codex_app.set_thread_title is exposed but refuses remote threads #26178

What happened?

In a Codex Desktop remote thread, the thread-management tool codex_app.set_thread_title is discoverable, but calling it for the current thread fails at runtime with:

Codex thread tools are only supported for local threads.

This is confusing because the current remote thread is visible in the Codex Desktop sidebar, and the agent can discover the rename tool plus a current thread id. A skill or agent trying to keep conversation titles tidy sees an apparently valid tool, calls it, then gets a runtime refusal.

Steps to reproduce

1. Open a Codex Desktop thread that runs in a remote environment.
2. From that thread, ask the agent/skill to rename the current conversation.
3. Discover thread tools via tool search; codex_app.set_thread_title is returned.
4. Call codex_app.set_thread_title with the current thread id and a new title.
5. Observe the runtime error above.

Expected behavior

Either:

• support renaming Desktop-visible remote-backed threads through codex_app.set_thread_title, or
• do not expose the rename tool to remote threads where it cannot work, or
• expose a clear capability/status signal so skills can skip the call and report a suggested title instead.

Actual behavior

The tool is discoverable and looks applicable, but refuses execution because the thread is not local.

Why this matters

This makes thread-title automation brittle in Codex Desktop remote threads. It also nudges skill authors toward unsafe fallback ideas such as editing local session index files directly, which is not a reliable or supported way to update Desktop thread metadata.

Related issues

These appear related to the same local/remote/Desktop thread metadata boundary, though they do not describe this exact error:

• Codex App remote project conversations disappear from local sidebar, but still exist on the remote server #25092
• Android Codex shows stale local project threads despite connected desktop until remote-control enrollment reset #24749
• Make Codex CLI sessions available in Codex desktop history #21079
• Codex Desktop: setting a goal fails after thread title generation without inserting thread_goals row #24282

Environment

• Product: Codex Desktop
• Thread type: remote-backed Desktop thread
• Tool: codex_app.set_thread_title
• Error: Codex thread tools are only supported for local threads.