- Native context
- Official native specification: 400,000 tokens
- Input methods
- Text, images; can be combined with screenshots and written task instructions
- Primary outputs
- Text responses, code, analysis results, and function call requests
- Coding focus
- Targeted editing, codebase navigation, frontend generation, debugging
- Tool collaboration
- Native support for tool use and function calling
- Platform interaction
- Standard text or streamed text; message history is organized by the application according to the selected protocol
- Invocation controls
- Streaming responses, output length control; reasoning settings depend on the selected endpoint
- Native maximum input
- 272,000 tokens; must be planned together with output
- Native maximum output
- 128,000 tokens
400K is the native context specification for GPT-5.4 mini. Platform multimodal and tool inputs are handled according to public protocols, while relevant history and execution results are organized by the application and passed into subsequent requests.