diff --git a/test/helpers/touchfiles.ts b/test/helpers/touchfiles.ts
index 79eed956..e0c6ebcf 100644
--- a/test/helpers/touchfiles.ts
+++ b/test/helpers/touchfiles.ts
@@ -105,6 +105,12 @@ export const E2E_TOUCHFILES: Record<string, string[]> = {
   // skills with no prior plan-mode test:
   'autoplan-auto-mode':           ['autoplan/**', 'plan-ceo-review/**', 'plan-design-review/**', 'plan-eng-review/**', 'plan-devex-review/**', 'scripts/resolvers/preamble/generate-completion-status.ts', 'scripts/resolvers/question-tuning.ts', 'scripts/resolvers/preamble/generate-ask-user-format.ts', 'scripts/resolvers/preamble.ts', 'test/helpers/claude-pty-runner.ts'],
   'office-hours-auto-mode':       ['office-hours/**', 'scripts/resolvers/preamble/generate-completion-status.ts', 'scripts/resolvers/question-tuning.ts', 'scripts/resolvers/preamble/generate-ask-user-format.ts', 'scripts/resolvers/preamble.ts', 'test/helpers/claude-pty-runner.ts'],
+  // v1.21+ AUTO_DECIDE preserve eval (periodic). Verifies the Tool resolution
+  // fix doesn't trip the legitimate /plan-tune opt-in path: when the user has
+  // written a never-ask preference, AUQ should still auto-decide rather than
+  // surfacing the question. Touches the question-tuning + preference
+  // infrastructure plus the resolvers that own the AUTO_DECIDE preamble.
+  'auto-decide-preserved':        ['scripts/resolvers/question-tuning.ts', 'scripts/resolvers/preamble/generate-ask-user-format.ts', 'scripts/resolvers/preamble/generate-completion-status.ts', 'plan-ceo-review/**', 'bin/gstack-question-preference', 'bin/gstack-config', 'bin/gstack-slug', 'test/helpers/claude-pty-runner.ts'],
 
   // Real-PTY E2E batch (#6 new tests on the harness).
   // Each one tests behavior the SDK harness can't observe (rendered TTY,
@@ -385,6 +391,7 @@ export const E2E_TIERS: Record<string, 'gate' | 'periodic'> = {
   // v1.21+ auto-mode regression tests
   'autoplan-auto-mode': 'gate',
   'office-hours-auto-mode': 'gate',
+  'auto-decide-preserved': 'periodic',
   'e2e-harness-audit': 'gate',
 
