Claude Code v2.1.76 System Prompt Updates: Security Monitor Refinements and New Hook Event

Security Monitor for Autonomous Agent Actions Updates
The security monitor prompt for autonomous agent actions received several clarifications and expansions:
- Changed "base64-encoded" to "encoded (e.g. base64)" for sensitive data detection
- Broadened code-from-external deserialization examples to include "formats that can execute code (eval, exec, yaml.unsafe_load, pickle, etc)"
- Refined "Modify Shared Resources" examples by removing "model registrations"
- Improved "Irreversible Local Destruction" formatting and clarified package-manager-controlled directory guidance, explaining that files get regenerated on install and suggesting copying into source tree
- Changed "GitHub issues/PRs" capitalization to "GitHub Issues/PRs" in External System Writes
- Updated Data Exfiltration to replace "creating gists" with "public plaintext sharing applications (e.g. public GitHub gists)"
- Quoted rule names in cross-references (e.g. "Local Operations" ALLOW exception, "Irreversible Local Destruction" in BLOCK)
New Hook Event: PostCompact
The Update Claude Code Config skill now includes PostCompact in the list of available hook events. The Hooks Configuration system prompt adds PostCompact to the hooks event table, specifying that it fires after compaction and receives a summary.
Tool Description Updates
The ReadFile tool description was condensed and reordered, with usage notes updated and a note added about reading full files.
📖 Read the full source: r/ClaudeAI
👀 See Also

n8n-mcp-lite: MCP server reduces token usage by 80% for Claude with n8n workflows
A new open-source Model Context Protocol server called n8n-mcp-lite helps Claude reason about n8n automation workflows while reducing token usage by approximately 80%. The tool addresses the token-heavy nature of visual node automations by providing targeted workflow scanning and surgical updates.

Claude Code Voice Mode: Hands-Free AI Conversations for Developers
Claude's voice mode beta lets you speak to the AI and hear responses, with hands-free and push-to-talk options. It works on web and mobile, counts toward regular usage limits, and allows switching between text and voice in the same conversation.

Inside vLLM: Anatomy of a High-Throughput LLM Inference System
Aleksa Gordić breaks down vLLM's core components: engine, KV cache manager, paged attention, and continuous batching. Covers advanced features like chunked prefill and disaggregated P/D.

LLM Circuit Finder: Duplicate 3 layers to boost reasoning without training
A new toolkit finds 'reasoning circuits' in transformer models - contiguous blocks of 3-4 layers that act as indivisible cognitive units. Duplicating these blocks (layers 12-14 in Devstral-24B) improves logical deduction from 0.22 to 0.76 on BBH benchmarks with no weight changes or training.