Live session title refresh when hook returns hookSpecificOutput.sessionTitle

Problem

When a UserPromptSubmit hook returns hookSpecificOutput.sessionTitle, Claude Code Desktop does not update the displayed title until the app is fully quit and relaunched. The title is correctly persisted to the session sidecar at ~/Library/Application Support/Claude/claude-code-sessions/<workspace>/<project>/local_<uuid>.json, but Desktop reads this file only at startup — it doesn't watch for changes.

This makes the official sessionTitle hook field effectively useless for any automation that wants live, per-turn renaming (e.g. titling a session from a Topic line in the assistant's output).

Environment

• Claude Code CLI: 2.1.119
• Claude Desktop bundled Claude Code: 2.1.111
• Claude.app: 1.3883.0
• macOS 24.6.0

Repro

1. Configure a UserPromptSubmit hook that emits {"hookSpecificOutput": {"hookEventName": "UserPromptSubmit", "sessionTitle": "NewTitle"}}.
2. Submit a prompt in Desktop. Observe the sidecar JSON on disk — title is updated.
3. Desktop's displayed title (sidebar + header) remains the old Haiku-generated title.
4. Quit Desktop (⌘Q) and relaunch — title now shows correctly.

Requested

Have Desktop either:

• Watch the session sidecar JSON and re-render title on change, OR
• Emit an in-app event when the CLI subprocess reports a hook-set sessionTitle so the UI refreshes live.

Related open issues

• #29355
• #33165
• #35316