# Rulefiles

> A weekly digest of dated, sourced changes in Cursor, Claude Code, Codex and GitHub Copilot, plus a matrix of which agent reads which instruction file.

Every digest item and matrix cell links to an official source and carries a date. Cells marked "unverified" were not confirmed on the cited page, and cells marked "migration only" are mentioned there only as input to a migration command. Pages are plain HTML without cookies. Their only third-party script is Cloudflare Web Analytics, which measures visits and page load performance.

## Data

- [Instruction file matrix](https://rulefiles-preview.pages.dev/matrix/): which of 4 tools reads which of 9 instruction files, last reviewed 2026-10-16
- [matrix.json](https://rulefiles-preview.pages.dev/data/matrix.json): the same matrix as JSON
- [digests.json](https://rulefiles-preview.pages.dev/data/digests.json): all digest issues as JSON
- [llms-full.txt](https://rulefiles-preview.pages.dev/llms-full.txt): matrix and digests as one Markdown file
- [License](https://creativecommons.org/licenses/by/4.0/): the data and the text are CC BY 4.0, credit "Rulefiles contributors" and link https://rulefiles-preview.pages.dev/; quoted excerpts belong to their authors; the code is MIT

## Instruction files

- [Instruction files](https://rulefiles-preview.pages.dev/files/): one page per file type, built from the matrix
- [Which coding agents read AGENTS.md?](https://rulefiles-preview.pages.dev/files/agents-md/): Open format for agent instructions. May sit in the repository root or in subdirectories.
- [Which coding agents read AGENTS.override.md?](https://rulefiles-preview.pages.dev/files/agents-override-md/): Override file used by Codex in place of AGENTS.md in the same directory.
- [Which coding agents read CLAUDE.md?](https://rulefiles-preview.pages.dev/files/claude-md/): Claude Code project instructions file.
- [Which coding agents read GEMINI.md?](https://rulefiles-preview.pages.dev/files/gemini-md/): Gemini CLI instructions file.
- [Which coding agents read .cursorrules?](https://rulefiles-preview.pages.dev/files/cursorrules/): Single-file rules format used by early Cursor versions.
- [Which coding agents read .cursor/rules/*.mdc?](https://rulefiles-preview.pages.dev/files/cursor-rules-mdc/): Cursor project rules with frontmatter (description, globs, alwaysApply).
- [Which coding agents read .claude/rules/*.md?](https://rulefiles-preview.pages.dev/files/claude-rules/): Claude Code topic and path-scoped rules.
- [Which coding agents read .github/copilot-instructions.md?](https://rulefiles-preview.pages.dev/files/copilot-instructions-md/): Repository-wide GitHub Copilot instructions.
- [Which coding agents read .github/instructions/*.instructions.md?](https://rulefiles-preview.pages.dev/files/copilot-path-instructions/): Path-specific GitHub Copilot instructions with an applyTo glob.
- [What the cited official pages don't say](https://rulefiles-preview.pages.dev/unverified/): the 15 cells marked unverified, with the cited page and the check date

## Digest

- [Claude Code v2.1.309, Copilot deprecations, global default](https://rulefiles-preview.pages.dev/digest/2026-W43/): 17 dated items, checked 2026-10-26
- [Digest for 12 to 18 October 2026](https://rulefiles-preview.pages.dev/digest/2026-W42/): 15 dated items, checked 2026-10-19
- [Digest for 5 to 11 October 2026](https://rulefiles-preview.pages.dev/digest/2026-W41/): 14 dated items, checked 2026-10-16
- [Atom feed](https://rulefiles-preview.pages.dev/digest/feed.xml): every issue

## Tools

- [Instruction file generator](https://rulefiles-preview.pages.dev/generator/): builds AGENTS.md, CLAUDE.md, Cursor rules and Copilot instructions in the browser

## Optional

- [About](https://rulefiles-preview.pages.dev/about/): method and limits
- [Privacy](https://rulefiles-preview.pages.dev/privacy/): no cookies; visits counted with Cloudflare Web Analytics
- [Sponsors](https://rulefiles-preview.pages.dev/sponsors/): sponsorship policy
- [Legal notice](https://rulefiles-preview.pages.dev/legal/): publisher, host and contact