Question 1

What is GPT-5.1 Codex Max?

Accepted Answer

GPT-5.1 Codex Max is a model from OpenAI, released on Nov 19, 2025. GPT-5.1-Codex-Max is OpenAI’s latest agentic coding model, designed for long-running, high-context software development tasks. It is based on an updated version of the 5.1 reasoning stack and trained on agentic workflows spanning software engineering, mathematics, and research. GPT-5.1-Codex-Max delivers faster performance, improved reasoning, and higher token efficiency across the development lifecycle.

Question 2

How much does GPT-5.1 Codex Max cost?

Accepted Answer

On the Respan gateway, input starts at $1.25 per 1M tokens on every provider, and output starts at $10.00 per 1M tokens on every provider, after gateway discounts.

Question 3

Which providers serve GPT-5.1 Codex Max on Respan?

Accepted Answer

3 providers serve GPT-5.1 Codex Max: Azure OpenAI, OpenAI, and OpenRouter. Azure OpenAI requires your own provider API key (BYOK).

Question 4

What is GPT-5.1 Codex Max's context window?

Accepted Answer

GPT-5.1 Codex Max accepts up to 400K tokens of context on its largest provider route.

Question 5

How do I use GPT-5.1 Codex Max with the Respan gateway?

Accepted Answer

Point any OpenAI-compatible SDK at https://api.respan.ai/api/ with your Respan API key and set the model to "openai/gpt-5.1-codex-max". To set it up with a coding agent, copy the agent setup prompt at the top of this page.

Question 6

How fast is GPT-5.1 Codex Max?

Accepted Answer

Over the last 30 days of requests through the Respan gateway, the fastest provider was OpenRouter at 18 tokens per second, and the lowest response latency was 3.9 seconds on OpenRouter. Speed varies with request size and provider.

Question 7

How does GPT-5.1 Codex Max score on benchmarks?

Accepted Answer

GPT-5.1 Codex Max has 3 published benchmark scores, including SWE-Lancer IC SWE 79.9%. Each score links to where it was published; the data is collected by llmmetric.com.

Provider	Context	Input	Output
Azure OpenAIBYOK only`azure/gpt-5.1-codex-max`	400K	$1.25/M	$10.00/M
OpenAI`openai/gpt-5.1-codex-max`	400K	$1.25/M	$10.00/M
OpenRouter`openrouter/openai/gpt-5.1-codex-max`	400K	$1.25/M	$10.00/M

GPT-5.1 Codex Max

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