diff --git a/cli/__tests__/adapters.codex.test.mjs b/cli/__tests__/adapters.codex.test.mjs
index 8dd6326917..d162675a54 100644
--- a/cli/__tests__/adapters.codex.test.mjs
+++ b/cli/__tests__/adapters.codex.test.mjs
@@ -134,6 +134,20 @@ describe('codex adapter — detect()', () => {
 });
 
 describe('codex adapter — spawn()', () => {
+  test('an aborted signal before the child is created spawns nothing', async () => {
+    const { impl, calls } = makeSpawnImpl({ outputContents: 'ok' });
+    const controller = new AbortController();
+    const reason = new Error('stalled during preparation');
+    controller.abort(reason);
+    await expect(codex.spawn('hi', {
+      environment: { model: 'test-model' },
+      sessionId: null,
+      signal: controller.signal,
+      _spawnImpl: impl,
+    })).rejects.toBe(reason);
+    expect(calls).toHaveLength(0);
+  });
+
   test('BYO without fleet opt-in retains the CLI default on fresh and resumed turns', async () => {
     const prior = process.env.COMMONLY_REQUIRE_SEAT_MODEL;
     delete process.env.COMMONLY_REQUIRE_SEAT_MODEL;
diff --git a/cli/__tests__/supervise-runs-flag.test.mjs b/cli/__tests__/supervise-runs-flag.test.mjs
index c1e16a87cc..0ca1e2d0c1 100644
--- a/cli/__tests__/supervise-runs-flag.test.mjs
+++ b/cli/__tests__/supervise-runs-flag.test.mjs
@@ -41,7 +41,7 @@ await jest.unstable_mockModule('../src/lib/pod-focus.js', () => ({
 }));
 
 const { createClient } = await import('../src/lib/api.js');
-const { performRun } = await import('../src/commands/agent.js');
+const { performRun, superviseRunsByDefault } = await import('../src/commands/agent.js');
 const stubAdapter = (await import('../src/lib/adapters/stub.js')).default;
 
 const drain = async (depth = 40) => {
@@ -274,13 +274,34 @@ const filesUnder = (dir) => {
   return found;
 };
 
-describe('COMMONLY_SUPERVISE_RUNS=1 with the real codex adapter', () => {
+describe('superviseRunsByDefault: codex on by default, others only on =1', () => {
+  test.each([
+    ['codex', undefined, true],
+    ['codex', '1', true],
+    ['codex', '0', false],
+    ['codex', 'true', true],
+    ['claude', undefined, false],
+    ['claude', '1', true],
+    ['claude', '0', false],
+    ['stub', undefined, false],
+    ['stub', '', false],
+    [undefined, undefined, false],
+  ])('adapter %s with COMMONLY_SUPERVISE_RUNS=%s -> %s', (adapterName, value, expected) => {
+    const env = value === undefined ? {} : { COMMONLY_SUPERVISE_RUNS: value };
+    expect(superviseRunsByDefault(adapterName, env)).toBe(expected);
+  });
+});
+
+describe('COMMONLY_SUPERVISE_RUNS with the real codex adapter', () => {
   // Each turn spawns a real child and makes real loopback calls; under a
   // parallel suite on a loaded host that takes longer than jest's 5 s default.
   jest.setTimeout(60_000);
   const TURN_KEY = 'sk-turn-run-loop-4c1d9e7a';
 
-  test('a clean reply is posted, the metric line says supervised and delivered, and nothing else reaches disk', async () => {
+  test.each([
+    ['unset (codex default)', undefined],
+    ['=1', '1'],
+  ])('flag %s: a clean reply is posted, the metric line says supervised and delivered, and nothing else reaches disk', async (_label, flag) => {
     const { startFakeProvider } = await import('../../packages/seats/test-support/fake-provider.js');
     const codex = (await import('../src/lib/adapters/codex.js')).default;
     const provider = await startFakeProvider({ defaultReply: 'review: PASS' });
@@ -294,14 +315,15 @@ describe('COMMONLY_SUPERVISE_RUNS=1 with the real codex adapter', () => {
     fs.writeFileSync(path.join(bin, 'codex'), STUB_CODEX, { mode: 0o755 });
     const workspace = fs.mkdtempSync(path.join(home, 'ws-'));
     const env = {
-      COMMONLY_SUPERVISE_RUNS: '1',
       CODEX_HOME: codexHome,
       FAKE_PROVIDER_KEY: TURN_KEY,
       STUB_CODEX_DIRECT_BASE: provider.baseURL,
       PATH: `${bin}${path.delimiter}${path.dirname(process.execPath)}${path.delimiter}${process.env.PATH}`,
     };
     // The env must stay set while the turn runs: the adapter reads it at spawn.
-    const saved = Object.fromEntries(Object.keys(env).map((k) => [k, process.env[k]]));
+    const saved = Object.fromEntries(['COMMONLY_SUPERVISE_RUNS', ...Object.keys(env)].map((k) => [k, process.env[k]]));
+    delete process.env.COMMONLY_SUPERVISE_RUNS;
+    if (flag !== undefined) process.env.COMMONLY_SUPERVISE_RUNS = flag;
     Object.assign(process.env, env);
     try {
       const run = harness({
diff --git a/cli/src/commands/agent.js b/cli/src/commands/agent.js
index 209da246c5..091a5d0e82 100644
--- a/cli/src/commands/agent.js
+++ b/cli/src/commands/agent.js
@@ -1386,6 +1386,15 @@ const extractPrompt = (event) => {
 // cancel grace, and the wall-clock backstop past the adapter's own timeout.
 export { supervisedRunPolicy };
 
