test(voyage): add annotation roundtrip + rollback + source_annotations integration — v4.2 Step 7

Implements SC2/SC3/SC5b/SC7 + additive-field invariant for the v4.2
annotation pipeline:

Fixtures (tests/fixtures/annotation/):
  - annotation-brief.md           — brief-validator-clean fixture
  - annotation-plan.md            — plan-validator-clean (2 steps)
  - annotation-review.md          — review-validator-clean
  - annotation-plan-large.md      — 51 steps (SC3 scale fixture)

Integration tests:
  - tests/integration/annotation-roundtrip.test.mjs — 7 cases:
    SC2 byte-identical empty round-trip across brief/plan/review,
    SC3 scale (51 steps + 100 anchors) round-trip,
    SC7 parseAnchors(stripAnchors(addAnchors(...))) === [] per target.
  - tests/integration/schema-rollback.test.mjs — 4 cases:
    SC5b validator-FAIL -> revisionGuard rolls back byte-identical
    (sha256 invariant) for brief/plan/review + cross-target sweep.
    .local.bak deleted on rollback path (validator-PASS path tested
    in lib/util/revision-guard tests).
  - tests/lib/source-annotations.test.mjs — 6 cases mirroring
    tests/lib/source-findings.test.mjs additive-field pattern: each
    validator (brief/plan/review) accepts source_annotations as
    additive-optional, parser extracts as array of dicts, entries
    conform to documented shape, baseline forward-compat (artifacts
    without source_annotations still validate).

Verify: node --test tests/integration/annotation-roundtrip.test.mjs
       tests/integration/schema-rollback.test.mjs
       tests/lib/source-annotations.test.mjs -> 17 pass / 0 fail.
Full npm test: 577 pass / 0 fail / 2 skipped (Docker).

Refs plan.md Step 7 + plan-critic M4 + plan-critic B4.

plugins/voyage/tests/fixtures/annotation/annotation-brief.md

@@ -0,0 +1,34 @@
+---
+type: trekbrief
+brief_version: "1.0"
+task: Demo task for annotation round-trip fixture
+slug: annotation-brief-demo
+research_topics: 0
+research_status: complete
+---
+
+# Demo brief for annotation round-trip
+
+This fixture is used by `tests/integration/annotation-roundtrip.test.mjs`
+to verify SC2 (byte-identical empty-anchor round-trip) and SC7 (per-target
+isolation against `validateBrief`).
+
+It carries no anchors. The round-trip test runs:
+`stripAnchors(addAnchors(body, [])) === body`.
+
+## Intent
+
+Provide a minimal brief that validates against `brief-validator.mjs` so
+the round-trip integration test has a real artifact to revise.
+
+## Goal
+
+The brief should validate cleanly (no errors, no warnings) and contain
+enough body text that adding an anchor and stripping it back is a
+non-trivial operation.
+
+## Success Criteria
+
+- File parses via `parseDocument`.
+- `validateBrief` returns `valid: true`.
+- `stripAnchors(addAnchors(body, []))` is byte-identical to body.

plugins/voyage/tests/fixtures/annotation/annotation-plan.md

@@ -0,0 +1,64 @@
+---
+plan_version: 1.7
+profile: balanced
+---
+
+# Demo plan for annotation round-trip
+
+This fixture is used by `tests/integration/annotation-roundtrip.test.mjs`
+to verify SC2 (byte-identical empty-anchor round-trip) and SC7 (per-target
+isolation against `validatePlan`).
+
+## Context
+
+A minimal plan with two steps. Each step has a Manifest block so
+`plan-validator --strict` accepts the file.
+
+## Implementation Plan
+
+### Step 1: Touch a sentinel file
+
+- **Files:** `tmp/sentinel-1.txt` (new)
+- **Changes:** Create the sentinel file with the literal content "step-1".
+- **Reuses:** none.
+- **Test first:** none — sentinel-only step.
+- **Verify:** `test -f tmp/sentinel-1.txt`
+- **On failure:** revert.
+- **Checkpoint:** `git commit -m "chore: sentinel step 1"`
+- **Manifest:**
+  ```yaml
+  manifest:
+    expected_paths:
+      - tmp/sentinel-1.txt
+    min_file_count: 1
+    commit_message_pattern: "^chore: sentinel step 1"
+    bash_syntax_check: []
+    forbidden_paths: []
+    must_contain: []
+  ```
+
+### Step 2: Touch a second sentinel file
+
+- **Files:** `tmp/sentinel-2.txt` (new)
+- **Changes:** Create the sentinel file with the literal content "step-2".
+- **Reuses:** none.
+- **Test first:** none.
+- **Verify:** `test -f tmp/sentinel-2.txt`
+- **On failure:** revert.
+- **Checkpoint:** `git commit -m "chore: sentinel step 2"`
+- **Manifest:**
+  ```yaml
+  manifest:
+    expected_paths:
+      - tmp/sentinel-2.txt
+    min_file_count: 1
+    commit_message_pattern: "^chore: sentinel step 2"
+    bash_syntax_check: []
+    forbidden_paths: []
+    must_contain: []
+  ```
+
+## Verification
+
+- `npm test` passes.
+- Both sentinel files exist.

