Step 3.5 Flash 2603

Step 3.5 Flash 2603 is a flash model from StepFun for efficient multimodal reasoning, coding, and tool use, according to the maker. It is the latest release in the step line, dated 2026-04-02, succeeding Step 3.5 Flash from 2026-01-29. It has a context window of 256,000 tokens and a maximum output of 256,000 tokens. The weights are open. It supports reasoning mode and tool calling. It accepts text and returns text. The knowledge cutoff is 2025-01. It is served by 5 hosts. Pricing starts at $0.10 per million input tokens and $0.30 per million output tokens, with cached input at $0.02 per million tokens.

Against Step 3.5 Flash: input $0.09 to $0.10.

• ·256k context and output window
• ·Open weights for self-hosting
• ·Reasoning mode and tool calling
• ·Input from $0.10 per million tokens
• ·Cached input from $0.02 per million tokens

• Reach for it for coding and tool use
• Reach for it for long-context text reasoning
• Reach for it for self-hosted deployment with open weights
• Reach for it for text generation with large output windows

5 hosts serve this model at the price above · the maker's documentation

The registry keeps the six most recent versions of a line. Older ones stay in the file and can be surfaced without a rebuild.

What is the context window and output limit?

Both the context window and the maximum output are 256,000 tokens.

Is the model open weights?

Yes, the weights are open.

What are the prices?

Input from $0.10 per million tokens, output $0.30 per million, cached input $0.02 per million.