Anthropic's Scion accused of copying Meta's Mononoke design
An engineer who helped build Meta's Mononoke source control server published a post arguing that Anthropic's new Scion version control system uses the same "derived data" concept in a way that goes well beyond sharing similar insights. He notes that Anthropic's engineering post credited Sapling only for "hard-won lessons" and never mentioned Mononoke, calling this close to plagiarism, while adding that he does not object to Anthropic reusing the open-source design — the post also says that both Opus 5.5 and GPT-6 Astra immediately point to Mononoke when asked about prior art.
As LLMs increasingly help design new systems, they lean on existing designs in their training data, making credit and attribution a growing engineering-ethics issue.
Update 2026-10-15: I wrote a followup to answer questions and concerns.
Discuss on Hacker News or Lobsters.
Here is Anthropic describing (archive link) yesterday how their new version control system, Scion, uses a concept called “derived data” to make operations like blames more efficient:
How Anthropic describes Scion’s derived data.
Here is me, back in 2022, describing in my Oxide candidate materials how the Mononoke source control server I helped build uses a concept called “derived data” to make operations like blames more efficient:
#Anthropic#Scion#Meta#Mononoke#Sapling#Claude Opus 5.5#GPT-6 Astra