fix(ingestion): tripwire alerts survive outages; drop only permanent rejections

PR #160 round 2: dropping a message after 5 failures could not tell a
poison message from an ntfy outage. A 15-minute outage dropped the only
incident with nothing reported, and drops were not counted (74 of 300
removals were neither delivered nor counted).

- audit.NtfyNotifier returns *RejectedError for non-2xx; Permanent() is
  true for 4xx other than 429.
- The tripwire queue drops a message only on a permanent rejection and
  counts it; every other failure is an outage and is retried, however
  long. Each flush tries every queued message, so an undeliverable one
  cannot block the rest.
- Overflow and drops go into one counter, sent as a summary retried
  every tick and never dropped. Every removal is delivered or counted.

Tests (red first): an outage of ~100 ticks still delivers the only
incident; delivered + counted equals the number of removals; a
permanently rejected message is dropped and counted. The short-outage
test is renamed to say it is short. The Watch doc no longer claims
'loses none' unconditionally.

Refs #157

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

ingestion/internal/api/readnote_root_test.go

@@ -1,43 +0,0 @@
-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

@@ -3,18 +3,14 @@ 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
@@ -94,23 +90,14 @@ func UpdateNote(brainDir string, opts UpdateNoteOptions) (relPath, contentHash,
 		rel = filepath.ToSlash(rel)
 	}
 
-	// The path is caller-supplied (brain_update): resolve it as brain_edit
+	rel, abs, err := resolveWithin(brainDir, rel)
-	// 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
-	bfs, err := brainfs.Open(brainDir)
-	if err != nil {
-		return "", "", "", fmt.Errorf("open brain: %w", err)
-	}
-	defer func() { _ = bfs.Close() }()
 
-	prior, err := bfs.ReadRegular(rel)
+	prior, err := os.ReadFile(abs)
 	if err != nil {
-		if errors.Is(err, fs.ErrNotExist) {
+		if os.IsNotExist(err) {
 			return "", "", "", fmt.Errorf("note %q does not exist: use brain_write to create", rel)
 		}
 		return "", "", "", fmt.Errorf("read target: %w", err)
@@ -176,7 +163,7 @@ func UpdateNote(brainDir string, opts UpdateNoteOptions) (relPath, contentHash,
 		return "", "", "", err
 	}
 	out := []byte(stamped)
-	if err := bfs.WriteRegular(rel, out); err != nil {
+	if err := os.WriteFile(abs, out, 0o644); err != nil {
 		return "", "", "", fmt.Errorf("write: %w", err)
 	}
 	return rel, ContentHash(out), priorHash, nil
@@ -187,17 +174,11 @@ 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) {
-	rel, _, err := resolveWithin(brainDir, relPath)
+	_, abs, err := resolveWithin(brainDir, relPath)
 	if err != nil {
 		return nil, "", "", err
 	}
-	// Through the brain root, regular files only (hyperguild#157).
+	raw, err := os.ReadFile(abs)
-	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

@@ -1,112 +0,0 @@
-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/brain/tunnel.go

@@ -4,12 +4,9 @@ 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.
@@ -200,12 +197,6 @@ 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)
@@ -218,50 +209,20 @@ func WriteTunnel(brainDir, sourcePath, targetPath string) error {
 		return fmt.Errorf("tunnel must cross wings; got both in %q", srcWing)
 	}
 
-	// Both notes are read and rewritten through the brain root, regular
+	srcFull := filepath.Join(brainDir, filepath.FromSlash(sourcePath))
-	// files only: brain_tunnel passes caller-supplied paths, and the brain is
+	tgtFull := filepath.Join(brainDir, filepath.FromSlash(targetPath))
-	// a Syncthing folder that can hold symlinks.
+	if _, err := os.Stat(srcFull); err != nil {
-	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)
 	}
-	tgtContent, err := bfs.ReadRegular(targetPath)
+	if _, err := os.Stat(tgtFull); err != nil {
-	if err != nil {
 		return fmt.Errorf("target note: %w", err)
 	}
 
-	if out, changed, err := withSeeAlso(srcContent, wikilinkOf(targetPath)); err != nil {
+	if err := appendSeeAlso(srcFull, 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
 }
@@ -287,13 +248,16 @@ func wingOf(relPath string) (string, error) {
 	return parts[1], nil
 }
 
-// withSeeAlso returns content with `- [[link]]` under its See also section,
+// appendSeeAlso inserts `- [[link]]` under the file's See also section,
-// creating the section if absent. changed is false when the link is already
+// creating the section if absent. No-op when the link is already present.
-// present.
+func appendSeeAlso(filePath, link string) error {
-func withSeeAlso(content []byte, link string) (out []byte, changed bool, err error) {
+	content, err := os.ReadFile(filePath)
+	if err != nil {
+		return err
+	}
 	wikilink := "[[" + link + "]]"
 	if strings.Contains(string(content), wikilink) {
-		return content, false, nil
+		return nil
 	}
 
 	bullet := "- " + wikilink
@@ -302,7 +266,8 @@ func withSeeAlso(content []byte, link string) (out []byte, changed bool, err err
 		// 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")
-		return []byte(trimmed + "\n\n" + seeAlsoHeader + "\n\n" + bullet + "\n"), true, nil
+		out := trimmed + "\n\n" + seeAlsoHeader + "\n\n" + bullet + "\n"
+		return os.WriteFile(filePath, []byte(out), 0o644)
 	}
 
