diff --git a/CHANGELOG.md b/CHANGELOG.md
index ffe24f5d..c5ac27f3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,50 @@
 # Changelog
 
+## [1.21.1.0] - 2026-04-28
+
+## **plan-ceo-review smoke tightens. The "agent skips Step 0 and ships a plan" regression now fails the gate.**
+
+The v1.15.0.0 real-PTY harness shipped with a smoke that accepted either `'asked'` or `'plan_ready'` as success. That OR was too lax for `/plan-ceo-review` specifically: the skill template mandates Step 0A premise challenge plus Step 0F mode selection BEFORE any plan write, so reaching `plan_ready` first IS the regression. This release tightens the assertion to `'asked'` only for that smoke, and refactors the runner so the contract is testable in <1s instead of $0.50 of stochastic PTY.
+
+### The numbers that matter
+
+Numbers come from `git diff --shortstat origin/main..HEAD` and `bun test test/helpers/claude-pty-runner.unit.test.ts` on a clean tree.
+
+| Metric | Δ |
+|---|---|
+| Net branch size vs main | +162 / −65 lines (3 files) |
+| New unit tests added | **+24** (claude-pty-runner.unit.test.ts) |
+| Unit suite runtime | **14ms** (deterministic, free-tier) |
+| Real-PTY gate runs verified | **4 clean PTY runs** (3 lock-in + 1 post-refactor) |
+| Outcome assertions covered | **5/5** (was 3/5; `plan_ready` is now FAIL for plan-ceo) |
+| Reviewers run on this PR | plan-eng-review (CLEARED) + codex consult + 2 specialists + adversarial |
+
+### What this means for builders
+
+Three new classes of harness regression are now caught deterministically in the free tier instead of waiting on a $0.50 stochastic PTY run. The classifier is extracted into a pure `classifyVisible()` function so reordering branches in the polling loop fails the unit tests instead of silently shipping. Permission dialogs (which render numbered lists) are filtered out of the `'asked'` classification so a permission prompt cannot pose as a Step 0 skill question. The bare phrase `Do you want to proceed?` no longer triggers permission detection on its own — it now requires a file-edit context co-trigger, so a skill question that contains the phrase isn't mis-classified.
+
+For `/plan-ceo-review` specifically: any future preamble slim-down or template edit that lets the agent skip Step 0 and write a plan will fail the gate before the PR ships. Pull, run `bun test`, and the harness layer is provably tighter without you having to spend a token.
+
+### Itemized changes
+
+#### Added
+
+- `test/helpers/claude-pty-runner.unit.test.ts`: 24 deterministic tests covering `isPermissionDialogVisible` (with the new co-trigger contract), `isNumberedOptionListVisible`, `parseNumberedOptions`, and the new `classifyVisible()` runtime path. Free-tier, runs on every `bun test`.
+- `classifyVisible(visible)` in `claude-pty-runner.ts`: pure classifier extracted from the polling loop. Returns `{ outcome, summary } | null`. Branch order: silent_write → plan_ready → asked → null (with permission-dialog filter). Live-state branches (process exited, "Unknown command") stay in the runner.
+- `TAIL_SCAN_BYTES = 1500` exported constant. Shared between `runPlanSkillObservation` and the routing test's nav loop so tuning stays in sync.
+- `env?: Record<string, string>` option on `runPlanSkillObservation`, threaded to `launchClaudePty`. Plumbing for future env-driven test isolation (gstack-config does not yet honor env overrides; tracked as post-merge follow-up).
+
+#### Changed
+
+- `test/skill-e2e-plan-ceo-plan-mode.test.ts`: assertion narrowed from `['asked', 'plan_ready']` to `'asked'` only. Failure message now branches on `outcome` (plan_ready vs timeout vs silent_write) with a tailored diagnosis line, and references skill-template section names instead of line numbers (durable to template edits).
+- `isPermissionDialogVisible`: bare `Do you want to proceed?` now requires a file-edit context co-trigger (`Edit to <path>` or `Write to <path>`). Other clauses (`requested permissions to`, `allow all edits`, `always allow access to`, `Bash command requires permission`) remain unconditional.
+- `test/skill-e2e-plan-ceo-mode-routing.test.ts`: replaces the local `1500` magic number with the shared `TAIL_SCAN_BYTES` constant.
+
+#### For contributors
+
+- The runner change is additive and the existing sibling smokes (`plan-eng`, `plan-design`, `plan-devex`, `plan-mode-no-op`) keep their loose `['asked', 'plan_ready']` assertion. Their behavior is unchanged.
+- Post-merge follow-ups captured in `TODOS.md`: per-finding AskUserQuestion count assertion (V2), env-driven gstack-config overrides (so `QUESTION_TUNING=false` actually isolates the test), path-confusion hardening on `SANCTIONED_WRITE_SUBSTRINGS`.
+
 ## [1.15.0.0] - 2026-04-26
 
 ## **Real-PTY test harness ships. 11 plan-mode E2E tests, 23 unit tests, and 50K fewer tokens per invocation.**
diff --git a/VERSION b/VERSION
index 0550662d..6b86f767 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.15.0.0
+1.21.1.0
diff --git a/package.json b/package.json
index a2dd52d4..ba1b4f8f 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "gstack",
-  "version": "1.15.0.0",
+  "version": "1.21.1.0",
   "description": "Garry's Stack — Claude Code skills + fast headless browser. One repo, one install, entire AI engineering workflow.",
   "license": "MIT",
   "type": "module",