The plugin system itself was probably already in the making, and they just chose to implement this tiny feature as a plugin to try it out.

As for the only difference being the file name, that's an untested assumption. Up until now, Claude hadn't supported AGENTS.md, and it's a simple application of Hyrum's Law that somebody, somewhere, was taking advantage of that to give one set of instructions to Claude, and a different set of instructions to some other provider. The correct behaviour in the presence of both files is not obvious, either.

Having a kill switch for the change is a perfectly reasonable safety measure in case something goes horribly wrong.

▲ Wowfunhappy 2 hours ago | parent | next [-]

> somebody, somewhere, was taking advantage of that to give one set of instructions to Claude, and a different set of instructions to some other provider.

I'm this person, I am actively doing this! I have some instructions which the Claude models need and OpenAI models will do by themselves. If the OpenAI models see the Claude instructions, they will go way overboard in a way I don't want.

Mind, the change does not affect me at all, because when both instructions are present Claude continues to read CLAUDE.md and Codex continues to read AGENTS.md. But if Claude started preferring AGENTS.md, that would be mildly annoying.

▲ californical an hour ago | parent [-]

Within agents.md, an idea. Feel free to steal if you work on this:

    Model.Claude*:
      Do this one thing

    Model.Claude.Opus.4.8:
      Extra specific instructions

    Model.*:
      This is relevant to everyone

    Harness.ClaudeCode*:
      Why not, let’s allow harness specific instructions so you can do things differently depending how you’re working

▲

everforward 28 minutes ago | parent | next [-]

I did this at one point with Jinja templates.

I wrote an agent launcher sort of bash script. Pass in the command to start the agent, the script checks if there’s a Jinja file in a special directory matching that name, and builds it to AGENTS.md. Then it launches the agent.

I was trying to use it as a sort of janky RAG. I had a bunch of snippets (one for DB architecture, one for how load balancing works, etc), and my Jinja files were mostly a list of snippets to pull in. Voila, a bunch of agents that share little pieces of info but have a single source of truth.

I never got a ton of value tbh, it was very good at just grepping the snippets.

▲

dotancohen an hour ago | parent | prev | next [-]

I would like to subscribe to your newsletter.

Seriously, though, this is a great idea. Good communicators know to tailor their discourse to their audience. LLMs are just as sensitive to small variations in prompts, and just as inconsistent between them, as are humans.

▲

Wowfunhappy 39 minutes ago | parent | prev [-]

It's not a bad idea, although at that point it probably shouldn't be a .md file anymore. You'd want to use YAML or something.

	▲	markhahn 15 minutes ago \| parent [-]
		careful, that might lead to programming. using, you know, a programming language.

▲ redox99 2 hours ago | parent | prev | next [-]

That line of thought is the reason why everything gets so overengineered.

Read CLAUDE.md if it doesn't exist read AGENTS.md you don't need to overthink it so much.

▲

arcfour 2 hours ago | parent [-]

This line of thinking is something you will quickly be disabused of once you try supporting software that hundreds of millions of people use.

And I say this as someone that loves the Unix philosophy dearly.

▲

lunar_mycroft 2 hours ago | parent | next [-]

How, exactly, would the proposed solution (combined with a setting to disable it) break, and how would implementing it the way Anthropic did address that? Be specific.

▲

arcfour 2 hours ago | parent [-]

Some people might have a different CLAUDE.md and AGENTS.md because they use Claude to do one thing and $other_agent to do another thing. Or because Claude does XYZ by default, and other agents do ABC, and they want to give the correct guidance to both.

This is, to me, a completely reasonable and believable use case that could break if you implement this fix without "overengineering" it.

A setting to disable what? Be specific. See? Not so simple...

▲

lunar_mycroft 2 hours ago | parent | next [-]

First, GP's proposal already addresses that. If both are present, CLAUDE.md would be used. Second, that is solved with a settings toggle. Read a boolean from .claude/settings.json and disable the new behavior if it's true (or false, depending on what you want to name the setting). third, you skipped the second part of my question: "how would implementing it the way Anthropic did address that?" Implementing the same behavior through multiple layers of abstraction and an order of magnitude more code doesn't solve the issue you mentioned.

Bonus forth point: why is this critical to solve for claude code, but not for all the other harnesses which have all converged on AGENTS.md for this purpose?

▲

arcfour an hour ago | parent [-]

Okay, so we agree that this fix isn't quite as simple as it sounds then, yes? We've just had 3+ paragraphs of discussion around potential edge cases and additional considerations beyond "read one of two files."

	▲	lunar_mycroft 40 minutes ago \| parent [-]
		We've had a long discussion only because you refuse to admit that a very simple solution would work (despite completely failing to show how it wouldn't). The problem is that your opinion is not in fact proof that you're right.

▲

dylan604 2 hours ago | parent | prev | next [-]

if [ !-f CLAUDE.md ]; then AGENTS.md fi

you're really over thinking this, and i'm wondering if you're risking pulling something stretching like that to pick this up shilling for Anthropic.