 	// Section exists — splice the bullet in just before the next `## `
@@ -328,11 +293,12 @@ func withSeeAlso(content []byte, link string) (out []byte, changed bool, err err
 		b.WriteByte('\n')
 	}
 	if err := scanner.Err(); err != nil {
-		return nil, false, err
+		return err
 	}
 	if !inserted {
 		// section was the last thing in the file — just append bullet
-		return []byte(strings.TrimRight(b.String(), "\n") + "\n" + bullet + "\n"), true, nil
+		out := strings.TrimRight(b.String(), "\n") + "\n" + bullet + "\n"
+		return os.WriteFile(filePath, []byte(out), 0o644)
 	}
-	return []byte(b.String()), true, nil
+	return os.WriteFile(filePath, []byte(b.String()), 0o644)
 }

ingestion/internal/brain/tunnel_root_test.go

@@ -1,141 +0,0 @@
-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

@@ -1,268 +0,0 @@
-// 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
-}
-
-// ReadDirRegular lists the regular files directly in a brain-relative
-// directory, by name. Every component of relDir must be a real directory
-// (ErrNotRegular otherwise); symlinks, FIFOs, devices and subdirectories in
-// it are left out.
-func (b *Brain) ReadDirRegular(relDir string) ([]string, error) {
-	relDir = filepath.ToSlash(relDir)
-	if err := b.realDir(relDir); err != nil {
-		return nil, err
-	}
-	ents, err := fs.ReadDir(b.root.FS(), relDir)
-	if err != nil {
-		return nil, err
-	}
-	var names []string
-	for _, e := range ents {
-		if e.Type().IsRegular() {
-			names = append(names, e.Name())
-		}
-	}
-	return names, nil
-}
-
-// 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.readOpenedMax(rel, -1, fi)
-}
-
-// 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, nil) }
-
-// 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, fi)
-}
-
-// readOpenedMax opens rel and reads it if the opened handle is a regular file
-// and, when lfi is set, the same file the caller Lstat-ed: os.Root follows an
-// in-root final symlink even with O_NOFOLLOW, so a symlink to another brain
-// file swapped in between the Lstat and the open is refused only here.
-func (b *Brain) readOpenedMax(rel string, max int64, lfi fs.FileInfo) ([]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 lfi != nil && !os.SameFile(lfi, hfi) {
-		return nil, fmt.Errorf("%s: changed while opening: %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)
-	})
-}
-
-// 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()
-}

ingestion/internal/brainfs/brainfs_test.go

@@ -1,310 +0,0 @@
-package brainfs
-
-import (
-	"errors"
-	"io"
-	"io/fs"
-	"os"
-	"path/filepath"
-	"sync"
-	"sync/atomic"
-	"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 TestReadDirRegularListsOnlyRegularFilesAndRefusesSymlinkedComponents(t *testing.T) {
-	dir := t.TempDir()
-	require.NoError(t, os.MkdirAll(filepath.Join(dir, "a", "b", "sub"), 0o755))
-	require.NoError(t, os.WriteFile(filepath.Join(dir, "a", "b", "n.md"), []byte("n"), 0o644))
-	require.NoError(t, os.WriteFile(filepath.Join(dir, "other.md"), []byte("o"), 0o644))
-	require.NoError(t, os.Symlink(filepath.Join("..", "..", "other.md"), filepath.Join(dir, "a", "b", "l.md")))
-	require.NoError(t, syscall.Mkfifo(filepath.Join(dir, "a", "b", "f.md"), 0o644))
-	require.NoError(t, os.Symlink("a", filepath.Join(dir, "alias")))
-	require.NoError(t, os.MkdirAll(filepath.Join(dir, "x"), 0o755))
-	require.NoError(t, os.Symlink(filepath.Join("..", "a"), filepath.Join(dir, "x", "mid")))
-	b, err := Open(dir)
-	require.NoError(t, err)
-	defer func() { _ = b.Close() }()
-
-	names, err := b.ReadDirRegular("a/b")
-	require.NoError(t, err)
-	assert.Equal(t, []string{"n.md"}, names)
-	for _, rel := range []string{"alias/b", "x/mid/b"} {
-		_, err := b.ReadDirRegular(rel)
-		assert.ErrorIs(t, err, ErrNotRegular, rel)
-	}
-}
-
-// A final component swapped for a symlink to another regular file in the
-// brain between the Lstat and the open: os.Root follows in-root links, so
-// only comparing the two (os.SameFile) refuses it.
-func TestReadRegularNeverReturnsAnInBrainFileSwappedInBehindASymlink(t *testing.T) {
-	dir := t.TempDir()
-	require.NoError(t, os.WriteFile(filepath.Join(dir, "s.md"), []byte("zqsamefilesentinel"), 0o644))
-	p := filepath.Join(dir, "r.md")
-	require.NoError(t, os.WriteFile(p, []byte("inside"), 0o644))
-	b, err := Open(dir)
-	require.NoError(t, err)
-	defer func() { _ = b.Close() }()
-
-	var stop atomic.Bool
-	var wg sync.WaitGroup
-	wg.Add(1)
-	go func() {
-		defer wg.Done()
-		tmp := p + ".swap"
-		for i := 0; !stop.Load(); i++ {
-			_ = os.Remove(tmp)
-			if i%2 == 0 {
-				_ = os.WriteFile(tmp, []byte("inside"), 0o644)
-			} else {
-				_ = os.Symlink("s.md", tmp)
-			}
-			_ = os.Rename(tmp, p)
-		}
-	}()
-	leaks, ok := 0, 0
-	for deadline := time.Now().Add(1500 * time.Millisecond); time.Now().Before(deadline); {
-		got, err := b.ReadRegular("r.md")
-		if err == nil {
-			ok++
-		}
-		if string(got) == "zqsamefilesentinel" {
-			leaks++
-		}
-		got, _ = b.ReadRegularMax("r.md", 1<<20)
-		if string(got) == "zqsamefilesentinel" {
-			leaks++
-		}
-	}
-	stop.Store(true)
-	wg.Wait()
-	assert.Zero(t, leaks)
-	assert.Positive(t, ok, "positive control: the regular file is read")
-}
-
-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

