GPT-5.3-Codex
GPT-5.3-Codex is a deprecated model specialized for coding agents. It was designed for Codex and similar environments with tools and source files.
Deprecated API; check access details
Coding specialization includes reasoning controls
The model supports low, medium, high and xhigh effort. Its documented context is 400,000 tokens, with a separate 272,000-token input ceiling. It is a model release, not the Codex application itself.GPT-5.3-Codex official model documentation
Review an existing integration
Practical guidance. Compare a replacement on complete repository tasks, including file inspection, edits and validation. Review whether it follows project constraints and preserves unrelated changes. A correct code snippet alone does not establish a successful agent workflow.
Specifications & access
| Detail | Value and conditions |
|---|---|
| Status | Deprecated API; check access details |
| Access | API |
| Model identifiers | gpt-5.3-codex |
| Context window | 400,000 tokens Published context for this deprecated release GPT-5.3-Codex official model documentation |
| Maximum output | 128,000 tokens Published maximum output, bounded by the remaining context GPT-5.3-Codex official model documentation |
| Provider status | Deprecated in the current OpenAI model catalog; confirm remaining account access.GPT-5.3-Codex official model documentation |