feat(pipeline): skip extraction when the source has not changed (#105) (#126)

Co-authored-by: Mathias <mthbqv@gmail.com>

README.md

@@ -76,6 +76,46 @@ that prompted the question is answered by naming it here instead.
 Full reasoning, including the reversal trigger: brain
 `wiki/hyperguild/decisions/brain-mcp-stays-in-ingestion-fix-discoverability-by-name`.
 
+## Ingest revises, it does not overwrite
+
+Re-ingesting a source **merges into the page already on disk** rather than
+replacing it. Previously the write was unconditional, so a second ingest of the
+same source discarded everything accumulated since — including hand-written
+sections.
+
+The merge is deliberately asymmetric in the existing page's favour:
+
+| On the page | In the fresh extraction | Result |
+|---|---|---|
+| a section | the same section | **the on-disk version wins** |
+| — | a new section | added |
+| a bullet list (`Sources`, `Key Claims`, …) | more bullets | unioned, no duplicates |
+| an append section (`Open Questions`, `Updates`, …) | more lines | only genuinely new lines appended |
+| frontmatter | frontmatter | **the on-disk frontmatter wins** |
+
+So an extraction can add to a note but never silently rewrite what a human put
+there, which is what makes it safe to run on every ingest rather than behind a
+review gate.
+
+Re-ingesting unchanged content is **byte-identical** — no diff, so brain-sync
+does not commit noise that hides real edits.
+
+Two fields are **generator-owned** and do get refreshed on a revise:
+`last_updated` and `source_hash`. Everything else on disk wins. The boundary is
+an explicit allowlist, so a field nobody has thought about stays human-owned.
+
+## Re-ingesting an unchanged source is skipped
+
+Ingest stores `source_hash` — sha256 of the ingested **body**, frontmatter
+excluded — on the source page. A later ingest of the same source compares it
+first and skips extraction entirely when it matches, reporting the skip rather
+than doing it silently.
+
+Body-only is deliberate: a re-crawl that stamps a new fetch date has not changed
+the source, and treating that as drift would re-extract the corpus every time a
+crawler ran. A missing or unreadable hash always means "extract" — a missed skip
+costs one extraction, a wrong skip loses an update.
+
 ## Phase 1 tools (available now)
 
 | Tool | What it does |

ingestion/internal/api/update.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"github.com/mathiasbq/hyperguild/ingestion/internal/brain"
+	"github.com/mathiasbq/hyperguild/ingestion/internal/claim"
 )
 
 // ContentHash returns the lowercase hex sha256 of b. It is the note's
@@ -98,14 +99,47 @@ func UpdateNote(brainDir string, opts UpdateNoteOptions) (relPath, contentHash,
 	}
 	priorHash = ContentHash(prior)
 
+	// A caller may lead opts.Content with its own frontmatter fence to set or
+	// change fields on supersede (e.g. the claim envelope). Split it off
+	// before it reaches the body — left un-split, it would render as a
+	// second, inert `---`-fenced block of literal text rather than taking
+	// effect, and any claim-envelope fields inside it would reach disk
+	// unvalidated (hyperguild#111: the same rule that guards note birth in
+	// writeHallNote must guard a change to the same fields).
+	contentFM, contentBody := parseFrontmatter(opts.Content)
+
 	fm, _ := parseFrontmatter(string(prior))
+	for _, l := range contentFM.lines {
+		if l.key != "" {
+			fm.set(l.key, l.value)
+		}
+	}
 	fm.set("updated_at", time.Now().UTC().Format(time.RFC3339))
 	fm.set("supersedes", priorHash)
 	if opts.Reason != "" {
 		fm.set("supersede_reason", opts.Reason)
 	}
 
-	out := []byte(fm.render() + opts.Content)
+	// Validate the envelope AFTER the merge, against the full field set that
+	// is about to reach disk — not just the caller's fragment. Validating the
+	// fragment alone would miss a caller that supersedes claim_provenance to
+	// empty while half_life/applies survive untouched from the prior note:
+	// each side looks individually fine, but the merged result is an
+	// unprovenanced envelope, which is the exact laundering this check
+	// exists to catch. (Caught in review before merge, not filed after —
+	// worth being honest about in the history: this second pass was the
+	// actual fix; the first one validated the wrong document.)
+	envelope := make(map[string]string, len(fm.lines))
+	for _, l := range fm.lines {
+		if l.key != "" {
+			envelope[l.key] = l.value
+		}
+	}
+	if err := claim.ValidateEnvelope(envelope); err != nil {
+		return "", "", "", fmt.Errorf("claim envelope: %w", err)
+	}
+
+	out := []byte(fm.render() + contentBody)
 	if err := os.WriteFile(abs, out, 0o644); err != nil {
 		return "", "", "", fmt.Errorf("write: %w", err)
 	}

ingestion/internal/api/update_test.go

@@ -52,6 +52,114 @@ func TestUpdateNoteSupersedesAndStamps(t *testing.T) {
 	assert.Contains(t, s, "supersede_reason: facts changed")
 }
 
