Claude Sonnet 5 vs GPT-5.4

Claude Sonnet 5 and GPT-5.4 are both available through FastRouter's OpenAI-compatible API, so switching between them is a change of model id, not a new integration.

Claude Sonnet 5, from Anthropic, has a 1,000,000-token context window, costs from $2.00/1M input and $10.00/1M output tokens across 2 providers and scores 38.2 on the Artificial Analysis Intelligence Index.

GPT-5.4, from OpenAI, has a 1,050,000-token context window, costs from $2.50/1M input and $15.00/1M output tokens across 2 providers and scores 39.0 on the Artificial Analysis Intelligence Index.

Claude Sonnet 5 is the cheapest on input, 1.3× cheaper than the next model, GPT-5.4 has the largest context window, GPT-5.4 scores highest for intelligence, Claude Sonnet 5 leads on coding and Claude Sonnet 5 has the highest throughput.