[FEATURE] Unique Session IDs and Inter-Session Mentioning

Problem Statement

When managing multiple parallel Claude Code sessions, it is difficult to uniquely identify them and reference specific sessions in prompts. This makes it hard to coordinate work across different sessions or delegate tasks between them with precision.

Proposed Solution

1. UI Visibility: Display a short, unique session ID (e.g., claude-code-0e) next to the session name in the Claude and Claude Code UI. For example: "PR fixing (claude-code-0e)".
2. Session Mentioning: Introduce a way to mention a specific session by its ID in the prompt using a syntax like @agents:session-id. This would allow a user in one session to communicate with or query the state of another.

Alternative Solutions

Currently, users can only refer to sessions by name, which may not be unique or easy to type. There is no native way to "address" another active session.

Priority

Medium - Would be very helpful for power users managing complex, multi-session workflows.

Feature Category

Interactive mode (TUI)

Use Case Example

1. A user has two sessions: "PR fixing" (ID: claude-code-0e) and "Research" (ID: claude-code-1a).
2. In the "Research" session, the user wants to check if the "PR fixing" session has tasks that could be handled by the current agent.
3. The user types: "Ask if @agents:claude-code-0e has another task that it can delegate to you to complete".
4. Claude Code resolves the mention to the specific session and coordinates the request.

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)