+func TestUpdateNoteRejectsInvalidEnvelopeAndWritesNothing(t *testing.T) {
+	// hyperguild#111: WriteNote validates the claim envelope before create;
+	// UpdateNote didn't before supersede, so the same rule must hold on
+	// change as on birth, fail-closed, nothing written on rejection.
+	brainDir := t.TempDir()
+	original := "---\nwing: jepa-fx\nhall: facts\ncreated_at: 2026-01-01T00:00:00Z\n---\n# Old\n\nold body\n"
+	rel := seedNote(t, brainDir, "wiki/jepa-fx/facts/val-vol.md", original)
+
+	_, _, _, err := UpdateNote(brainDir, UpdateNoteOptions{
+		Path:    rel,
+		Content: "---\nhalf_life: forever\n---\n# New\n\nnew body\n",
+	})
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "claim envelope")
+
+	got, err := os.ReadFile(filepath.Join(brainDir, filepath.FromSlash(rel)))
+	require.NoError(t, err)
+	assert.Equal(t, original, string(got), "rejected update must leave the note byte-identical")
+}
+
+func TestUpdateNoteRejectsAppliesWithoutProvenance(t *testing.T) {
+	brainDir := t.TempDir()
+	original := "---\nwing: jepa-fx\nhall: facts\n---\nold\n"
+	rel := seedNote(t, brainDir, "wiki/jepa-fx/facts/val-vol.md", original)
+
+	_, _, _, err := UpdateNote(brainDir, UpdateNoteOptions{
+		Path:    rel,
+		Content: "---\napplies: universal\n---\nnew\n",
+	})
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "claim envelope")
+
+	got, err := os.ReadFile(filepath.Join(brainDir, filepath.FromSlash(rel)))
+	require.NoError(t, err)
+	assert.Equal(t, original, string(got))
+}
+
+func TestUpdateNoteAcceptsValidEnvelopeAndMergesIntoFrontmatter(t *testing.T) {
+	brainDir := t.TempDir()
+	rel := seedNote(t, brainDir, "wiki/jepa-fx/facts/val-vol.md",
+		"---\nwing: jepa-fx\nhall: facts\ncreated_at: 2026-01-01T00:00:00Z\n---\nold\n")
+
+	_, _, _, err := UpdateNote(brainDir, UpdateNoteOptions{
+		Path:    rel,
+		Content: "---\nhalf_life: durable\napplies: universal\nclaim_provenance: asserted\n---\nnew body\n",
+	})
+	require.NoError(t, err)
+
+	got, err := os.ReadFile(filepath.Join(brainDir, filepath.FromSlash(rel)))
+	require.NoError(t, err)
+	s := string(got)
+	assert.Contains(t, s, "half_life: durable")
+	assert.Contains(t, s, "applies: universal")
+	assert.Contains(t, s, "claim_provenance: asserted")
+	assert.Contains(t, s, "wing: jepa-fx", "prior fields survive")
+	assert.Contains(t, s, "new body")
+	assert.Equal(t, 2, strings.Count(s, "---\n"),
+		"exactly one open+close fence pair — the caller's own fence must not leak in as a second, inert block")
+}
+
+func TestUpdateNoteRejectsClearingProvenanceWhileEnvelopeSurvives(t *testing.T) {
+	// Found in review, not written speculatively: validating only the
+	// caller's fragment (rather than the merged result) let a caller blank
+	// out claim_provenance alone while half_life/applies survived from the
+	// prior note untouched — each side looks fine on its own, the merged
+	// envelope on disk is the unprovenanced one the whole check exists to
+	// catch.
+	brainDir := t.TempDir()
+	original := "---\nwing: jepa-fx\nhall: facts\nhalf_life: durable\napplies: universal\nclaim_provenance: asserted\n---\nold\n"
+	rel := seedNote(t, brainDir, "wiki/jepa-fx/facts/val-vol.md", original)
+
+	_, _, _, err := UpdateNote(brainDir, UpdateNoteOptions{
+		Path:    rel,
+		Content: "---\nclaim_provenance: \n---\nnew body\n",
+	})
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "claim envelope")
+
+	got, err := os.ReadFile(filepath.Join(brainDir, filepath.FromSlash(rel)))
+	require.NoError(t, err)
+	assert.Equal(t, original, string(got), "rejected update must leave the note byte-identical")
+}
+
+func TestUpdateNoteWithoutEnvelopeFieldsIsUnchangedFromToday(t *testing.T) {
+	// Regression pin: plain fence-less content (the common case) must behave
+	// exactly as it did before the envelope-merge fix.
+	brainDir := t.TempDir()
+	rel := seedNote(t, brainDir, "wiki/jepa-fx/facts/val-vol.md",
+		"---\nwing: jepa-fx\nhall: facts\ncreated_at: 2026-01-01T00:00:00Z\ncustom: keep-me\n---\n# Old\n\nold body\n")
+
+	relPath, hash, priorHash, err := UpdateNote(brainDir, UpdateNoteOptions{
+		Path:    rel,
+		Content: "# New\n\nnew body\n",
+		Reason:  "facts changed",
+	})
+	require.NoError(t, err)
+	assert.Equal(t, rel, relPath)
+	assert.NotEmpty(t, hash)
+	assert.NotEqual(t, hash, priorHash)
+
+	got, err := os.ReadFile(filepath.Join(brainDir, filepath.FromSlash(rel)))
+	require.NoError(t, err)
+	s := string(got)
+	assert.Contains(t, s, "# New")
+	assert.Contains(t, s, "custom: keep-me")
+	assert.Contains(t, s, "supersedes: "+priorHash)
+}
+
 func TestUpdateNoteResolvesByWingHallSlug(t *testing.T) {
 	brainDir := t.TempDir()
 	seedNote(t, brainDir, "wiki/jepa-fx/facts/val-vol.md",

ingestion/internal/mcp/tools_notes.go

@@ -3,6 +3,7 @@ package mcp
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"log/slog"
 	"strings"
@@ -180,6 +181,13 @@ func (s *Server) editWithScope(args json.RawMessage, scope notes.Scope) (notes.R
 	}
 	res, err := notes.Edit(s.brainDir, a.Path, a.OldStr, a.NewStr, scope)
 	if err != nil {
+		if errors.Is(err, notes.ErrDegenerate) && a.OldStr == "" {
+			// hyperguild#115: "old_str is empty" alone doesn't say whether the
+			// caller sent it empty or a hop between the caller and here lost
+			// it. Naming the raw argument byte count makes that distinguishable
+			// without a second investigation.
+			return notes.Result{}, nil, fmt.Errorf("%w (raw arguments were %d bytes)", err, len(args))
+		}
 		return notes.Result{}, nil, err
 	}
 

ingestion/internal/mcp/tools_notes_test.go

@@ -70,6 +70,29 @@ func TestBrainReadAndEdit_RoundTripThroughJSONRPC(t *testing.T) {
 		"only the matched bytes may change")
 }
 
+func TestBrainEdit_EmptyOldStrErrorNamesRawArgumentBytes(t *testing.T) {
+	// hyperguild#115: a session reported "old_str is empty" with an old_str
+	// that, on their end, was never empty. The server-side path was
+	// unreachable to reproduce (verified separately: a fresh brain_edit call
+	// with real content round-trips cleanly), which points at something
+	// between a specific client and this call losing the field. The fix this
+	// issue actually asked for isn't a behavior change — old_str=="" must
+	// still refuse — it's that the refusal should say how many raw argument
+	// bytes it received, so "client sent empty" is distinguishable from
+	// "server received empty after some hop lost it" without a second
+	// session's worth of guessing.
+	dir := newBrainRepo(t)
+	srv := mcp.NewServer(dir, nil, nil, nil)
+
+	resp := call(t, srv, "brain_edit", map[string]any{
+		"path": "wiki/homelab/facts/n.md", "old_str": "", "new_str": "BETA",
+	})
+	errMsg, ok := resp["error"].(map[string]any)["message"].(string)
+	require.True(t, ok, "%v", resp)
+	assert.Contains(t, errMsg, "old_str is empty")
+	assert.Contains(t, errMsg, "raw arguments were", "%v", errMsg)
+}
+
 func TestBrainEdit_RefusesGovernanceFilesFromTheModelFacingTool(t *testing.T) {
 	dir := newBrainRepo(t)
 	srv := mcp.NewServer(dir, nil, nil, nil)

ingestion/internal/pipeline/build.go

@@ -76,6 +76,9 @@ func buildFrontmatter(rp RawPage, date string) string {
 		}
 		fmt.Fprintf(&sb, "date_ingested: %s\n", date)
 		fmt.Fprintf(&sb, "last_updated: %s\n", date)
+		if rp.SourceHash != "" {
+			fmt.Fprintf(&sb, "source_hash: %s\n", rp.SourceHash)
+		}
 		if rp.Source != "" {
 			fmt.Fprintf(&sb, "source: %s\n", yamlScalar(rp.Source))
 		}

ingestion/internal/pipeline/parse.go

@@ -20,6 +20,10 @@ type RawPage struct {
 	// ingested content's own frontmatter (see parseContentFrontmatter) — never
 	// set by the LLM. json:"-" keeps them immune to same-named keys the LLM
 	// might emit. Only meaningful for Type == "source".
+	// SourceHash is sha256 of the ingested BODY (frontmatter excluded), stamped
+	// so the next ingest of the same source can tell "unchanged" from "edited"
+	// without re-running extraction (#105).
+	SourceHash string `json:"-"`
 	Source     string `json:"-"`
 	Author     string `json:"-"`
 	Published  string `json:"-"`
@@ -112,6 +116,11 @@ type sourceMeta struct {
 	Source    string
 	Author    string
 	Published string
+	// BodyHash is sha256 of the content with any leading frontmatter removed.
+	// Body-only on purpose: a re-crawl that stamps a new fetch date has not
+	// changed the source, and treating that as drift would re-extract the
+	// whole corpus every time a crawler ran (#105).
+	BodyHash string
 }
 
