Anthropic: Claude Sonnet 4.5

What separates this model from the obvious alternatives is a coding focus backed by benchmark evidence rather than marketing: it is tuned for real-world agents and coding workflows and cites state-of-the-art results on SWE-bench Verified. For a developer running an agent that reads a large repository, plans a multi-file change and executes it, the 1,000,000-token context window holds the codebase, chain-of-thought reasoning works through the plan, and tool calling with structured JSON output drives the execution loop. Vision handles diagrams and screenshots, and the 2025-01-31 knowledge cutoff marks its unaided boundary. Set beside its alternatives the positioning is coding-first at a mid price: at $3.00 per 1M input tokens it undercuts the $5.00 general ChatGPT and Sakana Fugu Ultra tiers while matching their 1M window, and against the broader Claude and Gemini assistants it is the model tuned specifically for agentic coding rather than general chat. The above-average API price relative to the cheapest options is the stated caveat, and there is no free tier. The SWE-bench grounding gives its coding claim more weight than a generic capability list. Ideal for research and writing users, and especially engineering teams, who need dependable agentic coding over large codebases. Choose it when verified coding performance and agent reliability lead your decision; look to a general assistant or a cheaper Flash-class model if broad chat or minimal cost matters more than coding strength.