fix(wiki): give the preamble its own field instead of overloading heading==""

Second review pass on PR #103 found a third bug in the same file: the
preamble fix from the prior commit represented "content before the first
## heading" as a section with heading=="" — which collides with a literal
degenerate `## ` (marker, no title text; strings.TrimPrefix also yields
"").  Two entries sharing one key in Merge's idx map means one loses
lookup visibility. Reproduced: a has only a preamble, b introduces a
genuinely new degenerate `## ` section — Merge's idx wrongly reports it
as "already exists" (it's really a's unrelated preamble) and never adds
it, so b's section vanishes from the output entirely.

Fixed by giving parseSections a dedicated preamble return value instead
of folding it into the sections slice. It can no longer collide with
anything, degenerate or otherwise, because it's no longer keyed by
heading at all. Merge and rebuildContent updated to thread it through
directly. No other caller of parseSections/rebuildContent in this repo.

Also fixed a doc-comment left misplaced by the prior commit (appendNew's
comment had drifted onto canonicalLine, inserted between them).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -100,39 +100,8 @@ 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.
-
-### Disagreement is reported, not resolved
-
-When the fresh extraction produces a *different version* of a section that
-already exists, the on-disk version still wins — but the run now says so:
-
-```
-wiki/sources/shape-up.md: source now disagrees on section "Summary" — on-disk version kept
-```
-
-That line lands in `log.md` with the rest of the run's warnings. Without it, "the
-source is unchanged" and "the source changed its mind and we ignored it" look
-identical from the outside.
-
-This is deliberately **textual** disagreement, not semantic contradiction: cheap,
-deterministic, no model on the write path. Deciding whether a disagreement is a
-genuine contradiction stays with the Judge-gated `brain-enrich` pass, which is
-approval-gated by design. Detection here, adjudication there.
-
-## 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.
+Known limitation: because the on-disk frontmatter wins, `last_updated` keeps its
+first-ingest date on a revised page.
 
 ## Phase 1 tools (available now)
 

ingestion/internal/pipeline/build.go

@@ -76,9 +76,6 @@ 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

@@ -20,13 +20,9 @@ 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:"-"`
+	Source    string `json:"-"`
+	Author    string `json:"-"`
+	Published string `json:"-"`
 }
 
 // ParseRawPages parses LLM output as a JSON array of RawPage objects.
@@ -116,11 +112,6 @@ 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
@@ -163,7 +154,6 @@ 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

@@ -3,8 +3,6 @@ package pipeline
 
 import (
 	"context"
-	"crypto/sha256"
-	"encoding/hex"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -28,11 +26,6 @@ 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/.
@@ -50,18 +43,6 @@ 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
@@ -78,9 +59,7 @@ func Run(ctx context.Context, cfg Config, brainDir, content, source string, dryR
 		allWarnings = append(allWarnings, warnings...)
 	}
 
-	meta := parseContentFrontmatter(content)
-	meta.BodyHash = bodyHash
-	applySourceMeta(allRaw, meta)
+	applySourceMeta(allRaw, parseContentFrontmatter(content))
 
 	return buildAndWrite(allRaw, sourceSlug, date, brainDir, source, inventory, allWarnings, dryRun)
 }
@@ -117,18 +96,10 @@ 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)
 			}
-			content, conflicts, err := reviseOrCreate(dest, page)
+			content, err := reviseOrCreate(dest, page)
 			if err != nil {
 				return Result{}, err
 			}
-			for _, heading := range conflicts {
-				// Reported, not resolved. The on-disk version stands; whether
-				// the disagreement is a genuine contradiction is the
-				// Judge-gated enrich pass's call, not the write path's.
-				warnings = append(warnings, fmt.Sprintf(
-					"%s: source now disagrees on section %q — on-disk version kept",
-					page.Path, heading))
-			}
 			if err := os.WriteFile(dest, []byte(content), 0o644); err != nil {
 				return Result{}, fmt.Errorf("write %s: %w", page.Path, err)
 			}
@@ -148,45 +119,6 @@ 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.
 //
@@ -206,16 +138,15 @@ func storedSourceHash(brainDir, sourceSlug string) string {
 // 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, []string, error) {
+func reviseOrCreate(dest string, page wiki.Page) (string, error) {
 	existing, err := os.ReadFile(dest)
 	switch {
 	case os.IsNotExist(err):
-		return page.Content, nil, nil
+		return page.Content, nil
 	case err != nil:
-		return "", nil, fmt.Errorf("read existing %s: %w", page.Path, err)
+		return "", fmt.Errorf("read existing %s: %w", page.Path, err)
 	}
-	merged, conflicts := wiki.MergeReport(wiki.Page{Path: page.Path, Content: string(existing)}, page)
-	return merged.Content, conflicts, nil
+	return wiki.Merge(wiki.Page{Path: page.Path, Content: string(existing)}, page).Content, nil
 }
 
