Claude Code v2.1.140: Agent tool usage notes, stricter Self-Modification rules, Snooze warnings

Claude Code v2.1.140 (+622 tokens) shipped several prompt and tool description updates that tighten agent behavior and clarify when to use tools. Here's the relevant breakdown:

Agent Tool simplified usage notes

New usage notes cover:

• When to delegate (fork vs. direct execution)
• Fork behavior and how worktrees isolate agent contexts
• Resumption mechanics after a fork
• Worktree isolation rules
• Background execution support
• Parallel launches and context restrictions

Self-Modification rules – explicit path list

The Self-Modification rule was expanded from a vague description to an explicit list of agent-config paths that constitute self-modification:

.claude/settings.json, CLAUDE.md, CLAUDE.local.md, .claude.json, .claude/rules/, .claude/hooks/, .claude/commands/, .claude/agents/, .claude/skills/, .claude/output-styles/, .claude/workflows/, .claude/routines/, .claude/scheduled_tasks.json, .claude/loop.md, .mcp.json

Exceptions: Files under .claude/worktrees/<name>/ are treated as ordinary project files. A project-specific .claude/ subdirectory not in the above list is not Self-Modification on its own.

Worker fork prompt cleanup

Removed “in your system prompt” from the “default to forking” reference so the rule applies generically to parent guidance.

Snooze tool – prevent short wakeup abuse

The tool description now includes an explicit warning: do not schedule short-interval wakeups to poll for harness-tracked background work – the agent is re-invoked automatically when it finishes. Use a longer 1200s+ fallback heartbeat instead. The sub-5-minute cache window is appropriate only for actively polling external state the harness cannot notify about (e.g., CI runs, deploy statuses, remote queues). Example updated from bun build to a CI run.

Write tool – when to use

Rewritten into a “When to use” format:

• Creating a new file
• Fully replacing a previously-read file

For partial changes, use the edit tool instead.

Full diff available on GitHub: Piebald-AI/claude-code-system-prompts v2.1.140.