fix(update,session): brain_update and session_log confine caller paths (#169)

Review round 1 on PR #170 found two more handlers with the #169 class of
bug (verified by execution):

- brain_update resolved its caller path with resolveWithin, a lexical
  containment check: any brain file could be superseded
  (classification.yaml, raw/, sessions/), and a final symlink was
  written through. UpdateNote now resolves like brain_edit
  (notes.Resolve, ScopeNotes: knowledge/ and wiki/ .md notes), and reads
  and rewrites through brainfs (ReadRegular, WriteRegular).
- session_log joined the caller's session_id onto the sessions dir and
  opened it O_CREATE|O_APPEND: an id with path segments created or
  appended a .jsonl file anywhere the pod could write. The id must now
  be a plain name (^[A-Za-z0-9_][A-Za-z0-9._-]{0,127}$, which every live
  session file matches), and the open adds O_NOFOLLOW|O_NONBLOCK. Read
  checks the id too.
- Tunnel tests: the .txt case now names an existing file (it failed on
  "missing" before), the symlink test adds an in-brain target, and the
  FIFO comment no longer claims the handle check is the only guard.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.context/PROJECT.md

@@ -64,7 +64,11 @@ the routing pod; brain tools moved to the brain MCP.
 
 The brain HTTP REST API (`/query`, `/write`, `/ingest`, `/ingest-raw`,
 `/ingest-path`, `/backfill-refs`, `/pass-rate`) remains available on port 3300
-for shell scripts and non-MCP clients.
+for shell scripts and non-MCP clients, **with the same bearer token as `/mcp`**
+(`BRAIN_MCP_TOKEN`; hyperguild#149). It is not served on the public host
+(infra#517): use the tailnet (`koala:8443`) or in-cluster
+`ingestion.supervisor.svc:3300`. `/ingest-path` and `brain_ingest` `path`
+accept only paths inside `brain/raw/`.
 
 `brain_answer(query)` performs BM25 retrieval + LLM synthesis (berget.ai
 gemma4:31b → iguana fallback). `brain_classify(text)` infers doc type, title,

.context/system-prompt.txt

@@ -78,6 +78,27 @@ These rules apply to every task across every project, regardless of harness.
    when a human reviewer outside the project is required. Document the reason in
    PROJECT.md.
 
+   **Exception — a GitOps repo where a branch cannot be reconciled.** In a repo whose
+   deployment watches one branch (`mathias/infra`: Flux watches `main`), a branch is
+   invisible to the thing that applies it. A `risk/medium` change to `alerts.yaml` or
+   `litellm-config.yaml` can be linted on a branch but never *exercised* there, so a
+   PR would buy a review of a state that was never deployed.
+
+   There, `risk/medium`+ work stays on `main` and instead requires a **recorded
+   adversarial review pass before the push** — `skills:pr-gatekeeper` or equivalent,
+   reviewing the staged diff. **The reviewer's verdict goes in the issue, not a PR
+   thread.** No verdict recorded means the lane was not used, and saying "the gate was
+   green" is not the same claim.
+
+   Be honest about what this is: a recorded *independent* pass, not four-eyes in the
+   sense `assessor-loop` §4.1 means for a regulated organisation, because the reviewer
+   is an agent. It is more than the repo had and less than the model it mirrors; do not
+   describe it as the stronger property. (infra#470, decided 2026-09-29.)
+
+   This lane depends on the `risk/` label being right. A label that triggers a heavier
+   lane is load-bearing, not cosmetic — if work that belongs in it is unlabelled, the
+   lane silently does not apply.
+
 6. **Close the loop — every substantive task ends with the same ritual.** Shipping
    the code is not the end of the task; capturing it is. Run this unprompted:
    - **Tag + bump SemVer** on the change (annotated tag; minor for a feature or
@@ -106,6 +127,43 @@ These rules apply to every task across every project, regardless of harness.
    revisit Y". Those are exactly the items that need a locator. If it is worth
    saying in a summary, it is worth writing where it can be found again without you.
 
+7. **Finish what's closable — only involve me for a genuine call.** If a
+   tracker issue, PR, or checklist item is demonstrably resolved — the fix
+   landed, the state changed, you verified it live — close/merge/check it off
+   in the same turn. Don't leave it open "for the record" or park it waiting
+   on me to confirm something that already happened; that's bookkeeping, not
+   a decision. Reserve asking me (`AskUserQuestion`, a `DECISION NEEDED`
+   comment, or otherwise pausing) for when it's genuinely mine to call:
+   irreversible or prod/host-impacting actions, a real judgment call with no
+   clearly-better option, ambiguous intent, or anything secret-writes/
+   destructive-git already gate. Before claiming something is closable,
+   verify it live (re-check the issue, re-run the command) rather than
+   trusting your own earlier summary (brain: `filed-issue-not-same-as-fixed`).
+
+8. **Control code needs an adversary, not a checklist.** Code whose job is to
+   refuse, deny, gate or contain is not adequately verified by a green gate.
+   Rule 5 makes CI the quality gate and that holds for ordinary work — but a
+   passing suite only asserts what its author already thought of, and for a
+   control the author is precisely the person whose imagination just failed.
+   Measured on `dispatch#75`: five review rounds, five real escapes verified by
+   execution, and **CI was green on every one of them** while `git rm
+   ././.dispatch-allow` deleted the file the control existed to protect. So
+   route this work through a review with authority to block, instructed to
+   verify by execution rather than by reading the implementation. Expect to be
+   blocked more than once; that is the control working, not the reviewer being
+   difficult. (brain: `a-green-gate-is-not-evidence-for-control-code`; the
+   practices live in the `pr-gatekeeper` agent.)
+
+9. **A test's name must not claim more than its assertions prove.** Name a test
+   after the mechanism it observes, not the goal it serves.
+   `DoesNotInheritEnv` is honest; `IsContained` is a claim the test cannot
+   support. This is not pedantry about naming — when name and assertion
+   diverge, the name wins in the reader's head and the gap becomes invisible,
+   which is what lets the defect survive review. Found three times in one PR,
+   twice in tests written to fix the previous instance of it; each passed while
+   the thing it was named for was exploitable. If you cannot name the mechanism,
+   you do not yet know what the test observes.
+
 ## CAD sprint patterns
 
 Two CAD sprint archetypes (defs: brain `wiki/homelab/decisions/continuous-agentic-development-cad-concept-2026-06-16`):
@@ -246,10 +304,16 @@ entries that age well are about *why*, *how to avoid*, and *what to do when*.
 |---------|-------|-------|
 | **Claude Code, Claude Desktop** | `brain_query` (BM25), `brain_answer` (LLM-synth + sources) MCP tools | `brain_write` MCP tool |
 | **Crush, Pi, Antigravity, other MCP-capable** | same MCP server: `ingestion-brain` (via the `mcp__*_brain__*` namespace once authenticated) | same |
-| **Anything HTTP-only (curl, scripts)** | `POST https://brain-mcp.d-ma.be/query` with `{"query":"..."}` (auth via `BRAIN_MCP_TOKEN`) | `POST .../write` with `{"content":"...","filename":"..."}` |
+| **Anything HTTP-only (curl, scripts)** | Tailnet only: `POST https://koala.tail30472e.ts.net:8443/query` with `{"query":"..."}`, sending `BRAIN_MCP_TOKEN` (not yet enforced on REST, hyperguild#149). The public `brain-mcp.d-ma.be` serves `/mcp` only (infra#517). | `POST .../write` with `{"content":"...","wing":"...","hall":"..."}` |
 | **Browser / human inspection** | `https://git.d-ma.be/mathias/hyperguild` → `knowledge/` and `wiki/` markdown files |
 
-- **Scoping**: defaults to `public` collection; client projects filter to `{client}` + `public`.
+- **Scoping — the brain holds no confidential client content.** Nothing on the read path
+  filters by client: every token holder can read every wing, and `wing` on `brain_query`
+  is an optional argument, not an access control. Client confidentiality is enforced only
+  at write time (`capture`'s I1 gate refuses internal/confidential). So never `brain_write`
+  client material; generalise it first or keep it in the client's own repo. (hyperguild#144,
+  decided 2026-10-01. This line previously claimed client projects were filtered; they
+  were not.)
 - **Routing**: brain_answer's LLM uses berget.ai as primary, iguana ollama as
   fallback. Both are configurable in the `supervisor/ingestion-deployment.yaml`
   on the koala k3s cluster; don't hardcode local-only model names into the
@@ -319,8 +383,20 @@ Workflow:
    and missing-untracked adapters). A drift fails the check with a
    message telling you to stage the regenerated files.
 
-Behavior rules in this file and per-project rules in `PROJECT.md` apply
+Behavior rules in this file and per-project rules in `PROJECT.md` apply on every
-unconditionally on every host, every harness.
+host and every harness.
+
+**Where a project rule contradicts a rule here, the project rule governs — and it
+must state its reason.** Both halves matter: the project file wins because it knows
+something this file cannot (infra's Flux constraint is real and not visible from
+here), and it must say why because a bare override is indistinguishable from drift.
+
+This replaces the previous wording, which said rules here and in `PROJECT.md` both
+apply *"unconditionally"*. That was not a tiebreak but a contradiction, and it went
+unnoticed until rule 5 and infra's "never create feature branches" had to be obeyed
+at the same time (infra#470). A standard can hold two individually sensible clauses
+that are jointly unsatisfiable, and survive for as long as everyone reads it
+charitably — the same failure the Inception Sprint Oath's G6 had.
 
 ## Engineering Skills
 
@@ -417,7 +493,11 @@ the routing pod; brain tools moved to the brain MCP.
 
 The brain HTTP REST API (`/query`, `/write`, `/ingest`, `/ingest-raw`,
 `/ingest-path`, `/backfill-refs`, `/pass-rate`) remains available on port 3300
-for shell scripts and non-MCP clients.
+for shell scripts and non-MCP clients, **with the same bearer token as `/mcp`**
+(`BRAIN_MCP_TOKEN`; hyperguild#149). It is not served on the public host
+(infra#517): use the tailnet (`koala:8443`) or in-cluster
+`ingestion.supervisor.svc:3300`. `/ingest-path` and `brain_ingest` `path`
+accept only paths inside `brain/raw/`.
 
 `brain_answer(query)` performs BM25 retrieval + LLM synthesis (berget.ai
 gemma4:31b → iguana fallback). `brain_classify(text)` infers doc type, title,

AGENTS.md

@@ -73,6 +73,27 @@ These rules apply to every task across every project, regardless of harness.
    when a human reviewer outside the project is required. Document the reason in
    PROJECT.md.
 
+   **Exception — a GitOps repo where a branch cannot be reconciled.** In a repo whose
+   deployment watches one branch (`mathias/infra`: Flux watches `main`), a branch is
+   invisible to the thing that applies it. A `risk/medium` change to `alerts.yaml` or
+   `litellm-config.yaml` can be linted on a branch but never *exercised* there, so a
+   PR would buy a review of a state that was never deployed.
+
+   There, `risk/medium`+ work stays on `main` and instead requires a **recorded
+   adversarial review pass before the push** — `skills:pr-gatekeeper` or equivalent,
+   reviewing the staged diff. **The reviewer's verdict goes in the issue, not a PR
+   thread.** No verdict recorded means the lane was not used, and saying "the gate was
+   green" is not the same claim.
+
+   Be honest about what this is: a recorded *independent* pass, not four-eyes in the
+   sense `assessor-loop` §4.1 means for a regulated organisation, because the reviewer
+   is an agent. It is more than the repo had and less than the model it mirrors; do not
+   describe it as the stronger property. (infra#470, decided 2026-09-29.)
+
+   This lane depends on the `risk/` label being right. A label that triggers a heavier
+   lane is load-bearing, not cosmetic — if work that belongs in it is unlabelled, the
+   lane silently does not apply.
+
 6. **Close the loop — every substantive task ends with the same ritual.** Shipping
    the code is not the end of the task; capturing it is. Run this unprompted:
    - **Tag + bump SemVer** on the change (annotated tag; minor for a feature or
@@ -101,6 +122,43 @@ These rules apply to every task across every project, regardless of harness.
    revisit Y". Those are exactly the items that need a locator. If it is worth
    saying in a summary, it is worth writing where it can be found again without you.
 
+7. **Finish what's closable — only involve me for a genuine call.** If a
+   tracker issue, PR, or checklist item is demonstrably resolved — the fix
+   landed, the state changed, you verified it live — close/merge/check it off
+   in the same turn. Don't leave it open "for the record" or park it waiting
+   on me to confirm something that already happened; that's bookkeeping, not
+   a decision. Reserve asking me (`AskUserQuestion`, a `DECISION NEEDED`
+   comment, or otherwise pausing) for when it's genuinely mine to call:
+   irreversible or prod/host-impacting actions, a real judgment call with no
+   clearly-better option, ambiguous intent, or anything secret-writes/
+   destructive-git already gate. Before claiming something is closable,
+   verify it live (re-check the issue, re-run the command) rather than
+   trusting your own earlier summary (brain: `filed-issue-not-same-as-fixed`).
+
+8. **Control code needs an adversary, not a checklist.** Code whose job is to
+   refuse, deny, gate or contain is not adequately verified by a green gate.
+   Rule 5 makes CI the quality gate and that holds for ordinary work — but a
+   passing suite only asserts what its author already thought of, and for a
+   control the author is precisely the person whose imagination just failed.
+   Measured on `dispatch#75`: five review rounds, five real escapes verified by
+   execution, and **CI was green on every one of them** while `git rm
+   ././.dispatch-allow` deleted the file the control existed to protect. So
+   route this work through a review with authority to block, instructed to
+   verify by execution rather than by reading the implementation. Expect to be
+   blocked more than once; that is the control working, not the reviewer being
+   difficult. (brain: `a-green-gate-is-not-evidence-for-control-code`; the
+   practices live in the `pr-gatekeeper` agent.)
+
+9. **A test's name must not claim more than its assertions prove.** Name a test
+   after the mechanism it observes, not the goal it serves.
+   `DoesNotInheritEnv` is honest; `IsContained` is a claim the test cannot
+   support. This is not pedantry about naming — when name and assertion
+   diverge, the name wins in the reader's head and the gap becomes invisible,
+   which is what lets the defect survive review. Found three times in one PR,
+   twice in tests written to fix the previous instance of it; each passed while
+   the thing it was named for was exploitable. If you cannot name the mechanism,
+   you do not yet know what the test observes.
+
 ## CAD sprint patterns
 
 Two CAD sprint archetypes (defs: brain `wiki/homelab/decisions/continuous-agentic-development-cad-concept-2026-06-16`):
@@ -241,10 +299,16 @@ entries that age well are about *why*, *how to avoid*, and *what to do when*.
 |---------|-------|-------|
 | **Claude Code, Claude Desktop** | `brain_query` (BM25), `brain_answer` (LLM-synth + sources) MCP tools | `brain_write` MCP tool |
 | **Crush, Pi, Antigravity, other MCP-capable** | same MCP server: `ingestion-brain` (via the `mcp__*_brain__*` namespace once authenticated) | same |
-| **Anything HTTP-only (curl, scripts)** | `POST https://brain-mcp.d-ma.be/query` with `{"query":"..."}` (auth via `BRAIN_MCP_TOKEN`) | `POST .../write` with `{"content":"...","filename":"..."}` |
+| **Anything HTTP-only (curl, scripts)** | Tailnet only: `POST https://koala.tail30472e.ts.net:8443/query` with `{"query":"..."}`, sending `BRAIN_MCP_TOKEN` (not yet enforced on REST, hyperguild#149). The public `brain-mcp.d-ma.be` serves `/mcp` only (infra#517). | `POST .../write` with `{"content":"...","wing":"...","hall":"..."}` |
 | **Browser / human inspection** | `https://git.d-ma.be/mathias/hyperguild` → `knowledge/` and `wiki/` markdown files |
 
-- **Scoping**: defaults to `public` collection; client projects filter to `{client}` + `public`.
+- **Scoping — the brain holds no confidential client content.** Nothing on the read path
+  filters by client: every token holder can read every wing, and `wing` on `brain_query`
+  is an optional argument, not an access control. Client confidentiality is enforced only
+  at write time (`capture`'s I1 gate refuses internal/confidential). So never `brain_write`
+  client material; generalise it first or keep it in the client's own repo. (hyperguild#144,
+  decided 2026-10-01. This line previously claimed client projects were filtered; they
+  were not.)
 - **Routing**: brain_answer's LLM uses berget.ai as primary, iguana ollama as
   fallback. Both are configurable in the `supervisor/ingestion-deployment.yaml`
   on the koala k3s cluster; don't hardcode local-only model names into the
@@ -314,8 +378,20 @@ Workflow:
    and missing-untracked adapters). A drift fails the check with a
    message telling you to stage the regenerated files.
 
-Behavior rules in this file and per-project rules in `PROJECT.md` apply
+Behavior rules in this file and per-project rules in `PROJECT.md` apply on every
-unconditionally on every host, every harness.
+host and every harness.
+
+**Where a project rule contradicts a rule here, the project rule governs — and it
+must state its reason.** Both halves matter: the project file wins because it knows
+something this file cannot (infra's Flux constraint is real and not visible from
+here), and it must say why because a bare override is indistinguishable from drift.
+
+This replaces the previous wording, which said rules here and in `PROJECT.md` both
+apply *"unconditionally"*. That was not a tiebreak but a contradiction, and it went
+unnoticed until rule 5 and infra's "never create feature branches" had to be obeyed
+at the same time (infra#470). A standard can hold two individually sensible clauses
+that are jointly unsatisfiable, and survive for as long as everyone reads it
+charitably — the same failure the Inception Sprint Oath's G6 had.
 
 ## Engineering Skills
 
@@ -412,7 +488,11 @@ the routing pod; brain tools moved to the brain MCP.
 
 The brain HTTP REST API (`/query`, `/write`, `/ingest`, `/ingest-raw`,
 `/ingest-path`, `/backfill-refs`, `/pass-rate`) remains available on port 3300
-for shell scripts and non-MCP clients.
+for shell scripts and non-MCP clients, **with the same bearer token as `/mcp`**
+(`BRAIN_MCP_TOKEN`; hyperguild#149). It is not served on the public host
+(infra#517): use the tailnet (`koala:8443`) or in-cluster
+`ingestion.supervisor.svc:3300`. `/ingest-path` and `brain_ingest` `path`
+accept only paths inside `brain/raw/`.
 
 `brain_answer(query)` performs BM25 retrieval + LLM synthesis (berget.ai
 gemma4:31b → iguana fallback). `brain_classify(text)` infers doc type, title,

CLAUDE.md

@@ -64,7 +64,11 @@ the routing pod; brain tools moved to the brain MCP.
 
 The brain HTTP REST API (`/query`, `/write`, `/ingest`, `/ingest-raw`,
 `/ingest-path`, `/backfill-refs`, `/pass-rate`) remains available on port 3300
-for shell scripts and non-MCP clients.
+for shell scripts and non-MCP clients, **with the same bearer token as `/mcp`**
+(`BRAIN_MCP_TOKEN`; hyperguild#149). It is not served on the public host
+(infra#517): use the tailnet (`koala:8443`) or in-cluster
+`ingestion.supervisor.svc:3300`. `/ingest-path` and `brain_ingest` `path`
+accept only paths inside `brain/raw/`.
 
 `brain_answer(query)` performs BM25 retrieval + LLM synthesis (berget.ai
 gemma4:31b → iguana fallback). `brain_classify(text)` infers doc type, title,

cmd/hyperguild/http.go

@@ -20,6 +20,7 @@ const defaultBrainURL = "http://koala:30330"
 // shell-friendly client; MCP framing is unnecessary.
 type brainClient struct {
 	baseURL string
+	token   string // BRAIN_MCP_TOKEN; the REST API requires it since hyperguild#149
 	http    *http.Client
 }
 
@@ -30,6 +31,7 @@ func newBrainClient() *brainClient {
 	}
 	return &brainClient{
 		baseURL: u,
+		token:   os.Getenv("BRAIN_MCP_TOKEN"),
 		http:    &http.Client{Timeout: 5 * time.Second},
 	}
 }
@@ -62,8 +64,7 @@ func (c *brainClient) Query(ctx context.Context, topic string, limit int) (*Quer
 		return nil, fmt.Errorf("build request: %w", err)
 	}
 	req.Header.Set("Content-Type", "application/json")
-
+	resp, err := c.do(req)
-	resp, err := c.http.Do(req)
 	if err != nil {
 		return nil, fmt.Errorf("brain POST /query: %w", err)
 	}
@@ -105,8 +106,7 @@ func (c *brainClient) Write(ctx context.Context, wing, hall, filename string, co
 		return nil, fmt.Errorf("build request: %w", err)
 	}
 	req.Header.Set("Content-Type", "application/json")
-
+	resp, err := c.do(req)
-	resp, err := c.http.Do(req)
 	if err != nil {
 		return nil, fmt.Errorf("brain POST /write: %w", err)
 	}
@@ -143,7 +143,7 @@ func (c *brainClient) PassRate(ctx context.Context, skill, window string) (*Pass
 	if err != nil {
 		return nil, fmt.Errorf("build request: %w", err)
 	}
-	resp, err := c.http.Do(req)
+	resp, err := c.do(req)
 	if err != nil {
 		return nil, fmt.Errorf("brain GET /pass-rate: %w", err)
 	}
@@ -158,3 +158,13 @@ func (c *brainClient) PassRate(ctx context.Context, skill, window string) (*Pass
 	}
 	return &out, nil
 }
+
+// do sends every brain request, adding the bearer token when one is
+// configured. All methods go through here so none can forget it (PassRate
+// did, PR #152 review).
+func (c *brainClient) do(req *http.Request) (*http.Response, error) {
+	if c.token != "" {
+		req.Header.Set("Authorization", "Bearer "+c.token)
+	}
+	return c.http.Do(req)
+}

cmd/hyperguild/http_auth_test.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// hyperguild#149: the ingestion REST API now requires a bearer token; the CLI
+// sends BRAIN_MCP_TOKEN, or it gets 401 on every brain call.
+func TestBrainClientSendsBrainMCPTokenOnQueryWriteAndPassRate(t *testing.T) {
+	var got []string
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		got = append(got, r.URL.Path+" "+r.Header.Get("Authorization"))
+		switch r.URL.Path {
+		case "/write":
+			_, _ = w.Write([]byte(`{"path":"wiki/x/facts/y.md"}`))
+			return
+		case "/pass-rate":
+			_, _ = w.Write([]byte(`{}`))
+			return
+		}
+		_, _ = w.Write([]byte(`{"results":[]}`))
+	}))
+	defer srv.Close()
+	t.Setenv("BRAIN_URL", srv.URL)
+	t.Setenv("BRAIN_MCP_TOKEN", "cli-test-token")
+
+	c := newBrainClient()
+	_, err := c.Query(context.Background(), "x", 1)
+	require.NoError(t, err)
+	_, err = c.Write(context.Background(), "x", "facts", "y", strings.NewReader("# y"))
+	require.NoError(t, err)
+	// PR #152 review: PassRate sent no token and would 401 in production.
+	_, _ = c.PassRate(context.Background(), "tdd", "7d")
+	assert.Equal(t, []string{"/query Bearer cli-test-token", "/write Bearer cli-test-token",
+		"/pass-rate Bearer cli-test-token"}, got)
+}
+
+func TestBrainClientSendsNoAuthorizationWhenTokenUnset(t *testing.T) {
+	var auth string
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		auth = r.Header.Get("Authorization")
+		_, _ = w.Write([]byte(`{"results":[]}`))
+	}))
+	defer srv.Close()
+	t.Setenv("BRAIN_URL", srv.URL)
+	t.Setenv("BRAIN_MCP_TOKEN", "")
+	_, err := newBrainClient().Query(context.Background(), "x", 1)
+	require.NoError(t, err)
+	assert.Empty(t, auth)
+}

docs/runbooks/exercising-pass-rate-traffic.md

@@ -24,7 +24,7 @@ Only a `tools/call` to the routing pod records a pass/fail.
 |---------|-----|------|
 | Routing MCP (local, Tailscale) | `http://koala:30310/mcp` | Bearer `ROUTING_MCP_TOKEN` |
 | Routing MCP (remote) | `https://routing-mcp.d-ma.be/mcp` | OAuth via `auth.d-ma.be` (audience `claude-ai`) |
-| Pass-rate readout | `http://koala:30330/pass-rate?skill=<name>` | none (read-only) |
+| Pass-rate readout | `http://koala:30330/pass-rate?skill=<name>` | Bearer `BRAIN_MCP_TOKEN` (since hyperguild#149) |
 
 Tools advertised: **`review`**, **`debug`** (the two the #35 gate measures),
 plus `session_log`, `retrospective`, `trainer`.

ingestion/cmd/server/main.go

@@ -33,6 +33,7 @@ import (
 	"github.com/mathiasbq/hyperguild/ingestion/internal/reranker"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/search"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/startupretry"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/symlinkguard"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/vectorstore"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/watcher"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/webhook"
@@ -147,6 +148,38 @@ func envInt(key string, fallback int) int {
 // buildNotifier returns the ntfy notifier, or a nil interface when
 // BRAIN_NTFY_URL is unset. A nil *interface* (not a typed-nil) is required so
 // DegradingSink/Reconcile and the governance observer skip it cleanly.
+// alertingWarnings names every alert that will not fire under the current
+// configuration (#107).
+//
+// buildNotifier returns a nil interface when BRAIN_NTFY_URL is unset, and every
+// consumer skips a nil notifier silently — right for an unconfigured homelab,
+// wrong for an alert whose entire value is that someone finds out. The cost of
+// the silence is that "configured and working" and "never configured" are
+// byte-identical in behaviour: no error, no warning, only a message that never
+// arrives, which nobody notices because nobody is waiting for an alert they
+// have never seen. Two alerts were dark in production for exactly that reason
+// (#100), found by firing a real event rather than by reading anything.
+//
+// WARN rather than fatal, deliberately. The brain sibling rule
+// (`empty-credential-must-refuse-to-start-not-switch-modes`) says an empty
+// credential must be a startup error, never a silent mode switch — but that is
+// about a control being removed. Here observability is degraded, not a gate
+// bypassed, and refusing to boot would break the unconfigured-homelab case the
+// nil notifier exists to support. What the rule does demand, and what this
+// provides, is that the mode switch stops being silent.
+//
+// Pure and env-injected so the message is testable without a running server:
+// the reason this gap survived is that nothing about it was observable.
+func alertingWarnings(getenv func(string) string) []string {
+	var out []string
+	if getenv("BRAIN_NTFY_URL") == "" {
+		out = append(out, "alerting DISABLED: BRAIN_NTFY_URL unset — "+
+			"brain_edit_root governance rewrites, capture audit degradation and the "+
+			"brain symlink tripwire (hyperguild#157) will not notify")
+	}
+	return out
+}
+
 func buildNotifier() audit.Notifier {
 	if n := audit.NewNtfyNotifier(os.Getenv("BRAIN_NTFY_URL"), os.Getenv("BRAIN_NTFY_TOKEN")); n != nil {
 		return n
@@ -203,7 +236,15 @@ func systemHostname() string {
 func main() {
 	logger := slog.New(slog.NewJSONHandler(os.Stdout, nil))
 
+	for _, w := range alertingWarnings(os.Getenv) {
+		logger.Warn(w)
+	}
+
 	brainDir := envOr("INGEST_BRAIN_DIR", "../brain")
+	if err := startupSymlinkCheck(brainDir); err != nil {
+		logger.Error("brain symlink tripwire", "err", err)
+		os.Exit(1)
+	}
 	port := envOr("INGEST_PORT", "3300")
 
 	llmURL := envOr("INGEST_LLM_URL", "http://iguana:4000/v1")
@@ -325,6 +366,8 @@ func main() {
 	}
 
 	ctx := context.Background()
+	// hyperguild#157: report a symlink that appears in the brain while running.
+	go symlinkguard.Watch(ctx, brainDir, symlinkScanInterval(os.Getenv), buildNotifier())
 
 	// Built before the watcher, the graph backfill and session ingestion, and
 	// retried rather than fatal (#83). Two separate reasons:
@@ -468,20 +511,10 @@ func main() {
 		logger.Info("embed sync started", "interval_s", embedSyncInterval)
 	}
 
-	mux := http.NewServeMux()
+	// Public routes only; buildMux mounts the authenticated REST API (#149).
-	mux.HandleFunc("POST /query", h.Query)
+	public := map[string]http.Handler{}
-	mux.HandleFunc("POST /write", h.Write)
-	mux.HandleFunc("POST /index", h.Index)
-	mux.HandleFunc("POST /ingest", h.Ingest)
-	mux.HandleFunc("POST /ingest-path", h.IngestPath)
-	mux.HandleFunc("POST /ingest-raw", h.IngestRaw)
-	mux.HandleFunc("POST /backfill-refs", h.BackfillRefs)
-	mux.HandleFunc("GET /pending", h.Pending)
-	mux.HandleFunc("POST /promote", h.Promote)
-	mux.HandleFunc("POST /backfill-embeddings", h.BackfillEmbeddings)
-	mux.HandleFunc("GET /pass-rate", h.PassRate)
 	if webhookHandler != nil {
-		mux.Handle("POST /webhooks/brain-sync", webhookHandler)
+		public["POST /webhooks/brain-sync"] = webhookHandler
 	}
 	// Resource-metadata URL is only emitted on 401 when Dex OAuth is
 	// configured. Static-Bearer-only deployments leave this empty so
@@ -489,14 +522,14 @@ func main() {
 	var resourceMetadataURL string
 	if dexURL := os.Getenv("DEX_ISSUER_URL"); dexURL != "" {
 		resourceURL := os.Getenv("MCP_RESOURCE_URL")
-		mux.HandleFunc("GET /.well-known/oauth-protected-resource",
+		public["GET /.well-known/oauth-protected-resource"] = http.HandlerFunc(
 			chassisauth.ProtectedResourceHandler(resourceURL, dexURL))
 		if resourceURL != "" {
 			resourceMetadataURL = strings.TrimRight(resourceURL, "/") + "/.well-known/oauth-protected-resource"
 		}
 	}
 
-	mux.Handle("/mcp", chassisauth.BearerMiddleware(mcpToken, jwtValidator, "brain", resourceMetadataURL, mcpSrv))
+	public["/mcp"] = chassisauth.BearerMiddleware(mcpToken, jwtValidator, "brain", resourceMetadataURL, mcpSrv)
 
 	// POST /capture (#53/#54): the uniform capture REST door. Needs a ticket
 	// tracker to file action items, so it only mounts when Gitea is
@@ -518,7 +551,7 @@ func main() {
 		sovereign := splitList(os.Getenv("BRAIN_CAPTURE_SOVEREIGN_PRINCIPALS"))
 		resolver := capturehttp.NewOriginResolver(sovereign)
 		captureH := capturehttp.New(captureSvc, jwtValidator, mcpToken, "local-cli", resolver)
-		mux.Handle("POST /capture", captureH)
+		public["POST /capture"] = captureH
 		// Same use-case behind the MCP `capture` tool (#55 relay) so MCP-native
 		// harnesses (claude.ai, Crush, Pi, LLM Council) reach capture through
 		// the existing /mcp OAuth connector. mcpSrv is already wrapped above;
@@ -548,9 +581,9 @@ func main() {
 			logger.Error("OAUTH_CLIENT_ID/SECRET set but MCP_RESOURCE_URL is empty; cannot derive issuer")
 			os.Exit(1)
 		}
-		mux.HandleFunc("GET /.well-known/oauth-authorization-server",
+		public["GET /.well-known/oauth-authorization-server"] = http.HandlerFunc(
 			oauth.MetadataHandler(issuer))
-		mux.HandleFunc("POST /oauth/token", oauth.TokenHandler(oauth.TokenConfig{
+		public["POST /oauth/token"] = http.HandlerFunc(oauth.TokenHandler(oauth.TokenConfig{
 			ClientID:     oauthID,
 			ClientSecret: oauthSecret,
 			AccessToken:  mcpToken,
@@ -569,7 +602,17 @@ func main() {
 	// real request latency. /metrics itself is excluded from its own
 	// observation by registering it on the outer mux (post-wrap).
 	reg := metrics.New()
-	mux.HandleFunc("GET /metrics", reg.Handler())
+	public["GET /metrics"] = http.HandlerFunc(reg.Handler())
+
+	// The whole router, built in one place so the test of buildMux is a test
+	// of production wiring (PR #152 review). The REST API's credential is the
+	// same as /mcp's.
+	mux, err := buildMux(restAuth{token: mcpToken, validator: jwtValidator, realm: "brain",
+		resourceMetadataURL: resourceMetadataURL}, h, public)
+	if err != nil {
+		logger.Error("build router", "err", err)
+		os.Exit(1)
+	}
 	logger.Info("metrics endpoint registered", "path", "/metrics")
 
 	addr := ":" + port

ingestion/cmd/server/main_test.go

@@ -6,6 +6,7 @@ import (
 	"log/slog"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -36,3 +37,42 @@ func TestClaudeSink_IngestWritesToNonIndexedArchiveNotWiki(t *testing.T) {
 	_, err = os.Stat(filepath.Join(dir, "wiki", "claude-sessions"))
 	assert.True(t, os.IsNotExist(err), "raw transcripts must never land under wiki/ (ai-sessions#10 — BM25 pollution)")
 }
+
+// --- #107: an unconfigured alert must announce itself ----------------------
+
+func TestAlertingWarnings(t *testing.T) {
+	tests := []struct {
+		name string
+		env  map[string]string
+		want []string // substrings that must appear across the warnings
+		none bool     // true = expect no warnings at all
+	}{
+		{
+			// The failure this exists to prevent: two alerts dark in
+			// production, discovered only by firing a real event and watching
+			// nothing arrive (#100).
+			name: "notifier unconfigured names what will not fire",
+			env:  map[string]string{},
+			want: []string{"BRAIN_NTFY_URL", "brain_edit_root", "audit"},
+		},
+		{
+			name: "configured notifier is silent",
+			env:  map[string]string{"BRAIN_NTFY_URL": "http://ntfy/brain-alerts"},
+			none: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := alertingWarnings(func(k string) string { return tt.env[k] })
+			if tt.none {
+				assert.Empty(t, got)
+				return
+			}
+			joined := strings.Join(got, " ")
+			for _, w := range tt.want {
+				assert.Contains(t, joined, w)
+			}
+		})
+	}
+}

ingestion/cmd/server/routes.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+
+	chassisauth "git.d-ma.be/mathias/mcp-chassis/auth"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
+)
+
+// publicRoutes is the complete set of patterns allowed on the outer mux,
+// outside the REST API's auth (hyperguild#149). Each authenticates itself or is
+// meant to be open: /mcp (bearer/JWT), /capture (bearer/JWT), the webhook
+// (HMAC), /oauth/token (client secret), OAuth metadata and /metrics (open).
+// A REST pattern added here would beat the authenticated catch-all by
+// specificity and ship open, which is why buildMux refuses anything else.
+var publicRoutes = map[string]bool{
+	"/mcp":                      true,
+	"POST /capture":             true,
+	"POST /webhooks/brain-sync": true,
+	"GET /.well-known/oauth-protected-resource":   true,
+	"GET /.well-known/oauth-authorization-server": true,
+	"POST /oauth/token":                           true,
+	"GET /metrics":                                true,
+}
+
+// restAuth is the credential the REST API checks: the same as /mcp's.
+type restAuth struct {
+	token               string
+	validator           *chassisauth.JWTValidator
+	realm               string
+	resourceMetadataURL string
+}
+
+// buildMux is the server's whole router. The REST API is mounted at "/"
+// behind bearer auth that buildMux constructs itself, so a caller cannot pass
+// a no-op; public handlers are registered as given, and only for patterns on
+// the publicRoutes allowlist. It returns an http.Handler, not the
+// *ServeMux, so nothing can register a route on the result afterwards and
+// bypass the allowlist.
+func buildMux(auth restAuth, h *api.Handler, public map[string]http.Handler) (http.Handler, error) {
+	if auth.token == "" {
+		return nil, errors.New("buildMux: REST auth needs a token")
+	}
+	mux := http.NewServeMux()
+	for pattern, handler := range public {
+		if !publicRoutes[pattern] {
+			return nil, fmt.Errorf("buildMux: %q is not an allowed public route", pattern)
+		}
+		mux.Handle(pattern, handler)
+	}
+	mountREST(mux, h, func(next http.Handler) http.Handler {
+		return chassisauth.BearerMiddleware(auth.token, auth.validator, auth.realm, auth.resourceMetadataURL, next)
+	})
+	return mux, nil
+}
+
+// mountREST registers the REST API on its own mux and mounts it at "/" behind
+// auth: anything not registered as public lands here and is authenticated,
+// including routes added later.
+func mountREST(mux *http.ServeMux, h *api.Handler, auth func(http.Handler) http.Handler) {
+	rest := http.NewServeMux()
+	rest.HandleFunc("POST /query", h.Query)
+	rest.HandleFunc("POST /write", h.Write)
+	rest.HandleFunc("POST /index", h.Index)
+	rest.HandleFunc("POST /ingest", h.Ingest)
+	rest.HandleFunc("POST /ingest-path", h.IngestPath)
+	rest.HandleFunc("POST /ingest-raw", h.IngestRaw)
+	rest.HandleFunc("POST /backfill-refs", h.BackfillRefs)
+	rest.HandleFunc("GET /pending", h.Pending)
+	rest.HandleFunc("POST /promote", h.Promote)
+	rest.HandleFunc("POST /backfill-embeddings", h.BackfillEmbeddings)
+	rest.HandleFunc("GET /pass-rate", h.PassRate)
+	mux.Handle("/", auth(rest))
+}

ingestion/cmd/server/routes_test.go

@@ -0,0 +1,106 @@
+package main
+
+import (
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/pipeline"
+)
+
+const routesTok = "routes-test-token"
+
+func okHandler(body string) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) { _, _ = w.Write([]byte(body)) })
+}
+
+// testMux builds the router exactly as main does: buildMux with the full
+// public set main registers (stub handlers) and real bearer config.
+// hyperguild#149: the REST API is authenticated as a whole; the PR #152
+// review showed a test of a COPY of the router let main.go regress unseen.
+func testMux(t *testing.T) http.Handler {
+	t.Helper()
+	h := api.NewHandler(t.TempDir(), slog.New(slog.NewTextHandler(os.Stderr, nil)), pipeline.Config{})
+	public := map[string]http.Handler{}
+	for p := range publicRoutes {
+		public[p] = okHandler("public " + p)
+	}
+	mux, err := buildMux(restAuth{token: routesTok, realm: "brain"}, h, public)
+	require.NoError(t, err)
+	return mux
+}
+
+func do(t *testing.T, h http.Handler, method, path, authz string) (int, string) {
+	t.Helper()
+	req := httptest.NewRequest(method, path, strings.NewReader(`{"query":"x"}`))
+	if authz != "" {
+		req.Header.Set("Authorization", authz)
+	}
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+	return rec.Code, rec.Body.String()
+}
+
+func TestBuildMuxRefusesRESTRoutesWithoutAValidToken(t *testing.T) {
+	r := testMux(t)
+	for _, rt := range []struct{ method, path string }{
+		{"POST", "/query"}, {"POST", "/write"}, {"POST", "/index"}, {"POST", "/ingest"},
+		{"POST", "/ingest-path"}, {"POST", "/ingest-raw"}, {"POST", "/backfill-refs"},
+		{"GET", "/pending"}, {"POST", "/promote"}, {"POST", "/backfill-embeddings"}, {"GET", "/pass-rate"},
+	} {
+		code, _ := do(t, r, rt.method, rt.path, "")
+		assert.Equal(t, http.StatusUnauthorized, code, "%s %s without a token", rt.method, rt.path)
+		code, _ = do(t, r, rt.method, rt.path, "Bearer wrong")
+		assert.Equal(t, http.StatusUnauthorized, code, "%s %s with a wrong token", rt.method, rt.path)
+	}
+}
+
+func TestBuildMuxServesRESTRoutesToAValidToken(t *testing.T) {
+	r := testMux(t)
+	code, _ := do(t, r, "GET", "/pending", "Bearer "+routesTok)
+	assert.Equal(t, http.StatusOK, code)
+}
+
+func TestBuildMuxAuthenticatesAnUnregisteredPath(t *testing.T) {
+	code, _ := do(t, testMux(t), "POST", "/some-future-route", "")
+	assert.Equal(t, http.StatusUnauthorized, code)
+}
+
+// buildMux registers public handlers as given, without adding auth: each
+// public route owns its own (bearer on /mcp, HMAC on the webhook, client
+// secret on /oauth/token) or is meant to be open (/metrics, OAuth metadata).
+func TestBuildMuxDoesNotWrapPublicRoutes(t *testing.T) {
+	r := testMux(t)
+	for p := range publicRoutes {
+		method, path, ok := strings.Cut(p, " ")
+		if !ok {
+			method, path = "GET", p
+		}
+		code, body := do(t, r, method, path, "")
+		assert.Equal(t, http.StatusOK, code, p)
+		assert.Equal(t, "public "+p, body, p)
+	}
+}
+
+// The allowlist is the control: a REST pattern registered as public would win
+// over the authenticated catch-all (more specific pattern), so it is refused.
+func TestBuildMuxRefusesAPublicPatternOffTheAllowlist(t *testing.T) {
+	h := api.NewHandler(t.TempDir(), slog.New(slog.NewTextHandler(os.Stderr, nil)), pipeline.Config{})
+	for _, p := range []string{"POST /query", "GET /pending", "/", "POST /metrics"} {
+		_, err := buildMux(restAuth{token: routesTok, realm: "brain"}, h, map[string]http.Handler{p: okHandler("x")})
+		assert.Error(t, err, "public pattern %q must be refused", p)
+	}
+}
+
+func TestBuildMuxRefusesAnEmptyToken(t *testing.T) {
+	h := api.NewHandler(t.TempDir(), slog.New(slog.NewTextHandler(os.Stderr, nil)), pipeline.Config{})
+	_, err := buildMux(restAuth{token: "", realm: "brain"}, h, nil)
+	assert.Error(t, err)
+}

ingestion/cmd/server/symlink_check.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/symlinkguard"
+)
+
+// startupSymlinkCheck is the hyperguild#157 tripwire at boot: a symlink in the
+// brain dir would let brain readers serve a file from outside the brain, so
+// the server does not start until it is removed. A directory the scan cannot
+// read could hide one, so it refuses on that too. A missing brain dir (first
+// boot) is the only case it lets pass.
+func startupSymlinkCheck(brainDir string) error {
+	r, err := symlinkguard.Scan(brainDir)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil
+		}
+		return fmt.Errorf("refusing to start: cannot scan the brain dir %s (hyperguild#157): %w", brainDir, err)
+	}
+	if !r.Clean() {
+		return fmt.Errorf("refusing to start: brain dir %s has %s (hyperguild#157); fix them first", brainDir, r)
+	}
+	return nil
+}
+
+// symlinkScanInterval reads BRAIN_SYMLINK_SCAN_INTERVAL (seconds), falling
+// back to the default on an unset, non-numeric or non-positive value.
+func symlinkScanInterval(getenv func(string) string) time.Duration {
+	if s, err := strconv.Atoi(getenv("BRAIN_SYMLINK_SCAN_INTERVAL")); err == nil && s > 0 {
+		return time.Duration(s) * time.Second
+	}
+	return symlinkguard.DefaultInterval
+}

ingestion/cmd/server/symlink_check_test.go

@@ -0,0 +1,65 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// hyperguild#157: the server refuses to start while a symlink exists in the
+// brain dir, or while any part of it cannot be scanned (which could hide
+// one); a missing brain dir is the only thing it lets pass.
+func TestStartupSymlinkCheckRefusesABrainWithASymlink(t *testing.T) {
+	brain := t.TempDir()
+	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "planted")))
+	err := startupSymlinkCheck(brain)
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "planted")
+}
+
+func TestStartupSymlinkCheckRefusesABrainWithAnUnreadableDir(t *testing.T) {
+	if os.Geteuid() == 0 {
+		t.Skip("root reads mode-000 directories")
+	}
+	brain := t.TempDir()
+	locked := filepath.Join(brain, "aaa")
+	require.NoError(t, os.MkdirAll(locked, 0o755))
+	require.NoError(t, os.Chmod(locked, 0o000))
+	t.Cleanup(func() { _ = os.Chmod(locked, 0o755) })
+	err := startupSymlinkCheck(brain)
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "aaa")
+}
+
+func TestStartupSymlinkCheckPassesACleanOrMissingBrain(t *testing.T) {
+	brain := t.TempDir()
+	require.NoError(t, os.WriteFile(filepath.Join(brain, "n.md"), []byte("x"), 0o644))
+	assert.NoError(t, startupSymlinkCheck(brain))
+	assert.NoError(t, startupSymlinkCheck(filepath.Join(brain, "missing")))
+}
+
+func TestSymlinkScanIntervalFallsBackOnNonPositive(t *testing.T) {
+	for _, v := range []string{"0", "-5", "", "junk"} {
+		got := symlinkScanInterval(func(string) string { return v })
+		assert.Positive(t, got, "env %q", v)
+	}
+}
+
+func TestAlertingWarningsNamesTheSymlinkTripwire(t *testing.T) {
+	w := strings.Join(alertingWarnings(func(string) string { return "" }), " ")
+	assert.Contains(t, w, "symlink tripwire")
+}
+
+func TestStartupSymlinkCheckRefusesAnUnlistableBrainRoot(t *testing.T) {
+	if os.Geteuid() == 0 {
+		t.Skip("root lists mode-0100 directories")
+	}
+	brain := t.TempDir()
+	require.NoError(t, os.Chmod(brain, 0o100))
+	t.Cleanup(func() { _ = os.Chmod(brain, 0o755) })
+	assert.Error(t, startupSymlinkCheck(brain))
+}

ingestion/internal/api/frontmatter.go

@@ -1,6 +1,12 @@
 package api
 
-import "strings"
+import (
+	"strings"
+
+	// Aliased: this package's own frontmatter type (below) would collide
+	// with the imported package's name otherwise.
+	sharedfm "github.com/mathiasbq/hyperguild/ingestion/internal/frontmatter"
+)
 
