Claude Sonnet 5: Complete Guide to Benchmarks, Pricing, and Features (2026)

Anthropic released Claude Sonnet 5 on June 30, 2026. It is the new default model for the Free and Pro plans, and it is the most agentic Sonnet model the company has shipped. The headline is simple: Sonnet 5 gets close to [Opus 4.8](https://www.aimadetools.com/blog/claude-opus-4-8-complete-guide/?utm_source=devto) on the benchmarks that matter for real work, but it costs a fraction of the price.

I have spent the hours since launch reading the announcement, the system card, and the early partner feedback. Here is everything a developer needs to know before switching.

Quick specs

| Spec | Claude Sonnet 5 |

|------|-----------------|

| API model string | `claude-sonnet-5` |

| Codename | Fennec |

| Release date | June 30, 2026 |

| Context window | 1,000,000 tokens |

| Inputs | Text, image, file |

| Effort levels | low, medium, high, max, x-high |

| Input pricing (intro) | $2 / 1M tokens through Aug 31, 2026 |

| Output pricing (intro) | $10 / 1M tokens through Aug 31, 2026 |

| Input pricing (standard) | $3 / 1M tokens |

| Output pricing (standard) | $15 / 1M tokens |

| Availability | Claude API, Claude Code, Free and Pro default, Amazon Bedrock, Microsoft Foundry, Google Vertex |

What is Claude Sonnet 5?

Sonnet 5 is the latest model in Anthropic's mid-tier Sonnet line, the direct successor to [Sonnet 4.6](https://www.aimadetools.com/blog/claude-sonnet-4-6-vs-opus-4-6/?utm_source=devto). For many developers the agentic era began with Sonnet-class models, since Sonnet 3.5, 3.6, and 3.7 were the first to show strong coding and tool use. Lately the biggest jumps came from the larger Opus models. Sonnet 5 narrows that gap.

Anthropic describes it as built to act, not just answer. It makes plans, drives browsers and terminals, checks its own output without being asked, and runs autonomously for long stretches. That kind of sustained work needed bigger and pricier models only a few months ago.

Benchmarks: how good is Sonnet 5?

The numbers confirm the positioning. Sonnet 5 is a clear improvement over Sonnet 4.6 and lands within striking distance of Opus 4.8.

| Benchmark | Sonnet 5 | Sonnet 4.6 | Opus 4.8 |

|-----------|----------|-----------|----------|

| SWE-bench Pro | 63.2% | lower | 69.2% |

| OSWorld (computer use) | 81.2% | 78.5% | higher |

| SWE-bench Verified | strong | 79.6% | 88.6% |

| GPQA-AAA v2 | slight edge over Opus 4.8 | lower | high |

A few takeaways:

• On SWE-bench Pro, Sonnet 5 reaches 63.2% versus Opus 4.8 at 69.2%. That is close for a model that costs less than half as much.
• On OSWorld, the computer-use benchmark, Sonnet 5 hits 81.2%, a real step up from Sonnet 4.6.
• It actually edges Opus 4.8 on GPQA-AAA v2, a graduate-level reasoning test, which shows how much capability Anthropic packed into the smaller tier.
• It does not beat Opus 4.8 overall. Opus 4.8 still wins on the hardest coding and agentic tasks, especially at higher reasoning effort.

For the full picture of where the flagship still leads, see our [Sonnet