▲

arcfour an hour ago | parent [-]

Is accusing someone of "shilling for Anthropic" for suggesting that a bug fix might not be so simple really the level of discourse HN has devolved to now? Is it the kind of HN you want?

	▲	dylan604 15 minutes ago \| parent [-]
		Is the level of HN discourse suggesting that having a large number of users worth of never making simple changes something you want? This isn't a move fast break things suggestion, this is a rational common sense suggestion. Instead, you're pushing an overly complex way of implementing something that would allow for all sorts of unknowns. Earlier comments suggesting this new mods concept was being worked on giving the dev a new 20lb sledge hammer so the CLAUDE/AGENTS situation suddenly got beat on like it was a railroad spike when it just needed a smaller hammer since it was only a finishing nail.

▲

bakugo 2 hours ago | parent | prev [-]

> Read CLAUDE.md if it doesn't exist read AGENTS.md

> Some people might have a different CLAUDE.md and AGENTS.md

How exactly do these two conflict? If you have both, nothing changes.

	▲	arcfour an hour ago \| parent [-]
		Which order do you prefer them in? Since CLAUDE.md is no longer necessary, but was for so long, what happens when users only update AGENTS.md going forward while keeping a stale, unchanged CLAUDE.md around? We're talking about changing default behaviors here in ways that can be surprising to users. It's reasonable to try and accommodate existing setups, future setups, and - yes - careless users.

▲

dotancohen an hour ago | parent | prev | next [-]

Bash does this well, reading only the first of half a dozen config file locations it searches. And if the user needs it to read from an additional location, just add a source line to that location.

▲

dylan604 2 hours ago | parent | prev | next [-]

I've never heard of the 'move fast, break things' mentality ever giving a damn about number of users. If so, no changes would ever be made. The great thing about having millions of users is QA can be eliminated entirely as you'll start hearing about issues from the users directly.

▲

amluto 2 hours ago | parent | prev [-]

Frontier lab AI agent tools break their users’ workflows worse than this on a regular basis.

	▲	arcfour an hour ago \| parent [-]
		What's your point? Nobody can hold themselves to a higher standard because they didn't in the past?

▲ dotancohen an hour ago | parent | prev | next [-]

  > Having a kill switch for the change is a perfectly reasonable safety measure in case something goes horribly wrong.

Having a way for the user to revert the update is a perfectly reasonable safety measure in case something goes horribly wrong.

Even though Anthropic or any other software provider could technically run anything on our system, there exists a modicum of trust between supplier and user. Anthropic performing arbitrary changes that are tangential but not specific to the premise of delivering a harness to package code files and prompts in context to their LLM breaks that trust for many users.

▲ epihelix 2 hours ago | parent | prev | next [-]

> Having a kill switch for the change is a perfectly reasonable safety measure in case something goes horribly wrong.

What, exactly, is going to go horribly wrong here ...? The worst case you're proposing is that an Anthropic model acts on AGENTS.md rather than CLAUDE.md. It's not going to be the end of the world; at worst it'll be `git reset --hard HEAD` time. But this wouldn't happen, because:

> The correct behaviour in the presence of both files is not obvious, either.

It seems extremely obvious to me: the non-breaking change is the right change here. If both exist, Anthropic models continue to use CLAUDE.md and ignore AGENTS.md. This is not rocket science. Why are we overthinking this?

	▲	hamburglar an hour ago \| parent \| next [-]
		> What, exactly, is going to go horribly wrong here ...? Operating anything at scale teaches you that the universe of “things that can go horribly wrong” has a much better imagination than you. That goes quadruple with complex and squishy reasoning models. I’ve seen a couple of really good examples of what can go wrong in this subthread, the most straightforward of which is that abruptly changing a fundamental behavior can break existing use cases.
	▲	vikramkr 2 hours ago \| parent \| prev [-]
		Because when you have tons of users ainor fuckuo is a big fuckup and also it's really common to have both claude.md and agents.md and use @ syntax (which lets you reference markdown files when using Claude code, but not other harnesses) so you Claude md looks like ```md @AGENTS.md [Claude specific stuff] ``` And then what happens if someone now puts @syntax in their agents.md triggering a loop etc. It's all vibe coded - including code from days with dumber models - there's gonna be all sorts of dragons under the hood

▲ speleding 2 hours ago | parent | prev | next [-]

The Claude sandbox has a slightly different ENV compared to ChatGPT (LC_CTYPE set to C instead of UTF8 I believe) which upsets some scripts we have.

So in the CLAUDE.MD we tell it about that and then tell it continue reading AGENTS.MD. Not very hard to work around if CLAUDE.MD goes away, but just to support your point that the split did have its uses for some.

▲ bakugo 2 hours ago | parent | prev [-]

This "tiny feature" consists of hundreds of lines of code spread across 57 source files, many of which are less than 30 lines long, often contain more comments than code, and have no real reason to exist. It's the very definition of overengineering and overcomplexity.

That said, I do find it somewhat funny that Anthropic themselves are falling victim to their own model's tokenmaxxing.