 // frontmatter is an ordered, line-preserving view of a note's YAML
 // frontmatter block. It deliberately avoids a full YAML round-trip: the
@@ -25,19 +31,26 @@ type fmLine struct {
 // frontmatter block is recognised only when the file opens with a `---`
 // fence and a closing `---` fence follows. Otherwise the whole input is
 // the body and the returned frontmatter is empty.
+//
+// Fence detection itself is frontmatter.Split (hyperguild#138) — this
+// package's own contribution is purely the ordered, line-preserving fmLine
+// shape below, which a shared parser has no business owning since it's
+// specific to how brain_update does a surgical, byte-round-trip edit.
 func parseFrontmatter(src string) (frontmatter, string) {
 	var fm frontmatter
-	if !strings.HasPrefix(src, "---\n") {
+	blockBytes, restBytes, ok := sharedfm.Split([]byte(src))
+	if !ok {
 		return fm, src
 	}
-	rest := src[len("---\n"):]
+	// sharedfm.Split's block/rest boundary sits one byte earlier than this
-	end := strings.Index(rest, "\n---\n")
+	// package's always has: block keeps the "\n" immediately before the
-	if end < 0 {
+	// closing fence, and rest keeps the "\n" immediately after it (both by
-		// Opening fence with no closing fence — treat as bodyless content.
+	// design, for Fix's own reconstruction). This package's block/body
-		return fm, src
+	// never included either — TrimSuffix/TrimPrefix restore that exact
-	}
+	// boundary. Split guarantees ok=true only when "\n---\n" matched, so
-	block := rest[:end]
+	// both trims are always exactly one byte, never ambiguous.
-	body := rest[end+len("\n---\n"):]
+	block := strings.TrimSuffix(string(blockBytes), "\n")
+	body := strings.TrimPrefix(string(restBytes), "\n")
 
 	for _, line := range strings.Split(block, "\n") {
 		// An indented line is a continuation (a YAML block-list item, a

ingestion/internal/api/handler.go

@@ -13,7 +13,6 @@ import (
 
 	"github.com/mathiasbq/hyperguild/ingestion/internal/brain"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/claim"
-	"github.com/mathiasbq/hyperguild/ingestion/internal/extract"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/pipeline"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/search"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/vectorstore"
@@ -118,6 +117,11 @@ type WriteNoteOptions struct {
 	Wing       string
 	Hall       string
 	SourceType string // "internal" marks a first-party observation (e.g. claudewatcher) that needs no external citation
+	// Origin/WrittenBy are server-owned provenance (hyperguild#145): any
+	// origin/written_by in Content's own frontmatter is discarded, so a
+	// caller cannot claim a more trusted origin than it authenticated as.
+	Origin    string
+	WrittenBy string
 }
 
 // WriteNote writes a markdown note into the brain. Returns the path
@@ -169,9 +173,6 @@ func writeHallNote(brainDir string, opts WriteNoteOptions) (string, error) {
 		return "", fmt.Errorf("claim envelope: %w", err)
 	}
 
-	if err := os.MkdirAll(filepath.Dir(dest), 0o755); err != nil {
-		return "", fmt.Errorf("create hall dir: %w", err)
-	}
 	emitted := make(map[string]bool, 6)
 
 	var fm strings.Builder
@@ -219,7 +220,17 @@ func writeHallNote(brainDir string, opts WriteNoteOptions) (string, error) {
 	}
 	fm.WriteString("---\n")
 
-	if err := os.WriteFile(dest, []byte(fm.String()+body), 0o644); err != nil {
+	final, err := StampProvenance(fm.String()+body, opts.Origin, opts.WrittenBy)
+	if err != nil {
+		return "", err
+	}
+	// The directory is created only once the note is known to be writable:
+	// a refused write leaves nothing behind, not even an empty hall dir
+	// (brain#21; provenance refusal joins the envelope refusal here).
+	if err := os.MkdirAll(filepath.Dir(dest), 0o755); err != nil {
+		return "", fmt.Errorf("create hall dir: %w", err)
+	}
+	if err := os.WriteFile(dest, []byte(final), 0o644); err != nil {
 		return "", fmt.Errorf("write: %w", err)
 	}
 	rel, _ := filepath.Rel(brainDir, dest)
@@ -295,7 +306,16 @@ func (h *Handler) Write(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "invalid JSON")
 		return
 	}
-	relPath, err := WriteNote(h.brainDir, WriteNoteOptions(req))
+	// Field by field, not a struct conversion: provenance is server-owned and
+	// this door carries no principal, so it stamps origin: unknown
+	// (hyperguild#145). A JSON body must never be able to set it.
+	relPath, err := WriteNote(h.brainDir, WriteNoteOptions{
+		Content:    req.Content,
+		Filename:   req.Filename,
+		Wing:       req.Wing,
+		Hall:       req.Hall,
+		SourceType: req.SourceType,
+	})
 	if err != nil {
 		h.logger.Error("write failed", "err", err)
 		writeError(w, http.StatusBadRequest, err.Error())
@@ -426,6 +446,12 @@ func (h *Handler) IngestPath(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "path is required")
 		return
 	}
+	resolved, err := ResolveIngestPath(h.brainDir, req.Path)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+	req.Path = resolved
 
 	info, err := os.Stat(req.Path)
 	if err != nil {
@@ -448,7 +474,13 @@ func (h *Handler) IngestPath(w http.ResponseWriter, r *http.Request) {
 			if !isSupportedExtension(ext) {
 				return nil
 			}
-			content, readErr := extract.Text(path)
+			// Each walked file is re-resolved: a symlinked file inside raw/
+			// would otherwise lead extract.Text out of the inbox (#149).
+			if _, rerr := ResolveIngestPath(h.brainDir, path); rerr != nil {
+				allWarnings = append(allWarnings, fmt.Sprintf("skipped %s: %v", path, rerr))
+				return nil
+			}
+			content, readErr := ReadIngestFile(h.brainDir, path)
 			if readErr != nil {
 				allWarnings = append(allWarnings, fmt.Sprintf("extract %s: %v", path, readErr))
 				return nil
@@ -477,7 +509,7 @@ func (h *Handler) IngestPath(w http.ResponseWriter, r *http.Request) {
 			writeError(w, http.StatusBadRequest, fmt.Sprintf("unsupported file extension: %s", ext))
 			return
 		}
-		content, readErr := extract.Text(req.Path)
+		content, readErr := ReadIngestFile(h.brainDir, req.Path)
 		if readErr != nil {
 			writeError(w, http.StatusInternalServerError, fmt.Sprintf("extract text: %v", readErr))
 			return
@@ -529,7 +561,8 @@ func (h *Handler) IngestRaw(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	result, err := pipeline.RunRaw(h.brainDir, req.Source, req.Pages, req.DryRun)
+	// No principal on this door: pages are stamped origin: unknown (#145).
+	result, err := pipeline.RunRaw(r.Context(), h.brainDir, req.Source, req.Pages, req.DryRun)
 	if err != nil {
 		h.logger.Error("ingest-raw failed", "source", req.Source, "err", err)
 		writeError(w, http.StatusInternalServerError, "ingest error")
@@ -585,7 +618,11 @@ func (h *Handler) Promote(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "invalid JSON")
 		return
 	}
-	rel, err := PromoteNote(h.brainDir, PromoteOptions(req))
+	// Field by field: this door carries no principal, so the promoted note is
+	// stamped origin: unknown and the body cannot set provenance (#145).
+	rel, err := PromoteNote(h.brainDir, PromoteOptions{
+		Filename: req.Filename, Wing: req.Wing, Hall: req.Hall, Slug: req.Slug,
+	})
 	if err != nil {
 		writeError(w, http.StatusBadRequest, err.Error())
 		return

ingestion/internal/api/handler_test.go

@@ -361,10 +361,11 @@ func TestIngestPath_MissingPath(t *testing.T) {
 }
 
 func TestIngestPath_File(t *testing.T) {
-	_, h := setup(t)
+	brainDir, h := setup(t)
 
 	// Create a temp file with content
-	dir := t.TempDir()
+	dir := filepath.Join(brainDir, "raw", "fixture") // ingest paths must live in brain/raw/ (#149)
+	require.NoError(t, os.MkdirAll(dir, 0o755))
 	f := filepath.Join(dir, "doc.md")
 	require.NoError(t, os.WriteFile(f, []byte("# Hello\nThis is markdown content."), 0o644))
 
@@ -468,10 +469,11 @@ func TestIngestRaw_DryRun(t *testing.T) {
 }
 
 func TestIngestPath_Directory(t *testing.T) {
-	_, h := setup(t)
+	brainDir, h := setup(t)
 
 	// Create a temp dir with one .md file
-	dir := t.TempDir()
+	dir := filepath.Join(brainDir, "raw", "fixture") // ingest paths must live in brain/raw/ (#149)
+	require.NoError(t, os.MkdirAll(dir, 0o755))
 	require.NoError(t, os.WriteFile(filepath.Join(dir, "notes.md"), []byte("# Notes\nSome notes."), 0o644))
 
 	body, _ := json.Marshal(map[string]any{

ingestion/internal/api/ingestpath_docmark_test.go

@@ -40,9 +40,10 @@ func TestIngestPath_DocxSupportedWhenDocmarkConfigured(t *testing.T) {
 	t.Setenv("DOCMARK_URL", srv.URL+"/mcp")
 	t.Setenv("DOCMARK_BEARER_TOKEN", "tok")
 
-	_, h := setup(t)
+	brainDir, h := setup(t)
 
-	dir := t.TempDir()
+	dir := filepath.Join(brainDir, "raw", "fixture") // ingest paths must live in brain/raw/ (#149)
+	require.NoError(t, os.MkdirAll(dir, 0o755))
 	f := filepath.Join(dir, "doc.docx")
 	require.NoError(t, os.WriteFile(f, []byte("fake docx"), 0o644))
 

ingestion/internal/api/ingestpath_root.go

@@ -0,0 +1,67 @@
+package api
+
+import (
+	"errors"
+	"os"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/extract"
+	"path/filepath"
+	"strings"
+)
+
+// ErrOutsideIngestRoot is the one refusal for every bad ingest path. It never
+// carries the underlying error: "no such file" versus "permission denied"
+// would let a caller probe which server files exist (PR #152 review).
+var ErrOutsideIngestRoot = errors.New("ingest path must be an existing file or directory inside brain/raw/")
+
+// ResolveIngestPath confines a caller-supplied ingest path to brain/raw/, the
+// inbox the watcher already owns (hyperguild#149). Relative paths resolve
+// against that root; symlinks are evaluated before the containment check, so
+// a link inside raw/ that points elsewhere is refused. The path must exist.
+func ResolveIngestPath(brainDir, p string) (string, error) {
+	if strings.TrimSpace(p) == "" {
+		return "", ErrOutsideIngestRoot
+	}
+	// raw/ itself must be a real directory: if it were a symlink, containment
+	// inside it would mean nothing (hyperguild#153 item 4).
+	if fi, lerr := os.Lstat(filepath.Join(brainDir, "raw")); lerr != nil || fi.Mode()&os.ModeSymlink != 0 || !fi.IsDir() {
+		return "", ErrOutsideIngestRoot
+	}
+	root, err := filepath.EvalSymlinks(filepath.Join(brainDir, "raw"))
+	if err != nil {
+		return "", ErrOutsideIngestRoot
+	}
+	if !filepath.IsAbs(p) {
+		p = filepath.Join(root, p)
+	}
+	real, err := filepath.EvalSymlinks(filepath.Clean(p))
+	if err != nil {
+		return "", ErrOutsideIngestRoot
+	}
+	rel, err := filepath.Rel(root, real)
+	if err != nil || rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) || filepath.IsAbs(rel) {
+		return "", ErrOutsideIngestRoot
+	}
+	return real, nil
+}
+
+// ReadIngestFile extracts text from an ingest path already confined by
+// ResolveIngestPath, reading it through the raw/ root rather than reopening
+// the path by name (hyperguild#153 item 3): if the file is swapped for a
+// symlink after the check, the read still cannot leave raw/.
+func ReadIngestFile(brainDir, resolved string) (string, error) {
+	root, rawPath, err := OpenRawRoot(brainDir)
+	if err != nil {
+		return "", ErrOutsideIngestRoot
+	}
+	defer func() { _ = root.Close() }()
+	realRoot, err := filepath.EvalSymlinks(rawPath)
+	if err != nil {
+		return "", ErrOutsideIngestRoot
+	}
+	rel, err := filepath.Rel(realRoot, resolved)
+	if err != nil || rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) || filepath.IsAbs(rel) {
+		return "", ErrOutsideIngestRoot
+	}
+	return extract.TextIn(root, rel)
+}

ingestion/internal/api/ingestpath_root_test.go

@@ -0,0 +1,88 @@
+package api_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
+)
+
+// hyperguild#149: /ingest-path and MCP brain_ingest read a caller-chosen
+// server path, so any file the pod could read (the ServiceAccount token,
+// /etc/passwd) could be pulled into the brain and read back out. Ingest paths
+// now resolve inside brain/raw/ — the inbox the watcher already owns — with
+// symlinks evaluated, or are refused.
+func TestResolveIngestPathConfinesToRawInbox(t *testing.T) {
+	brain := t.TempDir()
+	raw := filepath.Join(brain, "raw")
+	require.NoError(t, os.MkdirAll(filepath.Join(raw, "sub"), 0o755))
+	require.NoError(t, os.WriteFile(filepath.Join(raw, "sub", "ok.md"), []byte("x"), 0o644))
+	outside := filepath.Join(t.TempDir(), "secret.txt")
+	require.NoError(t, os.WriteFile(outside, []byte("s"), 0o644))
+	require.NoError(t, os.Symlink(outside, filepath.Join(raw, "link.md")))
+	require.NoError(t, os.Symlink(filepath.Dir(outside), filepath.Join(raw, "dirlink")))
+
+	for _, ok := range []string{filepath.Join(raw, "sub", "ok.md"), "sub/ok.md", raw, "sub"} {
+		_, err := api.ResolveIngestPath(brain, ok)
+		assert.NoError(t, err, ok)
+	}
+	for _, bad := range []string{
+		"/etc/hostname", outside, "../secret.txt", filepath.Join(raw, "..", "wiki"),
+		filepath.Join(raw, "link.md"), filepath.Join(raw, "dirlink", "secret.txt"),
+		raw + "-evil/x.md", "",
+	} {
+		_, err := api.ResolveIngestPath(brain, bad)
+		assert.Error(t, err, "must refuse %q", bad)
+	}
+}
+
+func TestIngestPathRefusesAPathOutsideTheInbox(t *testing.T) {
+	_, h := setup(t)
+	body, _ := json.Marshal(map[string]any{"path": "/etc/hostname"})
+	rec := httptest.NewRecorder()
+	h.IngestPath(rec, httptest.NewRequest(http.MethodPost, "/ingest-path", bytes.NewReader(body)))
+	assert.Equal(t, http.StatusBadRequest, rec.Code)
+	assert.Contains(t, rec.Body.String(), "raw")
+}
+
+// A directory ingest must not follow a symlinked FILE inside raw/ out of it.
+func TestIngestPathDirectoryWalkSkipsSymlinksLeavingTheInbox(t *testing.T) {
+	dir, h := setup(t)
+	raw := filepath.Join(dir, "raw", "batch")
+	require.NoError(t, os.MkdirAll(raw, 0o755))
+	outside := filepath.Join(t.TempDir(), "secret.md")
+	require.NoError(t, os.WriteFile(outside, []byte("# secret\n\nSENTINEL-149-OUTSIDE"), 0o644))
+	require.NoError(t, os.Symlink(outside, filepath.Join(raw, "leak.md")))
+	body, _ := json.Marshal(map[string]any{"path": "batch", "source": "walk"})
+	rec := httptest.NewRecorder()
+	h.IngestPath(rec, httptest.NewRequest(http.MethodPost, "/ingest-path", bytes.NewReader(body)))
+	assert.Contains(t, rec.Body.String(), "skipped")
+	assert.NotContains(t, rec.Body.String(), "SENTINEL-149-OUTSIDE")
+}
+
+// PR #152 review: the raw EvalSymlinks error told an authenticated caller
+// whether any server file existed ("no such file") or was unreadable
+// ("permission denied"), and leaked the brain directory. Every refusal now
+// reads the same.
+func TestResolveIngestPathRefusalsAreIndistinguishable(t *testing.T) {
+	brain := t.TempDir()
+	require.NoError(t, os.MkdirAll(filepath.Join(brain, "raw"), 0o755))
+	var msgs []string
+	for _, p := range []string{"/etc/hostname", "/etc/definitely-not-here-149", "../x", "nope/missing.md", ""} {
+		_, err := api.ResolveIngestPath(brain, p)
+		require.Error(t, err, p)
+		msgs = append(msgs, err.Error())
+		assert.NotContains(t, err.Error(), brain, "refusal for %q leaks the brain dir", p)
+	}
+	for _, m := range msgs[1:] {
+		assert.Equal(t, msgs[0], m)
+	}
+}

ingestion/internal/api/promote.go

@@ -1,7 +1,9 @@
 package api
 
 import (
+	"errors"
 	"fmt"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -28,25 +30,25 @@ var datePrefix = regexp.MustCompile(`^\d{4}-\d{2}-\d{2}-`)
 // (natural review order). An absent raw/ dir yields an empty slice, not an
 // error. Only .md files are listed; tunnel-candidate files are skipped.
 func ListPending(brainDir string) ([]PendingNote, error) {
-	dir := filepath.Join(brainDir, "raw")
+	root, _, err := OpenRawRoot(brainDir)
-	entries, err := os.ReadDir(dir)
 	if err != nil {
-		if os.IsNotExist(err) {
+		if errors.Is(err, os.ErrNotExist) {
 			return []PendingNote{}, nil
 		}
 		return nil, fmt.Errorf("read raw dir: %w", err)
 	}
+	defer func() { _ = root.Close() }()
+	entries, err := fs.ReadDir(root.FS(), ".")
+	if err != nil {
+		return nil, fmt.Errorf("read raw dir: %w", err)
+	}
 
 	out := make([]PendingNote, 0, len(entries))
 	for _, e := range entries {
-		if e.IsDir() || !strings.HasSuffix(e.Name(), ".md") || strings.HasPrefix(e.Name(), "tunnel-candidates-") {
+		if !e.Type().IsRegular() || !strings.HasSuffix(e.Name(), ".md") || strings.HasPrefix(e.Name(), "tunnel-candidates-") {
-			continue
+			continue // directories, and symlinks whose target may be anywhere (#153)
 		}
-		info, statErr := e.Info()
+		raw, info, readErr := readRawNote(root, e.Name())
-		if statErr != nil {
-			continue
-		}
-		raw, readErr := os.ReadFile(filepath.Join(dir, e.Name()))
 		if readErr != nil {
 			continue
 		}
@@ -72,6 +74,10 @@ type PromoteOptions struct {
 	Wing     string
 	Hall     string
 	Slug     string // optional; defaults to Filename minus date prefix + .md
+	// Origin/WrittenBy re-attribute the promoted note to the promoter: the raw
+	// note's own frontmatter claims are not provenance (hyperguild#145).
+	Origin    string
+	WrittenBy string
 }
 
 // PromoteNote moves a note from brain/raw/ into the structured wiki: it
@@ -101,12 +107,9 @@ func PromoteNote(brainDir string, opts PromoteOptions) (string, error) {
 	}
 
 	src := filepath.Join(brainDir, "raw", base)
-	raw, err := os.ReadFile(src)
+	raw, err := readRawSource(brainDir, base)
 	if err != nil {
-		if os.IsNotExist(err) {
+		return "", err
-			return "", fmt.Errorf("pending note %q does not exist in raw/", base)
-		}
-		return "", fmt.Errorf("read source: %w", err)
 	}
 
 	// Collision: never silently overwrite an existing promoted note.
@@ -128,7 +131,11 @@ func PromoteNote(brainDir string, opts PromoteOptions) (string, error) {
 		return "", fmt.Errorf("create wing dir: %w", err)
 	}
 	// Write-then-delete: the source survives any write failure.
-	if err := os.WriteFile(dest, []byte(fm.render()+body), 0o644); err != nil {
+	promoted, err := StampProvenance(fm.render()+body, opts.Origin, opts.WrittenBy)
+	if err != nil {
+		return "", err
+	}
+	if err := os.WriteFile(dest, []byte(promoted), 0o644); err != nil {
 		return "", fmt.Errorf("write promoted note: %w", err)
 	}
 	if err := os.Remove(src); err != nil {
@@ -172,12 +179,9 @@ func RejectNote(brainDir string, opts RejectOptions) (string, error) {
 	}
 
 	src := filepath.Join(brainDir, "raw", base)
-	raw, err := os.ReadFile(src)
+	raw, err := readRawSource(brainDir, base)
 	if err != nil {
-		if os.IsNotExist(err) {
+		return "", err
-			return "", fmt.Errorf("pending note %q does not exist in raw/", base)
-		}
-		return "", fmt.Errorf("read source: %w", err)
 	}
 
 	dest := filepath.Join(brainDir, "raw", "rejected", base)
@@ -216,3 +220,24 @@ func excerpt(s string, n int) string {
 	}
 	return strings.TrimSpace(string(r))
 }
+
+// readRawSource reads a pending note for promote/reject through the raw root,
+// refusing symlinks and a symlinked raw/ (hyperguild#153).
+func readRawSource(brainDir, base string) ([]byte, error) {
+	root, _, err := OpenRawRoot(brainDir)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, fmt.Errorf("pending note %q does not exist in raw/", base)
+		}
+		return nil, fmt.Errorf("read source: %w", err)
+	}
+	defer func() { _ = root.Close() }()
+	raw, _, err := readRawNote(root, base)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, fmt.Errorf("pending note %q does not exist in raw/", base)
+		}
+		return nil, fmt.Errorf("read source: %w", err)
+	}
+	return raw, nil
+}

ingestion/internal/api/provenance.go

@@ -0,0 +1,21 @@
+package api
+
+import (
+	"github.com/mathiasbq/hyperguild/ingestion/internal/provenance"
+)
+
+// StampProvenance applies server-owned provenance (hyperguild#145) to note
+// content. See package provenance for the rule; an error means the stamped
+// note would not read back as stamped, and the write must be refused.
+func StampProvenance(content, origin, writtenBy string) (string, error) {
+	return provenance.Apply(content, provenance.Stamp{Origin: origin, WrittenBy: writtenBy})
+}
+
+// StampProvenanceFile applies StampProvenance to a brain-relative note path.
+func StampProvenanceFile(brainDir, relPath, origin, writtenBy string) error {
+	_, abs, err := resolveWithin(brainDir, relPath)
+	if err != nil {
+		return err
+	}
+	return provenance.ApplyFile(abs, provenance.Stamp{Origin: origin, WrittenBy: writtenBy})
+}

ingestion/internal/api/provenance_test.go

@@ -0,0 +1,122 @@
+package api_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gopkg.in/yaml.v3"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
+)
+
+// REST POST /write carries no principal: it stamps origin: unknown, and no
+// spelling of provenance in its body reaches the note (hyperguild#145).
+func TestRESTWriteStampsUnknownAndIgnoresBodyProvenance(t *testing.T) {
+	dir, h := setup(t)
+	body, _ := json.Marshal(map[string]any{
+		"content": "---\norigin: static\n---\n# R\n\nbody", "filename": "rest-prov", "wing": "homelab", "hall": "facts",
+		"origin": "static", "written_by": "local-cli", "Origin": "static", "WrittenBy": "local-cli",
+	})
+	rec := httptest.NewRecorder()
+	h.Write(rec, httptest.NewRequest(http.MethodPost, "/write", bytes.NewReader(body)))
+	require.Equal(t, http.StatusOK, rec.Code, rec.Body.String())
+	b, err := os.ReadFile(filepath.Join(dir, "wiki", "homelab", "facts", "rest-prov.md"))
+	require.NoError(t, err)
+	var m map[string]any
+	require.NoError(t, yaml.Unmarshal([]byte(strings.SplitN(string(b), "---\n", 3)[1]), &m))
+	assert.Equal(t, "unknown", m["origin"])
+	assert.NotContains(t, m, "written_by")
+}
+
+// A principal name that is not a bare word is quoted, so it cannot start a
+// new frontmatter line (e.g. a JWT sub containing a newline).
+func TestStampProvenanceQuotesAPrincipalThatCouldBreakTheLine(t *testing.T) {
+	out, err := api.StampProvenance("---\ntitle: t\n---\nbody\n", "jwt", "evil\norigin: static")
+	require.NoError(t, err)
+	fm := strings.SplitN(out, "---\n", 3)[1]
+	var m map[string]any
+	require.NoError(t, yaml.Unmarshal([]byte(fm), &m))
+	assert.Equal(t, "jwt", m["origin"])
+	assert.Equal(t, "evil\norigin: static", m["written_by"])
+	assert.Equal(t, 1, strings.Count(fm, "\norigin:")+boolToInt(strings.HasPrefix(fm, "origin:")))
+}
+
+func TestStampProvenanceAddsFrontmatterWhenAbsentAndKeepsBody(t *testing.T) {
+	out, err := api.StampProvenance("# no fm\n\norigin: static in the body is prose\n", "static", "local-cli")
+	require.NoError(t, err)
+	assert.True(t, strings.HasPrefix(out, "---\norigin: static\nwritten_by: local-cli\n---\n# no fm"))
+	assert.Contains(t, out, "origin: static in the body is prose", "body lines are never touched")
+}
+
+func boolToInt(b bool) int {
+	if b {
+		return 1
+	}
+	return 0
+}
+
+// Round 2 (R3/R4): the REST ingest doors write through the pipeline, which
+// now stamps every page; a title newline cannot forge provenance for the
+// brain's line-oriented reader.
+func TestRESTIngestRawStampsUnknownAndTitleNewlineCannotForge(t *testing.T) {
+	dir, h := setup(t)
+	body, _ := json.Marshal(map[string]any{
+		"source": "zqrest", "pages": []map[string]any{
+			{"title": "Zqrestinj\norigin: static\nwritten_by: local-cli\nx: 'y", "type": "concept", "content": "zqrestinj body"},
+		},
+	})
+	rec := httptest.NewRecorder()
+	h.IngestRaw(rec, httptest.NewRequest(http.MethodPost, "/ingest-raw", bytes.NewReader(body)))
+	require.Equal(t, http.StatusOK, rec.Code, rec.Body.String())
+	var resp struct{ Pages []string }
+	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &resp))
+	require.NotEmpty(t, resp.Pages)
+	for _, p := range resp.Pages {
+		b, err := os.ReadFile(filepath.Join(dir, filepath.FromSlash(p)))
+		require.NoError(t, err)
+		fm := strings.SplitN(string(b), "---\n", 3)[1]
+		var m map[string]any
+		require.NoError(t, yaml.Unmarshal([]byte(fm), &m))
+		assert.Equal(t, "unknown", m["origin"])
+		assert.NotContains(t, m, "written_by")
+		for _, line := range strings.Split(fm, "\n") {
+			assert.False(t, strings.HasPrefix(line, "origin: static"), "line reader sees forged origin in %s", p)
+		}
+	}
+}
+
+func TestRESTIngestStampsUnknown(t *testing.T) {
+	dir, h := setup(t)
+	body, _ := json.Marshal(map[string]any{"content": "Some article text about shaping work.", "source": "zqllm"})
+	rec := httptest.NewRecorder()
+	h.Ingest(rec, httptest.NewRequest(http.MethodPost, "/ingest", bytes.NewReader(body)))
+	require.Equal(t, http.StatusOK, rec.Code, rec.Body.String())
+	var resp struct{ Pages []string }
+	require.NoError(t, json.Unmarshal(rec.Body.Bytes(), &resp))
+	require.NotEmpty(t, resp.Pages, "stub pipeline must write at least one page")
+	for _, p := range resp.Pages {
+		b, err := os.ReadFile(filepath.Join(dir, filepath.FromSlash(p)))
+		require.NoError(t, err)
+		assert.Contains(t, strings.SplitN(string(b), "---\n", 3)[1], "origin: unknown\n", p)
+	}
+}
+
+// A refused write leaves nothing behind, not even an empty hall directory
+// (brain#21's invariant, round 3 non-blocking finding).
+func TestWriteNoteRefusedForProvenanceLeavesNoDirectory(t *testing.T) {
+	dir := t.TempDir()
+	_, err := api.WriteNote(dir, api.WriteNoteOptions{
+		Content: "# x\n\nbody", Wing: "freshwing", Hall: "facts", Filename: "x", Origin: "jwt", WrittenBy: "bad\xff",
+	})
+	require.Error(t, err)
+	_, statErr := os.Stat(filepath.Join(dir, "wiki", "freshwing"))
+	assert.True(t, os.IsNotExist(statErr), "no wing directory may be created by a refused write")
+}

ingestion/internal/api/raw_race_test.go

@@ -0,0 +1,178 @@
+package api_test
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"syscall"
+	"testing"
+	"time"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
+)
+
+// hyperguild#153 / PR #156: behavioural race tests, so the control does not
+// rest on lints that list forbidden APIs (round 3: an os.ReadFile or
+// Root.ReadFile rewrite passed the lint and leaked 19k times in 4s). A
+// swapper keeps renaming a regular note, a symlink to an outside file, or a
+// FIFO into raw/r.md while the public readers loop. Any leaked byte fails;
+// any hang fails.
+
+const raceSentinel = "SENTINEL-153-RACE"
+
+// startSwapper runs fn until the test ends, and waits for it to exit before
+// t.TempDir's cleanup removes the directory it writes into (hyperguild#162:
+// an unawaited swapper raced the cleanup, "directory not empty").
+func startSwapper(t *testing.T, fn func(stop *atomic.Bool)) {
+	t.Helper()
+	var stop atomic.Bool
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() { defer wg.Done(); fn(&stop) }()
+	t.Cleanup(func() { stop.Store(true); wg.Wait() })
+}
+
+func swap(raw, outside string, fifo bool, stop *atomic.Bool) {
+	tgt := filepath.Join(raw, "r.md")
+	for i := 0; !stop.Load(); i++ {
+		tmp := filepath.Join(raw, ".swap")
+		_ = os.Remove(tmp)
+		switch {
+		case i%2 == 0:
+			_ = os.WriteFile(tmp, []byte("# r\n\ninside"), 0o644)
+		case fifo:
+			_ = syscall.Mkfifo(tmp, 0o644)
+		default:
+			_ = os.Symlink(outside, tmp)
+		}
+		_ = os.Rename(tmp, tgt)
+	}
+}
+
+func raceBrain(t *testing.T) (brain, raw, outside string) {
+	t.Helper()
+	brain = t.TempDir()
+	raw = filepath.Join(brain, "raw")
+	if err := os.MkdirAll(raw, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	outside = filepath.Join(t.TempDir(), "secret.md")
+	if err := os.WriteFile(outside, []byte("# s\n\n"+raceSentinel), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(raw, "r.md"), []byte("# r\n\ninside"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	return brain, raw, outside
+}
+
+// readers runs every public raw/ reader once and returns all text they
+// produced (excerpts, extracted text).
+func readers(brain, raw string) string {
+	var b strings.Builder
+	if ns, err := api.ListPending(brain); err == nil {
+		for _, n := range ns {
+			b.WriteString(n.Excerpt)
+		}
+	}
+	if s, err := api.ReadIngestFile(brain, filepath.Join(raw, "r.md")); err == nil {
+		b.WriteString(s)
+	}
+	return b.String()
+}
+
+func TestRawReadersLeakNothingUnderASymlinkSwapRace(t *testing.T) {
+	brain, raw, outside := raceBrain(t)
+	startSwapper(t, func(stop *atomic.Bool) { swap(raw, outside, false, stop) })
+	leaks, iters := 0, 0
+	for deadline := time.Now().Add(1500 * time.Millisecond); time.Now().Before(deadline); iters++ {
+		leaks += strings.Count(readers(brain, raw), raceSentinel)
+	}
+	if leaks > 0 {
+		t.Fatalf("outside file leaked %d times in %d iterations", leaks, iters)
+	}
+	t.Logf("%d iterations, 0 leaks", iters)
+}
+
+func TestRawReadersDoNotHangUnderAFIFOSwapRace(t *testing.T) {
+	brain, raw, outside := raceBrain(t)
+	startSwapper(t, func(stop *atomic.Bool) { swap(raw, outside, true, stop) })
+	var iters atomic.Int64
+	done := make(chan struct{})
+	go func() {
+		for deadline := time.Now().Add(1500 * time.Millisecond); time.Now().Before(deadline); {
+			_ = readers(brain, raw)
+			iters.Add(1)
+		}
+		close(done)
+	}()
+	select {
+	case <-done:
+	case <-time.After(6 * time.Second):
+		// Unblock the stuck open so the test process can exit.
+		if f, err := os.OpenFile(filepath.Join(raw, "r.md"), os.O_WRONLY|syscall.O_NONBLOCK, 0); err == nil {
+			_ = f.Close()
+		}
+		t.Fatalf("a raw/ reader hung on a swapped-in FIFO after %d iterations", iters.Load())
+	}
+}
+
+// PR #156 round 4: the pdf/docmark branch of TextIn copies the file through
+// the root to a temp file; pointing the extractor back at the raw/ path by
+// name stayed green because the race tests only used r.md (a stub docmark
+// then received the outside file's bytes 34k times in 4s). This races a
+// symlink into raw/r.docx and has a fake docmark count the sentinel in every
+// document it is sent.
+func TestDocmarkExtractionLeaksNothingUnderASymlinkSwapRace(t *testing.T) {
+	var seen atomic.Int64
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req struct {
+			Params struct {
+				Arguments struct {
+					ContentBase64 string `json:"content_base64"`
+				} `json:"arguments"`
+			} `json:"params"`
+		}
+		_ = json.NewDecoder(r.Body).Decode(&req)
+		if b, err := base64.StdEncoding.DecodeString(req.Params.Arguments.ContentBase64); err == nil &&
+			strings.Contains(string(b), raceSentinel) {
+			seen.Add(1)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"jsonrpc":"2.0","id":1,"result":{"content":[{"type":"text","text":"converted"}]}}`))
+	}))
+	defer srv.Close()
+	t.Setenv("DOCMARK_URL", srv.URL)
+
+	brain, raw, outside := raceBrain(t)
+	tgt := filepath.Join(raw, "r.docx")
+	if err := os.WriteFile(tgt, []byte("inside docx bytes"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	startSwapper(t, func(stop *atomic.Bool) {
+		for i := 0; !stop.Load(); i++ {
+			tmp := filepath.Join(raw, ".swapdocx")
+			_ = os.Remove(tmp)
+			if i%2 == 0 {
+				_ = os.WriteFile(tmp, []byte("inside docx bytes"), 0o644)
+			} else {
+				_ = os.Symlink(outside, tmp)
+			}
+			_ = os.Rename(tmp, tgt)
+		}
+	})
+	iters := 0
+	for deadline := time.Now().Add(1500 * time.Millisecond); time.Now().Before(deadline); iters++ {
+		_, _ = api.ReadIngestFile(brain, tgt)
+	}
+	if n := seen.Load(); n > 0 {
+		t.Fatalf("docmark received the outside file %d times in %d iterations", n, iters)
+	}
+	t.Logf("%d iterations, 0 leaks to docmark", iters)
+}

