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GPT 5.1 Codex Mini

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.

View API reference
Input and output price
Input $0.25, Output $2, Per 1M tokens
24h uptime
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import { streamText } from 'ai'
const result = streamText({
model: 'openai/gpt-5.1-codex-mini',
prompt: 'Why is the sky blue?'
})
Read docs

Copy link to headingPlayground

Try out GPT 5.1 Codex Mini by OpenAI. Usage is billed to your team at API rates. Free users (those who haven't made a payment) get $5 of credits every 30 days.

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GPT 5.1 Codex Mini

Copy link to headingProviders

Route requests across multiple providers. Copy a provider slug to set your preference. Visit the docs for more info. Using a provider means you agree to their terms, listed under Legal.

Provider
Context
Max Output
Latency
Throughput
Input
Output
Cache
Web Search
Capabilities
ZDR
No Training
Free Tier
Release Date
400K128K0.6 s37 tps
$0.25/M
$2/M
Read$0.03/M
$14/K
+3
11/12/2025

Copy link to headingUptime

Direct request success rate on AI Gateway and per-provider. Visit the docs for more info.

Copy link to headingThroughput

P50 throughput on live AI Gateway traffic, in tokens per second (TPS). Visit the docs for more info.

Copy link to headingLatency

P50 time to first token (TTFT) on live AI Gateway traffic, in milliseconds. View the docs for more info.

Getting started

Call GPT 5.1 Codex Mini through AI Gateway with the AI SDK generateText and streamText functions, or through the OpenAI Chat Completions, OpenAI Responses, and Anthropic Messages APIs by changing the base URL. AI Gateway authenticates the request and routes it to an available provider.

Install the AI SDK (pnpm add ai dotenv), create an API key from the API Keys page, and set it as AI_GATEWAY_API_KEY in your environment. Full setup is covered in the text generation quickstart.

index.ts
import { generateText } from 'ai';
import 'dotenv/config';
async function main() {
const result = await generateText({
model: 'openai/gpt-5.1-codex-mini',
prompt: 'Why is the sky blue?',
});
console.log(result.text);
}
main().catch(console.error);

Top-level parameters

The same GPT 5.1 Codex Mini request in each API format AI Gateway supports.

top-level-params.ts
import { generateText } from 'ai';
import 'dotenv/config';
async function main() {
const result = await generateText({
model: 'openai/gpt-5.1-codex-mini',
system: 'You are a concise technical assistant.',
prompt: 'Summarize the tradeoffs between static generation and SSR.',
maxOutputTokens: 1024,
});
console.log(result.text);
}
main().catch(console.error);

Standard parameters like prompt, messages, temperature, and tools work as documented in the AI SDK docs. These are the parameters with model-specific behavior.

ParameterTypeRequiredDescription
modelstringYesModel ID in the form creator/model, e.g. openai/gpt-5.1-codex-mini. AI Gateway routes the request to an available provider.
maxOutputTokensnumberNoHard cap on generated tokens. GPT 5.1 Codex Mini supports up to 128,000 output tokens. Reasoning tokens count toward this limit.
reasoning'provider-default' | 'none' | 'minimal' | 'low' | 'medium' | 'high' | 'xhigh'NoProvider-agnostic reasoning effort, available in AI SDK 7 or later. Maps to the provider’s native reasoning configuration; reasoning settings under providerOptions take precedence when both are set. See the Reasoning section below.
providerOptionsRecord<string, JSONValue>NoAI Gateway routing options under gateway, plus any provider-native options under the provider’s own namespace — see the table below.

Input limits

InputFormatsSourcesMax countMax sizeLimits
TextPrompt and response share the 400K-token context window
ImageURL, base64, Uint8ArraySent as image parts in messages; counts as input tokens
PDFURL, base64, Uint8ArraySent as file parts in messages; counts as input tokens

Provider options

Set AI Gateway routing options under providerOptions.gateway. For provider-specific options, pass them under the provider’s namespace as documented by the AI SDK.

Learn more in the AI SDK openai provider docs.

provider-options.ts
import { generateText } from 'ai';
import 'dotenv/config';
async function main() {
const result = await generateText({
model: 'openai/gpt-5.1-codex-mini',
prompt: 'Why is the sky blue?',
providerOptions: {
gateway: {
only: ['azure'],
},
},
});
console.log(result.text);
}
main().catch(console.error);

These AI Gateway routing options apply to every model. Provider-specific options pass through under the provider’s own namespace (for example providerOptions.anthropic) exactly as documented by the AI SDK.

ParameterTypeRequiredDescription
providerOptions.gateway.onlystring[]NoRestrict routing to these provider slugs. Requests fail over only within the listed providers.
providerOptions.gateway.orderstring[]NoPreferred provider order. Listed providers are tried first; unlisted providers remain available as fallbacks.
providerOptions.gateway.sort'cost' | 'ttft' | 'tps'NoRank candidate providers by price, time to first token, or tokens per second instead of the default routing order.
providerOptions.gateway.zeroDataRetentionbooleanNoRoute only to providers with a zero-data-retention policy for this model.

Routing across providers

AI Gateway serves the same model through multiple providers and fails over automatically. order expresses a preference while keeping every provider eligible; only is a hard allowlist — if none of the listed providers are available the request fails instead of falling back.

Options under a provider's own namespace (for example providerOptions.anthropic) are forwarded to that provider with the request. Providers ignore option namespaces that don't apply to them, so it is safe to set provider options alongside gateway routing options.

