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Claude Sonnet 5.5 vs Kimi K3.1 Pro

Claude Sonnet 5.5 and Kimi K3.1 Pro are closely matched at 57.9 and 55.5 on the LLM Stats Score. Claude Sonnet 5.5 and Kimi K3.1 Pro cost the same.

Anthropic · Moonshot AI · Updated for 2026

Which is better?

Claude Sonnet 5.5 and Kimi K3.1 Pro are closely matched on the overall LLM Stats Score at 57.9 and 55.5.

In the 10 individual benchmarks reported for both models, Claude Sonnet 5.5 wins 6; this is a narrower head-to-head signal than the composite indexes.

Kimi K3.1 Pro also accepts a larger context window (1,048,576 input tokens), making it the stronger choice for long documents and large codebases.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Claude Sonnet 5.5

  • you value its reported benchmark strengths — it wins 6 of 10 exact shared results

Choose Kimi K3.1 Pro

  • you process long inputs — it offers a 1,048,576 token context window
  • you want the most recent training data — it shipped Oct 2026

At a glance

The differences that matter most.

Claude Sonnet 5.5
Anthropic
Kimi K3.1 Pro
Moonshot AI
Core performance indexes
LLM Stats Score
57.9
#3
55.5
#5
Reasoning
56.2
#2
54.3
#6
Coding
48.5
#2
42.7
#9
Agents
43.8
#4
41.6
#5
Cost, coverage & limits
Benchmark wins
6 of 10
4 of 10
Input price
$2.00 / M
$2.00 / M
Output price
$10.00 / M
$10.00 / M
Context window
1,000,000
1,048,576

Capability indexes

Additional strengths measured across groups of related public benchmarks

4 shared
Index
Claude Sonnet 5.5
Kimi K3.1 Pro
Math
38.1#28
38.6#26
Vision
39.8#6
40.5#4
Tool use
36.2#2
30.4#14
Multimodal
40.0#3
40.8#2
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

47 reported for Claude Sonnet 5.5 · 30 for Kimi K3.1 Pro

10 shared

Claude Sonnet 5.5 outperforms in 6 benchmarks (AA-Briefcase v1.1, BenchCAD, BenchCAD (with Python tool), BioMysteryBench, Terminal-Bench 4.0, Terminal-Bench-Science 0.1), while Kimi K3.1 Pro is better at 3 benchmarks (GDPval-AA 2.1, Humanity's Last Exam (with tools), OfficeQA Pro).

Claude Sonnet 5.5 has a slight edge in benchmark performance.

Thu Oct 29 2026 • llm-stats.com

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

For input processing, Claude Sonnet 5.5 ($2.00/1M tokens) costs the same as Kimi K3.1 Pro ($2.00/1M tokens).

For output processing, Claude Sonnet 5.5 ($10.00/1M tokens) costs the same as Kimi K3.1 Pro ($10.00/1M tokens).

In conclusion, Claude Sonnet 5.5 and Kimi K3.1 Pro cost the same.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Thu Oct 29 2026 • llm-stats.com
Anthropic
Claude Sonnet 5.5
Input tokens$2.00
Output tokens$10.00
Best providerAnthropic
Moonshot AI
Kimi K3.1 Pro
Input tokens$2.00
Output tokens$10.00
Best providerUnknown Organization
Notice missing or incorrect data?

Context Window

Maximum input and output token capacity

Kimi K3.1 Pro accepts 1,048,576 input tokens compared to Claude Sonnet 5.5's 1,000,000 tokens. Kimi K3.1 Pro can generate longer responses up to 1,048,576 tokens, while Claude Sonnet 5.5 is limited to 128,000 tokens.

Anthropic
Claude Sonnet 5.5
Input1,000,000 tokens
Output128,000 tokens
Moonshot AI
Kimi K3.1 Pro
Input1,048,576 tokens
Output1,048,576 tokens
Thu Oct 29 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both Claude Sonnet 5.5 and Kimi K3.1 Pro support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

Claude Sonnet 5.5

Text
Images
Audio
Video

Kimi K3.1 Pro

Text
Images
Audio
Video

Release Timeline

When each model was launched

Claude Sonnet 5.5 was released on 2026-09-28, while Kimi K3.1 Pro was released on 2026-10-23.

Kimi K3.1 Pro is 1 month newer than Claude Sonnet 5.5.

Claude Sonnet 5.5

Sep 28, 2026

4 weeks ago

Kimi K3.1 Pro

Oct 23, 2026

3 days ago

3w newer

Knowledge Cutoff

When training data ends

Claude Sonnet 5.5 has a documented knowledge cutoff of 2026-06-01, while Kimi K3.1 Pro's cutoff date is not specified.

We can confirm Claude Sonnet 5.5's training data extends to 2026-06-01, but cannot make a direct comparison without Kimi K3.1 Pro's cutoff date.

Claude Sonnet 5.5

Jun 2026

Kimi K3.1 Pro

—

Provider Availability

Claude Sonnet 5.5 is available from Anthropic. Kimi K3.1 Pro is available from Moonshot AI.

Claude Sonnet 5.5

anthropic logo
Anthropic
Input Price:Input: $2.00/1MOutput Price:Output: $10.00/1M

Kimi K3.1 Pro

moonshot logo
Unknown Organization
Input Price:Input: $2.00/1MOutput Price:Output: $10.00/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?

Judge for yourself.

Run your own prompts against Claude Sonnet 5.5 and Kimi K3.1 Pro side-by-side, then vote on the output you prefer.

Claude Sonnet 5.5
✓ Preferred
Kimi K3.1 Pro
Open in Playground

FAQ

Common questions about Claude Sonnet 5.5 vs Kimi K3.1 Pro.

Which is better, Claude Sonnet 5.5 or Kimi K3.1 Pro?

Claude Sonnet 5.5 and Kimi K3.1 Pro are closely matched on the LLM Stats Score at 57.9 and 55.5. Claude Sonnet 5.5 is made by Anthropic and Kimi K3.1 Pro is made by Moonshot AI. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Claude Sonnet 5.5 compare to Kimi K3.1 Pro in benchmarks?

Claude Sonnet 5.5 scores BenchCAD (with Python tool): 96.3%, ArXivMath (with tools): 95.2%, Global-MMLU: 92.1%, MILU: 91.6%, SWE-bench Multilingual: 90.3%. Kimi K3.1 Pro scores BabyVision: 95.4%, GPQA: 94.2%, BenchCAD (with Python tool): 92.7%, BrowseComp: 92.1%, Chartography: 90.2%.

Is Claude Sonnet 5.5 cheaper than Kimi K3.1 Pro?

Both models cost $2.00 per million input tokens.

What are the context window sizes for Claude Sonnet 5.5 and Kimi K3.1 Pro?

Claude Sonnet 5.5 supports 1.0M tokens and Kimi K3.1 Pro supports 1.0M tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Claude Sonnet 5.5 and Kimi K3.1 Pro?

Key differences include LLM Stats Score (57.9 vs 55.5), context window (1.0M vs 1.0M), licensing (Proprietary vs Unknown). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Sonnet 5.5 and Kimi K3.1 Pro?

Claude Sonnet 5.5 is developed by Anthropic and Kimi K3.1 Pro is developed by Moonshot AI.

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