“Source control for huge monorepos has prior art, notably Google’s Piper and Meta’s Sapling, so we were able to build Scion with their hard-won lessons in mind.”
Mononoke is a component of Sapling, as I understand it. In fact, the repo link provided in this article links to a subdirectory of the Sapling repo. I’m not totally sure I understand the complaint.
If I credit my newly introduced car as inspired by Corvette, then sure, it might be ok not to mention the engine (Mononoke is the server part of Sapling)
However if my new car's engine is a near copy of the one in the Corvette, and my announcement gushes about the engine using the same terms the Corvette design team invented...
The level of inspiration goes well beyond "hard-won lessons". Something like Lore (slop design document aside) can claim that level of inspiration. Here the data model is a direct copy, down to the terminology.
To be uncharitable, this is marketing for Anthropic's impending IPO.
Effectively nobody considering buying into the IPO cares about Anthropic's source control system. They could be passing around floppy disks and so long as they were still shipping nobody would care.
Not about the details but the marketing story is all about how "agents" are building so fast they need to design new infrastructure for the new world, etc. Extra points if you spin it as though the "agents" have built some new never-before-seen architecture that is clearly better than the "human scale" stuff.
The intended audience is obvious from first paragraph alone:
> At Anthropic, coding is no longer the bottleneck to building systems or doing research. Claude is able to autonomously iterate on research loops, micro-optimize complex programs, and build new services from the ground up at a speed and scale we haven’t seen before. The bottleneck, now, is all of the developer infrastructure built for human scale: source control, builds, and CI.
Translation:
> We are so far at the cutting edge we need to build shiny new infrastructure to replace the smelly "human scale" cruft. How could you /not/ value us at $2T?
Who cares about your opinions about what number of PRs is right? They want to make more PRs (particularly to a monorepo), they need a new VCS.
Even if they weren't making a lot of PRs, Github has been melting down enough this year that they've probably encouraged customers like Anthropic to move off.
> Here the data model is a direct copy, down to the terminology.
That’s not surprising to me - they designed and built it using their LLMs, of course it’s duplicating prior work. That’s essentially the core of what LLMs do, after all.
> And, to be clear, I do not have a problem with Anthropic copying Mononoke’s design. (This is part of why we put out open source — to benefit humanity through the spread of good ideas.)
> But as LLMs continue to assist in designing new systems, they are likely to index heavily on existing designs. Mononoke is open source and in every LLM’s training set. If you ask Opus 5.5 or GPT-6 Astra (thanks Matthew Fowle) about prior art, they both immediately point out the similarities to Mononoke.
> Giving credit to those that came before us is now easier — and more important — than ever. There is no longer an excuse.
Yes, and I would like it to explicitly say that their data model is very similar to Mononoke's, and avoid even the appearance of the idea that Claude came up with it de novo.
I didn't think that their article implied Claude had come up with the design.
I thought it was likely that their team of 7 included ex-Meta and ex-Google people with knowledge of those company's internal version control solutions.
I saw RMS give a talk once on Free Software. He wore three quarter length cargo pants and sandals with no socks, and spent a good amount of the talk picking a scab off his shin to the point where he started bleeding. It got on his fingers. No one said anything.
There are things in this world that people can and should be stopped from doing, and there which anyone can do unhindered if they so wish. In between those two boundaries there’s a standard of decent behavior that one should strive for in order to be considered a good person.
Giving credit isn’t required, but many consider it basic decency.
OTOH I'm not seeing the problem with scraping a scab. I have hands, my attention is focused on something, then my hands will scrape where it itches (the scab).
"I built a thing in the style of X" (which is even more charitable than what Anthropic piece said) is different than "I incorporated X from Y to build a thing this way."
When Fable first released, I had it "one shot" a project using an initial spec and a team of agents. I was blown away with how good the results were.
And then I noticed some links to images from random small github projects and realized somewhere along the way agents had searched for existing projects and copied almost everything.
I wonder if something similar happened here on a larger scale.
I think a lot is memory really. For fun you can try pointing just about any model against the older kaggle challenges and it’ll come up with more or less the winning solution from memory. It’s here where you see a Gemma 27b perform about the same as opus 5.5
Is this what is expected of how to cite sources? Because if this is the expectation nobody does it.
There are two cases and only one is an issue for citations:
- Mononoke was directly consulted and not attributed
- Concepts were reinvented or used as a derivative (Sapling cited Mononoke and implements something similar)
For one I know Sapling, Git, and Jujutsu, but up to today I have never heard of Oxide or Mononoke and I am not exactly compelled to look up the research papers of any of them, at most I read through their high level documentation.
Anthropic effectively doing a "git clone" with extra steps here.
Uncharitable?
I don't think so.
If this were about functionality, why not use Sapling/Mononoke or extend it and contribute back to the open source community?
