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GPT-5.1 Codex

GPT-5.1 Codex specializes GPT-5.1 for software engineering, from interactive development to extended independent assignments. It can create projects, add features, debug, refactor large repositories, and review code while following developer instructions closely. Adjustable reasoning effort supports both small changes and sustained work. Image inputs help with interface development, and tools support search, dependency installation, environment setup, and checking behavior against tests.

textreasoningfunction tools
gpt-5.1-codex
Version date 2025-11-13

Our price

$1.01 / $8.07

input / output per 1M

Official

$1.25 / $10.00
−19% vs official

USD · Published rate · Updated 2026-10-06

First request

Available
curl https://api.tokely.me/v1/responses \
  -H "Authorization: Bearer $TOKELY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5.1-codex",
    "input": "Hello!",
    "max_output_tokens": 1024,
    "store": false
  }'

Set TOKELY_API_KEY to your dashboard key. Requests require a funded Tokely balance. Base URL: https://api.tokely.me/v1.

Capabilities & limits

Context window
400,000 tokens
Model max output
128,000 tokens
Cached input price
$0.100834 per 1M tokens · Official: $0.125
Provider
OpenAI
API model ID
gpt-5.1-codex
Category
Text
Endpoints
POST /v1/responses
Tokely max output
65,536 tokens / request, including reasoning tokens
Default output
256 tokens. Set an explicit limit for longer responses.
Request limits
256 KB JSON body · 128 messages · 32 function tools
Rate limit
60 requests / minute / account, across its keys
Supported input
Text messages and function tool results
Model modalities
text, image. Tokely currently accepts text input.

The context includes your instructions, conversation history, tool definitions and generated output. Keep the input and requested output within the model’s context window.

API reference

Authenticate with Authorization: Bearer YOUR_TOKELY_API_KEY. Use an OpenAI SDK with the Tokely base URL.

model
Required string: gpt-5.1-codex
input
Text or an array of text messages and function call results. Send history in each request; use store=false.
max_output_tokens
Optional integer, 1–65,536. Defaults to 256.
stream
Streaming has not been verified for this model.
reasoning.effort
Optional reasoning effort. Supported values depend on the model; omit to use its default.
tools
Function definitions executed by your application. Provider-hosted tools are not enabled.

The response contains output items and usage (input_tokens, output_tokens, total_tokens). Streaming uses named Responses events.

400 / 415
Invalid request, parameter, endpoint for this model, or content type.
401 / 403
Invalid, revoked or restricted API key.
402
Insufficient account balance or API key budget.
429
Request limit reached. Retry after the indicated delay.
502 / 503 / 504
Upstream failure, temporary service unavailability or request timeout.

Compare nearby prices

USD per million tokens. Compare price and context; these are not quality benchmarks.
ModelInputOutputContext
GPT-5.1 CodexOpenAI · this model$1.008334$8.066667400,000
GPT-5.3 CodexOpenAI$1.05875$8.47400,000
GPT-6 AstraOpenAI$2.527938$7.5838131,050,000
Gemini 3 ProGoogle$0.833334$5.833334128,000
Gemini 3.1 ProGoogle$0.833334$5.833334128,000

Frequently asked questions

How much does GPT-5.1 Codex cost?

$1.008334 per million input tokens, $8.066667 per million output tokens and $0.100834 per million cached input tokens. Usage is charged to your Tokely balance.

Do I need a separate OpenAI account?

Use your Tokely API key and balance. A separate provider key is not required.

How do I switch to this model?

Set model to gpt-5.1-codex and use /v1/responses. Keep your Tokely base URL and API key.

What is the context window?

400,000 tokens, including input and output. The Tokely request body and output limits listed above also apply.

Playground

Explore this model in the Tokely Playground.

Open in playground