 // parseContentFrontmatter extracts source/author/published from a leading
@@ -154,6 +163,7 @@ func applySourceMeta(pages []RawPage, meta sourceMeta) {
 		if pages[i].Type != "source" {
 			continue
 		}
+		pages[i].SourceHash = meta.BodyHash
 		pages[i].Source = meta.Source
 		pages[i].Author = meta.Author
 		pages[i].Published = meta.Published

ingestion/internal/pipeline/pipeline.go

@@ -3,6 +3,8 @@ package pipeline
 
 import (
 	"context"
+	"crypto/sha256"
+	"encoding/hex"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -26,6 +28,11 @@ type Config struct {
 type Result struct {
 	Pages    []string // relative paths written (or would-be written in dry-run)
 	Warnings []string
+	// Skipped reports that the source was byte-identical to the last ingest,
+	// so no extraction ran and nothing was written. Reported rather than
+	// silent: a run that does nothing must say so, or "the pipeline is fine"
+	// and "the pipeline stopped working" look the same (#105, #107).
+	Skipped bool
 }
 
 // Run ingests content and writes structured wiki pages to brainDir/wiki/.
@@ -43,6 +50,18 @@ func Run(ctx context.Context, cfg Config, brainDir, content, source string, dryR
 
 	sourceSlug := wiki.Slug(source)
 	date := time.Now().UTC().Format("2006-01-02")
+
+	// Drift check BEFORE any extraction: an unchanged source costs a full LLM
+	// pass over every chunk to produce a result that merges to nothing (#105).
+	// The merge is already idempotent (#103), so this is cost and signal, not
+	// correctness — which is why it is safe for it to be an early return.
+	bodyHash := hashBody(content)
+	if !dryRun && bodyHash != "" && bodyHash == storedSourceHash(brainDir, sourceSlug) {
+		return Result{Skipped: true, Warnings: []string{
+			fmt.Sprintf("source %q unchanged since last ingest (hash %s) — extraction skipped", source, bodyHash[:12]),
+		}}, nil
+	}
+
 	chunks := Chunk(content, cfg.ChunkSize)
 
 	var allRaw []RawPage
@@ -59,7 +78,9 @@ func Run(ctx context.Context, cfg Config, brainDir, content, source string, dryR
 		allWarnings = append(allWarnings, warnings...)
 	}
 
-	applySourceMeta(allRaw, parseContentFrontmatter(content))
+	meta := parseContentFrontmatter(content)
+	meta.BodyHash = bodyHash
+	applySourceMeta(allRaw, meta)
 
 	return buildAndWrite(allRaw, sourceSlug, date, brainDir, source, inventory, allWarnings, dryRun)
 }
@@ -96,7 +117,11 @@ func buildAndWrite(rawPages []RawPage, sourceSlug, date, brainDir, source string
 			if err := os.MkdirAll(filepath.Dir(dest), 0o755); err != nil {
 				return Result{}, fmt.Errorf("mkdir for %s: %w", page.Path, err)
 			}
-			if err := os.WriteFile(dest, []byte(page.Content), 0o644); err != nil {
+			content, err := reviseOrCreate(dest, page)
+			if err != nil {
+				return Result{}, err
+			}
+			if err := os.WriteFile(dest, []byte(content), 0o644); err != nil {
 				return Result{}, fmt.Errorf("write %s: %w", page.Path, err)
 			}
 		}
@@ -115,6 +140,75 @@ func buildAndWrite(rawPages []RawPage, sourceSlug, date, brainDir, source string
 	return Result{Pages: written, Warnings: warnings}, nil
 }
 
+// hashBody returns sha256 of content with any leading frontmatter block
+// removed, or "" for empty content.
+//
+// Body-only on purpose: a re-crawl that stamps a new fetch date has not changed
+// the source, and treating that as drift would re-extract the corpus every time
+// a crawler ran (#105).
+func hashBody(content string) string {
+	body := content
+	if strings.HasPrefix(body, "---\n") {
+		if _, rest, found := strings.Cut(body[4:], "\n---"); found {
+			body = strings.TrimPrefix(rest, "\n")
+		}
+	}
+	if strings.TrimSpace(body) == "" {
+		return ""
+	}
+	sum := sha256.Sum256([]byte(body))
+	return hex.EncodeToString(sum[:])
+}
+
+// storedSourceHash reads source_hash from the source page a previous ingest
+// wrote, or "" when there is no such page or no such field.
+//
+// Absence always means "extract". That is the fail-safe direction: a missed
+// skip costs one extraction, while a wrong skip loses an update silently — and
+// silence is the failure mode this repo keeps paying for.
+func storedSourceHash(brainDir, sourceSlug string) string {
+	raw, err := os.ReadFile(filepath.Join(brainDir, "wiki", "sources", sourceSlug+".md"))
+	if err != nil {
+		return ""
+	}
+	for _, line := range strings.Split(string(raw), "\n") {
+		if key, value, found := strings.Cut(line, ":"); found && strings.TrimSpace(key) == "source_hash" {
+			return strings.TrimSpace(value)
+		}
+	}
+	return ""
+}
+
+// reviseOrCreate returns the bytes to write for one extracted page: merged into
+// whatever is already on disk, or the page as-is when the path is new.
+//
+// This is the compile half of compile-on-ingest. Before it, the write was an
+// unconditional os.WriteFile, so re-ingesting a source replaced its page
+// wholesale and discarded everything accumulated since — including human edits
+// (hyperguild#43: "re-ingest overwrites wholesale").
+//
+// The merge is deliberately asymmetric in the existing page's favour:
+// wiki.Merge keeps the on-disk frontmatter and the on-disk version of any
+// section both sides carry, adds sections only the extraction produced, and
+// unions bullet lists. So a freshly extracted page can add to a note but never
+// silently rewrite what a human put there — which is what makes it safe to run
+// this on every ingest rather than behind a review gate.
+//
+// Known limitation: because the on-disk frontmatter wins, `last_updated` keeps
+// its first-ingest date on a revised page. Left deliberately — the alternative
+// is this function editing frontmatter it does not own, and no lint reads that
+// field today.
+func reviseOrCreate(dest string, page wiki.Page) (string, error) {
+	existing, err := os.ReadFile(dest)
+	switch {
+	case os.IsNotExist(err):
+		return page.Content, nil
+	case err != nil:
+		return "", fmt.Errorf("read existing %s: %w", page.Path, err)
+	}
+	return wiki.Merge(wiki.Page{Path: page.Path, Content: string(existing)}, page).Content, nil
+}
+
 // mergeAll deduplicates pages by path, merging content from later occurrences.
 func mergeAll(pages []wiki.Page) []wiki.Page {
 	order := make([]string, 0, len(pages))