plugins/voyage/tests/fixtures/annotation/annotation-review.md

@@ -0,0 +1,32 @@
+---
+type: trekreview
+review_version: "1.0"
+task: Demo review for annotation round-trip
+slug: annotation-review-demo
+project_dir: .claude/projects/2026-05-09-annotation-demo
+brief_path: .claude/projects/2026-05-09-annotation-demo/brief.md
+scope_sha_end: 0000000000000000000000000000000000000000
+reviewed_files_count: 0
+findings: []
+---
+
+# Demo review for annotation round-trip
+
+This fixture is used by `tests/integration/annotation-roundtrip.test.mjs`
+to verify SC2 (byte-identical empty-anchor round-trip) and SC7 (per-target
+isolation against `validateReview`).
+
+## Executive Summary
+
+Verdict: ALLOW. No findings. This is a synthetic fixture used to exercise
+the round-trip mechanics; it does not represent a real review.
+
+## Coverage
+
+| File | Treatment |
+|------|-----------|
+| _none_ | _no diff_ |
+
+## Remediation Summary
+
+No remediation needed. ALLOW.

plugins/voyage/tests/integration/annotation-roundtrip.test.mjs

@@ -0,0 +1,133 @@
+// tests/integration/annotation-roundtrip.test.mjs
+// SC2 + SC3 + SC7 integration tests for the annotation round-trip pipeline.
+//
+// SC2 (byte-identical empty round-trip):
+//   For each target fixture (brief/plan/review), assert that
+//   stripAnchors(addAnchors(body, [])) === body, byte-for-byte.
+//
+// SC3 (scale: >=50 steps + >=100 anchors):
+//   On the 51-step scale fixture, generate 100 anchors above varied lines,
+//   run addAnchors -> stripAnchors, assert the original body is restored
+//   byte-for-byte.
+//
+// SC7 (per-target isolation):
+//   parseAnchors(stripAnchors(addAnchors(body, anchors))) === [] — once
+//   anchors are stripped, no residual voyage:anchor markers remain that
+//   parseAnchors would re-detect.
+
+import { test } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { readFileSync } from 'node:fs';
+import { join, dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { parseDocument } from '../../lib/util/frontmatter.mjs';
+import { parseAnchors, addAnchors, stripAnchors } from '../../lib/parsers/anchor-parser.mjs';
+
+const HERE = dirname(fileURLToPath(import.meta.url));
+const ROOT = join(HERE, '..', '..');
+const FIX_DIR = join(ROOT, 'tests/fixtures/annotation');
+
+function readBody(fixture) {
+  const text = readFileSync(join(FIX_DIR, fixture), 'utf-8');
+  const doc = parseDocument(text);
+  assert.ok(doc.valid, `fixture ${fixture} did not parse: ${(doc.errors || []).map(e => e.message).join(', ')}`);
+  return doc.parsed.body;
+}
+
+test('annotation-brief.md byte-identical empty round-trip (SC2)', () => {
+  const body = readBody('annotation-brief.md');
+  const out = stripAnchors(addAnchors(body, []));
+  assert.strictEqual(out, body, 'empty addAnchors+stripAnchors must be byte-identical');
+});
+
+test('annotation-plan.md byte-identical empty round-trip (SC2)', () => {
+  const body = readBody('annotation-plan.md');
+  const out = stripAnchors(addAnchors(body, []));
+  assert.strictEqual(out, body, 'empty addAnchors+stripAnchors must be byte-identical');
+});
+
+test('annotation-review.md byte-identical empty round-trip (SC2)', () => {
+  const body = readBody('annotation-review.md');
+  const out = stripAnchors(addAnchors(body, []));
+  assert.strictEqual(out, body, 'empty addAnchors+stripAnchors must be byte-identical');
+});
+
+test('annotation-plan-large.md scale (51 steps + 100 anchors) round-trip (SC3)', () => {
+  const body = readBody('annotation-plan-large.md');
+  const lineCount = body.split('\n').length;
+  // Generate 100 anchors targeting safe paragraph lines. Place them above
+  // line numbers that are deliberately avoided by anchor-parser placement
