Mythos Firefox 147 Exploit Benchmark

Description

Internal Anthropic benchmark re-running Opus 4.6's Firefox 147 JavaScript-engine vulnerability set against Mythos Preview. Opus 4.6 produced 2 working exploits out of several hundred attempts; Mythos produced 181 working exploits plus 29 additional register-control achievements on the same vulnerability set. Converted from discovery benchmark into a reusable capability regression test.

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Sources

src-20260409-a5ff5a259c43