ingestion/internal/pipeline/pipeline_test.go

@@ -171,3 +171,125 @@ func mustJSON(v any) string {
 	}
 	return string(b)
 }
+
+// --- B1: compile-on-ingest — revise the existing page, never clobber it -----
+
+func TestRunRaw_MergesIntoAnExistingPageInsteadOfOverwritingIt(t *testing.T) {
+	// Before this, buildAndWrite did an unconditional os.WriteFile: re-ingesting
+	// a source replaced its page wholesale, discarding anything accumulated
+	// since — including human edits. hyperguild#43 recorded the symptom as
+	// "re-ingest overwrites wholesale".
+	dir := t.TempDir()
+	page := filepath.Join(dir, "wiki", "sources", "shape-up.md")
+	require.NoError(t, os.MkdirAll(filepath.Dir(page), 0o755))
+	require.NoError(t, os.WriteFile(page, []byte(`---
+title: 'Shape Up'
+---
+
+## Summary
+
+A book about shaping product work.
+
+## My Take
+
+Read this before the next planning cycle.
+`), 0o644))
+
+	_, err := RunRaw(dir, "shape-up", []RawPage{{
+		Title: "Shape Up", Type: "source", Subtype: "book", Domain: "product-strategy",
+		Content: "## Summary\n\nA book about shaping product work.\n\n## Key Claims\n\n- Appetite beats estimation.\n",
+	}}, false)
+	require.NoError(t, err)
+
+	got, err := os.ReadFile(page)
+	require.NoError(t, err)
+	s := string(got)
+
+	assert.Contains(t, s, "## My Take", "a section the extraction never saw must survive the merge")
+	assert.Contains(t, s, "Read this before the next planning cycle.")
+	assert.Contains(t, s, "Appetite beats estimation.", "newly extracted material must still land")
+}
+
+func TestRunRaw_ReIngestingUnchangedContentIsByteIdentical(t *testing.T) {
+	// Compile-on-ingest runs on every ingest, so "nothing changed" must produce
+	// no diff at all. Otherwise every re-ingest dirties the tree, brain-sync
+	// commits it, and the git history fills with noise that hides real edits.
+	dir := t.TempDir()
+	raw := []RawPage{{
+		Title: "Shape Up", Type: "source", Subtype: "book", Domain: "product-strategy",
+		Content: "## Summary\n\nA book about shaping product work.\n\n## Open Questions\n\n- Does appetite scale?\n",
+	}}
+
+	_, err := RunRaw(dir, "shape-up", raw, false)
+	require.NoError(t, err)
+	first, err := os.ReadFile(filepath.Join(dir, "wiki", "sources", "shape-up.md"))
+	require.NoError(t, err)
+
+	_, err = RunRaw(dir, "shape-up", raw, false)
+	require.NoError(t, err)
+	second, err := os.ReadFile(filepath.Join(dir, "wiki", "sources", "shape-up.md"))
+	require.NoError(t, err)
+
+	assert.Equal(t, string(first), string(second),
+		"re-ingesting unchanged content must leave the page byte-identical")
+}
+
+// --- #105: source drift — an unchanged re-ingest must not re-extract --------
+
+func TestRun_SkipsExtractionWhenTheSourceIsUnchanged(t *testing.T) {
+	// #103 made a re-ingest harmless (byte-identical merge). It is still not
+	// free: the full LLM extraction runs over every chunk to produce a result
+	// that merges to nothing. This is the cost half.
+	dir := t.TempDir()
+	var calls int
+	cfg := Config{Complete: func(_ context.Context, _, _ string) (string, error) {
+		calls++
+		return `[{"title":"Shape Up","type":"source","subtype":"book","domain":"product","content":"## Summary\n\nA book.\n"}]`, nil
+	}}
+
+	content := "---\nsource: https://example.com/shape-up\n---\n\nThe body of the article.\n"
+
+	first, err := Run(context.Background(), cfg, dir, content, "shape-up", false)
+	require.NoError(t, err)
+	require.Equal(t, 1, calls, "first ingest must extract")
+	assert.False(t, first.Skipped)
+
+	second, err := Run(context.Background(), cfg, dir, content, "shape-up", false)
+	require.NoError(t, err)
+	assert.Equal(t, 1, calls, "unchanged content must not be extracted again")
+	assert.True(t, second.Skipped, "the skip must be reported, not silent")
+}
+
+func TestRun_ReExtractsWhenTheSourceBodyChanged(t *testing.T) {
+	dir := t.TempDir()
+	var calls int
+	cfg := Config{Complete: func(_ context.Context, _, _ string) (string, error) {
+		calls++
+		return `[{"title":"Shape Up","type":"source","subtype":"book","domain":"product","content":"## Summary\n\nA book.\n"}]`, nil
+	}}
+
+	_, err := Run(context.Background(), cfg, dir, "---\nsource: x\n---\n\nversion one\n", "shape-up", false)
+	require.NoError(t, err)
+	_, err = Run(context.Background(), cfg, dir, "---\nsource: x\n---\n\nversion two — the source was edited\n", "shape-up", false)
+	require.NoError(t, err)
+
+	assert.Equal(t, 2, calls, "changed content must be re-extracted")
+}
+
+func TestRun_FrontmatterOnlyChangeIsNotDrift(t *testing.T) {
+	// The hash covers the body, so re-fetching a page whose metadata moved
+	// (a re-crawl stamping a new date) is not treated as the source changing.
+	dir := t.TempDir()
+	var calls int
+	cfg := Config{Complete: func(_ context.Context, _, _ string) (string, error) {
+		calls++
+		return `[{"title":"Shape Up","type":"source","subtype":"book","domain":"product","content":"## Summary\n\nA book.\n"}]`, nil
+	}}
+
+	_, err := Run(context.Background(), cfg, dir, "---\nsource: x\nfetched: monday\n---\n\nsame body\n", "shape-up", false)
+	require.NoError(t, err)
+	_, err = Run(context.Background(), cfg, dir, "---\nsource: x\nfetched: tuesday\n---\n\nsame body\n", "shape-up", false)
+	require.NoError(t, err)
+
+	assert.Equal(t, 1, calls, "only the body counts as the source")
+}

ingestion/internal/wiki/merge.go

@@ -3,6 +3,7 @@ package wiki
 
 import (
 	"fmt"
+	"sort"
 	"strings"
 )
 
