x-AI/Grok-4-Fast

Grok 4 Fast is presented as a speed- and efficiency-oriented variant of Grok 4, with one third-party description claiming similar performance while using 40% fewer resources. The supplied evidence does not provide an architecture, parameter count, training scale, or benchmark results, so the model should be evaluated through its documented interface rather than those unsupported dimensions.

The strongest practical fit is applications that need long-running analysis, image- and file-based input, and configurable generation controls. A third-party OpenRouter guide lists reasoning, tools, temperature, structured-output, response-format, and sampling parameters, making the model suitable for assisted reasoning and tool-oriented workflows. Since the evidence is third-party and does not establish an official xAI specification, users should validate behavior and availability in their own workloads.