@@ -1,141 +0,0 @@
-// 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 (
-	"fmt"
-	"os"
-	"path/filepath"
-	"strings"
-	"sync"
-	"sync/atomic"
-	"syscall"
-	"testing"
-	"time"
-)
-
-// Sentinel marks the outside file's contents.
-const Sentinel = "zqbrainfssentinelonefiftyseven"
-
-// outsideContent carries Sentinel in every field a reader might extract: the
-// frontmatter title and aliases, a heading, a wikilink and the body.
-const outsideContent = "---\ntitle: " + Sentinel + "\naliases:\n  - " + Sentinel + "\n---\n# " + Sentinel +
-	"\n\n" + Sentinel + " [[" + Sentinel + "]]\n"
-
-// 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(outsideContent), 0o644); err != nil {
-		t.Fatal(err)
-	}
-	return p
-}
-
-var swapSeq atomic.Int64
-
-// 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()
-		// A name of its own: swappers on one path share a test, and one
-		// opening another's FIFO for write would block forever.
-		tmp := fmt.Sprintf("%s.swap%d", path, swapSeq.Add(1))
-		// A relative link: os.Root refuses every absolute link on its own, so
-		// an absolute in-brain target would test nothing.
-		link := outside
-		if rel, err := filepath.Rel(filepath.Dir(path), outside); err == nil {
-			link = rel
-		}
-		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(link, tmp)
-			}
-			_ = os.Rename(tmp, path)
-		}
-	}()
-	t.Cleanup(func() { stop.Store(true); wg.Wait() })
-}
-
-// WriteSentinelAt writes a file carrying Sentinel at p (creating its
-// directory), for an in-brain symlink target.
-func WriteSentinelAt(t *testing.T, p string) string {
-	t.Helper()
-	if err := os.MkdirAll(filepath.Dir(p), 0o755); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.WriteFile(p, []byte(outsideContent), 0o644); err != nil {
-		t.Fatal(err)
-	}
-	return p
-}
-
-// AssertNoLeak loops read for d while a symlink swapper runs on path, and
-// fails if any output contains Sentinel. The symlink points outside the
-// brain; os.Root refuses that on its own, so pair it with AssertNoLeakFrom
-// and an in-brain target.
-func AssertNoLeak(t *testing.T, path, inside string, d time.Duration, read func() string) {
-	t.Helper()
-	AssertNoLeakFrom(t, path, inside, Outside(t), d, read)
-}
-
-// AssertNoLeakFrom is AssertNoLeak with the symlink pointing at target, e.g.
-// a file elsewhere in the brain written with WriteSentinelAt.
-func AssertNoLeakFrom(t *testing.T, path, inside, target string, d time.Duration, read func() string) {
-	t.Helper()
-	StartSwap(t, path, inside, target, 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/graphsync/graphsync.go

@@ -12,14 +12,10 @@ package graphsync
 
 import (
 	"context"
-	"errors"
 	"fmt"
-	"io/fs"
+	"os"
-	"path"
 	"path/filepath"
-	"strings"
 