@@ -29,12 +30,16 @@ type section struct {
 }
 
 // Merge combines two Page values with the same path.
-// Frontmatter is taken from a. Sections are merged by strategy:
-// bullet sections union unique lines, append sections concatenate,
-// all others keep a's version. Sections in b not present in a are appended.
+// Frontmatter is taken from a. The preamble (content before the first ##
+// heading) is taken from a — same "on-disk wins" default every unlisted
+// named section gets, kept as a separate field rather than a section with
+// an empty heading so it can never collide with one (see parseSections).
+// Sections are merged by strategy: bullet sections union unique lines,
+// append sections concatenate, all others keep a's version. Sections in b
+// not present in a are appended.
 func Merge(a, b Page) Page {
-	fmA, secsA := parseSections(a.Content)
-	_, secsB := parseSections(b.Content)
+	fmA, preambleA, secsA := parseSections(a.Content)
+	fmB, _, secsB := parseSections(b.Content)
 
 	idx := make(map[string]int, len(secsA))
 	for i, s := range secsA {
@@ -53,14 +58,168 @@ func Merge(a, b Page) Page {
 		case bulletSections[sB.heading]:
 			secsA[i].content = mergeBullets(sA.content, sB.content)
 		case appendSections[sB.heading]:
-			secsA[i].content = strings.TrimRight(sA.content, "\n") + "\n\n" + strings.TrimLeft(sB.content, "\n")
+			secsA[i].content = appendNew(sA.content, sB.content)
 		}
 	}
 
-	return Page{Path: a.Path, Content: rebuildContent(fmA, secsA)}
+	return Page{Path: a.Path, Content: rebuildContent(refreshOwned(fmA, fmB), preambleA, secsA)}
 }
 
-func parseSections(markdown string) (frontmatter string, sections []section) {
+// generatorOwned names the frontmatter fields the ingest pipeline may refresh
+// on a page it is revising. Everything else on disk wins.
+//
+// #103 made the on-disk frontmatter win wholesale, which is what stops a
+// regenerating writer from overwriting human-set metadata — a title someone
+// fixed, or the claim-property envelope (brain#21). The cost was that fields
+// the generator legitimately owns froze at their first-ingest values: when it
+// last ran, and what it last saw.
+//
+// An explicit allowlist rather than a carve-out: the ownership boundary is
+// nameable, and a field nobody has thought about stays human-owned by default,
+// which is the safe direction.
+var generatorOwned = map[string]bool{
+	"last_updated": true,
+	"source_hash":  true,
+}
+
+// fmLine is one line of a frontmatter block: a parsed key/value pair, or a
+// raw line (blank, comment, or anything else that isn't a simple "key:
+// value") kept verbatim. Same shape as api.frontmatter's fmLine — this
+// package doesn't import that one (it's unexported there, and a's/b's
+// frontmatter here always arrives as a string, not a parsed struct), so the
+// small, already-proven set()-appends-if-absent behavior is reproduced
+// locally rather than string-index surgery reinvented per call site.
+type fmLine struct {
+	key, value, raw string
+}
+
+// parseFrontmatterBlock parses a "---\n...\n---\n" fenced block (the shape
+// parseSections produces) into an ordered line list. A block with no
+// opening/closing fence — including the empty string, a page with no
+// frontmatter at all — returns nil, ok=false: there is nothing to update in
+// place, only something to potentially create.
+func parseFrontmatterBlock(block string) (lines []fmLine, ok bool) {
+	if !strings.HasPrefix(block, "---\n") {
+		return nil, false
+	}
+	rest := block[len("---\n"):]
+	end := strings.Index(rest, "\n---\n")
+	if end < 0 {
+		return nil, false
+	}
+	for _, line := range strings.Split(rest[:end], "\n") {
+		// An indented line is a continuation (a YAML block-list item, a
+		// wrapped value) never a top-level key, regardless of whether it
+		// happens to contain a colon — "  - 'Chapter 3: The Reckoning'"
+		// is not a key named "- 'Chapter 3". Checked before Cut so a
+		// colon inside one never reaches the key/value path at all.
+		if line != "" && (line[0] == ' ' || line[0] == '\t') {
+			lines = append(lines, fmLine{raw: line})
+			continue
+		}
+		key, val, found := strings.Cut(line, ":")
+		key = strings.TrimSpace(key)
+		if !found || key == "" || strings.HasPrefix(strings.TrimSpace(line), "#") {
+			lines = append(lines, fmLine{raw: line})
+			continue
+		}
+		lines = append(lines, fmLine{key: key, value: strings.TrimSpace(val)})
+	}
+	return lines, true
+}
+
+// setLine updates key's value in place if lines already has it, or appends
+// a new entry if it doesn't — the one behavior the original refreshOwned
+// got wrong (PR #126 review, round 2: it only ever updated in place).
+func setLine(lines []fmLine, key, value string) []fmLine {
+	for i := range lines {
+		if lines[i].key == key {
+			lines[i].value = value
+			return lines
+		}
+	}
+	return append(lines, fmLine{key: key, value: value})
+}
+
+func renderFrontmatterBlock(lines []fmLine) string {
+	if len(lines) == 0 {
+		return ""
+	}
+	var sb strings.Builder
+	sb.WriteString("---\n")
+	for _, l := range lines {
+		switch {
+		case l.key == "":
+			sb.WriteString(l.raw)
+		case l.value == "":
+			// A key with nothing after the colon (the YAML block-list shape:
+			// "aliases:" followed by indented "- item" lines on their own
+			// raw lines) must stay bare — "key: " with a trailing space
+			// is a different, if invisible, byte sequence, and this file's
+			// whole purpose is byte-stability across an unrelated merge.
+			sb.WriteString(l.key)
+			sb.WriteByte(':')
+		default:
+			sb.WriteString(l.key)
+			sb.WriteString(": ")
+			sb.WriteString(l.value)
+		}
+		sb.WriteByte('\n')
+	}
+	sb.WriteString("---\n")
+	return sb.String()
+}
+
+// refreshOwned returns a's frontmatter with the generator-owned fields taken
+// from b where b supplies them. Fields absent from b keep a's value, so a
+// generator that stops emitting a field cannot blank it.
+//
+// A field b supplies that a doesn't have yet — every page ingested before
+// this mechanism existed has no source_hash line at all — is appended, not
+// dropped (round 1 of review: dropping it silently meant source_hash never
+// populated for the pre-existing corpus). If a has no frontmatter fence at
+// all, one is created to hold the new fields rather than splicing raw
+// "key: value" text into the body (round 2: that corrupted the page and the
+// fields would duplicate on every subsequent merge, since unfenced text
+// isn't recognized as frontmatter by parseSections on the next pass).
+func refreshOwned(a, b string) string {
+	bLines, _ := parseFrontmatterBlock(b)
+	bVals := make(map[string]string)
+	for _, l := range bLines {
+		if l.key != "" && generatorOwned[l.key] {
+			bVals[l.key] = l.value
+		}
+	}
+	if len(bVals) == 0 {
+		return a
+	}
+
+	aLines, _ := parseFrontmatterBlock(a) // ok==false (no fence) -> aLines nil, same as "start fresh"
+
+	// Sorted for a deterministic, byte-stable result when more than one
+	// field is appended in the same call — map iteration order isn't.
+	keys := make([]string, 0, len(bVals))
+	for k := range bVals {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	for _, k := range keys {
+		aLines = setLine(aLines, k, bVals[k])
+	}
+	return renderFrontmatterBlock(aLines)
+}
+
+// parseSections splits markdown into its frontmatter, its preamble (content
+// before the first `## ` heading), and its `## `-headed sections.
+//
+// The preamble is returned separately rather than as a section with an
+// empty heading — a section keyed by heading=="" would collide with a
+// literal degenerate `## ` (marker, no title text; strings.TrimPrefix also
+// yields ""), which is a distinct, addressable section a page can genuinely
+// have, not the same thing as "no heading yet." Two entries sharing one key
+// in Merge's idx map means one of them silently loses lookup visibility —
+// found in review as real, reproducible data loss, not a hypothetical.
+func parseSections(markdown string) (frontmatter, preamble string, sections []section) {
 	lines := strings.Split(markdown, "\n")
 	i := 0
 