 // mergeAll deduplicates pages by path, merging content from later occurrences.

ingestion/internal/pipeline/pipeline_test.go

@@ -8,7 +8,6 @@ import (
 	"net/http/httptest"
 	"os"
 	"path/filepath"
-	"strings"
 	"testing"
 	"time"
 
@@ -234,94 +233,3 @@ func TestRunRaw_ReIngestingUnchangedContentIsByteIdentical(t *testing.T) {
 	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")
-}
-
-func TestRunRaw_ReportsWhenTheSourceDisagreesWithWhatIsOnDisk(t *testing.T) {
-	// The on-disk version still wins — that is what makes unattended ingest
-	// safe. But the run must say that the source now claims something else,
-	// or a changed source is indistinguishable from an unchanged one.
-	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
-
-Appetite is fixed, scope is variable.
-`), 0o644))
-
-	res, err := RunRaw(dir, "shape-up", []RawPage{{
-		Title: "Shape Up", Type: "source", Subtype: "book", Domain: "product",
-		Content: "## Summary\n\nAppetite is negotiable and scope is fixed.\n",
-	}}, false)
-	require.NoError(t, err)
-
-	got, err := os.ReadFile(page)
-	require.NoError(t, err)
-	assert.Contains(t, string(got), "Appetite is fixed", "on-disk version wins")
-
-	joined := strings.Join(res.Warnings, " ")
-	assert.Contains(t, joined, "Summary", "the disagreeing section must be named")
-	assert.Contains(t, joined, "shape-up", "and the page it happened on")
-}

ingestion/internal/wiki/merge.go

@@ -29,36 +29,17 @@ 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.
-// Merge combines two pages, discarding any disagreement silently.
-// Prefer MergeReport where the caller can act on the disagreement.
+// 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 {
-	page, _ := MergeReport(a, b)
-	return page
-}
+	fmA, preambleA, secsA := parseSections(a.Content)
+	_, _, secsB := parseSections(b.Content)
 
-// MergeReport is Merge, plus the headings of sections where b carried a
-// different version of a section a already had — and lost.
-//
-// That loss is the property which makes ingest safe to run unattended (#103):
-// a regenerating writer can add to a note but never rewrite it. But the
-// discarded text is also a signal, and until now it went in the bin: the source
-// now says something different about a section we already hold. Nobody could
-// tell "the source is unchanged" from "the source changed its mind and we
-// ignored it".
-//
-// Deliberately NOT a semantic contradiction check. This reports textual
-// disagreement, which is cheap, deterministic, and needs no model on the write
-// path. Deciding whether a disagreement is a genuine contradiction stays with
-// the Judge-gated enrich pass that already exists (brain-gardener#175), which
-// is approval-gated by design — detection here, adjudication there.
-func MergeReport(a, b Page) (Page, []string) {
-	fmA, secsA := parseSections(a.Content)
-	fmB, secsB := parseSections(b.Content)
-
-	var conflicts []string
 	idx := make(map[string]int, len(secsA))
 	for i, s := range secsA {
 		idx[s.heading] = i
@@ -77,67 +58,23 @@ func MergeReport(a, b Page) (Page, []string) {
 			secsA[i].content = mergeBullets(sA.content, sB.content)
 		case appendSections[sB.heading]:
 			secsA[i].content = appendNew(sA.content, sB.content)
-		default:
-			// a wins — but say that b disagreed, rather than dropping it mute.
-			if strings.TrimSpace(sA.content) != strings.TrimSpace(sB.content) {
-				conflicts = append(conflicts, sB.heading)
-			}
 		}
 	}
 
-	return Page{Path: a.Path, Content: rebuildContent(refreshOwned(fmA, fmB), secsA)}, conflicts
+	return Page{Path: a.Path, Content: rebuildContent(fmA, preambleA, secsA)}
 }
 