+  // rules: skip anchor insertion above headings and inside fenced blocks.
+  // Strategy: pick 100 safe insertion points by walking blank lines outside
+  // fenced blocks; anchor at line N inserts above line N (so line N must
+  // be a content line, not a fence delimiter).
+  const lines = body.split('\n');
+  const safe = [];
+  let inFence = false;
+  for (let i = 0; i < lines.length; i++) {
+    const ln = lines[i];
+    if (/^```/.test(ln)) { inFence = !inFence; continue; }
+    if (inFence) continue;
+    // Skip headings, blank lines, list items, and structural anchors
+    if (ln.startsWith('#') || ln.trim() === '' || /^\s*[-*+]\s/.test(ln)) continue;
+    safe.push(i + 1); // 1-indexed line number
+  }
+  assert.ok(safe.length >= 100, `need >=100 safe insertion points; got ${safe.length}`);
+  const anchors = [];
+  for (let n = 0; n < 100; n++) {
+    anchors.push({
+      id: `ANN-${String(n + 1).padStart(4, '0')}`,
+      target: `step-${(n % 51) + 1}`,
+      line: safe[n],
+      intent: ['fix', 'change', 'question', 'block'][n % 4],
+    });
+  }
+  const annotated = addAnchors(body, anchors);
+  // sanity: 100 anchors produced
+  const parsed = parseAnchors(annotated);
+  assert.ok(parsed.valid, `parseAnchors on annotated body failed: ${(parsed.errors || []).map(e => e.message).join('; ')}`);
+  assert.strictEqual(parsed.parsed.length, 100, `expected 100 anchors after addAnchors, got ${parsed.parsed.length}`);
+  // Round-trip restores body byte-for-byte.
+  const restored = stripAnchors(annotated);
+  assert.strictEqual(restored, body, 'addAnchors -> stripAnchors must round-trip byte-identical at scale');
+});
+
+test('parseAnchors(stripAnchors(addAnchors(brief, anchors))) === [] (SC7 brief)', () => {
+  const body = readBody('annotation-brief.md');
+  const lines = body.split('\n');
+  // Pick a content line — first non-blank, non-heading line
+  const target = lines.findIndex(l => l.length > 0 && !l.startsWith('#')) + 1;
+  assert.ok(target > 0, 'brief fixture has no content lines');
+  const anchors = [{ id: 'ANN-0001', target: 'intent', line: target, intent: 'change' }];
+  const annotated = addAnchors(body, anchors);
+  const stripped = stripAnchors(annotated);
+  const result = parseAnchors(stripped);
+  assert.ok(result.valid, 'parseAnchors on stripped body should be valid');
+  assert.deepStrictEqual(result.parsed, [], 'no anchors should remain after stripAnchors');
+});
+
+test('parseAnchors(stripAnchors(addAnchors(plan, anchors))) === [] (SC7 plan)', () => {
+  const body = readBody('annotation-plan.md');
+  const lines = body.split('\n');
+  const target = lines.findIndex(l => l.startsWith('A minimal')) + 1;
+  assert.ok(target > 0, 'plan fixture missing expected content line');
+  const anchors = [{ id: 'ANN-0001', target: 'context', line: target, intent: 'fix' }];
+  const annotated = addAnchors(body, anchors);
+  const stripped = stripAnchors(annotated);
+  const result = parseAnchors(stripped);
+  assert.ok(result.valid);
+  assert.deepStrictEqual(result.parsed, []);
+});
+
+test('parseAnchors(stripAnchors(addAnchors(review, anchors))) === [] (SC7 review)', () => {
+  const body = readBody('annotation-review.md');
+  const lines = body.split('\n');
+  const target = lines.findIndex(l => l.startsWith('Verdict')) + 1;
+  assert.ok(target > 0, 'review fixture missing Verdict line');
+  const anchors = [{ id: 'ANN-0001', target: 'executive-summary', line: target, intent: 'question' }];
+  const annotated = addAnchors(body, anchors);
+  const stripped = stripAnchors(annotated);
+  const result = parseAnchors(stripped);
+  assert.ok(result.valid);
+  assert.deepStrictEqual(result.parsed, []);
+});

