bug(webui): archived session "flashes back" due to SSE race condition

[hotic]

Problem

When archiving a session in WebUI sidebar, the session briefly disappears then reappears (~100ms later).

Possible Cause

The session.archive API may trigger a session.updated SSE event before archive completes. The optimistic update removes the session, but then the stale event re-adds it.

Suggestion

Use the same logic as TUI - call session.delete API instead, which sends a session.deleted event and avoids confusion with update events.

Video

2026-01-12_06.31.23.mp4

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Context size in sidebar not updated after /compact #5760: Context size in sidebar not updated after /compact - similar SSE/sidebar state synchronization issue
• Session Todo-list is forgotten after compaction #5934: Session Todo-list is forgotten after compaction - related to session state persistence after backend operations
• Session Changes / Modified Files show changes from origin/main #7555: Session Changes / Modified Files show changes from origin/main - another sidebar data consistency issue with stale information

All three share the core pattern of WebUI/sidebar state being out of sync with backend state. Feel free to ignore if none of these address your specific case.