[BUG] Claude Code trusts subagent file-write reports without verifying files exist on disk

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Claude Code trusts the agent's text output as ground truth. This leads to:

• False confirmation of success to the user
• Blocking legitimate re-runs based on stale/false reported state
• No warning when files don't exist

What Should Happen?

After any subagent reports writing files, Claude Code should verify the files exist on disk before telling the user the operation succeeded and making decisions based on that reported state.

Error Messages/Logs

Steps to Reproduce

1. Run /plan --create <spec-path> using the tdd-l1-spec-generator plugin
2. The orchestrator subagent reports: "All 6 files written successfully" with file paths listed
3. Claude Code presents the plan as complete and ready
4. User deletes the plan folder (or it was never written)
5. Claude Code later blocks the user from re-running --create, saying "a fully finalized plan already exists at

plans/20260319-sub-intent-classifier"

1. No such directory exists on disk

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.76

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_