Claude Code 2.1.72 System Prompt Updates: New Execution Modes and Verification Improvements

New System Prompts and Execution Modes

Claude Code 2.1.72 adds three new system prompts:

• Auto mode - Continuous task execution mode that functions like a background agent
• Brief mode - Codex-like execution mode with short status updates before launching into work
• Post checkpoints - Instructions for how to post checkpoints during task execution

Tool Updates

The release includes new tool descriptions:

• ExitWorktree - Tool for leaving a git worktree mid-session, with option to keep or remove it
• ToolSearch (second part) - Second part of the ToolSearch tool description with query modes and usage examples

Removed items include Tool permission mode guidance, standalone searching tools guidance, and extended ToolSearch usage instructions (replaced by ToolSearch second part).

Agent Prompt Changes

Significant updates to agent prompts:

• Claude guide agent - Removed inline agent metadata block (agent type, model, permission mode, tool list, and when-to-use guidance)
• Explore strengths and guidelines - Added agent metadata block with agent type, model, disallowed tools, when-to-use guidance, and critical read-only system reminder (moved from Explore prompt)
• Explore - Removed inline agent metadata block (moved to Explore strengths and guidelines)

Major Verification Specialist Expansion

The Verification specialist agent received substantial updates:

• Two documented failure patterns: verification avoidance and "first 80%" bias
• Structured per-check output format requiring command run, output observed, and result
• Self-rationalization recognition section with common excuses to override
• Guidance to match rigor to stakes
• Pre-FAIL checklist to avoid flagging intentional behavior or already-handled cases
• Defined PARTIAL as environmental limitations only
• Updated mobile verification strategy to use accessibility/UI tree dumps instead of screenshots
• Clarified that test suite results are context, not evidence

Other Key Updates

• Simplify skill - Added "Recurring no-op updates" as a new efficiency check for state/store updates in polling loops or event handlers that fire unconditionally without change detection
• Fork usage guidelines - Refined forking criteria from a list of use cases to a qualitative "will I need this output again" heuristic; added guidance that forks beat Explore subagent for research because they inherit context and share cache; added warning not to set a different model on forks to preserve cache reuse
• Tool usage prompts - Generalized individual tool name references to unified search tools references in both delegate exploration and direct search prompts
• EnterWorktree tool - Added mention of ExitWorktree for leaving the worktree mid-session; clarified that the keep/remove prompt on session exit only applies if still in the worktree

Internal changes include variable renames in Agent and WebSearch tool descriptions with no user-facing impact.