plugins/voyage/tests/integration/schema-rollback.test.mjs

@@ -0,0 +1,135 @@
+// tests/integration/schema-rollback.test.mjs
+// SC5b: post-write validator failure rolls back byte-identical pre-revision state.
+//
+// Exercises lib/util/revision-guard.mjs revisionGuard():
+//   - Apply a deliberately-corrupting mutator that produces an artifact
+//     the validator will reject (missing required section / wrong type).
+//   - Assert outcome === 'rolled-back'.
+//   - Assert sha256_after === sha256_before (byte-identical recovery).
+//   - Assert .local.bak is deleted on the rollback path.
+//
+// Cases:
+//   1. brief-rollback — strip a required body section
+//   2. plan-rollback — break plan structure (rename Implementation Plan)
+//   3. review-rollback — flip type to non-trekreview
+//   4. sha256-invariance-cross-target — across all three targets, verify
+//      the byte-invariance holds for at least one common corrupting class
+//      (frontmatter `type:` flip).
+
+import { test } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { copyFileSync, existsSync, mkdtempSync, readFileSync, rmSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join, dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { createHash } from 'node:crypto';
+import { revisionGuard } from '../../lib/util/revision-guard.mjs';
+import { validateBrief } from '../../lib/validators/brief-validator.mjs';
+import { validatePlan } from '../../lib/validators/plan-validator.mjs';
+import { validateReview } from '../../lib/validators/review-validator.mjs';
+
+const HERE = dirname(fileURLToPath(import.meta.url));
+const ROOT = join(HERE, '..', '..');
+const FIX_DIR = join(ROOT, 'tests/fixtures/annotation');
+
+function sha256(p) {
+  return createHash('sha256').update(readFileSync(p)).digest('hex');
+}
+
+function tmpCopy(name) {
+  const dir = mkdtempSync(join(tmpdir(), 'voyage-rollback-'));
+  const dst = join(dir, name);
+  copyFileSync(join(FIX_DIR, name), dst);
+  return { dir, path: dst };
+}
+
+test('brief-rollback: strip Goal section -> validator FAIL -> byte-identical restore', () => {
+  const { dir, path } = tmpCopy('annotation-brief.md');
+  try {
+    const sha_before = sha256(path);
+    const result = revisionGuard(
+      path,
+      ({ frontmatter, body }) => ({
+        frontmatter,
+        body: body.replace(/## Goal[\s\S]*?(?=\n## Success Criteria)/, ''), // strip Goal section
+      }),
+      validateBrief,
+    );
+    assert.strictEqual(result.outcome, 'rolled-back', `expected rolled-back, got ${result.outcome}`);
+    const sha_after = sha256(path);
+    assert.strictEqual(sha_after, sha_before, 'sha256 must be byte-identical after rollback');
+    assert.ok(!existsSync(path + '.local.bak'), '.local.bak must be deleted after rollback');
+  } finally {
+    rmSync(dir, { recursive: true, force: true });
+  }
+});
+
+test('plan-rollback: rename Implementation Plan heading -> validator FAIL -> byte-identical restore', () => {
+  const { dir, path } = tmpCopy('annotation-plan.md');
