Claude system prompts as a git timeline

# Research: Claude system prompts as a git timeline Source: https://simonwillison.net/2026/Apr/18/extract-system-prompts/ Claude system prompts as a git timeline (https://github.com/simonw/research/tree/main/extract-system-prompts#readme) — Anthropic's published system prompt history for Claude is transformed into a git-based exploration tool, breaking up the monolithic markdown source into granular files and timestamped commits. By structuring extracted prompts per model, family, and revision, researchers can leverage `git log`, `diff`, and `blame` to trace prompt evolution, compare differences, and attribute changes to specific dates—all without manual parsing. Anthropic publish the system prompts (https://platform.claude.com/docs/en/release-notes/system-prompts) for Claude chat and make that page available as Markdown (https://platform.claude.com/docs/en/release-notes/system-prompts.md). I had Claude Code turn that page into separate files for each model and model family with fake git commit dates to enable browsing the changes via the GitHub commit view. I used this to write my own detailed notes on the changes between Opus 4.6 and 4.7 (https://simonwillison.net/2026/Apr/18/opus-system-prompt/).