-	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/graph"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/graphstore"
 )
@@ -50,25 +46,8 @@ func IndexDoc(ctx context.Context, store Store, brainDir, relPath string) error
 	if relPath == "" {
 		return nil
 	}
-	// Callers pass caller-supplied paths (brain_tunnel, brain_update): index
+	abs := filepath.Join(brainDir, filepath.FromSlash(relPath))
-	// only a clean path under wiki/ or knowledge/.
+	content, err := os.ReadFile(abs)
-	if path.Clean(relPath) != relPath || !filepath.IsLocal(relPath) ||
-		(!strings.HasPrefix(relPath, "wiki/") && !strings.HasPrefix(relPath, "knowledge/")) {
-		return fmt.Errorf("index %q: not a clean wiki/ or knowledge/ path", relPath)
-	}
-	bfs, err := brainfs.Open(brainDir)
-	if err != nil {
-		return fmt.Errorf("open brain: %w", err)
-	}
-	defer func() { _ = bfs.Close() }()
-	return indexDoc(ctx, store, bfs, relPath)
-}
-
-// indexDoc reads relPath through the brain root, regular files only
-// (hyperguild#157): the brain is a Syncthing folder, and os.ReadFile
-// followed a synced symlink into the graph and blocked on a FIFO.
-func indexDoc(ctx context.Context, store Store, bfs *brainfs.Brain, relPath string) error {
-	content, err := bfs.ReadRegular(relPath)
 	if err != nil {
 		return fmt.Errorf("read %q: %w", relPath, err)
 	}
@@ -98,34 +77,33 @@ func BackfillFromBrainDir(ctx context.Context, store Store, brainDir string) (in
 	if store == nil {
 		return 0, nil
 	}
-	bfs, err := brainfs.Open(brainDir)
+	roots := []string{"wiki", "knowledge"}
-	if err != nil {
+	for _, root := range roots {
-		return 0, fmt.Errorf("open brain: %w", err)
+		base := filepath.Join(brainDir, root)
-	}
+		if _, err := os.Stat(base); os.IsNotExist(err) {
-	defer func() { _ = bfs.Close() }()
-	for _, root := range []string{"wiki", "knowledge"} {
-		if _, err := bfs.Lstat(root); errors.Is(err, fs.ErrNotExist) {
 			continue
 		}
-		// Any walk error, including a root that is a symlink, aborts.
+		err := filepath.WalkDir(base, func(path string, d os.DirEntry, walkErr error) error {
-		var walkErr error
+			if walkErr != nil {
-		err := bfs.WalkRegular(root, func(rel string) error {
+				return walkErr
-			if path.Ext(rel) != ".md" {
+			}
+			if d.IsDir() {
 				return nil
 			}
-			if err := indexDoc(ctx, store, bfs, rel); err != nil {
+			if filepath.Ext(path) != ".md" {
+				return nil
+			}
+			rel, relErr := filepath.Rel(brainDir, path)
+			if relErr != nil {
+				return fmt.Errorf("rel %q: %w", path, relErr)
+			}
+			rel = filepath.ToSlash(rel)
+			if err := IndexDoc(ctx, store, brainDir, rel); err != nil {
 				return fmt.Errorf("index %q: %w", rel, err)
 			}
 			indexed++
 			return nil
-		}, func(rel string, err error) {
-			if walkErr == nil {
-				walkErr = fmt.Errorf("%s: %w", rel, err)
-			}
 		})
-		if err == nil {
-			err = walkErr
-		}
 		if err != nil {
 			return indexed, fmt.Errorf("walk %s: %w", root, err)
 		}

ingestion/internal/graphsync/graphsync_root_test.go

@@ -1,92 +0,0 @@
-package graphsync
-
-import (
-	"context"
-	"fmt"
-	"os"
-	"path/filepath"
-	"testing"
-	"time"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-
-	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs/brainfstest"
-)
-
-func (f *fakeStore) dump() string {
-	f.mu.Lock()
-	defer f.mu.Unlock()
-	return fmt.Sprintf("%+v %+v", f.upserts, f.replaces)
-}
-
-// hyperguild#157 slice 4: IndexDoc and BackfillFromBrainDir read notes with
-// os.ReadFile, so a symlinked note put the target's title and wikilinks into
-// the graph, and a FIFO hung the read.
-func TestIndexDocRefusesSymlinksAndSurvivesSwapRaces(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, "ok.md"), []byte("---\ntitle: zqinside\n---\nbody [[other]]\n"), 0o644))
-	require.NoError(t, os.Symlink(brainfstest.Outside(t), filepath.Join(facts, "leak.md")))
-
-	store := newFakeStore()
-	require.NoError(t, IndexDoc(context.Background(), store, brain, "wiki/w/facts/ok.md"))
-	assert.Contains(t, store.dump(), "zqinside", "positive control: a regular note is indexed")
-	assert.Error(t, IndexDoc(context.Background(), store, brain, "wiki/w/facts/leak.md"))
-	// A link to a file elsewhere in the brain: os.Root allows it, only the
-	// regular-file check refuses it.
-	inBrain := brainfstest.WriteSentinelAt(t, filepath.Join(brain, "raw", "s.md"))
-	require.NoError(t, os.Symlink(filepath.Join("..", "..", "..", "raw", "s.md"), filepath.Join(facts, "inlink.md")))
-	assert.Error(t, IndexDoc(context.Background(), store, brain, "wiki/w/facts/inlink.md"))
-	assert.NotContains(t, store.dump(), brainfstest.Sentinel)
-
-	p := filepath.Join(facts, "r.md")
-	read := func() string {
-		s := newFakeStore()
-		_ = IndexDoc(context.Background(), s, brain, "wiki/w/facts/r.md")
-		return s.dump()
-	}
-	brainfstest.AssertNoLeak(t, p, "---\ntitle: zqinside\n---\n", 1500*time.Millisecond, read)
-	brainfstest.AssertNoLeakFrom(t, p, "---\ntitle: zqinside\n---\n", inBrain, 1500*time.Millisecond, read)
-	brainfstest.AssertNoHang(t, p, "---\ntitle: zqinside\n---\n", 1500*time.Millisecond, 6*time.Second, func() { _ = read() })
-}
-
-func TestBackfillSkipsSymlinkedNotesAndAbortsOnASymlinkedRoot(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, "ok.md"), []byte("---\ntitle: zqinside\n---\n"), 0o644))
-	require.NoError(t, os.Symlink(brainfstest.Outside(t), filepath.Join(facts, "leak.md")))
-	require.NoError(t, os.MkdirAll(filepath.Join(brain, "raw"), 0o755))
-	require.NoError(t, os.WriteFile(filepath.Join(brain, "raw", "r.md"), []byte("---\ntitle: zqrawonly\n---\n"), 0o644))
-	require.NoError(t, os.Symlink(filepath.Join("..", "..", "..", "raw", "r.md"), filepath.Join(facts, "inlink.md")))
-	require.NoError(t, os.Symlink(".", filepath.Join(brain, "knowledge")))
-
-	store := newFakeStore()
-	_, err := BackfillFromBrainDir(context.Background(), store, brain)
-	assert.Error(t, err, "a symlinked root aborts the backfill")
-	assert.NotContains(t, store.dump(), brainfstest.Sentinel)
-	assert.NotContains(t, store.dump(), "zqrawonly")
-
-	require.NoError(t, os.Remove(filepath.Join(brain, "knowledge")))
-	store = newFakeStore()
-	n, err := BackfillFromBrainDir(context.Background(), store, brain)
-	require.NoError(t, err)
-	assert.Equal(t, 1, n, "only the regular note is indexed")
-	assert.Contains(t, store.dump(), "zqinside")
-	assert.NotContains(t, store.dump(), brainfstest.Sentinel)
-}
-
-// IndexDoc gets caller-supplied paths (brain_tunnel, brain_update): only a
-// clean path under wiki/ or knowledge/ is indexed.
-func TestIndexDocRefusesPathsOutsideWikiAndKnowledgeAndUncleanPaths(t *testing.T) {
-	brain := t.TempDir()
-	brainfstest.WriteSentinelAt(t, filepath.Join(brain, "raw", "secret.md"))
-	require.NoError(t, os.MkdirAll(filepath.Join(brain, "wiki", "w"), 0o755))
-	for _, p := range []string{"raw/secret.md", "wiki/w/../../raw/secret.md", "./raw/secret.md", "/raw/secret.md"} {
-		store := newFakeStore()
-		assert.Error(t, IndexDoc(context.Background(), store, brain, p), p)
-		assert.NotContains(t, store.dump(), brainfstest.Sentinel, p)
-	}
-}

