PR #26526 - manaflow-ai/cmux

Problem

A harness can be signed out or have an expired account while the composer still shows its model as selectable. The first prompt then discovers auth failure too late.

Leo's request:

"we also want to be having that modal picker situation, like be able to surface, say, like, Oh, you gotta re-authenticate. You gotta log in again on the modal picker before the user even sends a prompt. You know, some sort of thing that raises."

Change

Show the existing _acpmux/harness/health result in the selected harness row and on the closed model control before sending.
Offer Log In beside the closed control and inside the picker without sending a turn. Empty or whitespace-only login commands produce no action.
Keep signed-out models unavailable for fresh sessions. For an established session, machine-wide health is a nonblocking login offer: it may be cached or describe different credentials from the session's account/route. Model and provider selections remain usable in the full picker and both compact layouts.

The gallery includes the normal signed-in picker and the signed-out selected-harness state.

Validation

Head: bf126f5e8dadea7c57d5074d15f4b24e99ca188a.

Final verification run 40638222418 passed at bf126f5e8dadea7c57d5074d15f4b24e99ca188a: 10 tests passed, 0 failed, 43 assertions across the two focused signed-out suites; full webviews web lint (including formatting, source checks, lint and typecheck) passed. The receipt confirms source and post-check head both equal the PR head, with exit code 0. Comparison base: 0c8336391b32df85bcdd7db7eac2f3f0f82a54d8.

Before / after

Synthetic Chromium captures from run 40645379232, using the same fixture on base 0c8336391b32df85bcdd7db7eac2f3f0f82a54d8 and head bf126f5e8dadea7c57d5074d15f4b24e99ca188a. The closed control adds “Signed out · Log In” beside the model name. The open popover is otherwise unchanged.