# Step 3.5 Flash 2603

> Step 3.5 Flash 2603 is an open-weight language model from StepFun, released on 2 Apr 2026. It accepts text and generates text, with a 256K-token context window and up to 131K output tokens per response.

Source page: https://www.aimodel.directory/models/step-3-5-flash-2603
Last verified: 4 Oct 2026

## Specifications

- **Developer:** StepFun
- **Release date:** 2 Apr 2026 (source: models.dev, https://github.com/sst/models.dev/blob/dev/providers/empiriolabs/models/step-3-5-flash-2603.toml)
- **Status:** Generally available (source: models.dev, https://github.com/sst/models.dev/blob/dev/providers/empiriolabs/models/step-3-5-flash-2603.toml)
- **Weights:** Open weights (source: models.dev, https://github.com/sst/models.dev/blob/dev/providers/empiriolabs/models/step-3-5-flash-2603.toml)
- **Context window:** 256K (256,000 tokens) (source: models.dev, https://github.com/sst/models.dev/blob/dev/providers/empiriolabs/models/step-3-5-flash-2603.toml)
- **Max output:** 131K tokens (source: models.dev, https://github.com/sst/models.dev/blob/dev/providers/empiriolabs/models/step-3-5-flash-2603.toml)
- **Knowledge cutoff:** Jan 2025 (source: models.dev, https://github.com/sst/models.dev/blob/dev/providers/empiriolabs/models/step-3-5-flash-2603.toml)
- **Input:** Text (source: models.dev, https://github.com/sst/models.dev/blob/dev/providers/empiriolabs/models/step-3-5-flash-2603.toml)
- **Output:** Text (source: models.dev, https://github.com/sst/models.dev/blob/dev/providers/empiriolabs/models/step-3-5-flash-2603.toml)
- **Reasoning mode:** Yes (source: models.dev, https://github.com/sst/models.dev/blob/dev/providers/empiriolabs/models/step-3-5-flash-2603.toml)
- **Tool calling:** Yes (source: models.dev, https://github.com/sst/models.dev/blob/dev/providers/empiriolabs/models/step-3-5-flash-2603.toml)
- **Structured output:** Yes (source: models.dev, https://github.com/sst/models.dev/blob/dev/providers/empiriolabs/models/step-3-5-flash-2603.toml)

## API pricing (USD per 1M tokens)

| Provider | Input | Output | Cached input | Context |
|---|---|---|---|---|

## FAQ

### What is the context window of Step 3.5 Flash 2603?

Step 3.5 Flash 2603 has a context window of 256,000 tokens (256K) and can generate up to 131,072 tokens in a single response, according to models.dev.

### Is Step 3.5 Flash 2603 open source?

Step 3.5 Flash 2603 is an open-weight model. Check the license terms before commercial use.

### When was Step 3.5 Flash 2603 released?

StepFun released Step 3.5 Flash 2603 on 2 Apr 2026, according to models.dev.

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Data licensed CC BY 4.0. Cite as: AI Model Directory, "Step 3.5 Flash 2603", https://www.aimodel.directory/models/step-3-5-flash-2603