ingestion/internal/mcp/readexcerpt_root_test.go

@@ -1,34 +0,0 @@
-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/tools_context.go

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

ingestion/internal/notes/edit.go

@@ -5,7 +5,6 @@ import (
 	"encoding/hex"
 	"errors"
 	"fmt"
-	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
 	"os"
 	"path/filepath"
 	"strings"
@@ -72,18 +71,14 @@ func ReadScoped(brainDir, path string, scope Scope) ([]byte, error) {
 }
 
 func readContained(t Target) ([]byte, error) {
-	// Through the brain root, regular files only, size checked on the opened
+	fi, err := os.Stat(t.Abs)
-	// 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: %w", err)
+		return nil, fmt.Errorf("notes: stat %s: %w", t.Rel, err)
 	}
-	defer func() { _ = bfs.Close() }()
+	if fi.Size() > maxNoteBytes {
-	b, err := bfs.ReadRegularMax(t.Rel, maxNoteBytes)
+		return nil, fmt.Errorf("%w: %s is %d bytes (limit %d)", ErrTooLarge, t.Rel, fi.Size(), 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

@@ -60,7 +60,6 @@ var (
 type Target struct {
 	Rel string // brain-relative, cleaned
 	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,
@@ -110,7 +109,7 @@ func Resolve(brainDir, path string, scope Scope) (Target, error) {
 		return Target{}, err
 	}
 
-	return Target{Rel: clean, Abs: abs, Brain: brainDir}, nil
+	return Target{Rel: clean, Abs: abs}, nil
 }
 
 // allow enforces the scope's allowlist. The two scopes are DISJOINT, not

ingestion/internal/notes/read_root_test.go

@@ -1,40 +0,0 @@
-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/search/brainroot_test.go

@@ -1,174 +0,0 @@
-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/search.go

@@ -5,7 +5,6 @@ import (
 	"bufio"
 	"context"
 	"fmt"
-	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
 	sharedfm "github.com/mathiasbq/hyperguild/ingestion/internal/frontmatter"
 	"log/slog"
 	"os"
@@ -120,30 +119,20 @@ 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
 		}
-		relDir, relErr := bfs.Rel(dir)
+		err := filepath.WalkDir(dir, func(path string, d os.DirEntry, err error) error {
-		if relErr != nil {
+			if err != nil {
-			return nil, fmt.Errorf("search: %w", relErr)
+				slog.Warn("search: skipping path", "path", path, "err", err)
-		}
-		err := bfs.WalkRegular(relDir, func(relPath string) error {
-			if !strings.HasSuffix(relPath, ".md") {
 				return nil
 			}
-			path := filepath.Join(brainDir, filepath.FromSlash(relPath))
+			if d.IsDir() || !strings.HasSuffix(path, ".md") {
-			content, err := bfs.ReadRegular(relPath)
+				return nil
+			}
+			content, err := os.ReadFile(path)
 			if err != nil {
 				slog.Warn("search: skipping unreadable file", "path", path, "err", err)
 				return nil
@@ -166,7 +155,7 @@ func QueryContext(ctx context.Context, brainDir string, opts QueryOptions) ([]Re
 			origin, writtenBy := extractProvenance(string(content))
 			results = append(results, Result{
 				Path:    rel,
-				Title:   extractTitle(string(content), filepath.Base(relPath)),
+				Title:   extractTitle(string(content), d.Name()),
 				Excerpt: excerpt(string(content), 300),
 				Score:   score,
 				Wing:    wing,
@@ -177,8 +166,6 @@ func QueryContext(ctx context.Context, brainDir string, opts QueryOptions) ([]Re
 				WrittenBy: writtenBy,
 			})
 			return nil
-		}, func(p string, err error) {
-			slog.Warn("search: skipping path", "path", p, "err", err)
 		})
 		if err != nil {
 			return nil, err
@@ -288,13 +275,8 @@ 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) {
-	// Through the brain root, regular files only (hyperguild#157).
+	full := filepath.Join(brainDir, filepath.FromSlash(relPath))
-	bfs, err := brainfs.Open(brainDir)
+	content, err := os.ReadFile(full)
-	if err != nil {
-		return Result{}, err
-	}
-	defer func() { _ = bfs.Close() }()
-	content, err := bfs.ReadRegular(filepath.ToSlash(relPath))
 	if err != nil {
 		return Result{}, err
 	}

