Kimi K3.1 Pro vs Claude Fable 5.2: Benchmarks, Pricing, and Key Differences
Moonshot AI and Anthropic released two powerful AI models within weeks of each other: Kimi K3.1 Pro in October 2026 and Claude Fable 5.2 in November 2026.
Both models are designed for demanding workloads, including agentic coding,
research, and complex knowledge work. However, they target different markets. Kimi K3.1 Pro is an open-weight model that costs significantly less, while Claude Fable 5.2 is a closed model with stronger reported performance across several advanced benchmarks.
In this article, we'll compare Kimi K3.1 Pro and Claude Fable 5.2 across benchmarks, coding capabilities, reasoning, pricing, availability, and practical use cases to help you decide which model is worth choosing.
What Is Kimi K3.1 Pro?
Kimi K3.1 Pro is Moonshot AI's flagship model, released on October 23, 2026. It is an improved version of Kimi K3, a 2.8-trillion-parameter Mixture-of-Experts (MoE) model with approximately 104 billion active parameters per token.
The architecture remains unchanged, while the improvements come from additional reinforcement learning across hundreds of task domains.
Key specifications include:
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Moonshot released the model weights on November 4, 2026, under its custom license. This allows developers to download and deploy the model, although its large size requires substantial computing infrastructure.
What Is Claude Fable 5.2?
Claude Fable 5.2 is Anthropic's most capable generally available model, released on November 9, 2026.
It sits above Claude Opus 5.5 and is designed for demanding technical tasks, including large software migrations, long-running agent workflows, and complex research problems.
Its key specifications include:
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Anthropic also offers Claude Mythos 5.2, a version with different cybersecurity and biology safeguards, for selected verified organizations.
Unlike Kimi K3.1 Pro, Fable 5.2 is a closed model. However, it is available through Amazon Web Services, Google Cloud, and Microsoft Azure.
Kimi K3.1 Pro vs Claude Fable 5.2: Head-to-Head Comparison
There is no shared benchmark leaderboard directly comparing these two models. Anthropic's published results compare Fable 5.2 against Claude Opus 5.5, while Moonshot's results compare Kimi K3.1 Pro against Fable 5.1 and Opus 5.5.
The following comparison uses Opus 5.5 as a reference point across the two vendors' reported evaluations.
Benchmark | Kimi K3.1 Pro | Opus 5.5 (Moonshot) | Claude Fable 5.2 | Opus 5.5 (Anthropic) |
Humanity's Last Exam (with tools) | 70.0% | 67.7% | 74.2% | 67.7% |
Terminal-Bench-Science 0.1 | 38.1% | 63.3% | 74.6% | 58.7% |
OSWorld 2.1 | 79.6% | 81.8% | 89.3% | 87.2% |
The results need careful interpretation because the two companies use different testing setups. Even their reported Opus 5.5 scores differ on some benchmarks.
Agentic coding performance
Both models are designed for complex coding tasks, but their reported results show different strengths.
Moonshot's evaluations indicate that Kimi K3.1 Pro performs close to Opus 5.5 on Terminal-Bench 4.0, scoring 65.7% compared with 66.4%. It also leads on SWE-Marathon, a benchmark for multi-hour engineering tasks, with 51.7% against Opus 5.5's 46.3%.
However, Kimi falls behind on ProgramBench, scoring 31.5% compared with Opus 5.5's 65.0%.
Anthropic's evaluations show Fable 5.2 outperforming Opus 5.5 on both of its reported coding benchmarks:
Benchmark | Claude Fable 5.2 | Claude Opus 5.5 |
FrontierCode 2.0 | 49.1% | 45.5% |
FrontierSWE v2 | 69.9% | 62.3% |
Overall, Kimi K3.1 Pro delivers competitive coding performance, particularly on longer engineering tasks. Fable 5.2 appears stronger across the reported coding evaluations, although direct independent testing is still needed.
Reasoning, research, and office work
Claude Fable 5.2 has a clear advantage in advanced reasoning and scientific work.
Its performance on Humanity's Last Exam and Terminal-Bench-Science indicates stronger capabilities in complex research and technical problem-solving. Kimi K3.1 Pro scores 38.1% on Terminal-Bench-Science, considerably below Opus 5.5 in Moonshot's own comparison.
However, Kimi remains competitive in web research and document analysis.
