STANDARDS AND CONVENTIONS

COMPARING COMPETING CONVENTION FILES Different vendors of coding agents popularized their own instructions files, each with a similar purpose but a different file name and sometimes a slightly different format. Examples include a file called AGENTS.md, a file called CLAUDE.md used by the Claude Code product, and rule files used by various code editors and assistants. (A file ending in md is written in the simple Markdown text format, which is plain text with light labeling.) AGENTS.md appeared in 2025 as an open format, with OpenAI as a leading contributor, and it was later placed under the care of the Agentic AI Foundation, a group hosted by the Linux Foundation that was announced in December 2025. The Linux Foundation is a nonprofit organization that hosts many shared open-source projects. Because this area changes quickly, verify the current file names and which tools read which files by consulting each tool's own documentation. When several files exist, a few differences are worth comparing. Name and location: where the file lives and what it is called. Scope: whether a tool reads only the root file, or also reads extra files in subfolders, so that a rule can apply to one part of the project only. Format: whether the file is free-form text or has required sections. Extra features: some tools allow a file to refer to other files, or to apply only to certain file types. Many projects face a practical problem when team members use different tools. Maintaining three nearly identical files creates drift, which means the copies slowly stop matching because someone updates one and forgets the others. Drift is dangerous, because the agents of different vendors will then follow different rules in the same project. Two common remedies exist. One is to keep one shared file and configure each tool to read it, where the tool allows that. The other is to keep one real file and make the others short pointers that simply say to read the shared file. Either way, the principle from Chapter 48 applies, which is to keep one source of truth.