ingestion/internal/api/raw_symlink_test.go

@@ -0,0 +1,80 @@
+package api_test
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
+)
+
+// hyperguild#153: readers of brain/raw/ followed symlinks. /pending showed the
+// target's contents and promote would copy it into wiki/ (and brain-sync to
+// Gitea). raw/ is writable via Syncthing, so a symlink there is reachable
+// input. Every raw/ reader now treats a symlink as not-a-note.
+const sentinel153 = "SENTINEL-153-OUTSIDE"
+
+func rawWithSymlink(t *testing.T) (brain string) {
+	t.Helper()
+	brain = t.TempDir()
+	raw := filepath.Join(brain, "raw")
+	require.NoError(t, os.MkdirAll(raw, 0o755))
+	outside := filepath.Join(t.TempDir(), "secret.md")
+	require.NoError(t, os.WriteFile(outside, []byte("---\ncreated_at: 2026-01-01T00:00:00Z\n---\n# s\n\n"+sentinel153), 0o644))
+	require.NoError(t, os.Symlink(outside, filepath.Join(raw, "2026-01-01-leak.md")))
+	require.NoError(t, os.WriteFile(filepath.Join(raw, "2026-01-02-real.md"), []byte("# real\n\nreal body"), 0o644))
+	return brain
+}
+
+func TestListPendingSkipsSymlinkedNotes(t *testing.T) {
+	notes, err := api.ListPending(rawWithSymlink(t))
+	require.NoError(t, err)
+	var names []string
+	for _, n := range notes {
+		names = append(names, n.Filename)
+		assert.NotContains(t, n.Excerpt, sentinel153)
+	}
+	assert.Equal(t, []string{"2026-01-02-real.md"}, names)
+}
+
+func TestPromoteNoteRefusesASymlinkedSource(t *testing.T) {
+	brain := rawWithSymlink(t)
+	_, err := api.PromoteNote(brain, api.PromoteOptions{Filename: "2026-01-01-leak.md", Wing: "testing", Hall: "facts"})
+	require.Error(t, err)
+	_, statErr := os.Stat(filepath.Join(brain, "wiki", "testing", "facts", "leak.md"))
+	assert.True(t, os.IsNotExist(statErr), "nothing may be promoted from a symlink")
+}
+
+func TestRejectNoteRefusesASymlinkedSource(t *testing.T) {
+	brain := rawWithSymlink(t)
+	_, err := api.RejectNote(brain, api.RejectOptions{Filename: "2026-01-01-leak.md"})
+	require.Error(t, err)
+	b, _ := os.ReadFile(filepath.Join(brain, "raw", "rejected", "2026-01-01-leak.md"))
+	assert.False(t, strings.Contains(string(b), sentinel153))
+}
+
+// Item 4: if raw/ itself is a symlink, containment inside it means nothing.
+func TestResolvePendingPromoteRejectAndReadIngestRefuseASymlinkedRawRoot(t *testing.T) {
+	brain := t.TempDir()
+	elsewhere := t.TempDir()
+	require.NoError(t, os.WriteFile(filepath.Join(elsewhere, "x.md"), []byte("# x\n\n"+sentinel153), 0o644))
+	require.NoError(t, os.Symlink(elsewhere, filepath.Join(brain, "raw")))
+
+	_, err := api.ResolveIngestPath(brain, "x.md")
+	assert.Error(t, err, "ingest must refuse a symlinked raw/")
+	notes, err := api.ListPending(brain)
+	assert.Error(t, err, "pending must refuse a symlinked raw/")
+	assert.Empty(t, notes)
+	_, err = api.PromoteNote(brain, api.PromoteOptions{Filename: "x.md", Wing: "testing", Hall: "facts"})
+	assert.Error(t, err, "promote must refuse a symlinked raw/")
+	_, err = api.RejectNote(brain, api.RejectOptions{Filename: "x.md"})
+	assert.Error(t, err, "reject must refuse a symlinked raw/")
+	text, err := api.ReadIngestFile(brain, filepath.Join(elsewhere, "x.md"))
+	assert.Error(t, err, "ReadIngestFile must refuse a symlinked raw/")
+	assert.NotContains(t, text, sentinel153)
+	// The watcher's refusal is tested in internal/watcher.
+}

ingestion/internal/api/rawroot.go

@@ -0,0 +1,67 @@
+package api
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/extract"
+)
+
+// errNotANote is returned for a raw/ entry that is not a regular file — in
+// particular a symlink, whose target may be anywhere (hyperguild#153).
+var errNotANote = errors.New("not a regular note file in raw/ (symlinks are refused)")
+
+// errRawNotDir means brain/raw is not a real directory (e.g. a symlink), so
+// containment inside it would mean nothing (hyperguild#153 item 4).
+var errRawNotDir = errors.New("brain/raw is not a real directory")
+
+// OpenRawRoot opens brain/raw as an os.Root, refusing a raw/ that is itself a
+// symlink. Reads through the root cannot leave it, even if an entry is
+// swapped for a symlink between a check and the read. It returns the root
+// and raw/'s path. A missing raw/ returns an error wrapping os.ErrNotExist.
+func OpenRawRoot(brainDir string) (*os.Root, string, error) {
+	p := filepath.Join(brainDir, "raw")
+	fi, err := os.Lstat(p)
+	if err != nil {
+		return nil, "", err
+	}
+	if fi.Mode()&os.ModeSymlink != 0 || !fi.IsDir() {
+		return nil, "", errRawNotDir
+	}
+	r, err := os.OpenRoot(p)
+	if err != nil {
+		return nil, "", fmt.Errorf("open raw root: %w", err)
+	}
+	return r, p, nil
+}
+
+// readRawNote reads one raw/ entry by basename through the root, refusing
+// anything that is not a regular file.
+//
+// Accepted residual: a HARD link to an outside file is a regular file and is
+// read. Syncthing syncs contents, not links, so a peer cannot create one;
+// fs.protected_hardlinks=1 and the pod's secrets live on a different
+// filesystem from the brain volume, so a local caller cannot link them in.
+// Refusing Nlink > 1 is the next step if either assumption changes.
+func readRawNote(r *os.Root, base string) ([]byte, os.FileInfo, error) {
+	fi, err := r.Lstat(base)
+	if err != nil {
+		return nil, nil, err
+	}
+	if !fi.Mode().IsRegular() {
+		return nil, nil, errNotANote
+	}
+	f, _, err := extract.OpenRegular(r, base)
+	if err != nil {
+		return nil, nil, err
+	}
+	defer func() { _ = f.Close() }()
+	b, err := io.ReadAll(f)
+	if err != nil {
+		return nil, nil, err
+	}
+	return b, fi, nil
+}

ingestion/internal/api/readnote_root_test.go

@@ -0,0 +1,43 @@
+package api_test
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs/brainfstest"
+)
+
+// hyperguild#157 slice 2: ReadNote (brain_get, read-after-write) read by
+// path; it now reads through brainfs.
+func TestReadNoteRefusesSymlinksAndSurvivesSwapRaces(t *testing.T) {
+	brain := t.TempDir()
+	facts := filepath.Join(brain, "wiki", "w", "facts")
+	require.NoError(t, os.MkdirAll(facts, 0o755))
+	require.NoError(t, os.Symlink(brainfstest.Outside(t), filepath.Join(facts, "leak.md")))
+	_, body, _, err := api.ReadNote(brain, "wiki/w/facts/leak.md")
+	assert.Error(t, err)
+	assert.NotContains(t, body, brainfstest.Sentinel)
+
+	p := filepath.Join(facts, "r.md")
+	require.NoError(t, os.WriteFile(p, []byte("---\nx: y\n---\ninside"), 0o644))
+	fm, body, _, err := api.ReadNote(brain, "wiki/w/facts/r.md")
+	require.NoError(t, err)
+	assert.Equal(t, "y", fm["x"])
+	assert.Contains(t, body, "inside")
+	read := func() string {
+		fm, body, _, _ := api.ReadNote(brain, "wiki/w/facts/r.md")
+		s := body
+		for k, v := range fm {
+			s += k + v
+		}
+		return s
+	}
+	brainfstest.AssertNoLeak(t, p, "---\nx: y\n---\ninside", 1500*time.Millisecond, read)
+	brainfstest.AssertNoHang(t, p, "---\nx: y\n---\ninside", 1500*time.Millisecond, 6*time.Second, func() { _ = read() })
+}

ingestion/internal/api/update.go

@@ -3,14 +3,18 @@ package api
 import (
 	"crypto/sha256"
 	"encoding/hex"
+	"errors"
 	"fmt"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"strings"
 	"time"
 
 	"github.com/mathiasbq/hyperguild/ingestion/internal/brain"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/claim"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/notes"
 )
 
 // ContentHash returns the lowercase hex sha256 of b. It is the note's
@@ -46,6 +50,11 @@ type UpdateNoteOptions struct {
 	Slug    string
 	Content string // new full body (whole-note replace)
 	Reason  string // optional; stamped as supersede_reason
+	// Origin/WrittenBy re-stamp provenance to the updating principal: the
+	// body is replaced wholesale, so the last writer is the author of what
+	// a reader sees (hyperguild#145). Never taken from Content's fragment.
+	Origin    string
+	WrittenBy string
 }
 
 // UpdateNote supersedes an existing note in place. It replaces the body
@@ -85,14 +94,23 @@ func UpdateNote(brainDir string, opts UpdateNoteOptions) (relPath, contentHash,
 		rel = filepath.ToSlash(rel)
 	}
 
-	rel, abs, err := resolveWithin(brainDir, rel)
+	// The path is caller-supplied (brain_update): resolve it as brain_edit
+	// does, knowledge/ and wiki/ notes only, and read and rewrite it through
+	// the brain root, never through a symlink (hyperguild#169).
+	t, err := notes.Resolve(brainDir, rel, notes.ScopeNotes)
 	if err != nil {
 		return "", "", "", err
 	}
-
+	rel = t.Rel
-	prior, err := os.ReadFile(abs)
+	bfs, err := brainfs.Open(brainDir)
 	if err != nil {
-		if os.IsNotExist(err) {
+		return "", "", "", fmt.Errorf("open brain: %w", err)
+	}
+	defer func() { _ = bfs.Close() }()
+
+	prior, err := bfs.ReadRegular(rel)
+	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
 			return "", "", "", fmt.Errorf("note %q does not exist: use brain_write to create", rel)
 		}
 		return "", "", "", fmt.Errorf("read target: %w", err)
@@ -110,9 +128,23 @@ func UpdateNote(brainDir string, opts UpdateNoteOptions) (relPath, contentHash,
 
 	fm, _ := parseFrontmatter(string(prior))
 	for _, l := range contentFM.lines {
-		if l.key != "" {
+		// updated_at/supersedes/supersede_reason are this function's own
-			fm.set(l.key, l.value)
+		// output, not something a caller's fragment sets — updated_at and
+		// supersedes are already unconditionally re-set below regardless of
+		// what the loop does with them, but supersede_reason is only
+		// re-set when opts.Reason is non-empty, so without this skip a
+		// caller could set it via its own fragment and have it survive
+		// even when Reason is empty, bypassing the one intended entry
+		// point for that field (hyperguild#125, found in #111's review).
+		// Skipping all three here rather than relying on the unconditional
+		// overwrites below to save the other two keeps the invariant
+		// explicit at the one place it can be silently broken by a future
+		// reordering, not implicit in call order.
+		if l.key == "" || l.key == "updated_at" || l.key == "supersedes" || l.key == "supersede_reason" ||
+			l.key == "origin" || l.key == "written_by" {
+			continue
 		}
+		fm.set(l.key, l.value)
 	}
 	fm.set("updated_at", time.Now().UTC().Format(time.RFC3339))
 	fm.set("supersedes", priorHash)
@@ -139,8 +171,12 @@ func UpdateNote(brainDir string, opts UpdateNoteOptions) (relPath, contentHash,
 		return "", "", "", fmt.Errorf("claim envelope: %w", err)
 	}
 
-	out := []byte(fm.render() + contentBody)
+	stamped, err := StampProvenance(fm.render()+contentBody, opts.Origin, opts.WrittenBy)
-	if err := os.WriteFile(abs, out, 0o644); err != nil {
+	if err != nil {
+		return "", "", "", err
+	}
+	out := []byte(stamped)
+	if err := bfs.WriteRegular(rel, out); err != nil {
 		return "", "", "", fmt.Errorf("write: %w", err)
 	}
 	return rel, ContentHash(out), priorHash, nil
@@ -151,11 +187,17 @@ func UpdateNote(brainDir string, opts UpdateNoteOptions) (relPath, contentHash,
 // write primitive behind brain_get: the hash it returns equals the hash
 // brain_write / brain_update returned for the same bytes.
 func ReadNote(brainDir, relPath string) (fm map[string]string, body, contentHash string, err error) {
-	_, abs, err := resolveWithin(brainDir, relPath)
+	rel, _, err := resolveWithin(brainDir, relPath)
 	if err != nil {
 		return nil, "", "", err
 	}
-	raw, err := os.ReadFile(abs)
+	// Through the brain root, regular files only (hyperguild#157).
+	bfs, err := brainfs.Open(brainDir)
+	if err != nil {
+		return nil, "", "", fmt.Errorf("read note: %w", err)
+	}
+	defer func() { _ = bfs.Close() }()
+	raw, err := bfs.ReadRegular(rel)
 	if err != nil {
 		if os.IsNotExist(err) {
 			return nil, "", "", fmt.Errorf("note %q does not exist", relPath)

ingestion/internal/api/update_scope_test.go

@@ -0,0 +1,112 @@
+package api_test
+
+import (
+	"os"
+	"path/filepath"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
+)
+
+// brain_update passed the caller's path through resolveWithin, a lexical
+// containment check only: any file in the brain could be superseded
+// (classification.yaml, raw/, sessions/), and a final symlink was written
+// through. It now resolves like brain_edit: knowledge/ and wiki/ notes only,
+// read and rewritten through the brain root.
+func TestUpdateNoteRefusesPathsOutsideKnowledgeAndWikiNotes(t *testing.T) {
+	brain := t.TempDir()
+	files := map[string]string{
+		"classification.yaml": "levels: {}\n",
+		"raw/r.md":            "raw\n",
+		"sessions/s.jsonl":    "{}\n",
+		"wiki/w/facts/ok.md":  "---\ntitle: ok\n---\nold\n",
+		"knowledge/k.md":      "---\ntitle: k\n---\nold\n",
+		"wiki/w/facts/x.txt":  "txt\n",
+	}
+	for rel, body := range files {
+		p := filepath.Join(brain, filepath.FromSlash(rel))
+		require.NoError(t, os.MkdirAll(filepath.Dir(p), 0o755))
+		require.NoError(t, os.WriteFile(p, []byte(body), 0o644))
+	}
+	for _, rel := range []string{"classification.yaml", "raw/r.md", "sessions/s.jsonl", "wiki/w/facts/x.txt", "wiki/w/../../raw/r.md"} {
+		_, _, _, err := api.UpdateNote(brain, api.UpdateNoteOptions{Path: rel, Content: "replaced"})
+		assert.Error(t, err, rel)
+	}
+	for rel, body := range files {
+		if rel == "wiki/w/facts/ok.md" || rel == "knowledge/k.md" {
+			continue
+		}
+		got, err := os.ReadFile(filepath.Join(brain, filepath.FromSlash(rel)))
+		require.NoError(t, err)
+		assert.Equal(t, body, string(got), rel)
+	}
+	for _, rel := range []string{"wiki/w/facts/ok.md", "knowledge/k.md"} {
+		_, _, _, err := api.UpdateNote(brain, api.UpdateNoteOptions{Path: rel, Content: "new body"})
+		require.NoError(t, err, "positive control: %s", rel)
+		got, _ := os.ReadFile(filepath.Join(brain, filepath.FromSlash(rel)))
+		assert.Contains(t, string(got), "new body")
+	}
+}
+
+func TestUpdateNoteDoesNotWriteThroughASymlinkedNote(t *testing.T) {
+	brain := t.TempDir()
+	facts := filepath.Join(brain, "wiki", "w", "facts")
+	require.NoError(t, os.MkdirAll(facts, 0o755))
+	victim := filepath.Join(brain, "raw", "victim.md")
+	require.NoError(t, os.MkdirAll(filepath.Dir(victim), 0o755))
+	require.NoError(t, os.WriteFile(victim, []byte("untouched\n"), 0o644))
+	require.NoError(t, os.Symlink(filepath.Join("..", "..", "..", "raw", "victim.md"), filepath.Join(facts, "l.md")))
+	_, _, _, err := api.UpdateNote(brain, api.UpdateNoteOptions{Path: "wiki/w/facts/l.md", Content: "replaced"})
+	assert.Error(t, err)
+	got, _ := os.ReadFile(victim)
+	assert.Equal(t, "untouched\n", string(got))
+}
+
+// The note is swapped between a regular file and an in-brain symlink to a
+// raw/ file while UpdateNote runs: the read and the write each refuse a
+// symlink, so the raw/ file is never rewritten.
+func TestUpdateNoteNeverRewritesASymlinkSwappedInForTheNote(t *testing.T) {
+	brain := t.TempDir()
+	facts := filepath.Join(brain, "wiki", "w", "facts")
+	require.NoError(t, os.MkdirAll(facts, 0o755))
+	victim := filepath.Join(brain, "raw", "victim.md")
+	require.NoError(t, os.MkdirAll(filepath.Dir(victim), 0o755))
+	require.NoError(t, os.WriteFile(victim, []byte("untouched\n"), 0o644))
+	note := filepath.Join(facts, "n.md")
+	body := "---\ntitle: n\n---\nold\n"
+	require.NoError(t, os.WriteFile(note, []byte(body), 0o644))
+
+	var stop atomic.Bool
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		tmp := note + ".swap"
+		for i := 0; !stop.Load(); i++ {
+			_ = os.Remove(tmp)
+			if i%2 == 0 {
+				_ = os.WriteFile(tmp, []byte(body), 0o644)
+			} else {
+				_ = os.Symlink(filepath.Join("..", "..", "..", "raw", "victim.md"), tmp)
+			}
+			_ = os.Rename(tmp, note)
+		}
+	}()
+	ok := 0
+	for deadline := time.Now().Add(1500 * time.Millisecond); time.Now().Before(deadline); {
+		if _, _, _, err := api.UpdateNote(brain, api.UpdateNoteOptions{Path: "wiki/w/facts/n.md", Content: "new"}); err == nil {
+			ok++
+		}
+	}
+	stop.Store(true)
+	wg.Wait()
+	got, _ := os.ReadFile(victim)
+	assert.Equal(t, "untouched\n", string(got))
+	assert.Positive(t, ok, "positive control: some updates reach the regular note")
+}

ingestion/internal/api/update_test.go

@@ -231,6 +231,45 @@ func TestUpdateThenReadRoundTripsHash(t *testing.T) {
 	assert.Equal(t, hash, readHash, "update content_hash must round-trip through ReadNote")
 }
 
+func TestUpdateNoteSupersedeReasonNotSettableViaCallerFragmentWhenReasonOptionEmpty(t *testing.T) {
+	// hyperguild#125, found in #111's review: the merge loop applied every
+	// field from the caller's leading frontmatter fragment, including
+	// supersede_reason -- which is only re-set unconditionally when
+	// opts.Reason is non-empty, so a caller could set it via its own
+	// fragment and have it survive even with Reason left empty, bypassing
+	// the one intended entry point for that field.
+	brainDir := t.TempDir()
+	rel := seedNote(t, brainDir, "wiki/a/facts/n.md", "---\nwing: a\nhall: facts\n---\nold\n")
+
+	_, _, _, err := UpdateNote(brainDir, UpdateNoteOptions{
+		Path:    rel,
+		Content: "---\nsupersede_reason: snuck in via the fragment\n---\nnew\n",
+		// Reason deliberately left empty.
+	})
+	require.NoError(t, err)
+
+	got, err := os.ReadFile(filepath.Join(brainDir, filepath.FromSlash(rel)))
+	require.NoError(t, err)
+	assert.NotContains(t, string(got), "supersede_reason",
+		"supersede_reason must not appear at all when opts.Reason is empty, regardless of what the fragment tried to set")
+}
+
+func TestUpdateNoteSupersedeReasonFromOptionStillWorks(t *testing.T) {
+	// Regression pin: the legitimate entry point (opts.Reason) must be
+	// completely unaffected by #125's fix.
+	brainDir := t.TempDir()
+	rel := seedNote(t, brainDir, "wiki/a/facts/n.md", "---\nwing: a\nhall: facts\n---\nold\n")
+
+	_, _, _, err := UpdateNote(brainDir, UpdateNoteOptions{
+		Path: rel, Content: "new\n", Reason: "facts changed",
+	})
+	require.NoError(t, err)
+
+	got, err := os.ReadFile(filepath.Join(brainDir, filepath.FromSlash(rel)))
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "supersede_reason: facts changed")
+}
+
 func TestContentHashStable(t *testing.T) {
 	assert.Equal(t, ContentHash([]byte("abc")), ContentHash([]byte("abc")))
 	assert.NotEqual(t, ContentHash([]byte("abc")), ContentHash([]byte("abd")))

ingestion/internal/audit/ntfy.go

@@ -49,7 +49,19 @@ func (n *NtfyNotifier) Notify(ctx context.Context, msg string) error {
 	}
 	defer func() { _ = resp.Body.Close() }()
 	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
-		return fmt.Errorf("ntfy notify: status %d", resp.StatusCode)
+		return &RejectedError{Status: resp.StatusCode}
 	}
 	return nil
 }
+
+// RejectedError is a non-2xx ntfy response.
+type RejectedError struct{ Status int }
+
+func (e *RejectedError) Error() string { return fmt.Sprintf("ntfy notify: status %d", e.Status) }
+
+// Permanent reports whether resending the same message cannot succeed: a 4xx
+// other than 429 (rate limited). Callers may drop such a message; anything
+// else (5xx, 429, transport errors) is an outage and must be retried.
+func (e *RejectedError) Permanent() bool {
+	return e.Status >= 400 && e.Status < 500 && e.Status != http.StatusTooManyRequests
+}

ingestion/internal/audit/ntfy_rejected_test.go

@@ -0,0 +1,27 @@
+package audit
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// A non-2xx ntfy response is a *RejectedError, and only a client-side refusal
+// other than rate limiting is permanent: callers may drop a message on a
+// permanent rejection and must retry the rest (hyperguild#157, PR #160).
+func TestNotifyClassifiesRejectionsAsPermanentOrNot(t *testing.T) {
+	for status, permanent := range map[int]bool{413: true, 400: true, 403: true, 429: false, 500: false, 503: false} {
+		srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) { w.WriteHeader(status) }))
+		err := NewNtfyNotifier(srv.URL, "").Notify(context.Background(), "m")
+		srv.Close()
+		var rej *RejectedError
+		require.True(t, errors.As(err, &rej), "status %d: %v", status, err)
+		assert.Equal(t, status, rej.Status)
+		assert.Equal(t, permanent, rej.Permanent(), "status %d", status)
+	}
+}

ingestion/internal/brain/tunnel.go

@@ -4,9 +4,12 @@ import (
 	"bufio"
 	"fmt"
 	"os"
+	"path"
 	"path/filepath"
 	"strings"
 	"time"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
 )
 
 // seeAlsoHeader is the markdown heading used to group cross-wing links.
@@ -197,6 +200,12 @@ func fileExists(p string) bool {
 // section headers. Rejects same-wing pairs (a tunnel is by definition
 // cross-wing) and missing notes.
 func WriteTunnel(brainDir, sourcePath, targetPath string) error {
+	if err := checkNotePath(sourcePath); err != nil {
+		return fmt.Errorf("source: %w", err)
+	}
+	if err := checkNotePath(targetPath); err != nil {
+		return fmt.Errorf("target: %w", err)
+	}
 	srcWing, err := wingOf(sourcePath)
 	if err != nil {
 		return fmt.Errorf("source: %w", err)
@@ -209,20 +218,50 @@ func WriteTunnel(brainDir, sourcePath, targetPath string) error {
 		return fmt.Errorf("tunnel must cross wings; got both in %q", srcWing)
 	}
 
-	srcFull := filepath.Join(brainDir, filepath.FromSlash(sourcePath))
+	// Both notes are read and rewritten through the brain root, regular
-	tgtFull := filepath.Join(brainDir, filepath.FromSlash(targetPath))
+	// files only: brain_tunnel passes caller-supplied paths, and the brain is
-	if _, err := os.Stat(srcFull); err != nil {
+	// a Syncthing folder that can hold symlinks.
+	bfs, err := brainfs.Open(brainDir)
+	if err != nil {
+		return fmt.Errorf("open brain: %w", err)
+	}
+	defer func() { _ = bfs.Close() }()
+	srcContent, err := bfs.ReadRegular(sourcePath)
+	if err != nil {
 		return fmt.Errorf("source note: %w", err)
 	}
-	if _, err := os.Stat(tgtFull); err != nil {
+	tgtContent, err := bfs.ReadRegular(targetPath)
+	if err != nil {
 		return fmt.Errorf("target note: %w", err)
 	}
 
-	if err := appendSeeAlso(srcFull, wikilinkOf(targetPath)); err != nil {
+	if out, changed, err := withSeeAlso(srcContent, wikilinkOf(targetPath)); err != nil {
 		return fmt.Errorf("update source: %w", err)
+	} else if changed {
+		if err := bfs.WriteRegular(sourcePath, out); err != nil {
+			return fmt.Errorf("update source: %w", err)
+		}
 	}
-	if err := appendSeeAlso(tgtFull, wikilinkOf(sourcePath)); err != nil {
+	if out, changed, err := withSeeAlso(tgtContent, wikilinkOf(sourcePath)); err != nil {
 		return fmt.Errorf("update target: %w", err)
+	} else if changed {
+		if err := bfs.WriteRegular(targetPath, out); err != nil {
+			return fmt.Errorf("update target: %w", err)
+		}
+	}
+	return nil
+}
+
+// checkNotePath accepts only a clean, local wiki/<wing>/<hall>/.../<slug>.md
+// path: no "." or ".." segments, no empty segments, no leading slash.
+func checkNotePath(p string) error {
+	if p == "" || path.Clean(p) != p || !filepath.IsLocal(p) || !strings.HasSuffix(p, ".md") {
+		return fmt.Errorf("not a clean wiki note path: %q", p)
+	}
+	for _, part := range strings.Split(p, "/") {
+		if part == "" || part == "." || part == ".." {
+			return fmt.Errorf("not a clean wiki note path: %q", p)
+		}
 	}
 	return nil
 }
@@ -248,16 +287,13 @@ func wingOf(relPath string) (string, error) {
 	return parts[1], nil
 }
 
-// appendSeeAlso inserts `- [[link]]` under the file's See also section,
+// withSeeAlso returns content with `- [[link]]` under its See also section,
-// creating the section if absent. No-op when the link is already present.
+// creating the section if absent. changed is false when the link is already
-func appendSeeAlso(filePath, link string) error {
+// present.
-	content, err := os.ReadFile(filePath)
+func withSeeAlso(content []byte, link string) (out []byte, changed bool, err error) {
-	if err != nil {
-		return err
-	}
 	wikilink := "[[" + link + "]]"
 	if strings.Contains(string(content), wikilink) {
-		return nil
+		return content, false, nil
 	}
 
 	bullet := "- " + wikilink
@@ -266,8 +302,7 @@ func appendSeeAlso(filePath, link string) error {
 		// No section yet — append a fresh one. Always emit a trailing
 		// newline so subsequent appends don't merge into the previous line.
 		trimmed := strings.TrimRight(string(content), "\n")
-		out := trimmed + "\n\n" + seeAlsoHeader + "\n\n" + bullet + "\n"
+		return []byte(trimmed + "\n\n" + seeAlsoHeader + "\n\n" + bullet + "\n"), true, nil
-		return os.WriteFile(filePath, []byte(out), 0o644)
 	}
 
 	// Section exists — splice the bullet in just before the next `## `
@@ -293,12 +328,11 @@ func appendSeeAlso(filePath, link string) error {
 		b.WriteByte('\n')
 	}
 	if err := scanner.Err(); err != nil {
-		return err
+		return nil, false, err
 	}
 	if !inserted {
 		// section was the last thing in the file — just append bullet
-		out := strings.TrimRight(b.String(), "\n") + "\n" + bullet + "\n"
+		return []byte(strings.TrimRight(b.String(), "\n") + "\n" + bullet + "\n"), true, nil
-		return os.WriteFile(filePath, []byte(out), 0o644)
 	}
-	return os.WriteFile(filePath, []byte(b.String()), 0o644)
+	return []byte(b.String()), true, nil
 }

ingestion/internal/brain/tunnel_root_test.go

@@ -0,0 +1,141 @@
+package brain_test
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brain"
+)
+
+// brain_tunnel passes caller-supplied source and target paths to WriteTunnel,
+// which checked only "wiki/<wing>/..." and then joined them onto the brain
+// dir: ".." segments resolved outside the brain and appendSeeAlso rewrote the
+// file there.
+func TestWriteTunnelRefusesATargetThatTraversesOutOfTheBrain(t *testing.T) {
+	brain0 := t.TempDir()
+	src := filepath.Join(brain0, "wiki", "a", "facts", "s.md")
+	require.NoError(t, os.MkdirAll(filepath.Dir(src), 0o755))
+	require.NoError(t, os.WriteFile(src, []byte("---\ntitle: S\n---\nbody\n"), 0o644))
+	victim := filepath.Join(t.TempDir(), "victim.md")
+	require.NoError(t, os.WriteFile(victim, []byte("untouched\n"), 0o644))
+
+	up := strings.Repeat("../", strings.Count(filepath.Clean(brain0), "/")+3)
+	target := "wiki/b/x/" + up + strings.TrimPrefix(victim, "/")
+	err := brain.WriteTunnel(brain0, "wiki/a/facts/s.md", target)
+	assert.Error(t, err)
+	got, rerr := os.ReadFile(victim)
+	require.NoError(t, rerr)
+	assert.Equal(t, "untouched\n", string(got), "a file outside the brain was modified")
+}
+
+func TestWriteTunnelRefusesUncleanOrNonWikiPaths(t *testing.T) {
+	brain0 := t.TempDir()
+	for _, p := range []string{"wiki/a/facts/s.md", "wiki/b/facts/t.md", "wiki/b/facts/t.txt", "raw/r.md"} {
+		require.NoError(t, os.MkdirAll(filepath.Dir(filepath.Join(brain0, p)), 0o755))
+		require.NoError(t, os.WriteFile(filepath.Join(brain0, p), []byte("x\n"), 0o644))
+	}
+	for _, target := range []string{
+		"wiki/b/facts/../../../raw/r.md",
+		"wiki/b/./facts/t.md",
+		"wiki/b//facts/t.md",
+		"/wiki/b/facts/t.md",
+		"wiki/b/facts/t.txt",
+		"wiki/b/facts/",
+	} {
+		assert.Error(t, brain.WriteTunnel(brain0, "wiki/a/facts/s.md", target), target)
+	}
+	for _, p := range []string{"raw/r.md", "wiki/b/facts/t.txt"} {
+		got, err := os.ReadFile(filepath.Join(brain0, p))
+		require.NoError(t, err)
+		assert.Equal(t, "x\n", string(got), p)
+	}
+	require.NoError(t, brain.WriteTunnel(brain0, "wiki/a/facts/s.md", "wiki/b/facts/t.md"), "positive control")
+	got, err := os.ReadFile(filepath.Join(brain0, "wiki", "b", "facts", "t.md"))
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "[[a/facts/s]]")
+}
+
+func TestWriteTunnelDoesNotWriteThroughASymlinkedNote(t *testing.T) {
+	brain0 := t.TempDir()
+	src := filepath.Join(brain0, "wiki", "a", "facts", "s.md")
+	require.NoError(t, os.MkdirAll(filepath.Dir(src), 0o755))
+	require.NoError(t, os.WriteFile(src, []byte("x\n"), 0o644))
+	tdir := filepath.Join(brain0, "wiki", "b", "facts")
+	require.NoError(t, os.MkdirAll(tdir, 0o755))
+	victim := filepath.Join(t.TempDir(), "victim.md")
+	require.NoError(t, os.WriteFile(victim, []byte("untouched\n"), 0o644))
+	require.NoError(t, os.Symlink(victim, filepath.Join(tdir, "t.md")))
+	assert.Error(t, brain.WriteTunnel(brain0, "wiki/a/facts/s.md", "wiki/b/facts/t.md"))
+	got, err := os.ReadFile(victim)
+	require.NoError(t, err)
+	assert.Equal(t, "untouched\n", string(got))
+
+	// The same with a link to a file elsewhere in the brain, which os.Root
+	// would follow.
+	inVictim := filepath.Join(brain0, "raw", "v.md")
+	require.NoError(t, os.MkdirAll(filepath.Dir(inVictim), 0o755))
+	require.NoError(t, os.WriteFile(inVictim, []byte("untouched\n"), 0o644))
+	require.NoError(t, os.Symlink(filepath.Join("..", "..", "..", "raw", "v.md"), filepath.Join(tdir, "u.md")))
+	assert.Error(t, brain.WriteTunnel(brain0, "wiki/a/facts/s.md", "wiki/b/facts/u.md"))
+	got, err = os.ReadFile(inVictim)
+	require.NoError(t, err)
+	assert.Equal(t, "untouched\n", string(got))
+	got, err = os.ReadFile(src)
+	require.NoError(t, err)
+	assert.Equal(t, "x\n", string(got), "the source is not touched when the target is refused")
+}
+
+// The target is swapped between a regular note and a symlink to an in-brain
+// file outside wiki/ while WriteTunnel runs: the read and the write each
+// refuse a symlink, so the other file is never rewritten.
+func TestWriteTunnelNeverRewritesASymlinkSwappedInForTheTarget(t *testing.T) {
+	brain0 := t.TempDir()
+	src := filepath.Join(brain0, "wiki", "a", "facts", "s.md")
+	require.NoError(t, os.MkdirAll(filepath.Dir(src), 0o755))
+	require.NoError(t, os.WriteFile(src, []byte("x\n"), 0o644))
+	tdir := filepath.Join(brain0, "wiki", "b", "facts")
+	require.NoError(t, os.MkdirAll(tdir, 0o755))
+	victim := filepath.Join(brain0, "raw", "victim.md")
+	require.NoError(t, os.MkdirAll(filepath.Dir(victim), 0o755))
+	require.NoError(t, os.WriteFile(victim, []byte("untouched\n"), 0o644))
+	tgt := filepath.Join(tdir, "t.md")
+	require.NoError(t, os.WriteFile(tgt, []byte("t\n"), 0o644))
+
+	var stop atomic.Bool
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		tmp := tgt + ".swap"
+		for i := 0; !stop.Load(); i++ {
+			_ = os.Remove(tmp)
+			if i%2 == 0 {
+				_ = os.WriteFile(tmp, []byte("t\n"), 0o644)
+			} else {
+				_ = os.Symlink(filepath.Join("..", "..", "..", "raw", "victim.md"), tmp)
+			}
+			_ = os.Rename(tmp, tgt)
+		}
+	}()
+	ok := 0
+	for deadline := time.Now().Add(1500 * time.Millisecond); time.Now().Before(deadline); {
+		if brain.WriteTunnel(brain0, "wiki/a/facts/s.md", "wiki/b/facts/t.md") == nil {
+			ok++
+		}
+		_ = os.WriteFile(src, []byte("x\n"), 0o644)
+	}
+	stop.Store(true)
+	wg.Wait()
+	got, err := os.ReadFile(victim)
+	require.NoError(t, err)
+	assert.Equal(t, "untouched\n", string(got), "the swapped-in symlink's target was rewritten")
+	assert.Positive(t, ok, "positive control: some tunnels were written to the regular target")
+}

ingestion/internal/brainfs/brainfs.go

@@ -0,0 +1,239 @@
+// Package brainfs reads the brain directory through an os.Root (hyperguild#157).
+// The brain dir is a Syncthing sendreceive folder and Syncthing syncs
+// symlinks; a reader that walks and reads by path follows a planted symlink
+// out of the brain, and blocks forever on a planted FIFO. Readers that go
+// through a Brain only ever read regular files inside the brain: os.Root
+// refuses to leave the root even if an entry is swapped mid-read, and every
+// open is non-blocking with the type checked on the opened handle.
+package brainfs
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+	"syscall"
+)
+
+// ErrNotRegular is returned for an entry that is not a regular file.
+var ErrNotRegular = errors.New("not a regular file")
+
+// ErrTooLarge is returned by ReadRegularMax for a file over the limit.
+var ErrTooLarge = errors.New("file too large")
+
+// Brain is an open brain directory.
+type Brain struct {
+	root *os.Root
+	dir  string
+}
+
+// Open opens brainDir (which may itself be a mount symlink) as a root.
+func Open(brainDir string) (*Brain, error) {
+	r, err := os.OpenRoot(brainDir)
+	if err != nil {
+		return nil, fmt.Errorf("open brain root: %w", err)
+	}
+	return &Brain{root: r, dir: brainDir}, nil
+}
+
+// Close releases the root.
+func (b *Brain) Close() error { return b.root.Close() }
+
+// Rel converts a path under the brain dir to a root-relative path.
+func (b *Brain) Rel(path string) (string, error) {
+	rel, err := filepath.Rel(b.dir, path)
+	if err != nil {
+		return "", err
+	}
+	if rel == ".." || len(rel) > 2 && rel[:3] == ".."+string(filepath.Separator) {
+		return "", fmt.Errorf("%s is outside the brain dir", path)
+	}
+	return filepath.ToSlash(rel), nil
+}
+
+// Lstat stats a brain-relative path through the root without following a
+// final symlink.
+func (b *Brain) Lstat(rel string) (fs.FileInfo, error) {
+	return b.root.Lstat(filepath.ToSlash(rel))
+}
+
+// realDir returns ErrNotRegular unless every component of rel is a real
+// directory. A swap after the check is not caught (accepted residual,
+// hyperguild#157).
+func (b *Brain) realDir(rel string) error {
+	if rel == "." {
+		return nil
+	}
+	prefix := ""
+	for _, part := range strings.Split(rel, "/") {
+		prefix = path.Join(prefix, part)
+		fi, err := b.root.Lstat(prefix)
+		if err != nil {
+			return err
+		}
+		if !fi.IsDir() {
+			return fmt.Errorf("%s: walk root component %s is not a directory: %w", rel, prefix, ErrNotRegular)
+		}
+	}
+	return nil
+}
+
+// WriteRegular replaces the contents of an existing regular file at a
+// brain-relative path. It never creates a file and never writes through a
+// final symlink: os.Root.OpenFile follows an in-root final symlink even with
+// O_NOFOLLOW (verified on go1.27), so the path is Lstat-ed through the root
+// first and the opened handle must be that same file (os.SameFile), which
+// also catches a swap between the two. O_NONBLOCK keeps a FIFO from blocking
+// the open. Intermediate in-brain symlinks are still followed (os.Root keeps
+// the write inside the brain; hyperguild#167).
+func (b *Brain) WriteRegular(rel string, data []byte) error {
+	rel = filepath.ToSlash(rel)
+	lfi, err := b.root.Lstat(rel)
+	if err != nil {
+		return err
+	}
+	if !lfi.Mode().IsRegular() {
+		return fmt.Errorf("%s: %w", rel, ErrNotRegular)
+	}
+	f, err := b.root.OpenFile(rel, os.O_WRONLY|syscall.O_NOFOLLOW|syscall.O_NONBLOCK, 0)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = f.Close() }()
+	fi, err := f.Stat()
+	if err != nil {
+		return err
+	}
+	if !fi.Mode().IsRegular() || !os.SameFile(lfi, fi) {
+		return fmt.Errorf("%s: changed while opening: %w", rel, ErrNotRegular)
+	}
+	if err := f.Truncate(0); err != nil {
+		return err
+	}
+	if _, err := f.Write(data); err != nil {
+		return err
+	}
+	return f.Close()
+}
+
+// ReadRegular reads a brain-relative path, refusing anything that is not a
+// regular file, both before the open and on the opened handle.
+func (b *Brain) ReadRegular(rel string) ([]byte, error) {
+	fi, err := b.root.Lstat(rel)
+	if err != nil {
+		return nil, err
+	}
+	if !fi.Mode().IsRegular() {
+		return nil, fmt.Errorf("%s: %w", rel, ErrNotRegular)
+	}
+	return b.readOpened(rel)
+}
+
+// readOpened opens rel non-blocking and reads it only if the OPENED handle is
+// a regular file. This is the check that matters under a race: an entry
+// swapped for a FIFO after the Lstat, with a writer holding it open, would
+// otherwise park io.ReadAll forever (PR #161 review: removing it hung search
+// after 16 iterations).
+//
+// Accepted residual, as in api/rawroot.go: a HARD link to an outside file is
+// a regular file and is read. Syncthing syncs contents, not links, so a peer
+// cannot create one; fs.protected_hardlinks=1 and the pod's secrets are on a
+// different filesystem from the brain volume, so a local caller cannot link
+// them in. Refusing Nlink > 1 is the next step if either changes.
+func (b *Brain) readOpened(rel string) ([]byte, error) { return b.readOpenedMax(rel, -1) }
+
+// ReadRegularMax is ReadRegular with a size limit, checked on the opened
+// handle before reading (max < 0 means no limit).
+func (b *Brain) ReadRegularMax(rel string, max int64) ([]byte, error) {
+	fi, err := b.root.Lstat(rel)
+	if err != nil {
+		return nil, err
+	}
+	if !fi.Mode().IsRegular() {
+		return nil, fmt.Errorf("%s: %w", rel, ErrNotRegular)
+	}
+	return b.readOpenedMax(rel, max)
+}
+
+func (b *Brain) readOpenedMax(rel string, max int64) ([]byte, error) {
+	f, err := b.root.OpenFile(rel, os.O_RDONLY|syscall.O_NONBLOCK, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer func() { _ = f.Close() }()
+	hfi, err := f.Stat()
+	if err != nil {
+		return nil, err
+	}
+	if !hfi.Mode().IsRegular() {
+		return nil, fmt.Errorf("%s: %w", rel, ErrNotRegular)
+	}
+	if max >= 0 && hfi.Size() > max {
+		return nil, fmt.Errorf("%s is %d bytes (limit %d): %w", rel, hfi.Size(), max, ErrTooLarge)
+	}
+	var r io.Reader = f
+	if wrapAfterStat != nil {
+		r = wrapAfterStat(r)
+	}
+	if max < 0 {
+		return io.ReadAll(r)
+	}
+	// The handle's size can grow after the check; bound the read itself.
+	data, err := io.ReadAll(io.LimitReader(r, max+1))
+	if err != nil {
+		return nil, err
+	}
+	if int64(len(data)) > max {
+		return nil, fmt.Errorf("%s grew past %d bytes while read: %w", rel, max, ErrTooLarge)
+	}
+	return data, nil
+}
+
+// wrapAfterStat is a test seam: it runs between the size check and the read,
+// and wraps the reader the read consumes. A package global: brainfs tests
+// must not use t.Parallel.
+var wrapAfterStat func(io.Reader) io.Reader
+
+// WalkRegular walks a brain-relative directory through the root and calls fn
+// for each regular file. Directories are descended; symlinks, FIFOs and
+// devices found by the walk are skipped. A walk root with any component that
+// is not a real directory goes to onErr as ErrNotRegular and nothing is
+// yielded. An entry error is passed to onErr and the walk continues; a nil
+// onErr ignores it.
+//
+// Accepted residual (hyperguild#157): a directory swapped for a symlink
+// between the listing and the read is followed. os.Root still keeps the read
+// inside the brain, but not inside relDir.
+func (b *Brain) WalkRegular(relDir string, fn func(rel string) error, onErr func(rel string, err error)) error {
+	relDir = filepath.ToSlash(relDir)
+	// fs.WalkDir stats its root with a follow, and os.Root allows a symlink
+	// that stays inside the brain: knowledge -> . would alias the whole
+	// brain. Require every component of the root to be a real directory
+	// (Lstat checks only the last one).
+	err := b.realDir(relDir)
+	if err != nil {
+		if onErr != nil {
+			onErr(relDir, err)
+		}
+		return nil
+	}
+	return fs.WalkDir(b.root.FS(), relDir, func(p string, d fs.DirEntry, err error) error {
+		if err != nil {
+			if onErr != nil {
+				onErr(p, err)
+			}
+			if d != nil && d.IsDir() {
+				return fs.SkipDir
+			}
+			return nil
+		}
+		if d.IsDir() || !d.Type().IsRegular() {
+			return nil
+		}
+		return fn(p)
+	})
+}

