gpt-oss-20b vs Step 3.5 Flash
How do these models stack up? Below is an expert side-by-side comparison of specifications, context window capacity, live pricing per million tokens, and standardized benchmark scores for gpt-oss-20b and Step 3.5 Flash.
gpt-oss-20b
gpt-oss-20b is an open-weight 21B parameter model released by OpenAI under the Apache 2.0 license. It uses a Mixture-of-Experts (MoE) architecture with 3.6B active parameters per forward pass, optimized for...
Step 3.5 Flash
Step 3.5 Flash is StepFun's most capable open-source foundation model. Built on a sparse Mixture of Experts (MoE) architecture, it selectively activates only 11B of its 196B parameters per token....
Technical Specifications
| Specification | gpt-oss-20b | Step 3.5 Flash |
|---|---|---|
| Provider | OpenAI | StepFun |
| Context Window | 131,072 tokens | 262,144 tokens |
| Agent Suitability | N/A | N/A |
| Time to First Token (TTFT) | N/A | N/A |
| Deployment Model | managed api | managed api |
| Production Stability | stable | stable |
| API Available | Yes | Yes |
| Released Date | 2025-08-05 | 2026-01-29 |
API Pricing Comparison
Input Price per Million Tokens
gpt-oss-20b
$0.03
Step 3.5 Flash
$0.10
Output Price per Million Tokens
gpt-oss-20b
$0.14
Step 3.5 Flash
$0.30
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Benchmark Performance Metrics
Scores show the raw performance percentages verified across key evaluation suites. Higher bars indicate superior accuracy and capability in that domain.
gpt-oss-20b Quirks & Gotchas
No developer gotchas reported.
Step 3.5 Flash Quirks & Gotchas
No developer gotchas reported.