Because that doesn't juice the IPO valuation.
hi rain :) Anthropic’s post reminded me a lot of your work, glad this is getting some visibility. do you think the “time has come” for some of these ideas that previously may not have spread because they need too much learning to appreciate? I wonder what new norms will emerge in creative collectives.
Thanks! Yeah, I think overall several more organizations are going to reach the scale that Meta reached a while ago. I'm not sure if they'll go in the monorepo or polyrepo direction, though; I can see arguments both ways.
Agents tend to act differently than humans here. I would have expected most humans to notice and acknowledge the connection. Passing it off as one's own insight definitely feels like plagiarism. Agents are generally not equipped to deal with this type of thing, since looking for prior art is a detour from their goal or an exercise in post-hoc rationalization of knowledge built into the weights.
Whether it is plagiarism or hacking, the buck has to stop with the operators. It's not a good look.
1. Sapling can refer to either the system as a whole, or just the client people use (`sl`, forked from `hg`).
2. EdenFS is the virtualized FUSE filesystem (closely modeled after SrcFS at Google).
3. Mononoke is the distributed system that implements the backend server storage + the API they describe for checkout-less writes.
All three come together to form the core of the Meta source control experience. From what I can tell, Anthropic built its own version of 1 and copied 2 and 3, plus also built out a code review tool separately.
The company is predominantly FAANG people. They’re going to just rebuild what they know. I don’t think you need any kind of conspiracy here. One year into ad tech and everyone was using HyperLogLog. Everyone was using 20 years ago LMAX-style disruptor, and single threaded event queue powered by loop called governor. It’s just what happens. People carry in their head what they know.
IP maximalism is the present zeitgeist but that’s just how knowledge flows.
It isn’t something I care very much about, except when it’s used as a certificate of achievement. I almost never do literature searches with an attempt to dedupe. I only ever do it to see if someone has explored something better than I have. That’s often the case but other times it is not.
Absolutely not. When I create projects I only credit other existing systems if they are a direct inspiration. If I independently come up with the same idea as someone else I see no reason for me to do the due diligence and credit them.
Okay, well, in this case (even accepting your argument) I've been told there is direct overlap in contributors so there is no feasible way they couldn't have known.
Damn. It’s hard not to see it as plagiarism. I can only imagine the surprised Pikachu face you must have made reading that announcement from Anthropic.
It's totally wild seeing entities being criticized for writing software based on/very similar to other open source software. Ffs, this used to be what open source software was about. It was actually the fucking point [1].
> And, to be clear, I do not have a problem with Anthropic copying Mononoke’s design. (This is part of why we put out open source — to benefit humanity through the spread of good ideas.)
Followed by:
> But as LLMs continue to assist in designing new systems, they are likely to index heavily on existing designs. Mononoke is open source and in every LLM’s training set. If you ask Opus 5.5 or GPT-6 Astra (thanks Matthew Fowle) about prior art, they both immediately point out the similarities to Mononoke.
I think it is the duty of any responsible engineer to look for and cite prior art and related work, if only to compare notes.
I did, but those additional requirements are outside the licenses and the legal framework, and more wanting them to match your personal vibe/moral framework around open source. There's case law around this going back to the 80's. A third party is allowed to independently produce, and be extremely inspired, by open source code, and then can license it however they want. Protecting copied functionality is NOT PROTECTED. Again, that was the fucking point. You could, for example, swap out compatible software if you wanted! You wouldn't be tied to one vendor!
Open source licensing protects direct copying. It does NOT protect re-implementing from scratch. See all the lawsuits around Java. You should not be using open source software if you don't want others to read your source!
Yes, I am aware that that credit is not required by law, nor in this case do I wish for credit to be required by law. I am appealing to norms, to basic decency.
I really really wish Sapling could be used externally. It is by-and-large TheWay.
Centralized, virtual file system, all commits automatically on cloud, large binary files totally fine, Mercurial CLI. It’s fantastic. People who only use Git really don’t understand how much better things can be.
Working for a few years at Facebook, and then returning to the normal world, it was like stepping back in time -- I really think that the mainstream git culture (by which I mostly mean "github") achieved a local maxima around 2012, and has been holding the industry back since :(
(Like GH finally has some support for stacks, 15 years late, with an implementation which is somehow more complicated and less powerful than the prior art...)
“Source control for huge monorepos has prior art, notably Google’s Piper and Meta’s Sapling, so we were able to build Scion with their hard-won lessons in mind.”
Mononoke is a component of Sapling, as I understand it. In fact, the repo link provided in this article links to a subdirectory of the Sapling repo. I’m not totally sure I understand the complaint.
However if my new car's engine is a near copy of the one in the Corvette, and my announcement gushes about the engine using the same terms the Corvette design team invented...
Then can you see how a mention might be nice?
To be uncharitable, this is marketing for Anthropic's impending IPO.
The intended audience is obvious from first paragraph alone:
> At Anthropic, coding is no longer the bottleneck to building systems or doing research. Claude is able to autonomously iterate on research loops, micro-optimize complex programs, and build new services from the ground up at a speed and scale we haven’t seen before. The bottleneck, now, is all of the developer infrastructure built for human scale: source control, builds, and CI.
