diff --git a/src/cli.ts b/src/cli.ts
index e1cb8dbe2..300f241c5 100755
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -1396,6 +1396,14 @@ async function handleCliOnly(command: string, args: string[]) {
     return;
   }
 
+  // v0.42.x (#2390): `gbrain eval chronicle` is deterministic — brings its own
+  // in-memory PGLite, no DB/gateway. CI fixture gate runs anywhere.
+  if (command === 'eval' && args[0] === 'chronicle') {
+    const { runEvalChronicle } = await import('./commands/eval-chronicle.ts');
+    setCliExitVerdict(await runEvalChronicle(args.slice(1)));
+    return;
+  }
+
   // v0.41.13.0: `gbrain eval conversation-parser` is pure-function
   // (parses fixture JSONL, runs parseConversation, scores results).
   // No DB access; bypass connectEngine entirely so the CI fixture
diff --git a/src/commands/eval-chronicle.ts b/src/commands/eval-chronicle.ts
new file mode 100644
index 000000000..fe9bcfad7
--- /dev/null
+++ b/src/commands/eval-chronicle.ts
@@ -0,0 +1,44 @@
+// v0.42.x — Life Chronicle (#2390) `gbrain eval chronicle` (Phase A.9).
+// Deterministic, brings its own in-memory PGLite (no DB, no gateway), so the
+// CI fixture gate runs anywhere. Exit 0 only on a perfect score.
+import { PGLiteEngine } from '../core/pglite-engine.ts';
+import { runChronicleEval } from '../eval/chronicle/harness.ts';
+
+const HELP = `Usage: gbrain eval chronicle [--json]
+
+Deterministic Life Chronicle (#2390) feature eval. Builds a synthetic month
+corpus with a known gold chronology + a planted ontology supersession + a
+planted conflict, then scores the chronicle layer on: day reconstruction
+(intra-day order), last-seen exact date, ontology supersession + --asof
+time-travel, contradiction surfacing, and source isolation.
+
+Exit code 0 iff every task passes.
+`;
+
+export async function runEvalChronicle(args: string[]): Promise<number> {
+  if (args.includes('--help') || args.includes('-h')) {
+    process.stdout.write(HELP);
+    return 0;
+  }
+  const json = args.includes('--json');
+  const engine = new PGLiteEngine();
+  await engine.connect({ database_url: '' });
+  await engine.initSchema();
+  try {
+    const result = await runChronicleEval(engine);
+    if (json) {
+      process.stdout.write(`${JSON.stringify(result, null, 2)}\n`);
+    } else {
+      process.stderr.write(
+        `[eval chronicle] ${result.passed}/${result.total} tasks passed ` +
+        `(score ${(result.score * 100).toFixed(0)}%)\n`,
+      );
+      for (const t of result.tasks) {
+        process.stderr.write(`  ${t.passed ? 'PASS' : 'FAIL'} ${t.id} — ${t.detail}\n`);
+      }
+    }
+    return result.score === 1 ? 0 : 1;
+  } finally {
+    await engine.disconnect();
+  }
+}
diff --git a/src/eval/chronicle/harness.ts b/src/eval/chronicle/harness.ts
new file mode 100644
index 000000000..4b75f21ba
--- /dev/null
+++ b/src/eval/chronicle/harness.ts
@@ -0,0 +1,89 @@
+// v0.42.x — Life Chronicle (#2390) feature eval (Phase A.9), the PRIMARY proof.
+//
+// Deterministic + CI-safe (no LLM): builds a small synthetic corpus with a KNOWN
+// gold chronology + a planted ontology supersession + a planted conflict, then
+// asserts the chronicle layer answers the temporal/longitudinal questions
+// correctly. This is the "does the feature deliver value" bar from the North
+// Star — chronology reconstruction, last-seen, supersession time-travel,
+// contradiction surfacing, source isolation — measured against gold, not vibes.
+//
+// The OFF baseline (raw meeting pages) structurally CANNOT order intra-day
+// events or time-travel ontology; the ON path (chronicle ops) does. We score
+// the ON path against gold; a perfect score is the proof the ops are correct.
+import type { BrainEngine } from '../../core/engine.ts';
+import { runChronicleExtract, type ChronicleJudge } from '../../core/chronicle/extract-events.ts';
+
+export interface ChronicleEvalTask { id: string; passed: boolean; detail: string }
+export interface ChronicleEvalResult {
+  tasks: ChronicleEvalTask[];
+  passed: number;
+  total: number;
+  score: number; // passed / total, [0,1]
+}
+
+const ALICE = 'people/alice-example';
+const BOB = 'people/bob-example';
+
+/** Seed the synthetic corpus into a fresh engine (schema already initialized). */
+export async function seedChronicleEvalCorpus(engine: BrainEngine): Promise<void> {
+  // Two same-day meetings → two events, gold intra-day order AM then PM.
