Using GPT-5.1 Codex Max on Vercel AI Gateway

Implementation guide · GPT-5.1 · OpenAI

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Vercel AI Gateway exposes GPT-5.1 Codex Max through model ID openai/gpt-5.1-codex-max. Use the setup steps, sourced pricing, capabilities, and official provider links below to validate this route before deployment.

Last refreshed 2026-06-29. Next refresh: weekly.

Quick Start

1
Create an account at Vercel AI Gateway and generate an API key.
2
Use the Vercel AI Gateway SDK or REST API to call openai/gpt-5.1-codex-max — see the documentation for request format.
3
You'll be billed $1.25/1M input, $10.00/1M output tokens. See full pricing.

API Portal Documentation Pricing Model Card

Code Examples

Install

pip install openai

API key

AI_GATEWAY_API_KEY

Model ID

openai/gpt-5.1-codex-max

creator/model-name e.g. kwaipilot/kat-coder-pro-v2

import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["AI_GATEWAY_API_KEY"],
    base_url="https://ai-gateway.vercel.sh/v1"
)
response = client.chat.completions.create(
    model="openai/gpt-5.1-codex-max",
    messages=[{"role": "user", "content": "Hello"}]
)
print(response.choices[0].message.content)

Pricing on Vercel AI Gateway

Type	Price (per 1M)
Input tokens	$1.25
Output tokens	$10.00
Query	$10.00

Capabilities

VisionMultimodalReasoningJSON / Tool useStructured Outputs

About GPT-5.1 Codex Max

OpenAI's GPT-5.1-Codex-Max is a code-specialized model released November 19, 2025, optimized for agentic coding tasks including project-scale refactors, debugging, and multi-file edits. Uses context compaction to handle long-running tasks beyond a single context window. 30% more token-efficient than previous Codex on SWE-bench. Supports an extra-high reasoning effort option.

Full model details →

Model Specs

Released2025-11-19

Knowledge cutoff2024-09

Vercel