Standing rules belong in AGENTS.md, not in memory: OpenAI says so, and Astra reads AGENTS.md closely. Reasoning: Astra Medium. The testing sentences are OpenAI's own recommended text for Astra, which otherwise writes broader tests than a small task needs. AGENTS.md scope: ~/.codex/AGENTS.md globally, then per-repository files from the Git root down to the working directory. Free template — copy and paste into ChatGPT, Claude, or Copilot.