ingestion/internal/session/id_test.go

@@ -1,92 +0,0 @@
-package session
-
-import (
-	"errors"
-	"os"
-	"path/filepath"
-	"syscall"
-	"testing"
-	"time"
-
-	"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)
-}
-
-// A name that starts plainly and then climbs out with ".." is exactly what the
-// ban on "/" in the id's tail stops: filepath.Join cleans "a/../../x" to a
-// path beside the sessions dir without needing sessions/a to exist. The
-// assertion is on the refusal itself (ErrInvalidID), not on any error.
-func TestAppendRefusesAnIDThatClimbsOutAfterAPlainPrefix(t *testing.T) {
-	root := t.TempDir()
-	dir := filepath.Join(root, "sessions")
-	require.NoError(t, os.MkdirAll(dir, 0o755))
-	for _, id := range []string{"a/../../escape", "a/../../../escape", "a/../b"} {
-		err := Append(dir, id, Entry{SessionID: id})
-		assert.ErrorIs(t, err, ErrInvalidID, "%q", id)
-	}
-	_, err := os.Lstat(filepath.Join(root, "escape.jsonl"))
-	assert.True(t, errors.Is(err, os.ErrNotExist), "nothing created beside the sessions dir")
-	_, err = os.Lstat(filepath.Join(dir, "b.jsonl"))
-	assert.True(t, errors.Is(err, os.ErrNotExist), "no in-dir alias created either")
-}
-
-// Append does no Lstat type check, so O_NONBLOCK is the only thing that keeps
-// a FIFO named <id>.jsonl with no reader from blocking session_log forever.
-func TestAppendReturnsPromptlyOnAFIFOLogWithNoReader(t *testing.T) {
-	dir := filepath.Join(t.TempDir(), "sessions")
-	require.NoError(t, os.MkdirAll(dir, 0o755))
-	fifo := filepath.Join(dir, "s.jsonl")
-	require.NoError(t, syscall.Mkfifo(fifo, 0o644))
-	done := make(chan error, 1)
-	go func() { done <- Append(dir, "s", Entry{SessionID: "s"}) }()
-	select {
-	case err := <-done:
-		assert.Error(t, err, "a FIFO with no reader is refused, not written")
-	case <-time.After(3 * time.Second):
-		// Unblock the stuck open so the goroutine and TempDir cleanup finish.
-		if r, err := os.OpenFile(fifo, os.O_RDONLY|syscall.O_NONBLOCK, 0); err == nil {
-			defer r.Close() //nolint:errcheck
-		}
-		<-done
-		t.Fatal("Append blocked on a FIFO log with no reader")
-	}
-}

ingestion/internal/session/session.go

@@ -9,8 +9,6 @@ import (
 	"io/fs"
 	"os"
 	"path/filepath"
-	"regexp"
-	"syscall"
 	"time"
 )
 
@@ -44,32 +42,13 @@ 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}$`)
-
-// ErrInvalidID is returned when a session id is not a plain file name.
-var ErrInvalidID = errors.New("session id is not a plain name")
-
-func checkID(sessionID string) error {
-	if !idPattern.MatchString(sessionID) {
-		return fmt.Errorf("%w: %q", ErrInvalidID, 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|syscall.O_NOFOLLOW|syscall.O_NONBLOCK, 0o644)
+	f, err := os.OpenFile(path, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0o644)
 	if err != nil {
 		return fmt.Errorf("open session log: %w", err)
 	}
@@ -91,9 +70,6 @@ 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/vectorstore/sync.go

@@ -2,15 +2,12 @@ package vectorstore
 
 import (
 	"context"
-	"errors"
 	"fmt"
-	"io/fs"
 	"log/slog"
-	"path"
+	"os"
+	"path/filepath"
 	"strings"
 	"time"
-
-	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
 )
 
 // Embedder produces dense vectors. The embed package's Client satisfies
@@ -93,38 +90,31 @@ 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 {
-		if _, err := bfs.Lstat(sub); errors.Is(err, fs.ErrNotExist) {
+		root := filepath.Join(brainDir, sub)
+		if _, err := os.Stat(root); os.IsNotExist(err) {
 			continue
 		}
-		// Any other walk error, including a scan root that is a symlink,
+
-		// aborts the run below.
+		err = filepath.WalkDir(root, func(path string, d os.DirEntry, err error) error {
-		var walkErr error
+			if err != nil {
-		onErr := func(rel string, err error) {
+				return err
-			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 := bfs.Lstat(relSlash)
+				info, statErr := d.Info()
 				if statErr != nil {
 					res.Errors = append(res.Errors, fmt.Errorf("stat %s: %w", relSlash, statErr))
 					return nil
@@ -142,7 +132,7 @@ func Sync(ctx context.Context, brainDir string, store Store, embedder Embedder)
 				}
 			}
 
