GPT-5.1-Codex
GPT-5.1-Codex is the GPT-5.1 coding specialization for Codex and comparable tool-based development environments. It combines reasoning, image understanding, and text generation for implementation and repository work, with Responses API access. It is a distinct coding model identity; the Codex application and its underlying harness are separate products.
2025-11-13
Unreleased
Undisclosed proprietary architecture
Proprietary
Specifications
- Parameters
- Unreleased
- Architecture
- Undisclosed proprietary architecture
- License
- Proprietary
- Context Window
- 400,000 tokens
- Max Output
- 128,000 tokens
- Training Data Cutoff
- Sep 30, 2024
- Type
- multimodal
- Modalities
- textimage
Benchmark Scores
Advanced Specifications
- Model Family
- GPT-5
- API Access
- Not Available
- Chat Interface
- Not Available
- Variants
- gpt-5.1-codex
Capabilities & Limitations
- Capabilities
- agentic codingcode reviewdebuggingvisiontool use
- Known Limitations
- Can produce incorrect factual claims or code; important results require independent verification.This API identity was retired on July 23, 2026; preserved for historical coverage.
- Notable Use Cases
- coding assistantsrepository changessoftware testing
- Function Calling Support
- Yes
- Tool Use Support
- Yes