Step 3.5 Flash
ModelOpen sourceActiveby StepFun · family “step-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.... (description from the OpenRouter listing)
in: textout: textReasoningTool use
Epoch Capabilities Index
Not scored by Epoch AI
Released
29 Jan 2026
Context window
262K tokens
Max output
66K tokens
Input $ / 1M tokens
$0.10
Output $ / 1M tokens
$0.30
Cached input $ / 1M
Unknown
Each benchmark shown separately with its own source
Benchmark results (0)
No benchmark results recorded for this model.
Source: Epoch AI Benchmarking Hub (CC BY 4.0). “External” rows are leaderboard results Epoch collects from third parties. Best reported setting per benchmark is shown.
API list price over time
Price history
$ per 1M tokens
8 observations (OpenRouter listing + Internet Archive snapshots). History accumulates with every ingest run; a single point means no change has been observed yet.
Events
- Open release8mo agoStepFun releases Step 3.5 FlashOpenRouter models API