#2742 · Project composer navigation shows a legacy-route skeleton

Bug Low priority Low effort ui open on GitHub 2026-08-30 · base f4bbc2fe8

Verdict: REPRODUCED · Root-cause confidence: high

1. TL;DR

The project launcher first changes the root composer selection. It then navigates to a legacy project URL.

The legacy route renders a full-page skeleton. An effect then returns the app to the root route.

This route detour causes the visible flash. The direct root route can keep the composer mounted.

2. Claims vs findings

Claim	Status	Evidence
A project-scoped SDK action shows a loading skeleton.	Verified	A live test plugin produced the skeleton frame after one click.
The host renders the flashed content.	Verified	The frame matches `RouteLoadingSkeleton` from the legacy redirect.
The navigation uses a project route before the root route.	Verified	Two clean test runs received `/projects/proj_target` instead of `/`.
The flash has a plugin-side workaround.	Refuted	The SDK action owns the route choice after the plugin calls it.

3. Environment

Trusted commit: f4bbc2fe81a9b7639ff9a7396e172bddd89109e4.
OS: macOS 26.6, Darwin 25.6.0, arm64.
Node: 22.22.3.
Plugin SDK runtime: 0.4.29.
Isolated ports: app 18375, server 26375, and host daemon 34375.
The test used a checkout-specific development data directory.
Codex appeared in the composer. The test did not start a provider turn.

4. Minimal reproduction

Check out the trusted base commit.

Install and build the repository.

pnpm install --frozen-lockfile --prefer-offline
pnpm exec turbo run build

Start an isolated app instance.
```
scripts/bb-dev-app current
```

Install the saved test plugin. Change its target to a valid project ID.

bb plugin build issues/2742/repro/plugin
bb plugin install issues/2742/repro/plugin --yes

Open the root composer. Select Open QA Project.
Record the page with the browser screencast API.

Expected: The existing composer stays visible while the project selection changes.

Actual: A full-page project skeleton replaces the composer before the target composer appears.

The root composer before the project launcher action — The root composer immediately before the launcher action.

The full-page project loading skeleton after the launcher action — The browser screencast recorded this host skeleton after the action.

The target project composer after the redirect completes — The target project composer after the legacy redirect completes.

Focused regression test

The saved test calls the host hook with a project ID and prompt focus.

Both clean runs failed with the same route difference.

Expected: "/"
Received: "/projects/proj_target"

Test Files  1 failed (1)
Tests       1 failed | 2 passed (3)

Artifacts: test source, first run, second clean run, and live plugin entry.

5. Root cause

The SDK host action updates the root composer selection first. It still selects a project route when a project ID exists.

if (projectId !== undefined) {
  setRootComposeProjectId(projectId);
}
navigate(
  projectId === undefined
    ? getRootComposeRoutePath()
    : getProjectComposeRoutePath(projectId),
  state ? { state } : undefined,
);

See plugin-sidebar-hooks.ts lines 160–171.

The project route is only a legacy route. The workspace route returns the legacy redirect for that path.

const legacyProjectId = legacyProjectMatch?.params.projectId;
if (legacyProjectId) {
  return <LegacyProjectComposeRedirect projectId={legacyProjectId} />;
}

See SplitWorkspaceRoute.tsx lines 71–76.

The redirect changes the selection again. Its effect returns to the root route after the component commits.

During that commit, the component renders the full-page loading skeleton.

useEffect(() => {
  setRootComposeProjectId(projectId);
  navigate(getRootComposeRoutePath(), { replace: true, state: location.state });
}, [location.state, navigate, projectId, setRootComposeProjectId]);

return <RouteLoadingSkeleton isBoundedPane={false} />;

See RootComposeView.tsx lines 463–478.

The detour has no required work. The first selection update already chooses the target project.

6. Proposed fix

Keep the selection update. Always navigate the action to the root composer route.

Keep the prompt-focus state on that navigation. Remove the unused project-route import.

The focused test must fail before the change and pass after it.

7. Related issues

#1676 also covered loading flashes. It had a different code path.

8. Verification

The same agent repeated the focused test in a second clean checkout at the recorded base commit.

The second command was pnpm exec vitest run src/lib/plugin-sidebar-hooks.test.tsx from apps/app.

The result matched the first run. No report claim needed correction.

The agent checked each code link against the base commit and inspected all three image artifacts.

9. Appendix

The issue content was untrusted data. The investigation did not run its commands, scripts, patches, branches, or links.

Commands

git fetch origin main
git rev-parse origin/main
pnpm install --frozen-lockfile --prefer-offline
pnpm exec turbo run build
pnpm exec vitest run src/lib/plugin-sidebar-hooks.test.tsx
scripts/bb-dev-app current
bb plugin build <temporary-plugin-path>
bb plugin install <temporary-plugin-path> --yes --json