diff --git a/hosts/claude/hooks/auq-error-fallback-hook.ts b/hosts/claude/hooks/auq-error-fallback-hook.ts
index be0900830..502c9d486 100755
--- a/hosts/claude/hooks/auq-error-fallback-hook.ts
+++ b/hosts/claude/hooks/auq-error-fallback-hook.ts
@@ -98,20 +98,25 @@ export function isErrorResponse(response: unknown): boolean {
   if (typeof response === 'string') {
     const s = response.trim();
     if (s === '') return true;
-    return /tool result missing|internal error|\bis_error\b/i.test(s);
+    // Match ONLY the specific missing-result sentinel phrase, not any string that
+    // merely contains "error" — a real answer like "Investigate the internal error"
+    // must NOT trigger the fallback. (Codex review finding.)
+    return /tool result missing/i.test(s);
   }
   if (typeof response === 'object') {
     const rec = response as Record<string, unknown>;
-    if (rec.is_error === true || rec.isError === true || rec.error) return true;
+    // Structured flag must be the boolean true — not the substring "is_error" inside
+    // a serialized success payload like '{"is_error": false}'.
+    if (rec.is_error === true || rec.isError === true) return true;
+    if (typeof rec.error === 'string' && rec.error.trim() !== '') return true;
     // Some hosts wrap the payload as { content: "..." } or { content: [{text}] }.
     const content = rec.content;
-    if (typeof content === 'string') return isErrorResponse(content);
+    if (typeof content === 'string') return /tool result missing/i.test(content);
     if (Array.isArray(content)) {
       const text = content
         .map((c) => (typeof c === 'string' ? c : (c as Record<string, unknown>)?.text ?? ''))
         .join(' ');
-      if (text.trim() === '') return false; // empty content array on success is ambiguous; don't trigger
-      return /tool result missing|internal error/i.test(text);
+      return /tool result missing/i.test(text);
     }
   }
   return false;
diff --git a/package.json b/package.json
index a9440ba15..e1fb1cf70 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "gstack",
-  "version": "1.57.0.0",
+  "version": "1.57.2.0",
   "description": "Garry's Stack — Claude Code skills + fast headless browser. One repo, one install, entire AI engineering workflow.",
   "license": "MIT",
   "type": "module",
@@ -20,16 +20,16 @@
     "test": "bun test browse/test/ test/ make-pdf/test/ --ignore 'test/skill-e2e-*.test.ts' --ignore test/skill-llm-eval.test.ts --ignore test/skill-routing-e2e.test.ts --ignore test/codex-e2e.test.ts --ignore test/gemini-e2e.test.ts && (bun run slop:diff 2>/dev/null || true)",
     "test:free": "bun run scripts/test-free-shards.ts",
     "test:windows": "bun run scripts/test-free-shards.ts --windows-only",
-    "test:evals": "EVALS=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-llm-eval.test.ts test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
-    "test:evals:all": "EVALS=1 EVALS_ALL=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-llm-eval.test.ts test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
-    "test:e2e": "EVALS=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
-    "test:e2e:all": "EVALS=1 EVALS_ALL=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
-    "test:gate": "EVALS=1 EVALS_TIER=gate bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-llm-eval.test.ts test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
-    "test:periodic": "EVALS=1 EVALS_TIER=periodic EVALS_ALL=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
-    "test:codex": "EVALS=1 bun test test/codex-e2e.test.ts",
-    "test:codex:all": "EVALS=1 EVALS_ALL=1 bun test test/codex-e2e.test.ts",
-    "test:gemini": "EVALS=1 bun test test/gemini-e2e.test.ts",
-    "test:gemini:all": "EVALS=1 EVALS_ALL=1 bun test test/gemini-e2e.test.ts",
+    "test:evals": "EVALS=1 GSTACK_HEADLESS=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-llm-eval.test.ts test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
+    "test:evals:all": "EVALS=1 GSTACK_HEADLESS=1 EVALS_ALL=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-llm-eval.test.ts test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
+    "test:e2e": "EVALS=1 GSTACK_HEADLESS=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
+    "test:e2e:all": "EVALS=1 GSTACK_HEADLESS=1 EVALS_ALL=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
+    "test:gate": "EVALS=1 GSTACK_HEADLESS=1 EVALS_TIER=gate bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-llm-eval.test.ts test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
+    "test:periodic": "EVALS=1 GSTACK_HEADLESS=1 EVALS_TIER=periodic EVALS_ALL=1 bun test --retry 2 --concurrent --max-concurrency ${EVALS_CONCURRENCY:-15} test/skill-e2e-*.test.ts test/skill-routing-e2e.test.ts test/codex-e2e.test.ts test/gemini-e2e.test.ts",
+    "test:codex": "EVALS=1 GSTACK_HEADLESS=1 bun test test/codex-e2e.test.ts",
+    "test:codex:all": "EVALS=1 GSTACK_HEADLESS=1 EVALS_ALL=1 bun test test/codex-e2e.test.ts",
+    "test:gemini": "EVALS=1 GSTACK_HEADLESS=1 bun test test/gemini-e2e.test.ts",
+    "test:gemini:all": "EVALS=1 GSTACK_HEADLESS=1 EVALS_ALL=1 bun test test/gemini-e2e.test.ts",
     "skill:check": "bun run scripts/skill-check.ts",
     "dev:skill": "bun run scripts/dev-skill.ts",
     "start": "bun run browse/src/server.ts",
diff --git a/setup b/setup
index 1fce574ce..0c180f7bf 100755
--- a/setup
+++ b/setup
@@ -1325,9 +1325,13 @@ if [ "$NO_TEAM_MODE" -ne 1 ] \
    && [ -x "$PLAN_TUNE_LOG_HOOK" ] \
    && [ -x "$PLAN_TUNE_PREF_HOOK" ]; then
 
