Claude Code 2.1.277 reads AGENTS.md when there is no CLAUDE.md, and subagent output now carries an anti-spoofing header
The Claude Code changelog entries for 2026-09-18 and 09-19 land two things builders will feel immediately. 2.1.277 adds AGENTS.md support: in a project with no CLAUDE.md, Claude Code reads AGENTS.md instead, switchable under Project instructions in /config, and not yet available on Bedrock, Vertex or Foundry. The same pair of releases adds omitClaudeMd to agent frontmatter and the --agents JSON so custom and plugin subagents can run without user, project and local CLAUDE.md files loading (managed policy files still load), and changes subagent results to render under a header marking them as subagent output, indented to prevent spoofing. The AGENTS.md item drew 675 points on Hacker News, which is a fair read on how long people have been asking.
↳ Follow the thread