What Claude Sonnet 4's million-token context enabled
The August 2025 API beta increased capacity, with separate pricing and availability conditions.
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Anthropic announced a one-million-token context window for Claude Sonnet 4 on August 12, 2025. The API feature expanded how much material a request could include, compared with the model's 200,000-token window [1].
Capacity has conditions
The announcement described a public beta for eligible API customers, including Tier 4 and custom-rate-limit accounts. It also listed different pricing for prompts above 200,000 tokens [1]. This was not a promise that every Claude subscription suddenly had the same capacity at the same price.
Our carousel's description of infinite context was figurative. One million tokens is a defined limit, and the announcement does not establish that it was the largest context window across every competing system.
More context still needs selection
A larger window can help when relevant information spans many files or documents. It does not make every included sentence equally useful.
For a repository question, start with the files needed to answer it and add missing dependencies deliberately. Compare the answer against the code and tests. If a larger request improves the result, weigh that improvement against its cost and response time.
These are the terms of the 2025 announcement. Check current model documentation for availability and pricing before using it today.
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