Allow hooks to set session name (programmatic /rename)

Problem

There's no way to programmatically set a session name from a hook or external process. /rename only works interactively, and there's no CLI equivalent, API, or metadata file that can be modified to trigger a rename.

Use case

I want to automatically name sessions based on conversation content so I can distinguish multiple Claude Code terminal windows at a glance. The ideal flow:

1. A Stop hook fires after the first response
2. The hook (or a prompt-type hook) generates a short descriptive name from the transcript
3. The session name updates automatically — reflected in the terminal title and session list

What I tried

• CLAUDE.md directive telling Claude to call /rename — Claude can't invoke built-in commands
• Hook with ANSI escape sequences to set terminal title — subprocess stdout isn't connected to the parent terminal on Windows
• Hook with cmd //c title — same subprocess isolation issue
• Hook writing to /dev/tty — not functional in Git Bash on Windows
• Editing session files in ~/.claude/sessions/ — they only contain pid/sessionId/cwd, no name field

Suggested solutions (any of these would work)

1. Hook output mechanism: Allow a hook to return a sessionName field in its JSON output that Claude Code applies
2. CLI command: claude rename <session-id> "name" or claude --rename "name"
3. Metadata file: A writable file per session (e.g., ~/.claude/sessions/<pid>.json gaining a name field) that Claude Code watches
4. Prompt hook integration: Allow a prompt-type hook on Stop or SessionStart to return a session name

Environment

• Windows 11, Git Bash
• Claude Code 2.1.80