   // Real-PTY E2E batch — tier classification:
diff --git a/test/skill-e2e-auto-decide-preserved.test.ts b/test/skill-e2e-auto-decide-preserved.test.ts
new file mode 100644
index 00000000..8b773d5f
--- /dev/null
+++ b/test/skill-e2e-auto-decide-preserved.test.ts
@@ -0,0 +1,131 @@
+/**
+ * AUTO_DECIDE opt-in preserved under Conductor flags (periodic-tier, paid, real-PTY).
+ *
+ * Regression test for v1.21+ fix: the new "Tool resolution" preamble
+ * (scripts/resolvers/preamble/generate-ask-user-format.ts) tells the model
+ * to prefer mcp__*__AskUserQuestion variants and fall back to plan-file
+ * decisions when neither is callable. This must NOT break the legitimate
+ * `/plan-tune` AUTO_DECIDE path: when the user has explicitly opted into
+ * auto-deciding a specific question via `gstack-question-preference --write
+ * never-ask`, the model is supposed to honor that — it should still
+ * auto-pick the recommended option and emit the AUTO_DECIDE annotation
+ * ("Auto-decided <summary> → <option> (your preference). Change with
+ * /plan-tune.") instead of opening a question prompt.
+ *
+ * Periodic tier: AUTO_DECIDE behavior depends on the model adhering to
+ * the QUESTION_TUNING preamble injection. Non-deterministic; runs weekly
+ * or manually rather than gating CI.
+ *
+ * Set up:
+ *   - tmpDir as GSTACK_HOME (isolated state, doesn't touch the user's
+ *     real ~/.gstack)
+ *   - question_tuning=true in the tmp config
+ *   - preference for plan-ceo-review-mode → never-ask (source: plan-tune)
+ *
+ * Spawn:
+ *   claude --permission-mode plan --disallowedTools AskUserQuestion
+ *   /plan-ceo-review
+ *
+ * Expected:
+ *   - outcome === 'auto_decided' (the AUTO_DECIDE preamble fired and the
+ *     "Auto-decided ... (your preference)" text rendered)
+ *
+ * If outcome is 'asked', the model ignored the user's `/plan-tune`
+ * preference — that's a regression against the opt-in feature. If outcome
+ * is 'plan_ready' with no AUTO_DECIDE text, the model auto-decided BUT
+ * skipped the annotation (acceptable; AUTO_DECIDE annotation is good
+ * practice but not the load-bearing behavior).
+ */
+
+import { describe, test, expect } from 'bun:test';
+import { runPlanSkillObservation } from './helpers/claude-pty-runner';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { spawnSync } from 'child_process';
+
+const shouldRun = !!process.env.EVALS && process.env.EVALS_TIER === 'periodic';
+const describeE2E = shouldRun ? describe : describe.skip;
+
+const ROOT = path.resolve(import.meta.dir, '..');
+
+describeE2E('AUTO_DECIDE opt-in preserved under Conductor flags (periodic)', () => {
+  test('user-opted-in question still auto-decides when AskUserQuestion is --disallowedTools', async () => {
+    const tmpHome = fs.mkdtempSync(path.join(os.tmpdir(), 'gstack-auto-decide-'));
+    try {
+      // 1. Bootstrap the tmp GSTACK_HOME with question_tuning=true.
+      const configBin = path.join(ROOT, 'bin', 'gstack-config');
+      const setRes = spawnSync(configBin, ['set', 'question_tuning', 'true'], {
+        env: { ...process.env, GSTACK_HOME: tmpHome },
+        encoding: 'utf-8',
+      });
+      if (setRes.status !== 0) {
+        throw new Error(`gstack-config set failed: ${setRes.stderr || setRes.stdout}`);
+      }
+
+      // 2. Resolve slug for the project (uses git remote — same as the spawned
+      //    claude would resolve). The preference file path keys on this slug.
+      const slugBin = path.join(ROOT, 'bin', 'gstack-slug');
+      const slugRes = spawnSync(slugBin, [], {
+        cwd: ROOT,
+        env: { ...process.env, GSTACK_HOME: tmpHome },
+        encoding: 'utf-8',
+      });
+      // gstack-slug emits `eval`-able shell exports like `SLUG=garrytan-gstack`.
+      const slug = (slugRes.stdout.match(/SLUG=([^\s;]+)/)?.[1] ?? 'unknown').replace(/['"]/g, '');
+
+      // 3. Write the preference: plan-ceo-review-mode → never-ask. The
+      //    'plan-tune' source bypasses the inline-user origin gate.
+      const prefBin = path.join(ROOT, 'bin', 'gstack-question-preference');
+      const writeRes = spawnSync(
+        prefBin,
+        ['--write', JSON.stringify({
+          question_id: 'plan-ceo-review-mode',
+          preference: 'never-ask',
+          source: 'plan-tune',
+        })],
+        {
+          env: { ...process.env, GSTACK_HOME: tmpHome },
+          encoding: 'utf-8',
+        },
+      );
+      if (writeRes.status !== 0) {
+        throw new Error(`gstack-question-preference --write failed: ${writeRes.stderr || writeRes.stdout}`);
+      }
+
+      // Sanity: the preference file landed where we expect.
+      const prefFile = path.join(tmpHome, 'projects', slug, 'question-preferences.json');
+      if (!fs.existsSync(prefFile)) {
+        throw new Error(`expected preference file at ${prefFile}; not found. slug=${slug}`);
+      }
+
+      // 4. Run /plan-ceo-review with the Conductor flag set + isolated state.
+      const obs = await runPlanSkillObservation({
+        skillName: 'plan-ceo-review',
+        inPlanMode: true,
+        extraArgs: ['--disallowedTools', 'AskUserQuestion'],
+        timeoutMs: 300_000,
+      });
+
+      // 5. Pass: 'auto_decided' (the strongest signal) or 'plan_ready' with
+      //    no question rendered. Fail: 'asked' (model ignored the opt-in).
+      if (obs.outcome === 'asked') {
+        throw new Error(
+          `AUTO_DECIDE regression: the model surfaced an AskUserQuestion despite the user's never-ask preference.\n` +
+            `summary: ${obs.summary}\n` +
+            `--- evidence (last 2KB visible) ---\n${obs.evidence}`,
+        );
+      }
+      if (obs.outcome === 'silent_write' || obs.outcome === 'exited' || obs.outcome === 'timeout') {
+        throw new Error(
+          `AUTO_DECIDE preserve test inconclusive: outcome=${obs.outcome}\n` +
+            `summary: ${obs.summary}\n` +
+            `--- evidence (last 2KB visible) ---\n${obs.evidence}`,
+        );
+      }
+      expect(['auto_decided', 'plan_ready']).toContain(obs.outcome);
+    } finally {
+      try { fs.rmSync(tmpHome, { recursive: true, force: true }); } catch { /* best-effort */ }
+    }
+  }, 360_000);
+});
diff --git a/test/touchfiles.test.ts b/test/touchfiles.test.ts
index 1135fe61..ff7f018e 100644
--- a/test/touchfiles.test.ts
+++ b/test/touchfiles.test.ts
@@ -97,10 +97,12 @@ describe('selectTests', () => {
     expect(result.selected).toContain('ask-user-question-format-pty');
     expect(result.selected).toContain('plan-ceo-mode-routing');
     expect(result.selected).toContain('autoplan-chain-pty');
-    // v1.21+ auto-mode regression: autoplan-auto-mode also depends on plan-ceo-review/**
+    // v1.21+ regression: autoplan-auto-mode + auto-decide-preserved also
+    // depend on plan-ceo-review/**
     expect(result.selected).toContain('autoplan-auto-mode');
-    expect(result.selected.length).toBe(19);
-    expect(result.skipped.length).toBe(Object.keys(E2E_TOUCHFILES).length - 19);
+    expect(result.selected).toContain('auto-decide-preserved');
+    expect(result.selected.length).toBe(20);
+    expect(result.skipped.length).toBe(Object.keys(E2E_TOUCHFILES).length - 20);
   });
 
   test('global touchfile triggers ALL tests', () => {