Claude Opus 5.5

Claude Opus 5.5, released in September 2026, is the current Opus model and the natural starting point in the Claude lineup. It reads text and images, holds 1M tokens of context and writes up to 128K tokens per reply. It performs at the level of Claude Fable 5.1 on most work, generates output more than 30% faster than Claude Opus 5 and gets through comparable tasks in fewer steps.

It is at its best on long, sprawling jobs such as codebase-wide migrations and audits, performance work across a web app, or careful code review. Outside code, it writes research reports with source-checked figures and quotes and builds Excel models and executive presentations. Its writing leads with the key point and follows the style rules you give it.

Pick Opus 5.5 when work needs careful judgment over many steps. Claude Sonnet 5.5 comes close on several tasks and runs faster, so it suits well-scoped everyday work, while Claude Fable 5.1 is the step up for the hardest reasoning. All three live in the same Endless workspace and draw on its shared credits.