[BUG] Plan mode ignores CLAUDE.md instructions for plan file naming

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?

When entering plan mode, Claude Code generates random quirky plan filenames (e.g., magical-imagining-harp.md) instead of respecting user instructions in CLAUDE.md.

CLAUDE.md instruction:
## Plan Mode

• Use descriptive plan filenames. Name plan files clearly based on what the plan is about. No random or quirky names.

Expected behavior: Plan file should be named based on content, e.g., ibkr-history-download-improvements.md

Actual behavior: Plan file was named magical-imagining-harp.md (random words)

Impact: CLAUDE.md is documented as the way to customize Claude Code behavior, but built-in defaults override user instructions for plan naming. This undermines trust in CLAUDE.md as a configuration mechanism.

Suggested fix: Before generating a plan filename, check CLAUDE.md for naming instructions and follow them.

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What Should Happen?

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Error Messages/Logs

Steps to Reproduce

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Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

latest

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Jezus this form is tedious as hell