@bcherny: Opus 5.5 is a really good model. It's been my daily driver the last few weeks. We had Opus 5.5 and Fable 5.1 each port …

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Claude Opus 5.5 is an AI model that outperformed Fable 5.1 in porting HAProxy from C to Rust, completing the task faster and at a lower cost.

Opus 5.5 is a really good model. It's been my daily driver the last few weeks. We had Opus 5.5 and Fable 5.1 each port HAProxy from C to Rust. Both passed nearly all of HAProxy's tests, but Opus 5.5 finished in 9.5 hours compared to Fable 5.1's 12 hours, and for 51% less cost.
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Cached at: 09/22/26, 07:56 PM

Opus 5.5 is a really good model. It’s been my daily driver the last few weeks.

We had Opus 5.5 and Fable 5.1 each port HAProxy from C to Rust. Both passed nearly all of HAProxy’s tests, but Opus 5.5 finished in 9.5 hours compared to Fable 5.1’s 12 hours, and for 51% less cost.

Claude (@claudeai): Introducing Claude Opus 5.5, the first model in our new Claude 5.5 family.

It performs at the level of Claude Fable 5.1 for most tasks, and costs 40% less to run than Opus 5.

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