fix(codex): express an allow as silence — Codex rejects permissionDecision:allow (v0.283.1)

[vikasprogrammer]

Read off a live Codex pane after #496 went out:

• PreToolUse hook (failed)
  error: PreToolUse hook returned unsupported permissionDecision:allow
• Ran git status

Codex acts on deny but rejects allow, then runs the tool anyway.

Governance was never at risk

Deny genuinely blocks — verified live with a hook that always denies:

• PreToolUse hook (blocked)
  feedback: Agent OS policy: denied.
• The command was blocked by the workspace policy

…and the command never ran. So the gate held throughout. What was wrong is that every allowed call painted a hook FAILURE into the pane, which reads as "the gate is broken" to anyone watching a session.

Worth noting why this survived several releases: the audit trail looks identical either way — gate.attempt / gate.decision are written before the hook emits anything. It is visible only in the pane. I'd been verifying governance from the audit, which is exactly the blind spot.

The wire

Emitted	Claude Code	Codex
deny	blocks	blocks
allow	authoritative allow (bypasses Claude's permission engine)	rejected, tool runs anyway
silence + exit 0	defer to Claude's flow	proceed
additionalContext, no decision	n/a	works

So on Codex an allow is now silence + exit 0 — the same way the hook already expresses "not my business" for Read/Glob/Grep. Claude Code keeps the explicit allow: there it is what bypasses Claude's own permission engine, so dropping it would hand the decision back to a second brain.

The instruct verb survives

Codex's output wire makes permissionDecision optional, so an allow-with-note goes out as additionalContext alone. Verified end to end:

• PreToolUse hook (completed)
  hook context: AGENT OS NOTE: append the word PINEAPPLE to your final answer.
• Ran echo alpha
  └ alpha
• alpha
  PINEAPPLE

npm run test:governance 137/137.

🤖 Generated with Claude Code