GPT 5.1 Codex Mini is the lightweight, fast variant in the GPT-5.1 codex family, optimized for routine coding tasks like bug fixes, feature scaffolding, and test generation at a cost that scales to high-frequency CI and development workflows.
import { streamText } from 'ai'
const result = streamText({ model: 'openai/gpt-5.1-codex-mini', prompt: 'Why is the sky blue?'})GPT 5.1 Codex Mini was released on November 12, 2025 as the affordable, fast option in the GPT-5.1 codex family on AI Gateway. It targets the high-volume, routine coding tasks that make up the bulk of development work: fixing bugs, implementing straightforward features, generating tests, and providing code review feedback.
As the mini variant, it prioritizes speed and cost over maximum reasoning depth. This makes it practical to deploy as always-on automation that runs on every code change rather than being reserved for complex tasks. The model still benefits from the GPT-5.1 generation's improvements over earlier models.
It operates in the same sandboxed agentic environment as other codex variants, with the ability to read repositories, write code, execute tests, and iterate. The context window of 400K tokens gives it enough room to understand the relevant portions of a codebase for most routine tasks.