diff --git a/.github/workflows/measure-journal-read.yml b/.github/workflows/measure-journal-read.yml
new file mode 100644
index 000000000..ba4a7c1e6
--- /dev/null
+++ b/.github/workflows/measure-journal-read.yml
@@ -0,0 +1,39 @@
+name: Measure journal read
+
+# CEO-2 / CEO-6: one read plus evaluation of the /autoplan publication guard on
+# synthetic 120 MiB parent journals, on Linux and macOS, while the journal keeps
+# growing. Dispatched by hand on the A2 branch; never on every PR. The Linux
+# numbers are the acceptance record (<= 1000 ms, <= 256 MiB peak RSS); the
+# macOS numbers are recorded and do not gate. Results go to the job summary.
+
+on:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: measure-journal-read-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  measure:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 20
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
+      - uses: oven-sh/setup-bun@0c5077e51419868618aeaa5fe8019c62421857d6 # v2
+        with:
+          bun-version: 1.4.2
+      - name: Install dependencies
+        run: bun install --frozen-lockfile
+      - name: Measure one guarded read (3 runs per journal)
+        run: |
+          bun scripts/measure-journal-read.ts --runs 3 | tee "$RUNNER_TEMP/measure.md"
+          cat "$RUNNER_TEMP/measure.md" >> "$GITHUB_STEP_SUMMARY"
diff --git a/scripts/measure-journal-read.ts b/scripts/measure-journal-read.ts
new file mode 100644
index 000000000..5aa82fd2a
--- /dev/null
+++ b/scripts/measure-journal-read.ts
@@ -0,0 +1,171 @@
+#!/usr/bin/env bun
+/**
+ * CEO-2 / CEO-6 acceptance for the /autoplan guard's bounded journal read:
+ * build a synthetic parent journal around one real /autoplan invocation, keep
+ * appending to it while the guard runs, and measure one hook call (read plus
+ * evaluation) in a fresh process: wall milliseconds and peak RSS.
+ *
+ *   bun scripts/measure-journal-read.ts [--runs N] [--json] [--strict]
+ *
+ * Two journals, 120 MiB each:
+ * - `mixed`: many records of mixed size (assistant text, Bash and Read pairs,
+ *   hook attachments), about 10% before the invocation and the rest inside it.
+ * - `large-invocation`: a current invocation of many small records.
+ * Acceptance (CEO-2): at most 1000 ms and 256 MiB peak RSS on a 4-vCPU Linux
+ * runner, with an allow decision. macOS numbers are recorded, not gated
+ * (CEO-6). `--strict` exits 1 on a miss. `--measure` and `--append` are the
+ * per-run child modes; `--build <benchmark>` writes one journal and prints its
+ * metadata path, for profiling.
+ */
+import * as fs from 'node:fs';
+import * as path from 'node:path';
+import * as os from 'node:os';
+import { randomUUID } from 'node:crypto';
+
+const MiB = 1024 * 1024;
+const BUDGET_MS = 1000, BUDGET_RSS_MIB = 256;
+type Row = { type: string; message?: Record<string, unknown>; extra?: Record<string, unknown> };
+type RowMaker = (rnd: () => number, i: number) => Row;
+/** Shares of the journal: before /autoplan (`head`), inside its phase work, and after the close Read. */
+interface Benchmark { name: string; bytes: number; headShare: number; afterCloseShare: number; head: RowMaker; window: RowMaker }
+
+/** Deterministic, so every runner measures the same journal. */
+function random(seed: number) { return () => (seed = (seed * 1103515245 + 12345) % 2147483648) / 2147483648; }
+const pad = (n: number) => 'x'.repeat(Math.max(0, Math.round(n)));
+/** The envelope Claude Code writes on every assistant message (model, usage), so record sizes match real journals. */
+const assistant = (i: number, content: unknown[]): Row => ({ type: 'assistant', message: { id: `msg_pad${i}`, type: 'message', role: 'assistant',
+  model: 'claude-opus-4-1-20250805', content, stop_reason: null, stop_sequence: null,
+  usage: { input_tokens: 4, cache_creation_input_tokens: 812, cache_read_input_tokens: 48213, output_tokens: 312, service_tier: 'standard' } },
+  extra: { requestId: `req_pad${i}`, userType: 'external', gitBranch: 'main' } });
+
+function mixedRow(rnd: () => number, i: number): Row {
+  const p = rnd(), id = `toolu_pad${i}`;
+  if (p < 0.4) return assistant(i, [{ type: 'text', text: pad(300 + rnd() * 900) }]);
+  if (p < 0.55) return assistant(i, [{ type: 'tool_use', id, name: 'Bash', input: { command: `ls ${pad(40)}` } }]);
+  if (p < 0.7) return { type: 'user', message: { role: 'user', content: [{ type: 'tool_result', tool_use_id: `${id}b`, content: pad(300 + rnd() * 2700), is_error: false }] },