-  # Already installed? Check the settings.json for our source tag.
+  # Already installed? Require BOTH the plan-tune source AND the AUQ-error-fallback
+  # source — so an existing install that predates the fallback hook re-runs the
+  # install (which is idempotent for the plan-tune hooks) and picks up the new one.
   ALREADY_INSTALLED=0
-  if "$SETTINGS_HOOK" list-sources 2>/dev/null | grep -q "plan-tune-cathedral"; then
+  _HOOK_SOURCES=$("$SETTINGS_HOOK" list-sources 2>/dev/null || true)
+  if printf '%s' "$_HOOK_SOURCES" | grep -q "plan-tune-cathedral" \
+     && printf '%s' "$_HOOK_SOURCES" | grep -q "auq-error-fallback"; then
     ALREADY_INSTALLED=1
   fi
 
@@ -1365,15 +1369,19 @@ if [ "$NO_TEAM_MODE" -ne 1 ] \
       --command "$PLAN_TUNE_PREF_HOOK" \
       --source plan-tune-cathedral \
       --timeout 5
-    # AUQ-failure prose-fallback reliability hook (OV3:B). Fires only when an
-    # AskUserQuestion call returns an error/missing result; inert on success and
-    # inert if the platform doesn't invoke PostToolUse on tool errors.
+    # AskUserQuestion-failure prose-fallback reliability hook (OV3:B). Fires only when
+    # an AskUserQuestion call returns an error/missing result; inert on success and
+    # inert if the platform doesn't invoke PostToolUse on tool errors. MUST use its
+    # OWN source tag: gstack-settings-hook dedupes by (event, matcher, source) and
+    # REPLACES the entry's hooks, so sharing 'plan-tune-cathedral' would overwrite the
+    # question-log capture hook (same event+matcher). A distinct source = a second
+    # PostToolUse entry; both run in parallel.
     if [ -x "$AUQ_ERROR_FALLBACK_HOOK" ]; then
       "$SETTINGS_HOOK" add-event \
         --event PostToolUse \
         --matcher '(AskUserQuestion|mcp__.*__AskUserQuestion)' \
         --command "$AUQ_ERROR_FALLBACK_HOOK" \
-        --source plan-tune-cathedral \
+        --source auq-error-fallback \
         --timeout 5
     fi
   }
diff --git a/test/auq-error-fallback-hook.test.ts b/test/auq-error-fallback-hook.test.ts
index 48a996edb..ee6d317f5 100644
--- a/test/auq-error-fallback-hook.test.ts
+++ b/test/auq-error-fallback-hook.test.ts
@@ -32,20 +32,29 @@ describe('isErrorResponse — only clear failures, never a real answer', () => {
     expect(isErrorResponse('[Tool result missing due to internal error]')).toBe(true);
   });
 
