If you use more than one coding agent, you have probably ended up with a small pile of context files: CLAUDE.md for Claude Code, AGENTS.md for Codex, maybe leftover .cursorrules from an older Cursor setup. They all do the same conceptual job, which is giving the agent a persistent briefing that survives across sessions. The question is which one to maintain in 2026, and the answer is more nuanced than picking a winner.
Disclosure: I work on Blume, a desktop app that manages agent configuration across tools. This post stays practical and tool-agnostic; Blume appears once near the end where it is relevant.
The short version
AGENTS.md is the closest thing to a universal standard. It is recognized by Codex CLI, Copilot CLI, Gemini CLI, Cursor, and Claude Code itself.
CLAUDE.md is Claude Code's native file, and it still has capabilities AGENTS.md does not standardize, most notably hierarchical loading and imports.
