[MODEL] Agent briefs/replies refused by the user's own hook: FAKE REPLY (1 on one day)

Preflight Checklist

• [x] I have searched existing issues for similar behavior reports
• [x] This report does NOT contain sensitive information (API keys, passwords, etc.)

Type of Behavior Issue

Claude ignored my instructions or configuration

What You Asked Claude to Do

Standing project instructions and a user-written hook set rules for how agents brief, message, stop and report. This report covers one refusal type, FAKE REPLY. Count for the day: 1; actors: a Google Flow trailer worker.

What Claude Actually Did

A worker replied to an agent using a responseId that the hook found it had never been sent in that session (the id was truncated or invented).

Expected Behavior

Copy the full responseId from the incoming message when replying.

Files Affected

None. Agent messages and tool calls only.

Permission Mode

Accept Edits was ON (auto-accepting changes)

Can You Reproduce This?

Sometimes (intermittent)

Steps to Reproduce

Not a deterministic repro. The sequence is in the record above; the underlying logs are on the reporter's machine and can be summarised on request.

Claude Model

Sonnet

Relevant Conversation

See "What Claude Actually Did". Quotes are limited to the agents' own tool results and messages.

Impact

Medium - Extra work to undo changes

Claude Code Version

2.1.289 (as recorded in the agent session logs; the claude on PATH reports 2.1.220)

Platform

Other

Additional Context

This is one of 19 refusal types from the same day; the summary ticket links all of them. The hook is user-written and is not part of the product; the behaviour reported is what the agents sent into it.
Single-day record, 2026-10-06, all times US Eastern (Windows 11), a multi-agent session driven through a third-party agent harness; API platform is unverified. Reported as behaviour, not as a claim that Claude Code is defective.