fix(brain): provenance as a post-condition on every model-reachable write

The PR #147 review forged origin: static as a JWT principal through
three tools the first version never touched (brain_edit, brain_ingest_raw,
ingest_raw + brain_promote), and through YAML spellings a key-name match
missed (quoted, escaped, tagged, flow-mapped, merge keys, lone CR).

- api.StampProvenance removes every spelling of origin/written_by from
  the frontmatter and appends the real values. A line is dropped if
  EITHER yaml.v3 (decoding quotes, escapes, tags, flow maps) or the
  brain's line-oriented readers would read it as provenance; complex
  keys, orphan values and merge keys are dropped outright. Lone CRs in
  frontmatter become LF. Principal values that are not bare words are
  quoted.
- Applied as the last step of writeHallNote, UpdateNote, PromoteNote
  (re-attributed to the promoter), brain_edit (re-attributed to the
  editor) and both ingests (every page written or merged). REST
  /write and /promote carry no principal and stamp unknown.
- Ingest: newlines in scalar fields fold to spaces; a page type must be
  a plain lower-case name (../raw wrote outside wiki/, pre-existing).
- Audit: outcome is ok|error, never the error text, which echoed
  argument values.

Tests: every escape from the review is a table case asserting the
invariant on the file (parses as YAML, yaml.v3 and brain_get agree,
exactly the stamped lines). Plus REST /write, REST capture AuthPath,
body-line provenance in search, and quoted principals; two of the
review's surviving flips now go red. Three tests renamed so names claim
only what they assert.

Refs #145 #144

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

ingestion/internal/mcp/audit.go

@@ -35,12 +35,13 @@ func logToolCall(ctx context.Context, name string, args json.RawMessage, start t
 			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 = err.Error()
-		if len(outcome) > 200 {
-			outcome = outcome[:200]
-		}
+		outcome = "error"
 	}
 	attrs = append(attrs, "outcome", outcome)
 	slog.InfoContext(ctx, "mcp tool call", attrs...)

ingestion/internal/mcp/audit_test.go

@@ -64,7 +64,7 @@ func TestToolsCallLogsErrorOutcome(t *testing.T) {
 		authCall(t, srv, "Bearer "+capStaticTok, "brain_query", map[string]any{})
 	})
 	require.Len(t, recs, 1)
-	assert.Contains(t, recs[0]["outcome"], "query is required")
+	assert.Equal(t, "error", recs[0]["outcome"])
 }
 
 // The audit line must not become a second copy of brain content.

ingestion/internal/mcp/handlers.go

@@ -393,8 +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
@@ -510,6 +512,9 @@ func (s *Server) brainIngestRaw(ctx context.Context, args json.RawMessage) (json
 		warnings = []string{}
 	}
 	if !a.DryRun {
+		if err := s.stampPages(ctx, pages); err != nil {
+			return nil, err
+		}
 		for _, p := range pages {
 			s.indexInGraph(ctx, "brain_ingest_raw", p)
 		}
@@ -605,6 +610,9 @@ func (s *Server) runIngest(ctx context.Context, content, source string, dryRun b
 		pages = []string{}
 	}
 	if !dryRun {
+		if err := s.stampPages(ctx, pages); err != nil {
+			return nil, err
+		}
 		for _, p := range pages {
 			s.indexInGraph(ctx, "brain_ingest", p)
 		}
@@ -615,3 +623,16 @@ func (s *Server) runIngest(ctx context.Context, content, source string, dryRun b
 	}
 	return json.Marshal(map[string]any{"pages": pages, "warnings": warnings})
 }
+
+// stampPages attributes every page an ingest wrote (or merged into) to the
+// calling principal (hyperguild#145). Ingest builds frontmatter itself, so
+// without this its pages carried no provenance at all.
+func (s *Server) stampPages(ctx context.Context, pages []string) error {
+	origin, writtenBy := provenanceFrom(ctx)
+	for _, p := range pages {
+		if err := api.StampProvenanceFile(s.brainDir, p, origin, writtenBy); err != nil {
+			return fmt.Errorf("stamp provenance: %w", err)
+		}
+	}
+	return nil
+}

ingestion/internal/mcp/provenance_escapes_test.go

@@ -0,0 +1,227 @@
+package mcp_test
+
+import (
+	"bytes"
+	"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"
+)
+
+// 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"},
+}
+
+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")
+}
+
+// E2 + E4: brain_ingest_raw stamps every page it writes, and a newline in a
+// title cannot start a new frontmatter key.
+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)
+	}
+}
+
+// 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")
+}

ingestion/internal/mcp/provenance_test.go

@@ -61,7 +61,7 @@ func TestBrainWriteWithoutPrincipalStampsOriginUnknown(t *testing.T) {
 
 // The control: a caller cannot claim a more trusted origin by putting it in
 // its own frontmatter.
-func TestBrainWriteOverwritesCallerSuppliedProvenance(t *testing.T) {
+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{
@@ -76,7 +76,7 @@ func TestBrainWriteOverwritesCallerSuppliedProvenance(t *testing.T) {
 
 // brain_update replaces the content wholesale, so provenance follows the
 // last writer — and a forged fragment must not survive the merge either.
-func TestBrainUpdateRestampsProvenanceAndIgnoresForgedFragment(t *testing.T) {
+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",
@@ -106,7 +106,7 @@ func TestBrainQueryReturnsProvenance(t *testing.T) {
 
 // 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 TestCaptureStampsJWTProvenance(t *testing.T) {
+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"},

ingestion/internal/mcp/tools_notes.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/api"
 	"log/slog"
 	"strings"
 	"time"
@@ -103,9 +104,19 @@ 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) {
-	_, out, err := s.editWithScope(args, notes.ScopeNotes)
-	return out, err
+func (s *Server) brainEdit(ctx context.Context, args json.RawMessage) (json.RawMessage, error) {
+	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 {
+		return nil, fmt.Errorf("stamp provenance: %w", serr)
+	}
+	return out, nil
 }
 
 // brainEditRoot edits a governance file (CLAUDE.md). De-surfaced AND gated on

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 may change")
+	// Only the matched bytes change in the body; the one deliberate addition
+	// 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) {