diff --git a/ingestion/internal/brain/detect_root_test.go b/ingestion/internal/brain/detect_root_test.go
index 93d5162..c5f451c 100644
--- a/ingestion/internal/brain/detect_root_test.go
+++ b/ingestion/internal/brain/detect_root_test.go
@@ -19,25 +19,37 @@ import (
 // every note with a blocking os.Open, so a FIFO named *.md anywhere under
 // wiki/ hung every brain_write and brain_update (wikiUpkeep -> AutoTunnel),
 // and a symlinked note's title became a tunnel candidate.
-func TestDetectTunnelsReturnsPromptlyWithAFIFOUnderWiki(t *testing.T) {
-	b := t.TempDir()
-	facts := filepath.Join(b, "wiki", "w", "facts")
-	require.NoError(t, os.MkdirAll(facts, 0o755))
-	require.NoError(t, os.WriteFile(filepath.Join(facts, "ok.md"), []byte("---\ntitle: Zqinside Phrase\n---\n"), 0o644))
-	require.NoError(t, syscall.Mkfifo(filepath.Join(facts, "f.md"), 0o644))
-	done := make(chan []brain.TunnelCandidate, 1)
-	go func() {
-		cs, _ := brain.DetectTunnels(b, "text mentioning zqinside phrase here")
-		done <- cs
-	}()
-	select {
-	case cs := <-done:
-		assert.Contains(t, fmt.Sprintf("%+v", cs), "Zqinside Phrase", "positive control")
-	case <-time.After(3 * time.Second):
-		if r, err := os.OpenFile(filepath.Join(facts, "f.md"), os.O_WRONLY|syscall.O_NONBLOCK, 0); err == nil {
-			_ = r.Close()
-		}
-		t.Fatal("DetectTunnels blocked on a FIFO")
+func TestDetectTunnelsReturnsPromptlyWithAFIFOUnderWikiWithAndWithoutAWriter(t *testing.T) {
+	for _, withWriter := range []bool{false, true} {
+		t.Run(fmt.Sprintf("writer=%v", withWriter), func(t *testing.T) {
+			b := t.TempDir()
+			facts := filepath.Join(b, "wiki", "w", "facts")
+			require.NoError(t, os.MkdirAll(facts, 0o755))
+			require.NoError(t, os.WriteFile(filepath.Join(facts, "ok.md"), []byte("---\ntitle: Zqinside Phrase\n---\n"), 0o644))
+			fifo := filepath.Join(facts, "f.md")
+			require.NoError(t, syscall.Mkfifo(fifo, 0o644))
+			if withWriter {
+				// A writer held open: a reader that opens the FIFO gets no
+				// EOF and parks, unless the FIFO is never opened.
+				w, err := os.OpenFile(fifo, os.O_RDWR, 0)
+				require.NoError(t, err)
+				t.Cleanup(func() { _ = w.Close() })
+			}
+			done := make(chan []brain.TunnelCandidate, 1)
+			go func() {
+				cs, _ := brain.DetectTunnels(b, "text mentioning zqinside phrase here")
+				done <- cs
+			}()
+			select {
+			case cs := <-done:
+				assert.Contains(t, fmt.Sprintf("%+v", cs), "Zqinside Phrase", "positive control")
+			case <-time.After(3 * time.Second):
+				if r, err := os.OpenFile(fifo, os.O_WRONLY|syscall.O_NONBLOCK, 0); err == nil {
+					_ = r.Close()
+				}
+				t.Fatal("DetectTunnels blocked on a FIFO")
+			}
+		})
 	}
 }
 