ingestion/internal/brainfs/brainfs_test.go

@@ -0,0 +1,237 @@
+package brainfs
+
+import (
+	"errors"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"syscall"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// The handle check is what stops a FIFO swapped in after the Lstat. A FIFO
+// with no writer reads EOF at once, so a race test could not see the check
+// missing; here a writer holds the FIFO open, as any local process can, and
+// readOpened must refuse it promptly (PR #161 review).
+func TestReadOpenedRefusesAFIFOHeldOpenByAWriter(t *testing.T) {
+	dir := t.TempDir()
+	fifo := filepath.Join(dir, "p.md")
+	require.NoError(t, syscall.Mkfifo(fifo, 0o644))
+	w, err := os.OpenFile(fifo, os.O_RDWR, 0)
+	require.NoError(t, err)
+	defer func() { _ = w.Close() }()
+
+	b, err := Open(dir)
+	require.NoError(t, err)
+	defer func() { _ = b.Close() }()
+
+	done := make(chan error, 1)
+	go func() { _, err := b.readOpened("p.md"); done <- err }()
+	select {
+	case err := <-done:
+		assert.True(t, errors.Is(err, ErrNotRegular), "got %v", err)
+	case <-time.After(2 * time.Second):
+		t.Fatal("readOpened blocked on a FIFO with a writer")
+	}
+}
+
+func TestReadRegularRefusesSymlinksAndReadsRegularFiles(t *testing.T) {
+	dir := t.TempDir()
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "ok.md"), []byte("ok"), 0o644))
+	outside := filepath.Join(t.TempDir(), "s.md")
+	require.NoError(t, os.WriteFile(outside, []byte("secret"), 0o644))
+	require.NoError(t, os.Symlink(outside, filepath.Join(dir, "link.md")))
+	b, err := Open(dir)
+	require.NoError(t, err)
+	defer func() { _ = b.Close() }()
+	got, err := b.ReadRegular("ok.md")
+	require.NoError(t, err)
+	assert.Equal(t, "ok", string(got))
+	_, err = b.ReadRegular("link.md")
+	assert.True(t, errors.Is(err, ErrNotRegular), "got %v", err)
+	_, err = b.ReadRegular("../" + filepath.Base(outside))
+	assert.Error(t, err)
+}
+
+func TestRelAcceptsPathsInsideAndRefusesEscapes(t *testing.T) {
+	dir := t.TempDir()
+	b, err := Open(dir)
+	require.NoError(t, err)
+	defer func() { _ = b.Close() }()
+	for in, want := range map[string]string{
+		filepath.Join(dir, "wiki", "x.md"): "wiki/x.md",
+		filepath.Join(dir, "..foo", "x"):   "..foo/x",
+		dir:                                ".",
+	} {
+		got, err := b.Rel(in)
+		require.NoError(t, err, in)
+		assert.Equal(t, want, got, in)
+	}
+	for _, bad := range []string{filepath.Join(dir, "..", "x"), dir + "-evil/x", "/etc/passwd", filepath.Join(dir, "wiki", "..", "..", "x")} {
+		_, err := b.Rel(bad)
+		assert.Error(t, err, bad)
+	}
+}
+
+func TestWalkRegularYieldsOnlyRegularFiles(t *testing.T) {
+	dir := t.TempDir()
+	require.NoError(t, os.MkdirAll(filepath.Join(dir, "a"), 0o755))
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "a", "n.md"), []byte("n"), 0o644))
+	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(dir, "a", "dirlink")))
+	require.NoError(t, os.Symlink(filepath.Join(dir, "a", "n.md"), filepath.Join(dir, "a", "filelink.md")))
+	require.NoError(t, syscall.Mkfifo(filepath.Join(dir, "a", "p.md"), 0o644))
+	b, err := Open(dir)
+	require.NoError(t, err)
+	defer func() { _ = b.Close() }()
+	var got []string
+	require.NoError(t, b.WalkRegular(".", func(rel string) error { got = append(got, rel); return nil }, nil))
+	assert.Equal(t, []string{"a/n.md"}, got)
+}
+
+func TestReadRegularMaxRefusesAFileOverTheLimit(t *testing.T) {
+	dir := t.TempDir()
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "big.md"), make([]byte, 100), 0o644))
+	b, err := Open(dir)
+	require.NoError(t, err)
+	defer func() { _ = b.Close() }()
+	_, err = b.ReadRegularMax("big.md", 99)
+	assert.True(t, errors.Is(err, ErrTooLarge), "got %v", err)
+	got, err := b.ReadRegularMax("big.md", 100)
+	require.NoError(t, err)
+	assert.Len(t, got, 100)
+}
+
+func TestReadRegularMaxRefusesAndStopsReadingAFileThatGrowsPastTheLimit(t *testing.T) {
+	dir := t.TempDir()
+	p := filepath.Join(dir, "grow.md")
+	require.NoError(t, os.WriteFile(p, make([]byte, 10), 0o644))
+	consumed := &countingReader{}
+	wrapAfterStat = func(r io.Reader) io.Reader {
+		f, err := os.OpenFile(p, os.O_WRONLY|os.O_APPEND, 0)
+		require.NoError(t, err)
+		_, err = f.Write(make([]byte, 1000))
+		require.NoError(t, err)
+		require.NoError(t, f.Close())
+		consumed.r = r
+		return consumed
+	}
+	t.Cleanup(func() { wrapAfterStat = nil })
+	b, err := Open(dir)
+	require.NoError(t, err)
+	defer func() { _ = b.Close() }()
+	got, err := b.ReadRegularMax("grow.md", 100)
+	assert.True(t, errors.Is(err, ErrTooLarge), "got %v", err)
+	assert.Nil(t, got)
+	assert.LessOrEqual(t, consumed.n, 101, "read past max+1 bytes")
+}
+
+type countingReader struct {
+	r io.Reader
+	n int
+}
+
+func (c *countingReader) Read(p []byte) (int, error) {
+	n, err := c.r.Read(p)
+	c.n += n
+	return n, err
+}
+
+func TestLstatDoesNotFollowSymlinksAndRefusesEscapes(t *testing.T) {
+	dir := t.TempDir()
+	outside := filepath.Join(t.TempDir(), "o.md")
+	require.NoError(t, os.WriteFile(outside, []byte("o"), 0o644))
+	require.NoError(t, os.Symlink(outside, filepath.Join(dir, "l.md")))
+	b, err := Open(dir)
+	require.NoError(t, err)
+	defer func() { _ = b.Close() }()
+	fi, err := b.Lstat("l.md")
+	require.NoError(t, err)
+	assert.Equal(t, fs.ModeSymlink, fi.Mode().Type())
+	_, err = b.Lstat("../" + filepath.Base(filepath.Dir(outside)) + "/o.md")
+	assert.Error(t, err)
+}
+
+func TestWalkRegularReportsASymlinkedWalkRootAndYieldsNothing(t *testing.T) {
+	dir := t.TempDir()
+	require.NoError(t, os.MkdirAll(filepath.Join(dir, "real"), 0o755))
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "real", "n.md"), []byte("n"), 0o644))
+	require.NoError(t, os.Symlink("real", filepath.Join(dir, "alias")))
+	b, err := Open(dir)
+	require.NoError(t, err)
+	defer func() { _ = b.Close() }()
+	var got []string
+	var errs []error
+	require.NoError(t, b.WalkRegular("alias", func(rel string) error { got = append(got, rel); return nil },
+		func(_ string, err error) { errs = append(errs, err) }))
+	assert.Empty(t, got)
+	require.Len(t, errs, 1)
+	assert.ErrorIs(t, errs[0], ErrNotRegular)
+}
+
+func TestWalkRegularReportsASymlinkedIntermediateComponentOfTheWalkRoot(t *testing.T) {
+	dir := t.TempDir()
+	require.NoError(t, os.MkdirAll(filepath.Join(dir, "real", "sub"), 0o755))
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "real", "sub", "n.md"), []byte("n"), 0o644))
+	require.NoError(t, os.Symlink("real", filepath.Join(dir, "alias")))
+	b, err := Open(dir)
+	require.NoError(t, err)
+	defer func() { _ = b.Close() }()
+	var got []string
+	var errs []error
+	require.NoError(t, b.WalkRegular("alias/sub", func(rel string) error { got = append(got, rel); return nil },
+		func(_ string, err error) { errs = append(errs, err) }))
+	assert.Empty(t, got)
+	require.Len(t, errs, 1)
+	assert.ErrorIs(t, errs[0], ErrNotRegular)
+}
+
+func TestWriteRegularRefusesFinalSymlinksFIFOsEscapesAndMissingFilesAndRewritesRegularFiles(t *testing.T) {
+	dir := t.TempDir()
+	outside := filepath.Join(t.TempDir(), "o.md")
+	require.NoError(t, os.WriteFile(outside, []byte("untouched"), 0o644))
+	require.NoError(t, os.Symlink(outside, filepath.Join(dir, "l.md")))
+	require.NoError(t, syscall.Mkfifo(filepath.Join(dir, "f.md"), 0o644))
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "n.md"), []byte("old content"), 0o644))
+	b, err := Open(dir)
+	require.NoError(t, err)
+	defer func() { _ = b.Close() }()
+
+	assert.Error(t, b.WriteRegular("l.md", []byte("x")))
+	got, _ := os.ReadFile(outside)
+	assert.Equal(t, "untouched", string(got))
+
+	// A symlink to another file inside the brain: os.Root would allow it,
+	// only O_NOFOLLOW refuses it.
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "in.md"), []byte("inside"), 0o644))
+	require.NoError(t, os.Symlink("in.md", filepath.Join(dir, "il.md")))
+	assert.Error(t, b.WriteRegular("il.md", []byte("x")))
+	got, _ = os.ReadFile(filepath.Join(dir, "in.md"))
+	assert.Equal(t, "inside", string(got))
+
+	// A reader held open, so a non-blocking write open would succeed. The
+	// Lstat type check refuses the FIFO first; the handle check and
+	// O_NONBLOCK matter only if it is swapped in after the Lstat.
+	r, err := os.OpenFile(filepath.Join(dir, "f.md"), os.O_RDONLY|syscall.O_NONBLOCK, 0)
+	require.NoError(t, err)
+	defer func() { _ = r.Close() }()
+	done := make(chan error, 1)
+	go func() { done <- b.WriteRegular("f.md", []byte("x")) }()
+	select {
+	case err := <-done:
+		assert.Error(t, err)
+	case <-time.After(3 * time.Second):
+		t.Fatal("WriteRegular hung on a FIFO")
+	}
+
+	assert.Error(t, b.WriteRegular("../"+filepath.Base(filepath.Dir(outside))+"/o.md", []byte("x")))
+	assert.Error(t, b.WriteRegular("missing.md", []byte("x")), "does not create files")
+
+	require.NoError(t, b.WriteRegular("n.md", []byte("new")))
+	got, _ = os.ReadFile(filepath.Join(dir, "n.md"))
+	assert.Equal(t, "new", string(got), "truncated and rewritten")
+}

ingestion/internal/brainfs/brainfstest/brainfstest.go

@@ -0,0 +1,103 @@
+// Package brainfstest is the shared harness for hyperguild#157's swap-race
+// tests: it keeps swapping a regular note, a symlink to an outside file, or a
+// FIFO (with a writer held open) into a path while a reader under test loops.
+// It observes two things: no sentinel byte from the outside file reaches the
+// reader's output, and the reader returns within a timeout. It does not cover
+// hard links, other paths into the reader, or races it does not generate.
+package brainfstest
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"syscall"
+	"testing"
+	"time"
+)
+
+// Sentinel marks the outside file's contents.
+const Sentinel = "zqbrainfssentinelonefiftyseven"
+
+// Outside writes a file outside any brain dir containing Sentinel.
+func Outside(t *testing.T) string {
+	t.Helper()
+	p := filepath.Join(t.TempDir(), "secret.md")
+	if err := os.WriteFile(p, []byte("# secret\n\n"+Sentinel), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	return p
+}
+
+// StartSwap renames, in a loop, a regular note (content inside) and either
+// a symlink to outside or a FIFO into path, until the test ends. FIFOs get a
+// writer held open until the swapper exits, so a reader that skips the
+// handle check parks forever instead of reading EOF. The swapper is stopped
+// and awaited before t.TempDir cleanup.
+func StartSwap(t *testing.T, path, inside, outside string, fifo bool) {
+	t.Helper()
+	var stop atomic.Bool
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		tmp := path + ".swap"
+		var writers []*os.File
+		defer func() {
+			for _, w := range writers {
+				_ = w.Close()
+			}
+		}()
+		for i := 0; !stop.Load(); i++ {
+			_ = os.Remove(tmp)
+			switch {
+			case i%2 == 0:
+				_ = os.WriteFile(tmp, []byte(inside), 0o644)
+			case fifo:
+				if err := syscall.Mkfifo(tmp, 0o644); err == nil {
+					if w, err := os.OpenFile(tmp, os.O_RDWR, 0); err == nil {
+						writers = append(writers, w)
+					}
+				}
+			default:
+				_ = os.Symlink(outside, tmp)
+			}
+			_ = os.Rename(tmp, path)
+		}
+	}()
+	t.Cleanup(func() { stop.Store(true); wg.Wait() })
+}
+
+// AssertNoLeak loops read for d while a symlink swapper runs on path, and
+// fails if any output contains Sentinel.
+func AssertNoLeak(t *testing.T, path, inside string, d time.Duration, read func() string) {
+	t.Helper()
+	StartSwap(t, path, inside, Outside(t), false)
+	leaks, iters := 0, 0
+	for deadline := time.Now().Add(d); time.Now().Before(deadline); iters++ {
+		leaks += strings.Count(read(), Sentinel)
+	}
+	if leaks > 0 {
+		t.Fatalf("outside file leaked %d times in %d iterations", leaks, iters)
+	}
+}
+
+// AssertNoHang loops read for d while a FIFO swapper (held writers) runs on
+// path, and fails if a read does not return within timeout.
+func AssertNoHang(t *testing.T, path, inside string, d, timeout time.Duration, read func()) {
+	t.Helper()
+	StartSwap(t, path, inside, Outside(t), true)
+	done := make(chan struct{})
+	go func() {
+		for deadline := time.Now().Add(d); time.Now().Before(deadline); {
+			read()
+		}
+		close(done)
+	}()
+	select {
+	case <-done:
+	case <-time.After(timeout):
+		t.Fatal("reader hung on a swapped-in FIFO with a writer held open")
+	}
+}

ingestion/internal/brainstore/store.go

@@ -49,10 +49,12 @@ func (s *Store) Write(ctx context.Context, n capture.Note) (capture.Ref, error)
 	n.Content = content
 
 	relPath, err := api.WriteNote(s.brainDir, api.WriteNoteOptions{
-		Content:  n.Content,
+		Content:   n.Content,
-		Filename: n.Filename,
+		Filename:  n.Filename,
-		Wing:     n.Wing,
+		Wing:      n.Wing,
-		Hall:     n.Hall,
+		Hall:      n.Hall,
+		Origin:    n.Origin,
+		WrittenBy: n.WrittenBy,
 	})
 	if err != nil {
 		return capture.Ref{}, err
@@ -74,7 +76,7 @@ func (s *Store) Update(ctx context.Context, slug string, n capture.Note) (captur
 	}
 	n.Content = content
 
-	opts := api.UpdateNoteOptions{Content: n.Content, Reason: n.Reason}
+	opts := api.UpdateNoteOptions{Content: n.Content, Reason: n.Reason, Origin: n.Origin, WrittenBy: n.WrittenBy}
 	if strings.Contains(slug, "/") {
 		opts.Path = slug
 	} else {

ingestion/internal/capture/entities.go

@@ -60,6 +60,7 @@ type CaptureContext struct {
 	Classification string // caller-declared level token ("" = unspecified)
 	Principal      string // server-derived (auth); audit identity
 	Origin         Zone   // server-derived trust zone; the I1 gate input
+	AuthPath       string // server-derived: "static" or "jwt"; stamped as note provenance (#145)
 }
 
 // Insight is one piece of session knowledge bound for the brain. A

ingestion/internal/capture/ports.go

@@ -40,6 +40,11 @@ type Note struct {
 	Wing     string
 	Hall     string
 	Reason   string
+	// Provenance (hyperguild#145) is stamped by the server from the
+	// authenticated principal, never taken from Content's frontmatter.
+	// Origin is "static", "jwt" or "unknown"; empty means "unknown".
+	Origin    string
+	WrittenBy string
 }
 
 // BrainStore is the brain persistence port — the shared implementation of

ingestion/internal/capture/service.go

@@ -142,7 +142,7 @@ func (s *Service) Capture(ctx context.Context, in CaptureInput) (CaptureReceipt,
 	var landed []string
 
 	for i, ins := range in.Insights {
-		res, item, err := s.persistInsight(ctx, ins)
+		res, item, err := s.persistInsight(ctx, ins, in.Context)
 		receipt.Insights = append(receipt.Insights, res)
 		if err != nil {
 			receipt.Errors = append(receipt.Errors, ItemError{Item: fmt.Sprintf("insight[%d]", i), Error: err.Error()})
@@ -278,8 +278,11 @@ func escalationReason(escalators []string) string {
 	return "required by: " + strings.Join(escalators, ", ")
 }
 
-func (s *Service) persistInsight(ctx context.Context, ins Insight) (InsightResult, string, error) {
+func (s *Service) persistInsight(ctx context.Context, ins Insight, cc CaptureContext) (InsightResult, string, error) {
-	note := Note{Content: ins.Text, Wing: ins.Wing, Hall: ins.Hall, Filename: brain.Sanitise(firstLine(ins.Text))}
+	note := Note{
+		Content: ins.Text, Wing: ins.Wing, Hall: ins.Hall, Filename: brain.Sanitise(firstLine(ins.Text)),
+		Origin: cc.AuthPath, WrittenBy: cc.Principal,
+	}
 	var ref Ref
 	var err error
 	if ins.SupersedeSlug != "" {

ingestion/internal/capturehttp/handler.go

@@ -104,6 +104,10 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	// caller may have tried to put in the body.
 	in.Context.Principal = principal
 	in.Context.Origin = h.resolver.Resolve(principal, viaStatic)
+	in.Context.AuthPath = "jwt"
+	if viaStatic {
+		in.Context.AuthPath = "static"
+	}
 
 	rec, err := h.svc.Capture(r.Context(), in)
 	switch {

ingestion/internal/capturehttp/provenance_test.go

@@ -0,0 +1,51 @@
+package capturehttp_test
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/audit"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brainstore"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/capture"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/capturehttp"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/classification"
+)
+
+// The REST capture door derives AuthPath itself (hyperguild#145); a body
+// field cannot set it, and static vs JWT are told apart.
+func TestRESTCaptureStampsAuthPathFromAuthentication(t *testing.T) {
+	for _, tc := range []struct {
+		name, authz, wantOrigin, wantBy string
+		v                               capturehttp.Validator
+		sovereign                       []string
+	}{
+		{"static", "Bearer " + staticTok, "origin: static\n", "written_by: local-cli\n", nil, nil},
+		{"jwt", "Bearer jwt", "origin: jwt\n", "written_by: koala-cli\n", fakeValidator{subject: "koala-cli"}, []string{"koala-cli"}},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			brainDir := t.TempDir()
+			cfg, err := classification.Load(t.TempDir())
+			require.NoError(t, err)
+			svc := capture.NewService(brainstore.New(brainDir), fakeTracker{}, cfg, audit.NewSlogSink(nil))
+			h := capturehttp.New(svc, tc.v, staticTok, "local-cli", capturehttp.NewOriginResolver(tc.sovereign))
+			rr := do(t, h, tc.authz, map[string]any{
+				"context": map[string]any{
+					"harness": "claude-code", "actor": "mathias", "classification": "internal",
+					"AuthPath": "static", "auth_path": "static", "principal": "local-cli",
+				},
+				"insights": []map[string]any{{"text": "rest provenance probe", "wing": "hyperguild", "hall": "facts"}},
+			})
+			require.Equal(t, 200, rr.Code, rr.Body.String())
+			matches, _ := filepath.Glob(filepath.Join(brainDir, "wiki/hyperguild/facts/*.md"))
+			require.Len(t, matches, 1)
+			b, err := os.ReadFile(matches[0])
+			require.NoError(t, err)
+			assert.Contains(t, string(b), tc.wantOrigin)
+			assert.Contains(t, string(b), tc.wantBy)
+		})
+	}
+}

ingestion/internal/claudewatcher/scrubber.go

@@ -43,6 +43,26 @@ var DefaultRules = []Rule{
 	// JSON, so both segments begin with "eyJ".
 	{Name: "jwt", RE: regexp.MustCompile(`eyJ[A-Za-z0-9_\-]{8,}\.eyJ[A-Za-z0-9_\-]{8,}\.[A-Za-z0-9_\-]{8,}`)},
 	{Name: "postgres-uri-with-password", RE: regexp.MustCompile(`postgres(?:ql)?://[^:\s/]+:[^@\s/]+@`)},
+	// Any credential embedded in a URL's userinfo, which is what a git credential
+	// store holds: `https://<user>:<token>@host`. The postgres rule above is the
+	// same shape narrowed to one scheme, and is kept ahead of this one only so a
+	// DSN reports the more specific name -- same ordering convention as
+	// authorization-header before bearer-token.
+	//
+	// Added after this shape passed ALL rules and was therefore ingested rather
+	// than dropped (hyperguild#142). It reached ~/.claude/projects -- this
+	// watcher's own input -- because a test suite in mathias/infra executed a
+	// script that configures git while inheriting the operator's real $HOME, read
+	// koala's live credential store, and printed it. Two credentials were rotated
+	// (infra#466). The scrubber is the control that decides whether that class of
+	// mistake is survivable, and for this shape it was failing open.
+	//
+	// The {8,} floor on the secret half is what keeps `https://host:443/path` and
+	// `https://user:@host` out; the `[^:\s/@]+` user half stops a host:port pair
+	// being read as userinfo. Both directions are covered by
+	// TestScrub_URLUserinfoCredential, because a rule that dropped every URL with
+	// a colon in it would discard most of the signal this watcher exists to keep.
+	{Name: "url-userinfo-credential", RE: regexp.MustCompile(`[a-zA-Z][a-zA-Z0-9+.\-]*://[^:\s/@]+:[^@\s/]{8,}@`)},
 	{Name: "private-key", RE: regexp.MustCompile(`-----BEGIN[^-]*PRIVATE KEY-----`)},
 	{Name: "ssh-key", RE: regexp.MustCompile(`ssh-(?:rsa|ed25519|ecdsa)\s+[A-Za-z0-9+/=]{40,}`)},
 	{Name: "github-pat", RE: regexp.MustCompile(`\b(?:ghp|gho|ghu|ghr|gha)_[A-Za-z0-9]{30,}\b`)},

ingestion/internal/claudewatcher/scrubber_test.go

@@ -46,6 +46,64 @@ func TestScrub_PoisonedFixtures(t *testing.T) {
 	}
 }
 
+// A credential embedded in a URL's userinfo is the shape a git credential store
+// holds -- `https://<user>:<token>@host` -- and it walked past every rule until
+// hyperguild#142. There was a rule for `postgres://user:pass@` and nothing for the
+// general form, so `~/.git-credentials` content was ingested rather than dropped.
+//
+// Found the hard way: a test suite in mathias/infra executed a script that
+// configures git while inheriting the operator's real $HOME, read koala's live
+// credential store, and printed two live credentials into a session transcript.
+// ~/.claude/projects is this watcher's own input, so the scrubber was the last
+// line of defence for that mistake and it failed open. Two credentials were
+// rotated (infra#466).
+//
+// The lesson is not "do not read the credential file" -- that mistake will recur.
+// It is that this shape must fail closed, because the scrubber is what decides
+// whether such a mistake is survivable.
+func TestScrub_URLUserinfoCredential(t *testing.T) {
+	// Every secret below is INVENTED. None is or was a real credential.
+	mustScrub := []struct {
+		name    string
+		content string
+	}{
+		{"git-credential-store-user", "https://mathias:0123456789abcdef0123456789abcdef01234567@git.d-ma.be"},
+		{"git-credential-store-oauth2", "https://oauth2:0123456789abcdef0123456789abcdef01234567@git.d-ma.be"},
+		{"in-context-payload-line", `payload line: https://mathias:0123456789abcdef0123456789abcdef01234567@git.d-ma.be`},
+		{"clone-url-in-argv", "git clone https://oauth2:abcdefghijklmnopqrstuvwx@git.d-ma.be/mathias/infra.git"},
+		{"http-not-https", "http://admin:supersecretvalue123@10.0.1.20/api"},
+		{"git-plus-ssh-scheme", "git+ssh://deploy:abcdefghijklmnop@example.com/repo"},
+		{"redis-scheme", "redis://default:abcdefghijklmnopqrst@10.0.1.20:6379/0"},
+	}
+	for _, tc := range mustScrub {
+		t.Run(tc.name, func(t *testing.T) {
+			assert.NotEmpty(t, Scrub(tc.content),
+				"a credential in URL userinfo must be dropped, not ingested")
+		})
+	}
+
+	// The other direction matters as much: a rule that scrubs every URL with a
+	// colon in it would drop most of the signal this watcher exists to keep.
+	mustNotScrub := []struct {
+		name    string
+		content string
+	}{
+		{"host-with-port", "cloning https://git.d-ma.be:443/mathias/infra.git"},
+		{"postgres-no-password", "postgres://localhost:5432/brain"},
+		{"url-with-colon-in-query", "GET https://example.com/path?filter=a:b&x=1"},
+		{"plain-url", "see https://git.d-ma.be/mathias/infra/issues/466"},
+		{"userinfo-no-secret", "https://user:@example.com"},
+		{"format-string-placeholder", `printf 'https://oauth2:%s@%s\n' "$TOKEN" "$HOST"`},
+		{"scheme-relative-time", "duration https://example.com took 00:03:22"},
+	}
+	for _, tc := range mustNotScrub {
+		t.Run(tc.name, func(t *testing.T) {
+			assert.Empty(t, Scrub(tc.content),
+				"this is not a credential and must pass through")
+		})
+	}
+}
+
 func TestScrub_CleanContentPassesThrough(t *testing.T) {
 	cases := []string{
 		"",

ingestion/internal/extract/callsites_test.go

@@ -0,0 +1,130 @@
+package extract
+
+import (
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+const extractPkg = "github.com/mathiasbq/hyperguild/ingestion/internal/extract"
+
+// parseNonTest parses every non-test Go file under the module.
+func parseNonTest(t *testing.T) map[string]*ast.File {
+	t.Helper()
+	fset := token.NewFileSet()
+	out := map[string]*ast.File{}
+	err := filepath.WalkDir(filepath.Join("..", ".."), func(p string, d os.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() && (d.Name() == "vendor" || d.Name() == ".git") {
+			return filepath.SkipDir
+		}
+		if d.IsDir() || !strings.HasSuffix(p, ".go") || strings.HasSuffix(p, "_test.go") {
+			return nil
+		}
+		f, perr := parser.ParseFile(fset, p, nil, 0)
+		if perr != nil {
+			return perr
+		}
+		out[filepath.ToSlash(p)] = f
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	return out
+}
+
+// PR #156 review: reading a caller-chosen path by name reopens it after the
+// containment check (hyperguild#153 item 3). Outside this package, nothing
+// may reference extract.Text — called OR taken as a value — under whatever
+// name the package is imported (round 2: an alias and a func value slipped
+// past a plain text search).
+func TestNoPackageReferencesExtractTextOutsideExtract(t *testing.T) {
+	for path, f := range parseNonTest(t) {
+		if strings.Contains(path, "internal/extract/") {
+			continue
+		}
+		names := map[string]bool{}
+		for _, imp := range f.Imports {
+			if p, _ := strconv.Unquote(imp.Path.Value); p == extractPkg {
+				name := "extract"
+				if imp.Name != nil {
+					name = imp.Name.Name
+				}
+				if name == "." {
+					t.Errorf("%s dot-imports extract; import it by name so its use stays checkable", path)
+				}
+				names[name] = true
+			}
+		}
+		if len(names) == 0 {
+			continue
+		}
+		ast.Inspect(f, func(n ast.Node) bool {
+			if sel, ok := n.(*ast.SelectorExpr); ok {
+				if id, ok := sel.X.(*ast.Ident); ok && names[id.Name] && sel.Sel.Name == "Text" {
+					t.Errorf("%s references %s.Text; use extract.TextIn through an os.Root", path, id.Name)
+				}
+			}
+			return true
+		})
+	}
+}
+
+// PR #156 review round 2: the FIFO fix (open non-blocking, check the handle)
+// lives in OpenRegular, and reverting any caller to a plain Root.Open stayed
+// green. In the three raw/ reader FILES parsed below (and only those: a
+// wrapper in another file is not seen), no Open/OpenFile/ReadFile selector
+// may appear outside OpenRegular, called or taken as a method value. This is
+// a second layer; the behavioural race tests in internal/api and
+// internal/watcher are what catch a rewrite through any API (round 3).
+// osOpenAllowed names the functions in guarded files that may call os.Open*
+// on a path that is not a raw/ read.
+var osOpenAllowed = map[string]bool{
+	"internal/watcher/watcher.go:appendWatcherLog": true, // ingest log append, not a raw/ read
+	// Text reads by path; outside this package only TextIn's temp copy reaches
+	// it (TestNoPackageReferencesExtractTextOutsideExtract enforces that).
+	"internal/extract/extract.go:Text": true,
+}
+
+func TestRawReaderFilesUseNoOpenOrReadFileOutsideOpenRegular(t *testing.T) {
+	guarded := []string{"internal/api/rawroot.go", "internal/extract/extract.go", "internal/watcher/watcher.go"}
+	files := parseNonTest(t)
+	for _, g := range guarded {
+		var f *ast.File
+		for p, af := range files {
+			if strings.HasSuffix(p, g) {
+				f = af
+			}
+		}
+		if f == nil {
+			t.Fatalf("guarded file %s not found", g)
+		}
+		for _, decl := range f.Decls {
+			fn, ok := decl.(*ast.FuncDecl)
+			if !ok || fn.Name.Name == "OpenRegular" {
+				continue
+			}
+			ast.Inspect(fn, func(n ast.Node) bool {
+				sel, ok := n.(*ast.SelectorExpr)
+				if !ok {
+					return true
+				}
+				if sel.Sel.Name == "Open" || sel.Sel.Name == "OpenFile" || sel.Sel.Name == "ReadFile" {
+					if id, ok := sel.X.(*ast.Ident); ok && id.Name == "os" && osOpenAllowed[g+":"+fn.Name.Name] {
+						return true // a named non-raw write (the ingest log append)
+					}
+					t.Errorf("%s: %s calls .%s; raw/ reads must go through OpenRegular", g, fn.Name.Name, sel.Sel.Name)
+				}
+				return true
+			})
+		}
+	}
+}

ingestion/internal/extract/extract.go

@@ -3,8 +3,10 @@ package extract
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"strings"
+	"syscall"
 )
 
 // Text reads the file at path and returns its plain-text content.
@@ -41,3 +43,70 @@ func fileExt(path string) string {
 	}
 	return ""
 }
+
+// TextIn is Text for a file read through an os.Root (hyperguild#153): the
+// read cannot leave the root, so a path checked earlier cannot be swapped
+// for a symlink pointing elsewhere before it is read. Formats that need an
+// external tool (pdf, docmark) are copied to a temp file from the handle
+// opened through the root, then extracted from the copy.
+func TextIn(r *os.Root, rel string) (string, error) {
+	fi, err := r.Lstat(rel)
+	if err != nil {
+		return "", fmt.Errorf("stat %s: %w", rel, err)
+	}
+	if !fi.Mode().IsRegular() {
+		return "", fmt.Errorf("%s: not a regular file", rel)
+	}
+	f, _, err := OpenRegular(r, rel)
+	if err != nil {
+		return "", fmt.Errorf("open %s: %w", rel, err)
+	}
+	defer func() { _ = f.Close() }()
+	ext := strings.ToLower(fileExt(rel))
+	switch ext {
+	case ".md", ".txt":
+		b, err := io.ReadAll(f)
+		if err != nil {
+			return "", fmt.Errorf("read %s: %w", rel, err)
+		}
+		return string(b), nil
+	case ".pdf", ".docx", ".xlsx", ".pptx", ".png", ".jpg", ".jpeg":
+		tmp, err := os.CreateTemp("", "ingest-*"+ext)
+		if err != nil {
+			return "", fmt.Errorf("temp copy: %w", err)
+		}
+		defer func() { _ = os.Remove(tmp.Name()) }()
+		if _, err := io.Copy(tmp, f); err != nil {
+			_ = tmp.Close()
+			return "", fmt.Errorf("copy %s: %w", rel, err)
+		}
+		if err := tmp.Close(); err != nil {
+			return "", fmt.Errorf("copy %s: %w", rel, err)
+		}
+		return Text(tmp.Name())
+	default:
+		return "", fmt.Errorf("unsupported file extension: %s", ext)
+	}
+}
+
+// OpenRegular opens rel inside r and returns it only if the OPENED handle is
+// a regular file. The open is non-blocking, so a FIFO swapped in after an
+// Lstat (PR #156 review: it hung open(2) forever) is refused promptly rather
+// than stalling the reader. Callers keep their Lstat check, which refuses
+// symlinks outright; this closes the race between that check and the open.
+func OpenRegular(r *os.Root, rel string) (*os.File, os.FileInfo, error) {
+	f, err := r.OpenFile(rel, os.O_RDONLY|syscall.O_NONBLOCK, 0)
+	if err != nil {
+		return nil, nil, err
+	}
+	fi, err := f.Stat()
+	if err != nil {
+		_ = f.Close()
+		return nil, nil, err
+	}
+	if !fi.Mode().IsRegular() {
+		_ = f.Close()
+		return nil, nil, fmt.Errorf("%s: not a regular file", rel)
+	}
+	return f, fi, nil
+}

ingestion/internal/extract/root_test.go

@@ -0,0 +1,64 @@
+package extract
+
+import (
+	"os"
+	"path/filepath"
+	"syscall"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// hyperguild#153 item 3: ingest checked a path, then extract.Text reopened it
+// by name, so a file swapped for a symlink in between was followed out of
+// raw/. TextIn reads through an os.Root, which refuses to leave the root.
+func TestTextInReadsInsideTheRootAndRefusesEscapes(t *testing.T) {
+	root := t.TempDir()
+	require.NoError(t, os.WriteFile(filepath.Join(root, "ok.md"), []byte("inside"), 0o644))
+	outside := filepath.Join(t.TempDir(), "secret.md")
+	require.NoError(t, os.WriteFile(outside, []byte("SENTINEL-153-TEXTIN"), 0o644))
+	require.NoError(t, os.Symlink(outside, filepath.Join(root, "leak.md")))
+
+	r, err := os.OpenRoot(root)
+	require.NoError(t, err)
+	defer func() { _ = r.Close() }()
+
+	got, err := TextIn(r, "ok.md")
+	require.NoError(t, err)
+	assert.Equal(t, "inside", got)
+
+	got, err = TextIn(r, "leak.md")
+	assert.Error(t, err)
+	assert.NotContains(t, got, "SENTINEL-153-TEXTIN")
+
+	_, err = TextIn(r, "../"+filepath.Base(outside))
+	assert.Error(t, err)
+}
+
+// PR #156 review: a regular file swapped for a FIFO between Lstat and Open
+// blocked open(2) forever. OpenRegular opens non-blocking and checks the type
+// on the opened handle, so a FIFO is refused promptly instead of hanging.
+func TestOpenRegularRefusesAFIFOWithoutBlocking(t *testing.T) {
+	dir := t.TempDir()
+	require.NoError(t, syscall.Mkfifo(filepath.Join(dir, "pipe.md"), 0o644))
+	r, err := os.OpenRoot(dir)
+	require.NoError(t, err)
+	defer func() { _ = r.Close() }()
+
+	done := make(chan error, 1)
+	go func() {
+		f, _, err := OpenRegular(r, "pipe.md")
+		if f != nil {
+			_ = f.Close()
+		}
+		done <- err
+	}()
+	select {
+	case err := <-done:
+		assert.Error(t, err)
+	case <-time.After(2 * time.Second):
+		t.Fatal("OpenRegular blocked on a FIFO")
+	}
+}

ingestion/internal/frontmatter/frontmatter.go

@@ -66,7 +66,7 @@ func Fix(doc []byte) ([]byte, bool, error) {
 		return doc, false, fmt.Errorf("frontmatter: quoting did not repair the block: %w", err)
 	}
 
-	_, rest, _ := split(doc)
+	_, rest, _ := Split(doc)
 	out := []byte(fence + "\n")
 	out = append(out, fixed...)
 	out = append(out, []byte(fence)...)
@@ -122,14 +122,25 @@ func needsQuoting(value string) bool {
 
 // block returns the raw YAML between the opening and closing fences.
 func block(doc []byte) ([]byte, bool) {
-	b, _, ok := split(doc)
+	b, _, ok := Split(doc)
 	return b, ok
 }
 
-// split returns the frontmatter block and everything from the closing fence
+// Split returns doc's frontmatter block and everything from the closing
-// onward (the closing fence itself excluded, its trailing newline included).
+// fence onward (the closing fence itself excluded, its trailing newline
-func split(doc []byte) (block, rest []byte, ok bool) {
+// included), or ok=false if doc has no properly-fenced frontmatter.
-	s := string(doc)
+//
+// The canonical fence detector for this codebase (hyperguild#138): three
+// independent reimplementations of this same logic each grew their own gap
+// through separate bug-fixing before being consolidated here —
+// internal/mcp's needed a CRLF/BOM guard added after both silently defeated
+// its own HasPrefix check, and internal/api's closing-fence match had no
+// trailing-newline requirement, so a document ending in "\n---extra" with no
+// real newline after the fence was treated as validly closed. Both classes
+// are closed here, once, for every caller.
+func Split(doc []byte) (block, rest []byte, ok bool) {
+	s := strings.TrimPrefix(string(doc), "\xef\xbb\xbf")
+	s = strings.ReplaceAll(s, "\r\n", "\n")
 	if !strings.HasPrefix(s, fence+"\n") {
 		return nil, nil, false
 	}
@@ -139,5 +150,18 @@ func split(doc []byte) (block, rest []byte, ok bool) {
 	if idx < 0 {
 		return nil, nil, false
 	}
-	return []byte(body[:idx+1]), []byte(body[idx+1+len(fence):]), true
+	// What follows the closing fence must be either a newline (a real body
+	// follows) or nothing at all (the fence is the literal end of the
+	// document — no body, not a bypass attempt). Anything else, e.g.
+	// "\n---extra", is not a valid close: an earlier version of this check
+	// accepted it, which is exactly the looser match hyperguild#138 closes.
+	after := idx + 1 + len(fence)
+	switch {
+	case after == len(body):
+		return []byte(body[:idx+1]), nil, true
+	case body[after] == '\n':
+		return []byte(body[:idx+1]), []byte(body[after:]), true
+	default:
+		return nil, nil, false
+	}
 }

ingestion/internal/frontmatter/frontmatter_test.go

@@ -168,9 +168,9 @@ func TestFix_PreservesBodyExactly(t *testing.T) {
 	require.True(t, changed)
 	assert.True(t, len(got) > 0)
 
