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.
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Model settings
Extended thinking
Max output tokens
Default 65,536 · max 65,536
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Results appear here. Add an image or pick an example to run Claude Fable 5.1.
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Usage
Past 30 DaysVision Evals is Roboflow's ground-truth benchmark: every model runs the same real-world samples across six vision tasks, and answers are scored against ground truth.
Evals updated September 2, 2026Pricing updated September 2, 2026
Claude Fable 5.1 averages 81.3% across the six Vision Evals tasks, ranking #7 of 36 models overall.
It places in the top three for OCR.
Its weakest relative showing is Counting, ranking #12 of 36 at 69.4%.
At $0.035 per sample it is the 36th cheapest of the 36 benchmarked models, and its average inference time of 8.3s per sample makes it the 21st fastest.
Field medians: Object Detection 55.5%, Counting 62.2%, Identification 85.9%, OCR 89.1%, Data Extraction 86.6%, Reasoning 56.6%.
| Task | Score | Field (0 to 100) | Rank | Cost / sample | Speed |
|---|---|---|---|---|---|
| Object Detection (low) | 61.4% ±0.5, Mean of 3 runs, range 61.0 to 62.0 | #7 of 36 | $0.060 | 11.98s | |
| Object Detection (high) | 65.0% ±0.4, Mean of 3 runs, range 64.6 to 65.3 | #5 of 5 | $0.078 | 17.13s | |
| Counting (low) | 69.4% ±2.7, Mean of 3 runs, range 66.2 to 71.6 | #12 of 36 | $0.019 | 5.75s | |
| Counting (high) | 73.0% ±4.7, Mean of 3 runs, range 67.6 to 77.0 | #5 of 5 | $0.023 | 6.53s | |
| Identification (low) | 97.9% ±1.6, Mean of 3 runs, range 96.9 to 100.0 | #5 of 36 | $0.013 | 5.01s | |
| Identification (high) | 96.9% ±3.1, Mean of 3 runs, range 93.8 to 100.0 | #3 of 5 | $0.014 | 4.95s | |
| OCR (low) | 94.0% ±0.4, Mean of 3 runs, range 93.6 to 94.4 | #2 of 36 | $0.039 | 9.76s | |
| OCR (high) | 93.6% ±0.2, Mean of 3 runs, range 93.5 to 93.9 | #1 of 5 | $0.039 | 9.66s | |
| Data Extraction (low) | 93.1% ±0.5, Mean of 3 runs, range 92.8 to 93.8 | #7 of 36 | $0.016 | 4.83s | |
| Data Extraction (high) | 93.5% ±0.5, Mean of 3 runs, range 92.8 to 93.8 | #5 of 5 | $0.016 | 4.83s | |
| Reasoning (low) | 72.0% ±1.3, Mean of 3 runs, range 70.9 to 73.5 | #9 of 36 | $0.019 | 5.94s | |
| Reasoning (high) | 73.1% ±2.0, Mean of 3 runs, range 71.5 to 75.5 | #12 of 36 | $0.028 | 8.05s |
Overall benchmark score against estimated cost per sample, on a log scale. Upper-left is the sweet spot: high quality at low cost.
36 models on the current benchmark · scores and efficiency pooled across all six tasks at low effort · Claude Fable 5.1 highlighted
Claude Fable 5.1 scores are the mean of 3 runs per task at both low and high effort · Methodology
View all Vision Evals →Claude Fable 5.1 costs $10.00 per 1M input tokens and $50.00 per 1M output tokens.
Pricing updated Sep 2, 2026
Other versions in the same family as Claude Fable 5.1.
Claude Fable 5.1 is proprietary: the weights are not distributed, and the Claude Fable 5.1 license is the vendor's commercial terms of service that you accept when you call the API.
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Yes. Claude Fable 5.1 accepts image input and handles OCR, data extraction, object counting, identification, visual reasoning, and object detection. On Roboflow's Vision Evals its strongest task is OCR at 94% (#2 of 36 at low effort). You can test it on your own image in the demo above.
Yes, and it is one of the model's strongest vision skills: its transcriptions match the ground truth 94% on average (#2 of 36 at low effort) on Vision Evals OCR. Pulling specific fields out of documents (data extraction) scores 93.1%.
It's serviceable. On Vision Evals, Claude Fable 5.1 scores 61.4% mAP@50 on object detection (#7 of 36 at low effort) and 69.4% judge-graded accuracy on object counting.
On our benchmark's task mix, Claude Fable 5.1 averages $0.04 per sample at $10.00 per 1M input and $50.00 per 1M output tokens (#36 of 36 on cost), with an average speed of 8.3s per sample across the benchmark. Actual cost depends on your images and prompts.
On the overall Vision Evals ranking, Claude Fable 5.1 sits #7 of 36 at 81.3%, just behind Gemini 3.6 Flash (83%) and just ahead of Muse Spark 1.2 (80.6%). See the full side-by-side: Claude Fable 5.1 vs Gemini 3.6 Flash.