x-ai/grok-4.1-fastGrok 4.1 Fast is xAI's best agentic tool calling model for customer support, deep research, and similar workloads. Released November 19, 2025. 2M context window, up to 30K tokens output. Pricing: $0.20/M input, $0.50/M output, $0.05/M cache read. Reasoning can be toggled via the reasoning-enabled API parameter. OpenRouter routes to xAI and compatible providers with fallbacks.