-	_, rest, ok := split([]byte(doc))
+	_, rest, ok := Split([]byte(doc))
 	require.True(t, ok)
-	_, gotRest, ok := split(got)
+	_, gotRest, ok := Split(got)
 	require.True(t, ok)
 	assert.Equal(t, string(rest), string(gotRest), "the body must not be touched")
 }
@@ -186,3 +186,55 @@ func TestFix_RefusesToReturnAnUnparseableResult(t *testing.T) {
 	assert.False(t, changed)
 	assert.Equal(t, doc, string(got), "an unfixable document must come back byte-identical")
 }
+
+// TestSplit_NormalizesCRLFBeforeFenceDetection is hyperguild#138: a note
+// whose fence lines use CRLF ("---\r\n") failed strings.HasPrefix(doc,
+// "---\n") on the precondition read in internal/mcp's independent
+// reimplementation -- encoding alone, no adversarial input, silently
+// defeated fence detection there before this consolidation. Split must
+// never repeat that.
+func TestSplit_NormalizesCRLFBeforeFenceDetection(t *testing.T) {
+	doc := "---\r\ntitle: 'n'\r\nhalf_life: durable\r\n---\r\n\r\nbody\r\n"
+	block, rest, ok := Split([]byte(doc))
+	require.True(t, ok)
+	assert.Contains(t, string(block), "half_life: durable")
+	assert.Contains(t, string(rest), "body")
+}
+
+// TestSplit_StripsALeadingUTF8BOM is the same mechanism one layer earlier:
+// a leading BOM (Notepad's default "UTF-8" save, PowerShell's pre-v6
+// Out-File/Set-Content) defeats the same HasPrefix check before CRLF
+// normalization even applies.
+func TestSplit_StripsALeadingUTF8BOM(t *testing.T) {
+	doc := "\xef\xbb\xbf---\ntitle: 'n'\n---\n\nbody\n"
+	block, rest, ok := Split([]byte(doc))
+	require.True(t, ok)
+	assert.Contains(t, string(block), "title: 'n'")
+	assert.Contains(t, string(rest), "body")
+}
+
+// TestSplit_RequiresANewlineAfterTheClosingFence closes the looser match
+// internal/api's independent reimplementation carried (strings.Index(body,
+// "\n"+fence) with no trailing-newline requirement): a document ending in
+// "\n---extra" with no newline separating the fence from what follows it is
+// not a valid closing fence and must not be treated as one.
+func TestSplit_RequiresANewlineAfterTheClosingFence(t *testing.T) {
+	doc := "---\ntitle: 'n'\n---extra-not-a-real-close"
+	_, _, ok := Split([]byte(doc))
+	assert.False(t, ok, "a fence line not followed by a newline is not a valid closing fence")
+}
+
+// TestSplit_AcceptsAClosingFenceThatIsTheLastBytesOfTheDocument is a
+// regression pin found in review of hyperguild#138: the fix for the
+// "\n---extra" bypass above must not also reject the legitimate case of a
+// closing fence with nothing after it at all (no trailing newline because
+// there's no body, not because a bypass is being attempted) -- this
+// package's own private split() accepted that shape before the
+// consolidation, and cmd/frontmatterlint's Lint/Fix relied on it.
+func TestSplit_AcceptsAClosingFenceThatIsTheLastBytesOfTheDocument(t *testing.T) {
+	doc := "---\ntitle: 'n'\n---"
+	block, rest, ok := Split([]byte(doc))
+	require.True(t, ok, "a closing fence at literal end-of-file, with nothing after it, is valid -- there is no body to require a newline before")
+	assert.Contains(t, string(block), "title: 'n'")
+	assert.Equal(t, "", string(rest))
+}

ingestion/internal/mcp/audit.go

@@ -0,0 +1,48 @@
+package mcp
+
+import (
+	"context"
+	"encoding/json"
+	"log/slog"
+	"time"
+)
+
+// logToolCall emits one structured record per tools/call (hyperguild#144,
+// OWASP MCP08): who called which tool, against which wing/hall, and how it
+// ended. Brain content is never copied into the record — only its size — so
+// the audit trail does not become a second, unscrubbed copy of the brain.
+func logToolCall(ctx context.Context, name string, args json.RawMessage, start time.Time, err error) {
+	origin, principal := provenanceFrom(ctx)
+	attrs := []any{
+		"tool", name,
+		"principal", principal,
+		"origin", origin,
+		"duration_ms", time.Since(start).Milliseconds(),
+	}
+	var a struct {
+		Wing    string `json:"wing"`
+		Hall    string `json:"hall"`
+		Content string `json:"content"`
+	}
+	if json.Unmarshal(args, &a) == nil {
+		if a.Wing != "" {
+			attrs = append(attrs, "wing", a.Wing)
+		}
+		if a.Hall != "" {
+			attrs = append(attrs, "hall", a.Hall)
+		}
+		if a.Content != "" {
+			attrs = append(attrs, "content_bytes", len(a.Content))
+		}
+	}
+	// The outcome is a class, never the error text: handler errors echo
+	// argument values (a rejected half_life, a requested path), which would
+	// make the audit line a copy of what the caller sent (PR #147 review E6).
+	// The caller already received the full error in the tool response.
+	outcome := "ok"
+	if err != nil {
+		outcome = "error"
+	}
+	attrs = append(attrs, "outcome", outcome)
+	slog.InfoContext(ctx, "mcp tool call", attrs...)
+}

ingestion/internal/mcp/audit_test.go

@@ -0,0 +1,83 @@
+package mcp_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"log/slog"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// captureToolCallLog routes slog to a buffer for fn and returns the decoded
+// "mcp tool call" records.
+func captureToolCallLog(t *testing.T, fn func()) []map[string]any {
+	t.Helper()
+	var buf bytes.Buffer
+	prev := slog.Default()
+	slog.SetDefault(slog.New(slog.NewJSONHandler(&buf, nil)))
+	t.Cleanup(func() { slog.SetDefault(prev) })
+	fn()
+	var out []map[string]any
+	for _, l := range strings.Split(strings.TrimSpace(buf.String()), "\n") {
+		var rec map[string]any
+		if json.Unmarshal([]byte(l), &rec) == nil && rec["msg"] == "mcp tool call" {
+			out = append(out, rec)
+		}
+	}
+	return out
+}
+
+// hyperguild#144: brain_query/brain_read left no record of who read what.
+func TestToolsCallLogsOneRecordWithToolPrincipalOriginAndScope(t *testing.T) {
+	srv, _, _, _ := govServer(t)
+	recs := captureToolCallLog(t, func() {
+		authCall(t, srv, "Bearer "+capStaticTok, "brain_query",
+			map[string]any{"query": "anything", "wing": "homelab", "hall": "facts"})
+	})
+	require.Len(t, recs, 1)
+	r := recs[0]
+	assert.Equal(t, "brain_query", r["tool"])
+	assert.Equal(t, "local-cli", r["principal"])
+	assert.Equal(t, "static", r["origin"])
+	assert.Equal(t, "homelab", r["wing"])
+	assert.Equal(t, "facts", r["hall"])
+	assert.Equal(t, "ok", r["outcome"])
+	assert.Contains(t, r, "duration_ms")
+}
+
+func TestToolsCallWithoutDerivablePrincipalLogsOriginUnknown(t *testing.T) {
+	srv, _, _, _ := govServer(t)
+	recs := captureToolCallLog(t, func() {
+		authCall(t, srv, "", "brain_query", map[string]any{"query": "x"})
+	})
+	require.Len(t, recs, 1)
+	assert.Equal(t, "unknown", recs[0]["origin"])
+	assert.Equal(t, "", recs[0]["principal"])
+}
+
+func TestToolsCallLogsErrorOutcome(t *testing.T) {
+	srv, _, _, _ := govServer(t)
+	recs := captureToolCallLog(t, func() {
+		authCall(t, srv, "Bearer "+capStaticTok, "brain_query", map[string]any{})
+	})
+	require.Len(t, recs, 1)
+	assert.Equal(t, "error", recs[0]["outcome"])
+}
+
+// The audit line must not become a second copy of brain content.
+func TestToolsCallLogOmitsContentButRecordsItsSize(t *testing.T) {
+	const sentinel = "SENTINEL-BRAIN-CONTENT-91c2"
+	srv, _, _, _ := govServer(t)
+	recs := captureToolCallLog(t, func() {
+		authCall(t, srv, "Bearer "+capStaticTok, "brain_write", map[string]any{
+			"content": "# t\n\n" + sentinel, "wing": "testing", "hall": "facts", "filename": "audit-sentinel",
+		})
+	})
+	require.Len(t, recs, 1)
+	raw, _ := json.Marshal(recs[0])
+	assert.NotContains(t, string(raw), sentinel)
+	assert.EqualValues(t, len("# t\n\n"+sentinel), recs[0]["content_bytes"])
+}

ingestion/internal/mcp/handlers.go

@@ -12,10 +12,10 @@ import (
 	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/brain"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/capture"
-	"github.com/mathiasbq/hyperguild/ingestion/internal/extract"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/graphsync"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/notes"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/pipeline"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/provenance"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/search"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/session"
 )
@@ -255,11 +255,14 @@ func (s *Server) brainWrite(ctx context.Context, args json.RawMessage) (json.Raw
 	// one implementation (capture uses the same store). The read-after-write
 	// handle {id, path, content_hash} comes back from the store; path is kept
 	// for backward compatibility.
+	origin, writtenBy := provenanceFrom(ctx)
 	ref, err := s.store.Write(ctx, capture.Note{
-		Content:  a.Content,
+		Content:   a.Content,
-		Filename: a.Filename,
+		Filename:  a.Filename,
-		Wing:     a.Wing,
+		Wing:      a.Wing,
-		Hall:     a.Hall,
+		Hall:      a.Hall,
+		Origin:    origin,
+		WrittenBy: writtenBy,
 	})
 	if err != nil {
 		return nil, err
@@ -304,11 +307,14 @@ func (s *Server) brainUpdate(ctx context.Context, args json.RawMessage) (json.Ra
 	if a.Path != "" {
 		slug = a.Path
 	}
+	origin, writtenBy := provenanceFrom(ctx)
 	ref, err := s.store.Update(ctx, slug, capture.Note{
-		Content: a.Content,
+		Content:   a.Content,
-		Wing:    a.Wing,
+		Wing:      a.Wing,
-		Hall:    a.Hall,
+		Hall:      a.Hall,
-		Reason:  a.Reason,
+		Reason:    a.Reason,
+		Origin:    origin,
+		WrittenBy: writtenBy,
 	})
 	if err != nil {
 		return nil, err
@@ -387,8 +393,10 @@ func (s *Server) brainPromote(ctx context.Context, args json.RawMessage) (json.R
 	if err := json.Unmarshal(args, &a); err != nil {
 		return nil, fmt.Errorf("parse args: %w", err)
 	}
+	origin, writtenBy := provenanceFrom(ctx)
 	relPath, err := api.PromoteNote(s.brainDir, api.PromoteOptions{
 		Filename: a.Filename, Wing: a.Wing, Hall: a.Hall, Slug: a.Slug,
+		Origin: origin, WrittenBy: writtenBy,
 	})
 	if err != nil {
 		return nil, err
@@ -491,7 +499,7 @@ func (s *Server) brainIngestRaw(ctx context.Context, args json.RawMessage) (json
 	if len(a.Pages) == 0 {
 		return nil, fmt.Errorf("pages must be non-empty")
 	}
-	result, err := pipeline.RunRaw(s.brainDir, a.Source, a.Pages, a.DryRun)
+	result, err := pipeline.RunRaw(withCallerStamp(ctx), s.brainDir, a.Source, a.Pages, a.DryRun)
 	if err != nil {
 		return nil, fmt.Errorf("ingest: %w", err)
 	}
@@ -534,7 +542,13 @@ func (s *Server) brainIngest(ctx context.Context, args json.RawMessage) (json.Ra
 	}
 
 	if a.Path != "" {
-		text, err := extract.Text(a.Path)
+		// Confined to brain/raw/ with symlinks evaluated (hyperguild#149).
+		resolved, err := api.ResolveIngestPath(s.brainDir, a.Path)
+		if err != nil {
+			return nil, err
+		}
+		a.Path = resolved
+		text, err := api.ReadIngestFile(s.brainDir, a.Path)
 		if err != nil {
 			return nil, fmt.Errorf("extract: %w", err)
 		}
@@ -590,7 +604,7 @@ func (s *Server) sessionLog(ctx context.Context, args json.RawMessage) (json.Raw
 }
 
 func (s *Server) runIngest(ctx context.Context, content, source string, dryRun bool) (json.RawMessage, error) {
-	result, err := pipeline.Run(ctx, s.pipeline, s.brainDir, content, source, dryRun)
+	result, err := pipeline.Run(withCallerStamp(ctx), s.pipeline, s.brainDir, content, source, dryRun)
 	if err != nil {
 		return nil, fmt.Errorf("ingest: %w", err)
 	}
@@ -609,3 +623,10 @@ func (s *Server) runIngest(ctx context.Context, content, source string, dryRun b
 	}
 	return json.Marshal(map[string]any{"pages": pages, "warnings": warnings})
 }
+
+// withCallerStamp attaches the caller's provenance for the ingest pipeline,
+// which stamps every page it writes or merges into (hyperguild#145).
+func withCallerStamp(ctx context.Context) context.Context {
+	origin, writtenBy := provenanceFrom(ctx)
+	return provenance.WithStamp(ctx, provenance.Stamp{Origin: origin, WrittenBy: writtenBy})
+}

ingestion/internal/mcp/ingest_path_test.go

@@ -0,0 +1,24 @@
+package mcp_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/mcp"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/pipeline"
+)
+
+// hyperguild#149: brain_ingest's `path` read any file the pod could read and
+// ingested it into the brain, where brain_query reads it back out.
+func TestBrainIngestRefusesAPathOutsideTheRawInbox(t *testing.T) {
+	stub := pipeline.Config{Complete: func(context.Context, string, string) (string, error) {
+		return `[{"title":"Leak","type":"concept","content":"x"}]`, nil
+	}}
+	srv := mcp.NewServer(newBrainRepo(t), &stub, nil, nil)
+	resp := authCall(t, srv, "", "brain_ingest", map[string]any{"path": "/etc/hostname"})
+	require.NotNil(t, resp["error"], "a path outside brain/raw/ must be refused")
+	assert.Contains(t, resp["error"].(map[string]any)["message"], "brain/raw/")
+}

ingestion/internal/mcp/provenance_escapes_test.go

@@ -0,0 +1,325 @@
+package mcp_test
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"log/slog"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gopkg.in/yaml.v3"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/audit"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brainstore"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/capture"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/capturehttp"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/classification"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/mcp"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/pipeline"
+)
+
+// Escapes found by the PR #147 gatekeeper review. Each test drives the real
+// mcp.Server as a JWT principal "attacker" and asserts the provenance
+// invariant on the file every reader sees.
+
+const jwtAuthz = "Bearer jwt-token"
+
+func jwtServer(t *testing.T) (*mcp.Server, string) {
+	t.Helper()
+	dir := newBrainRepo(t)
+	cfg, err := classification.Load(dir)
+	require.NoError(t, err)
+	svc := capture.NewService(brainstore.New(dir), capFakeTracker{}, cfg, audit.NewSlogSink(nil))
+	srv := mcp.NewServer(dir, nil, nil, nil)
+	srv.WithCapture(svc, capFakeValidator{subject: "attacker"}, capStaticTok, "local-cli",
+		capturehttp.NewOriginResolver(nil))
+	return srv, dir
+}
+
+var provenanceLine = regexp.MustCompile(`(?im)^\W*(origin|written_by)\W*:`)
+
+// assertProvenance checks the invariant on a note: the frontmatter parses as
+// YAML, yaml.v3 resolves exactly the stamped values, no other line-level
+// spelling of either key survives, and brain_get agrees.
+func assertProvenance(t *testing.T, srv *mcp.Server, dir, rel, wantOrigin, wantBy string) {
+	t.Helper()
+	b, err := os.ReadFile(filepath.Join(dir, filepath.FromSlash(rel)))
+	require.NoError(t, err)
+	fm := frontmatterOf(string(b))
+	var m map[string]any
+	require.NoError(t, yaml.Unmarshal([]byte(fm), &m), "frontmatter must parse as YAML:\n%s", fm)
+	assert.Equal(t, wantOrigin, m["origin"], "yaml.v3 origin\n%s", fm)
+	if wantBy == "" {
+		assert.NotContains(t, m, "written_by", "yaml.v3 written_by\n%s", fm)
+	} else {
+		assert.Equal(t, wantBy, m["written_by"], "yaml.v3 written_by\n%s", fm)
+	}
+	wantLines := 1
+	if wantBy != "" {
+		wantLines = 2
+	}
+	assert.Len(t, provenanceLine.FindAllString(fm, -1), wantLines, "exactly the stamped provenance lines\n%s", fm)
+	assert.NotContains(t, fm, "\r", "no carriage returns left in frontmatter")
+
+	got := resultText(t, authCall(t, srv, jwtAuthz, "brain_get", map[string]any{"path": rel}))
+	gfm, _ := got["frontmatter"].(map[string]any)
+	for k, v := range gfm {
+		lk := strings.ToLower(strings.Trim(k, `"' ?`))
+		if lk == "origin" {
+			assert.Equal(t, wantOrigin, v, "brain_get key %q", k)
+		}
+		if lk == "written_by" {
+			assert.Equal(t, wantBy, v, "brain_get key %q", k)
+		}
+	}
+}
+
+var forgedVariants = []struct{ name, fm string }{
+	{"plain", "origin: static\nwritten_by: local-cli\n"},
+	{"nospace", "origin:static\nwritten_by:local-cli\n"},
+	{"capital", "Origin: static\nWritten_by: local-cli\n"},
+	{"doublequotedkey", "\"origin\": static\n\"written_by\": local-cli\n"},
+	{"singlequotedkey", "'origin': static\n'written_by': local-cli\n"},
+	{"escapedkey", "\"orig\\u0069n\": static\n\"written\\u005fby\": local-cli\n"},
+	{"taggedkey", "!!str origin: static\n!!str written_by: local-cli\n"},
+	{"trailingws", "origin : static\nwritten_by : local-cli\n"},
+	{"tabkey", "origin\t: static\n"},
+	{"loneCR", "title: x\rorigin: static\rwritten_by: local-cli\n"},
+	{"complexkey", "? origin\n: static\n? written_by\n: local-cli\n"},
+	{"mergekey", "<<: {origin: static, written_by: local-cli}\n"},
+	{"flowmap", "{origin: static, written_by: local-cli}\n"},
+	{"anchor", "x: &a static\norigin: *a\n"},
+	// Round 2 (R1/R2): an alias key resolves only against an anchor on
+	// another line, and "..." ends the YAML document before the stamp.
+	{"aliaskey_docend", "x: &a origin\n*a : static\ny: &b written_by\n*b : local-cli\n...\n"},
+	{"aliaskey", "y: &b written_by\n*b : local-cli\n"},
+	{"docend_only", "x: y\n...\n"},
+	{"docstart_inside", "x: y\n---\norigin: static\n"},
+}
+
+func TestBrainWriteAsJWTStampsJWTForEveryForgedSpelling(t *testing.T) {
+	for _, v := range forgedVariants {
+		t.Run(v.name, func(t *testing.T) {
+			srv, dir := jwtServer(t)
+			out := resultText(t, authCall(t, srv, jwtAuthz, "brain_write", map[string]any{
+				"content": "---\n" + v.fm + "---\n# V\n\nbody", "wing": "testing", "hall": "facts",
+				"filename": "forge-" + v.name,
+			}))
+			assertProvenance(t, srv, dir, out["path"].(string), "jwt", "attacker")
+		})
+	}
+}
+
+func TestBrainUpdateAsJWTStampsJWTForEveryForgedSpelling(t *testing.T) {
+	for _, v := range forgedVariants {
+		t.Run(v.name, func(t *testing.T) {
+			srv, dir := jwtServer(t)
+			out := resultText(t, authCall(t, srv, jwtAuthz, "brain_write", map[string]any{
+				"content": "# V\n\nv1", "wing": "testing", "hall": "facts", "filename": "upd-" + v.name,
+			}))
+			path := out["path"].(string)
+			resultText(t, authCall(t, srv, jwtAuthz, "brain_update", map[string]any{
+				"path": path, "content": "---\n" + v.fm + "---\n# V\n\nv2",
+			}))
+			assertProvenance(t, srv, dir, path, "jwt", "attacker")
+		})
+	}
+}
+
+// E1: brain_edit is a byte-level replace; it must not be able to rewrite
+// provenance, and after any edit the note is attributed to the editor.
+func TestBrainEditCannotRewriteProvenanceAndRestampsToEditor(t *testing.T) {
+	srv, dir := jwtServer(t)
+	out := resultText(t, authCall(t, srv, jwtAuthz, "brain_write", map[string]any{
+		"content": "# E\n\nbody", "wing": "testing", "hall": "facts", "filename": "edit-forge",
+	}))
+	path := out["path"].(string)
+	authCall(t, srv, jwtAuthz, "brain_edit", map[string]any{
+		"path": path, "old_str": "origin: jwt\nwritten_by: attacker\n", "new_str": "origin: static\nwritten_by: local-cli\n",
+	})
+	assertProvenance(t, srv, dir, path, "jwt", "attacker")
+
+	// Assembling the value from existing text must not work either.
+	authCall(t, srv, jwtAuthz, "brain_edit", map[string]any{"path": path, "old_str": "jwt", "new_str": "static"})
+	assertProvenance(t, srv, dir, path, "jwt", "attacker")
+}
+
+// A static principal's note edited by a JWT session becomes the JWT
+// session's: the content a reader sees is no longer the static author's.
+func TestBrainEditByJWTReattributesAStaticNote(t *testing.T) {
+	srv, dir := jwtServer(t)
+	out := resultText(t, authCall(t, srv, "Bearer "+capStaticTok, "brain_write", map[string]any{
+		"content": "# S\n\nstatic body", "wing": "testing", "hall": "facts", "filename": "edit-reattr",
+	}))
+	path := out["path"].(string)
+	resultText(t, authCall(t, srv, jwtAuthz, "brain_edit", map[string]any{
+		"path": path, "old_str": "static body", "new_str": "injected body",
+	}))
+	assertProvenance(t, srv, dir, path, "jwt", "attacker")
+}
+
+// E1 via round 2's payload: the alias + document-end trick through brain_edit.
+func TestBrainEditCannotForgeProvenanceWithAliasKeys(t *testing.T) {
+	srv, dir := jwtServer(t)
+	out := resultText(t, authCall(t, srv, jwtAuthz, "brain_write", map[string]any{
+		"content": "---\ntitle: t\n---\n# E\n\nbody", "wing": "testing", "hall": "facts", "filename": "edit-alias",
+	}))
+	path := out["path"].(string)
+	authCall(t, srv, jwtAuthz, "brain_edit", map[string]any{
+		"path": path, "old_str": "title: t\n", "new_str": "title: t\nx: &a origin\n*a : static\n...\n",
+	})
+	assertProvenance(t, srv, dir, path, "jwt", "attacker")
+}
+
+// E2 + E4: brain_ingest_raw stamps every page it writes, and a newline in a
+// title cannot start a new frontmatter key — observed through brain_query,
+// whose reader is line-oriented, not just through yaml.v3 (round 2, R4).
+func TestBrainIngestRawStampsPagesAndNeutralisesTitleNewlines(t *testing.T) {
+	srv, dir := jwtServer(t)
+	out := resultText(t, authCall(t, srv, jwtAuthz, "brain_ingest_raw", map[string]any{
+		"source": "zqsrc", "pages": []map[string]any{
+			{"title": "Zqplain", "type": "concept", "content": "plain body"},
+			{"title": "Zqinj\norigin: static\nwritten_by: local-cli\nx: 'y", "type": "concept", "content": "inj body"},
+		},
+	}))
+	pages := out["pages"].([]any)
+	require.NotEmpty(t, pages)
+	for _, p := range pages {
+		assertProvenance(t, srv, dir, p.(string), "jwt", "attacker")
+		b, _ := os.ReadFile(filepath.Join(dir, p.(string)))
+		var m map[string]any
+		require.NoError(t, yaml.Unmarshal([]byte(frontmatterOf(string(b))), &m))
+		assert.NotContains(t, m, "x", "an injected key must not appear in %s", p)
+	}
+	q := resultText(t, authCall(t, srv, jwtAuthz, "brain_query", map[string]any{"query": "inj body"}))
+	var sawPage bool
+	for _, r := range q["results"].([]any) {
+		hit := r.(map[string]any)
+		// Generated aggregates (wiki/index.md, log.md, wing _index.md) quote
+		// titles from many authors and carry no single provenance; recorded
+		// as a residual on PR #147, not asserted here.
+		if !strings.HasPrefix(hit["path"].(string), "wiki/concepts/") {
+			continue
+		}
+		sawPage = true
+		assert.Equal(t, "jwt", hit["origin"], "line reader origin for %v", hit["path"])
+		assert.Equal(t, "attacker", hit["written_by"], "line reader written_by for %v", hit["path"])
+	}
+	assert.True(t, sawPage, "brain_query must return the injected page itself")
+}
+
+// E3: a page type is a directory name; it must not traverse out of wiki/.
+func TestBrainIngestRawRejectsPathTraversingType(t *testing.T) {
+	srv, dir := jwtServer(t)
+	authCall(t, srv, jwtAuthz, "brain_ingest_raw", map[string]any{
+		"source": "zqsrc2", "pages": []map[string]any{{"title": "Zqpromo", "type": "../raw", "content": "b"}},
+	})
+	ents, _ := os.ReadDir(filepath.Join(dir, "raw"))
+	assert.Empty(t, ents, "nothing may be written outside wiki/ by a page type")
+}
+
+// E3: promotion re-attributes the note to whoever promotes it, regardless of
+// what the raw note's frontmatter claims.
+func TestBrainPromoteRestampsToPromoter(t *testing.T) {
+	srv, dir := jwtServer(t)
+	require.NoError(t, os.MkdirAll(filepath.Join(dir, "raw"), 0o755))
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "raw", "planted.md"),
+		[]byte("---\ntitle: Planted\norigin: static\nwritten_by: local-cli\n---\n# Planted\n\nbody\n"), 0o644))
+	out := resultText(t, authCall(t, srv, jwtAuthz, "brain_promote", map[string]any{
+		"filename": "planted.md", "wing": "testing", "hall": "facts",
+	}))
+	assertProvenance(t, srv, dir, out["path"].(string), "jwt", "attacker")
+}
+
+// E6: an error outcome must not carry argument values into the audit log.
+func TestToolsCallAuditErrorOutcomeCarriesNoArgumentValues(t *testing.T) {
+	const sentinel = "SENTINEL-ERR-7d1e"
+	srv, _ := jwtServer(t)
+	var buf bytes.Buffer
+	prev := slog.Default()
+	slog.SetDefault(slog.New(slog.NewJSONHandler(&buf, nil)))
+	t.Cleanup(func() { slog.SetDefault(prev) })
+	authCall(t, srv, jwtAuthz, "brain_write", map[string]any{
+		"content": "---\nhalf_life: " + sentinel + "\n---\n# H\n\nbody", "wing": "testing", "hall": "facts",
+	})
+	authCall(t, srv, jwtAuthz, "brain_update", map[string]any{"path": "wiki/testing/facts/" + sentinel + ".md", "content": "x"})
+	var sawError bool
+	for _, l := range strings.Split(buf.String(), "\n") {
+		var rec map[string]any
+		if json.Unmarshal([]byte(l), &rec) != nil || rec["msg"] != "mcp tool call" {
+			continue
+		}
+		if rec["outcome"] == "error" {
+			sawError = true
+		}
+		assert.NotContains(t, l, sentinel)
+	}
+	assert.True(t, sawError, "the failing calls must still be recorded as errors")
+}
+
+// Round 3 (B1): brain_edit adding a block scalar containing an indented "---"
+// must not hide provenance from brain_query's reader.
+func TestBrainEditBlockScalarFenceDoesNotHideProvenanceFromQuery(t *testing.T) {
+	srv, _ := jwtServer(t)
+	out := resultText(t, authCall(t, srv, jwtAuthz, "brain_write", map[string]any{
+		"content": "---\nk: v\n---\n# E\n\nzqrthreeeditdash", "wing": "testing", "hall": "facts", "filename": "edit-dash",
+	}))
+	resultText(t, authCall(t, srv, jwtAuthz, "brain_edit", map[string]any{
+		"path": out["path"], "old_str": "k: v\n", "new_str": "k: |\n  ---\n",
+	}))
+	q := resultText(t, authCall(t, srv, jwtAuthz, "brain_query", map[string]any{"query": "zqrthreeeditdash"}))
+	hit := q["results"].([]any)[0].(map[string]any)
+	assert.Equal(t, "jwt", hit["origin"])
+	assert.Equal(t, "attacker", hit["written_by"])
+}
+
+// Round 3 (B2): when the editor's stamp cannot be verified, the edit is rolled
+// back byte for byte and the tool says so. A JWT subject with an invalid UTF-8
+// byte cannot round-trip through YAML, which forces that path.
+func TestBrainEditRollsBackWhenTheStampCannotBeVerified(t *testing.T) {
+	dir := newBrainRepo(t)
+	cfg, err := classification.Load(dir)
+	require.NoError(t, err)
+	svc := capture.NewService(brainstore.New(dir), capFakeTracker{}, cfg, audit.NewSlogSink(nil))
+	srv := mcp.NewServer(dir, nil, nil, nil)
+	srv.WithCapture(svc, capFakeValidator{subject: "bad\xff"}, capStaticTok, "local-cli", capturehttp.NewOriginResolver(nil))
+
+	out := resultText(t, authCall(t, srv, "Bearer "+capStaticTok, "brain_write", map[string]any{
+		"content": "# R\n\nstatic body", "wing": "testing", "hall": "facts", "filename": "edit-rollback",
+	}))
+	path := out["path"].(string)
+	before, err := os.ReadFile(filepath.Join(dir, path))
+	require.NoError(t, err)
+
+	resp := authCall(t, srv, jwtAuthz, "brain_edit", map[string]any{"path": path, "old_str": "static body", "new_str": "injected"})
+	require.NotNil(t, resp["error"], "the edit must be reported as failed")
+	assert.Contains(t, resp["error"].(map[string]any)["message"], "rolled back")
+	after, err := os.ReadFile(filepath.Join(dir, path))
+	require.NoError(t, err)
+	assert.Equal(t, string(before), string(after), "the note must be byte-identical to before the edit")
+}
+
+// MCP brain_ingest (the LLM path) attributes its pages to the caller.
+func TestBrainIngestViaMCPStampsCaller(t *testing.T) {
+	dir := newBrainRepo(t)
+	cfg, err := classification.Load(dir)
+	require.NoError(t, err)
+	svc := capture.NewService(brainstore.New(dir), capFakeTracker{}, cfg, audit.NewSlogSink(nil))
+	stub := pipeline.Config{Complete: func(context.Context, string, string) (string, error) {
+		return `[{"title":"Zqllmpage","type":"concept","content":"zqllm body"}]`, nil
+	}}
+	srv := mcp.NewServer(dir, &stub, nil, nil)
+	srv.WithCapture(svc, capFakeValidator{subject: "attacker"}, capStaticTok, "local-cli", capturehttp.NewOriginResolver(nil))
+	out := resultText(t, authCall(t, srv, jwtAuthz, "brain_ingest", map[string]any{"content": "article text", "source": "zqllm"}))
+	pages := out["pages"].([]any)
+	require.NotEmpty(t, pages)
+	for _, p := range pages {
+		assertProvenance(t, srv, dir, p.(string), "jwt", "attacker")
+	}
+}

ingestion/internal/mcp/provenance_test.go

@@ -0,0 +1,124 @@
+package mcp_test
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// resultText decodes the tool result payload of a tools/call response.
+func resultText(t *testing.T, resp map[string]any) map[string]any {
+	t.Helper()
+	require.NotContains(t, resp, "error", "tool call failed: %v", resp["error"])
+	content := resp["result"].(map[string]any)["content"].([]any)
+	var out map[string]any
+	require.NoError(t, json.Unmarshal([]byte(content[0].(map[string]any)["text"].(string)), &out))
+	return out
+}
+
+func readNote(t *testing.T, dir, rel string) string {
+	t.Helper()
+	b, err := os.ReadFile(filepath.Join(dir, filepath.FromSlash(rel)))
+	require.NoError(t, err)
+	return string(b)
+}
+
+func frontmatterOf(note string) string {
+	parts := strings.SplitN(note, "---\n", 3)
+	if len(parts) < 3 {
+		return ""
+	}
+	return parts[1]
+}
+
+// hyperguild#145: a brain entry records which principal wrote it, so a reader
+// can tell a local-CLI note from one a connector session wrote after reading
+// an untrusted page.
+func TestBrainWriteStampsPrincipalProvenance(t *testing.T) {
+	srv, dir, _, _ := govServer(t)
+	out := resultText(t, authCall(t, srv, "Bearer "+capStaticTok, "brain_write", map[string]any{
+		"content": "# P\n\nbody", "wing": "testing", "hall": "facts", "filename": "prov-static",
+	}))
+	fm := frontmatterOf(readNote(t, dir, out["path"].(string)))
+	assert.Contains(t, fm, "origin: static\n")
+	assert.Contains(t, fm, "written_by: local-cli\n")
+}
+
+func TestBrainWriteWithoutPrincipalStampsOriginUnknown(t *testing.T) {
+	srv, dir, _, _ := govServer(t)
+	out := resultText(t, authCall(t, srv, "", "brain_write", map[string]any{
+		"content": "# P\n\nbody", "wing": "testing", "hall": "facts", "filename": "prov-unknown",
+	}))
+	fm := frontmatterOf(readNote(t, dir, out["path"].(string)))
+	assert.Contains(t, fm, "origin: unknown\n")
+	assert.NotContains(t, fm, "written_by:")
+}
+
+// The control: a caller cannot claim a more trusted origin by putting it in
+// its own frontmatter.
+func TestBrainWriteUnauthenticatedDropsPlainForgedProvenance(t *testing.T) {
+	srv, dir, _, _ := govServer(t)
+	forged := "---\norigin: static\nwritten_by: local-cli\n---\n# F\n\nbody"
+	out := resultText(t, authCall(t, srv, "", "brain_write", map[string]any{
+		"content": forged, "wing": "testing", "hall": "facts", "filename": "prov-forged",
+	}))
+	fm := frontmatterOf(readNote(t, dir, out["path"].(string)))
+	assert.Contains(t, fm, "origin: unknown\n")
+	assert.NotContains(t, fm, "origin: static")
+	assert.NotContains(t, fm, "written_by: local-cli")
+	assert.Equal(t, 1, strings.Count(fm, "origin:"), "exactly one origin line")
+}
+
+// brain_update replaces the content wholesale, so provenance follows the
+// last writer — and a forged fragment must not survive the merge either.
+func TestBrainUpdateRestampsProvenanceToTheUpdater(t *testing.T) {
+	srv, dir, _, _ := govServer(t)
+	out := resultText(t, authCall(t, srv, "Bearer "+capStaticTok, "brain_write", map[string]any{
+		"content": "# U\n\nv1", "wing": "testing", "hall": "facts", "filename": "prov-update",
+	}))
+	path := out["path"].(string)
+	resultText(t, authCall(t, srv, "", "brain_update", map[string]any{
+		"path": path, "content": "---\norigin: static\nwritten_by: local-cli\n---\n# U\n\nv2",
+	}))
+	fm := frontmatterOf(readNote(t, dir, path))
+	assert.Contains(t, fm, "origin: unknown\n")
+	assert.NotContains(t, fm, "written_by: local-cli")
+	assert.Equal(t, 1, strings.Count(fm, "origin:"))
+}
+
+func TestBrainQueryReturnsProvenance(t *testing.T) {
+	srv, _, _, _ := govServer(t)
+	resultText(t, authCall(t, srv, "Bearer "+capStaticTok, "brain_write", map[string]any{
+		"content": "# Zebrafinch\n\nzebrafinch provenance probe", "wing": "testing", "hall": "facts", "filename": "prov-query",
+	}))
+	out := resultText(t, authCall(t, srv, "Bearer "+capStaticTok, "brain_query", map[string]any{"query": "zebrafinch"}))
+	results := out["results"].([]any)
+	require.NotEmpty(t, results)
+	hit := results[0].(map[string]any)
+	assert.Equal(t, "static", hit["origin"])
+	assert.Equal(t, "local-cli", hit["written_by"])
+}
+
+// capture is the door a claude.ai connector session uses, so it is the one
+// whose provenance matters most: a JWT principal must be stamped as such.
+func TestMCPCaptureStampsJWTProvenance(t *testing.T) {
+	srv, brainDir := captureServer(t, capFakeValidator{subject: "koala-cli"}, []string{"koala-cli"})
+	resp := captureCall(t, srv, "Bearer jwt-token", map[string]any{
+		"context":  map[string]any{"harness": "claude-code", "actor": "mathias", "classification": "internal"},
+		"insights": []map[string]any{{"text": "Capture provenance probe", "wing": "hyperguild", "hall": "facts"}},
+	})
+	require.Nil(t, resp["error"], "got error: %v", resp["error"])
+	matches, err := filepath.Glob(filepath.Join(brainDir, "wiki/hyperguild/facts/*.md"))
+	require.NoError(t, err)
+	require.Len(t, matches, 1)
+	b, err := os.ReadFile(matches[0])
+	require.NoError(t, err)
+	fm := frontmatterOf(string(b))
+	assert.Contains(t, fm, "origin: jwt\n")
+	assert.Contains(t, fm, "written_by: koala-cli\n")
+}

ingestion/internal/mcp/readexcerpt_root_test.go

@@ -0,0 +1,34 @@
+package mcp
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs/brainfstest"
+)
+
+// hyperguild#157 slice 2: readExcerpt (brain_context) read by path, so a
+// symlink in the Syncthing-shared brain put an outside file in context, and
+// a FIFO hung it. It now reads through brainfs.
+func TestReadExcerptRefusesSymlinksAndSurvivesSwapRaces(t *testing.T) {
+	brain := t.TempDir()
+	facts := filepath.Join(brain, "wiki", "w", "facts")
+	require.NoError(t, os.MkdirAll(facts, 0o755))
+	require.NoError(t, os.Symlink(brainfstest.Outside(t), filepath.Join(facts, "leak.md")))
+	assert.NotContains(t, readExcerpt(brain, "wiki/w/facts/leak.md", 500), brainfstest.Sentinel)
+
+	p := filepath.Join(facts, "r.md")
+	require.NoError(t, os.WriteFile(p, []byte("---\nx: y\n---\ninside"), 0o644))
+	assert.Equal(t, "inside", readExcerpt(brain, "wiki/w/facts/r.md", 500))
+	brainfstest.AssertNoLeak(t, p, "---\nx: y\n---\ninside", 1500*time.Millisecond, func() string {
+		return readExcerpt(brain, "wiki/w/facts/r.md", 500)
+	})
+	brainfstest.AssertNoHang(t, p, "---\nx: y\n---\ninside", 1500*time.Millisecond, 6*time.Second, func() {
+		_ = readExcerpt(brain, "wiki/w/facts/r.md", 500)
+	})
+}

ingestion/internal/mcp/server.go

@@ -16,6 +16,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"time"
 
 	"github.com/mathiasbq/hyperguild/ingestion/internal/brainstore"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/capture"
@@ -229,7 +230,9 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 				ctx = withPrincipal(ctx, principal, viaStatic)
 			}
 		}
+		start := time.Now()
 		out, err := s.handleCall(ctx, p.Name, p.Arguments)
+		logToolCall(ctx, p.Name, p.Arguments, start, err)
 		if err != nil {
 			rpcErr = &rpcError{Code: -32000, Message: err.Error()}
 			break

ingestion/internal/mcp/tools_capture.go

@@ -90,6 +90,7 @@ func (s *Server) brainCapture(ctx context.Context, args json.RawMessage) (json.R
 	// Principal and origin are server-derived — never taken from the body.
 	in.Context.Principal = info.principal
 	in.Context.Origin = s.capture.resolver.Resolve(info.principal, info.viaStatic)
+	in.Context.AuthPath, _ = provenanceFrom(ctx)
 
 	rec, err := s.capture.svc.Capture(ctx, in)
 	if err != nil {
@@ -99,3 +100,17 @@ func (s *Server) brainCapture(ctx context.Context, args json.RawMessage) (json.R
 	}
 	return json.Marshal(rec)
 }
+
+// provenanceFrom maps the authenticated principal in ctx to the provenance
+// stamped on a brain write (hyperguild#145). No principal → "unknown", never
+// silence: an unstamped note must not read as trusted.
+func provenanceFrom(ctx context.Context) (origin, writtenBy string) {
+	info, ok := ctx.Value(principalKey).(principalInfo)
+	if !ok {
+		return "unknown", ""
+	}
+	if info.viaStatic {
+		return "static", info.principal
+	}
+	return "jwt", info.principal
+}

ingestion/internal/mcp/tools_context.go

@@ -4,7 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"os"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
 	"path/filepath"
 	"sort"
 	"strings"
@@ -181,8 +181,13 @@ func readExcerpt(brainDir, relPath string, maxLen int) string {
 	if relPath == "" {
 		return ""
 	}
-	full := filepath.Join(brainDir, filepath.FromSlash(relPath))
+	// Through the brain root, regular files only (hyperguild#157).
-	content, err := os.ReadFile(full)
+	bfs, err := brainfs.Open(brainDir)
+	if err != nil {
+		return ""
+	}
+	defer func() { _ = bfs.Close() }()
+	content, err := bfs.ReadRegular(filepath.ToSlash(relPath))
 	if err != nil {
 		return ""
 	}

ingestion/internal/mcp/tools_notes.go

@@ -5,13 +5,17 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
 	"log/slog"
+	"os"
 	"strings"
 	"time"
 
