Step 3.5 Flash 2603

Name: Step 3.5 Flash 2603
Author: StepFun

StepFun

Step 3.5 Flash 2603 is a 2026 efficiency update to StepFun's Step 3.5 Flash reasoning model. It introduces a configurable token-budget system with a low mode that uses significantly fewer tokens for straightforward requests and a high mode that preserves full reasoning depth, making it better suited for agentic workflows that issue many sequential tool calls.

Benchmark scores

Benchmark	Score
AA-LCR	54.3
AA-LCR v1.1	63.0
AA-Omniscience Index	-44.2
Artificial Analysis Omniscience Accuracy	24.6
Artificial Analysis Omniscience Hallucination Rate	91.3
Artificial Analysis Progress Index v1	260
Capability	147.2
CritPt (avg@5)	2.3
GPQA Diamond (Artificial Analysis avg@5)	82.6
Humanity's Last Exam (Text-Only)	24.5
IFBench (Artificial Analysis avg@5)	66.5
SciCode (Artificial Analysis avg@3)	38.5
Terminal-Bench Hard	32.6
τ²-bench (Telecom)	87.4