v1.57.2.0 feat: AskUserQuestion prose fallback when the tool fails at runtime (#1908)

* feat(auq): add gstack-session-kind + echo SESSION_KIND in preamble

Classifies the session as spawned | headless | interactive from env markers
(OPENCLAW_SESSION / GSTACK_HEADLESS / CONDUCTOR_* / CLAUDE_CODE_ENTRYPOINT / CI),
defaulting to interactive. Echoed once at skill start alongside BRANCH/REPO_MODE
so the AskUserQuestion-failure fallback can branch without a shell-out at failure
time. Degrade-safe: empty/error => interactive.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* feat(auq): prose fallback when AskUserQuestion fails (interactive sessions)

On a genuine AUQ failure (tool absent, or present-but-erroring like Conductor's
flaky MCP returning '[Tool result missing due to internal error]'): retry once,
then branch on SESSION_KIND — spawned auto-chooses, headless BLOCKs, interactive
renders a prose decision brief the user answers by typing a letter.

The prose fallback MUST surface the triad: a clear ELI10 of the issue, a
per-choice Completeness score, and a recommendation+why (one paragraph per
choice). Carves out the [plan-tune auto-decide] denial as NOT a failure, and
qualifies the former 'tool_use, not prose' assertions so the rule isn't
self-contradicting. Tests pin the triad, the SESSION_KIND branch, the OV2
collision guard, the always-loaded guarantee, and a cross-file invariant on the
auto-decide prefix.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* test(auq): default GSTACK_HEADLESS=1 in eval/E2E runners

Headless harness runs classify as headless (BLOCK on AUQ failure rather than
emit a prose question no one reads). SDK runner uses ambient mutation, not the
Options.env object, to avoid breaking the SDK auth pipeline. Interactive-path
suites opt out by overriding the env per-run.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* feat(auq): defensive PostToolUse error-fallback hook (OV3:B)

When an AskUserQuestion call returns an error/missing result, this hook injects
additionalContext reminding the model to run the prose fallback for the current
SESSION_KIND. It does not render prose itself — it guarantees the reminder fires
at the moment of failure instead of relying on the model recalling SESSION_KIND.

Inert on success and inert if the platform never invokes PostToolUse on tool
errors (unverified — could not force the Conductor MCP error in a harness; see
the spike doc). The prompt-level fallback covers the case regardless. Decision
logic is unit-tested deterministically; registered in setup beside the existing
AUQ hooks.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore(auq): regenerate SKILL.md for all hosts + refresh ship goldens

Regenerated from the resolver changes (gen:skill-docs --host all). Refreshes the
byte-exact ship golden fixtures (claude/codex/factory). Spec prose tightened so
the cross-cutting preamble addition stays under the 5% per-skill parity ceiling
(investigate 4.8%) — guard unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(test): kebab testNames for section-loading E2Es to match TOUCHFILES keys

The two section-loading E2E tests used display-form testNames ('/ship
section-loading', '/plan-ceo-review section-loading') while every other E2E
testName and their E2E_TOUCHFILES keys are kebab. The completeness gate does an
exact `name in E2E_TOUCHFILES` check, so it failed (pre-existing on main); diff-
based selection also couldn't match them. Align to ship-section-loading /
plan-ceo-section-loading.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(test): make external-host freshness checks deterministic

The parameterized host smoke + --host all freshness tests assumed an external
`gen:skill-docs --host all` had run first (it never does in `bun test`), so which
host reported STALE varied by sibling-test timing — flaky. Regenerate the
gitignored external host dirs in a beforeAll so the --dry-run check is
deterministic. It still catches non-deterministic generation (the real bug class
for regenerated outputs); the tracked-claude freshness test runs earlier and is
unaffected.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* test(parity): headroom for AUQ cross-cutting addition on carved document-release

Merging main brought the carve of document-release (smaller skeleton); the AUQ
prose-fallback adds ~2KB to every skill's always-loaded preamble, landing
document-release at ~5.9% over the pre-carve v1.53.0.0 baseline. Add a per-carve
maxSizeRatio override (CARVE_GUARDS single source of truth) and bump only this
skill to 1.08. All other skills keep the strict 1.05 ceiling.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(auq): harden error-fallback hook + harness per adversarial review

Codex pre-landing review found three real issues:
- The PostToolUse fallback hook shared source 'plan-tune-cathedral' with the
  question-log hook (same event+matcher); gstack-settings-hook replaces the entry,
  so it would have clobbered plan-tune capture. Give it its own 'auq-error-fallback'
  source (separate entry, both run); ALREADY_INSTALLED now requires both sources.
- isErrorResponse triggered on any string containing 'internal error'/'is_error',
  so a real answer or a {"is_error": false} payload could fire the fallback after a
  successful question. Narrow it to the missing-result sentinel + boolean is_error.
- The SDK runner mutated process.env.GSTACK_HEADLESS process-wide (leaked headless
  into later tests). Removed; GSTACK_HEADLESS=1 now lives in the eval package.json
  scripts, scoped to the invocation and inherited by the SDK child.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore: bump version and changelog (v1.57.2.0)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/spikes/claude-code-hook-mutation.md

@@ -127,6 +127,38 @@ required for our hook to fire there.
 (PostToolUse hooks can also set `additionalContext` to append to the tool
 result; we don't need this for v1 capture.)
 
+## PostToolUse on tool error (AUQ-failure fallback, OV3:B) — UNVERIFIED
+
+The AUQ-failure prose fallback adds a defensive PostToolUse hook
+(`hosts/claude/hooks/auq-error-fallback-hook.ts`) that, when an AskUserQuestion
+call returns an error / missing result, injects `additionalContext` reminding the
+model to run the prose fallback per `SESSION_KIND`. It uses the same
+`additionalContext` mechanism documented above.
+
+**Open question we could NOT settle in a harness:** does Claude Code invoke
+PostToolUse hooks when an MCP tool call returns a transport/missing-result error
+(the Conductor bug surfaces `[Tool result missing due to internal error]`)? The
+docs above cover PostToolUse on *success*. We could not force the Conductor
+internal MCP failure on demand to observe it.
+
+**Decision (OV3:B = A):** build the hook defensively anyway.
+- It is **inert on success** (only fires when `isErrorResponse(tool_response)` is
+  true) and **inert if the platform never invokes it** on the error path.
+- The prompt-level fallback in `generate-ask-user-format.ts` covers the case
+  regardless — the hook is a reliability *layer*, not the mechanism.
+- Its decision logic is unit-tested deterministically
+  (`test/auq-error-fallback-hook.test.ts`): given a synthetic error `tool_response`
+  + each `SESSION_KIND`, it emits the correct directive; given a real answer it
+  defers.
+
+**Recommended manual / partial spike (to close the gap later):** register a
+throwaway PostToolUse hook that logs on fire, then (a) trigger a normal tool
+error (e.g. a failing `Bash` call) to confirm PostToolUse fires on tool errors at
+all, and (b) reproduce the Conductor MCP AUQ failure and check the log. If (b)
+confirms a fire, promote the hook from "defensive/inert" to "verified". Until
+then, treat the runtime layer as best-effort and the prompt-level fallback as the
+guaranteed path.
+
 ## Settings.json snippet for T8 hook installer
 
 ```json