Comprehensive side-by-side LLM comparison
Grok 4.1 Fast supports multimodal inputs. Both models have their strengths depending on your specific coding needs.
xAI
Grok 4.1 Fast, released by xAI in November 2025, is a fast-response variant from the Grok 4 family featuring a 2M token context window designed for high-throughput applications. It omits thinking tokens for immediate responses, reducing latency while maintaining strong output quality. Grok 4.1 Fast targets production APIs, real-time assistants, and cost-sensitive applications requiring long-context understanding at high volume.
StepFun
Step-3.5-Flash, released by StepFun on February 2, 2026, is a Mixture-of-Experts large language model with 197 billion total parameters and approximately 11 billion active parameters per inference. It features a 256K token context window using a 3:1 sliding-window-to-full-attention ratio, processing 100–350 tokens per second. Step-3.5-Flash targets agentic tasks, coding workflows, and open-source deployments requiring frontier reasoning capabilities with efficient inference, under an Apache 2.0 license.
2 months newer

Grok 4.1 Fast
xAI
2025-11-17
Step-3.5-Flash
StepFun
2026-02-02
Context window and performance specifications
Available providers and their performance metrics
Grok 4.1 Fast
xAI
Step-3.5-Flash
Grok 4.1 Fast
Step-3.5-Flash
Grok 4.1 Fast
Step-3.5-Flash