It initially thought it found something, but when asked to produce a testcase, it thought for 20 minutes and admitted defeat
IainIreland on Hacker News
In the thread “Hardening Firefox with Claude Mythos Preview”, replying to this comment
Helped: Supplementing manual investigations with AI audits for similar problems.
Got in the way: Opus failed to produce a valid testcase after 20 minutes.
… I did get Opus to do an audit for similar problems elsewhere, to supplement the investigations that we were already doing by hand. It initially thought it found something, but when asked to produce a testcase, it thought for 20 minutes and admitted defeat. I suspect that the difference between Opus and Mythos is in small edges like this: if Mythos is smart enough to spot why Opus's discovery didn't work a little bit faster, and it can waste less time chasing down red herrings, then it's more likely to find a real bug within the limits of a context window. …