Benchmark | Kimi K3.1 Pro | Claude Opus 5.5 |
BrowseComp | 92.1% | 90.8% |
OfficeQA Pro | 64.4% | 62.2% |
Kimi performs better on both reported evaluations. BrowseComp measures the ability to find difficult information online, while OfficeQA Pro evaluates financial document analysis.
Anthropic has not published equivalent Fable 5.2 results for these benchmarks, so a direct comparison with Fable 5.2 is not available.
Hallucination and 3D modeling
Moonshot also reports results in hallucination testing and 3D modeling.
Hallucination: On Moonshot's internal Kimi Hallu Bench, K3.1 Pro records a 5.4% false-claim rate without tools, compared with 11.4% for Claude Fable 5.1. These are vendor-reported results, and no equivalent Fable 5.2 result is provided.
3D modeling: On BenchCAD, Kimi K3.1 Pro and Fable 5.1 achieve nearly identical results with tools, scoring 92.7 and 92.6 respectively. Anthropic reports improvements for Fable 5.2 on a different version of the benchmark, so the results cannot be directly compared.
These evaluations highlight Kimi's strengths, although more independent testing is needed to establish how it compares with Fable 5.2.
Open Weights and Safety
One of the biggest differences between the models is how they are distributed.
Kimi K3.1 Pro offers open weights through Hugging Face. Developers can download the model, deploy it on their own infrastructure, and explore fine-tuning options.
However, the model checkpoint is approximately 1.56 TB, requiring a multi-GPU server rather than a standard workstation. Developers should also review Moonshot's custom license before using it commercially.
Claude Fable 5.2 is a closed model. Users cannot download its weights or independently deploy the underlying model, but it is accessible through Anthropic and major cloud platforms.
Their cybersecurity safeguards also differ:
Moonshot removed cybersecurity-related training data before releasing K3.1 Pro's weights, reducing its score on an internal exploit benchmark from 90.5% to 81.0%.
Anthropic retains Fable 5.2's broader capabilities but restricts most offensive cybersecurity and research-level biology requests. Eligible organizations can access Claude Mythos 5.2 under separate safeguards.
For organizations prioritizing infrastructure control and model customization, Kimi offers more flexibility. Fable 5.2 is more suitable for teams that prefer a managed model service.
Kimi K3.1 Pro vs Claude Fable 5.2 Pricing
Pricing is one of Kimi K3.1 Pro's biggest advantages. Its standard input and output rates are approximately one-quarter of Fable 5.2's prices.
Token pricing
Pricing per 1M tokens | Kimi K3.1 Pro | Claude Fable 5.2 |
Input | $2.00 | $8.00 |
Output | $10.00 | $40.00 |
Cached input reads | $0.20 | $0.20 |
5-minute cache writes | $2.00 | $10.00 |
Faster variant | Highspeed: $4 / $20 | Fast mode: $16 / $80 |
Batch discount | Not listed | 50% |
For a workload involving 1 million input tokens and 250,000 output tokens, the estimated cost is:
Kimi K3.1 Pro: $4.50
Claude Fable 5.2: $18.00
There are a few pricing differences worth considering:
Cached input reads cost the same for both models.
Fable 5.2 offers a 50% batch discount for eligible workloads.
Kimi's Highspeed variant costs more than its standard version.
Different tokenizers mean identical text may produce different token counts across the two models.
Despite these differences, Kimi K3.1 Pro remains considerably cheaper for many high-volume workloads.
When to Choose Kimi K3.1 Pro vs Claude Fable 5.2
Both models have their strengths, and the right choice depends on your workload, budget, and infrastructure requirements.
Choose Kimi K3.1 Pro if:
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Choose Claude Fable 5.2 if:
You need stronger performance in complex reasoning and scientific research.
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For teams that find Fable 5.2 too expensive, Claude Opus 5.5 is another option. It costs $4 per million input tokens and $20 per million output tokens, making it twice as expensive as Kimi K3.1 Pro but less expensive than Fable 5.2.
Conclusion
Claude Fable 5.2 is the stronger model across several reported benchmarks, particularly in reasoning, scientific work, and computer use. However, Kimi K3.1 Pro remains a competitive alternative for coding, research, and long-running engineering tasks.
The biggest advantage of Kimi is its pricing and open-weight availability. At approximately one-quarter of Fable 5.2's standard token cost, it offers an attractive option for developers and businesses managing large AI workloads.
Ultimately, Fable 5.2 is better suited to teams prioritizing maximum model performance, while Kimi K3.1 Pro is a compelling choice for those seeking lower costs, greater infrastructure control, and competitive capabilities.
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