Claude Opus 5.5 ports HAProxy to Rust faster and cheaper than Fable 5.1

Anthropic introduced Claude Opus 5.5 as the first model in its Claude 5.5 family, saying it performs at the level of Claude Fable 5.1 for most tasks at 40% lower run cost than Opus 5. Boris Cherny reports that Opus 5.5 and Fable 5.1 each ported HAProxy from C to Rust and both passed nearly all of its tests, with Opus 5.5 finishing in 9.5 hours versus 12 hours and at 51% less cost.