-  test('is_error / error object shapes are failures', () => {
+  test('is_error: true / error-field / sentinel-in-content are failures', () => {
     expect(isErrorResponse({ is_error: true })).toBe(true);
     expect(isErrorResponse({ isError: true })).toBe(true);
     expect(isErrorResponse({ error: 'boom' })).toBe(true);
-    expect(isErrorResponse({ content: '...internal error...' })).toBe(true);
+    expect(isErrorResponse({ content: 'Tool result missing due to internal error' })).toBe(true);
   });
 
   test('a real answer is NOT a failure (no false trigger)', () => {
     expect(isErrorResponse({ answers: [{ option_label: 'A' }] })).toBe(false);
     expect(isErrorResponse('A')).toBe(false);
-    // a choice that coincidentally contains the word "error" must not trip it
+    // a choice that coincidentally contains "error" must not trip it
     expect(isErrorResponse({ answers: [{ option_label: 'Fix the error' }] })).toBe(false);
     expect(isErrorResponse('Investigate the login error')).toBe(false);
   });
+
+  test('Codex review: narrow detection — generic "error"/"is_error" substrings do NOT trigger', () => {
+    // A real answer mentioning "internal error" must not be read as a failure.
+    expect(isErrorResponse('Investigate the internal error')).toBe(false);
+    // A serialized success payload containing the substring is_error:false must not trigger.
+    expect(isErrorResponse('{"is_error": false, "answer": "A"}')).toBe(false);
+    expect(isErrorResponse({ is_error: false })).toBe(false);
+    expect(isErrorResponse({ content: 'The page had an internal error we fixed' })).toBe(false);
+  });
 });
 
 describe('directiveFor — per-session-kind instruction', () => {
diff --git a/test/helpers/agent-sdk-runner.ts b/test/helpers/agent-sdk-runner.ts
index c35585438..fc50f7884 100644
--- a/test/helpers/agent-sdk-runner.ts
+++ b/test/helpers/agent-sdk-runner.ts
@@ -300,13 +300,12 @@ export async function runAgentSdkTest(
   const queryImpl: QueryProvider = opts.queryProvider ?? query;
   const model = opts.model ?? 'claude-opus-4-7';
 
-  // Default GSTACK_HEADLESS=1 so SDK-driven eval/E2E runs classify as headless: an
-  // AskUserQuestion failure BLOCKs instead of emitting a prose question no human can
-  // answer. Set ambiently (the SDK child inherits process.env) rather than via
-  // sdkOpts.env — passing an env object to the SDK breaks its auth pipeline (see
-  // CLAUDE.md). A suite testing the interactive prose-fallback path sets
-  // process.env.GSTACK_HEADLESS='' before calling.
-  if (process.env.GSTACK_HEADLESS === undefined) process.env.GSTACK_HEADLESS = '1';
+  // NOTE on GSTACK_HEADLESS: the SDK child inherits process.env, so headless
+  // classification for eval/E2E runs is set by the `test:gate` / `test:evals`
+  // package.json scripts (scoped to that invocation), NOT mutated here. We must not
+  // pass sdkOpts.env (it breaks the SDK auth pipeline — see CLAUDE.md) and must not
+  // mutate process.env ambiently (it would leak headless into later interactive-path
+  // tests in the same Bun process — Codex review finding).
 
   let attempt = 0;
   let lastErr: unknown = null;