+  try {
+    const sha_before = sha256(path);
+    const result = revisionGuard(
+      path,
+      ({ frontmatter, body }) => ({
+        frontmatter,
+        // Inject a forbidden phase-style heading the plan-schema rejects (PLAN_FORBIDDEN_HEADING)
+        body: body + '\n\n### Fase 99: This forbidden heading triggers PLAN_FORBIDDEN_HEADING\n',
+      }),
+      validatePlan,
+    );
+    assert.strictEqual(result.outcome, 'rolled-back', `expected rolled-back, got ${result.outcome}`);
+    const sha_after = sha256(path);
+    assert.strictEqual(sha_after, sha_before, 'sha256 must be byte-identical after rollback');
+    assert.ok(!existsSync(path + '.local.bak'), '.local.bak must be deleted after rollback');
+  } finally {
+    rmSync(dir, { recursive: true, force: true });
+  }
+});
+
+test('review-rollback: flip type to non-trekreview -> validator FAIL -> byte-identical restore', () => {
+  const { dir, path } = tmpCopy('annotation-review.md');
+  try {
+    const sha_before = sha256(path);
+    const result = revisionGuard(
+      path,
+      ({ frontmatter, body }) => ({
+        frontmatter: { ...frontmatter, type: 'not-a-real-type' },
+        body,
+      }),
+      validateReview,
+    );
+    assert.strictEqual(result.outcome, 'rolled-back', `expected rolled-back, got ${result.outcome}`);
+    const sha_after = sha256(path);
+    assert.strictEqual(sha_after, sha_before, 'sha256 must be byte-identical after rollback');
+    assert.ok(!existsSync(path + '.local.bak'), '.local.bak must be deleted after rollback');
+  } finally {
+    rmSync(dir, { recursive: true, force: true });
+  }
+});
+
+test('sha256-invariance-cross-target: byte-identical rollback for all three targets', () => {
+  const cases = [
+    { fixture: 'annotation-brief.md', validator: validateBrief, frontmatterCorruption: { type: 'wrong-type' } },
+    { fixture: 'annotation-plan.md', validator: validatePlan, bodyCorruption: '\n\n### Fase 1: forbidden\n' },
+    { fixture: 'annotation-review.md', validator: validateReview, frontmatterCorruption: { findings: 'not-an-array' } },
+  ];
+  for (const c of cases) {
+    const { dir, path } = tmpCopy(c.fixture);
+    try {
+      const sha_before = sha256(path);
+      const result = revisionGuard(
+        path,
+        ({ frontmatter, body }) => ({
+          frontmatter: c.frontmatterCorruption ? { ...frontmatter, ...c.frontmatterCorruption } : frontmatter,
+          body: c.bodyCorruption ? body + c.bodyCorruption : body,
+        }),
+        c.validator,
+      );
+      assert.strictEqual(result.outcome, 'rolled-back', `${c.fixture}: expected rolled-back, got ${result.outcome}`);
+      assert.strictEqual(sha256(path), sha_before, `${c.fixture}: sha256 must be byte-identical after rollback`);
+      assert.ok(!existsSync(path + '.local.bak'), `${c.fixture}: .local.bak must be deleted after rollback`);
+    } finally {
+      rmSync(dir, { recursive: true, force: true });
+    }
+  }
+});

