openai/gpt-5.3-codexGPT-5.3 Codex is OpenAI’s proprietary AI model, released Feb 5, 2026. It costs $1.75/M input and $14/M output tokens, and handles a 400K-token context window. Its strongest use case is reasoning & knowledge, where it ranks in the 85th percentile of the models Model Beat tracks.
GPT-5.3-Codex is OpenAI’s most advanced agentic coding model, combining the frontier software engineering performance of GPT-5.2-Codex with the broader reasoning and professional knowledge capabilities of GPT-5.2.
Scores on standardized evaluations. Higher is better — and rank shows where GPT-5.3 Codex lands among all models tracked on Model Beat.
Graduate-level scientific reasoning
Frontier of human expert knowledge
Novel ML problem-solving
Scientific research coding
Real GitHub issue resolution
Human-rated web development
Multi-step agentic tasks
Autonomous task length
Command-line agentic tasks
Tool-agent-user reliability
GPT-5.3-Codex is OpenAI’s most advanced agentic coding model, combining the frontier software engineering performance of GPT-5.2-Codex with the broader reasoning and professional knowledge capabilities of GPT-5.2.
GPT-5.3 Codex is an AI model developed by OpenAI, part of the GPT family, released Feb 5, 2026.
GPT-5.3 Codex's list price from OpenAI is $1.75 per million input tokens and $14 per million output tokens.
GPT-5.3 Codex supports a context window of up to 400K tokens.
On standardized evaluations tracked by Epoch AI, GPT-5.3 Codex scores 79.3% on WeirdML, 42.5% on Humanity's Last Exam, 78.4% on Terminal-Bench.
GPT-5.3 Codex is a proprietary model (API access), available through its provider's API rather than as a downloadable open-weight model.
Benchmark data from Epoch AI (CC BY) and Artificial Analysis; pricing, specs & descriptions from OpenRouter. Data updated Sep 17, 2026.