Translation:
> We are so far at the cutting edge we need to build shiny new infrastructure to replace the smelly "human scale" cruft. How could you /not/ value us at $2T?
Even if they weren't making a lot of PRs, Github has been melting down enough this year that they've probably encouraged customers like Anthropic to move off.
That’s not surprising to me - they designed and built it using their LLMs, of course it’s duplicating prior work. That’s essentially the core of what LLMs do, after all.
Mononoke and Sapling are open source systems. Why shouldn't new software take inspiration from how they are designed?
> And, to be clear, I do not have a problem with Anthropic copying Mononoke’s design. (This is part of why we put out open source — to benefit humanity through the spread of good ideas.)
> But as LLMs continue to assist in designing new systems, they are likely to index heavily on existing designs. Mononoke is open source and in every LLM’s training set. If you ask Opus 5.5 or GPT-6 Astra (thanks Matthew Fowle) about prior art, they both immediately point out the similarities to Mononoke.
> Giving credit to those that came before us is now easier — and more important — than ever. There is no longer an excuse.
Fair enough.
I thought it was likely that their team of 7 included ex-Meta and ex-Google people with knowledge of those company's internal version control solutions.
There are things in this world that people can and should be stopped from doing, and there which anyone can do unhindered if they so wish. In between those two boundaries there’s a standard of decent behavior that one should strive for in order to be considered a good person.
Giving credit isn’t required, but many consider it basic decency.
OTOH I'm not seeing the problem with scraping a scab. I have hands, my attention is focused on something, then my hands will scrape where it itches (the scab).
Another Claude-written article
This is the load-bearing seam.
And then I noticed some links to images from random small github projects and realized somewhere along the way agents had searched for existing projects and copied almost everything.
I wonder if something similar happened here on a larger scale.
More seriously, I'm curious if you checked on the licensing of said codebases, were they permissive or strong copyleft?
There are two cases and only one is an issue for citations: - Mononoke was directly consulted and not attributed - Concepts were reinvented or used as a derivative (Sapling cited Mononoke and implements something similar)
For one I know Sapling, Git, and Jujutsu, but up to today I have never heard of Oxide or Mononoke and I am not exactly compelled to look up the research papers of any of them, at most I read through their high level documentation.
I guess that is the case.
Whether it is plagiarism or hacking, the buck has to stop with the operators. It's not a good look.
Edit: I was too lazy. From the README: "Mononoke is the server built for the Sapling Source Control System"
1. Sapling can refer to either the system as a whole, or just the client people use (`sl`, forked from `hg`).
2. EdenFS is the virtualized FUSE filesystem (closely modeled after SrcFS at Google).
3. Mononoke is the distributed system that implements the backend server storage + the API they describe for checkout-less writes.
All three come together to form the core of the Meta source control experience. From what I can tell, Anthropic built its own version of 1 and copied 2 and 3, plus also built out a code review tool separately.
IP maximalism is the present zeitgeist but that’s just how knowledge flows.
Open source is not IP maximalist by any means. I am merely asking that the appropriate credit be provided.
Written about it here before: https://wiki.roshangeorge.dev/w/Blog/2026-09-08/Intellectual...
It isn’t something I care very much about, except when it’s used as a certificate of achievement. I almost never do literature searches with an attempt to dedupe. I only ever do it to see if someone has explored something better than I have. That’s often the case but other times it is not.
The first step in approaching anything difficult is seeing whether someone else has already solved it.
[1] https://en.wikipedia.org/wiki/Open-source_software_movement
> And, to be clear, I do not have a problem with Anthropic copying Mononoke’s design. (This is part of why we put out open source — to benefit humanity through the spread of good ideas.)
Followed by:
> But as LLMs continue to assist in designing new systems, they are likely to index heavily on existing designs. Mononoke is open source and in every LLM’s training set. If you ask Opus 5.5 or GPT-6 Astra (thanks Matthew Fowle) about prior art, they both immediately point out the similarities to Mononoke.
I think it is the duty of any responsible engineer to look for and cite prior art and related work, if only to compare notes.
Open source licensing protects direct copying. It does NOT protect re-implementing from scratch. See all the lawsuits around Java. You should not be using open source software if you don't want others to read your source!
Maybe 5 years ago that would be the expectation but all etiquette has been thrown out the window with AI. I think you expect too much.
Another effort I couldn't have done without Astra. Even more so. All I did, the only reason I got cited, was because I'd asked Astra.
Centralized, virtual file system, all commits automatically on cloud, large binary files totally fine, Mercurial CLI. It’s fantastic. People who only use Git really don’t understand how much better things can be.
(Like GH finally has some support for stacks, 15 years late, with an implementation which is somehow more complicated and less powerful than the prior art...)
I agree so hard. It’s inertia is too strong and we’ve stalled progress for a decade.