Project change via openNewThread flashes loading skeleton

[yusuf8834]

Summary

Clicking a homepage project launcher that calls openNewThread({ projectId, focusPrompt: true }) briefly flashes BB's full-page loading skeleton. The existing compose screen should remain visible until the target project's composer is ready.

Versions and environment

• bb 0.40.1-nightly.33317473488.1 desktop app
• Plugin SDK 0.4.29
• macOS 26.6.2

Steps to reproduce

1. Open the root New thread page with a plugin homepage section.
2. From a project card, call experimental_useSidebarThreadActions().openNewThread({ projectId, focusPrompt: true }) for a different project.
3. Observe the route transition.

Expected vs actual

Actual: BB briefly shows the thread-page loading skeleton before the project composer appears.

Expected: Keep the current compose screen visible until the target composer is ready, or switch the selected project in place.

Evidence

Captured in BB thread thr_ip8dn2zyya. The report was reproduced and captured on the nightly above; the filing agent inspected the SDK and host navigation path but did not independently record the transition.

What you ruled out

• The flashed frame is host UI, not content rendered by the homepage plugin.
• The current SDK exposes no in-place project-selection action for the root composer.

Suggested priority and effort

Low. Visual flicker only, no data loss, and no clean plugin-side workaround.

• I reproduced this on the latest release or on main, or I say above that I could not.
• I searched open and closed issues for the same problem.
• If an agent wrote this, the body ends with > AGENT GENERATED and links the thread or report.

AGENT GENERATED

[bb-slop-cop]

🚨 SLOP COP 🚨 · new-issue-autopilot

Classification: Bug · Low priority · Low effort · ui

Report: https://get-bb.github.io/reports/issues/2742.html

Verdict: REPRODUCED · high confidence · confirmed-repro

Root cause: The SDK selected the project, then opened a legacy route that rendered a full-page skeleton.

Fix: #2745