-			content, readErr := bfs.ReadRegular(relSlash)
+			content, readErr := os.ReadFile(path)
 			if readErr != nil {
 				res.Errors = append(res.Errors, fmt.Errorf("read %s: %w", relSlash, readErr))
 				return nil
@@ -161,12 +151,7 @@ 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

@@ -1,126 +0,0 @@
-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/wiki/index.go

@@ -7,7 +7,6 @@ import (
 	"path/filepath"
 	"strings"
 
-	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
 	"github.com/mathiasbq/hyperguild/ingestion/internal/textutil"
 )
 
@@ -17,11 +16,6 @@ func RebuildIndex(brainDir, date string) error {
 	if err != nil {
 		return fmt.Errorf("load inventory: %w", err)
 	}
-	bfs, err := brainfs.Open(brainDir)
-	if err != nil {
-		return fmt.Errorf("open brain: %w", err)
-	}
-	defer func() { _ = bfs.Close() }()
 
 	total := len(inv[PageTypeConcept]) + len(inv[PageTypeEntity]) + len(inv[PageTypeSource])
 	var sb strings.Builder
@@ -40,7 +34,7 @@ func RebuildIndex(brainDir, date string) error {
 		label := strings.ToUpper(string(pt)[:1]) + string(pt)[1:]
 		fmt.Fprintf(&sb, "## %s\n\n", label)
 		for _, e := range entries {
-			summary := pageFirstSentence(bfs, e)
+			summary := pageFirstSentence(brainDir, e)
 			if summary != "" {
 				fmt.Fprintf(&sb, "- [[%s|%s]] — %s\n", e.Slug, e.Title, summary)
 			} else {
@@ -54,10 +48,9 @@ func RebuildIndex(brainDir, date string) error {
 	return os.WriteFile(dest, []byte(sb.String()), 0o644)
 }
 
-// pageFirstSentence reads the page through the brain root, regular files
+func pageFirstSentence(brainDir string, e Entry) string {
-// only (hyperguild#157).
+	path := filepath.Join(brainDir, "wiki", string(e.Type), e.Slug+".md")
-func pageFirstSentence(bfs *brainfs.Brain, e Entry) string {
+	content, err := os.ReadFile(path)
-	content, err := bfs.ReadRegular("wiki/" + string(e.Type) + "/" + e.Slug + ".md")
 	if err != nil {
 		return ""
 	}

ingestion/internal/wiki/inventory.go

@@ -3,45 +3,36 @@ package wiki
 
 import (
 	"bufio"
-	"bytes"
-	"errors"
 	"fmt"
-	"io/fs"
+	"os"
+	"path/filepath"
 	"strings"
-
-	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
 )
 
 // LoadInventory walks brain/wiki/ and returns all pages grouped by type.
-// Missing subdirectories are silently skipped. Pages are listed and read
+// Missing subdirectories are silently skipped.
-// through the brain root, regular files only (hyperguild#157); a type
-// directory that is a symlink is an error.
 func LoadInventory(brainDir string) (map[PageType][]Entry, error) {
 	result := map[PageType][]Entry{
 		PageTypeConcept: {},
 		PageTypeEntity:  {},
 		PageTypeSource:  {},
 	}
-	bfs, err := brainfs.Open(brainDir)
-	if err != nil {
-		return nil, fmt.Errorf("open brain: %w", err)
-	}
-	defer func() { _ = bfs.Close() }()
 	for pt := range result {
-		dir := "wiki/" + string(pt)
+		dir := filepath.Join(brainDir, "wiki", string(pt))
-		names, err := bfs.ReadDirRegular(dir)
+		entries, err := os.ReadDir(dir)
-		if errors.Is(err, fs.ErrNotExist) {
+		if os.IsNotExist(err) {
 			continue
 		}
 		if err != nil {
 			return nil, fmt.Errorf("read dir %s: %w", dir, err)
 		}
-		for _, name := range names {
+		for _, e := range entries {
-			if !strings.HasSuffix(name, ".md") {
+			if e.IsDir() || !strings.HasSuffix(e.Name(), ".md") {
 				continue
 			}
-			slug := strings.TrimSuffix(name, ".md")
+			slug := strings.TrimSuffix(e.Name(), ".md")
-			title, aliases := readFrontmatter(bfs, dir+"/"+name, slug)
+			path := filepath.Join(dir, e.Name())
+			title, aliases := readFrontmatter(path, slug)
 			result[pt] = append(result[pt], Entry{Slug: slug, Title: title, Aliases: aliases, Type: pt})
 		}
 	}
@@ -50,14 +41,15 @@ func LoadInventory(brainDir string) (map[PageType][]Entry, error) {
 
 // readFrontmatter extracts title and aliases from YAML frontmatter.
 // Falls back to slug for title and empty aliases on any error.
-func readFrontmatter(bfs *brainfs.Brain, rel, fallbackSlug string) (title string, aliases []string) {
+func readFrontmatter(path, fallbackSlug string) (title string, aliases []string) {
 	title = fallbackSlug
-	content, err := bfs.ReadRegular(rel)
+	f, err := os.Open(path)
 	if err != nil {
 		return
 	}
+	defer f.Close() //nolint:errcheck
 