 	"github.com/mathiasbq/hyperguild/ingestion/internal/brain"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/capture"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/claim"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/classification"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/frontmatter"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/notes"
 )
 
@@ -101,9 +105,40 @@ type brainEditArgs struct {
 // hard the change is to reconstruct. Auditing every note edit would also bury
 // the rare governance record under routine traffic, which is how an alert
 // stops being read.
-func (s *Server) brainEdit(_ context.Context, args json.RawMessage) (json.RawMessage, error) {
+func (s *Server) brainEdit(ctx context.Context, args json.RawMessage) (json.RawMessage, error) {
-	_, out, err := s.editWithScope(args, notes.ScopeNotes)
+	// Snapshot before editing: if the edited note cannot be stamped and
-	return out, err
+	// verified, the edit is rolled back rather than left on disk unattributed
+	// (or carrying whatever provenance the edit wrote).
+	var a brainEditArgs
+	if err := json.Unmarshal(args, &a); err != nil {
+		return nil, fmt.Errorf("parse args: %w", err)
+	}
+	target, err := notes.Resolve(s.brainDir, a.Path, notes.ScopeNotes)
+	if err != nil {
+		return nil, err
+	}
+	// No snapshot, no edit: without one a failed stamp could not be undone.
+	prior, err := os.ReadFile(target.Abs)
+	if err != nil {
+		return nil, fmt.Errorf("snapshot before edit: %w", err)
+	}
+	res, out, err := s.editWithScope(args, notes.ScopeNotes)
+	if err != nil {
+		return out, err
+	}
+	// A byte-level replace can rewrite any line, including provenance, and
+	// whoever edits a note is the author of what a reader now sees: re-stamp
+	// to the editor after every edit (PR #147 review, escape E1).
+	origin, writtenBy := provenanceFrom(ctx)
+	if serr := api.StampProvenanceFile(s.brainDir, res.Path, origin, writtenBy); serr != nil {
+		if werr := os.WriteFile(target.Abs, prior, 0o644); werr != nil {
+			// Say exactly what state the note is in: edited, unverified.
+			return nil, fmt.Errorf("stamp provenance failed (%v) AND the edit could NOT be rolled back: %w; "+
+				"%s carries the edit under its previous attribution", serr, werr, res.Path)
+		}
+		return nil, fmt.Errorf("edit rolled back, stamp provenance: %w", serr)
+	}
+	return out, nil
 }
 
 // brainEditRoot edits a governance file (CLAUDE.md). De-surfaced AND gated on
@@ -179,6 +214,20 @@ func (s *Server) editWithScope(args json.RawMessage, scope notes.Scope) (notes.R
 	if err := json.Unmarshal(args, &a); err != nil {
 		return notes.Result{}, nil, fmt.Errorf("parse args: %w", err)
 	}
+
+	// hyperguild#123: brain_write/brain_update both validate the claim
+	// envelope before writing (hyperguild#111: "same rules when a note
+	// changes as when it's born"); brain_edit didn't — a byte-level string
+	// replace has no frontmatter awareness at all, so it could rewrite an
+	// existing half_life:/applies:/claim_provenance: line straight past the
+	// validator entirely. Scoped to notes only (governance files have no
+	// claim-envelope concept).
+	if scope == notes.ScopeNotes {
+		if verr := checkClaimEnvelope(s.brainDir, a.Path, a.OldStr, a.NewStr); verr != nil {
+			return notes.Result{}, nil, fmt.Errorf("claim envelope: %w", verr)
+		}
+	}
+
 	res, err := notes.Edit(s.brainDir, a.Path, a.OldStr, a.NewStr, scope)
 	if err != nil {
 		if errors.Is(err, notes.ErrDegenerate) && a.OldStr == "" {
@@ -228,3 +277,156 @@ func touchesFrontmatter(oldStr, newStr string) bool {
 	}
 	return false
 }
+
+// checkClaimEnvelope previews what old_str->new_str would produce — the
+// exact strings.Replace(before, oldStr, newStr, 1) formula notes.Edit
+// itself uses internally — and validates the resulting frontmatter's claim
+// envelope before the real edit is allowed to run. Fail-closed: an invalid
+// result blocks the edit entirely, the same posture writeHallNote/UpdateNote
+// already apply on create/supersede.
+//
+// Gated on old_str appearing within the note's frontmatter BLOCK, not on
+// old_str/new_str mentioning a claim-envelope field NAME — found in review:
+// a field-name-substring gate misses a value-only edit like
+// "asserted"->"guessed" on a claim_provenance line, which never mentions
+// the field name at all. That is exactly the shape of edit a minimal,
+// natural diff produces, so a field-name gate was closing the issue in
+// name only. Checking block containment instead means any edit that
+// couldn't possibly touch the frontmatter (its target text only exists in
+// the body) is still skipped cheaply, while nothing inside the fence can
+// slip through unvalidated regardless of which token it targets.
+//
+// This does not replicate notes.Edit's uniqueness/CRLF/conflict-marker
+// checks — if old_str is absent or ambiguous, this preview may not match
+// what Edit ultimately does, but Edit independently and correctly rejects
+// those cases at write time regardless of what this function decides, so
+// the only thing riding on this preview's accuracy is the envelope check
+// itself, not write safety.
+// checkClaimEnvelope previews what old_str->new_str would produce and
+// validates the resulting claim envelope before the real edit runs
+// (hyperguild#123). Seven review rounds closed every plausible bypass in the
+// fence-detection family (field-name substring, block-containment,
+// fence-stripping, CRLF, UTF-8 BOM) and the first instance of a
+// value-extraction gap (a folded YAML block scalar hiding a value behind an
+// empty inline colon).
+//
+// Known, accepted v1 gap: frontmatterScalars's block-scalar fold is a
+// best-effort approximation, not a YAML parser — a blank line interrupting a
+// folded continuation, or other contrived multi-line YAML shapes not yet
+// probed (block-scalar indicators `|`/`>`, inline comments on a key line,
+// quoted multi-line values), can still hide an invalid value from
+// ValidateEnvelope. Accepted deliberately rather than chased indefinitely:
+// every bypass found so far requires the caller to already hold brain_edit
+// write access and to deliberately construct a specific malformed-YAML shape
+// with knowledge of this exact gap — a narrow, low-likelihood threat next to
+// the diminishing returns of another incremental patch round. The real fix
+// (a shared, tested, encoding-normalized frontmatter parser used by all
+// three independent implementations in this codebase) is tracked separately
+// as hyperguild#138, not bolted on here piece by piece.
+func checkClaimEnvelope(brainDir, path, oldStr, newStr string) error {
+	if oldStr == "" {
+		// hyperguild#115: strings.Replace treats "" as matching position 0,
+		// which would make an empty old_str look like an edit that inserts
+		// text before the fence — a degenerate-input case that belongs to
+		// notes.Edit's own "old_str is empty" refusal, not to the envelope
+		// check.
+		return nil
+	}
+	before, err := notes.Read(brainDir, path)
+	if err != nil {
+		// Let notes.Edit itself produce the real error (missing file, etc.)
+		// — this function's job is the envelope, not read failures.
+		return nil
+	}
+	// No gate on where old_str falls relative to the frontmatter fence:
+	// round 2 found that requiring old_str to be fully contained in the
+	// extracted block was itself bypassable by an old_str disambiguated
+	// across the closing "---" into the body. Simpler and bypass-proof:
+	// always compute what the edit would produce and validate that
+	// resulting state's envelope. A body-only edit leaves the frontmatter
+	// (and thus the validation outcome) unchanged, so this is a no-op for
+	// the common case and fail-closed for every case that touches the
+	// envelope, regardless of how old_str is phrased.
+	_, hadFence := frontmatterBlock(string(before))
+	after := strings.Replace(string(before), oldStr, newStr, 1)
+	_, hasFence := frontmatterBlock(after)
+	if hadFence && !hasFence {
+		// Round 3: an edit that drops the closing fence degrades `after`
+		// to "unfenced" — frontmatterScalars then sees an empty map and
+		// ValidateEnvelope({}) is nil by design (absent fields are valid),
+		// so an invalid value would otherwise land with zero error while
+		// also corrupting the note's structure. A previously-fenced note
+		// must stay fenced, full stop.
+		return fmt.Errorf("edit would remove the frontmatter fence")
+	}
+	return claim.ValidateEnvelope(frontmatterScalars(after))
+}
+
+// frontmatterBlock returns the raw text between doc's opening and closing
+// `---` fences, or ok=false if doc has no (properly closed) fence.
+func frontmatterBlock(doc string) (block string, ok bool) {
+	// hyperguild#138: fence detection itself is frontmatter.Split, shared
+	// with internal/api and internal/frontmatter — the CRLF/BOM guards that
+	// used to live here (added piecemeal across rounds 4 and 5 of #123's
+	// review) are now the shared parser's job, so every caller inherits a
+	// fix instead of needing bug-for-bug parity edits.
+	b, _, ok := frontmatter.Split([]byte(doc))
+	if !ok {
+		return "", false
+	}
+	// Split's block keeps the "\n" immediately before the closing fence
+	// (by design — see its own doc comment); this function never included
+	// it. Split guarantees ok=true only when "\n---\n" matched, so this is
+	// always exactly one byte, never ambiguous.
+	return strings.TrimSuffix(string(b), "\n"), true
+}
+
+// frontmatterScalars extracts top-level "key: value" scalar pairs from
+// doc's leading fence block, for the claim-envelope check only — not a
+// general frontmatter parser. Indented lines (YAML block-list items,
+// wrapped values) are skipped rather than misparsed as keys, same fix as
+// hyperguild#126/#128 in the sibling packages this mirrors.
+func frontmatterScalars(doc string) map[string]string {
+	out := map[string]string{}
+	block, ok := frontmatterBlock(doc)
+	if !ok {
+		return out
+	}
+	lines := strings.Split(block, "\n")
+	for i := 0; i < len(lines); i++ {
+		line := lines[i]
+		if line != "" && (line[0] == ' ' || line[0] == '\t') {
+			continue
+		}
+		key, val, ok := strings.Cut(line, ":")
+		if !ok {
+			continue
+		}
+		val = strings.TrimSpace(val)
+		if val == "" {
+			// Round 6: a colon with nothing after it is ambiguous — it can
+			// be a genuinely empty/omitted value, or the start of a YAML
+			// block scalar whose real value lives on the indented
+			// continuation line(s) that follow (e.g. "half_life:\n
+			// durable"). Treating the latter as absent let an edit smuggle
+			// an invalid value straight past ValidateEnvelope: the field
+			// read as unset while the disk actually carried a value. Fold
+			// the continuation in as a best-effort join so oneOf() still
+			// sees it. A genuinely empty value (no indented line follows)
+			// still folds to "", preserving present()'s existing
+			// placeholder-not-assertion contract.
+			var cont []string
+			for i+1 < len(lines) {
+				next := lines[i+1]
+				if next == "" || (next[0] != ' ' && next[0] != '\t') {
+					break
+				}
+				cont = append(cont, strings.TrimSpace(next))
+				i++
+			}
+			val = strings.Join(cont, " ")
+		}
+		out[strings.TrimSpace(key)] = val
+	}
+	return out
+}

ingestion/internal/mcp/tools_notes_test.go

@@ -66,8 +66,11 @@ func TestBrainReadAndEdit_RoundTripThroughJSONRPC(t *testing.T) {
 
 	got, err := os.ReadFile(filepath.Join(dir, "wiki/homelab/facts/n.md"))
 	require.NoError(t, err)
-	assert.Equal(t, "---\ntitle: 'n'\n---\n\nalpha\nBETA\n", string(got),
+	// Only the matched bytes change in the body; the one deliberate addition
-		"only the matched bytes may change")
+	// is the editor's provenance stamp (hyperguild#145 — no principal here,
+	// so origin: unknown).
+	assert.Equal(t, "---\ntitle: 'n'\norigin: unknown\n---\n\nalpha\nBETA\n", string(got),
+		"only the matched bytes and the provenance stamp may change")
 }
 
 func TestBrainEdit_EmptyOldStrErrorNamesRawArgumentBytes(t *testing.T) {
@@ -93,6 +96,243 @@ func TestBrainEdit_EmptyOldStrErrorNamesRawArgumentBytes(t *testing.T) {
 	assert.Contains(t, errMsg, "raw arguments were", "%v", errMsg)
 }
 
+func TestBrainEdit_RejectsAnInvalidClaimEnvelopeWrittenViaStringReplace(t *testing.T) {
+	// hyperguild#123: brain_write/brain_update both validate the claim
+	// envelope (half_life/applies/claim_provenance) before writing —
+	// brain_edit didn't, even though it's the one live, model-facing path
+	// that can rewrite an existing envelope line directly via raw string
+	// replace, no parsing involved. "same rules when a note changes as when
+	// it's born" (hyperguild#111's own framing) applies here too.
+	dir := newBrainRepo(t)
+	note := filepath.Join(dir, "wiki/homelab/facts/n.md")
+	require.NoError(t, os.WriteFile(note,
+		[]byte("---\ntitle: 'n'\nhalf_life: durable\napplies: universal\nclaim_provenance: asserted\n---\n\nbody\n"), 0o644))
+	srv := mcp.NewServer(dir, nil, nil, nil)
+
+	resp := call(t, srv, "brain_edit", map[string]any{
+		"path": "wiki/homelab/facts/n.md", "old_str": "claim_provenance: asserted", "new_str": "claim_provenance: guessed",
+	})
+	require.Contains(t, resp, "error", "%v", resp)
+
+	got, err := os.ReadFile(note)
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "claim_provenance: asserted", "rejected edit must leave the note byte-identical")
+}
+
+func TestBrainEdit_RejectsAValueOnlyEditThatBreaksTheEnvelope(t *testing.T) {
+	// Found in review: the original gate (touchesClaimEnvelope) checked
+	// whether old_str/new_str mention the FIELD NAME — but a minimal diff
+	// (the natural shape of any real edit, model-generated or human) can
+	// target just the VALUE token and never mention the field name at all.
+	// "asserted" -> "guessed" on a claim_provenance line walked straight
+	// past the field-name substring check and wrote an invalid enum value
+	// with no error — the exact bypass #123 was supposed to close, closed
+	// in name only.
+	dir := newBrainRepo(t)
+	note := filepath.Join(dir, "wiki/homelab/facts/n.md")
+	require.NoError(t, os.WriteFile(note,
+		[]byte("---\ntitle: 'n'\nhalf_life: durable\napplies: universal\nclaim_provenance: asserted\n---\n\nbody\n"), 0o644))
+	srv := mcp.NewServer(dir, nil, nil, nil)
+
+	resp := call(t, srv, "brain_edit", map[string]any{
+		"path": "wiki/homelab/facts/n.md", "old_str": "asserted", "new_str": "guessed",
+	})
+	require.Contains(t, resp, "error", "%v", resp)
+
+	got, err := os.ReadFile(note)
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "claim_provenance: asserted", "rejected edit must leave the note byte-identical")
+}
+
+func TestBrainEdit_RejectsAnOldStrThatCrossesTheClosingFence(t *testing.T) {
+	// Found in round-2 review: the position-based gate required old_str to
+	// be fully CONTAINED in the extracted frontmatter block (which excludes
+	// both "---" fence lines). An old_str disambiguated by extending past
+	// the closing fence into the body — a natural choice, since notes.Edit
+	// requires old_str to be unique in the file — fails that containment
+	// test, so checkClaimEnvelope skips validation entirely while
+	// notes.Edit still applies the replace verbatim. Same invalid-enum
+	// outcome as the original two bypasses, reached a third way.
+	dir := newBrainRepo(t)
+	note := filepath.Join(dir, "wiki/homelab/facts/n.md")
+	require.NoError(t, os.WriteFile(note,
+		[]byte("---\ntitle: 'n'\nhalf_life: durable\napplies: universal\nclaim_provenance: asserted\n---\n\nbody\n"), 0o644))
+	srv := mcp.NewServer(dir, nil, nil, nil)
+
+	resp := call(t, srv, "brain_edit", map[string]any{
+		"path":    "wiki/homelab/facts/n.md",
+		"old_str": "asserted\n---\n\nbody",
+		"new_str": "guessed\n---\n\nbody",
+	})
+	require.Contains(t, resp, "error", "%v", resp)
+
+	got, err := os.ReadFile(note)
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "claim_provenance: asserted", "rejected edit must leave the note byte-identical")
+}
+
+func TestBrainEdit_RejectsAnEditThatRemovesTheClosingFence(t *testing.T) {
+	// Found in round-3 review: checkClaimEnvelope always validates the
+	// resulting frontmatter of `after` — but an edit whose new_str drops
+	// the closing "---" degrades `after` to "unfenced" in the same call.
+	// frontmatterBlock(after) then returns ok=false, frontmatterScalars
+	// returns an empty map, and claim.ValidateEnvelope({}) is nil by
+	// design (absent fields are valid) — so an invalid enum value lands on
+	// disk with zero error, and the note is left permanently unfenced.
+	// Structural fix: a note that had a valid fence before the edit must
+	// still have one after, or the edit is rejected outright.
+	dir := newBrainRepo(t)
+	note := filepath.Join(dir, "wiki/homelab/facts/n.md")
+	require.NoError(t, os.WriteFile(note,
+		[]byte("---\ntitle: 'n'\nhalf_life: durable\napplies: universal\nclaim_provenance: asserted\n---\n\nbody\n"), 0o644))
+	srv := mcp.NewServer(dir, nil, nil, nil)
+
+	resp := call(t, srv, "brain_edit", map[string]any{
+		"path":    "wiki/homelab/facts/n.md",
+		"old_str": "claim_provenance: asserted\n---\n",
+		"new_str": "claim_provenance: not-a-real-value\n",
+	})
+	require.Contains(t, resp, "error", "%v", resp)
+
+	got, err := os.ReadFile(note)
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "claim_provenance: asserted\n---\n", "rejected edit must leave the note byte-identical, fence intact")
+}
+
+func TestBrainEdit_RejectsAnInvalidEnvelopeOnACRLFFencedNote(t *testing.T) {
+	// Found in round-4 review: frontmatterBlock's fence detection matches
+	// the literal byte sequence "---\n" / "\n---\n". A note whose fence
+	// lines use CRLF ("---\r\n") fails strings.HasPrefix(doc, "---\n") on
+	// the BEFORE read, so hadFence is false — not because the fence is
+	// missing, but because \r sits in front of every \n. hadFence&&!hasFence
+	// can then never fire, frontmatterScalars falls back to an empty map,
+	// and claim.ValidateEnvelope({}) is nil by design. No adversarial
+	// old_str/new_str crafting needed: encoding alone silently disables the
+	// whole envelope check for this note. Zero CRLF-fenced notes exist in
+	// the live corpus today, but nothing in the code prevents one.
+	dir := newBrainRepo(t)
+	note := filepath.Join(dir, "wiki/homelab/facts/n.md")
+	require.NoError(t, os.WriteFile(note,
+		[]byte("---\r\ntitle: 'n'\r\nhalf_life: durable\r\napplies: universal\r\nclaim_provenance: asserted\r\n---\r\n\r\nbody\r\n"), 0o644))
+	srv := mcp.NewServer(dir, nil, nil, nil)
+
+	resp := call(t, srv, "brain_edit", map[string]any{
+		"path": "wiki/homelab/facts/n.md", "old_str": "asserted", "new_str": "guessed",
+	})
+	require.Contains(t, resp, "error", "%v", resp)
+
+	got, err := os.ReadFile(note)
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "claim_provenance: asserted", "rejected edit must leave the note byte-identical")
+}
+
+func TestBrainEdit_RejectsAnInvalidEnvelopeOnABOMPrefixedNote(t *testing.T) {
+	// Found in round-5 review: the same "encoding property empties
+	// frontmatterScalars's map" mechanism as the CRLF bypass, one layer
+	// earlier — a leading UTF-8 BOM (EF BB BF) defeats
+	// strings.HasPrefix(doc, "---\n") exactly like CRLF did, before that
+	// prefix is even reached. Notepad's default "UTF-8" save and
+	// PowerShell's pre-v6 Out-File/Set-Content both emit a BOM, so this is
+	// a live, plausible authoring path, not an exotic one — same severity
+	// and same one-line cost as the CRLF fix, fixed the same way rather
+	// than deferred to hyperguild#138.
+	dir := newBrainRepo(t)
+	note := filepath.Join(dir, "wiki/homelab/facts/n.md")
+	require.NoError(t, os.WriteFile(note,
+		[]byte("\xef\xbb\xbf---\ntitle: 'n'\nhalf_life: durable\napplies: universal\nclaim_provenance: asserted\n---\n\nbody\n"), 0o644))
+	srv := mcp.NewServer(dir, nil, nil, nil)
+
+	resp := call(t, srv, "brain_edit", map[string]any{
+		"path": "wiki/homelab/facts/n.md", "old_str": "asserted", "new_str": "guessed",
+	})
+	require.Contains(t, resp, "error", "%v", resp)
+
+	got, err := os.ReadFile(note)
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "claim_provenance: asserted", "rejected edit must leave the note byte-identical")
+}
+
+func TestBrainEdit_RejectsAFoldedScalarThatHidesAnInvalidValue(t *testing.T) {
+	// Found in round-6 review: a different mechanism from the encoding
+	// family (rounds 1-6 were all about fence detection; this is the field
+	// extractor). old_str="half_life: durable", new_str="half_life:\n
+	// garbage-value" turns the field into a YAML block-scalar shape: the
+	// top-level line is now "half_life:" with an empty inline value, and
+	// the real value lives on the indented continuation line that follows.
+	// frontmatterScalars's indentation guard skips that continuation line
+	// outright, so the field reads as present-with-empty-value —
+	// present()'s own contract then treats that as absent (a placeholder,
+	// not an assertion) — and claim.ValidateEnvelope never sees the
+	// invalid value at all. No encoding quirk needed: one ordinary
+	// brain_edit call smuggles an out-of-enum value straight past the
+	// check the field was supposed to be validated by.
+	dir := newBrainRepo(t)
+	note := filepath.Join(dir, "wiki/homelab/facts/n.md")
+	require.NoError(t, os.WriteFile(note,
+		[]byte("---\ntitle: 'n'\nhalf_life: durable\napplies: universal\nclaim_provenance: asserted\n---\n\nbody\n"), 0o644))
+	srv := mcp.NewServer(dir, nil, nil, nil)
+
+	resp := call(t, srv, "brain_edit", map[string]any{
+		"path":    "wiki/homelab/facts/n.md",
+		"old_str": "half_life: durable",
+		"new_str": "half_life:\n  garbage-value",
+	})
+	require.Contains(t, resp, "error", "%v", resp)
+
+	got, err := os.ReadFile(note)
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "half_life: durable", "rejected edit must leave the note byte-identical")
+}
+
+func TestBrainEdit_AllowsAValidClaimEnvelopeEdit(t *testing.T) {
+	dir := newBrainRepo(t)
+	note := filepath.Join(dir, "wiki/homelab/facts/n.md")
+	require.NoError(t, os.WriteFile(note,
+		[]byte("---\ntitle: 'n'\nhalf_life: durable\napplies: universal\nclaim_provenance: asserted\n---\n\nbody\n"), 0o644))
+	srv := mcp.NewServer(dir, nil, nil, nil)
+
+	resp := call(t, srv, "brain_edit", map[string]any{
+		"path": "wiki/homelab/facts/n.md", "old_str": "half_life: durable", "new_str": "half_life: seasonal",
+	})
+	require.NotContains(t, resp, "error", "%v", resp)
+
+	got, err := os.ReadFile(note)
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "half_life: seasonal")
+}
+
+func TestBrainEdit_UnrelatedEditsSkipTheEnvelopeCheckEntirely(t *testing.T) {
+	// The gate only engages when old_str/new_str actually mention an
+	// envelope field name — an ordinary body edit on a note that happens to
+	// carry a valid envelope must not pay for (or be affected by) a check
+	// that has nothing to do with it.
+	dir := newBrainRepo(t)
+	note := filepath.Join(dir, "wiki/homelab/facts/n.md")
+	require.NoError(t, os.WriteFile(note,
+		[]byte("---\ntitle: 'n'\nhalf_life: durable\napplies: universal\nclaim_provenance: asserted\n---\n\nold body\n"), 0o644))
+	srv := mcp.NewServer(dir, nil, nil, nil)
+
+	resp := call(t, srv, "brain_edit", map[string]any{
+		"path": "wiki/homelab/facts/n.md", "old_str": "old body", "new_str": "new body",
+	})
+	require.NotContains(t, resp, "error", "%v", resp)
+
+	got, err := os.ReadFile(note)
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "new body")
+}
+
+func TestBrainEditRoot_GovernanceFilesAreNeverEnvelopeChecked(t *testing.T) {
+	// CLAUDE.md has no claim-envelope concept at all — the check must be
+	// scoped to notes (ScopeNotes), never applied on the governance path.
+	srv, _, _, _ := govServer(t)
+
+	resp := authCall(t, srv, "Bearer "+capStaticTok, "brain_edit_root", map[string]any{
+		"path": "CLAUDE.md", "old_str": "# rules", "new_str": "half_life: durable",
+	})
+	require.NotContains(t, resp, "error", "%v", resp)
+}
+
 func TestBrainEdit_RefusesGovernanceFilesFromTheModelFacingTool(t *testing.T) {
 	dir := newBrainRepo(t)
 	srv := mcp.NewServer(dir, nil, nil, nil)

ingestion/internal/notes/edit.go

@@ -5,6 +5,7 @@ import (
 	"encoding/hex"
 	"errors"
 	"fmt"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
 	"os"
 	"path/filepath"
 	"strings"
@@ -71,14 +72,18 @@ func ReadScoped(brainDir, path string, scope Scope) ([]byte, error) {
 }
 
 func readContained(t Target) ([]byte, error) {
-	fi, err := os.Stat(t.Abs)
+	// Through the brain root, regular files only, size checked on the opened
+	// handle (hyperguild#157): Resolve's Lstat could be raced by a swap, and
+	// os.ReadFile blocked on a FIFO.
+	bfs, err := brainfs.Open(t.Brain)
 	if err != nil {
-		return nil, fmt.Errorf("notes: stat %s: %w", t.Rel, err)
+		return nil, fmt.Errorf("notes: %w", err)
 	}
-	if fi.Size() > maxNoteBytes {
+	defer func() { _ = bfs.Close() }()
-		return nil, fmt.Errorf("%w: %s is %d bytes (limit %d)", ErrTooLarge, t.Rel, fi.Size(), maxNoteBytes)
+	b, err := bfs.ReadRegularMax(t.Rel, maxNoteBytes)
+	if errors.Is(err, brainfs.ErrTooLarge) {
+		return nil, fmt.Errorf("%w: %s (limit %d)", ErrTooLarge, t.Rel, maxNoteBytes)
 	}
-	b, err := os.ReadFile(t.Abs)
 	if err != nil {
 		return nil, fmt.Errorf("notes: read %s: %w", t.Rel, err)
 	}

ingestion/internal/notes/path.go

@@ -58,8 +58,9 @@ var (
 
 // Target is a resolved, contained path.
 type Target struct {
-	Rel string // brain-relative, cleaned
+	Rel   string // brain-relative, cleaned
-	Abs string // absolute, symlink-checked
+	Abs   string // absolute, symlink-checked
+	Brain string // the brain root Rel is relative to
 }
 
 // Resolve canonicalises path, then checks it against the scope's allowlist,
@@ -109,7 +110,7 @@ func Resolve(brainDir, path string, scope Scope) (Target, error) {
 		return Target{}, err
 	}
 
-	return Target{Rel: clean, Abs: abs}, nil
+	return Target{Rel: clean, Abs: abs, Brain: brainDir}, nil
 }
 
 // allow enforces the scope's allowlist. The two scopes are DISJOINT, not

ingestion/internal/notes/read_root_test.go

@@ -0,0 +1,40 @@
+package notes
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs/brainfstest"
+)
+
+// hyperguild#157 slice 2: ReadScoped (brain_read) Lstat-checked the final
+// component, then reopened by name with os.ReadFile: a swap after the check
+// was followed, and a FIFO blocked the read. It now reads through brainfs.
+func TestReadScopedRefusesSymlinksAndSurvivesSwapRaces(t *testing.T) {
+	brain := t.TempDir()
+	facts := filepath.Join(brain, "wiki", "w", "facts")
+	require.NoError(t, os.MkdirAll(facts, 0o755))
+	p := filepath.Join(facts, "r.md")
+	read := func() string {
+		b, _ := ReadScoped(brain, "wiki/w/facts/r.md", ScopeNotes)
+		return string(b)
+	}
+	require.NoError(t, os.WriteFile(p, []byte("inside"), 0o644))
+	assert.Equal(t, "inside", read())
+	brainfstest.AssertNoLeak(t, p, "inside", 1500*time.Millisecond, read)
+	brainfstest.AssertNoHang(t, p, "inside", 1500*time.Millisecond, 6*time.Second, func() { _ = read() })
+}
+
+func TestReadScopedRefusesANoteOverMaxNoteBytes(t *testing.T) {
+	brain := t.TempDir()
+	facts := filepath.Join(brain, "wiki", "w", "facts")
+	require.NoError(t, os.MkdirAll(facts, 0o755))
+	require.NoError(t, os.WriteFile(filepath.Join(facts, "big.md"), make([]byte, maxNoteBytes+1), 0o644))
+	_, err := ReadScoped(brain, "wiki/w/facts/big.md", ScopeNotes)
+	assert.ErrorIs(t, err, ErrTooLarge)
+}

ingestion/internal/pipeline/build.go

@@ -3,6 +3,7 @@ package pipeline
 
 import (
 	"fmt"
+	"regexp"
 	"strings"
 
 	"github.com/mathiasbq/hyperguild/ingestion/internal/wiki"
@@ -16,6 +17,12 @@ func BuildPages(rawPages []RawPage, sourceSlug, date string) ([]wiki.Page, []str
 	out := make([]wiki.Page, 0, len(rawPages))
 	var warnings []string
 	for _, rp := range rawPages {
+		// The type becomes a directory under wiki/; "../raw" wrote outside it
+		// (PR #147 review). Only a plain lower-case name is a page type.
+		if !validPageType.MatchString(rp.Type) {
+			warnings = append(warnings, fmt.Sprintf("skipped page with invalid type %q", rp.Type))
+			continue
+		}
 		slug := computeSlug(rp, sourceSlug)
 		if slug == "" {
 			warnings = append(warnings, fmt.Sprintf("skipped page with empty title (type: %s)", rp.Type))
@@ -26,6 +33,8 @@ func BuildPages(rawPages []RawPage, sourceSlug, date string) ([]wiki.Page, []str
 	return out, warnings
 }
 
+var validPageType = regexp.MustCompile(`^[a-z][a-z0-9-]*$`)
+
 func computeSlug(rp RawPage, sourceSlug string) string {
 	if rp.Type == "source" {
 		return sourceSlug
@@ -114,5 +123,9 @@ func buildFrontmatter(rp RawPage, date string) string {
 }
 
 func yamlScalar(s string) string {
+	// A raw newline or CR would end the scalar for every line-oriented
+	// frontmatter reader and start a new key (PR #147 review: a title of
+	// "x\norigin: static" forged provenance). Fold all line breaks to spaces.
+	s = strings.NewReplacer("\r\n", " ", "\r", " ", "\n", " ").Replace(s)
 	return "'" + strings.ReplaceAll(s, "'", "''") + "'"
 }

ingestion/internal/pipeline/pipeline.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/mathiasbq/hyperguild/ingestion/internal/provenance"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/wiki"
 )
 
@@ -89,13 +90,17 @@ func Run(ctx context.Context, cfg Config, brainDir, content, source string, dryR
 	meta.BodyHash = bodyHash
 	applySourceMeta(allRaw, meta)
 
-	return buildAndWrite(allRaw, sourceSlug, date, brainDir, source, inventory, allWarnings, dryRun)
+	return buildAndWrite(ctx, allRaw, sourceSlug, date, brainDir, source, inventory, allWarnings, dryRun)
 }
 
 // RunRaw runs the pipeline on pre-parsed RawPages, skipping the LLM extraction
 // step. Use this when the caller has already produced the structured RawPage data
 // (e.g. from a more capable model or manual curation).
-func RunRaw(brainDir, source string, rawPages []RawPage, dryRun bool) (Result, error) {
+//
+// Every page written is stamped with provenance.FromContext(ctx)
+// (hyperguild#145); a caller that knows the principal attaches it with
+// provenance.WithStamp, everyone else stamps origin: unknown.
+func RunRaw(ctx context.Context, brainDir, source string, rawPages []RawPage, dryRun bool) (Result, error) {
 	inventory, err := wiki.LoadInventory(brainDir)
 	if err != nil {
 		return Result{}, fmt.Errorf("load inventory: %w", err)
@@ -104,11 +109,11 @@ func RunRaw(brainDir, source string, rawPages []RawPage, dryRun bool) (Result, e
 	sourceSlug := wiki.Slug(source)
 	date := time.Now().UTC().Format("2006-01-02")
 
-	return buildAndWrite(rawPages, sourceSlug, date, brainDir, source, inventory, nil, dryRun)
+	return buildAndWrite(ctx, rawPages, sourceSlug, date, brainDir, source, inventory, nil, dryRun)
 }
 
 // buildAndWrite runs BuildPages through write for both Run and RunRaw.
-func buildAndWrite(rawPages []RawPage, sourceSlug, date, brainDir, source string, inventory map[wiki.PageType][]wiki.Entry, warnings []string, dryRun bool) (Result, error) {
+func buildAndWrite(ctx context.Context, rawPages []RawPage, sourceSlug, date, brainDir, source string, inventory map[wiki.PageType][]wiki.Entry, warnings []string, dryRun bool) (Result, error) {
 	pages, buildWarnings := BuildPages(rawPages, sourceSlug, date)
 	warnings = append(warnings, buildWarnings...)
 	resolved := Resolve(pages, inventory)
@@ -136,7 +141,13 @@ func buildAndWrite(rawPages []RawPage, sourceSlug, date, brainDir, source string
 					"%s: source now disagrees on section %q — on-disk version kept",
 					page.Path, heading))
 			}
-			if err := os.WriteFile(dest, []byte(content), 0o644); err != nil {
+			// Stamped as the last step, after merge/revise, so a page that
+			// was merged into is re-attributed to this ingest too.
+			stamped, err := provenance.Apply(content, provenance.FromContext(ctx))
+			if err != nil {
+				return Result{}, fmt.Errorf("stamp %s: %w", page.Path, err)
+			}
+			if err := os.WriteFile(dest, []byte(stamped), 0o644); err != nil {
 				return Result{}, fmt.Errorf("write %s: %w", page.Path, err)
 			}
 		}

ingestion/internal/pipeline/pipeline_test.go

@@ -196,7 +196,7 @@ A book about shaping product work.
 Read this before the next planning cycle.
 `), 0o644))
 
-	_, err := RunRaw(dir, "shape-up", []RawPage{{
+	_, err := RunRaw(context.Background(), dir, "shape-up", []RawPage{{
 		Title: "Shape Up", Type: "source", Subtype: "book", Domain: "product-strategy",
 		Content: "## Summary\n\nA book about shaping product work.\n\n## Key Claims\n\n- Appetite beats estimation.\n",
 	}}, false)
@@ -221,12 +221,12 @@ func TestRunRaw_ReIngestingUnchangedContentIsByteIdentical(t *testing.T) {
 		Content: "## Summary\n\nA book about shaping product work.\n\n## Open Questions\n\n- Does appetite scale?\n",
 	}}
 
-	_, err := RunRaw(dir, "shape-up", raw, false)
+	_, err := RunRaw(context.Background(), dir, "shape-up", raw, false)
 	require.NoError(t, err)
 	first, err := os.ReadFile(filepath.Join(dir, "wiki", "sources", "shape-up.md"))
 	require.NoError(t, err)
 
-	_, err = RunRaw(dir, "shape-up", raw, false)
+	_, err = RunRaw(context.Background(), dir, "shape-up", raw, false)
 	require.NoError(t, err)
 	second, err := os.ReadFile(filepath.Join(dir, "wiki", "sources", "shape-up.md"))
 	require.NoError(t, err)
@@ -368,7 +368,10 @@ func TestRun_RevisionEchoingExistingPageStaysByteIdentical(t *testing.T) {
 	require.NoError(t, err)
 
 	want := "---\ntitle: 'Shape Up'\nlast_updated: " + time.Now().UTC().Format("2006-01-02") +
-		"\nsource_hash: " + hashBody(content) + "\n---\n\n" +
+		"\nsource_hash: " + hashBody(content) +
+		// Every page an ingest writes carries provenance (hyperguild#145);
+		// no stamp in ctx here, so origin: unknown.
+		"\norigin: unknown\n---\n\n" +
 		"## Summary\n\nA book about shaping product work.\n\n" +
 		"## Key Claims\n\n- Appetite beats estimation.\n"
 	assert.Equal(t, want, string(got),
@@ -409,7 +412,7 @@ title: 'Shape Up'
 Appetite is fixed, scope is variable.
 `), 0o644))
 