Reasoning

AI Gateway bridges reasoning across every API format. The AI SDK exposes a provider-agnostic top-level reasoning level (none, minimal, low, medium, high, or xhigh); the Chat Completions and Responses formats take the same effort under reasoning.effort; and the Anthropic Messages format uses a native thinking token budget. Whichever you send, the gateway maps it to the target model’s native configuration, converting between effort levels and token budgets as needed. Reasoning-related settings under providerOptions take full precedence over the top-level reasoning value and are never merged. Reasoning tokens typically count toward your output-token usage, though how they’re reported and billed varies by provider.

Learn more in the AI Gateway reasoning guide.

reasoning.ts
import { generateText } from 'ai';
import 'dotenv/config';
async function main() {
const result = await generateText({
model: 'openai/gpt-5.1-codex-mini',
prompt: 'Explain the Monty Hall problem step by step.',
reasoning: 'high',
});
console.log(result.text);
}
main().catch(console.error);

Image input

Send images alongside text as message parts. Images count as input tokens.

image-input.ts
import { generateText } from 'ai';
import 'dotenv/config';
async function main() {
const result = await generateText({
model: 'openai/gpt-5.1-codex-mini',
messages: [
{
role: 'user',
content: [
{ type: 'text', text: 'Describe this image.' },
{ type: 'image', image: 'https://example.com/photo.jpg' },
],
},
],
});
console.log(result.text);
}
main().catch(console.error);

PDF input

Attach PDFs as file parts. Their contents count as input tokens.

pdf-input.ts
import { generateText } from 'ai';
import 'dotenv/config';
async function main() {
const result = await generateText({
model: 'openai/gpt-5.1-codex-mini',
messages: [
{
role: 'user',
content: [
{ type: 'text', text: 'Summarize this document.' },
{
type: 'file',
mediaType: 'application/pdf',
data: 'https://example.com/document.pdf',
},
],
},
],
});
console.log(result.text);
}
main().catch(console.error);

Tool calling

Expose tools the model can call. Define each tool’s inputs with a Zod schema.

tool-calling.ts
import { generateText, tool } from 'ai';
import { z } from 'zod';
import 'dotenv/config';
async function main() {
const result = await generateText({
model: 'openai/gpt-5.1-codex-mini',
prompt: 'What is the weather in San Francisco?',
tools: {
getWeather: tool({
description: 'Get the current weather for a location',
inputSchema: z.object({ location: z.string() }),
execute: async ({ location }) => ({ location, temperatureC: 18 }),
}),
},
});
console.log(result.text);
}
main().catch(console.error);

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Copy link to headingAbout GPT 5.1 Codex Mini

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.

Copy link to headingWhat To Consider When Choosing a Provider

  • Configuration: GPT 5.1 Codex Mini is priced for high-frequency use. Running it on every pull request, commit, or code change is economically viable, enabling continuous automated coding assistance.
  • Configuration: It handles the majority of everyday coding tasks well. Escalate to standard codex or codex max only when the task's complexity warrants it.
  • Zero Data Retention: Zero Data Retention is available for this model. It is offered on a per-provider and model basis. See the documentation for details.
  • Authentication: AI Gateway authenticates requests using an API key or OIDC token. You do not need to manage provider credentials directly.

Copy link to headingWhen to Use GPT 5.1 Codex Mini

Best for

  • Per-PR code review: Automated suggestions on every pull request at sustainable cost
  • Bug fix automation: Routine bug fixes with clear reproduction steps
  • Feature scaffolding: Generating boilerplate and implementing straightforward features
  • Test generation: Writing unit and integration test cases that cover existing code paths
  • CI integration: Continuous coding assistance embedded in development pipelines

Consider alternatives when

  • Complex refactoring: Standard GPT-5.1 codex for multi-file architectural changes
  • Critical code audits: Codex max for security-sensitive or high-stakes reviews
  • Non-coding tasks: GPT-5.1 instant for general-purpose fast inference
  • Maximum reasoning depth: O3 or o4-mini for problems requiring extended chain-of-thought

GPT 5.1 Codex Mini makes continuous AI-assisted development practical by bringing GPT-5.1 codex capability to a price point that scales with development velocity. For teams that want coding assistance on every PR through AI Gateway, it is the natural choice.

Copy link to headingFrequently Asked Questions

  • How does GPT 5.1 Codex Mini compare to standard GPT-5.1 codex?

    It's faster and cheaper but with less reasoning depth. It handles routine tasks well and is designed for high-frequency use in CI pipelines and development workflows.

  • Is GPT 5.1 Codex Mini good enough for code review?

    Yes, for standard code review. For security audits or architecturally complex changes, escalate to standard codex or codex max.

  • What context window does GPT 5.1 Codex Mini support?

    400K tokens, sufficient for understanding the relevant portions of most codebases.

  • How does AI Gateway handle authentication for GPT 5.1 Codex Mini?

    AI Gateway accepts a single API key or OIDC token for all requests. You don't embed OpenAI credentials in your application; AI Gateway routes and authenticates on your behalf.

  • Can I run GPT 5.1 Codex Mini on every commit?

    Yes. Its pricing is designed to make per-commit and per-PR automation economically viable.

  • What are typical latency characteristics?

    This page shows live throughput and time-to-first-token metrics measured across real AI Gateway traffic.

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