The global developer community is abuzz over a "historical" leak. Multiple pieces of evidence indicate that Anthropic's next-generation programming large model, Claude Sonnet5 (codename Fennec), has appeared in Google Cloud infrastructure and is expected to be officially released in early February 2026. This masterpiece, humorously dubbed "packing the entire development team into the model," is declaring the peak of programming AI with its extremely impressive performance metrics.

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This leak originated from a 404 error log triggered accidentally when developers called an API, revealing that the model has already been deployed. Preliminary evaluation data shows that Sonnet5 performs remarkably in handling complex UI rendering and structured visual generation tasks. More unsettling for competitors is that although it is positioned as a mid-range "Sonnet" series, in multiple internal benchmark tests, its overall performance has fully surpassed its own top flagship model, Claude Opus4.5.

The core killer feature of Sonnet5 is its powerful "Swarm Mode (Agent Swarm)." In Dev Team development mode, the model can automatically split tasks according to requirements and generate multiple sub-intelligences (such as front-end development, back-end development, QA testing, etc.) in the background to work in parallel. This means it is no longer just a plugin that assists in writing code, but a digital R&D team that can autonomously organize, self-iterate, and never take a break.

To completely address developers' pain points about large models being expensive and slow, Sonnet5 has been deeply optimized using Google's TPU. Its inference cost has significantly decreased, with a price that is only 50% of Opus4.5, while offering a context window of up to 1 million tokens. In response to OpenAI's upcoming Codex suite, Anthropic's move clearly carries a "direct confrontation" spirit, and the productivity paradigm of software engineering may soon undergo a complete transformation.

Key Points:

  • 🚀 Unprecedented Challenge: The Sonnet5, codenamed Fennec, outperforms the flagship Opus4.5 and scores over 80.9% on the SWE-Bench programming benchmark test.

  • 🤖 Swarm Collaboration: It introduces the "automatic development team" mode, capable of autonomously generating and scheduling multiple sub-intelligences to work in parallel, achieving full delivery from requirements to features.

  • 💸 Exceptional Cost-Effectiveness: The price is cut in half by 50%, with a super long context window of 1 million tokens, faster operation speed, and lower latency.