+// Codex turns are supervised by default (D211): a turn that stops making
+// progress is named and killed instead of holding the seat. COMMONLY_SUPERVISE_RUNS=0
+// opts out. Every other adapter stays off unless COMMONLY_SUPERVISE_RUNS=1.
+export const superviseRunsByDefault = (adapterName, env = process.env) => {
+  if (env.COMMONLY_SUPERVISE_RUNS === '0') return false;
+  if (adapterName === 'codex') return true;
+  return env.COMMONLY_SUPERVISE_RUNS === '1';
+};
+
 /**
  * Start the run loop. Polls /events, spawns the adapter per event, posts the
  * result into the pod, acks.
@@ -1461,14 +1470,15 @@ export const performRun = ({
   resolveOwnProviderKey = null,
   runtimeReportClient = null,
   refusalHandoff = null,
-  // Off unless COMMONLY_SUPERVISE_RUNS=1: each spawn runs under the seats
-  // supervisor (stall window, wall-clock backstop, a named failure on every
-  // settle). The CLI still talks to its provider directly, and one metadata
-  // line per turn goes to ~/.commonly/state/turns/<agent>.jsonl once
-  // delivery settles. Off, the spawn path is the plain adapter call it has
-  // always been, and nothing is written.
-  superviseRuns = process.env.COMMONLY_SUPERVISE_RUNS === '1',
+  // Each spawn runs under the seats supervisor (stall window, wall-clock
+  // backstop, a named failure on every settle) when superviseRuns is true.
+  // Unset, the default comes from superviseRunsByDefault. The CLI still talks
+  // to its provider directly, and one metadata line per turn goes to
+  // ~/.commonly/state/turns/<agent>.jsonl once delivery settles. Off, the spawn
+  // path is the plain adapter call it has always been, and nothing is written.
+  superviseRuns,
 }) => {
+  const supervising = superviseRuns ?? superviseRunsByDefault(adapter?.name);
   reportRuntime = reportRuntime && WALKED_HARNESSES.includes(adapter?.name);
   if (environment?.provider !== undefined && !adapter?.supportsProvider) {
     throw new Error('environment.provider requires a provider-capable adapter');
@@ -1480,9 +1490,9 @@ export const performRun = ({
   // The supervised run keeps its trace in memory, metadata only; no record of
   // a run is written to disk (lib/supervised-turn.js).
   const turnRunner = createTurnRunner({
-    seat: agentName, turnTimeoutMs: effectiveTurnTimeoutMs, supervise: superviseRuns, log,
+    seat: agentName, turnTimeoutMs: effectiveTurnTimeoutMs, supervise: supervising, log,
   });
-  if (superviseRuns) log(turnRunner.describe(adapter?.name));
+  if (supervising) log(turnRunner.describe(adapter?.name));
   const runtimeReporter = createRuntimeReporter({
     client: runtimeReportClient || { post: async () => {} },
     harness: adapter.name, detect: () => adapter.detect(),
@@ -1895,7 +1905,7 @@ export const performRun = ({
 
   // The spawn → post-decision half of a turn, split out so the claim release
   // above is a plain finally instead of threading through every return path.
-  // With superviseRuns, the turn's log line is written once delivery has
+  // With supervising, the turn's log line is written once delivery has
   // settled; anything thrown after a spawn that resolved means the reply never
   // reached the pod. Off, `turn` writes nothing.
   const runTurn = async (args) => {
diff --git a/cli/src/lib/adapters/codex.js b/cli/src/lib/adapters/codex.js
index 4ae97d260e..b6cc54930d 100644
--- a/cli/src/lib/adapters/codex.js
+++ b/cli/src/lib/adapters/codex.js
@@ -897,6 +897,13 @@ export default {
         await writePublicCodexInstructions(childEnv.CODEX_HOME, ctx);
       }
 
+      // The awaits above can outlast a supervisor stall window. Once it has
+      // aborted, the attempt has already settled and a retry may be running,
+      // so no process is created for this one. Checked synchronously before
+      // runCodex, so the spawn itself cannot race the abort.
+      if (ctx.signal?.aborted) {
+        throw ctx.signal.reason || new Error('codex spawn cancelled before the process started');
+      }
       const { threadId } = await runCodex({
         args,
         cwd: ctx.cwd,
diff --git a/cli/src/lib/supervised-turn.js b/cli/src/lib/supervised-turn.js
index 651286a34b..420f0fb126 100644
--- a/cli/src/lib/supervised-turn.js
+++ b/cli/src/lib/supervised-turn.js
@@ -3,7 +3,8 @@
  * path also writes one metadata line per turn (the turn log), once the
  * turn's outcome has reached the pod or failed to.
  *
- *   COMMONLY_SUPERVISE_RUNS=1  (read by performRun as `superviseRuns`)
+ *   codex by default, or COMMONLY_SUPERVISE_RUNS=1 (superviseRunsByDefault in
+ *     commands/agent.js; COMMONLY_SUPERVISE_RUNS=0 opts codex out)
  *     the turn runs under `superviseRun` from @commonlyai/seats: a stall
  *     window, a wall-clock backstop, and a guarantee the turn settles with a
  *     named failure. No provider relay: the CLI talks to its provider directly,