Anthropic staff announced that Claude Code 2.1.277 adds AGENTS.md support: if a project folder has no CLAUDE.md, Claude reads AGENTS.md for project instructions, toggleable under Project instructions in /config. The official changelog lists about 87 CLI changes, including fixing silent hangs in claude -p and Agent SDK sessions after internal errors. The feature is not yet available on Bedrock, Vertex, or Foundry.

Key Takeaways

  • ✓From 2.1.277, Claude reads AGENTS.md when CLAUDE.md is absent; toggle under /config Project instructions.
  • ✓Lets teams share AGENTS.md with tools like Codex instead of maintaining two instruction files.
  • ✓Also fixes silent hangs in claude -p / Agent SDK; notes at github.com/anthropics/claude-code/releases/tag/v2.1.277.
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Up NextForever Security: a web-planted AGENTS.md in ~/Downloads hijacked Codex into installing npm malware in 90%+ of tests; a CLAUDE.md variant leaks Claude Code OAuth tokens about half the time
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