GPT-5.1-Codex

OpenAI · Released November 2025

GPT-5.1-Codex is a specialized version of GPT-5.1 optimized for software engineering and coding workflows. It is designed for both interactive development sessions and long, independent execution of complex engineering tasks....

It is part of OpenAI's GPT family, where Sol, Luna and Terra mark the current generation's capability tiers and Pro servings trade speed for deeper computation.

Facts and pricing

Provider

OpenAI

Context window

400K tokens

Input price

13.8 credits / 1M tokens ($1.25 raw)

Output price

110 credits / 1M tokens ($10.00 raw)

Vision (image input)

Yes

Tool calling

Yes

Extended reasoning

No

Credits are what Zeplik bills: 1 credit = $0.10, computed from the raw provider rate with a 1.10x margin. Raw prices shown per 1M tokens.

Try GPT-5.1-Codex now

What GPT-5.1-Codex is best for

• Writing, reviewing and refactoring code; agentic coding workflows
• Long documents: the 400K-token window holds lengthy reports, contracts or papers whole
• Working with images: screenshots, charts, photos and scanned documents alongside text
• Tool use and agents: reliably calls functions, so it can search, run skills and drive workflows

Example prompts

Prompts that suit a coding model like GPT-5.1-Codex:

• Refactor this function to be testable and write the tests
• Explain what this regex does and rewrite it to be readable
• Design a database schema for a multi-tenant invoicing app
• Review this pull request diff for correctness and edge cases

OpenAI family

All 68 OpenAI models

Frequently asked questions

What is GPT-5.1-Codex?

GPT-5.1-Codex is an AI model by OpenAI. GPT-5.1-Codex is a specialized version of GPT-5.1 optimized for software engineering and coding workflows. It is designed for both interactive development sessions and long, independent execution of complex engineering tasks....

How much does GPT-5.1-Codex cost on Zeplik?

Input tokens cost 13.8 credits per million and output tokens 110 credits per million (1 credit = $0.10; the raw provider rates are $1.25 and $10.00 per million). New accounts start with free credits.

How long can a conversation with GPT-5.1-Codex be?

GPT-5.1-Codex has a 400K-token context window (400,000 tokens), which covers the conversation plus any documents you attach.

Does GPT-5.1-Codex support images and tools?

GPT-5.1-Codex accepts image input and supports tool calling.

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