What
When a session cannot be forked, the error now gives a specific reason rather than a generic refusal.
Details
- Persistence off: "Can't fork: session persistence is off, so the new session would have nothing to start from."
- Restricted flags: "Can't fork: this session was started with launch flags (safe or bare mode, a custom system prompt, a tool allowlist, or restricted settings)..."
- Nothing to fork yet: "Nothing to fork yet. Send a message first."
- Messages have also been shortened and made direct (no more parenthetical asides about worktrees or agent view)
Evidence
Fork error messages (search for "Can't fork: session persistence is off" or "Can't fork: this session was started with launch flags").
Strings lifted out of the shipped bundle, so the claim above can be checked against them.