# Claude Sonnet 4.5

Claude Sonnet 4.5 is an AI model released by Anthropic on Sep 29 2025. Tracked results include 79% on BullshitBench v2, 83.4% on GPQA Diamond and 77.2% on SWE-Bench Verified.

## Facts

| Field | Value |
| --- | --- |
| Model | Claude Sonnet 4.5 |
| Developer | Anthropic |
| Release date | Monday, Sep 29 2025 |
| Licensing | Proprietary |

## API pricing

All rates in USD per 1,000,000 tokens, pay-as-you-go.

| Tier | Input | Cached input | 5 min cache write | 1 hr cache write | Output |
| --- | --- | --- | --- | --- | --- |
| All documented contexts | $3.00 | $0.30 | $3.75 | $6.00 | $15.00 |

Verified August 18, 2026 against the first-party source: https://platform.claude.com/docs/en/about-claude/pricing

## Tracked benchmark scores

| Benchmark | Score | Source | What it measures |
| --- | --- | --- | --- |
| BullshitBench v2 | 79% | [BullshitBench](https://github.com/petergpt/bullshit-benchmark) | Given a confidently-worded but nonsensical prompt, does the AI spot that it makes no sense and push back — instead of playing along and inventing an answer? The score is how often it clearly called out the nonsense. Higher is better. |
| SWE-Bench Verified | 77.2% | Lab | Real coding tasks pulled from open-source projects — the AI has to find and fix actual bugs. A human-checked version of the original SWE-Bench. Higher is better. |
| Next.js Evals | 39% | [Next.js Evals](https://nextjs.org/evals) | Vercel's open eval of how well AI coding agents build and migrate real Next.js apps — measured as the share of tasks the agent completes successfully. Higher is better. |
| ARC-AGI-2 | 13.6% | [BenchLM](https://benchlm.ai), retrieved 2026-08-31 | Puzzle-style tests of abstract reasoning and pattern-finding — the kind of thing people find easy but AIs often struggle with. Higher is better. |
| GPQA Diamond | 83.4% | Lab | Graduate-level science questions in biology, physics, and chemistry — hard enough that subject-matter PhDs score around 65%. Higher is better. |
| OSWorld-Verified | 61.4% | [BenchLM](https://benchlm.ai), retrieved 2026-08-31 | Can the AI actually operate a computer — clicking, typing, and using real apps — to finish tasks on its own? Higher is better. |
| MMMU | 68% | Lab | Tests the AI on understanding images and text together across many college subjects. Higher is better. |

## About Claude Sonnet 4.5

Claude Sonnet 4.5, released September 29, 2025, was introduced by Anthropic as the best coding model in the world at the time. It reached 77.2% on SWE-Bench Verified and 83.4% on GPQA Diamond, and it was built for autonomy: Anthropic reported it could work productively on complex, multi-step tasks for many hours without losing the thread — the capability that underpinned the Claude Agent SDK, released the same day.

Beyond raw scores, Sonnet 4.5 marked the point where the mid-tier Sonnet line overtook the previous flagship Opus 4.1 on software-engineering benchmarks while remaining far cheaper, a pattern that repeated across the industry as labs pushed agentic training into smaller models. It was succeeded at the top of the coding leaderboards by Claude Opus 4.5 in November 2025.

## Questions and answers

### When was Claude Sonnet 4.5 released?

Claude Sonnet 4.5 was released by Anthropic on Monday, Sep 29 2025.

### Who made Claude Sonnet 4.5?

Claude Sonnet 4.5 was built by Anthropic. AI safety company building the Claude family of models. Founded in 2021 by former OpenAI researchers.

### How much does Claude Sonnet 4.5 cost?

Claude Sonnet 4.5 costs $3.00 per million input tokens and $15.00 per million output tokens through the Anthropic API. Cached input is $0.30 per million tokens. Rates are pay-as-you-go API prices verified against Anthropic's published pricing on August 18, 2026.

### What benchmark scores did Claude Sonnet 4.5 get?

Claude Sonnet 4.5 reports 7 tracked benchmark scores — BullshitBench v2: 79%; SWE-Bench Verified: 77.2%; Next.js Evals: 39%; ARC-AGI-2: 13.6%; GPQA Diamond: 83.4%; OSWorld-Verified: 61.4%; MMMU: 68%. Tracked scores may come from lab reports or independent benchmarks; source details accompany the benchmark data.

### Is Claude Sonnet 4.5 open source?

No. Claude Sonnet 4.5 is a proprietary model. The weights are not published — it is available only through the provider's own API, apps, or partner platforms.

### What came before and after Claude Sonnet 4.5?

Anthropic's previous tracked release was Claude Opus 4.1 on Aug 5 2025, 55 days earlier. It was followed by Claude Haiku 4.5 on Oct 15 2025.


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Canonical page: https://aireleasetracker.com/model/anthropic/claude-sonnet-4.5
Full dataset: https://aireleasetracker.com/llms-full.txt · JSON: https://aireleasetracker.com/models.json
Source: AI Release Tracker (https://aireleasetracker.com). Most benchmark scores come from lab launch material; gathered results identify the leaderboard that published them.