GPT-5.3-Codex
OpenAICodeProprietaryOpenAI's most capable agentic coding model combining frontier coding performance with deep reasoning. Handles long-running tasks involving research, tool use, and complex execution. Can be steered interactively while working.
Abilities
Use Cases
Available in Tools
Availability
How to Use
Pros
- State-of-the-art coding performance — 56.8% on SWE-Bench Pro and 75.1% on Terminal-Bench 2.0
- 400K token context window — can process entire large codebases in a single session
- Interactive steering — redirect mid-task without losing context, like working with a colleague
- 25% faster than predecessor Codex models
- 90% prompt caching discount significantly reduces repeat-query costs
- Integrations with GitHub, Slack, Linear, and MCP support
Cons
- High output token pricing at $14/1M — verbose responses amplify costs
- Significant latency (~98 seconds time-to-first-token) due to extended thinking
- Can hallucinate files in large codebases — references components that do not exist
- No fine-tuning support
- Not optimized for conversational use — use GPT-5.4 for chat scenarios
What to Use It For
Perfect For
Industry-leading SWE-Bench Pro and Terminal-Bench scores for cross-codebase coordination and feature implementation
Designed for multi-step tasks involving research, tool use, and execution with interactive steering
Good For
Deep code comprehension with 400K context for analyzing large codebases
Can plan and execute multi-step coding tasks autonomously in sandboxed environments
Not Recommended
~98 second time-to-first-token makes it unusable for real-time conversation
Try instead: GPT-5.4, GPT-4o
$14/1M output tokens with verbose responses adds up fast
Try instead: GPT-4.1 Mini
Do Not Use For
Extended thinking phase causes ~98 second time-to-first-token — completely unsuitable
Try instead: GPT-4o, GPT-4.1
Code-focused model — no image or audio capabilities
Try instead: GPT-Image-1, OpenAI TTS