System-Prompts

Anthropic has been publishing its Claude product system prompts since July 2024 — and as of April 2026, no other major AI lab has followed suit. That persistent gap in transparency practices deserves attention, especially in light of a recent episode that illustrates exactly why public system prompt changelogs matter. A Postmortem Written in Real Time On April 16, Anthropic updated Claude Opus 4.7’s system prompt to include a verbosity reduction — a change intended to make responses more concise. The update was reflected in Anthropic’s public system prompt changelog within days of deployment. ...

If you’ve used GitHub Copilot, Claude Code, Cursor, or OpenAI Codex and wondered what’s actually happening under the hood when the agent “thinks,” plans a multi-step fix, and edits three files at once — Simon Willison just published the definitive practitioner answer. Willison’s new chapter of Agentic Engineering Patterns — titled “How Coding Agents Work” — is the clearest technical breakdown yet of what separates a coding agent from a coding assistant, and why that distinction matters enormously for how you use and build with these tools. ...