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Claude Sonnet 5.5 vs Kimi K2.5

Claude Sonnet 5.5 leads the LLM Stats Score 58.1 to 38.7. Kimi K2.5 is 3.3x cheaper per token.

Anthropic · Moonshot AI · Updated for 2026

Which is better?

Claude Sonnet 5.5 leads the overall LLM Stats Score 58.1 to 38.7, ranking #3 overall.

In the 2 individual benchmarks reported for both models, Claude Sonnet 5.5 wins 2; this is a narrower head-to-head signal than the composite indexes.

On price, Kimi K2.5 is roughly 3.3x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Claude Sonnet 5.5 also accepts a larger context window (1,000,000 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

  • overall performance matters — it scores 58.1 and ranks #3 on LLM Stats
  • your work emphasizes reasoning and coding — it leads those capability indexes
  • you value its reported benchmark strengths — it wins 2 of 2 exact shared results
  • you process long inputs — it offers a 1,000,000 token context window
  • you want the most recent training data — it shipped Sep 2026

Choose Kimi K2.5

  • cost matters — it's about 3.3x cheaper per token
  • you need open weights you can self-host or fine-tune

At a glance

The differences that matter most.

Claude Sonnet 5.5
Anthropic
Kimi K2.5
Moonshot AI
Core performance indexes
LLM Stats Score
58.1
#3
38.7
#68
Reasoning
56.6
#3
38.6
#66
Coding
48.9
#2
24.9
#77
Agents
42.3
#3
18.0
#76
Cost, coverage & limits
Benchmark wins
2 of 2
0 of 2
Input price
$2.00 / M
$0.60 / M
Output price
$10.00 / M
$3.00 / M
Context window
1,000,000
262,100

Capability indexes

Additional strengths measured across groups of related public benchmarks

3 shared
Index
Claude Sonnet 5.5
Kimi K2.5
Math
36.9#34
36.6#37
Vision
40.1#3
27.4#39
Multimodal
40.2#2
29.4#31
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

47 reported for Claude Sonnet 5.5 · 40 for Kimi K2.5

2 shared

Claude Sonnet 5.5 outperforms in 2 benchmarks (SWE-bench Multilingual, SWE-Bench Pro), while Kimi K2.5 is better at 0 benchmarks.

Claude Sonnet 5.5 significantly outperforms across most benchmarks.

Tue Sep 29 2026 • llm-stats.com

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

Kimi K2.5 costs less

For input processing, Claude Sonnet 5.5 ($2.00/1M tokens) is 3.3x more expensive than Kimi K2.5 ($0.60/1M tokens).

For output processing, Claude Sonnet 5.5 ($10.00/1M tokens) is 3.3x more expensive than Kimi K2.5 ($3.00/1M tokens).

In conclusion, Claude Sonnet 5.5 is more expensive than Kimi K2.5.*

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

Lowest available price from all providers
Tue Sep 29 2026 • llm-stats.com
Anthropic
Claude Sonnet 5.5
Input tokens$2.00
Output tokens$10.00
Best providerAnthropic
Moonshot AI
Kimi K2.5
Input tokens$0.60
Output tokens$3.00
Best providerFireworks
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Claude Sonnet 5.5 accepts 1,000,000 input tokens compared to Kimi K2.5's 262,100 tokens. Kimi K2.5 can generate longer responses up to 262,100 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 K2.5
Input262,100 tokens
Output262,100 tokens
Tue Sep 29 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both Claude Sonnet 5.5 and Kimi K2.5 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 K2.5

Text
Images
Audio
Video

License

Usage and distribution terms

Claude Sonnet 5.5 is licensed under a proprietary license, while Kimi K2.5 uses MIT.

License differences may affect how you can use these models in commercial or open-source projects.

Claude Sonnet 5.5

Proprietary

Closed source

Kimi K2.5

MIT

Open weights

Release Timeline

When each model was launched

Claude Sonnet 5.5 was released on 2026-09-28, while Kimi K2.5 was released on 2026-01-27.

Claude Sonnet 5.5 is 8 months newer than Kimi K2.5.

Claude Sonnet 5.5

Sep 28, 2026

1 days ago

8mo newer
Kimi K2.5

Jan 27, 2026

8 months ago

Knowledge Cutoff

When training data ends

Claude Sonnet 5.5 has a documented knowledge cutoff of 2026-06-01, while Kimi K2.5'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 K2.5's cutoff date.

Claude Sonnet 5.5

Jun 2026

Kimi K2.5

—

Provider Availability

Claude Sonnet 5.5 is available from Anthropic. Kimi K2.5 is available from Fireworks, Moonshot AI.

Claude Sonnet 5.5

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

Kimi K2.5

fireworks logo
Fireworks
Input Price:Input: $0.60/1MOutput Price:Output: $3.00/1M
moonshot logo
Unknown Organization
Input Price:Input: $0.60/1MOutput Price:Output: $3.00/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against Claude Sonnet 5.5 and Kimi K2.5 side-by-side, then vote on the output you prefer.

Claude Sonnet 5.5
✓ Preferred
Kimi K2.5
Open in Playground

FAQ

Common questions about Claude Sonnet 5.5 vs Kimi K2.5.

Which is better, Claude Sonnet 5.5 or Kimi K2.5?

Claude Sonnet 5.5 leads the LLM Stats Score 58.1 to 38.7. Claude Sonnet 5.5 is made by Anthropic and Kimi K2.5 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 K2.5 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 K2.5 scores AIME 2025: 96.1%, HMMT 2025: 95.4%, InfoVQAtest: 92.6%, OCRBench: 92.3%, MathVista-Mini: 90.1%.

Is Claude Sonnet 5.5 cheaper than Kimi K2.5?

Kimi K2.5 is 3.3x cheaper for input tokens. Claude Sonnet 5.5 costs $2.00/M input and $10.00/M output via anthropic. Kimi K2.5 costs $0.60/M input and $3.00/M output via fireworks.

What are the context window sizes for Claude Sonnet 5.5 and Kimi K2.5?

Claude Sonnet 5.5 supports 1.0M tokens and Kimi K2.5 supports 262K 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 K2.5?

Key differences include LLM Stats Score (58.1 vs 38.7), context window (1.0M vs 262K), input pricing ($2.00 vs $0.60/M), licensing (Proprietary vs MIT). See the full comparison above for benchmark-by-benchmark results.

Who makes Claude Sonnet 5.5 and Kimi K2.5?

Claude Sonnet 5.5 is developed by Anthropic and Kimi K2.5 is developed by Moonshot AI.

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