fix(plan-tune): stop deferring AskUserQuestion in non-interactive sessions

[mitch-schneider-1]

Summary

The AskUserQuestion PreToolUse hook emits permissionDecision: "defer" on its pass-through path — no preference set, no <gstack-qid:…> marker, i.e. the common case. This makes AskUserQuestion silently fail in every non-interactive host while working perfectly in the terminal.

Root cause

defer is an undocumented, print-mode-only value. The documented set is allow | deny | ask. From the Claude Code 2.1.216 binary:

- `permissionDecision` - "allow", "deny", or "ask" (PreToolUse only)
Hook … returned permissionDecision=defer in interactive mode; ignoring (defer is print-mode only)
Unknown hook permissionDecision type: … Valid types are: allow, deny, ask, defer

So:

Host	Behavior
Interactive terminal	Value parsed, warning logged, ignored → tool works
Non-interactive (Cowork, Agent SDK, claude -p)	Value honored → tool_use left unresolved, no result

In the non-interactive case the agent receives [Tool result missing due to internal error] and the question never reaches the user.

The failure mode is nasty precisely because it's mode-split: 100% broken in one host, 100% fine in another. That reads as flaky transport, so it gets misattributed to the platform rather than the hook. It also defeats the existing auq-error-fallback-hook mitigation, since a deferred tool never produces the error response that hook keys on.

Fix

Emit no permissionDecision on pass-through. Absence is the correct "no opinion" signal and the only form that is safe in both modes.

Unchanged:

• additionalContext (plan-tune memory injection) still emitted when present.
• The deny paths — never-ask auto-decide and the Conductor prose redirect — are untouched.

Also corrects docs/spikes/claude-code-hook-mutation.md, which documented defer as the pass-through shape. That's where the bug originated, so leaving it would re-seed the regression.

Testing

• 89 pass / 0 fail across the 7 AskUserQuestion hook test files.
• Updated 11 assertions across 3 test files that pinned the old defer contract; they now assert absence.
• Verified live: AskUserQuestion confirmed working in a Cowork session where it had consistently returned no result.
• The 5 skill-e2e-plan-tune-cathedral eval scenarios fail identically on main and on this branch (pre-existing, unrelated — per the repo's E2E blame protocol).

Health check — empty stdout is correct:

echo '{"hook_event_name":"PreToolUse","tool_name":"AskUserQuestion","tool_input":{"questions":[]}}' \
  | hosts/claude/hooks/question-preference-hook

🤖 Generated with Claude Code

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[mitch-schneider-1]

Closing as a duplicate — #2325 already covers this fix and touches the same files. I missed it before opening; apologies for the noise.

Leaving one note here in case it's useful to whoever picks #2325 up: the reason this reads as flaky transport rather than a hook bug is that defer is honored in print mode but ignored in interactive mode, so the same hook is 100% broken in Cowork / Agent SDK / claude -p and 100% fine in a terminal. From the Claude Code 2.1.216 binary:

- `permissionDecision` - "allow", "deny", or "ask" (PreToolUse only)
Hook … returned permissionDecision=defer in interactive mode; ignoring (defer is print-mode only)

Worth also fixing docs/spikes/claude-code-hook-mutation.md, which documents defer as the pass-through shape — that's where the bug originated, so it can re-seed.