Claude Sonnet 4.5

Claude Sonnet 4.5 is a Claude family language model released by Anthropic on September 29, 2025. Anthropic positions it as a leading model for coding, building complex agents, and computer use, with substantial gains in reasoning and math compared to Sonnet 4. The model accepts text and image input and produces text output, including code. The default context window is 200,000 tokens and maximum output is 64,000 tokens. The API identifier is claude-sonnet-4-5 (snapshot claude-sonnet-4-5-20250929). It is available via the Claude API, AWS Bedrock, Google Vertex AI, and Microsoft Foundry. Pricing is USD 3 per 1M input tokens and USD 15 per 1M output tokens. Sonnet 4.5 supports extended thinking. Anthropic deployed the model under AI Safety Level 3 (ASL-3) safeguards.