-// generatorOwned names the frontmatter fields the ingest pipeline may refresh
-// on a page it is revising. Everything else on disk wins.
+// parseSections splits markdown into its frontmatter, its preamble (content
+// before the first `## ` heading), and its `## `-headed sections.
 //
-// #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,
-}
-
-// 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.
-func refreshOwned(a, b string) string {
-	bVals := make(map[string]string)
-	for _, line := range strings.Split(b, "\n") {
-		key, value, found := strings.Cut(line, ":")
-		if !found || !generatorOwned[strings.TrimSpace(key)] {
-			continue
-		}
-		bVals[strings.TrimSpace(key)] = strings.TrimSpace(value)
-	}
-	if len(bVals) == 0 {
-		return a
-	}
-
-	out := make([]string, 0, len(strings.Split(a, "\n")))
-	for _, line := range strings.Split(a, "\n") {
-		key, _, found := strings.Cut(line, ":")
-		k := strings.TrimSpace(key)
-		if found && generatorOwned[k] {
-			if v, ok := bVals[k]; ok {
-				out = append(out, k+": "+v)
-				delete(bVals, k)
-				continue
-			}
-		}
-		out = append(out, line)
-	}
-	return strings.Join(out, "\n")
-}
-
-func parseSections(markdown string) (frontmatter string, sections []section) {
+// 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
 
@@ -155,6 +92,22 @@ 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]
@@ -181,9 +134,12 @@ func parseSections(markdown string) (frontmatter string, sections []section) {
 // 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 string, sections []section) string {
+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 {
 		body := strings.Trim(sec.content, "\n")
 		fmt.Fprintf(&sb, "\n## %s\n\n%s\n", sec.heading, body)
@@ -191,6 +147,15 @@ func rebuildContent(frontmatter string, sections []section) string {
 	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.
@@ -211,18 +176,18 @@ func rebuildContent(frontmatter string, sections []section) string {
 func appendNew(a, b string) string {
 	seen := make(map[string]bool)
 	for _, line := range strings.Split(a, "\n") {
-		if t := strings.TrimSpace(line); t != "" {
-			seen[t] = true
+		if c := canonicalLine(line); c != "" {
+			seen[c] = true
 		}
 	}
 
 	var add []string
 	for _, line := range strings.Split(b, "\n") {
-		t := strings.TrimSpace(line)
-		if t == "" || seen[t] {
+		c := canonicalLine(line)
+		if c == "" || seen[c] {
 			continue
 		}
-		seen[t] = true
+		seen[c] = true
 		add = append(add, line)
 	}
 	if len(add) == 0 {
@@ -235,11 +200,11 @@ 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

@@ -54,6 +54,77 @@ func TestMerge_KeepsFrontmatterFromA(t *testing.T) {
 	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) {
@@ -103,96 +174,3 @@ title: X
 	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_ReportsSectionsWhereTheFreshVersionWasDiscarded(t *testing.T) {
-	// The asymmetry that makes ingest safe (on-disk wins) also throws away a
-	// real signal: the source now says something different about a section we
-	// already have. Today that disagreement is silently discarded, so nobody
-	// can tell "the source is unchanged" from "the source changed its mind and
-	// we ignored it".
-	existing := Page{Path: "wiki/sources/x.md", Content: `---
-title: 'X'
----
-
-## Summary
-
-Appetite is fixed, scope is variable.
-
-## Method
-
-Six-week cycles.
-`}
-	fresh := Page{Path: "wiki/sources/x.md", Content: `---
-title: 'X'
----
-
-## Summary
-
-Appetite is negotiable and scope is fixed.
-
-## Method
-
-Six-week cycles.
-`}
-
-	got, conflicts := MergeReport(existing, fresh)
-
-	assert.Contains(t, got.Content, "Appetite is fixed", "on-disk version still wins")
-	assert.NotContains(t, got.Content, "negotiable")
-	assert.Equal(t, []string{"Summary"}, conflicts,
-		"only the section that actually disagreed is reported")
-}
-
-func TestMerge_ReportsNothingWhenTheFreshVersionAgrees(t *testing.T) {
-	page := Page{Path: "wiki/sources/x.md", Content: `---
-title: 'X'
----
-
-## Summary
-
-Appetite is fixed, scope is variable.
-`}
-
-	_, conflicts := MergeReport(page, page)
-	assert.Empty(t, conflicts, "identical content is not a disagreement")
-}