@@ -78,6 +237,22 @@ func parseSections(markdown string) (frontmatter string, sections []section) {
 		frontmatter = fmt.Sprintf("---\n%s\n---\n", strings.Join(fmLines, "\n"))
 	}
 
+	// Everything before the first `## ` heading — an intro paragraph, or, if
+	// the page has no headings at all, the entire body — is ordinary content,
+	// not something this parser is entitled to drop (hyperguild#103 review:
+	// dropping it meant Merge, one caller up, would silently replace the
+	// whole on-disk body with the fresh extraction whenever a page didn't
+	// follow the ## convention — exactly the class of bug this file exists
+	// to prevent).
+	var preambleLines []string
+	for ; i < len(lines); i++ {
+		if strings.HasPrefix(lines[i], "## ") {
+			break
+		}
+		preambleLines = append(preambleLines, lines[i])
+	}
+	preamble = strings.Join(preambleLines, "\n")
+
 	var cur *section
 	for ; i < len(lines); i++ {
 		line := lines[i]
@@ -96,24 +271,85 @@ func parseSections(markdown string) (frontmatter string, sections []section) {
 	return
 }
 
-func rebuildContent(frontmatter string, sections []section) string {
+// rebuildContent serialises sections back into a page.
+//
+// Each section body is normalised to exactly one trailing newline and no
+// leading blank line. Without that, a section keeps whatever blank lines it was
+// parsed with and this function adds its own, so every merge pass grows the page
+// by a blank line — invisible in a diff viewer, fatal to byte-stability. Compile-on-ingest
+// merges on every run, so "merging changes nothing when nothing changed" has to
+// hold at the byte level, not just the content level.
+func rebuildContent(frontmatter, preamble string, sections []section) string {
 	var sb strings.Builder
 	sb.WriteString(frontmatter)
+	if body := strings.Trim(preamble, "\n"); body != "" {
+		fmt.Fprintf(&sb, "\n%s\n", body)
+	}
 	for _, sec := range sections {
-		fmt.Fprintf(&sb, "\n## %s\n\n%s", sec.heading, sec.content)
+		body := strings.Trim(sec.content, "\n")
+		fmt.Fprintf(&sb, "\n## %s\n\n%s\n", sec.heading, body)
 	}
 	return sb.String()
 }
 
+// canonicalLine collapses a line to its comparison key: internal whitespace
+// runs (a re-extraction's bullet spacing, tabs vs spaces, trailing spaces)
+// must not make the same logical line look new. strings.Fields already
+// trims and splits on any whitespace run, so joining it back with single
+// spaces is exactly "same words, same order, whitespace-insensitive."
+func canonicalLine(line string) string {
+	return strings.Join(strings.Fields(line), " ")
+}
+
+// appendNew concatenates the lines of b that a does not already carry.
+//
+// Append sections used to concatenate wholesale, which is correct exactly once.
+// Compile-on-ingest merges a freshly extracted page into the one already on
+// disk, so an unchanged source re-ingested would grow "Open Questions" and
+// "Updates" on every run until the page is unreadable — and the drift guard
+// that would otherwise catch it (hashing the source body) does not exist yet,
+// so idempotency has to hold here rather than upstream.
+//
+// Line-level rather than block-level: the common case is a re-ingest carrying
+// one genuinely new line alongside several it already has. A block-level
+// "skip if identical" would duplicate the old lines every time that happened.
+//
+// The cost is that a line repeated verbatim on purpose collapses to one. For
+// these sections — questions, updates, evolving notes — a repeat is noise
+// rather than signal, and the failure is conservative: the page stops growing
+// instead of growing wrongly.
+func appendNew(a, b string) string {
+	seen := make(map[string]bool)
+	for _, line := range strings.Split(a, "\n") {
+		if c := canonicalLine(line); c != "" {
+			seen[c] = true
+		}
+	}
+
+	var add []string
+	for _, line := range strings.Split(b, "\n") {
+		c := canonicalLine(line)
+		if c == "" || seen[c] {
+			continue
+		}
+		seen[c] = true
+		add = append(add, line)
+	}
+	if len(add) == 0 {
+		return a // nothing new — leave the section byte-identical
+	}
+	return strings.TrimRight(a, "\n") + "\n\n" + strings.Join(add, "\n") + "\n"
+}
+
 func mergeBullets(a, b string) string {
 	seen := make(map[string]bool)
 	var lines []string
 	for _, line := range strings.Split(a+b, "\n") {
-		trimmed := strings.TrimSpace(line)
-		if trimmed == "" || seen[trimmed] {
+		c := canonicalLine(line)
+		if c == "" || seen[c] {
 			continue
 		}
-		seen[trimmed] = true
+		seen[c] = true
 		lines = append(lines, line)
 	}
 	return strings.Join(lines, "\n") + "\n"

