Claude Sonnet 4.5 vs Claude Fable 5.1
Compare Claude Sonnet 4.5 and Claude Fable 5.1 side-by-side. See how these vision models stack up in Object Detection, Classification, Image Captioning, OCR, and Open Prompt.
Compare Claude Sonnet 4.5 vs Claude Fable 5.1 live
Run the same image across every model that supports a task and compare their outputs side-by-side.
Detect and compare bounding boxes across models on the same image.
Upload an image
Drag and drop an image here, or click to browse
Models in this comparison
Claude Sonnet 4.5 vs Claude Fable 5.1 Comparison Table
Evals updated September 2, 2026Pricing updated September 2, 2026
| Property | Claude Sonnet 4.5 | Claude Fable 5.1 |
|---|---|---|
| Organization | Anthropic | Anthropic |
| Category | closed | closed |
| Modality | multimodal | multimodal |
| Release Date | Sep 2025 | Sep 2026 |
| Context Window | 200K | 1.0M |
| Parameters | ||
| License | Proprietary | Proprietary |
| Pricing per 1M tokens | ||
| Input $/1M | $3.00 | $10.00 |
| Output $/1M | $15.00 | $50.00 |
| Vision Tasks | ||
| Captioning | Demo | Demo |
| Chart Question Answering | ||
| Classification | Demo | Demo |
| Document Question Answering | ||
| Image Tagging | ||
| Multi-Label Classification | ||
| Object Detection | Demo | Demo |
| OCR | Demo | Demo |
| Vision Language | ||
| Visual Question Answering | Demo | Demo |
| Model Features | ||
| Foundation Vision | ||
| LLMs with Vision Capabilities | ||
| Multimodal Vision | ||
Vision Evalsground-truth scores across 6 vision tasks, pooled at low effort | ||
| Overall | Not evaluated | 81.3% |
| Avg cost / sample | – | $0.035 |
| Avg speed / sample | – | 8.28s |
| By task | ||
| Object Detection (low) | – | 61.4% ±0.5, Mean of 3 runs, range 61.0 to 62.0 |
| Object Detection (high) | – | 65.0% ±0.4, Mean of 3 runs, range 64.6 to 65.3 |
| Counting (low) | – | 69.4% ±2.7, Mean of 3 runs, range 66.2 to 71.6 |
| Counting (high) | – | 73.0% ±4.7, Mean of 3 runs, range 67.6 to 77.0 |
| Identification (low) | – | 97.9% ±1.6, Mean of 3 runs, range 96.9 to 100.0 |
| Identification (high) | – | 96.9% ±3.1, Mean of 3 runs, range 93.8 to 100.0 |
| OCR (low) | – | 94.0% ±0.4, Mean of 3 runs, range 93.6 to 94.4 |
| OCR (high) | – | 93.6% ±0.2, Mean of 3 runs, range 93.5 to 93.9 |
| Data Extraction (low) | – | 93.1% ±0.5, Mean of 3 runs, range 92.8 to 93.8 |
| Data Extraction (high) | – | 93.5% ±0.5, Mean of 3 runs, range 92.8 to 93.8 |
| Reasoning (low) | – | 72.0% ±1.3, Mean of 3 runs, range 70.9 to 73.5 |
| Reasoning (high) | – | 73.1% ±2.0, Mean of 3 runs, range 71.5 to 75.5 |
Claude Sonnet 4.5 vs Claude Fable 5.1: Overview
Claude Sonnet 4.5, released by Anthropic in September 2025, is the company’s most advanced Sonnet-series model, built for high-performance reasoning, coding, and long-horizon agentic workflows. It is a multimodal system that accepts both text and images, with a 200,000-token context window designed for handling large documents and extended interactions. Anthropic highlights its improvements in reliability, reduced sycophancy, and alignment, making it suitable for sustained enterprise use.
The model delivers strong results in coding and autonomous workflows, achieving 61.4% on the OSWorld benchmark and leading performance on SWE-bench Verified. It introduces infrastructure features such as a memory tool (beta), checkpointing for Claude Code, parallel tool use, and tighter integration with VS Code. Compared to Opus, which targets broader reasoning, Sonnet 4.5 is optimized for structured, long-duration tasks. Positioned against leading offerings from OpenAI and Google, it is aimed at enterprise automation, software engineering, and research-intensive applications.
Claude Fable 5.1 is a proprietary multimodal model from Anthropic in the Mythos-class tier of the Claude 5 family, positioned above Claude Opus for demanding reasoning and long-horizon agentic work. It accepts text and images as input and returns text, with a one million token context window and a maximum output of 128 thousand tokens. Adaptive thinking is always on, and an effort parameter controls how much reasoning the model applies to a given request. Anthropic reports a reliable knowledge and training data cutoff of June 2026. Claude Fable 5.1 and Claude Mythos 5.1 share the same underlying model; the difference between them is the set of safety classifiers applied to dual-use cybersecurity and biology requests.
On the vision side, Anthropic documents improvements in reading dense charts, financial filings, and tables nested inside PDF documents, which extends the model toward document understanding, chart question answering, and spreadsheet and slide work. Reported evaluations cover agentic scientific research on Terminal-Bench-Science 0.1, agentic coding on Terminal-Bench 4.0, computer use on OSWorld 2.0, and multidisciplinary reasoning on Humanity's Last Exam. Model weights are not published.
Frequently Asked Questions
Claude Sonnet 4.5 has not yet been evaluated on Roboflow's current Vision Evals, so this comparison shows specs, licensing, and pricing rather than benchmark scores.
Yes. The comparison demo on this page runs both models on the same image side by side for object detection and image classification in the free Roboflow Playground. You can try it instantly, and a free account unlocks unlimited runs.