Claude Sonnet 5 leak reveals one-million-token context and imminent Anthropic release
Anthropic is preparing to release Claude Sonnet 5, a new mid-tier AI model that could reshape the large language model market. Leaked references found in Google Vertex AI logs point to a February 3, 2026 launch, with the model codenamed Fennec showing a one-million-token context window, 50% lower cost than Opus 4.5, and TPU-based training for faster inference speeds.