xAI has introduced Grok Voice Think Fast 2.0, its next-generation speech-to-speech model, with gains in intelligence, transcription accuracy, conversational behavior, and tool use. The model is aimed at developers building voice agents and costs $0.08 per minute of audio. xAI expects it to raise performance across almost all use cases without changes to existing prompts.
On Artificial Analysis’ speech-to-speech benchmark, Think Fast 2.0 scored 82.9% overall, up from 75.7% for version 1.0 and ahead of GPT-Realtime-2.1 at 79.1% and Gemini 3.1 Flash at 69.5%. Its agentic score reached 56.5%, compared with 52.1% for its predecessor, 45.7% for GPT-Realtime-2.1, and 37.7% for Gemini 3.1 Flash. Time to first audio fell from 1.25 seconds to 0.70 seconds. The model’s 95.1% conversational benchmark score was just below GPT-Realtime-2.1 at 95.7%.
Transcription is another major focus. In xAI’s evaluation of thousands of short phrases across 24 languages, the company reported accuracy improvements of 1.5 to 2.0 times versus Deepgram Nova 3 and ElevenLabs Scribe v2, and 1.4 times versus Think Fast 1.0. xAI says the gap is roughly 10× under substantial background noise and telephony compression. The comparison uses the word error rate, with lower scores preferred.
Think Fast 2.0 reasons in parallel with speech, a design intended to preserve latency while handling more complex queries. Median relative reasoning-token use fell to 0.4 times, using the predecessor’s 1.0 times as a baseline. xAI says this lets production tool calls usually execute before the agent finishes its first sentence. Reinforcement learning also pushed the model toward shorter sentences, one question at a time, and less fluff while guiding users through complex workflows.
For SpaceXAI, this release is a push to make Grok Voice more dependable in real customer workflows. An A/B test on Starlink’s phone service produced higher sales conversion and support containment rates, according to the company. On August 5, 2026, the grok-voice-latest alias will automatically move from grok-voice-think-fast-1.0 to grok-voice-think-fast-2.0. Developers who want the prior model must pin the 1.0 identifier before the switch; everyone else needs to take no action.