Model Comparison
Kimi K2 Thinking
vs. Step 3.5 Flash 2603
Comparing 2 AI models · 10 benchmarks · MoonshotAI, StepFun
Recommended Pick
Mo Kimi K2 Thinking 9 metric wins Strongest on: TTFT, Reasoning, Intelligence
Best Value
Step 3.5 Flash 2603
100.0 value score
47.9 reasoning / $0.15/1M
Lowest Price
Step 3.5 Flash 2603
$0.10/1M input price
Best Reasoning
Kimi K2 Thinking
67.3 reasoning score
Blends available reasoning benchmarks
Best for Coding
Kimi K2 Thinking
34.8 coding index
Composite Indices
Higher is better; speed and price are normalized
Standard Benchmarks
Only benchmarks with data are shown
Differences That Matter
Best value
Step 3.5 Flash 2603 has the strongest quality-to-price mix at 100.0 out of 100 value points.
Price gap
Step 3.5 Flash 2603 is 6.0x cheaper on input tokens than Kimi K2 Thinking.
Speed gap
Step 3.5 Flash 2603 generates about 1.6x as many tokens per second as Kimi K2 Thinking.
Reasoning gap
Kimi K2 Thinking leads Step 3.5 Flash 2603 by 19.4 points on reasoning.
Coding gap
Kimi K2 Thinking leads Step 3.5 Flash 2603 by 0.2 points on coding.
Response Face-Off
Run one prompt through the selected models and compare response quality with live speed and cost context.
Kimi K2 Thinking
MoonshotAI
TTFT
—
Time
—
tok/s
—
Tokens
—
Cost
—
Step 3.5 Flash 2603
StepFun
TTFT
—
Time
—
tok/s
—
Tokens
—
Cost
—
Which answer was more useful?
Full Comparison
| Metric | Top Pick Mo Kimi K2 Thinking | St Step 3.5 Flash 2603 |
|---|---|---|
| Pricing per 1M tokens | ||
| Input Cost | $0.60/1M | $0.10/1M |
| Output Cost | $2.50/1M | $0.30/1M |
| Blended (3:1) | $1.07/1M | $0.15/1M |
| Specifications | ||
| Organization | MoonshotAI | StepFun |
| Release Date | Nov 6, 2025 | Apr 2, 2026 |
| Performance & Speed | ||
| Throughput | 128.9 tok/s | 206.6 tok/s |
| TTFT | 962ms | 1021ms |
| Latency | 16475ms | 10700ms |
| Composite Indices | ||
| Value Score | 19.6 | 100.0 |
| Reasoning Score | 67.3 | 47.9 |
| Intelligence | 40.9 | 38.5 |
| Coding | 34.8 | 34.6 |
| Math | 94.7 | — |
| Standard Benchmarks | ||
| GPQA | 83.8% | 82.6% |
| MMLU Pro | 84.8% | — |
| HLE | 22.3% | 22.6% |
| LiveCodeBench | 85.3% | — |
| AIME 2025 | 94.7% | — |
| SciCode | 42.4% | 38.5% |
| LCR | 66.3% | 54.3% |
| IFBench | 68.1% | 66.5% |
| TAU-bench v2 | 93.0% | 87.4% |
| TerminalBench Hard | 31.1% | 32.6% |
Key Takeaways
Step 3.5 Flash 2603 offers the best value at $0.10/1M, making it ideal for high-volume applications and cost-conscious projects.
Kimi K2 Thinking has the strongest reasoning profile with a 67.3 reasoning score, combining the available reasoning-heavy benchmarks.
Kimi K2 Thinking reaches a 34.8 coding index, making it the top choice for software development and code generation tasks.
All models support context windows of ∞+ tokens, suitable for processing lengthy documents and maintaining extended conversations.
When to Choose Each Model
Kimi K2 Thinking
- Complex reasoning tasks
- Research & analysis
- Code generation
- Software development
Step 3.5 Flash 2603
- Cost-sensitive applications
- High-volume processing