-	scanner := bufio.NewScanner(bytes.NewReader(content))
+	scanner := bufio.NewScanner(f)
 	inFM := false
 	inAliases := false
 	for scanner.Scan() {

ingestion/internal/wiki/root_test.go

@@ -1,79 +0,0 @@
-package wiki
-
-import (
-	"fmt"
-	"os"
-	"path/filepath"
-	"testing"
-	"time"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-
-	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs"
-	"github.com/mathiasbq/hyperguild/ingestion/internal/brainfs/brainfstest"
-)
-
-// hyperguild#157 slice 4: LoadInventory listed wiki/<type>/ with os.ReadDir
-// and opened each .md by path, so a symlinked page put the target's title and
-// aliases into the inventory (and the LLM prompts built from it), and a FIFO
-// hung it. RebuildIndex read first sentences the same way.
-func TestLoadInventoryRefusesSymlinksAndSurvivesSwapRaces(t *testing.T) {
-	brain := t.TempDir()
-	dir := filepath.Join(brain, "wiki", "concepts")
-	require.NoError(t, os.MkdirAll(dir, 0o755))
-	require.NoError(t, os.WriteFile(filepath.Join(dir, "ok.md"), []byte("---\ntitle: zqinside\n---\n"), 0o644))
-	require.NoError(t, os.Symlink(brainfstest.Outside(t), filepath.Join(dir, "leak.md")))
-	inBrain := brainfstest.WriteSentinelAt(t, filepath.Join(brain, "raw", "s.md"))
-	require.NoError(t, os.Symlink(filepath.Join("..", "..", "raw", "s.md"), filepath.Join(dir, "inlink.md")))
-
-	inv, err := LoadInventory(brain)
-	require.NoError(t, err)
-	got := fmt.Sprintf("%+v", inv)
-	assert.Contains(t, got, "zqinside", "positive control")
-	assert.NotContains(t, got, brainfstest.Sentinel)
-	assert.NotContains(t, got, "leak", "a symlinked page is not listed")
-	assert.NotContains(t, got, "inlink", "a page linked to another brain file is not listed")
-
-	p := filepath.Join(dir, "r.md")
-	read := func() string {
-		inv, _ := LoadInventory(brain)
-		return fmt.Sprintf("%+v", inv)
-	}
-	brainfstest.AssertNoLeak(t, p, "---\ntitle: zqinside\n---\n", 1500*time.Millisecond, read)
-	brainfstest.AssertNoLeakFrom(t, p, "---\ntitle: zqinside\n---\n", inBrain, 1500*time.Millisecond, read)
-	brainfstest.AssertNoHang(t, p, "---\ntitle: zqinside\n---\n", 1500*time.Millisecond, 6*time.Second, func() { _ = read() })
-}
-
-func TestLoadInventoryReturnsErrNotRegularForASymlinkedTypeDir(t *testing.T) {
-	brain := t.TempDir()
-	require.NoError(t, os.MkdirAll(filepath.Join(brain, "wiki"), 0o755))
-	require.NoError(t, os.MkdirAll(filepath.Join(brain, "raw"), 0o755))
-	require.NoError(t, os.WriteFile(filepath.Join(brain, "raw", "r.md"), []byte("---\ntitle: zqrawonly\n---\n"), 0o644))
-	require.NoError(t, os.Symlink(filepath.Join("..", "raw"), filepath.Join(brain, "wiki", "concepts")))
-	inv, err := LoadInventory(brain)
-	require.ErrorIs(t, err, brainfs.ErrNotRegular)
-	assert.NotContains(t, fmt.Sprintf("%+v", inv), "zqrawonly")
-}
-
-func TestRebuildIndexDoesNotReadAPageSwappedForASymlink(t *testing.T) {
-	brain := t.TempDir()
-	dir := filepath.Join(brain, "wiki", "concepts")
-	require.NoError(t, os.MkdirAll(dir, 0o755))
-	p := filepath.Join(dir, "r.md")
-	require.NoError(t, os.WriteFile(p, []byte("---\ntitle: R\n---\nzqinside sentence.\n"), 0o644))
-	require.NoError(t, RebuildIndex(brain, "2026-10-04"))
-	idx, err := os.ReadFile(filepath.Join(brain, "wiki", "index.md"))
-	require.NoError(t, err)
-	require.Contains(t, string(idx), "zqinside", "positive control: the summary is read")
-
-	read := func() string {
-		_ = RebuildIndex(brain, "2026-10-04")
-		b, _ := os.ReadFile(filepath.Join(brain, "wiki", "index.md"))
-		return string(b)
-	}
-	brainfstest.AssertNoLeak(t, p, "---\ntitle: R\n---\nzqinside sentence.\n", 1500*time.Millisecond, read)
-	inBrain := brainfstest.WriteSentinelAt(t, filepath.Join(brain, "raw", "s.md"))
-	brainfstest.AssertNoLeakFrom(t, p, "---\ntitle: R\n---\nzqinside sentence.\n", inBrain, 1500*time.Millisecond, read)
-	brainfstest.AssertNoHang(t, p, "---\ntitle: R\n---\nzqinside sentence.\n", 1500*time.Millisecond, 6*time.Second, func() { _ = read() })
-}