+    extra: { toolUseResult: { stdout: pad(100), stderr: '' } } };
+  if (p < 0.78) {
+    const content = pad(4000 + rnd() * 36000);
+    return { type: 'user', message: { role: 'user', content: [{ type: 'tool_result', tool_use_id: `${id}r`, content }] },
+      extra: { toolUseResult: { type: 'text', file: { filePath: '/repo/src/file.ts', content, numLines: 400, startLine: 1, totalLines: 400 } } } };
+  }
+  return { type: 'attachment', extra: { attachment: { type: 'hook_success', hookEvent: 'PostToolUse', content: pad(150 + rnd() * 300) } } };
+}
+
+function smallRow(rnd: () => number, i: number): Row {
+  const p = rnd(), id = `toolu_small${i}`;
+  if (p < 0.35) return assistant(i, [{ type: 'text', text: pad(40 + rnd() * 160) }]);
+  if (p < 0.6) return assistant(i, [{ type: 'tool_use', id, name: 'Grep', input: { pattern: 'x' } }]);
+  if (p < 0.85) return { type: 'user', message: { role: 'user', content: [{ type: 'tool_result', tool_use_id: `${id}g`, content: pad(20 + rnd() * 200), is_error: false }] } };
+  return { type: 'attachment', extra: { attachment: { type: 'hook_success', hookEvent: 'PostToolUse', content: pad(50) } } };
+}
+
+const BENCHMARKS: Benchmark[] = [
+  { name: 'mixed', bytes: 120 * MiB, headShare: 0.1, afterCloseShare: 0.02, head: mixedRow, window: mixedRow },
+  // ENG-5: a current invocation of many small records (about 60k), after an ordinary mixed history.
+  { name: 'large-invocation', bytes: 120 * MiB, headShare: 0.6, afterCloseShare: 0.01, head: mixedRow, window: smallRow },
+];
+
+/** Build one journal: a published Phase 1 and the Phase 2 entry Read as the current, journaled call. */
+async function build(bench: Benchmark) {
+  const { guardFixture, section } = await import('../test/helpers/autoplan-guard-fixture');
+  const f = guardFixture('ceo');
+  f.publish();
+  f.use('next', 'Read', { file_path: section('design-phase.md') });
+  const step = (id: string) => f.steps.findIndex(s => s.kind === 'result' && s.id === id);
+  const head = bench.bytes * bench.headShare, after = bench.bytes * bench.afterCloseShare, window = bench.bytes - head - after;
+  const rnd = random(bench.name.length);
+  let i = 0, records = 0;
+  const fill = (budget: number, row: RowMaker) => {
+    const rows: Row[] = [];
+    // About 300 bytes of per-record metadata (uuid, parent, cwd, session, version, timestamp) join each row.
+    for (let used = 0; used < budget; i++) { const r = row(rnd, i); rows.push(r); used += JSON.stringify(r).length + 300; }
+    records += rows.length;
+    return rows;
+  };
+  // An earlier typed conversation that ended its turn; then /autoplan's phase work after init and after the
+  // entry Read; then a little after the close Read.
+  const earlier = (): Row[] => [{ type: 'user', message: { role: 'user', content: 'Review the retry change first.' },
+    extra: { origin: { kind: 'human' }, promptSource: 'typed', promptId: randomUUID() } }, ...fill(head, bench.head),
+    { type: 'assistant', message: { role: 'assistant', id: 'msg_earlier_end', content: [{ type: 'text', text: 'Done.' }], stop_reason: 'end_turn' } }];
+  f.journal(f.steps.length, at => at === -1 ? earlier() : at === step('init') || at === step('entry') ? fill(window / 2, bench.window)
+    : at === step('close') ? fill(after, bench.window) : []);
+  const input = f.input('next', 'Read', { file_path: section('design-phase.md') });
+  const meta = path.join(f.cwd, 'measure.json');
+  fs.writeFileSync(meta, JSON.stringify({ input, cwd: f.cwd, stateRoot: f.stateRoot }));
+  return { f, meta, records };
+}
+
+/** Child: one hook call in a fresh process; peak RSS is this process's own. */
+async function measure(meta: string) {
+  const { input, cwd, stateRoot } = JSON.parse(fs.readFileSync(meta, 'utf8'));
+  const { runPublicationHook } = await import('../autoplan/bin/phase-publication-hook.ts');
+  const root = fs.realpathSync(path.join(import.meta.dir, '..'));
+  process.env.CLAUDE_PROJECT_DIR = cwd; process.env.GSTACK_STATE_ROOT = stateRoot; process.env.GSTACK_HOME = stateRoot;
+  const started = performance.now();
+  const output: any = await runPublicationHook(input, root);
+  const wallMs = performance.now() - started;
+  const decision = output?.hookSpecificOutput?.permissionDecision === 'deny' ? `deny: ${output.hookSpecificOutput.permissionDecisionReason}`
+    : output?.systemMessage ? `unverified: ${output.systemMessage}` : 'allow';
+  // resourceUsage().maxRSS is in kilobytes on Linux and macOS.
