xAI releases Grok 4.3 reasoning model with 1M token context at $1.25/M input tokens

xAI has released Grok 4.3, a multimodal reasoning model with a 1 million token context window and no output token limit. Released on April 30, 2026, the model is now available through OpenRouter.

Specifications and pricing

Grok 4.3 processes text and image inputs with text output. Input tokens are priced at $1.25 per million tokens, while output tokens cost $2.50 per million tokens. According to xAI, requests exceeding 200,000 total tokens are billed at a higher rate, though the elevated pricing tier has not been disclosed.

The model features always-on reasoning that cannot be disabled or configured by effort level. This distinguishes it from other reasoning models that allow users to adjust computational intensity.

Technical capabilities

xAI positions Grok 4.3 for agentic workflows, instruction-following tasks, and applications requiring high factual accuracy. The absence of an output token limit, combined with the 1 million token context window, enables the model to handle long-document analysis and multi-step agentic tasks without truncation.

The model supports multimodal input, accepting both text and images, but outputs text only.

API access

Grok 4.3 is accessible through OpenRouter's API, which normalizes requests and responses across providers. The platform routes requests to available providers and includes fallback mechanisms for uptime.

OpenRouter's API supports accessing the model's reasoning process through a reasoning_details array in responses. The platform requires preserving complete reasoning details when passing messages back to the model for continued conversations.

What this means

Grok 4.3 enters a competitive reasoning model market where always-on reasoning represents a trade-off: consistent step-by-step thinking for all queries, but no ability to reduce computational cost for simpler tasks. The 1M token context window and unlimited output position it for enterprise document analysis and complex multi-turn interactions. The tiered pricing structure for requests over 200K tokens suggests xAI expects the model to be used for extended contexts, though the lack of disclosed upper-tier pricing creates uncertainty for budget planning at scale.