Claude Sonnet 5

Claude Sonnet 5 scores 82.1% on SWE-bench Verified and 46%+ on SWE-bench Pro, while GPT-5.4 scores 57.7% on SWE-bench Pro with comparable Verified scores around 85%. For most coding workflows, Sonnet 5 delivers a stronger autonomous code-editing experience, but GPT-5.4’s reasoning levels give it an edge in cost-flexibility for high-stakes reasoning tasks. What Is the SWE-bench Benchmark and Why Does It Matter for Coding? SWE-bench is the most respected real-world coding benchmark in 2026, built from actual GitHub issues submitted to production Python repositories including Django, Flask, and Scikit-learn. Unlike HumanEval — which tests isolated function writing and is now saturated at 95%+ for frontier models — SWE-bench requires a model to read a bug report, navigate a real codebase, write a patch, and pass the repository’s own test suite. This means the benchmark tests the full software engineering loop, not just code generation from a clean prompt. SWE-bench Verified contains 500 human-validated tasks, while SWE-bench Pro uses harder tasks from private and less-contaminated repositories. As of May 2026, Claude Sonnet 5 holds an 82.1% SWE-bench Verified score (the first model to break the 80% barrier) and GPT-5.4 leads SWE-bench Pro at 57.7%, reflecting fundamentally different strengths: Sonnet 5 excels at agentic, autonomous patch generation, while GPT-5.4 integrates broader reasoning and computer-use capabilities in a single model. ...

Claude Sonnet 5 is Anthropic’s mid-tier frontier model released February 3, 2026, scoring 82.1% on SWE-bench Verified — the highest coding benchmark score ever recorded at launch. It introduces Dev Team multi-agent mode, a 1 million token context window, and holds the same $3 per million input token price as its predecessor. For most development teams, it’s the most capable coding model available at a non-flagship price. What Is Claude Sonnet 5? (Fennec Model Overview & Release Details) Claude Sonnet 5 — internally codenamed “Fennec” after the large-eared desert fox — is Anthropic’s third-generation Sonnet model and the first AI model to break the 80% ceiling on SWE-bench Verified. It was officially released on February 3, 2026, simultaneously across the Anthropic API, Amazon Bedrock, and Google Vertex AI, with the identifier claude-sonnet-5@20260203 first spotted in Vertex AI deployment logs days before the announcement. The codename Fennec is not arbitrary marketing: it nods to the model’s 1 million token context window — metaphorically “large ears” for listening to entire codebases. Unlike Claude Opus 4.7, which targets deep multi-step reasoning at a premium price, Sonnet 5 is positioned as the workhorse model for engineering teams who need frontier-grade coding capability without flagship-grade cost. It replaced Claude Sonnet 4.6 as the default model for Claude Code Free and Pro users on launch day. The model runs on Google’s Antigravity TPU infrastructure, which Anthropic credits for the latency improvements over Sonnet 4.6. For API users, the migration path from claude-sonnet-4-6 to claude-sonnet-5 is a one-line model ID change — same tool format, same system prompt conventions. ...