OpenAI: GPT-5.1-Codex

openai/gpt-5.1-codex · OpenAINot yet established

Declared family: GPT
Evidence confidence: Unknown
Declared tokenizer tag: GPT
Entered catalogue: 13 November 2025
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	No other entry shares this exact contract	api_37595400
Context and output	400,000 context · 128,000 max output	declared
Reasoning contract	Mandatory · efforts high, medium, low · default medium	declared
Serving providers observed	None recorded yet	–

Declared record

What the catalogue claims about this model

GPT-5.1-Codex is a specialized version of GPT-5.1 optimized for software engineering and coding workflows. It is designed for both interactive development sessions and long, independent execution of complex engineering tasks....

Modalities: text+image->text
Declared tokenizer: GPT
Prompt price: $1.25 / M tokens
Completion price: $10.0 / M tokens

Supported parameters

include_reasoningmax_completion_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

13 November 2025Enters the OpenRouter catalogue declared as GPT.

Cite this page as the evidence record for OpenAI: GPT-5.1-Codex: 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.