OpenAI: GPT-5.5

openai/gpt-5.5 · OpenAINot yet established

Declared family: GPT
Evidence confidence: Unknown
Declared tokenizer tag: GPT
Entered catalogue: 24 April 2026
Last tested: Not yet measured
Measurement: Awaiting measurement

Evidence stack

Signals of different kinds, weighed together

Signal	Result	Reference
Tokenizer signature	Not measured	–
API surface	Identical contract to 1 other entry	api_c6874b79
Context and output	1,050,000 context · 128,000 max output	declared
Reasoning contract	Optional · efforts xhigh, high, medium, low, none · default medium	declared
Serving providers observed	None recorded yet	–

Declared record

What the catalogue claims about this model

GPT-5.5 is OpenAI’s frontier model designed for complex professional workloads, building on GPT-5.4 with stronger reasoning, higher reliability, and improved token efficiency on hard tasks. It features a 1M+ token...

Modalities: text+image+file->text
Declared tokenizer: GPT
Prompt price: $5.00 / M tokens
Completion price: $30.0 / M tokens

Supported parameters

include_reasoningmax_completion_tokensmax_tokensreasoningreasoning_effortresponse_formatseedstructured_outputstool_choicetools

defaults: {"temperature":null,"top_p":null,"top_k":null,"frequency_penalty":null,"presence_penalty":null,"repetition_penalty":null}

Catalogue entry

History

Every observation, kept as taken

24 April 2026Enters the OpenRouter catalogue declared as GPT.

Cite this page as the evidence record for OpenAI: GPT-5.5: 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.