GPT-5.5 is OpenAI's latest flagship reasoning model, positioned as a step toward agentic computing where a single prompt can drive multi-step work. The release emphasizes planning, tool use, self-checking, and persistence through ambiguity, with particular strength in agentic coding, computer use, knowledge work, and early scientific research. Rather than just answering questions, GPT-5.5 is designed to carry complex tasks across tools and documents until they are finished, making it well suited to messy, multi-part assignments that mix research, writing, analysis, and software operations.

On OpenRouter, the model is exposed as a frontier-tier offering with multimodal input, structured output support, and a that quick-info value window that comfortably exceeds a million tokens, enabling very long documents, codebases, or agent sessions in a single call. Provider-level performance varies noticeably: an Azure-backed route delivers a sub-two-second best P50 latency at modest throughput, while the OpenAI-direct route is slower but produces substantially higher tokens-per-second, letting users trade responsiveness for raw generation speed. The combination of deep reasoning, tool-calling, and a tiered pricing structure that scales up for the largest contexts makes GPT-5.5 a natural fit for developers building autonomous agents, long-horizon research assistants, and complex data or coding pipelines that benefit from sustained, context-aware execution.