Claude Fable 5.1 vs Claude Opus 5.5
Claude Opus 5.5 and Claude Fable 5.1 score 82.0% vs 74.7% averaged across five Vision Evals tasks (#5 and #17 of 67 models), so Claude Opus 5.5 leads overall.
- Claude Opus 5.5 wins 4 of the 5 tasks, with its widest lead on object detection (74.5% vs 61.4%).
- Claude Opus 5.5 is about a third of the cost: $0.015 vs $0.039 overall average cost per sample.
- Claude Opus 5.5 is faster: 7.6s vs 8.3s per sample.
Roboflow Vision Evals. Full breakdown below.
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Claude Fable 5.1 vs Claude Opus 5.5 on Vision Evals
Roboflow Vision Evals. Full breakdown below.
Claude Fable 5.1 vs Claude Opus 5.5 Comparison Table
Evals updated November 10, 2026Pricing updated November 10, 2026
| Property | Claude Fable 5.1 | Claude Opus 5.5 |
|---|---|---|
| Organization | Anthropic | Anthropic |
| Category | closed | closed |
| Modality | multimodal | multimodal |
| Release Date | Sep 2026 | Sep 2026 |
| Context Window | 1.0M | 1.0M |
| Parameters | Unknown | Unknown |
| License | Proprietary | Proprietary |
| Commercial use | commercial use per vendor terms | commercial use per vendor terms |
| Pricing per 1M tokens | ||
| Input $/1M | $10.00 | $4.00 |
| Output $/1M | $50.00 | $20.00 |
| Vision Tasks | ||
| Model Features | ||
Both support 3 more features | ||
Vision Evalsground-truth scores across 5 vision tasks, pooled at low effort | ||
| Overall | 74.7% | 82.0% |
| Avg cost / sample | $0.039 | $0.015 |
| Avg speed / sample | 8.35s | 7.63s |
| By task | ||
| Object Detection (low) | 61.4% ±0.5, Mean of 3 runs, range 61.0 to 62.0 | 74.5% ±0.5, Mean of 3 runs, range 74.0 to 75.0 |
| Object Detection (high) | 65.0% ±0.4, Mean of 3 runs, range 64.6 to 65.3 | 76.0% ±1.1, Mean of 3 runs, range 74.7 to 77.0 |
| Counting (low) | 69.4% ±2.7, Mean of 3 runs, range 66.2 to 71.6 | 80.6% ±2.0, Mean of 3 runs, range 78.4 to 82.4 |
| Counting (high) | 73.0% ±4.7, Mean of 3 runs, range 67.6 to 77.0 | 82.0% ±2.0, Mean of 3 runs, range 79.7 to 83.8 |
| Identification (low) | 97.9% ±1.6, Mean of 3 runs, range 96.9 to 100.0 | 93.8% ±0.0, Mean of 3 runs, range 93.8 to 93.8 |
| Identification (high) | 96.9% ±3.1, Mean of 3 runs, range 93.8 to 100.0 | 95.8% ±1.6, Mean of 3 runs, range 93.8 to 96.9 |
| OCR (low) | 72.9% | 78.3% |
| by category |
|
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| OCR (high) | 75.3% | 79.9% |
| by category |
|
|
| Reasoning (low) | 72.0% ±1.3, Mean of 3 runs, range 70.9 to 73.5 | 83.0% ±1.0, Mean of 3 runs, range 82.1 to 84.1 |
| Reasoning (high) | 73.1% ±2.0, Mean of 3 runs, range 71.5 to 75.5 | 85.9% ±2.6, Mean of 3 runs, range 82.8 to 88.1 |
Claude Fable 5.1 vs Claude Opus 5.5: Overview
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. Model weights are not published.
Claude Opus 5.5 is a proprietary multimodal reasoning model from Anthropic and the first entry in the Claude 5.5 family. It accepts interleaved text and image input and returns text, with a one million token context window and up to 128,000 output tokens per response. Adaptive thinking is always enabled on this model and cannot be disabled; thinking depth is instead governed by an effort parameter with five levels, where medium is the default, a change from the high default used by Claude Opus 5 and earlier Opus models. Anthropic reports a knowledge cutoff of June 2026.
On the visual side, Anthropic characterizes Opus 5.5 as its strongest Opus release for vision and computer use, describing improved reading of dense documents, charts, screenshots, and diagrams for document extraction and visual analysis tasks. The accompanying system card states that Opus 5.5 scored higher than Opus 5 on every evaluation in its capability summary, with the largest gains concentrated in agentic coding, visual reasoning, computer use, and long-horizon knowledge work. The model ships with safety classifiers covering biology and cybersecurity that can route blocked requests to earlier Claude models.