[BUG] Cowork (Desktop, cloud session): model picker change is ignored while a turn is processing, and the picker display reverts to the default model while a different model is being served
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?
What's wrong
A Cowork session started on the default, Opus 5.5. I changed the picker to Fable 5.1 while the first turn was processing. The picker showed Fable 5.1, but the transcript shows the next 24 assistant records all served by claude-opus-5-5. The change was silently ignored.
I changed the picker to Fable 5.1 again while the session was idle. That took: every assistant record since is claude-fable-5-1 (8 at export, no fallback).
The picker then reverted to displaying Opus 5.5 on its own and has stayed there, while the served model is Fable 5.1. The session, asked, reports it is configured as claude-fable-5-1.
In the Chat surface the same picker holds correctly. In Cowork it neither reliably sets the model nor shows it.
Evidence
Attached transcript d78076c2-90e8-59b2-a472-492ffd37be99.jsonl, exported from /root/.claude/projects/-home-claude/ in the cloud workspace: the model field on assistant records shows 24 × claude-opus-5-5 then 8 × claude-fable-5-1, switching at the second picker change. Attached screenshot: picker reading "Opus 5.5 Medium" under the session's statement that it is configured as claude-fable-5-1.
What Should Happen?
Expected
A picker change applies from the next turn, whether or not a turn is in flight, and the picker always displays the model configured for the session.
Actual
Change ignored if made during processing, no notice; display drifts back to the default while another model serves.
Impact
The user cannot trust the picker in either direction and has no way to know the served model without reading the transcript from inside the session. For anyone who must not use a given model, both halves are silent failures.
Environment
Claude Desktop [version]; macOS [version], Apple Silicon; plan Max;
Error Messages/Logs
Steps to Reproduce
Steps to reproduce
Start a Cowork session on the default model; send a message.
While it is processing, change the picker to another model. Send more messages. Transcript still carries the default model.
While idle, change the picker again. Transcript switches.
Continue; the picker reverts to displaying the default model while the transcript keeps the selected one.
Claude Model
Other
Is this a regression?
I don't know
Last Working Version
_No response_
Claude Code Version
Claude 2.9939.2 (d3e504) 2026-09-24T17:20:35.000Z
Platform
Anthropic API
Operating System
macOS
Terminal/Shell
Terminal.app (macOS)
Additional Information
Ask
Until fixed, document which of picker or /model is authoritative in Cowork, and surface the served model per turn.