@@ -45,16 +57,18 @@ func TestDetectTunnelsRefusesSymlinkedNotesAndSurvivesSwapRaces(t *testing.T) {
 	b := t.TempDir()
 	facts := filepath.Join(b, "wiki", "w", "facts")
 	require.NoError(t, os.MkdirAll(facts, 0o755))
-	require.NoError(t, os.WriteFile(filepath.Join(facts, "ok.md"), []byte("---\ntitle: Zqinside Phrase\n---\n"), 0o644))
+	// The static note's title differs from the raced note's, so the
+	// harness's "inside was read" floor can only be met by reading r.md.
+	require.NoError(t, os.WriteFile(filepath.Join(facts, "ok.md"), []byte("---\ntitle: Zqstatic Words\n---\n"), 0o644))
 	require.NoError(t, os.Symlink(brainfstest.Outside(t), filepath.Join(facts, "out.md")))
 	inBrain := brainfstest.WriteSentinelAt(t, filepath.Join(b, "raw", "s.md"))
 	require.NoError(t, os.Symlink(filepath.Join("..", "..", "..", "raw", "s.md"), filepath.Join(facts, "in.md")))
-	content := "zqinside phrase and " + brainfstest.Sentinel
+	content := "zqstatic words, zqinside phrase and " + brainfstest.Sentinel
 
 	cs, err := brain.DetectTunnels(b, content)
 	require.NoError(t, err)
 	got := fmt.Sprintf("%+v", cs)
-	assert.Contains(t, got, "Zqinside Phrase", "positive control")
+	assert.Contains(t, got, "Zqstatic Words", "positive control")
 	assert.NotContains(t, got, brainfstest.Sentinel)
 
 	p := filepath.Join(facts, "r.md")
@@ -77,3 +91,35 @@ func TestDetectTunnelsSkipsAWikiThatIsNotARealDirectory(t *testing.T) {
 	require.NoError(t, err)
 	assert.Empty(t, cs)
 }
+
+// An unreadable directory under wiki/ is a walk error and DetectTunnels
+// reports it, as filepath.WalkDir did; it is not silently dropped.
+func TestDetectTunnelsReportsAnUnreadableDirectoryUnderWiki(t *testing.T) {
+	if os.Geteuid() == 0 {
+		t.Skip("root ignores directory permissions")
+	}
+	b := t.TempDir()
+	require.NoError(t, os.MkdirAll(filepath.Join(b, "wiki", "w", "facts"), 0o755))
+	require.NoError(t, os.WriteFile(filepath.Join(b, "wiki", "w", "facts", "ok.md"), []byte("---\ntitle: Zqinside Phrase\n---\n"), 0o644))
+	locked := filepath.Join(b, "wiki", "other", "locked")
+	require.NoError(t, os.MkdirAll(locked, 0o755))
+	require.NoError(t, os.Chmod(locked, 0o000))
+	t.Cleanup(func() { _ = os.Chmod(locked, 0o755) })
+	_, err := brain.DetectTunnels(b, "zqinside phrase")
+	assert.ErrorIs(t, err, os.ErrPermission)
+}
+
+// _index.md files are generated, not notes: their title never becomes a
+// candidate.
+func TestDetectTunnelsSkipsIndexFiles(t *testing.T) {
+	b := t.TempDir()
+	w := filepath.Join(b, "wiki", "w")
+	require.NoError(t, os.MkdirAll(filepath.Join(w, "facts"), 0o755))
+	require.NoError(t, os.WriteFile(filepath.Join(w, "_index.md"), []byte("---\ntitle: Zqindex Words\n---\n"), 0o644))
+	require.NoError(t, os.WriteFile(filepath.Join(w, "facts", "ok.md"), []byte("---\ntitle: Zqinside Phrase\n---\n"), 0o644))
+	cs, err := brain.DetectTunnels(b, "zqindex words and zqinside phrase")
+	require.NoError(t, err)
+	got := fmt.Sprintf("%+v", cs)
+	assert.Contains(t, got, "Zqinside Phrase", "positive control")
+	assert.NotContains(t, got, "Zqindex")
+}
diff --git a/ingestion/internal/brain/index.go b/ingestion/internal/brain/index.go
index 020b164..d700b74 100644
--- a/ingestion/internal/brain/index.go
+++ b/ingestion/internal/brain/index.go
@@ -116,7 +116,6 @@ func collectWingEntries(bfs *brainfs.Brain, wingRel string) ([]noteEntry, error)
 	return out, nil
 }
 
-
 // readTitleAndCreatedIn is readTitleAndCreated through the brain root,
 // regular files only (hyperguild#157).
 func readTitleAndCreatedIn(bfs *brainfs.Brain, rel, slug string) (string, string) {