Reads
The page documents AGENTS.md in the project root and in subdirectories; nested files are combined, with more specific instructions taking precedence.
Sourcechecked
Which coding agent reads which instruction file
4 tools, 9 file types, 36 cells. Last reviewed 2026-10-16.
Each cell cites an official page and the date we checked it. A cell reads "unverified" when the page we checked does not mention the file. We then have no source, which says nothing about whether the tool reads it. A cell reads "migration only" when the page mentions the file only as input to a migration command such as /init. Counts: Reads: 12, Reads, with conditions: 1, Only if configured: 3, Migration only: 4, Not read: 1, Unverified: 15.
Scroll sideways to see every tool. The file column stays in place.
| File | Cursor | Claude Code | Codex | GitHub CopilotRepository custom instructions on GitHub.com (cloud agent, code review) |
|---|---|---|---|---|
AGENTS.mdOpen format for agent instructions. May sit in the repository root or in subdirectories. | Reads, with conditions from v2.1.277 Reads AGENTS.md only when there is no CLAUDE.md or CLAUDE.local.md in the working directory or above. Reading AGENTS.md directly needs v2.1.277 or later. Sourcechecked | Reads Reads AGENTS.md from the global Codex home and from the project root down to the working directory, at most one file per directory, up to 32 KiB combined by default. Sourcechecked | Reads Agent instructions: one or more AGENTS.md files anywhere in the repository; the nearest file in the directory tree takes precedence. Sourcechecked | |
AGENTS.override.mdOverride file used by Codex in place of AGENTS.md in the same directory. | Unverified Not mentioned on cursor.com/docs/rules or on cursor.com/help/customization/rules when checked. Sourcechecked | Not read The page lists AGENTS.local.md, AGENTS.override.md and anything under a .agents/ directory as not read. Sourcechecked | Reads Checked before AGENTS.md in each directory. In the Codex home, AGENTS.override.md replaces AGENTS.md when it exists. Sourcechecked | Unverified Not mentioned on the cited page or in GitHub's "Support for different types of custom instructions" table when checked. That table names copilot-instructions.md, *.instructions.md, AGENTS.md, CLAUDE.md, GEMINI.md and, for code review, REVIEW.md. Sourcechecked |
CLAUDE.mdClaude Code project instructions file. | Reads The help page says: "Cursor reads Sourcechecked | Reads Reads ./CLAUDE.md or ./.claude/CLAUDE.md, plus user, managed and local (CLAUDE.local.md) scopes. Sourcechecked | Only if configured Not part of default discovery. The page says Codex also reads names listed in project_doc_fallback_filenames and ignores names not on that list. Sourcechecked | |
GEMINI.mdGemini CLI instructions file. | Unverified Not mentioned on cursor.com/docs/rules or on cursor.com/help/customization/rules when checked. Sourcechecked | Unverified Not mentioned on the cited page when checked, including its /init migration list. Sourcechecked | Only if configured Not part of default discovery. The page says Codex also reads names listed in project_doc_fallback_filenames and ignores names not on that list. Sourcechecked | |
.cursorrulesSingle-file rules format used by early Cursor versions. | Migration only The help page mentions the file only in a migration section, where it calls it "legacy and will be deprecated". It does not say whether Cursor still loads it. Sourcechecked | Migration only Mentioned only in the /init migration section. /init reads Cursor rules in .cursor/rules/ or .cursorrules and incorporates the relevant parts into the generated CLAUDE.md. The page does not say Claude Code loads the file itself. Sourcechecked | Only if configured Not part of default discovery. The page says Codex also reads names listed in project_doc_fallback_filenames and ignores names not on that list. Sourcechecked | Unverified Not mentioned on the cited page or in GitHub's "Support for different types of custom instructions" table when checked. That table names copilot-instructions.md, *.instructions.md, AGENTS.md, CLAUDE.md, GEMINI.md and, for code review, REVIEW.md. Sourcechecked |
.cursor/rules/*.mdcCursor project rules with frontmatter (description, globs, alwaysApply). | Reads Project rules live in .cursor/rules as .mdc files. A plain .md file in that folder is ignored. Sourcechecked | Migration only Mentioned only in the /init migration section, as Cursor rules in .cursor/rules/. /init incorporates the relevant parts into the generated CLAUDE.md. The page does not say Claude Code loads these files itself. Sourcechecked | Unverified Not mentioned on the cited page, or in the configuration reference entry for project_doc_fallback_filenames, when checked. Sourcechecked | Unverified Not mentioned on the cited page or in GitHub's "Support for different types of custom instructions" table when checked. That table names copilot-instructions.md, *.instructions.md, AGENTS.md, CLAUDE.md, GEMINI.md and, for code review, REVIEW.md. Sourcechecked |
.claude/rules/*.mdClaude Code topic and path-scoped rules. | Unverified Not mentioned on cursor.com/docs/rules or on cursor.com/help/customization/rules when checked. Sourcechecked | Unverified Not mentioned on the cited page, or in the configuration reference entry for project_doc_fallback_filenames, when checked. Sourcechecked | Unverified Not mentioned on the cited page or in GitHub's "Support for different types of custom instructions" table when checked. That table names copilot-instructions.md, *.instructions.md, AGENTS.md, CLAUDE.md, GEMINI.md and, for code review, REVIEW.md. Sourcechecked | |
.github/copilot-instructions.mdRepository-wide GitHub Copilot instructions. | Unverified Not mentioned on cursor.com/docs/rules or on cursor.com/help/customization/rules when checked. Sourcechecked | Migration only Mentioned only in the /init migration section. /init reads Copilot rules in .github/copilot-instructions.md and incorporates the relevant parts into the generated CLAUDE.md. The page does not say Claude Code loads the file itself. Sourcechecked | Unverified The page says Codex checks fallback names from project_doc_fallback_filenames in each directory from the project root to the working directory. It does not say whether a path such as .github/copilot-instructions.md can be listed. Sourcechecked | |
.github/instructions/*.instructions.mdPath-specific GitHub Copilot instructions with an applyTo glob. | Unverified Not mentioned on cursor.com/docs/rules or on cursor.com/help/customization/rules when checked. Sourcechecked | Unverified Not mentioned on the cited page when checked, including its /init migration list. Sourcechecked | Unverified Not mentioned on the cited page, or in the configuration reference entry for project_doc_fallback_filenames, when checked. Sourcechecked | Reads NAME.instructions.md files under .github/instructions with an applyTo glob. On GitHub.com, supported for the cloud agent and code review only. Sourcechecked |
Legend
- ReadsThe official page says the tool reads this file.
- Reads, with conditionsThe tool reads the file only under the conditions stated in the cell.
- Only if configuredThe tool does not read the file by default but can be set up to.
- Migration onlyThe page mentions the file only as input to a migration command such as /init, which copies parts of it into the tool's own instruction file. It does not say the tool loads the file itself.
- Not readThe official page says the tool does not read this file.
- UnverifiedWe could not confirm this on the cited official page on the date shown.
Data
The same data is published as matrix.json. Need a starting file? Use the generator.
How to cite
The data and the text are under CC BY 4.0. Credit the project, link the license, and say what you changed. A cell is a dated reading of an official page, so give the date of the cell, which is shown on it, or the date the matrix was last reviewed.
Suggested credit: "Rulefiles data by Rulefiles contributors, https://rulefiles.dev/matrix/, last reviewed 2026-10-16, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)."
Quoted excerpts of the sources belong to their authors. Link the official page of the cell when you rely on it.
GitHub Copilot cells describe repository custom instructions on GitHub.com. Editor-specific behavior can differ and is not covered here.