Question 1

What is GPT-5.1 Codex?

Accepted Answer

GPT-5.1 Codex is a model from OpenAI, released on Nov 13, 2025. GPT-5.1-Codex is a specialized version of GPT-5.1 optimized for software engineering and coding workflows. $1.25 per million input tokens, $10 per million output tokens. 400,000 token context window, maximum output of 128,000 tokens. Higher uptime with 2 providers. Includes independent benchmarks from Artificial Analysis.

Question 2

How much does GPT-5.1 Codex 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 on Respan?

Accepted Answer

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

Question 4

What is GPT-5.1 Codex's context window?

Accepted Answer

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

Question 5

How do I use GPT-5.1 Codex 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". 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?

Accepted Answer

Over the last 30 days of requests through the Respan gateway, the fastest provider was OpenRouter at 15 tokens per second, and the lowest response latency was 1.5 seconds on OpenRouter. Speed varies with request size and provider.

Question 7

How does GPT-5.1 Codex score on benchmarks?

Accepted Answer

GPT-5.1 Codex has 4 published benchmark scores, including SWE-bench Verified 73.7% and LMArena WebDev 1337. 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`	400K	$1.25/M	$10.00/M
OpenAI`openai/gpt-5.1-codex`	400K	$1.25/M	$10.00/M
OpenRouter`openrouter/openai/gpt-5.1-codex`	400K	$1.25/M	$10.00/M

GPT-5.1 Codex

Providers

Certified where it counts.

Pricing

Cost by volume

Throughput and latency

Output speed

Response latency

Benchmarks

Coding3

Arena1

Apps

GPT-5.1 Codex FAQ

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