OpenAI: GPT Chat Latest is OpenAI's model. Its measured tokenizer sits with the GPT group, which is evidence that it builds on the GPT tokenizer. Tokenizer reuse is normal engineering, open vocabularies travel between labs, and this says nothing against OpenAI's authorship of the model itself.
| Signal | Result | Reference |
|---|---|---|
| Tokenizer signature | Exact match with 31 other models | tk_d1411c9d |
| API surface | No other entry shares this exact contract | api_3d182ea6 |
| Context and output | 400,000 context · 128,000 max output | declared |
| Reasoning contract | None declared | declared |
| Serving providers observed | OpenAI | measured 3 September 2026 |
Click a row to open the full comparison.
An x marks a row excluded as corrupt (caching or provider interference detected during measurement). Overhead subtracted: 6 prompt tokens.
GPT Chat Latest points to OpenAI's stable API alias `chat-latest` that always resolves to the latest Instant chat model used in ChatGPT. As OpenAI rolls out new Instant model updates...
Supported parameters
max_tokensresponse_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 Chat Latest: the URL is stable, measurements are dated, and revisions append to the history above. Method: tokenizer fingerprinting, v1, 50 strings.
