This entry is a serving variant of OpenAI: GPT-5.5 Pro. A variant shares its base model's tokenizer by construction, so the measurement lives on the base record and this page inherits it.
| Signal | Result | Reference |
|---|---|---|
| Tokenizer signature | Not measured | – |
| API surface | Identical contract to 2 other entries | api_79fd3702 |
| Context and output | 1,050,000 context · 128,000 max output | declared |
| Reasoning contract | Mandatory · efforts xhigh, high, medium · default medium | declared |
| Serving providers observed | None recorded yet | – |
GPT-5.5 Pro is OpenAI’s high-capability model optimized for deep reasoning and accuracy on complex, high-stakes workloads. It features a 1M+ token context window (922K input, 128K output) with support for...
Supported parameters
include_reasoningmax_tokensreasoningreasoning_effortresponse_formatseedstructured_outputstool_choicetools
defaults: {"temperature":null,"top_p":null,"top_k":null,"frequency_penalty":null,"presence_penalty":null,"repetition_penalty":null}
Cite this page as the evidence record for OpenAI: GPT-5.5 Pro (batch): the URL is stable, measurements are dated, and revisions append to the history above. Method: tokenizer fingerprinting, v1, 50 strings. The raw data behind every figure is on the data page.
