OpenAI: GPT-5.6 Terra Pro

GPT-5.6 Terra Pro is a text model from OpenAI, released by the provider on 9 July 2026. It shares its underlying model with GPT-5.6 Terra, but it is served with reasoning.mode set to pro, which is aimed at higher-quality responses on complex tasks. If you are already familiar with the Terra line, the practical difference here is the serving mode rather than a different base model.

On the input side, the model accepts text, images and files, and it produces text output. It has a context length of 1,050,000 tokens and a maximum output of 128,000 tokens, with a knowledge cutoff of 16 February 2026. The large context window means you can send long documents, multiple files or extended conversation histories in a single request without splitting them up, and the generous output ceiling supports long-form generation in one call.

Those capabilities point to work where the input is large and the reasoning is demanding. Document and file analysis over long contracts, reports or codebases is a natural fit, since files and text can be supplied directly. Image inputs allow tasks that combine visual material with written instructions, such as interpreting screenshots, diagrams or scanned pages alongside a question. Because the model is served in pro mode, it suits multi-step problems where answer quality matters more than latency or throughput, including structured extraction, careful review of technical material and tool-driven workflows.

You call it through api14's OpenAI-compatible API using the model id "openai/gpt-5.6-terra-pro". The supported request parameters are include_reasoning, max_completion_tokens, max_tokens, reasoning, reasoning_effort, response_format, seed, structured_outputs, tool_choice, tools and verbosity. In practice, tools and tool_choice cover function calling, response_format and structured_outputs cover shaped output such as JSON, and the reasoning and verbosity parameters let you tune how much internal work and how much explanation the model produces. If you already have an OpenAI-compatible client, switching to this model is a matter of changing the model id and, where relevant, adding the parameters above.

One thing to weigh before adopting it: pro mode spends far more than the standard serving of the same model, so it is best reserved for requests that genuinely need the extra quality. For high-volume, latency-sensitive or simpler text tasks, the non-pro GPT-5.6 Terra is likely the more sensible default, and you can route only the hard cases to this model.