-	res, err := RunRaw(dir, "shape-up", []RawPage{{
+	res, err := RunRaw(context.Background(), dir, "shape-up", []RawPage{{
 		Title: "Shape Up", Type: "source", Subtype: "book", Domain: "product",
 		Content: "## Summary\n\nAppetite is negotiable and scope is fixed.\n",
 	}}, false)

ingestion/internal/provenance/provenance.go

@@ -0,0 +1,226 @@
+// Package provenance stamps server-owned write provenance (hyperguild#145)
+// into a brain note's frontmatter: origin (static | jwt | unknown) and
+// written_by (the authenticated principal), so a reader can discount what a
+// connector session wrote after reading an untrusted page.
+//
+// The control is a post-condition applied by every write path a model can
+// reach. Two review rounds on PR #147 showed that deciding line by line which
+// lines are provenance loses to YAML's context-dependent features — an alias
+// key resolves only against an anchor elsewhere, and a `...` line ends the
+// document before the stamp. So Apply does not try to recognise provenance.
+// It keeps only frontmatter it can prove is plain:
+//
+//   - a top-level line `key: value` whose key is a bare identifier,
+//   - together with that key's continuation lines (indented, or `- ` items
+//     after an empty value),
+//   - where the group decodes ON ITS OWN, with yaml.v3, to a mapping with
+//     exactly that one key,
+//   - and the key is not origin/written_by and has not been seen before.
+//
+// Everything else — aliases, anchors used as keys, document markers, complex
+// keys, merge keys, flow maps, tags, quoted keys, duplicates — is dropped.
+// Then the stamp is appended and the whole result is decoded by yaml.v3 as a
+// backstop: if it does not decode to exactly the stamped values, Apply fails
+// and the caller refuses the write.
+package provenance
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"regexp"
+	"strings"
+
+	"gopkg.in/yaml.v3"
+
+	sharedfm "github.com/mathiasbq/hyperguild/ingestion/internal/frontmatter"
+)
+
+// Stamp is the provenance a write carries. An empty Origin means "unknown".
+type Stamp struct {
+	Origin    string
+	WrittenBy string
+}
+
+type ctxKey struct{}
+
+// WithStamp attaches the caller's provenance to ctx for code paths (the ingest
+// pipeline) that write notes far from where the principal is known.
+func WithStamp(ctx context.Context, s Stamp) context.Context {
+	return context.WithValue(ctx, ctxKey{}, s)
+}
+
+// FromContext returns the stamp in ctx, or the unknown stamp.
+func FromContext(ctx context.Context) Stamp {
+	if s, ok := ctx.Value(ctxKey{}).(Stamp); ok {
+		return s
+	}
+	return Stamp{}
+}
+
+// ErrUnverifiable means the stamped note would not read back as stamped.
+var ErrUnverifiable = errors.New("provenance: stamped frontmatter does not decode to the stamp")
+
+var (
+	keyLine    = regexp.MustCompile(`^([A-Za-z_][A-Za-z0-9_.-]*)[ ]*:(?:[ ]|$)(.*)$`)
+	bareScalar = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._@-]*$`)
+	reserved   = map[string]bool{"origin": true, "written_by": true}
+)
+
+func (s Stamp) origin() string {
+	if s.Origin == "" {
+		return "unknown"
+	}
+	return s.Origin
+}
+
+// Apply returns content with its frontmatter reduced to plain groups and the
+// stamp appended. Content without frontmatter gains a block.
+func Apply(content string, s Stamp) (string, error) {
+	stamp := "origin: " + scalar(s.origin()) + "\n"
+	if s.WrittenBy != "" {
+		stamp += "written_by: " + scalar(s.WrittenBy) + "\n"
+	}
+	content = foldFrontmatterCR(content)
+	block, rest, ok := sharedfm.Split([]byte(content))
+	var out string
+	switch {
+	case !ok && strings.HasPrefix(strings.ReplaceAll(content, "\r\n", "\n"), "---\n"):
+		// A fence was opened but cannot be closed (e.g. a "---x" line).
+		// Prepending a second block would demote the original frontmatter
+		// into the body, so refuse instead (PR #147 review round 3).
+		return "", fmt.Errorf("%w: unclosed frontmatter fence", ErrUnverifiable)
+	case !ok:
+		out = "---\n" + stamp + "---\n" + content
+	default:
+		out = "---\n" + plainGroups(string(block)) + stamp + "---\n" + strings.TrimPrefix(string(rest), "\n")
+	}
+	if err := verify(out, s); err != nil {
+		return "", err
+	}
+	return out, nil
+}
+
+// ApplyFile applies the stamp to the note at absPath in place.
+func ApplyFile(absPath string, s Stamp) error {
+	b, err := os.ReadFile(absPath)
+	if err != nil {
+		return fmt.Errorf("read for provenance: %w", err)
+	}
+	out, err := Apply(string(b), s)
+	if err != nil {
+		return err
+	}
+	if out == string(b) {
+		return nil
+	}
+	if err := os.WriteFile(absPath, []byte(out), 0o644); err != nil {
+		return fmt.Errorf("write provenance: %w", err)
+	}
+	return nil
+}
+
+// plainGroups keeps the provably plain key groups of a frontmatter block.
+func plainGroups(block string) string {
+	lines := strings.Split(strings.TrimSuffix(block, "\n"), "\n")
+	seen := map[string]bool{}
+	var b strings.Builder
+	for i := 0; i < len(lines); {
+		line := lines[i]
+		m := keyLine.FindStringSubmatch(line)
+		if m == nil {
+			i++ // not a plain key line: dropped, as is anything it would govern
+			for i < len(lines) && isContinuation(lines[i], "") {
+				i++
+			}
+			continue
+		}
+		key, value := m[1], strings.TrimSpace(m[2])
+		j := i + 1
+		for j < len(lines) && isContinuation(lines[j], value) {
+			j++
+		}
+		group := strings.Join(lines[i:j], "\n") + "\n"
+		lk := strings.ToLower(key)
+		if !reserved[lk] && !seen[lk] && decodesToOnly(group, key) {
+			seen[lk] = true
+			b.WriteString(group)
+		}
+		i = j
+	}
+	return b.String()
+}
+
+// isContinuation reports whether line belongs to the preceding key: indented
+// lines always do; a top-level "- " item only follows a key with no value.
+func isContinuation(line, value string) bool {
+	if line == "" {
+		return false
+	}
+	if line[0] == ' ' {
+		return true
+	}
+	return value == "" && strings.HasPrefix(line, "- ")
+}
+
+func decodesToOnly(group, key string) bool {
+	var m map[string]any
+	if err := yaml.Unmarshal([]byte(group), &m); err != nil {
+		return false
+	}
+	_, ok := m[key]
+	return ok && len(m) == 1
+}
+
+func verify(doc string, s Stamp) error {
+	block, _, ok := sharedfm.Split([]byte(doc))
+	if !ok {
+		return ErrUnverifiable
+	}
+	var m map[string]any
+	if err := yaml.Unmarshal(block, &m); err != nil {
+		return fmt.Errorf("%w: %v", ErrUnverifiable, err)
+	}
+	if m["origin"] != s.origin() {
+		return ErrUnverifiable
+	}
+	if s.WrittenBy == "" {
+		if _, has := m["written_by"]; has {
+			return ErrUnverifiable
+		}
+	} else if m["written_by"] != s.WrittenBy {
+		return ErrUnverifiable
+	}
+	return nil
+}
+
+// foldFrontmatterCR turns CRLF and lone CR inside a leading frontmatter block
+// into LF, so every reader agrees on where lines end.
+func foldFrontmatterCR(content string) string {
+	s := strings.ReplaceAll(content, "\r\n", "\n")
+	if !strings.HasPrefix(s, "---\n") {
+		return content
+	}
+	end := strings.Index(s[4:], "\n---")
+	if end < 0 {
+		return content
+	}
+	return strings.ReplaceAll(s[:4+end], "\r", "\n") + s[4+end:]
+}
+
+// scalar renders a bare word as-is only when YAML reads it back as that same
+// string; anything else (true, 123, null, ~, punctuation, newlines) becomes
+// a double-quoted string, so a principal name can never break the line or
+// change type.
+func scalar(v string) string {
+	if bareScalar.MatchString(v) {
+		var back any
+		if yaml.Unmarshal([]byte(v), &back) == nil {
+			if s, ok := back.(string); ok && s == v {
+				return v
+			}
+		}
+	}
+	return fmt.Sprintf("%q", v)
+}

ingestion/internal/provenance/provenance_test.go

@@ -0,0 +1,86 @@
+package provenance
+
+import (
+	"errors"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gopkg.in/yaml.v3"
+)
+
+func fmOf(t *testing.T, doc string) map[string]any {
+	t.Helper()
+	parts := strings.SplitN(doc, "---\n", 3)
+	require.Len(t, parts, 3, doc)
+	var m map[string]any
+	require.NoError(t, yaml.Unmarshal([]byte(parts[1]), &m), parts[1])
+	return m
+}
+
+// The whole-document backstop: a stamp that would not read back as written
+// is refused, never written. A principal with an invalid UTF-8 byte quotes
+// to "\xff", which YAML decodes as U+00FF, so it cannot round-trip.
+func TestApplyRefusesAStampThatDoesNotReadBack(t *testing.T) {
+	_, err := Apply("---\ntitle: t\n---\nbody\n", Stamp{Origin: "jwt", WrittenBy: "bad\xff"})
+	assert.True(t, errors.Is(err, ErrUnverifiable), "got %v", err)
+}
+
+// A principal that YAML would decode as a non-string (true, 123, null) is
+// quoted, so the stamp reads back as the same string.
+func TestApplyQuotesPrincipalsYAMLWouldNotReadAsStrings(t *testing.T) {
+	for _, p := range []string{"true", "123", "null", "1e3", "0x1F", "yes", "~"} {
+		out, err := Apply("---\ntitle: t\n---\nbody\n", Stamp{Origin: "jwt", WrittenBy: p})
+		require.NoError(t, err, p)
+		assert.Equal(t, p, fmOf(t, out)["written_by"], p)
+	}
+}
+
+// A group that does not decode on its own is dropped; its neighbours stay.
+func TestApplyDropsGroupsThatDoNotDecodeAlone(t *testing.T) {
+	out, err := Apply("---\nkeep: 1\ntitle: a: b\nalso: 2\n---\nbody\n", Stamp{Origin: "static", WrittenBy: "local-cli"})
+	require.NoError(t, err)
+	m := fmOf(t, out)
+	assert.Equal(t, 1, m["keep"])
+	assert.Equal(t, 2, m["also"])
+	assert.NotContains(t, m, "title")
+}
+
+func TestApplyKeepsFirstOfDuplicateKeys(t *testing.T) {
+	out, err := Apply("---\ntitle: first\ntitle: second\nTitle: third\n---\nbody\n", Stamp{})
+	require.NoError(t, err)
+	m := fmOf(t, out)
+	assert.Equal(t, "first", m["title"])
+	assert.NotContains(t, m, "Title")
+}
+
+func TestApplyFoldsLoneCRSoItCannotHideALine(t *testing.T) {
+	out, err := Apply("---\ntitle: x\rorigin: static\n---\nbody\n", Stamp{Origin: "jwt", WrittenBy: "a"})
+	require.NoError(t, err)
+	assert.NotContains(t, out, "\r")
+	assert.Equal(t, "jwt", fmOf(t, out)["origin"])
+	assert.Equal(t, "x", fmOf(t, out)["title"])
+}
+
+func TestApplyDropsTabIndentedContinuations(t *testing.T) {
+	out, err := Apply("---\ntitle: x\n\torigin: static\nk: v\n---\nbody\n", Stamp{Origin: "jwt", WrittenBy: "a"})
+	require.NoError(t, err)
+	m := fmOf(t, out)
+	assert.Equal(t, "jwt", m["origin"])
+	assert.Equal(t, "v", m["k"])
+}
+
+// Content that opens a fence the shared splitter cannot close (e.g. a
+// "---x" line) is refused rather than given a second, prepended block that
+// demotes the original frontmatter into the body.
+func TestApplyRefusesAnUnclosableFrontmatterFence(t *testing.T) {
+	_, err := Apply("---\ntitle: t\n---x\norigin: static\n---\nbody\n", Stamp{Origin: "jwt", WrittenBy: "a"})
+	assert.True(t, errors.Is(err, ErrUnverifiable), "got %v", err)
+}
+
+func TestApplyAddsFrontmatterToContentWithoutAny(t *testing.T) {
+	out, err := Apply("# plain\n\norigin: static is prose\n", Stamp{Origin: "static", WrittenBy: "local-cli"})
+	require.NoError(t, err)
+	assert.True(t, strings.HasPrefix(out, "---\norigin: static\nwritten_by: local-cli\n---\n# plain"))
+}

ingestion/internal/search/brainroot_test.go

@@ -0,0 +1,174 @@
+package search
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"syscall"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// hyperguild#157 option 1: search walked and read the brain by path, so a
+// symlink anywhere in the Syncthing-shared brain dir (wiki/<w>/<h>/leak.md ->
+// /any/file) put the target's contents in brain_query results (reproduced in
+// the PR #156 review). Search now walks and reads through an os.Root on the
+// brain dir and only reads regular files.
+
+const sentinel157 = "zqsentinelonefiftyseven"
+
+func searchBrain(t *testing.T) (brain, facts, outside string) {
+	t.Helper()
+	brain = t.TempDir()
+	facts = filepath.Join(brain, "wiki", "w", "facts")
+	require.NoError(t, os.MkdirAll(facts, 0o755))
+	require.NoError(t, os.MkdirAll(filepath.Join(brain, "knowledge"), 0o755))
+	outside = filepath.Join(t.TempDir(), "secret.md")
+	require.NoError(t, os.WriteFile(outside, []byte("# secret\n\n"+sentinel157), 0o644))
+	return brain, facts, outside
+}
+
+func leaked(rs []Result) int {
+	n := 0
+	for _, r := range rs {
+		n += strings.Count(r.Excerpt+r.Title, sentinel157)
+	}
+	return n
+}
+
+func TestQueryDoesNotFollowASymlinkInTheWiki(t *testing.T) {
+	brain, facts, outside := searchBrain(t)
+	require.NoError(t, os.Symlink(outside, filepath.Join(facts, "leak.md")))
+	require.NoError(t, os.WriteFile(filepath.Join(facts, "real.md"), []byte("# real\n\nzqrealnote"), 0o644))
+	rs, err := Query(brain, QueryOptions{Query: sentinel157, Limit: 10})
+	require.NoError(t, err)
+	assert.Zero(t, leaked(rs))
+	rs, err = Query(brain, QueryOptions{Query: "zqrealnote", Limit: 10})
+	require.NoError(t, err)
+	assert.Len(t, rs, 1, "regular notes are still found")
+}
+
+func TestQueryDoesNotFollowASymlinkedDirectory(t *testing.T) {
+	brain, _, outside := searchBrain(t)
+	require.NoError(t, os.Symlink(filepath.Dir(outside), filepath.Join(brain, "wiki", "linked")))
+	rs, err := Query(brain, QueryOptions{Query: sentinel157, Limit: 10})
+	require.NoError(t, err)
+	assert.Zero(t, leaked(rs))
+}
+
+// A search root that is a symlink staying inside the brain (wiki/<w> -> ..)
+// was followed by fs.WalkDir, aliasing raw/ and root files into results
+// (PR #166 review). The root is now Lstat-checked and skipped.
+func TestQueryDoesNotFollowASymlinkedWingRootInsideTheBrain(t *testing.T) {
+	brain, _, _ := searchBrain(t)
+	require.NoError(t, os.MkdirAll(filepath.Join(brain, "raw"), 0o755))
+	require.NoError(t, os.WriteFile(filepath.Join(brain, "raw", "r.md"), []byte("# r\n\nzqrawonly"), 0o644))
+	require.NoError(t, os.Symlink("..", filepath.Join(brain, "wiki", "alias")))
+	rs, err := Query(brain, QueryOptions{Query: "zqrawonly", Wing: "alias", Limit: 10})
+	require.NoError(t, err)
+	assert.Empty(t, rs)
+}
+
+// With a hall the search root is wiki/<wing>/<hall>; a symlinked <wing> with
+// a real <hall> directory under its target was followed (PR #166 round 2).
+func TestQueryDoesNotFollowASymlinkedWingUnderAWingAndHallRoot(t *testing.T) {
+	brain, _, _ := searchBrain(t)
+	require.NoError(t, os.MkdirAll(filepath.Join(brain, "raw", "facts"), 0o755))
+	require.NoError(t, os.WriteFile(filepath.Join(brain, "raw", "facts", "r.md"), []byte("# r\n\nzqrawhall"), 0o644))
+	require.NoError(t, os.Symlink(filepath.Join("..", "raw"), filepath.Join(brain, "wiki", "alias")))
+	rs, err := Query(brain, QueryOptions{Query: "zqrawhall", Wing: "alias", Hall: "facts", Limit: 10})
+	require.NoError(t, err)
+	assert.Empty(t, rs)
+}
+
+// swapInto keeps renaming a regular note, and either a symlink to outside or
+// a FIFO, into path. Each FIFO has a writer held open (as any local process
+// can): a FIFO with no writer reads EOF at once, which would let a reader
+// that skips the handle check pass (PR #161 round 2: with a held writer, a
+// bypass of readOpened hung Query after 5 iterations).
+// startSwap runs swapInto until the test ends and waits for it before
+// t.TempDir's cleanup (hyperguild#162).
+func startSwap(t *testing.T, path, outside string, fifo bool) {
+	t.Helper()
+	var stop atomic.Bool
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() { defer wg.Done(); swapInto(path, outside, fifo, &stop) }()
+	t.Cleanup(func() { stop.Store(true); wg.Wait() })
+}
+
+func swapInto(path, outside string, fifo bool, stop *atomic.Bool) {
+	tmp := path + ".swap"
+	// Writers stay open until the swapper exits, so a reader parked on a
+	// FIFO stays parked (closing one would hand the reader EOF and hide the
+	// hang). Past the fd limit, new FIFOs simply have no writer.
+	var writers []*os.File
+	defer func() {
+		for _, w := range writers {
+			_ = w.Close()
+		}
+	}()
+	for i := 0; !stop.Load(); i++ {
+		_ = os.Remove(tmp)
+		switch {
+		case i%2 == 0:
+			_ = os.WriteFile(tmp, []byte("# r\n\nzqinside "+"zqracenote"), 0o644)
+		case fifo:
+			if err := syscall.Mkfifo(tmp, 0o644); err == nil {
+				if w, err := os.OpenFile(tmp, os.O_RDWR, 0); err == nil {
+					writers = append(writers, w)
+				}
+			}
+		default:
+			_ = os.Symlink(outside, tmp)
+		}
+		_ = os.Rename(tmp, path)
+	}
+}
+
+func TestQueryLeaksNothingUnderASymlinkSwapRace(t *testing.T) {
+	brain, facts, outside := searchBrain(t)
+	startSwap(t, filepath.Join(facts, "r.md"), outside, false)
+	leaks, iters := 0, 0
+	for deadline := time.Now().Add(1500 * time.Millisecond); time.Now().Before(deadline); iters++ {
+		rs, _ := Query(brain, QueryOptions{Query: sentinel157, Limit: 10})
+		leaks += leaked(rs)
+	}
+	if leaks > 0 {
+		t.Fatalf("outside file leaked %d times in %d iterations", leaks, iters)
+	}
+}
+
+func TestQueryDoesNotHangUnderAFIFOSwapRace(t *testing.T) {
+	brain, facts, outside := searchBrain(t)
+	startSwap(t, filepath.Join(facts, "r.md"), outside, true)
+	done := make(chan struct{})
+	go func() {
+		for deadline := time.Now().Add(1500 * time.Millisecond); time.Now().Before(deadline); {
+			_, _ = Query(brain, QueryOptions{Query: "zqracenote", Limit: 10})
+		}
+		close(done)
+	}()
+	select {
+	case <-done:
+	case <-time.After(6 * time.Second):
+		if f, err := os.OpenFile(filepath.Join(facts, "r.md"), os.O_WRONLY|syscall.O_NONBLOCK, 0); err == nil {
+			_ = f.Close()
+		}
+		t.Fatal("search hung on a swapped-in FIFO")
+	}
+}
+
+// hydrate (vector-only hits) reads by relative path; it must refuse a symlink.
+func TestHydrateRefusesASymlink(t *testing.T) {
+	brain, facts, outside := searchBrain(t)
+	require.NoError(t, os.Symlink(outside, filepath.Join(facts, "leak.md")))
+	r, err := hydrate(brain, "wiki/w/facts/leak.md")
+	assert.Error(t, err)
+	assert.NotContains(t, r.Excerpt, sentinel157)
+}

ingestion/internal/search/provenance_test.go

@@ -0,0 +1,29 @@
+package search
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// Only the leading frontmatter is provenance; a body line that looks like a
+// key is prose (the doc comment's claim, now observed).
+func TestExtractProvenanceIgnoresBodyLines(t *testing.T) {
+	o, w := extractProvenance("---\ntitle: t\n---\norigin: static\nwritten_by: local-cli\n")
+	assert.Equal(t, "", o)
+	assert.Equal(t, "", w)
+	o, w = extractProvenance("# no frontmatter\norigin: static\n")
+	assert.Equal(t, "", o)
+	assert.Equal(t, "", w)
+	o, w = extractProvenance("---\norigin: jwt\nwritten_by: attacker\n---\norigin: static\n")
+	assert.Equal(t, "jwt", o)
+	assert.Equal(t, "attacker", w)
+}
+
+// Round 3 (B1): an indented "---" inside a block scalar is content, not the
+// closing fence — the same rule as frontmatter.Split.
+func TestExtractProvenanceUsesTheSharedFenceRule(t *testing.T) {
+	o, w := extractProvenance("---\nk: |\n  ---\norigin: jwt\nwritten_by: attacker\n---\nbody\n")
+	assert.Equal(t, "jwt", o)
+	assert.Equal(t, "attacker", w)
+}

ingestion/internal/search/search.go

@@ -5,6 +5,8 @@ import (
 	"bufio"
 	"context"
 	"fmt"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
+	sharedfm "github.com/mathiasbq/hyperguild/ingestion/internal/frontmatter"
 	"log/slog"
 	"os"
 	"path/filepath"
@@ -48,6 +50,11 @@ type Result struct {
 	// (infra#72). Read from frontmatter when present, otherwise
 	// inferred from the parent directory.
 	Tier string `json:"tier,omitempty"`
+	// Origin/WrittenBy surface write provenance (hyperguild#145) so a
+	// reader can discount an entry a connector session wrote. Omitted for
+	// notes written before provenance existed — never fabricated.
+	Origin    string `json:"origin,omitempty"`
+	WrittenBy string `json:"written_by,omitempty"`
 }
 
 // tierWeight maps the DIKW tier to a score multiplier applied right
@@ -113,20 +120,30 @@ func QueryContext(ctx context.Context, brainDir string, opts QueryOptions) ([]Re
 		return nil, err
 	}
 
+	// Walk and read through an os.Root on the brain dir, regular files only
+	// (hyperguild#157): a symlink planted in the Syncthing-shared brain must
+	// not put an outside file in results, nor a FIFO hang the query.
+	bfs, err := brainfs.Open(brainDir)
+	if err != nil {
+		return nil, fmt.Errorf("search: %w", err)
+	}
+	defer func() { _ = bfs.Close() }()
+
 	var results []Result
 	for _, dir := range roots {
 		if _, statErr := os.Stat(dir); os.IsNotExist(statErr) {
 			continue
 		}
-		err := filepath.WalkDir(dir, func(path string, d os.DirEntry, err error) error {
+		relDir, relErr := bfs.Rel(dir)
-			if err != nil {
+		if relErr != nil {
-				slog.Warn("search: skipping path", "path", path, "err", err)
+			return nil, fmt.Errorf("search: %w", relErr)
+		}
+		err := bfs.WalkRegular(relDir, func(relPath string) error {
+			if !strings.HasSuffix(relPath, ".md") {
 				return nil
 			}
-			if d.IsDir() || !strings.HasSuffix(path, ".md") {
+			path := filepath.Join(brainDir, filepath.FromSlash(relPath))
-				return nil
+			content, err := bfs.ReadRegular(relPath)
-			}
-			content, err := os.ReadFile(path)
 			if err != nil {
 				slog.Warn("search: skipping unreadable file", "path", path, "err", err)
 				return nil
@@ -146,16 +163,22 @@ func QueryContext(ctx context.Context, brainDir string, opts QueryOptions) ([]Re
 			rel = filepath.ToSlash(rel)
 			wing, hall := extractWingHall(string(content), rel)
 			tier := extractTier(string(content), rel)
+			origin, writtenBy := extractProvenance(string(content))
 			results = append(results, Result{
 				Path:    rel,
-				Title:   extractTitle(string(content), d.Name()),
+				Title:   extractTitle(string(content), filepath.Base(relPath)),
 				Excerpt: excerpt(string(content), 300),
 				Score:   score,
 				Wing:    wing,
 				Hall:    hall,
 				Tier:    tier,
+
+				Origin:    origin,
+				WrittenBy: writtenBy,
 			})
 			return nil
+		}, func(p string, err error) {
+			slog.Warn("search: skipping path", "path", p, "err", err)
 		})
 		if err != nil {
 			return nil, err
@@ -265,13 +288,19 @@ func pathInScope(relPath, wing, hall string) bool {
 // excerpt, wing, and hall populated. Used for paths that surface only
 // via vector search.
 func hydrate(brainDir, relPath string) (Result, error) {
-	full := filepath.Join(brainDir, filepath.FromSlash(relPath))
+	// Through the brain root, regular files only (hyperguild#157).
-	content, err := os.ReadFile(full)
+	bfs, err := brainfs.Open(brainDir)
+	if err != nil {
+		return Result{}, err
+	}
+	defer func() { _ = bfs.Close() }()
+	content, err := bfs.ReadRegular(filepath.ToSlash(relPath))
 	if err != nil {
 		return Result{}, err
 	}
 	wing, hall := extractWingHall(string(content), relPath)
 	tier := extractTier(string(content), relPath)
+	origin, writtenBy := extractProvenance(string(content))
 	return Result{
 		Path:    relPath,
 		Title:   extractTitle(string(content), filepath.Base(relPath)),
@@ -279,9 +308,44 @@ func hydrate(brainDir, relPath string) (Result, error) {
 		Wing:    wing,
 		Hall:    hall,
 		Tier:    tier,
+
+		Origin:    origin,
+		WrittenBy: writtenBy,
 	}, nil
 }
 
+// extractProvenance reads origin/written_by from the leading frontmatter
+// block only, located with the shared fence rule (frontmatter.Split: a "---"
+// at column 0) so an indented "---" inside a block scalar is content, not a
+// closing fence (PR #147 review round 3). A body line is never provenance.
+func extractProvenance(content string) (origin, writtenBy string) {
+	block, _, ok := sharedfm.Split([]byte(content))
+	if !ok {
+		return "", ""
+	}
+	for _, line := range strings.Split(string(block), "\n") {
+		if line == "" || line[0] == ' ' || line[0] == '\t' {
+			continue
+		}
+		key, val, found := strings.Cut(line, ":")
+		if !found {
+			continue
+		}
+		v := strings.Trim(strings.TrimSpace(val), `"'`)
+		switch strings.TrimSpace(key) {
+		case "origin":
+			if origin == "" {
+				origin = v
+			}
+		case "written_by":
+			if writtenBy == "" {
+				writtenBy = v
+			}
+		}
+	}
+	return origin, writtenBy
+}
+
 // resolveRoots returns the directories to walk for the given wing/hall
 // filters. Validates hall against the closed vocabulary when set.
 func resolveRoots(brainDir, wing, hall string) ([]string, error) {

ingestion/internal/session/id_test.go

@@ -0,0 +1,49 @@
+package session
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// session_log passed the caller's session_id straight into
+// filepath.Join(sessionsDir, id+".jsonl") and opened it O_CREATE|O_APPEND:
+// path segments in the id created or appended files anywhere the pod could
+// write. The id is now a plain name, and the open does not follow a final
+// symlink.
+func TestAppendRefusesSessionIDsThatAreNotPlainNames(t *testing.T) {
+	root := t.TempDir()
+	dir := filepath.Join(root, "sessions")
+	for _, id := range []string{"../x", "a/b", "/abs", ".", "..", ".hidden", "", "a\\b", "a\x00b"} {
+		assert.Error(t, Append(dir, id, Entry{SessionID: id}), "%q", id)
+	}
+	ents, _ := os.ReadDir(root)
+	for _, e := range ents {
+		assert.Equal(t, "sessions", e.Name(), "nothing created beside the sessions dir")
+	}
+	for _, id := range []string{"1557b2e1-bf0d-5c4f-bbe3-0754d087e356", "_routing", "2026-05-05-infra.plan", "0"} {
+		require.NoError(t, Append(dir, id, Entry{SessionID: id}), "positive control: %q", id)
+	}
+}
+
+func TestAppendDoesNotWriteThroughASymlinkedLog(t *testing.T) {
+	root := t.TempDir()
+	dir := filepath.Join(root, "sessions")
+	require.NoError(t, os.MkdirAll(dir, 0o755))
+	victim := filepath.Join(root, "victim.md")
+	require.NoError(t, os.WriteFile(victim, []byte("untouched\n"), 0o644))
+	require.NoError(t, os.Symlink(filepath.Join("..", "victim.md"), filepath.Join(dir, "s.jsonl")))
+	assert.Error(t, Append(dir, "s", Entry{SessionID: "s"}))
+	got, _ := os.ReadFile(victim)
+	assert.Equal(t, "untouched\n", string(got))
+}
+
+func TestReadRefusesSessionIDsThatAreNotPlainNames(t *testing.T) {
+	root := t.TempDir()
+	require.NoError(t, os.WriteFile(filepath.Join(root, "x.jsonl"), []byte(`{"session_id":"x"}`+"\n"), 0o644))
+	_, err := Read(filepath.Join(root, "sessions"), "../x")
+	assert.Error(t, err)
+}

ingestion/internal/session/session.go

@@ -9,6 +9,8 @@ import (
 	"io/fs"
 	"os"
 	"path/filepath"
+	"regexp"
+	"syscall"
 	"time"
 )
 
@@ -42,13 +44,29 @@ type Attempt struct {
 	RunnerOutput  string `json:"runner_output,omitempty"`
 }
 
+// idPattern is a plain file name: session_log takes the id from the caller,
+// and a path segment in it created or appended files anywhere the pod could
+// write (hyperguild#169).
+var idPattern = regexp.MustCompile(`^[A-Za-z0-9_][A-Za-z0-9._-]{0,127}$`)
+
+func checkID(sessionID string) error {
+	if !idPattern.MatchString(sessionID) {
+		return fmt.Errorf("session id %q is not a plain name", sessionID)
+	}
+	return nil
+}
+
 // Append writes entry as a single JSON line to sessionsDir/{sessionID}.jsonl.
+// The open does not follow a final symlink.
 func Append(sessionsDir, sessionID string, entry Entry) error {
+	if err := checkID(sessionID); err != nil {
+		return err
+	}
 	if err := os.MkdirAll(sessionsDir, 0o755); err != nil {
 		return fmt.Errorf("create sessions dir: %w", err)
 	}
 	path := filepath.Join(sessionsDir, sessionID+".jsonl")
-	f, err := os.OpenFile(path, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0o644)
+	f, err := os.OpenFile(path, os.O_CREATE|os.O_APPEND|os.O_WRONLY|syscall.O_NOFOLLOW|syscall.O_NONBLOCK, 0o644)
 	if err != nil {
 		return fmt.Errorf("open session log: %w", err)
 	}
@@ -70,6 +88,9 @@ func Append(sessionsDir, sessionID string, entry Entry) error {
 
 // Read returns all entries for sessionID. Returns empty slice if no log exists.
 func Read(sessionsDir, sessionID string) ([]Entry, error) {
+	if err := checkID(sessionID); err != nil {
+		return nil, err
+	}
 	path := filepath.Join(sessionsDir, sessionID+".jsonl")
 	f, err := os.Open(path)
 	if errors.Is(err, fs.ErrNotExist) {

ingestion/internal/symlinkguard/symlinkguard.go

@@ -0,0 +1,264 @@
+// Package symlinkguard is the hyperguild#157 tripwire. The brain directory is
+// a Syncthing sendreceive folder and Syncthing syncs symlinks; several brain
+// readers (search, vectorstore, context, graph) follow a symlink out of the
+// brain and would index or return whatever it points to. Until every reader
+// reads through an os.Root, a symlink inside the brain, or a directory the
+// scan cannot read (which could hide one), is an incident: the server refuses
+// to start on one (main), and Watch reports one that appears while it runs.
+package symlinkguard
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io/fs"
+	"log/slog"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// DefaultInterval is used when Watch is given a non-positive interval.
+const DefaultInterval = 30 * time.Second
+
+// Alert bounds (PR #160 review): the planter chooses the paths, so neither an
+// alert's size nor the queue may grow with what was planted.
+const (
+	maxPathsPerAlert = 10 // further paths are counted, not listed
+	maxPending       = 5  // queued alerts; the rest become one summary
+)
+
+// Notifier is the out-of-band alert sink (audit.Notifier satisfies it).
+type Notifier interface {
+	Notify(ctx context.Context, msg string) error
+}
+
+// Result is what a scan found: symlinks, and directories it could not read
+// (each of which could hide a symlink). Paths are brain-relative.
+type Result struct {
+	Symlinks   []string
+	Unreadable []string
+}
+
+// Clean reports whether the scan found nothing to act on.
+func (r Result) Clean() bool { return len(r.Symlinks) == 0 && len(r.Unreadable) == 0 }
+
+// String describes the findings for a log line or alert. Paths are quoted, so
+// a name containing a newline cannot blur two findings together.
+func (r Result) String() string {
+	q := r.quoted
+	var parts []string
+	if len(r.Symlinks) > 0 {
+		parts = append(parts, fmt.Sprintf("%d symlink(s): %s", len(r.Symlinks), q(r.Symlinks)))
+	}
+	if len(r.Unreadable) > 0 {
+		parts = append(parts, fmt.Sprintf("%d unreadable dir(s): %s", len(r.Unreadable), q(r.Unreadable)))
+	}
+	return strings.Join(parts, "; ")
+}
+
+// quoted joins at most maxPathsPerAlert paths, each strconv-quoted, and
+// counts the rest.
+func (Result) quoted(xs []string) string {
+	shown := xs
+	if len(shown) > maxPathsPerAlert {
+		shown = shown[:maxPathsPerAlert]
+	}
+	out := make([]string, len(shown))
+	for i, x := range shown {
+		out[i] = strconv.Quote(x)
+	}
+	s := strings.Join(out, ", ")
+	if extra := len(xs) - len(shown); extra > 0 {
+		s += fmt.Sprintf(" and %d more", extra)
+	}
+	return s
+}
+
+// Scan walks the brain dir and reports every symlink in it and every
+// directory it could not read, continuing past both. Only the ROOT .git is
+// skipped (it is brain-sync's, and no reader walks it); a nested .git is
+// scanned like any other directory. brainDir itself may be a symlink (a
+// volume mount); it is resolved first. The error is non-nil when the root
+// cannot be resolved (wrapping os.ErrNotExist when it is missing) or cannot be
+// listed.
+func Scan(brainDir string) (Result, error) {
+	root, err := filepath.EvalSymlinks(brainDir)
+	if err != nil {
+		return Result{}, fmt.Errorf("resolve brain dir: %w", err)
+	}
+	var r Result
+	rootGit := filepath.Join(root, ".git")
+	walkErr := filepath.WalkDir(root, func(p string, d fs.DirEntry, err error) error {
+		rel, _ := filepath.Rel(root, p)
+		rel = filepath.ToSlash(rel)
+		if err != nil {
+			if p == root {
+				return err
+			}
+			r.Unreadable = append(r.Unreadable, rel)
+			if d != nil && d.IsDir() {
+				return filepath.SkipDir
+			}
+			return nil
+		}
+		if d.IsDir() && p == rootGit {
+			return filepath.SkipDir
+		}
+		if d.Type()&os.ModeSymlink != 0 {
+			r.Symlinks = append(r.Symlinks, rel)
+		}
+		return nil
+	})
+	sort.Strings(r.Symlinks)
+	sort.Strings(r.Unreadable)
+	if walkErr != nil {
+		// Only the root's own error reaches here (deeper errors are recorded
+		// as Unreadable). A root that cannot be listed cannot be shown clean
+		// (PR #159 round 2: discarding this reported clean while search
+		// served a planted symlink).
+		return r, fmt.Errorf("scan brain dir: %w", walkErr)
+	}
+	return r, nil
+}
+
+// Watch rescans every interval (DefaultInterval if non-positive) until ctx
+// ends. Every symlink found is removed (the link, never its target:
+// hyperguild#157 decision), so one is readable for at most one interval.
+// Each removal is an alert; a persistent finding (a link it could not remove,
+// an unreadable dir, a scan error) alerts once per distinct state. Alerts
+// queue until Notify succeeds (see alertQueue): an outage delays them, and
+// any that do not fit the bounded queue, or are undeliverable, are counted in
+// a summary that is never dropped, so every incident is delivered or counted.
+func Watch(ctx context.Context, brainDir string, interval time.Duration, n Notifier) {
+	if interval <= 0 {
+		interval = DefaultInterval
+	}
+	t := time.NewTicker(interval)
+	defer t.Stop()
+	q := &alertQueue{}
+	reported := ""
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-t.C:
+		}
+		r, err := Scan(brainDir)
+		key := ""
+		if err != nil {
+			key = "cannot scan the brain dir: " + err.Error()
+		} else {
+			removed, failed := removeSymlinks(brainDir, r.Symlinks)
+			if len(removed) > 0 {
+				slog.Error("brain symlink tripwire removed symlinks", "count", len(removed))
+				q.push(fmt.Sprintf("brain symlink tripwire (hyperguild#157): removed %d symlink(s) from the brain dir: %s",
+					len(removed), Result{}.quoted(removed)))
+			}
+			key = Result{Symlinks: failed, Unreadable: r.Unreadable}.String()
+		}
+		if key != reported {
+			reported = key
+			if key != "" {
+				slog.Error("brain symlink tripwire", "finding", key)
+				q.push("brain symlink tripwire (hyperguild#157): " + key +
+					". Readers may follow symlinks out of the brain; fix them.")
+			}
+		}
+		q.flush(ctx, n)
+	}
+}
+
+// alertQueue holds alerts until Notify accepts them. It is bounded (at most
+// maxPending queued) and loses nothing from the record: every overflow and
+// every dropped message increments suppressed, sent as a summary that is
+// retried every tick and never dropped.
+//
+// A message is dropped only when the notifier rejects it permanently (an
+// error with Permanent() == true, e.g. ntfy 413). Every other failure is an
+// outage, and nothing is dropped however long it lasts (PR #160 round 2:
+// dropping after N raw failures lost the only incident of a long outage).
+// Each flush tries every queued message, so one undeliverable message cannot
+// block the others.
+type alertQueue struct {
+	items      []string
+	suppressed int
+}
+
+func (q *alertQueue) push(msg string) {
+	if len(q.items) >= maxPending {
+		q.suppressed++
+		return
+	}
+	q.items = append(q.items, msg)
+}
+
+func (q *alertQueue) flush(ctx context.Context, n Notifier) {
+	if n == nil {
+		q.items, q.suppressed = nil, 0
+		return
+	}
+	kept := q.items[:0]
+	for _, msg := range q.items {
+		err := n.Notify(ctx, msg)
+		switch {
+		case err == nil:
+		case permanent(err):
+			slog.Error("symlink tripwire alert rejected permanently; counted in the summary", "err", err)
+			q.suppressed++
+		default:
+			slog.Warn("symlink tripwire notify failed; will retry", "err", err)
+			kept = append(kept, msg)
+		}
+	}
+	q.items = kept
+	if q.suppressed > 0 {
+		msg := fmt.Sprintf("brain symlink tripwire (hyperguild#157): %d further alert(s) were suppressed or undeliverable; check the ingestion logs", q.suppressed)
+		if err := n.Notify(ctx, msg); err == nil {
+			q.suppressed = 0
+		}
+	}
+}
+
+// permanent reports whether err says the message itself can never be sent.
+func permanent(err error) bool {
+	var p interface{ Permanent() bool }
+	return errors.As(err, &p) && p.Permanent()
+}
+
+// removeSymlinks unlinks each brain-relative symlink through an os.Root on
+// the brain dir, after re-checking it is still a symlink. Removing a symlink
+// never touches its target. It returns what was removed and what was not.
+func removeSymlinks(brainDir string, rels []string) (removed, failed []string) {
+	if len(rels) == 0 {
+		return nil, nil
+	}
+	resolved, err := filepath.EvalSymlinks(brainDir)
+	if err != nil {
+		return nil, rels
+	}
+	root, err := os.OpenRoot(resolved)
+	if err != nil {
+		return nil, rels
+	}
+	defer func() { _ = root.Close() }()
+	for _, rel := range rels {
+		fi, err := root.Lstat(rel)
+		if err != nil || fi.Mode()&os.ModeSymlink == 0 {
+			failed = append(failed, rel)
+			continue
+		}
+		// root.Remove, not os.RemoveAll: if the link is swapped for a
+		// non-empty directory after the Lstat, Remove refuses rather than
+		// deleting it recursively, and it cannot act outside the root.
+		if err := root.Remove(rel); err != nil {
+			failed = append(failed, rel)
+			continue
+		}
+		removed = append(removed, rel)
+	}
+	return removed, failed
+}

