Anthropic released Claude Sonnet 5 with a 1 million token context window and headline pricing matching Sonnet 4.6. However, the new tokenizer produces approximately 30% more tokens for the same input text, creating an effective 30% price increase despite lower list rates. The model performs close to the more expensive Opus 4.8 but is significantly less capable at cyber tasks than Mythos 5, allowing Anthropic to release it without US government delays.
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Anthropic released Claude Sonnet 5, a new AI model with performance close to its more expensive Opus 4.8 variant. The model has a 1 million token context window and 128,000 maximum output tokens. However, the new tokenizer produces approximately 30% more tokens than Claude Sonnet 4.6 for the same input, effectively raising the price by 30% despite list pricing remaining at $3/million input and $15/million output (with an introductory discount to $2/$10 through 31st August).
Why it matters
Sonnet 5 offers high performance at lower list prices, but the tokenizer change means real-world costs are higher than they appear. The model is less capable at cyber tasks than Anthropic's more powerful Mythos 5, which allowed the company to release it without US government restrictions. For developers and businesses using Claude, the effective price increase may offset the appeal of lower headline rates.
What to watch
The tokenizer efficiency varies by language—English text costs 1.42× more per token than Sonnet 4.6, Spanish 1.33×, Python code 1.27×, and Simplified Mandarin roughly the same. Adaptive thinking is enabled by default, and the model uses the same tools and platform features as Claude Sonnet 4.6.
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