"...After fixing the initial set of issues that Anthropic sent to us in February, we built our own harness atop our existing fuzzing infrastructure.
We began with small-scale experiments prompting the harness to look for sandbox escapes with Claude Opus 4.6. Even with this model, we identified an impressive amount of previously-unknown vulnerabilities which required complex reasoning over multiprocess browser engine code..."
So yeah, Anthropic and Mozilla likely compare "Amount of bugs found by Opus 4.6 during early experiments" vs "Amount of bugs found by Mythos during large-scale codebase scanning".
"...After fixing the initial set of issues that Anthropic sent to us in February, we built our own harness atop our existing fuzzing infrastructure.
We began with small-scale experiments prompting the harness to look for sandbox escapes with Claude Opus 4.6. Even with this model, we identified an impressive amount of previously-unknown vulnerabilities which required complex reasoning over multiprocess browser engine code..."
So yeah, Anthropic and Mozilla likely compare "Amount of bugs found by Opus 4.6 during early experiments" vs "Amount of bugs found by Mythos during large-scale codebase scanning".
[1] https://hacks.mozilla.org/2026/05/behind-the-scenes-hardenin...