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%.
Announcing Grok Voice Think Fast 2.0, our next-generation voice model with improved intelligence, transcription accuracy, and conversational capabilities.https://t.co/XUiX1CouKz pic.twitter.com/Nel3zwzkwY
— SpaceXAI (@SpaceXAI) July 29, 2026
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.
