What happened
Claude Code’s 2.1.277 update adds support for AGENTS.md, a plain-text file that tells a coding agent how to work in a project: which commands to run, which conventions to follow, which files matter most. The release adds direct loading of AGENTS.md; projects could already import it through CLAUDE.md. The default reads AGENTS.md when no qualifying CLAUDE.md or CLAUDE.local.md exists in the working directory or above it.
You can see and change the selection under “Project instructions” in /config, Claude Code’s settings menu. Anthropic’s current instruction-file documentation includes an option to load both files. It also says some sessions, including Amazon Bedrock sessions, lacked direct support before version 2.1.281; update older installations and check the setting.
OpenAI told Codex users to rewrite their AGENTS.md files for GPT-6 Astra. That file format isn’t tied to one company. Anthropic, OpenAI’s Codex, and other coding agents have been converging on AGENTS.md as a shared standard, the same way most projects now include a README file that any tool can open and expect to find basic setup instructions in. Claude Code adding read support is a small technical change with a bigger implication: fewer builders will need to maintain two nearly identical instruction files just because they use more than one coding agent.
Why it matters
The default uses one set of project instruction files. A qualifying CLAUDE.md or CLAUDE.local.md prevents direct AGENTS.md loading under that setting, even if AGENTS.md is newer. You can choose the option to load both files, or import AGENTS.md from CLAUDE.md.
That matters for anyone who has used Claude Code before and also uses a second coding agent, like Codex, that reads AGENTS.md. If an old CLAUDE.md is still present, creating a fresh AGENTS.md does not make Claude Code load it under the default setting. Check the active selection rather than assuming that creating the shared file makes its instructions available.
Who should care
Anyone running more than one coding agent against the same repository, and anyone who has an old CLAUDE.md they haven’t touched in a while. If you’ve only ever used Claude Code and never created an AGENTS.md, nothing changes for you yet.
What builders should do next
Open a project you work in with Claude Code and run /config. Look for “Project instructions” and check which file it says it’s reading. If you intend to standardize on AGENTS.md across tools, first preserve any Claude-specific rules that are missing from AGENTS.md. Merge the instructions you still need before renaming the old file, or choose to load both and remove contradictory rules. Confirm the selection in /config and the loaded files in /context. Don’t just create the AGENTS.md and assume it’s live.
If Project instructions is unavailable, check your installed version and whether the built-in AGENTS.md plugin is disabled. Importing AGENTS.md through CLAUDE.md remains an alternative.
Correction, October 13, 2026: The default selects CLAUDE.md first, but /config can load both files. An import provides another way to share AGENTS.md instructions.
End of article