Set Your Claude Code Sessions to Run Without You: ANTHROPIC_DEFAULT_MODEL, Auto-Resume, and notify_when_idle

Three Claude Code settings from the weeks 33–34 changelog that together cover the "start it and walk away" workflow: a persistent default model, a session that restarts itself, and a ping when a background session goes idle.

ANTHROPIC_DEFAULT_MODEL — pin your startup model system-wide

Export it in your shell profile:

export ANTHROPIC_DEFAULT_MODEL=claude-sonnet-5-20260801

Unlike ANTHROPIC_MODEL (which applies only to the session you launch with the flag), ANTHROPIC_DEFAULT_MODEL sets the model every new session starts on. A /model pick in the session overrides it and persists across restarts — so per-project overrides still work. Use it if you have a preferred model you want without passing --model every time.

Auto-resume after a usage-limit pause

Claude Code now restarts your session automatically when a claude.ai usage limit resets, rather than dropping the session at the ceiling. If you're running a long-running job and step away, the session picks back up when your quota refills. Disable it in /config → "Continue session when usage limit resets" if you'd rather decide manually each time.

notify_when_idle in cross-session SendMessage

When you launch a background session, you can ask it to send a desktop notification the next time it goes idle:

{"to": "my-review-session", "message": "notify_when_idle"}

One-shot and opt-in — the session sends one notification when it goes idle, then stops. Runs on macOS and Linux only (same-machine).

What these don't cover

• notify_when_idle is same-machine only — cloud sessions or remote runners can't ping back.
• Auto-resume applies to claude.ai time-based usage limits, not API token quotas.
• ANTHROPIC_DEFAULT_MODEL takes effect at session start, not mid-session.

Sources: Claude Code changelog — code.claude.com · Cross-session messaging — code.claude.com · Model configuration — code.claude.com · Claude Code August changelog summary — releasebot.io