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Kimi K3.1 Pro vs Step-3.5-Flash

Kimi K3.1 Pro leads the LLM Stats Score 55.5 to 36.5. Step-3.5-Flash is 22.9x cheaper per token.

Moonshot AI · StepFun · Updated for 2026

Which is better?

Kimi K3.1 Pro leads the overall LLM Stats Score 55.5 to 36.5, ranking #5 overall.

In the 1 individual benchmarks reported for both models, Kimi K3.1 Pro wins 1; this is a narrower head-to-head signal than the composite indexes.

On price, Step-3.5-Flash is roughly 22.9x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

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 Kimi K3.1 Pro

  • overall performance matters — it scores 55.5 and ranks #5 on LLM Stats
  • your work emphasizes reasoning and coding — it leads those capability indexes
  • you value its reported benchmark strengths — it wins 1 of 1 exact shared results
  • you process long inputs — it offers a 1,048,576 token context window
  • you want the most recent training data — it shipped Oct 2026

Choose Step-3.5-Flash

  • cost matters — it's about 22.9x cheaper per token
  • you need open weights you can self-host or fine-tune

At a glance

The differences that matter most.

Kimi K3.1 Pro
Moonshot AI
Step-3.5-Flash
StepFun
Core performance indexes
LLM Stats Score
55.5
#5
36.5
#94
Reasoning
54.3
#6
36.5
#94
Coding
42.7
#9
20.5
#120
Agents
41.6
#5
15.0
#115
Cost, coverage & limits
Benchmark wins
1 of 1
0 of 1
Input price
$2.00 / M
$0.10 / M
Output price
$10.00 / M
$0.40 / M
Context window
1,048,576
65,536

Capability indexes

Additional strengths measured across groups of related public benchmarks

2 shared
Index
Kimi K3.1 Pro
Step-3.5-Flash
Math
38.6#26
34.0#55
Tool use
30.4#14
13.2#123
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

30 reported for Kimi K3.1 Pro · 7 for Step-3.5-Flash

1 shared

Kimi K3.1 Pro outperforms in 1 benchmarks (BrowseComp), while Step-3.5-Flash is better at 0 benchmarks.

Kimi K3.1 Pro significantly outperforms across most benchmarks.

Fri Oct 30 2026 • llm-stats.com

Human preference

Blind head-to-head votes and playground preference scores

Pricing Analysis

Price comparison per million tokens

Step-3.5-Flash costs less

For input processing, Kimi K3.1 Pro ($2.00/1M tokens) is 20.0x more expensive than Step-3.5-Flash ($0.10/1M tokens).

For output processing, Kimi K3.1 Pro ($10.00/1M tokens) is 25.0x more expensive than Step-3.5-Flash ($0.40/1M tokens).

In conclusion, Kimi K3.1 Pro is more expensive than Step-3.5-Flash.*

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

Lowest available price from all providers
Fri Oct 30 2026 • llm-stats.com
Moonshot AI
Kimi K3.1 Pro
Input tokens$2.00
Output tokens$10.00
Best providerUnknown Organization
StepFun
Step-3.5-Flash
Input tokens$0.10
Output tokens$0.40
Best providerStepFun
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 Step-3.5-Flash's 65,536 tokens. Kimi K3.1 Pro can generate longer responses up to 1,048,576 tokens, while Step-3.5-Flash is limited to 8,192 tokens.

Moonshot AI
Kimi K3.1 Pro
Input1,048,576 tokens
Output1,048,576 tokens
StepFun
Step-3.5-Flash
Input65,536 tokens
Output8,192 tokens
Fri Oct 30 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Kimi K3.1 Pro supports multimodal inputs, whereas Step-3.5-Flash does not.

Kimi K3.1 Pro can handle both text and other forms of data like images, making it suitable for multimodal applications.

Kimi K3.1 Pro

Text
Images
Audio
Video

Step-3.5-Flash

Text
Images
Audio
Video

Release Timeline

When each model was launched

Kimi K3.1 Pro was released on 2026-10-23, while Step-3.5-Flash was released on 2026-02-02.

Kimi K3.1 Pro is 9 months newer than Step-3.5-Flash.

Kimi K3.1 Pro

Oct 23, 2026

2 days ago

8mo newer
Step-3.5-Flash

Feb 2, 2026

8 months ago

Knowledge Cutoff

When training data ends

Neither model specifies a knowledge cutoff date.

Unable to compare the recency of their training data.

No cutoff dates available

Provider Availability

Kimi K3.1 Pro is available from Moonshot AI. Step-3.5-Flash is available from StepFun.

Kimi K3.1 Pro

moonshot logo
Unknown Organization
Input Price:Input: $2.00/1MOutput Price:Output: $10.00/1M

Step-3.5-Flash

stepfun logo
StepFun
Input Price:Input: $0.10/1MOutput Price:Output: $0.40/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?

Judge for yourself.

Run your own prompts against Kimi K3.1 Pro and Step-3.5-Flash side-by-side, then vote on the output you prefer.

Kimi K3.1 Pro
✓ Preferred
Step-3.5-Flash
Open in Playground

FAQ

Common questions about Kimi K3.1 Pro vs Step-3.5-Flash.

Which is better, Kimi K3.1 Pro or Step-3.5-Flash?

Kimi K3.1 Pro leads the LLM Stats Score 55.5 to 36.5. Kimi K3.1 Pro is made by Moonshot AI and Step-3.5-Flash is made by StepFun. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Kimi K3.1 Pro compare to Step-3.5-Flash in benchmarks?

Kimi K3.1 Pro scores BabyVision: 95.4%, GPQA: 94.2%, BenchCAD (with Python tool): 92.7%, BrowseComp: 92.1%, Chartography: 90.2%. Step-3.5-Flash scores AIME 2025: 97.3%, Tau-bench: 88.2%, LiveCodeBench v6: 86.4%, IMO-AnswerBench: 85.4%, SWE-Bench Verified: 74.4%.

Is Kimi K3.1 Pro cheaper than Step-3.5-Flash?

Step-3.5-Flash is 20.0x cheaper for input tokens. Kimi K3.1 Pro costs $2.00/M input and $10.00/M output via moonshot. Step-3.5-Flash costs $0.10/M input and $0.40/M output via stepfun.

What are the context window sizes for Kimi K3.1 Pro and Step-3.5-Flash?

Kimi K3.1 Pro supports 1.0M tokens and Step-3.5-Flash supports 66K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Kimi K3.1 Pro and Step-3.5-Flash?

Key differences include LLM Stats Score (55.5 vs 36.5), context window (1.0M vs 66K), input pricing ($2.00 vs $0.10/M), multimodal support (yes vs no), licensing (Unknown vs Apache 2.0). See the full comparison above for benchmark-by-benchmark results.

Who makes Kimi K3.1 Pro and Step-3.5-Flash?

Kimi K3.1 Pro is developed by Moonshot AI and Step-3.5-Flash is developed by StepFun.

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