Step 3.5 Flash
Newer version available: Step 3.7 Flash
Released
2026-01-29
Last refreshed
2026-10-17
Status
Researched today
ProprietaryCommercial use: restrictedCodingAgentsLong context
StepFun releases · 6 in the last 12 months · this family litChangelog →
Specifications
- Family
- Step
- Released
- 2026-01-29
- Context
- 256K
- Parameters
- 196B (11B active)
- Architecture
- Mixture of Experts
- Specialization
- general
- Openness
- Proprietary
- License
- ProprietaryRestricted
- Weights
- Not released
- Code
- Unknown
- Training
- Pretrained
Pricing
Output / 1M
$0.300
Input / 1M
$0.100
Cheapest of 1 route · OpenRouter
About
Step 3.5 Flash is StepFun's most capable open-source foundation model. Its sparse Mixture of Experts architecture activates only 11B of 196B total parameters per token, making it highly efficient at long contexts. Achieves 60.47% on SWE-Bench Verified and 56.2% on SWE-Pro, competing with frontier closed models on agentic coding benchmarks. Supports 256K token context.
Top use-case fit: coding, agents, and build tasks
Coding
Q/$ BAgents
Q/$ AProviders(1)
Compare API pricing across 1 tracked provider route for input and output tokens, batch, and cached reads when available.
| Provider | Input / 1M | Output / 1M | Route |
|---|---|---|---|
| OpenRouter | $0.100 | $0.300 | Serverless |
Capabilities
Reasoning
Benchmark peer barsfor Coding
SWE-bench VerifiedRank 47 of 100
LiveCodeBenchRank 19 of 73
Benchmark scores(3)
Scores are benchmark-specific and are direction-aware: the same numeric gap can mean very different outcomes across suites. Use the leaderboard context and this model's provider route to decide whether the winning margin is meaningful for your workload.
| Benchmark | Score | Version | Evaluation | Source |
|---|---|---|---|---|
| 97.3 | From official StepFun blog post (accuracy%)Observed 2026-06-07 | — | ||
| 86.4 | LiveCodeBench-V6 (accuracy%)Observed 2026-06-07 | — | ||
| 74.4 | From official StepFun blog post (resolved%)Observed 2026-06-07 | — |
Migration checks
No linked migration route is available for this model yet.
Rankings & picks(1)
Compare Step 3.5 Flash with other models
Comparison and alternatives
Browse all comparisons →Step 3.5 Flash vs Step 3.7 FlashStep 3.5 Flash vs Claude Opus 4.7Step 3.5 Flash vs Claude Sonnet 4.6Step 3.5 Flash vs Claude Sonnet 4.5Step 3.5 Flash vs Grok 4Step 3.5 Flash vs Claude Opus 4.6Step 3.5 Flash vs GPT-5.3-Codex-SparkStep 3.5 Flash vs Kimi K2.5Step 3.5 Flash vs DeepSeek V3.1Step 3.5 Flash vs Claude Opus 4.5Step 3.5 Flash vs DeepSeek V3Step 3.5 Flash vs GPT-5.4Step 3.5 Flash vs Claude Haiku 4.5Step 3.5 Flash vs o3Step 3.5 Flash vs DeepSeek R1Step 3.5 Flash vs GPT-5.4 Pro
Show all 2 popular comparisonssorted by 7-day search impressions
Pricing
Output / 1M
$0.300
Input / 1M
$0.100
Cheapest of 1 route · OpenRouter