Technical Specifications

GPT-5.1 High

GPT-5.1 High is a specialized reasoning variant within OpenAI's GPT-5 model family, engineered to provide high-effort cognitive processing for complex analytical tasks. The model is built upon a modular architecture that integrates a dense language backbone with sparse Mixture-of-Experts (MoE) layers and a dedicated reasoning core. This design enables the system to implement adaptive reasoning, where it dynamically allocates computational budget by extending its internal thinking time for multi-step problems such as advanced mathematical proofs and architectural code refactors. Unlike standard models that produce immediate output, GPT-5.1 High generates hidden reasoning tokens to evaluate multiple solution paths before committing to a final response.

Technically, the model employs a modified transformer architecture with Multi-Head Attention (MHA) and utilizes absolute position embeddings to maintain structural coherence across its expanded context. A significant innovation in the GPT-5.1 series is the integration of a 'compaction' mechanism for context management, which prunes and summarizes historical tokens when nearing limits to maintain long-term session coherence without full context reset. The architecture also incorporates explicit planning hooks and safety guardrails that operate both pre- and post-generation, ensuring that complex reasoning chains remain aligned with intended constraints while minimizing latency for the user.

The model is primarily intended for technical and agentic workflows where deep analysis is prioritized over raw speed. Its use cases include autonomous debugging, long-running coding projects involving multiple files, and sophisticated data synthesis. By exposing 'reasoning effort' controls to developers, GPT-5.1 High allows for granular tuning of the model's persistence on difficult queries. This makes it particularly effective for professionals building reliable agentic systems that require consistent, high-fidelity outputs across varied domains including engineering, legal analysis, and scientific research.