GPT-5.3-Codex
The most capable agentic coding model to date. Optimized for agentic coding tasks in Codex or similar environments. 400K context, 128K max output. Reasoning off by default.
You always get the exact model you pick — we never silently route you to another.
About GPT-5.3-Codex
Built to write, debug, and ship code autonomously, GPT-5.3-Codex is OpenAI's purpose-built agentic coding model — the one the Codex team itself used to manage deployment and diagnose test failures while training it. Where it earns loyalty is in sustained, multi-step work: users who push it through repository searches, PR creation, debugging sessions, and DevOps tasks report it "feels smarter" and becomes their default coding tool. It runs 25% faster than its predecessor, scores 57% on SWE-Bench Pro, and costs roughly half the output price of GPT-5.5 at $14.00 per million output tokens. The tradeoff is real, though: first-token latency sits around 80 seconds — far above the norm for reasoning models — and the model can go off-script, making autonomous decisions that ignore architectural guidelines. It is a specialist, not a generalist, and as of June 2026, OpenAI has announced its sunset from Codex subscription offerings, so availability may be limited.
Best for
- Agentic coding workflows that span multiple steps — repository search, terminal commands, debugging, and PR creation in a single session
- Interactive development where you steer the model mid-execution and keep it on track without losing context
- Code review, refactoring, and optimization across languages where detailed, verbose reasoning is welcome
- DevOps and infrastructure tasks requiring system-level command execution and deployment automation
- Long-running research and development sessions involving complex tool-call sequences
Specifications
| Provider | OpenAI |
|---|---|
| Released | 2026-02-05 |
| Intelligence | High |
| Speed | Medium |
| Context window | 400,000 tokens |
| Max output | 128,000 tokens |
| Knowledge cutoff | August 31, 2025 |
| Input price | $1.75 / 1M tokens |
| Output price | $14.00 / 1M tokens |
| Request cost | 1 premium request |
| Plan tier | Premium+ |
| Model ID | gpt-5.3-codex |
Frequently asked questions
Input is $1.75 per million tokens, output is $14.00 per million tokens, and cached input drops to $0.175 per million tokens. That makes it roughly 2x cheaper on output than GPT-5.5.
400,000 tokens, with a maximum output of 128,000 tokens. OpenAI engineered a 'Perfect Recall' mechanism to reduce information degradation across that extended context.
Agentic coding: multi-step tasks that combine code generation, tool use, terminal access, and decision-making. It scored 57% on SWE-Bench Pro and 64.7% on OSWorld-Verified.
Time-to-first-token averages around 80 seconds, far above the roughly 2.75-second median for comparable reasoning models. It can also make autonomous decisions outside the scope of what you asked, and its verbosity raises costs.
GPT-5.3-Codex is purpose-built for coding and agentic tasks and costs significantly less on output. GPT-5.5 is the stronger choice for general-purpose reasoning and broader applications.
As of June 2026, OpenAI has announced the sunset of GPT-5.3-Codex from Codex subscription offerings, so access may be limited or changing. Check OpenAI's current model availability for the latest status.