I am amazed at the speed of change in the industry.
Having started to use agentic coding on several open source projects I was appalled at the divergence of different names for instruction files.
Just over a week ago, I started to plan a project to try and at least standarise the open source projects, picking ChatGPT / OpenAI Codex AGENTS.md as the best option of a generic name (and avoid creating new standards).
I didn't get to do much until this weekend, and spent the time creating the Agent Rules (https://agent-rules.org/) microsite and raising feature requests with various open source projects.
My approach is fairly light-weight, based on projects like Editor Config, Semantic Versioning, and Conventional Commits).
This drew out a few comments that, following down the rabbit hole, it looks like the approach from Codex has already gained traction (within the last week) and will become the standard.
A lot of the discussion was on X, so I asked Grok to summarise the timeline and at how fast this has moved.
Prompt
Response
Timeline of "AGENTS.md" Discussions on X
"AGENTS.md" refers to a Markdown file placed in code repositories to provide AI coding agents (like Codex from OpenAI, Amp from Anthropic, Gemini from Google, and others) with contextual instructions, such as project overviews, style guidelines, migration notes, validation steps, and best practices. It helps agents understand and work within a codebase more effectively. The conversation on X highlights fragmentation across tools (e.g., variations like AGENT.md, CLAUDE.md, GEMINI.md, .cursorrules) and a push toward standardization on "AGENTS.md" for interoperability.
Key themes in the conversation:
- Fragmentation and Frustration: Developers complain about competing file names leading to "cursed" setups and inefficiency.
- Standardization Efforts: Calls for unity, with OpenAI acquiring the agents.md domain and collaborating with Google and Anthropic.
- Adoption and Tips: Sharing configs, prompts to generate the file, and tool integrations. Emphasis on its role in agent-driven development.
- Broader Context: Tied to AI agent tools' evolution, with users noting improved performance when agents read these files.
Below is a chronological timeline based on X posts, focusing on major milestones, announcements, and discussions. Dates are approximate based on post timestamps.
| Date | Key Event/Post | Summary/Details |
|---|---|---|
| May 16, 2025 | Early mentions of competing standards | Aiden Bai (@aidenybai) posts a meme about "9 competing standards for AI agent rules," sparking discussions on fragmentation. Greg Kamradt (@GregKamradt) shares how AGENTS.md clarifies thinking for AI and humans. Quinn Slack (@sqs) from Sourcegraph explains Amp's AGENT.md choice and commits to potential alignment. |
| May 17, 2025 | OpenAI's response and domain squat issue | Alexander Embiricos (@embirico) from OpenAI agrees on needing one file, DMs for collaboration. Posts note agents.md domain was squatted initially. |
| May 19-22, 2025 | Usage tips and integrations | Dan Mac (@daniel_mac8) shares prompts to generate AGENTS.md via Codex. Nicolas Bustamante (@nicbstme) demos Codex creating the file. konumaru_v2 (@konumaruuu_v2) notes OpenAI's own Agent SDK uses AGENTS.md. |
| June 6-7, 2025 | Calls for contribution ease | Jonas Templestein (@jonas) suggests OSS projects invest in AGENTS.md to attract AI-assisted contributors. ronin (@seatedro) lists variations like AGENTS.md vs. AGENT.md. |
| June 16, 2025 | Utility releases | Alessio Fanelli (@FanaHOVA) releases "agents-927," a CLI to sync instruction files across formats. |
| June 20-21, 2025 | Tool updates and standardization push | Jules (@julesagent) from Google Labs adds AGENTS.md support, improving autonomy and testing. Kath Korevec (@simpsoka) calls on Anthropic and OpenAI to standardize on AGENTS.md to avoid mess. |
| June 22-25, 2025 | Config tips and complaints | angelo (@giaccoangelo) frustrated by agents blocking on missing files. chokudai (@chokudai) critiques Gemini CLI but notes AGENTS.md potential. Denis Moskalets (@denyamsk) laments the "curse" of multiple files (agents.md, CLAUDE.md, GEMINI.md, .cursorrules). Gota (@gota_bara) shares Gemini CLI config to use AGENTS.md. David Ondrej (@DavidOndrej1) provides JSON config for Gemini CLI compatibility. |
| June 26-27, 2025 | More calls for unity | Taelin (@VictorTaelin) urges agreement on AGENTS.md before escalation. Walden (@walden_yan) from Cognition Labs shares "Agents 101" lessons, indirectly tying to file standards. |
| July 2-3, 2025 | Phoenix and Factory AI support | Zach Daniel (@ZachSDaniel1) announces Phoenix.new supports AGENTS.md with Ash Framework. intestine (@v_intestine) notes GitHub Copilot references similar files. |
| July 9, 2025 | Meme revival | Aiden Bai revives the "one more AI agent rules file" meme, highlighting ongoing issues. |
| July 16, 2025 | OpenAI acquires domain | Alexander Embiricos announces OpenAI got agents.md domain, plans microsite for best practices with Codex, Amp, Gemini. Calls for examples. Quinn Slack commits Amp to support AGENTS.md with backcompat. |
| July 17, 2025 | Sharing setups and configs | Brennan McEachran (@i_am_brennan) shares a gist of a "wiki-style" AGENTS.md directing agents to repo parts. Andrew Jefferson (@EastlondonDev) notes the distinction (AGENTS.md for OpenAI, AGENT.md for Anthropic). Eno Reyes (@EnoReyes) confirms Factory AI native support. Michael Wall (@sound4movement) and Alexander Embiricos discuss advanced setups. Sahebjot Singh (@zereraz) notes AGENTS.md emerging as standard. |
| July 18, 2025 | Google and OpenAI integrations | Mark McD (@m4rkmc) enables LLMS.TXT on Gemini API docs, tying to AGENTS.md. N. Taylor Mullen (@ntaylormullen) explains Gemini CLI config for AGENTS.md. Mario Zechner (@badlogicgames) spots OpenAI Codex adopting it. Tobias Möritz (@tobimori) and geoff (@GeoffreyHuntley) clarify origins (Amp's AGENT.md migrating to AGENTS.md). Julian Cardenas Mazo (@juliankmazo) praises Sentry's API rules in AGENTS.md. cutsea110 (@cutsea110) tweaks branch naming via AGENTS.md. |
| July 19, 2025 | Ongoing tweaks | NeurAlch (@NeurAlch) suggests AGENTS.md for Cursor rules. |
| July 20, 2025 | Latest updates and fixes | Beyang (@beyang) announces Amp migrating to AGENTS.md. Eyal Toledano (@EyalToledano) adds Zed and OpenCode support via TaskmasterAI. Sly Gryphon (@sgryphon) notes fixes and configs for multiple tools, linking to agent-rules.org. Olle Pridiuksson (@pridiuksson) jokes about adding grok.md to the collection. |
Overall Conversation Summary
The discourse started as complaints about inconsistent file names in May 2025, evolved into collaborative standardization efforts by mid-June, and culminated in OpenAI's domain acquisition and tool adoptions in July. Users like @simpsoka and @VictorTaelin drove the push for unity, while practical shares (e.g., configs, gists) helped adoption. By July 20, 2025, AGENTS.md is gaining traction as the neutral standard, with tools like Codex, OpenCode, Gemini CLI, Jules, and Factory AI supporting it. Developers see it as essential for agent efficiency but warn of over-reliance without human oversight. For more, check the agents.md microsite (once live) or agent-rules.org.