ingestion/internal/wiki/merge_test.go

@@ -53,3 +53,282 @@ func TestMerge_KeepsFrontmatterFromA(t *testing.T) {
 	assert.Contains(t, got.Content, "title: A")
 	assert.NotContains(t, got.Content, "title: B")
 }
+
+// --- hyperguild#103 review: a page with content outside any `## ` section ---
+// must never lose that content on merge. parseSections used to only capture
+// text between `## ` headings — anything before the first heading (a common,
+// ordinary shape for a hand-written note: an intro paragraph before the first
+// section) or, worse, an entire page with no `## ` headings at all (a legacy
+// note, a stub, any hand-edit that doesn't follow the section convention)
+// vanished silently. Merge would then fill the page entirely from the fresh
+// extraction — the opposite of "never silently rewrite what a human put
+// there," the guarantee this whole file exists to provide.
+
+func TestMerge_PreservesOnDiskContentWithNoSectionHeadings(t *testing.T) {
+	a := Page{Path: "wiki/x.md", Content: "---\ntitle: X\n---\n\nJust some free text a human wrote. No section headings at all.\n"}
+	b := Page{Path: "wiki/x.md", Content: "---\ntitle: X\n---\n\n## Definition\n\nFresh extraction's take.\n"}
+
+	got := Merge(a, b)
+	assert.Contains(t, got.Content, "Just some free text a human wrote",
+		"on-disk content with no ## headings must survive the merge, not be replaced wholesale by the fresh extraction")
+}
+
+func TestMerge_DegenerateEmptyHeadingDoesNotCollideWithPreamble(t *testing.T) {
+	// Second review pass on #103: representing the preamble as a section with
+	// heading=="" collides with a literal `## ` (marker, no title text) —
+	// strings.TrimPrefix("## ", "## ") is also "". `a` has only a preamble
+	// (no degenerate heading of its own); `b` introduces a genuinely new
+	// degenerate `## ` section. Because both key to "", Merge's idx thinks
+	// b's section "already exists" in a (it's really just a's unrelated
+	// preamble) and never adds it — b's section vanishes from the output
+	// entirely, not merged, not kept, not appended.
+	a := Page{Path: "p.md", Content: "---\ntitle: X\n---\n\nAn intro paragraph.\n\n## Definition\n\nA thing.\n"}
+	b := Page{Path: "p.md", Content: "---\ntitle: X\n---\n\n## \n\nA genuinely new degenerate section's body.\n\n## Definition\n\nA thing.\n"}
+
+	got := Merge(a, b)
+	assert.Contains(t, got.Content, "An intro paragraph.", "a's own preamble must survive")
+	assert.Contains(t, got.Content, "A genuinely new degenerate section's body.",
+		"b's degenerate section is new content, not a collision with a's unrelated preamble — it must not be silently dropped")
+}
+
+func TestMerge_PreservesPreambleBeforeFirstHeading(t *testing.T) {
+	a := Page{Path: "wiki/x.md", Content: "---\ntitle: X\n---\n\nAn intro paragraph before the first heading.\n\n## Definition\n\nA thing.\n"}
+	b := Page{Path: "wiki/x.md", Content: "---\ntitle: X\n---\n\n## Definition\n\nA thing.\n"}
+
+	got := Merge(a, b)
+	assert.Contains(t, got.Content, "An intro paragraph before the first heading",
+		"text before the first ## heading is ordinary page content, not something the parser is entitled to drop")
+}
+
+// --- hyperguild#103 review: dedup must be whitespace-insensitive -----------
+// Page content is produced by an LLM per run, so byte-identical re-extraction
+// of "the same" logical line is not guaranteed — different bullet spacing or
+// trailing whitespace on an otherwise-identical line must still dedup, or
+// idempotency only holds when the extractor happens to reproduce whitespace
+// exactly, which is not a real guarantee.
+
+func TestMerge_AppendSectionDedupsAcrossWhitespaceVariants(t *testing.T) {
+	a := Page{Path: "p.md", Content: "---\ntitle: X\n---\n\n## Open Questions\n\n- Does this converge?\n"}
+	b := Page{Path: "p.md", Content: "---\ntitle: X\n---\n\n## Open Questions\n\n-   Does this converge?  \n"}
+
+	got := Merge(a, b)
+	assert.Equal(t, 1, strings.Count(got.Content, "Does this converge?"),
+		"same logical line with different whitespace must dedup, not duplicate")
+}
+
+func TestMerge_BulletSectionDedupsAcrossWhitespaceVariants(t *testing.T) {
+	a := Page{Path: "p.md", Content: "---\ntitle: X\n---\n\n## Related Concepts\n\n- [[bar|Bar]]\n"}
+	b := Page{Path: "p.md", Content: "---\ntitle: X\n---\n\n## Related Concepts\n\n-  [[bar|Bar]]\n"}
+
+	got := Merge(a, b)
+	assert.Equal(t, 1, strings.Count(got.Content, "[[bar|Bar]]"),
+		"same logical bullet with different whitespace must dedup, not duplicate")
+}
+
+// --- brain#21/B1: merging must be safe to run again -------------------------
+
+func TestMerge_AppendSectionDoesNotDuplicateContentAlreadyPresent(t *testing.T) {
+	// Compile-on-ingest merges a freshly extracted page into the one already
+	// on disk. Bullet sections union, so they are naturally idempotent — but
+	// append sections concatenate, so re-ingesting an unchanged source would
+	// grow "Open Questions" on every run until the page is unreadable.
+	page := Page{Path: "wiki/sources/x.md", Content: `---
+title: X
+---
+
+## Open Questions
+
+- Does this converge?
+`}
+
+	once := Merge(page, page)
+	twice := Merge(once, page)
+
+	assert.Equal(t, 1, strings.Count(once.Content, "Does this converge?"),
+		"merging a page with itself must not duplicate an append section")
+	assert.Equal(t, once.Content, twice.Content,
+		"merge must be idempotent — a third pass may not keep growing the page")
+}
+
+func TestMerge_AppendSectionStillAccumulatesGenuinelyNewContent(t *testing.T) {
+	// The dedup must not turn append sections into keep-a-only sections:
+	// new material is exactly what compile-on-ingest exists to add.
+	existing := Page{Path: "wiki/sources/x.md", Content: `---
+title: X
+---
+
+## Open Questions
+
+- Does this converge?
+`}
+	fresh := Page{Path: "wiki/sources/x.md", Content: `---
+title: X
+---
+
+## Open Questions
+
+- What happens under load?
+`}
+
+	got := Merge(existing, fresh).Content
+	assert.Contains(t, got, "Does this converge?", "existing question must survive")
+	assert.Contains(t, got, "What happens under load?", "new question must be added")
+}
+
+func TestMerge_GeneratorOwnedFrontmatterFieldsAreRefreshed(t *testing.T) {
+	// #103 made on-disk frontmatter win wholesale, which is what protects
+	// human-set fields from a regenerating writer. The cost was that fields the
+	// generator legitimately owns — when it last ran, what it last saw — froze
+	// at their first-ingest values. An explicit owned-set is the boundary:
+	// named fields the generator may refresh, everything else human-owned.
+	existing := Page{Path: "wiki/sources/x.md", Content: `---
+title: 'X'
+last_updated: 2026-01-01
+source_hash: aaaa
+half_life: durable
+claim_provenance: asserted
+---
+
+## Summary
+
+Original.
+`}
+	fresh := Page{Path: "wiki/sources/x.md", Content: `---
+title: 'Renamed by the model'
+last_updated: 2026-08-22
+source_hash: bbbb
+---
+
+## Summary
+
+Rewritten by the model.
+`}
+
+	got := Merge(existing, fresh).Content
+
+	assert.Contains(t, got, "last_updated: 2026-08-22", "generator owns last_updated")
+	assert.Contains(t, got, "source_hash: bbbb", "generator owns source_hash")
+	assert.Contains(t, got, "title: 'X'", "a human-set title must survive regeneration")
+	assert.Contains(t, got, "half_life: durable", "the claim envelope must survive regeneration")
+	assert.Contains(t, got, "claim_provenance: asserted")
+	assert.Contains(t, got, "Original.", "an existing section still wins over the model's rewrite")
+	assert.NotContains(t, got, "Renamed by the model")
+}
+
+func TestMerge_GeneratorOwnedFieldsAreAppendedWhenAPageNeverHadThemBefore(t *testing.T) {
+	// Found in review of PR #126: refreshOwned only replaced a generator-owned
+	// line that already existed in a's frontmatter — it never appended one a
+	// didn't have. Every page ingested before this feature shipped has no
+	// source_hash line at all, so on its first re-ingest after deploy, the
+	// fresh hash was silently dropped and the skip-on-unchanged feature this
+	// PR exists to build would never engage for the entire pre-existing
+	// corpus, permanently, with nothing telling anyone.
+	existing := Page{Path: "wiki/sources/x.md", Content: `---
+title: 'X'
+---
+
+## Summary
+
+Original.
+`}
+	fresh := Page{Path: "wiki/sources/x.md", Content: `---
+title: 'Renamed by the model'
+last_updated: 2026-08-22
+source_hash: bbbb
+---
+
+## Summary
+
+Rewritten by the model.
+`}
+
+	got := Merge(existing, fresh).Content
+
+	// Exact frontmatter block, not Contains: the second review round found
+	// that a substring check doesn't prove the fields landed inside a valid
+	// fence, in the right order, or that the fence itself wasn't corrupted —
+	// two independent mutations (closeIdx targeting the wrong fence, reversed
+	// sort) both survived a Contains-only version of this test.
+	want := "---\ntitle: 'X'\nlast_updated: 2026-08-22\nsource_hash: bbbb\n---\n\n## Summary\n\nOriginal.\n"
+	assert.Equal(t, want, got)
+}
+
+func TestMerge_GeneratorOwnedFieldsCreateAFrontmatterBlockWhenThePageHadNoneAtAll(t *testing.T) {
+	// Second review round on PR #126: when a has no frontmatter fence at all,
+	// the append fallback spliced raw, unfenced "key: value" lines straight
+	// into the body -- worse than the original bug, because the next
+	// parseSections call wouldn't recognize them as frontmatter (they don't
+	// start with `---`), so they'd be absorbed as ordinary preamble text and
+	// re-duplicate on every subsequent merge instead of updating in place.
+	existing := Page{Path: "wiki/sources/x.md", Content: "## Summary\n\nOriginal.\n"}
+	fresh := Page{Path: "wiki/sources/x.md", Content: `---
+last_updated: 2026-08-22
+source_hash: bbbb
+---
+
+## Summary
+
+Rewritten by the model.
+`}
+
+	got := Merge(existing, fresh).Content
+
+	want := "---\nlast_updated: 2026-08-22\nsource_hash: bbbb\n---\n\n## Summary\n\nOriginal.\n"
+	assert.Equal(t, want, got)
+}
+
+func TestMerge_GeneratorOwnedFieldsMixedReplaceAndAppend(t *testing.T) {
+	// a already has last_updated (replace in place) but not source_hash
+	// (append) -- the two code paths in the same call, together.
+	existing := Page{Path: "wiki/sources/x.md", Content: `---
+title: 'X'
+last_updated: 2026-01-01
+---
+
+## Summary
+
+Original.
+`}
+	fresh := Page{Path: "wiki/sources/x.md", Content: `---
+last_updated: 2026-08-22
+source_hash: bbbb
+---
+
+## Summary
+
+Rewritten by the model.
+`}
+
+	got := Merge(existing, fresh).Content
+
+	want := "---\ntitle: 'X'\nlast_updated: 2026-08-22\nsource_hash: bbbb\n---\n\n## Summary\n\nOriginal.\n"
+	assert.Equal(t, want, got)
+}
+
+func TestRefreshOwned_CommentLinesSurviveUnmangled(t *testing.T) {
+	// Third review round on PR #126: parseFrontmatterBlock dropped the
+	// sibling api package's comment guard (strings.HasPrefix(trimmed, "#")).
+	// Without it, a comment line containing a colon gets cut at the colon
+	// and re-rendered with collapsed whitespace instead of surviving
+	// verbatim.
+	a := "---\n#see also:   https://x/y\ntitle: 'X'\n---\n"
+	b := "---\nsource_hash: bbbb\n---\n"
+
+	got := refreshOwned(a, b)
+	assert.Equal(t, "---\n#see also:   https://x/y\ntitle: 'X'\nsource_hash: bbbb\n---\n", got)
+}
+
+func TestRefreshOwned_IndentedListItemsWithColonsAreNotMisparsedAsKeys(t *testing.T) {
+	// Same round: an indented YAML block-list item that happens to contain a
+	// colon (e.g. a title with a subtitle) is a continuation line, never a
+	// top-level key, regardless of what strings.Cut finds in it. Misparsing
+	// it as a key/value pair and re-rendering strips its indentation,
+	// de-indenting it out of the list it belongs to -- and refreshOwned
+	// re-renders this block on essentially every non-skipped ingest, so this
+	// is the normal path, not an edge case.
+	a := "---\naliases:\n  - 'Chapter 3: The Reckoning'\ntitle: 'X'\n---\n"
+	b := "---\nsource_hash: bbbb\n---\n"
+
+	got := refreshOwned(a, b)
+	assert.Equal(t, "---\naliases:\n  - 'Chapter 3: The Reckoning'\ntitle: 'X'\nsource_hash: bbbb\n---\n", got)
+}