+  process.stdout.write(JSON.stringify({ wallMs: Math.round(wallMs), peakRssMiB: Math.round(process.resourceUsage().maxRSS / 1024), decision }) + '\n');
+}
+
+/** Child: Claude Code keeps writing while the guard reads (progress records outside the conversation chain). */
+function append(file: string) {
+  const fd = fs.openSync(file, 'a');
+  let n = 0;
+  const tick = () => {
+    fs.writeSync(fd, JSON.stringify({ type: 'progress', uuid: randomUUID(), parentUuid: randomUUID(), isSidechain: false,
+      sessionId: path.basename(file, '.jsonl'), cwd: path.dirname(file), timestamp: new Date().toISOString(), data: pad(800), n: n++ }) + '\n');
+    setTimeout(tick, 1);
+  };
+  tick();
+}
+
+async function child(args: string[], timeoutMs: number) {
+  const proc = Bun.spawn([process.execPath, import.meta.path, ...args], { stdout: 'pipe', stderr: 'inherit' });
+  const timer = setTimeout(() => proc.kill(), timeoutMs);
+  const text = await new Response(proc.stdout).text();
+  clearTimeout(timer);
+  if ((await proc.exited) !== 0) throw new Error(`measure child failed: ${args.join(' ')}`);
+  return JSON.parse(text.trim());
+}
+
+async function main() {
+  const argv = process.argv.slice(2);
+  if (argv[0] === '--measure') return measure(argv[1]!);
+  if (argv[0] === '--append') return append(argv[1]!);
+  if (argv[0] === '--build') { const built = await build(BENCHMARKS.find(b => b.name === argv[1])!); return console.log(built.meta); }
+  const requested = argv.includes('--runs') ? Number(argv[argv.indexOf('--runs') + 1]) : 3;
+  const runs = Number.isInteger(requested) && requested > 0 ? requested : 3;
+  const results = [];
+  for (const bench of BENCHMARKS) {
+    const built = await build(bench);
+    try {
+      for (let run = 1; run <= runs; run++) {
+        const before = fs.statSync(built.f.transcript).size;
+        const appender = Bun.spawn([process.execPath, import.meta.path, '--append', built.f.transcript], { stdout: 'ignore', stderr: 'inherit' });
+        await Bun.sleep(50);
+        try {
+          const measured = await child(['--measure', built.meta], 60_000);
+          results.push({ benchmark: bench.name, run, journalMiB: Number((before / MiB).toFixed(1)), records: built.records,
+            appendedBytes: fs.statSync(built.f.transcript).size - before, ...measured,
+            pass: measured.wallMs <= BUDGET_MS && measured.peakRssMiB <= BUDGET_RSS_MIB && measured.decision === 'allow' });
+        } finally { appender.kill(); await appender.exited; }
+      }
+    } finally { built.f.cleanup(); }
+  }
+  const platform = { os: `${os.platform()} ${os.release()}`, arch: os.arch(), cpus: os.cpus().length, cpu: os.cpus()[0]?.model, bun: Bun.version };
+  if (argv.includes('--json')) process.stdout.write(JSON.stringify({ platform, budget: { ms: BUDGET_MS, rssMiB: BUDGET_RSS_MIB }, results }, null, 2) + '\n');
+  else {
+    console.log(`# Journal read measurement (${platform.os}, ${platform.arch}, ${platform.cpus} vCPU, Bun ${platform.bun})`);
+    console.log('| benchmark | run | journal MiB | records | appended bytes | wall ms | peak RSS MiB | decision | verdict |');
+    console.log('|---|---|---|---|---|---|---|---|---|');
+    for (const r of results) console.log(`| ${r.benchmark} | ${r.run} | ${r.journalMiB} | ${r.records} | ${r.appendedBytes} | ${r.wallMs} | ` +
+      `${r.peakRssMiB} | ${r.decision.slice(0, 60)} | ${r.pass ? 'PASS' : 'MISS'} |`);
+  }
+  if (argv.includes('--strict') && results.some(r => !r.pass)) process.exit(1);
+}
+
+await main();
diff --git a/scripts/test-pr-profile.ts b/scripts/test-pr-profile.ts
index 667ade7a7..88ecbce2b 100644
--- a/scripts/test-pr-profile.ts
+++ b/scripts/test-pr-profile.ts
@@ -226,6 +226,7 @@ export const FREE_ONLY_PR_FILES = [
   '.github/workflows/dependency-review.yml',
   '.github/workflows/free-tests.yml',
   '.github/workflows/make-pdf-gate.yml',
+  '.github/workflows/measure-journal-read.yml',
   '.github/workflows/native-qualification.yml',
   '.github/workflows/osv-scanner.yml',
   '.github/workflows/platform-qualification.yml',