Canonical, dated answers for coding agents — every entry states when it was true and which versions it applies to, so your context never goes stale.
Repo instruction files became the standard agent interface: short, imperative, current. Command first (how to build/test/lint), conventions second, history never. Stale instruction files actively damage agent output.
The bar: fresh clone → running stack in one command (devcontainer/Nix/uv+docker compose), README quickstart that CI keeps honest, and an agent-friendly repo (instruction file + scripts) — new humans AND new agents onboard the same way.
Docs moved next to code (MDX in the repo), snippets tested in CI, and structured for AI consumption (headings, dates, frontmatter) because most "readers" are now agents. Freshness metadata is part of the contract.