skills/close-session/SKILL.md

@@ -49,12 +49,13 @@ Persist the session via a **single `capture` call** (the `brain:capture` MCP too
 **Assemble one payload:**
 
 - **`insights[]`** — the generalizable learnings from Phase 1 (decisions/failures worth re-reading). Each: `{text, wing, hall}`; add `supersede_slug` to revise a prior note in place instead of creating a duplicate. `hall` ∈ facts/decisions/failures/hypotheses/sources.
+  Optional claim envelope, per insight: `half_life` ∈ volatile/seasonal/durable, `applies` ∈ local/homelab/universal, `claim_provenance` ∈ asserted/inferred — required together whenever either `half_life` or `applies` is set (an envelope with no provenance is rejected). A close-session insight is usually exactly the durable, generalizable, human-decided kind this describes: `half_life: durable, applies: universal, claim_provenance: asserted` is the common case, not a rare opt-in.
 - **`tickets[]`** — the issue actions from Phase 3: `{repo, action, ...}` where action ∈ create/close/comment. Owner is always `mathias` (server-forced).
 - **`context`** — `{harness: "claudeai-chat", session_ref: <chatid8-or-slug>, fidelity: "live-capture", actor: "mathias", classification: <see gate below>}`.
 
 **THE CLASSIFICATION GATE (read before calling — this is where capture refuses).**
 Capture computes an **effective classification = the strictest across EVERY target it touches** (each insight's `wing`, each ticket's `repo`), then refuses if that effective level is `confidential` and the origin is us-nexus (claude.ai is us-nexus). Levels come from `classification.yaml` at the brain root (source of truth, #67), with the code defaults as the floor: `hyperguild`/`homelab` → internal; `client-*` → confidential; **anything untagged → confidential (fail-safe)**.
-- **Tagged `internal` today** (safe through claude.ai): wings `hyperguild`, `homelab`; repos `brain`, `ai-sessions`, `infra`, `hyperguild`, `homelab`, `tapir`, `agentsquad`, `jepa-fx-risk`, `swedsl`. Treat `classification.yaml` as authoritative — this list is a hint, not gospel.
+- **The rule, not a list**: untagged → confidential (fail-safe). `classification.yaml` at the brain root is the sole authority on what's tagged `internal` today — it grew from 10 to ~39 repos in one sweep (hyperguild#91) and will keep moving, so read the file rather than trust an enumeration frozen at whatever moment this skill was last edited.
 - Declare `context.classification: "internal"` for normal homelab work.
 - Insight `wing`s and ticket `repo`s are classification INPUTS, not free-form metadata — every target must resolve `internal` or the whole capture escalates to `confidential` and the gate refuses via claude.ai. Listing the central homelab repos (incl. `brain`/`ai-sessions`) is now fine; they're tagged.
 - If a session genuinely touched **`client-*` or otherwise-untagged** material, it cannot be captured through claude.ai — note that in the verdict rather than trying to force it.