codex - 💡(How to fix) Fix project_doc_fallback_filenames=["CLAUDE.md"] does not inject project instructions, while AGENTS.md works [1 participants]

[project]
project_doc_fallback_filenames = ["CLAUDE.md"]

## What I Expected

If a repository does not contain AGENTS.md but does contain CLAUDE.md, then Codex should inject CLAUDE.md as the project instruction document.

## What Actually Happened

- CLAUDE.md was not injected into the model-visible prompt input.
- The session only contained the normal base/developer instructions.
- I had to manually open/read CLAUDE.md from the workspace.
- In contrast, when I created a test directory containing only AGENTS.md, Codex injected it correctly.

## Why this seems CLI-side, not provider-side

I verified this with:

codex debug prompt-input

This command shows the model-visible input list before the request is sent.

So if CLAUDE.md is missing there, the problem seems to happen in local prompt construction / project-doc discovery, before provider transport.



### What steps can reproduce the bug?

## Reproduction

### Case 1: AGENTS.md works

Create a temp directory with only AGENTS.md:

mkdir -p /tmp/codex-doc-test-agents
cp CLAUDE.md /tmp/codex-doc-test-agents/AGENTS.md
cd /tmp/codex-doc-test-agents
codex debug prompt-input

Actual result:

The output includes a block like:

# AGENTS.md instructions for /tmp/codex-doc-test-agents

So AGENTS.md is injected correctly.

### Case 2: CLAUDE.md fallback does not work

Create a temp directory with only CLAUDE.md:

mkdir -p /tmp/codex-doc-test-claude
cp CLAUDE.md /tmp/codex-doc-test-claude/CLAUDE.md
cd /tmp/codex-doc-test-claude
codex debug prompt-input

Actual result:

- No project instruction block is injected
- No CLAUDE.md content appears in prompt input

Expected result:

- CLAUDE.md should be injected because project_doc_fallback_filenames = ["CLAUDE.md"] is configured

## Additional Notes

This does not seem to be caused by /new vs restarting the TUI.

I tested with a fresh codex debug prompt-input process, and the behavior was the same:

- AGENTS.md loads
- CLAUDE.md fallback does not load

So this seems reproducible even in a fresh process.

### What is the expected behavior?

_No response_

### Additional information

_No response_