GPT-5.1-Codex-Max

OpenAI · Released December 2025

GPT-5.1-Codex-Max is OpenAI’s latest agentic coding model, designed for long-running, high-context software development tasks.

It is part of OpenAI's GPT family, where GPT-6 Astra leads, GPT-6 Sol and GPT-6 Luna cover the capability and speed tiers below it, the GPT-5.6 generation sits behind them, and Pro servings trade speed for deeper computation.

Facts and pricing

Provider

OpenAI

Context window

400K tokens

Input price

15.0 credits / 1M tokens ($1.25 raw)

Output price

120 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 1.20x margin. Raw prices shown per 1M tokens.

Try GPT-5.1-Codex-Max now

What GPT-5.1-Codex-Max 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-Max:

• 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 71 OpenAI models

Model comparisons

• Claude Opus 5.5 vs GPT-6 Astra
• Claude Opus 5.5 vs GPT-6 Sol
• GPT-6 Sol vs GPT-5.6 Sol
• GPT-6 Sol vs GPT-6 Astra

Frequently asked questions

What is GPT-5.1-Codex-Max?

GPT-5.1-Codex-Max is an AI model by OpenAI. GPT-5.1-Codex-Max is OpenAI’s latest agentic coding model, designed for long-running, high-context software development tasks.

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

Input tokens cost 15.0 credits per million and output tokens 120 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-Max be?

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

Does GPT-5.1-Codex-Max support images and tools?

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

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