plugins/voyage/tests/lib/source-annotations.test.mjs

@@ -0,0 +1,244 @@
+// tests/lib/source-annotations.test.mjs
+// Additive-field invariant for source_annotations: array (Handover 8).
+//
+// Mirrors tests/lib/source-findings.test.mjs:9-13 — the structural three-part
+// contract that v4.2 brief-validator + plan-validator + review-validator must
+// uphold for the new optional source_annotations frontmatter field:
+//
+//   1. validators accept an artifact with source_annotations (additive optional)
+//   2. frontmatter parser extracts source_annotations as an array
+//   3. each entry has the documented annotation shape
+//      ({id, target_artifact, target_anchor, intent, ...})
+//
+// LLM behavior (the planner actually emitting source_annotations) is
+// non-testable without live invocation — this test only covers the schema
+// half. See Step 12 doc-pin for the operator-level contract.
+
+import { test } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { mkdtempSync, writeFileSync, rmSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { parseDocument } from '../../lib/util/frontmatter.mjs';
+import { validateBrief } from '../../lib/validators/brief-validator.mjs';
+import { validatePlan } from '../../lib/validators/plan-validator.mjs';
+import { validateReview } from '../../lib/validators/review-validator.mjs';
+
+const ID_RE = /^ANN-\d{4}$/;
+const VALID_INTENT = new Set(['fix', 'change', 'question', 'block']);
+
+function makeFixture(name, body) {
+  const dir = mkdtempSync(join(tmpdir(), 'voyage-source-ann-'));
+  const path = join(dir, name);
+  writeFileSync(path, body);
+  return { dir, path };
+}
+
+const BRIEF_WITH_SOURCE_ANNOTATIONS = `---
+type: trekbrief
+brief_version: "1.0"
+task: Demo brief with source_annotations
+slug: source-annotations-demo-brief
+research_topics: 0
+research_status: complete
+revision: 1
+annotation_digest: deadbeefcafe1234
+source_annotations:
+  - id: ANN-0001
+    target_artifact: brief.md
+    target_anchor: goal
+    line: 20
+    intent: change
+  - id: ANN-0002
+    target_artifact: brief.md
+    target_anchor: success-criteria
+    line: 30
+    intent: fix
+---
+
+# Demo
+
+## Intent
+
+Test fixture.
+
+## Goal
+
+Test fixture.
+
+## Success Criteria
+
+- It validates.
+`;
+
+const PLAN_WITH_SOURCE_ANNOTATIONS = `---
+plan_version: 1.7
+profile: balanced
+revision: 2
+annotation_digest: cafebabe98765432
+source_annotations:
+  - id: ANN-0001
+    target_artifact: plan.md
+    target_anchor: step-1
+    line: 25
+    intent: fix
+---
+
+# Demo plan
+
+## Implementation Plan
+
+### Step 1: Sentinel
+
+- **Files:** \`tmp/x.txt\` (new)
+- **Changes:** Touch.
+- **Verify:** \`test -f tmp/x.txt\`
+- **On failure:** revert.
+- **Checkpoint:** \`git commit -m "chore: x"\`
+- **Manifest:**
+  \`\`\`yaml
+  manifest:
+    expected_paths:
+      - tmp/x.txt
+    min_file_count: 1
+    commit_message_pattern: "^chore: x"
+    bash_syntax_check: []
+    forbidden_paths: []
+    must_contain: []
+  \`\`\`
+
+## Verification
+
+- It validates.
+`;
+
+const REVIEW_WITH_SOURCE_ANNOTATIONS = `---
+type: trekreview
+review_version: "1.0"
+task: Demo review with source_annotations
+slug: source-annotations-demo-review
+project_dir: .claude/projects/2026-05-09-demo
+brief_path: .claude/projects/2026-05-09-demo/brief.md
+scope_sha_end: 0000000000000000000000000000000000000000
+reviewed_files_count: 0
+findings: []
+revision: 1
+annotation_digest: 0123456789abcdef
+source_annotations:
+  - id: ANN-0001
+    target_artifact: review.md
+    target_anchor: executive-summary
+    line: 18
+    intent: question
+---
+
+# Demo
+
+## Executive Summary
+
+Verdict: ALLOW.
+
+## Coverage
+
+| File | Treatment |
+|------|-----------|
+| _none_ | _no diff_ |
+
+## Remediation Summary
+
+ALLOW.
+`;
+
+test('validators accept artifacts with source_annotations field (additive optional, brief)', () => {
+  const { dir, path } = makeFixture('brief.md', BRIEF_WITH_SOURCE_ANNOTATIONS);
+  try {
+    const r = validateBrief(path, { strict: true });
+    assert.ok(
+      r.valid,
