What happened?

When an agent session calls exit-worktree to leave a git worktree, the session view tears down and rebuilds. The message timeline unmounts, remounts with only 4 rendered messages, and content reassembles in-place — causing visible flicker, a large layout shift (CLS 0.38), and a 178ms jank burst. After the rebuild, when the user sends a follow-up message, the scroll position jumps from the bottom to near the top (scroll_top: 20451 → 4), forcing the user to manually scroll back.

Root cause chain

1. Agent calls exit-worktree → backend updates activeDirectory to project root
2. Sync propagates sync.data.path.directory change to frontend
3. directory-layout.tsx detects the change and navigate()s to a new URL with the updated base64-encoded directory
4. <Show when={resolved()} keyed> destroys and recreates the entire SDK/Sync subtree
5. SyncProvider reset clears all message caches (sync.data.message[id] becomes undefined)
6. session-main-view.tsx <Match when={...}> sees timelineMessagesReady → false → MessageTimeline unmounts
7. Messages reload from backend → timelineMessagesReady → true → MessageTimeline remounts with rendered_count: 4

Scroll-to-top (secondary)

After the rebuild, the user sends "下一步是什么？". A todo_force data refresh fires. The <Match when={...}> in session-main-view.tsx:132-136 uses its when value as an implicit SolidJS key. If timelineMessagesReady briefly becomes undefined during the refresh cycle, the <Match> destroys and recreates MessageTimeline. The new scroll container starts at scrollTop≈0, and the scroll-to-top is captured before forceScrollToBottom can recover.

Evidence from the session export:

scroll_height is identical (21356), ruling out content-height change. scroll_top=4 is near-zero but not zero, consistent with DOM replacement (browser overflow-anchor residual) rather than a scrollTo(0,0) call.

Steps to reproduce

1. Open PawWork in a git project
2. Ask the agent to enter-worktree into a git worktree
3. Let the agent complete some work (commits, file changes)
4. Ask the agent to exit-worktree
5. Observe the timeline flash, content rebuild, and layout shift
6. Send a follow-up message after the rebuild
7. Observe the scroll position jump to the top

What did you expect to happen?

• Exiting a worktree should keep the existing message timeline intact
• No visible teardown or rebuild of the session view
• Scroll position should be preserved across the directory change

Diagnostics

Renderer diagnostics from session export

Code pointers

• packages/app/src/pages/directory-layout.tsx — <Show when={resolved()} keyed> destroys subtree on directory change
• packages/app/src/pages/session/session-main-view.tsx:132-136 — <Match when={...}> implicit key destroys MessageTimeline on transient state changes
• packages/app/src/pages/session/message-timeline.tsx:415-425 — onMount/onCleanup emit timeline mount/unmount events
• packages/app/src/pages/session/use-session-scroll-dock.ts — createAutoScroll state reset on scrollRef change
• packages/ui/src/hooks/create-auto-scroll.tsx — scroll position tracking and auto-follow logic

Environment

• PawWork: dev (local build)
• OS: macOS 25.3.0
• Session export: pawwork-session-nimble-wizard-2026-05-04-08-59-46.json