Plain-English Summary
A late-2025 GPT-5 series model for coding and agentic tasks, with configurable reasoning effort. Superseded by newer GPT-5.x releases.
GPT-5.1
A late-2025 GPT-5 series model for coding and agentic tasks, with configurable reasoning effort. Superseded by newer GPT-5.x releases.
Maker
OpenAI
GPT-5
Reasoning LLM
Legacy
Open weights: No
API: Yes
Technical Notes
Reasoning model with 400K context, 128K max output, text and image input, and configurable reasoning effort.
Best For
Coding and agentic tasks at a lower price than newer GPT-5.x models
Watch Out For
Older knowledge cutoff (Sep 2024); superseded by newer GPT-5.x models.
Model Specs
- Maker
- OpenAI
- Country
- USA
- Family
- GPT-5
- Type
- Reasoning LLM
- Release date
- 2025-11-13
- Date confidence
- Model ID date
- Status
- Legacy
- Context window
- 400,000 tokens
- Max output
- 128,000
- Parameters
- Not disclosed
- Active parameters
- Not disclosed
- Architecture
- Not listed
- Reasoning
- Yes — configurable effort
- Tool calling
- Yes
- Structured output
- Yes
- API available
- Yes
- Open weights
- No
- Self-hostable
- No
- License
- Proprietary
- Inputs
- Text, image
- Outputs
- Text
- Approx. price
- $1.25 input / $10 output per 1M tokens
- How to access
- OpenAI API
- Model / API ID
- gpt-5.1-2025-11-13
- Knowledge cutoff
- 2024-09-30
- Fine-tuning
- Not listed
- Completeness
- Not listed
- Verified
- Snapshot date
- Source
- Official source