Claude Sonnet 5.5 Context Window: 1 Million Token Capacity

Update (9 Nov 2026): Claude Fable 5.2 and Mythos 5.2 are out - prices, access and benchmarks are in my Claude Fable 5.2 guide.

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Claude Sonnet 5.5 provides a context window of 1,000,000 tokens, which represents the total amount of information the model can process in a single interaction. This includes both the input you provide and the output the model generates, combined. The context window became available when the model launched on OpenRouter on September 28, 2026.

What 1 Million Tokens Means in Practice

A context window of 1,000,000 tokens translates to roughly 750,000 words of English text, though this varies based on language and content type. This capacity handles multiple full-length books, extensive codebases, or long conversation histories without truncation. For document analysis, you could process several hundred pages of technical documentation in a single request.

Claude Sonnet 5.5’s context capacity matches Claude Sonnet 5 and GLM 5.3 Prime exactly at 1,000,000 tokens. Gemini 3.5 Flash offers slightly more at 1,048,576 tokens, while GPT-5.6 Sol Pro provides 1,050,000 tokens. These differences are marginal - the 50,000 token gap between Claude Sonnet 5.5 and GPT-5.6 Sol Pro represents only 5% more capacity.

The model accepts text, image, and file inputs according to its specification card. Different input types may consume tokens at different rates, with images and files potentially using more tokens than equivalent information in plain text. Users should monitor actual token consumption when working with mixed media inputs.

For most applications, 1,000,000 tokens provides ample room for complex tasks. The practical limit is rarely the context window itself but rather the cost of processing large token volumes at $2 input and $10 output per million tokens.

// read moreClaude Sonnet 5.5 Price: Cost per Million Tokens in 2026BenchmarksClaude Sonnet 5.5: Pricing, Benchmarks, and Tested PerformanceNewsClaude Sonnet 5.5 vs GPT-5.6 Sol Pro: Which Model to ChooseBenchmarks

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