+  await engine.putPage('meetings/2026-03-02-am', {
+    type: 'meeting', title: 'Morning standup', compiled_truth: 'x'.repeat(120),
+    frontmatter: { attendees: [ALICE] }, effective_date: new Date('2026-03-02T09:00:00Z'),
+  });
+  await engine.putPage('meetings/2026-03-02-pm', {
+    type: 'meeting', title: 'Afternoon review', compiled_truth: 'y'.repeat(120),
+    frontmatter: { attendees: [ALICE] }, effective_date: new Date('2026-03-02T15:00:00Z'),
+  });
+  const judge = (when: string, what: string): ChronicleJudge => async () => ({
+    events: [{ when, who: [ALICE], what, kind: 'meeting' }],
+  });
+  await runChronicleExtract(engine, { slug: 'meetings/2026-03-02-am', judge: judge('2026-03-02T09:00:00Z', 'Morning standup') });
+  await runChronicleExtract(engine, { slug: 'meetings/2026-03-02-pm', judge: judge('2026-03-02T15:00:00Z', 'Afternoon review') });
+
+  // Ontology: alice was a founder, became an advisor (forward supersession).
+  await engine.mergeOntologyFact({ entitySlug: ALICE, dimension: 'role', value: 'founder', source: 'meetings/2024-01-10', validFrom: '2024-01-01' });
+  await engine.mergeOntologyFact({ entitySlug: ALICE, dimension: 'role', value: 'advisor', source: 'meetings/2026-03-02-pm', validFrom: '2026-03-01' });
+
+  // Planted conflict: bob has two backdated-vs-forward open values from 2 sources.
+  await engine.mergeOntologyFact({ entitySlug: BOB, dimension: 'role', value: 'advisor', source: 'meetings/a', validFrom: '2026-05-01' });
+  await engine.mergeOntologyFact({ entitySlug: BOB, dimension: 'role', value: 'founder', source: 'meetings/b', validFrom: '2026-01-01' });
+}
+
+export async function runChronicleEval(engine: BrainEngine): Promise<ChronicleEvalResult> {
+  await seedChronicleEvalCorpus(engine);
+  const tasks: ChronicleEvalTask[] = [];
+  const check = (id: string, ok: boolean, detail: string) => tasks.push({ id, passed: ok, detail });
+
+  // 1. Day reconstruction in correct intra-day order.
+  const day = await engine.getTimelineForDate('2026-03-02', { sourceId: 'default' });
+  const order = day.map((r) => r.summary);
+  check('day_order', JSON.stringify(order) === JSON.stringify(['Morning standup', 'Afternoon review']),
+    `order=${JSON.stringify(order)}`);
+
+  // 2. Last-seen exact date.
+  const ls = await engine.getLastSeen(ALICE, { sourceId: 'default' });
+  check('last_seen', ls.last_date === '2026-03-02', `last_date=${ls.last_date}`);
+
+  // 3. Supersession: current value is the new one.
+  const now = await engine.getOntology(ALICE, { sourceId: 'default' });
+  const roleNow = now.find((v) => v.dimension === 'role')?.value;
+  check('supersession_now', roleNow === 'advisor', `role_now=${roleNow}`);
+
+  // 4. Valid-time travel: as-of before the change returns the prior value.
+  const past = await engine.getOntology(ALICE, { sourceId: 'default', asof: '2025-01-01' });
+  const rolePast = past.find((v) => v.dimension === 'role')?.value;
+  check('supersession_asof', rolePast === 'founder', `role_asof=${rolePast}`);
+
+  // 5. Contradiction surfaced (genuine disagreement, not supersession).
+  const conflicts = await engine.findOntologyConflicts({ sourceId: 'default' });
+  check('conflict_surfaced', conflicts.some((c) => c.entity_slug === BOB && c.dimension === 'role'),
+    `conflicts=${conflicts.length}`);
+
+  // 6. Source isolation: querying another source leaks nothing.
+  const otherSource = await engine.getOntology(ALICE, { sourceId: 'nonexistent-source' });
+  check('source_isolation', otherSource.length === 0, `leaked=${otherSource.length}`);
+
+  const passed = tasks.filter((t) => t.passed).length;
+  return { tasks, passed, total: tasks.length, score: tasks.length ? passed / tasks.length : 0 };
+}
diff --git a/test/eval-chronicle.test.ts b/test/eval-chronicle.test.ts
new file mode 100644
index 000000000..cbb69222d
--- /dev/null
+++ b/test/eval-chronicle.test.ts
@@ -0,0 +1,25 @@
+/**
+ * v0.42.x — Life Chronicle (#2390) feature eval harness (Phase A.9, PRIMARY proof).
+ * The chronicle layer must answer EVERY gold task on the synthetic corpus.
+ */
+import { describe, test, expect, beforeAll, afterAll } from 'bun:test';
+import { PGLiteEngine } from '../src/core/pglite-engine.ts';
+import { runChronicleEval } from '../src/eval/chronicle/harness.ts';
+
+let engine: PGLiteEngine;
+beforeAll(async () => {
+  engine = new PGLiteEngine();
+  await engine.connect({ database_url: '' });
+  await engine.initSchema();
+});
+afterAll(async () => { await engine.disconnect(); });
+
+describe('runChronicleEval', () => {
+  test('scores a perfect 6/6 on the synthetic corpus (the value proof)', async () => {
+    const result = await runChronicleEval(engine);
+    const failed = result.tasks.filter((t) => !t.passed).map((t) => `${t.id}: ${t.detail}`);
+    expect(failed).toEqual([]); // surfaces which gold task failed, if any
+    expect(result.score).toBe(1);
+    expect(result.total).toBe(6);
+  });
+});