ingestion/internal/symlinkguard/symlinkguard_test.go

@@ -0,0 +1,498 @@
+package symlinkguard
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// hyperguild#157: the brain dir is a Syncthing sendreceive folder and
+// Syncthing syncs symlinks; several readers follow them out of the brain.
+// Until every reader goes through an os.Root, a symlink anywhere in the brain,
+// or a directory the scan cannot read (which could hide one), is an incident.
+
+func TestScanReportsSymlinksAtEveryDepthIncludingNestedGit(t *testing.T) {
+	brain := t.TempDir()
+	outside := t.TempDir()
+	require.NoError(t, os.MkdirAll(filepath.Join(brain, "wiki", "w", "facts", ".git"), 0o755))
+	require.NoError(t, os.MkdirAll(filepath.Join(brain, ".git", "objects"), 0o755))
+	require.NoError(t, os.Symlink(filepath.Join(outside, "f"), filepath.Join(brain, "wiki", "w", "facts", "leak.md")))
+	require.NoError(t, os.Symlink(outside, filepath.Join(brain, "wiki", "dirlink")))
+	// PR #159 review: only the ROOT .git is skipped; a nested .git is not
+	// special to the brain readers, which walk into it.
+	require.NoError(t, os.Symlink(filepath.Join(outside, "g"), filepath.Join(brain, "wiki", "w", "facts", ".git", "leak.md")))
+	require.NoError(t, os.Symlink(outside, filepath.Join(brain, ".git", "objects", "alt")))
+
+	r, err := Scan(brain)
+	require.NoError(t, err)
+	assert.ElementsMatch(t, []string{"wiki/w/facts/leak.md", "wiki/dirlink", "wiki/w/facts/.git/leak.md"}, r.Symlinks)
+	assert.Empty(t, r.Unreadable)
+}
+
+// PR #159 review: WalkDir stopped at the first unreadable directory and the
+// startup check passed, while search (which keeps walking) served a planted
+// symlink. Scan now records the unreadable dir and keeps going.
+func TestScanReportsUnreadableDirsAndKeepsWalkingPastThem(t *testing.T) {
+	if os.Geteuid() == 0 {
+		t.Skip("root reads mode-000 directories")
+	}
+	brain := t.TempDir()
+	locked := filepath.Join(brain, "aaa")
+	require.NoError(t, os.MkdirAll(locked, 0o755))
+	require.NoError(t, os.Chmod(locked, 0o000))
+	t.Cleanup(func() { _ = os.Chmod(locked, 0o755) })
+	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "zzz-planted")))
+
+	r, err := Scan(brain)
+	require.NoError(t, err)
+	assert.Equal(t, []string{"aaa"}, r.Unreadable)
+	assert.Equal(t, []string{"zzz-planted"}, r.Symlinks, "the walk continues past the unreadable dir")
+}
+
+func TestScanResolvesASymlinkedRootAndReportsSymlinkedEntriesInsideIt(t *testing.T) {
+	real := t.TempDir()
+	link := filepath.Join(t.TempDir(), "brain")
+	require.NoError(t, os.Symlink(real, link))
+	require.NoError(t, os.WriteFile(filepath.Join(real, "n.md"), []byte("x"), 0o644))
+	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(real, "inner")))
+	r, err := Scan(link)
+	require.NoError(t, err)
+	assert.Equal(t, []string{"inner"}, r.Symlinks)
+}
+
+func TestScanOfAMissingRootIsErrNotExist(t *testing.T) {
+	_, err := Scan(filepath.Join(t.TempDir(), "nope"))
+	assert.True(t, errors.Is(err, os.ErrNotExist), "got %v", err)
+}
+
+type recNotifier struct {
+	mu   sync.Mutex
+	msgs []string
+	fail int // fail the first N calls
+}
+
+func (r *recNotifier) Notify(_ context.Context, m string) error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	r.msgs = append(r.msgs, m)
+	if r.fail > 0 {
+		r.fail--
+		return errors.New("ntfy down")
+	}
+	return nil
+}
+
+func (r *recNotifier) count() int { r.mu.Lock(); defer r.mu.Unlock(); return len(r.msgs) }
+
+func TestWatchNotifiesOncePerDistinctSetAndAgainForANewSet(t *testing.T) {
+	brain := t.TempDir()
+	n := &recNotifier{}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go Watch(ctx, brain, 10*time.Millisecond, n)
+
+	time.Sleep(50 * time.Millisecond)
+	assert.Zero(t, n.count(), "a clean brain raises nothing")
+	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "first")))
+	require.Eventually(t, func() bool { return n.count() == 1 }, 2*time.Second, 10*time.Millisecond)
+	time.Sleep(60 * time.Millisecond)
+	assert.Equal(t, 1, n.count(), "the same set is reported once, not every tick")
+	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "second")))
+	require.Eventually(t, func() bool { return n.count() == 2 }, 2*time.Second, 10*time.Millisecond)
+}
+
+// PR #159 review: last was recorded before Notify, so an alert lost to an
+// ntfy outage was never retried while the symlink stayed.
+func TestWatchRetriesAnAlertThatFailedToSend(t *testing.T) {
+	brain := t.TempDir()
+	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "planted")))
+	n := &recNotifier{fail: 2}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go Watch(ctx, brain, 10*time.Millisecond, n)
+	require.Eventually(t, func() bool { return n.count() == 3 }, 2*time.Second, 10*time.Millisecond)
+	time.Sleep(60 * time.Millisecond)
+	assert.Equal(t, 3, n.count(), "after one successful send, no more")
+}
+
+func TestWatchAlertsOnAnUnreadableDir(t *testing.T) {
+	if os.Geteuid() == 0 {
+		t.Skip("root reads mode-000 directories")
+	}
+	brain := t.TempDir()
+	locked := filepath.Join(brain, "locked")
+	require.NoError(t, os.MkdirAll(locked, 0o755))
+	require.NoError(t, os.Chmod(locked, 0o000))
+	t.Cleanup(func() { _ = os.Chmod(locked, 0o755) })
+	n := &recNotifier{}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go Watch(ctx, brain, 10*time.Millisecond, n)
+	require.Eventually(t, func() bool { return n.count() == 1 }, 2*time.Second, 10*time.Millisecond)
+	assert.Contains(t, n.msgs[0], "locked")
+}
+
+// PR #159 review: a non-positive interval panicked time.NewTicker inside the
+// goroutine and crashlooped the server.
+func TestWatchToleratesANonPositiveInterval(t *testing.T) {
+	brain := t.TempDir()
+	ctx, cancel := context.WithCancel(context.Background())
+	done := make(chan struct{})
+	go func() { Watch(ctx, brain, 0, nil); close(done) }()
+	cancel()
+	select {
+	case <-done:
+	case <-time.After(2 * time.Second):
+		t.Fatal("Watch did not return on cancel")
+	}
+}
+
+// PR #159 round 2: a brain root that can be entered but not listed (mode
+// 0100) made WalkDir fail at the root; the error was discarded and Scan
+// reported clean, while search (which goes straight into wiki/) still served
+// a planted symlink. A root that cannot be listed is now an error.
+func TestScanOfAnUnlistableRootIsAnError(t *testing.T) {
+	if os.Geteuid() == 0 {
+		t.Skip("root lists mode-0100 directories")
+	}
+	brain := t.TempDir()
+	require.NoError(t, os.MkdirAll(filepath.Join(brain, "wiki"), 0o755))
+	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "wiki", "leak.md")))
+	require.NoError(t, os.Chmod(brain, 0o100))
+	t.Cleanup(func() { _ = os.Chmod(brain, 0o755) })
+	_, err := Scan(brain)
+	require.Error(t, err)
+	assert.False(t, errors.Is(err, os.ErrNotExist), "an unlistable root is not a missing root")
+}
+
+// The same set that disappears and comes back is reported again.
+func TestWatchReportsASetAgainAfterItWasCleared(t *testing.T) {
+	brain := t.TempDir()
+	link := filepath.Join(brain, "planted")
+	n := &recNotifier{}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go Watch(ctx, brain, 10*time.Millisecond, n)
+	require.NoError(t, os.Symlink(t.TempDir(), link))
+	require.Eventually(t, func() bool { return n.count() == 1 }, 2*time.Second, 10*time.Millisecond)
+	// The tripwire removed it; planting it again is a new event.
+	require.Eventually(t, func() bool { _, err := os.Lstat(link); return os.IsNotExist(err) }, 2*time.Second, 10*time.Millisecond)
+	require.NoError(t, os.Symlink(t.TempDir(), link))
+	require.Eventually(t, func() bool { return n.count() == 2 }, 2*time.Second, 10*time.Millisecond)
+}
+
+// hyperguild#157 decision: the runtime tripwire removes a symlink it finds
+// (the link, never its target), so it is readable for at most one interval
+// instead of until a human acts, and the alert says what was removed.
+func TestWatchRemovesAnOutsideFileLinkButNotItsTargetOrRegularFiles(t *testing.T) {
+	brain := t.TempDir()
+	outside := filepath.Join(t.TempDir(), "target.md")
+	require.NoError(t, os.WriteFile(outside, []byte("keep me"), 0o644))
+	require.NoError(t, os.MkdirAll(filepath.Join(brain, "wiki"), 0o755))
+	link := filepath.Join(brain, "wiki", "leak.md")
+	require.NoError(t, os.Symlink(outside, link))
+	regular := filepath.Join(brain, "wiki", "note.md")
+	require.NoError(t, os.WriteFile(regular, []byte("note"), 0o644))
+
+	n := &recNotifier{}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go Watch(ctx, brain, 10*time.Millisecond, n)
+
+	require.Eventually(t, func() bool {
+		_, err := os.Lstat(link)
+		return os.IsNotExist(err)
+	}, 2*time.Second, 10*time.Millisecond, "the symlink is removed")
+	require.Eventually(t, func() bool { return n.count() >= 1 }, 2*time.Second, 10*time.Millisecond)
+	b, err := os.ReadFile(outside)
+	require.NoError(t, err)
+	assert.Equal(t, "keep me", string(b), "the target is untouched")
+	b, err = os.ReadFile(regular)
+	require.NoError(t, err)
+	assert.Equal(t, "note", string(b), "regular files are untouched")
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	assert.Contains(t, n.msgs[0], "removed")
+	assert.Contains(t, n.msgs[0], "wiki/leak.md")
+}
+
+func TestDefaultIntervalIsThirtySeconds(t *testing.T) {
+	assert.Equal(t, 30*time.Second, DefaultInterval)
+}
+
+// PR #160 review: the Lstat re-check and the os.Root confinement in
+// removeSymlinks had no test. Anything that is not a symlink inside the brain
+// is reported failed and nothing is deleted.
+func TestRemoveSymlinksRefusesNonSymlinksEscapesAndPathsThroughLinks(t *testing.T) {
+	brain := t.TempDir()
+	require.NoError(t, os.MkdirAll(filepath.Join(brain, "wiki", "real"), 0o755))
+	regular := filepath.Join(brain, "wiki", "note.md")
+	require.NoError(t, os.WriteFile(regular, []byte("note"), 0o644))
+	inLinked := filepath.Join(brain, "wiki", "real", "x.md")
+	require.NoError(t, os.WriteFile(inLinked, []byte("x"), 0o644))
+	require.NoError(t, os.Symlink(filepath.Join(brain, "wiki", "real"), filepath.Join(brain, "wiki", "linkdir")))
+	outside := filepath.Join(filepath.Dir(brain), "outside-157.md")
+	require.NoError(t, os.WriteFile(outside, []byte("o"), 0o644))
+	t.Cleanup(func() { _ = os.Remove(outside) })
+
+	removed, failed := removeSymlinks(brain, []string{
+		"wiki/note.md", "wiki/linkdir/x.md", "../outside-157.md", "wiki/missing.md",
+	})
+	assert.Empty(t, removed)
+	assert.ElementsMatch(t, []string{"wiki/note.md", "wiki/linkdir/x.md", "../outside-157.md", "wiki/missing.md"}, failed)
+	for _, p := range []string{regular, inLinked, outside} {
+		_, err := os.Stat(p)
+		assert.NoError(t, err, "%s must not be deleted", p)
+	}
+}
+
+// Dir targets and in-brain targets survive too, not only an outside file.
+func TestWatchRemovesDirAndInBrainLinksButNotTheirTargets(t *testing.T) {
+	brain := t.TempDir()
+	outsideDir := t.TempDir()
+	require.NoError(t, os.WriteFile(filepath.Join(outsideDir, "keep.md"), []byte("keep"), 0o644))
+	require.NoError(t, os.MkdirAll(filepath.Join(brain, "wiki"), 0o755))
+	inBrain := filepath.Join(brain, "wiki", "target.md")
+	require.NoError(t, os.WriteFile(inBrain, []byte("t"), 0o644))
+	require.NoError(t, os.Symlink(outsideDir, filepath.Join(brain, "wiki", "dirlink")))
+	require.NoError(t, os.Symlink(inBrain, filepath.Join(brain, "wiki", "inlink.md")))
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go Watch(ctx, brain, 10*time.Millisecond, nil)
+	require.Eventually(t, func() bool {
+		r, err := Scan(brain)
+		return err == nil && len(r.Symlinks) == 0
+	}, 2*time.Second, 10*time.Millisecond)
+	for _, p := range []string{filepath.Join(outsideDir, "keep.md"), inBrain} {
+		_, err := os.Stat(p)
+		assert.NoError(t, err, "%s must survive", p)
+	}
+}
+
+// PR #160 review: the planter chooses the paths. An alert names at most
+// maxPathsPerAlert of them and counts the rest, so its size stays bounded.
+func TestWatchAlertNamesBoundedPathsAndCountsTheRest(t *testing.T) {
+	brain := t.TempDir()
+	for i := 0; i < 50; i++ {
+		require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, strings.Repeat("n", 100)+strconv.Itoa(i))))
+	}
+	n := &recNotifier{}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go Watch(ctx, brain, 10*time.Millisecond, n)
+	require.Eventually(t, func() bool { return n.count() >= 1 }, 2*time.Second, 10*time.Millisecond)
+	n.mu.Lock()
+	msg := n.msgs[0]
+	n.mu.Unlock()
+	assert.Contains(t, msg, "removed 50 symlink(s)")
+	assert.Contains(t, msg, "and 40 more")
+	assert.Less(t, len(msg), 2500, "alert size is bounded regardless of how many links were planted")
+}
+
+// rejectNotifier refuses every message containing a marker, forever.
+type rejectNotifier struct {
+	recNotifier
+	reject string
+}
+
+// permanentErr is a rejection the notifier says can never succeed (like ntfy 413).
+type permanentErr struct{}
+
+func (permanentErr) Error() string   { return "413 payload too large" }
+func (permanentErr) Permanent() bool { return true }
+
+func (r *rejectNotifier) Notify(ctx context.Context, m string) error {
+	if strings.Contains(m, r.reject) {
+		r.mu.Lock()
+		r.msgs = append(r.msgs, "REJECTED")
+		r.mu.Unlock()
+		return permanentErr{}
+	}
+	return r.recNotifier.Notify(ctx, m)
+}
+
+// PR #160 review: one message the server will never accept blocked every
+// later alert forever (head-of-line). It is dropped after maxAttempts.
+func TestWatchDropsAMessageThatNeverSendsSoLaterAlertsFlow(t *testing.T) {
+	brain := t.TempDir()
+	n := &rejectNotifier{reject: "POISON"}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go Watch(ctx, brain, 10*time.Millisecond, n)
+	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "POISON")))
+	time.Sleep(30 * time.Millisecond)
+	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "later")))
+	require.Eventually(t, func() bool {
+		n.mu.Lock()
+		defer n.mu.Unlock()
+		for _, m := range n.msgs {
+			if strings.Contains(m, "later") {
+				return true
+			}
+		}
+		return false
+	}, 3*time.Second, 10*time.Millisecond, "a later alert is delivered despite a poison message")
+}
+
+// toggleNotifier fails while down is set.
+type toggleNotifier struct {
+	recNotifier
+	down atomic.Bool
+}
+
+func (r *toggleNotifier) Notify(ctx context.Context, m string) error {
+	if r.down.Load() {
+		return errors.New("ntfy down")
+	}
+	return r.recNotifier.Notify(ctx, m)
+}
+
+// PR #160 review: an outage queued one message per removal, unbounded. The
+// queue holds at most maxPending messages; the rest become one summary.
+func TestWatchQueueIsBoundedDuringAnOutage(t *testing.T) {
+	brain := t.TempDir()
+	n := &toggleNotifier{}
+	n.down.Store(true)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go Watch(ctx, brain, 5*time.Millisecond, n)
+	for i := 0; i < 30; i++ {
+		link := filepath.Join(brain, "p"+strconv.Itoa(i))
+		require.NoError(t, os.Symlink(t.TempDir(), link))
+		require.Eventually(t, func() bool { _, err := os.Lstat(link); return os.IsNotExist(err) }, 2*time.Second, 2*time.Millisecond)
+	}
+	n.down.Store(false)
+	require.Eventually(t, func() bool { return n.count() >= 1 }, 2*time.Second, 5*time.Millisecond)
+	time.Sleep(100 * time.Millisecond)
+	assert.LessOrEqual(t, n.count(), maxPending+1, "queued alerts plus at most one suppression summary")
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	found := false
+	for _, m := range n.msgs {
+		if strings.Contains(m, "suppressed") {
+			found = true
+		}
+	}
+	assert.True(t, found, "suppressed alerts are counted in a summary")
+}
+
+// Within the bound, every alert queued during an outage is delivered after
+// it, each naming its own removal (PR #160 review: truncating the queue after
+// the first send stayed green).
+func TestWatchDeliversEveryQueuedAlertAfterAShortOutage(t *testing.T) {
+	brain := t.TempDir()
+	n := &toggleNotifier{}
+	n.down.Store(true)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go Watch(ctx, brain, 5*time.Millisecond, n)
+	for _, name := range []string{"qa", "qb", "qc"} {
+		link := filepath.Join(brain, name)
+		require.NoError(t, os.Symlink(t.TempDir(), link))
+		require.Eventually(t, func() bool { _, err := os.Lstat(link); return os.IsNotExist(err) }, 2*time.Second, 2*time.Millisecond)
+	}
+	n.down.Store(false)
+	require.Eventually(t, func() bool { return n.count() == 3 }, 2*time.Second, 5*time.Millisecond)
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	for i, name := range []string{"qa", "qb", "qc"} {
+		assert.Contains(t, n.msgs[i], strconv.Quote(name))
+	}
+}
+
+// PR #160 round 2: dropping after N failures could not tell a poison message
+// from an outage, so a 15-minute outage silently lost the only incident. A
+// message is only dropped when it keeps failing while others send; through
+// an outage nothing is dropped, however long.
+func TestWatchLosesNoAlertThroughALongOutage(t *testing.T) {
+	brain := t.TempDir()
+	n := &toggleNotifier{}
+	n.down.Store(true)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go Watch(ctx, brain, 2*time.Millisecond, n)
+	link := filepath.Join(brain, "only-incident")
+	require.NoError(t, os.Symlink(t.TempDir(), link))
+	require.Eventually(t, func() bool { _, err := os.Lstat(link); return os.IsNotExist(err) }, 2*time.Second, 2*time.Millisecond)
+	time.Sleep(200 * time.Millisecond) // ~100 ticks of outage, far past any attempt limit
+	n.down.Store(false)
+	require.Eventually(t, func() bool { return n.count() >= 1 }, 2*time.Second, 5*time.Millisecond)
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	assert.Contains(t, n.msgs[0], strconv.Quote("only-incident"))
+}
+
+// Every removal is either delivered or counted in the suppression summary:
+// none disappears from the record (round 2: 74 of 300 were in neither).
+func TestWatchAccountsForEveryRemovalDuringAnOutage(t *testing.T) {
+	brain := t.TempDir()
+	n := &toggleNotifier{}
+	n.down.Store(true)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go Watch(ctx, brain, 2*time.Millisecond, n)
+	const plants = 25
+	for i := 0; i < plants; i++ {
+		link := filepath.Join(brain, "acct"+strconv.Itoa(i))
+		require.NoError(t, os.Symlink(t.TempDir(), link))
+		require.Eventually(t, func() bool { _, err := os.Lstat(link); return os.IsNotExist(err) }, 2*time.Second, 1*time.Millisecond)
+	}
+	n.down.Store(false)
+	require.Eventually(t, func() bool {
+		n.mu.Lock()
+		defer n.mu.Unlock()
+		for _, m := range n.msgs {
+			if strings.Contains(m, "suppressed") {
+				return true
+			}
+		}
+		return false
+	}, 2*time.Second, 5*time.Millisecond)
+	time.Sleep(50 * time.Millisecond)
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	delivered, counted := 0, 0
+	for _, m := range n.msgs {
+		if strings.Contains(m, "removed 1 symlink(s)") {
+			delivered++
+		}
+		if i := strings.Index(m, "): "); i >= 0 && strings.Contains(m, "suppressed") {
+			_, _ = fmt.Sscanf(m[i+3:], "%d", &counted)
+		}
+	}
+	assert.Equal(t, plants, delivered+counted, "delivered %d + counted %d must equal %d removals", delivered, counted, plants)
+}
+
+// A poison message is still dropped (others send while it fails), and the
+// drop is counted in the summary.
+func TestWatchDropsAPoisonMessageAndCountsIt(t *testing.T) {
+	brain := t.TempDir()
+	n := &rejectNotifier{reject: "POISON"}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	go Watch(ctx, brain, 5*time.Millisecond, n)
+	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "POISON")))
+	time.Sleep(20 * time.Millisecond)
+	require.NoError(t, os.Symlink(t.TempDir(), filepath.Join(brain, "fine")))
+	require.Eventually(t, func() bool {
+		n.mu.Lock()
+		defer n.mu.Unlock()
+		for _, m := range n.msgs {
+			if strings.Contains(m, "1 further alert(s)") {
+				return true
+			}
+		}
+		return false
+	}, 3*time.Second, 5*time.Millisecond, "the dropped poison alert is counted in a summary")
+}

ingestion/internal/vectorstore/sync.go

@@ -2,12 +2,15 @@ package vectorstore
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"io/fs"
 	"log/slog"
-	"os"
+	"path"
-	"path/filepath"
 	"strings"
 	"time"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
 )
 
 // Embedder produces dense vectors. The embed package's Client satisfies
@@ -90,31 +93,38 @@ func Sync(ctx context.Context, brainDir string, store Store, embedder Embedder)
 	}
 	seenParents := make(map[string]struct{})
 
+	// Through the brain root, regular files only (hyperguild#157): the brain
+	// is a Syncthing folder, and os.ReadFile followed a synced symlink into
+	// the embeddings and blocked on a FIFO.
+	bfs, err := brainfs.Open(brainDir)
+	if err != nil {
+		return res, fmt.Errorf("open brain: %w", err)
+	}
+	defer func() { _ = bfs.Close() }()
+
 	for _, sub := range scanDirs {
-		root := filepath.Join(brainDir, sub)
+		if _, err := bfs.Lstat(sub); errors.Is(err, fs.ErrNotExist) {
-		if _, err := os.Stat(root); os.IsNotExist(err) {
 			continue
 		}
-
+		// Any other walk error, including a scan root that is a symlink,
-		err = filepath.WalkDir(root, func(path string, d os.DirEntry, err error) error {
+		// aborts the run below.
-			if err != nil {
+		var walkErr error
-				return err
+		onErr := func(rel string, err error) {
+			if walkErr == nil {
+				walkErr = fmt.Errorf("%s: %w", rel, err)
 			}
-			if d.IsDir() || !strings.HasSuffix(path, ".md") || d.Name() == "_index.md" {
+		}
+		err = bfs.WalkRegular(sub, func(relSlash string) error {
+			if !strings.HasSuffix(relSlash, ".md") || path.Base(relSlash) == "_index.md" {
 				return nil
 			}
-			rel, err := filepath.Rel(brainDir, path)
-			if err != nil {
-				return err
-			}
-			relSlash := filepath.ToSlash(rel)
 			seenParents[relSlash] = struct{}{}
 
 			if ps, ok := parents[relSlash]; ok {
 				// File already has chunks in the store. Re-embed only when
 				// the file has been edited since the oldest chunk was
 				// written. Tolerate clock skew with a sub-second grace.
-				info, statErr := d.Info()
+				info, statErr := bfs.Lstat(relSlash)
 				if statErr != nil {
 					res.Errors = append(res.Errors, fmt.Errorf("stat %s: %w", relSlash, statErr))
 					return nil
@@ -132,7 +142,7 @@ func Sync(ctx context.Context, brainDir string, store Store, embedder Embedder)
 				}
 			}
 
-			content, readErr := os.ReadFile(path)
+			content, readErr := bfs.ReadRegular(relSlash)
 			if readErr != nil {
 				res.Errors = append(res.Errors, fmt.Errorf("read %s: %w", relSlash, readErr))
 				return nil
@@ -151,7 +161,12 @@ func Sync(ctx context.Context, brainDir string, store Store, embedder Embedder)
 				res.Added++
 			}
 			return nil
-		})
+		}, onErr)
+		if err == nil {
+			err = walkErr
+		}
+		// Abort before the delete pass: an incomplete walk would leave
+		// seenParents short and delete chunks of files that still exist.
 		if err != nil {
 			return res, fmt.Errorf("walk %s: %w", sub, err)
 		}

ingestion/internal/vectorstore/sync_root_test.go

@@ -0,0 +1,126 @@
+package vectorstore_test
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs/brainfstest"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/vectorstore"
+)
+
+// recordingEmbedder keeps every text it was asked to embed.
+type recordingEmbedder struct {
+	mu    sync.Mutex
+	texts []string
+}
+
+func (e *recordingEmbedder) Embed(_ context.Context, text string) ([]float32, error) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	e.texts = append(e.texts, text)
+	return []float32{1}, nil
+}
+
+func (e *recordingEmbedder) all() string {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	return strings.Join(e.texts, "\n")
+}
+
+// hyperguild#157 slice 3: Sync walked wiki/ and knowledge/ and read each .md
+// with os.ReadFile, so a symlinked note had its target embedded and served by
+// semantic search, and a FIFO stalled the sync.
+func TestSyncRefusesSymlinkedNotesAndSurvivesSwapRaces(t *testing.T) {
+	brain := t.TempDir()
+	writeNote(t, brain, "wiki/w/facts/ok.md", "inside note")
+	require.NoError(t, os.Symlink(brainfstest.Outside(t), filepath.Join(brain, "wiki", "w", "facts", "leak.md")))
+
+	emb := &recordingEmbedder{}
+	store := &stubStore{}
+	_, err := vectorstore.Sync(context.Background(), brain, store, emb)
+	require.NoError(t, err)
+	assert.Contains(t, emb.all(), "inside note", "positive control: the regular note is embedded")
+	assert.NotContains(t, emb.all(), brainfstest.Sentinel)
+	for p := range store.upserts {
+		assert.NotContains(t, p, "leak.md")
+	}
+
+	p := filepath.Join(brain, "knowledge", "r.md")
+	require.NoError(t, os.MkdirAll(filepath.Dir(p), 0o755))
+	sync := func() string {
+		e := &recordingEmbedder{}
+		_, _ = vectorstore.Sync(context.Background(), brain, &stubStore{}, e)
+		return e.all()
+	}
+	brainfstest.AssertNoLeak(t, p, "inside", 1500*time.Millisecond, sync)
+	brainfstest.AssertNoHang(t, p, "inside", 1500*time.Millisecond, 6*time.Second, func() { _ = sync() })
+}
+
+// Chunks embedded from a symlinked note before this fix are deleted: the
+// note is no longer seen, so the delete pass drops its rows.
+func TestSyncDeletesChunksOfASymlinkedNote(t *testing.T) {
+	brain := t.TempDir()
+	writeNote(t, brain, "wiki/w/facts/ok.md", "inside note")
+	require.NoError(t, os.Symlink(brainfstest.Outside(t), filepath.Join(brain, "wiki", "w", "facts", "leak.md")))
+	store := &stubStore{known: map[string]time.Time{
+		"wiki/w/facts/leak.md#0001": {},
+		"wiki/w/facts/ok.md#0001":   {},
+	}}
+	_, err := vectorstore.Sync(context.Background(), brain, store, &recordingEmbedder{})
+	require.NoError(t, err)
+	assert.Equal(t, []string{"wiki/w/facts/leak.md#0001"}, store.deletes)
+}
+
+// A walk error aborts Sync before the delete pass, so chunks of files the
+// walk could not see are kept.
+func TestSyncAbortsBeforeDeletingWhenASubdirIsUnreadable(t *testing.T) {
+	if os.Geteuid() == 0 {
+		t.Skip("root ignores directory permissions")
+	}
+	brain := t.TempDir()
+	writeNote(t, brain, "wiki/w/facts/ok.md", "inside note")
+	locked := filepath.Join(brain, "wiki", "w")
+	require.NoError(t, os.Chmod(locked, 0o000))
+	t.Cleanup(func() { _ = os.Chmod(locked, 0o755) })
+	store := &stubStore{known: map[string]time.Time{"wiki/w/facts/ok.md#0001": {}}}
+	_, err := vectorstore.Sync(context.Background(), brain, store, &recordingEmbedder{})
+	assert.Error(t, err)
+	assert.Empty(t, store.deletes)
+}
+
+// A scan root that is a symlink inside the brain (knowledge -> .) was
+// followed by fs.WalkDir, aliasing raw/, sessions/ and root files into the
+// index. Sync now aborts on it, before embedding or deleting anything.
+func TestSyncAbortsOnASymlinkedScanRoot(t *testing.T) {
+	brain := t.TempDir()
+	writeNote(t, brain, "wiki/w/a.md", "wiki note")
+	writeNote(t, brain, "sessions/s1.md", "session note")
+	require.NoError(t, os.Symlink(".", filepath.Join(brain, "knowledge")))
+	emb := &recordingEmbedder{}
+	store := &stubStore{known: map[string]time.Time{"wiki/w/a.md#0001": {}}}
+	_, err := vectorstore.Sync(context.Background(), brain, store, emb)
+	assert.Error(t, err)
+	assert.NotContains(t, emb.all(), "session note")
+	for p := range store.upserts {
+		assert.False(t, strings.HasPrefix(p, "knowledge/"), "upserted %s", p)
+	}
+	assert.Empty(t, store.deletes)
+}
+
+// A missing scan root is skipped; the other root still syncs.
+func TestSyncSkipsAMissingScanRoot(t *testing.T) {
+	brain := t.TempDir()
+	writeNote(t, brain, "wiki/w/a.md", "wiki note")
+	emb := &recordingEmbedder{}
+	_, err := vectorstore.Sync(context.Background(), brain, &stubStore{}, emb)
+	require.NoError(t, err)
+	assert.Contains(t, emb.all(), "wiki note")
+}

ingestion/internal/watcher/watcher.go

@@ -48,8 +48,25 @@ func Start(ctx context.Context, cfg Config) {
 func processDir(ctx context.Context, cfg Config, date string) []error {
 	rawDir := filepath.Join(cfg.BrainDir, "raw")
 
+	// Every read goes through an os.Root on raw/ (hyperguild#153): raw/ is
+	// writable via Syncthing, and a file swapped for a symlink between the walk
+	// and the read must not lead out of it. A symlinked raw/ is refused.
+	if fi, lerr := os.Lstat(rawDir); lerr != nil {
+		if os.IsNotExist(lerr) {
+			return nil
+		}
+		return []error{fmt.Errorf("stat raw dir: %w", lerr)}
+	} else if fi.Mode()&os.ModeSymlink != 0 || !fi.IsDir() {
+		return []error{fmt.Errorf("raw dir %s is not a real directory; refusing to ingest from it", rawDir)}
+	}
+	root, err := os.OpenRoot(rawDir)
+	if err != nil {
+		return []error{fmt.Errorf("open raw root: %w", err)}
+	}
+	defer func() { _ = root.Close() }()
+
 	var errs []error
-	err := filepath.WalkDir(rawDir, func(path string, d os.DirEntry, err error) error {
+	err = filepath.WalkDir(rawDir, func(path string, d os.DirEntry, err error) error {
 		if err != nil {
 			return err
 		}
@@ -86,6 +103,10 @@ func processDir(ctx context.Context, cfg Config, date string) []error {
 		if strings.HasPrefix(d.Name(), "tunnel-candidates-") {
 			return nil
 		}
+		// Only regular files are notes; a symlink's target may be anywhere.
+		if !d.Type().IsRegular() {
+			return nil
+		}
 
 		// Skip files that have already been processed or permanently failed.
 		if _, err := os.Stat(path + ".processed"); err == nil {
@@ -95,7 +116,7 @@ func processDir(ctx context.Context, cfg Config, date string) []error {
 			return nil
 		}
 
-		if err := processFile(ctx, cfg, path, date); err != nil {
+		if err := processFile(ctx, cfg, root, rawDir, path, date); err != nil {
 			errs = append(errs, fmt.Errorf("process %s: %w", filepath.Base(path), err))
 		}
 		return nil
@@ -109,11 +130,15 @@ func processDir(ctx context.Context, cfg Config, date string) []error {
 // processFile reads a file, calls pipeline.Run, copies it to processed/ or failed/,
 // and writes a marker file next to the original so the watcher skips it next poll.
 // The original file is never deleted, keeping Syncthing-connected vaults (e.g. Obsidian) intact.
-func processFile(ctx context.Context, cfg Config, path, date string) error {
+func processFile(ctx context.Context, cfg Config, root *os.Root, rawDir, path, date string) error {
 	filename := filepath.Base(path)
 	source := deriveSource(filename)
+	rel, err := filepath.Rel(rawDir, path)
+	if err != nil {
+		return fmt.Errorf("relative path: %w", err)
+	}
 
-	content, err := extract.Text(path)
+	content, err := extract.TextIn(root, rel)
 	if err != nil {
 		return fmt.Errorf("extract text: %w", err)
 	}
@@ -126,7 +151,7 @@ func processFile(ctx context.Context, cfg Config, path, date string) error {
 			return fmt.Errorf("mkdir failed dir: %w", mkErr)
 		}
 		dest := filepath.Join(failedDir, filename)
-		if cpErr := copyFile(path, dest); cpErr != nil {
+		if cpErr := copyFromRoot(root, rel, dest); cpErr != nil {
 			return fmt.Errorf("copy to failed: %w", cpErr)
 		}
 		if mkErr := os.WriteFile(path+".failed", []byte(runErr.Error()), 0o644); mkErr != nil {
@@ -154,7 +179,7 @@ func processFile(ctx context.Context, cfg Config, path, date string) error {
 		base := strings.TrimSuffix(filename, ext)
 		dest = filepath.Join(processedDir, base+"-"+time.Now().UTC().Format("150405")+ext)
 	}
-	if err := copyFile(path, dest); err != nil {
+	if err := copyFromRoot(root, rel, dest); err != nil {
 		return fmt.Errorf("copy to processed: %w", err)
 	}
 	if err := os.WriteFile(path+".processed", []byte(date), 0o644); err != nil {
@@ -165,26 +190,6 @@ func processFile(ctx context.Context, cfg Config, path, date string) error {
 	return nil
 }
 
-// copyFile copies src to dst, creating dst if it doesn't exist.
-func copyFile(src, dst string) error {
-	in, err := os.Open(src)
-	if err != nil {
-		return fmt.Errorf("open src: %w", err)
-	}
-	defer in.Close() //nolint:errcheck
-
-	out, err := os.Create(dst)
-	if err != nil {
-		return fmt.Errorf("create dst: %w", err)
-	}
-
-	if _, err := io.Copy(out, in); err != nil {
-		out.Close() //nolint:errcheck
-		return fmt.Errorf("copy: %w", err)
-	}
-	return out.Close()
-}
-
 // deriveSource turns a filename into a human-readable source name.
 // "shape-up-book.md" → "Shape Up Book"
 func deriveSource(filename string) string {
@@ -221,3 +226,30 @@ func appendWatcherLog(brainDir, filename string, runErr error, date string) erro
 	}
 	return f.Close()
 }
+
+// copyFromRoot archives a raw/ file read through the root, refusing anything
+// that is not a regular file, so a swapped-in symlink cannot copy an outside
+// file into raw/processed/ or raw/failed/ (hyperguild#153).
+func copyFromRoot(root *os.Root, rel, dst string) error {
+	fi, err := root.Lstat(rel)
+	if err != nil {
+		return err
+	}
+	if !fi.Mode().IsRegular() {
+		return fmt.Errorf("%s: not a regular file", rel)
+	}
+	in, _, err := extract.OpenRegular(root, rel)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = in.Close() }()
+	out, err := os.Create(dst)
+	if err != nil {
+		return err
+	}
+	if _, err := io.Copy(out, in); err != nil {
+		_ = out.Close()
+		return err
+	}
+	return out.Close()
+}

ingestion/internal/watcher/watcher_test.go

@@ -7,6 +7,10 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"syscall"
 	"testing"
 	"time"
 
@@ -282,3 +286,107 @@ func TestProcessDir_SkipsTunnelCandidateFiles(t *testing.T) {
 	_, err = os.Stat(filepath.Join(brainDir, "raw", "processed", date, "tunnel-candidates-2026-07-19.md"))
 	assert.True(t, os.IsNotExist(err), "tunnel-candidates file should not be copied to processed/")
 }
+
+// hyperguild#153: raw/ is writable via Syncthing, and the watcher ingests
+// whatever lands there with no API call at all. WalkDir yields symlinked
+// files, and extract.Text followed them, so a symlink to any pod-readable
+// file would be extracted into the brain. The watcher now ingests only
+// regular files, read through an os.Root on raw/.
+func TestProcessDir_IngestsTheRealNoteAndSkipsTheSymlinkBesideIt(t *testing.T) {
+	brainDir := setupBrainDir(t)
+	outside := filepath.Join(t.TempDir(), "secret.md")
+	require.NoError(t, os.WriteFile(outside, []byte("SENTINEL-153-WATCHER"), 0o644))
+	// "a-" sorts before "real": a walk that stopped at the first symlink
+	// (filepath.SkipAll — one synced link halting all ingestion) would fail
+	// the call count below (PR #156 review).
+	require.NoError(t, os.Symlink(outside, filepath.Join(brainDir, "raw", "a-leak.md")))
+	require.NoError(t, os.WriteFile(filepath.Join(brainDir, "raw", "real.md"), []byte("real note"), 0o644))
+
+	var sawSentinel bool
+	calls := 0
+	cfg := Config{BrainDir: brainDir, Interval: time.Hour, Pipeline: pipeline.Config{
+		Complete: func(_ context.Context, _, user string) (string, error) {
+			calls++
+			if strings.Contains(user, "SENTINEL-153-WATCHER") {
+				sawSentinel = true
+			}
+			b, _ := json.Marshal([]pipeline.RawPage{{Title: "X", Type: "source", Subtype: "article", Content: "## S\n\nx\n"}})
+			return string(b), nil
+		},
+		Schema: "# Schema",
+	}}
+	errs := processDir(context.Background(), cfg, time.Now().UTC().Format("2006-01-02"))
+	assert.Empty(t, errs)
+	assert.False(t, sawSentinel, "the symlink target must never reach the pipeline")
+	assert.Equal(t, 1, calls, "exactly the real note is ingested; the symlink is not a note")
+}
+
+// A symlinked raw/ is refused outright: os.OpenRoot would otherwise follow
+// it and confine reads to wherever it points.
+func TestProcessDir_RefusesASymlinkedRawDir(t *testing.T) {
+	brainDir := t.TempDir()
+	elsewhere := t.TempDir()
+	require.NoError(t, os.WriteFile(filepath.Join(elsewhere, "x.md"), []byte("SENTINEL-153-RAWLINK"), 0o644))
+	require.NoError(t, os.Symlink(elsewhere, filepath.Join(brainDir, "raw")))
+	calls := 0
+	cfg := Config{BrainDir: brainDir, Interval: time.Hour, Pipeline: pipeline.Config{
+		Complete: func(context.Context, string, string) (string, error) { calls++; return "[]", nil },
+		Schema:   "# Schema",
+	}}
+	errs := processDir(context.Background(), cfg, time.Now().UTC().Format("2006-01-02"))
+	assert.NotEmpty(t, errs, "a symlinked raw/ must be reported, not silently ingested")
+	assert.Zero(t, calls)
+}
+
+// PR #156: a FIFO swapped into raw/ between the watcher's checks and its
+// read or archive copy must not hang the watcher, which runs unattended.
+func TestProcessDir_DoesNotHangUnderAFIFOSwapRace(t *testing.T) {
+	brainDir := setupBrainDir(t)
+	raw := filepath.Join(brainDir, "raw")
+	var stop atomic.Bool
+	var wg sync.WaitGroup
+	wg.Add(1)
+	// Awaited before t.TempDir's cleanup (hyperguild#162).
+	t.Cleanup(func() { stop.Store(true); wg.Wait() })
+	go func() {
+		defer wg.Done()
+		for i := 0; !stop.Load(); i++ {
+			tmp := filepath.Join(raw, ".swap")
+			_ = os.Remove(tmp)
+			if i%2 == 0 {
+				_ = os.WriteFile(tmp, []byte("x"), 0o644)
+			} else {
+				_ = syscall.Mkfifo(tmp, 0o644)
+			}
+			_ = os.Rename(tmp, filepath.Join(raw, "r.md"))
+		}
+	}()
+	cfg := Config{BrainDir: brainDir, Interval: time.Hour, Pipeline: pipeline.Config{
+		Complete: func(context.Context, string, string) (string, error) {
+			b, _ := json.Marshal([]pipeline.RawPage{{Title: "R", Type: "source", Subtype: "article", Content: "## S\n\nx\n"}})
+			return string(b), nil
+		},
+		Schema: "# Schema",
+	}}
+	var iters atomic.Int64
+	done := make(chan struct{})
+	go func() {
+		for deadline := time.Now().Add(1500 * time.Millisecond); time.Now().Before(deadline); {
+			_ = os.Remove(filepath.Join(raw, "r.md.processed"))
+			_ = os.Remove(filepath.Join(raw, "r.md.failed"))
+			_ = processDir(context.Background(), cfg, "2026-10-03")
+			iters.Add(1)
+		}
+		close(done)
+	}()
+	select {
+	case <-done:
+		stop.Store(true)
+	case <-time.After(8 * time.Second):
+		stop.Store(true)
+		if f, err := os.OpenFile(filepath.Join(raw, "r.md"), os.O_WRONLY|syscall.O_NONBLOCK, 0); err == nil {
+			_ = f.Close()
+		}
+		t.Fatalf("the watcher hung on a swapped-in FIFO after %d iterations", iters.Load())
+	}
+}

internal/brain/client.go

@@ -13,6 +13,7 @@ import (
 	"io"
 	"log/slog"
 	"net/http"
+	"os"
 	"strings"
 )
 
@@ -42,6 +43,10 @@ func Query(ctx context.Context, baseURL, query string, limit int) (string, error
 		return "", nil
 	}
 	req.Header.Set("Content-Type", "application/json")
+	// The REST API requires a bearer token since hyperguild#149.
+	if tok := os.Getenv("BRAIN_MCP_TOKEN"); tok != "" {
+		req.Header.Set("Authorization", "Bearer "+tok)
+	}
 
 	resp, err := http.DefaultClient.Do(req)
 	if err != nil {

internal/brain/client_test.go

@@ -65,3 +65,18 @@ func TestQueryUnavailableServerReturnsEmpty(t *testing.T) {
 	require.NoError(t, err)
 	assert.Empty(t, result)
 }
+
+// hyperguild#149: the REST API requires a bearer token.
+func TestQuerySendsBrainMCPToken(t *testing.T) {
+	var auth string
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		auth = r.Header.Get("Authorization")
+		_, _ = w.Write([]byte(`{"results":[]}`))
+	}))
+	defer srv.Close()
+	t.Setenv("BRAIN_MCP_TOKEN", "lib-test-token")
+	_, _ = brain.Query(context.Background(), srv.URL, "x", 1)
+	if auth != "Bearer lib-test-token" {
+		t.Fatalf("Authorization = %q, want the bearer token", auth)
+	}
+}

scripts/context-sync.sh

@@ -58,7 +58,7 @@ if [ "$FORCE" = false ]; then
     while IFS= read -r _match; do
       _lineno="${_match%%:*}"
       _content="${_match#*:}"
-      _token=$(printf '%s' "$_content" | grep -o '{{[^}]*}}' | head -1)
+      _token=$(head -1 < <(grep -o '{{[^}]*}}' <<<"$_content"))
       echo "  $PROJECT_FILE:$_lineno: unfilled placeholder $_token" >&2
     done <<< "$_placeholders"
     echo "" >&2