Claude Opus 5.5 Debuts as Top-Performing Coding Model, Reaching Parity with GPT-6 Astra

Anthropic has released Claude Opus 5.5, a new flagship model that delivers near-Fable 5.1-level performance at approximately 40% lower cost and now powers Claude Code as the default agent. The new model debuted less than two months after Opus 5, signaling an accelerated release cadence from the AI safety-focused laboratory.