Breaking

Anthropic Launches Claude Sonnet 5.5 as Faster, Lower-Cost Counterpart to Opus 5.5

September 29, 2026 at 02:14 EDT

Foundation Models
AI Agents
Software Dev & Coding

Anthropic has released Claude Sonnet 5.5, positioning the new model as a faster and lower-cost counterpart to Claude Opus 5.5 for everyday coding, agent tasks, documents, slides and spreadsheets. The company says the model is now available across its own platform and major cloud partners, with the same per-token pricing as Sonnet 5 but materially better speed and benchmark results.

Sep 28, 2026 · Anthropic

Claude Sonnet 5.5 Moves Into The Fast Lane

Anthropic is positioning Sonnet 5.5 as the faster, lower-cost model for everyday coding, agent tasks and polished work artifacts, while Opus 5.5 remains the choice for harder open-ended judgment.

Terminal-Bench 4.0: the coding jump

10.3%

Sonnet 5

70.6%

Sonnet 5.5

66.4%

Opus 5.5

Each stacked column is scaled to the reported benchmark score, making the Sonnet 5 to Sonnet 5.5 gain visible at a glance.

30%+

faster output than Sonnet 5

30%

lower task cost in Anthropic testing

token context window

128K

maximum output tokens

How Anthropic splits the lineup

Sonnet 5.5

well-scoped coding, fast iteration, documents and slides

→

Opus 5.5

complex, open-ended work needing sustained judgment

→

Fable 5.1

highest-end general intelligence tier

Why teams like it

Early testers reported fewer steps, faster ticket handling, fewer output tokens and stronger everyday coding results.

Where caution remains

Anthropic still points complex judgment work to Opus 5.5, and high effort can add cost or extra behavior.

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