[Bug]: Mobile New thread opens a draft in the open thread's project without asking #25622

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/mobile

Steps to reproduce

1. Connect the mobile app to an environment with three projects: atlas, beacon, comet (registered in that order).
2. Open a thread in beacon.
3. Start a global New thread:
   • iPad (split layout): tap the compose button in the thread header.
   • iPhone or a folded iPhone Duo (compact layout): press ⌘N on a hardware keyboard, or choose New thread in… in the command palette.

Expected behavior

New thread asks which project to start in, with beacon listed first. Backing out returns to the beacon thread.

Actual behavior

A draft opens immediately in beacon ("What should we build in beacon?"). There is no step to choose a project. The only way to start somewhere else is to notice the project name in the draft's heading and tap it.

With no thread open, the same action opens a draft in the oldest project (atlas), because newTaskDestination falls back to projects[0] and the server returns projects by created_at.

Both paths come from newTaskDestination in apps/mobile/src/features/threads/new-task-project-selection.ts, added in #23467. It returns a draft for the current project, else projects[0], and never the picker.

Related:

• [Bug]: Mobile New task on iPhone always defaults to the oldest project #25391 reports the oldest-project default on iPhone.
• fix(mobile): stop defaulting new threads to the oldest project #24359 removes the projects[0] fallback. With a thread open, New still skips the picker.
• feat(mobile): add a "Use last project" preference for new threads #24741 adds an on-by-default "Use last project" setting. Turning it off opens the picker even with a thread open.

The case here is New with a thread open. None of these change it by default.

Impact

Minor bug or occasional failure

Version or commit

main @ 374e57d

Environment

First seen on a physical iPhone Duo, unfolded (split layout). Reproduced in the iOS Simulator (Xcode 27.1) with a dev client on main @ 374e57d: iPhone 17 Pro (⌘N) and iPad mini (A17 Pro, compose) on iOS 26.3, and iPhone Duo folded (⌘N) on iOS 27.1. The simulator could not unfold the Duo. Synthetic projects only.

Logs or stack traces

No response

Screenshots, recordings, or supporting files

iPad mini, split layout. Left: the beacon thread. Right: after tapping compose.

Workaround

Tap the project name in the draft's heading and pick another project.