Model Comparison
Step 3.5 Flash
vs. GPT-5.5 (xhigh)
Comparing 2 AI models · 7 benchmarks · StepFun, OpenAI
Recommended Pick
Op GPT-5.5 (xhigh) 9 metric wins Strongest on: Reasoning, Intelligence, Coding
Best Value
Step 3.5 Flash
100.0 value score
46.7 reasoning / $0.15/1M
Lowest Price
Step 3.5 Flash
$0.10/1M input price
Best Reasoning
GPT-5.5 (xhigh)
66.0 reasoning score
Blends available reasoning benchmarks
Best for Coding
GPT-5.5 (xhigh)
59.1 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 has the strongest quality-to-price mix at 100.0 out of 100 value points.
Price gap
Step 3.5 Flash is 50x cheaper on input tokens than GPT-5.5 (xhigh).
Speed gap
Step 3.5 Flash generates about 3.1x as many tokens per second as GPT-5.5 (xhigh).
Reasoning gap
GPT-5.5 (xhigh) leads Step 3.5 Flash by 19.3 points on reasoning.
Coding gap
GPT-5.5 (xhigh) leads Step 3.5 Flash by 27.5 points on coding.
Response Face-Off
Run one prompt through the selected models and compare response quality with live speed and cost context.
Step 3.5 Flash
StepFun
TTFT
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Time
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tok/s
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Tokens
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Cost
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GPT-5.5 (xhigh)
OpenAI
TTFT
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Time
—
tok/s
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Tokens
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Cost
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Which answer was more useful?
Full Comparison
| Metric | St Step 3.5 Flash | Top Pick Op GPT-5.5 (xhigh) |
|---|---|---|
| Pricing per 1M tokens | ||
| Input Cost | $0.10/1M | $5.00/1M |
| Output Cost | $0.30/1M | $30.00/1M |
| Blended (3:1) | $0.15/1M | $11.25/1M |
| Specifications | ||
| Organization | StepFun | OpenAI |
| Release Date | Feb 2, 2026 | Apr 23, 2026 |
| Performance & Speed | ||
| Throughput | 219.8 tok/s | 70.7 tok/s |
| TTFT | 850ms | 43813ms |
| Latency | 9950ms | 43813ms |
| Composite Indices | ||
| Value Score | 100.0 | 1.9 |
| Reasoning Score | 46.7 | 66.0 |
| Intelligence | 37.8 | 60.2 |
| Coding | 31.6 | 59.1 |
| Standard Benchmarks | ||
| GPQA | 83.1% | 93.5% |
| HLE | 19.1% | 44.3% |
| SciCode | 40.4% | 56.1% |
| LCR | 43.0% | 74.3% |
| IFBench | 64.6% | 75.9% |
| TAU-bench v2 | 94.4% | 93.9% |
| TerminalBench Hard | 27.3% | 60.6% |
Key Takeaways
Step 3.5 Flash offers the best value at $0.10/1M, making it ideal for high-volume applications and cost-conscious projects.
GPT-5.5 (xhigh) has the strongest reasoning profile with a 66.0 reasoning score, combining the available reasoning-heavy benchmarks.
GPT-5.5 (xhigh) reaches a 59.1 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
Step 3.5 Flash
- Cost-sensitive applications
- High-volume processing
GPT-5.5 (xhigh)
- Complex reasoning tasks
- Research & analysis
- Code generation
- Software development