+      `brief-validator rejected synthetic brief with source_annotations: ` +
+      `${(r.errors || []).map(e => `[${e.code}] ${e.message}`).join('; ')}`,
+    );
+  } finally {
+    rmSync(dir, { recursive: true, force: true });
+  }
+});
+
+test('validators accept artifacts with source_annotations field (additive optional, plan)', () => {
+  const { dir, path } = makeFixture('plan.md', PLAN_WITH_SOURCE_ANNOTATIONS);
+  try {
+    const r = validatePlan(path, { strict: true });
+    assert.ok(
+      r.valid,
+      `plan-validator rejected synthetic plan with source_annotations: ` +
+      `${(r.errors || []).map(e => `[${e.code}] ${e.message}`).join('; ')}`,
+    );
+  } finally {
+    rmSync(dir, { recursive: true, force: true });
+  }
+});
+
+test('validators accept artifacts with source_annotations field (additive optional, review)', () => {
+  const { dir, path } = makeFixture('review.md', REVIEW_WITH_SOURCE_ANNOTATIONS);
+  try {
+    const r = validateReview(path, { strict: true });
+    assert.ok(
+      r.valid,
+      `review-validator rejected synthetic review with source_annotations: ` +
+      `${(r.errors || []).map(e => `[${e.code}] ${e.message}`).join('; ')}`,
+    );
+  } finally {
+    rmSync(dir, { recursive: true, force: true });
+  }
+});
+
+test('frontmatter parser extracts source_annotations as array of dicts (per artifact)', () => {
+  const cases = [
+    { name: 'brief.md', body: BRIEF_WITH_SOURCE_ANNOTATIONS, expected: 2 },
+    { name: 'plan.md', body: PLAN_WITH_SOURCE_ANNOTATIONS, expected: 1 },
+    { name: 'review.md', body: REVIEW_WITH_SOURCE_ANNOTATIONS, expected: 1 },
+  ];
+  for (const c of cases) {
+    const doc = parseDocument(c.body);
+    assert.ok(doc.valid, `${c.name}: frontmatter did not parse: ${(doc.errors || []).map(e => e.message).join(', ')}`);
+    const sa = doc.parsed.frontmatter && doc.parsed.frontmatter.source_annotations;
+    assert.ok(Array.isArray(sa), `${c.name}: frontmatter.source_annotations is not an array (got ${typeof sa})`);
+    assert.strictEqual(sa.length, c.expected, `${c.name}: expected ${c.expected} entries, got ${sa.length}`);
+  }
+});
+
+test('source_annotations entries match documented annotation shape', () => {
+  const doc = parseDocument(BRIEF_WITH_SOURCE_ANNOTATIONS);
+  const entries = doc.parsed.frontmatter.source_annotations;
+  for (const e of entries) {
+    assert.strictEqual(typeof e, 'object', `source_annotations entry is not an object: ${JSON.stringify(e)}`);
+    assert.ok(typeof e.id === 'string' && ID_RE.test(e.id), `source_annotations[*].id must match /^ANN-\\d{4}$/, got ${JSON.stringify(e.id)}`);
+    assert.ok(typeof e.target_artifact === 'string' && e.target_artifact.endsWith('.md'),
+      `source_annotations[*].target_artifact must be a *.md path, got ${JSON.stringify(e.target_artifact)}`);
+    assert.ok(typeof e.target_anchor === 'string' && e.target_anchor.length > 0,
+      `source_annotations[*].target_anchor must be a non-empty string, got ${JSON.stringify(e.target_anchor)}`);
+    if (e.intent !== undefined && e.intent !== null) {
+      assert.ok(VALID_INTENT.has(e.intent),
+        `source_annotations[*].intent must be in {fix|change|question|block}, got ${JSON.stringify(e.intent)}`);
+    }
+  }
+});
+
+test('artifacts WITHOUT source_annotations still validate (forward-compat baseline)', () => {
+  // Forward-compat: artifacts that predate v4.2 must still validate. Fall back
+  // to an artifact with neither revision nor source_annotations.
+  const baseline = BRIEF_WITH_SOURCE_ANNOTATIONS
+    .replace(/^revision:.*\n/m, '')
+    .replace(/^annotation_digest:.*\n/m, '')
+    .replace(/^source_annotations:[\s\S]*?(?=^---$|^[A-Za-z])/m, '');
+  const { dir, path } = makeFixture('brief.md', baseline);
+  try {
+    const r = validateBrief(path, { strict: true });
+    assert.ok(
+      r.valid,
+      `brief-validator must accept artifacts WITHOUT source_annotations (forward-compat baseline): ` +
+      `${(r.errors || []).map(e => `[${e.code}] ${e.message}`).join('; ')}`,
+    );
+  } finally {
+    rmSync(dir, { recursive: true, force: true });
+  }
+});