The Claude Code Source Leak

Error
Tue, 31 Mar 2026 17:16:13 GMT

(mods: I assume this is blowing up twitter and so discussing it here won't do additional damage -- and there are already a thousand github forks -- but I am not actually on twitter, which is why I’m opening discussion here. It's possible I'm missing something. Feel free to nuke this if so.)

For those that hadn't heard yet, last night Anthropic appears to have accidentally published a Claude Code update with extractable source code in it. This seems important, but I'm not sure how much so, and I didn't see an existing discussion here.

My understanding -- and hopefully someone will correct me if I'm wrong -- is that the actually dangerous part of Claude is the weights, and those were not leaked. So the leak may be embarrassing, it may cost Anthropic some competitive advantage, but it's not dangerous.

It's also my understanding that Anthropic has historically been relatively leak-free, until a certain memo leaked a few weeks ago during the DoW incident. Supposedly twice is still coincidence, not enemy action, but it does feel like a questionable coincidence and I wonder if the same person is responsible for both leaks. I don’t know enough about npm packaging to guess how easy it would be to do by mistake. Alternate hypotheses: Human error updating the build tools? AI-written build scripts that somebody was a little too lax reviewing? That last seems more than plausible, come to think of it.

The most questionable thing in the actual codebase I've heard mentioned is a stubbed-out feature for "undercover mode" to suppress its self-identification in commit messages (but all that says is that they considered it at some point, maybe as a competitive concession to Codex doing the same thing by default? Unclear). There's been a few other things too. I haven't dug into the code myself so I don't know how seriously to take any of them.

I came here to see if there was any discussion of the situation, didn't see one, was disappointed, and decided to fix that. Soliciting information from anyone who knows more than me.

[edit:] Takedown notices have gone out, unsurprisingly. At least some (well, at least one) appear to have misidentified forks of CC's issue-tracker repo as forks of the offending leak. I don't care enough to object to the one I received, but if anyone from Anthropic sees this, you may want to either debug something or notify github, depending on who's IDing instances.

Discuss