Desktop “Branch in new chat” does not preserve parent model and reasoning effort

What version of the Codex App are you using?

Codex Desktop 26.820.60940

What platform are you using?

macOS

What issue are you seeing?

Clicking “Branch in new chat” from an existing task creates a new task that does not preserve the parent task’s selected model and reasoning effort.

The new task instead appears to use the model and reasoning effort most recently selected elsewhere in the app, rather than the values active in the parent task.

Steps to reproduce

1. Open an existing task.
2. Select a specific model and reasoning effort in that parent task.
3. Click “Branch in new chat.”
4. Inspect the model and reasoning-effort selection in the new task.

Expected behavior

The branched task should inherit the parent task’s effective model and reasoning effort, unless the user explicitly changes them.

Actual behavior

The branched task uses the app’s most recently selected model/reasoning-effort combination instead of the parent task’s selections.

This can silently change capability, cost, latency, and behavior when branching a carefully configured task.

Related issues

• #32061 — resumed sessions do not restore their recorded model and reasoning effort
• #28860 — selective context transfer and chat branching
• #39269 — Voice Chat Fork loses parent model selection and project context
• #32506 — Desktop fork stores history but loses model-visible context

Start with the Desktop “Branch in new chat” entry point and trace how the parent task’s model and reasoning effort are transferred to the new task. Reproduce the issue using the listed steps, then verify that the branched task preserves both parent selections unless explicitly changed.