AI Desk · Model Identity · Compare
OpenAI: GPT-5.6 Luna · OpenAI: o4 Mini High
Identity similarity: very highExact tokenizer agreement · 50/50Exact agreement across every measured string is strong evidence of shared tokenizer lineage. It shows shared ancestry, and does not on its own establish that these are the same release.
OpenAI: GPT-5.6 Luna recordOpenAI: o4 Mini High recordOpen in the interactive bench
Tokenizer fingerprint
50 of 50 mutually clean strings agree| Test string | OpenAI: GPT-5.6 Luna | OpenAI: o4 Mini High | Verdict |
|---|---|---|---|
| en-prose | 14 | 14 | match |
| en-long | 17 | 17 | match |
| spaces-20 | 3 | 3 | match |
| spaces-60 | 3 | 3 | match |
| tabs-20 | 3 | 3 | match |
| newlines-20 | 4 | 4 | match |
| mixed-ws | 6 | 6 | match |
| digits-9 | 3 | 3 | match |
| digits-12 | 4 | 4 | match |
| digits-30 | 10 | 10 | match |
| digits-sep | 7 | 7 | match |
| float-long | 9 | 9 | match |
| zh-common | 12 | 12 | match |
| zh-long | 17 | 17 | match |
| zh-rare | 20 | 20 | match |
| ja-kana | 10 | 10 | match |
| ja-kanji | 13 | 13 | match |
| ko | 11 | 11 | match |
| ru | 11 | 11 | match |
| ar | 11 | 11 | match |
| he | 10 | 10 | match |
| hi | 11 | 11 | match |
| th | 11 | 11 | match |
| el | 14 | 14 | match |
| emoji-basic | 8 | 8 | match |
| emoji-skin | 13 | 13 | match |
| emoji-zwj-family | 11 | 11 | match |
| emoji-zwj-x3 | 33 | 33 | match |
| emoji-flags | 16 | 16 | match |
| emoji-prof | 20 | 20 | match |
| math | 31 | 31 | match |
| boxdraw | 27 | 27 | match |
| combining | 11 | 11 | match |
| cjk-ext-b | 13 | 13 | match |
| surrogates | 40 | 40 | match |
| zalgo | 35 | 35 | match |
| rtl-mix | 5 | 5 | match |
| py-code | 25 | 25 | match |
| py-indent | 15 | 15 | match |
| json | 20 | 20 | match |
| html | 16 | 16 | match |
| regex | 44 | 44 | match |
| camel | 6 | 6 | match |
| snake | 6 | 6 | match |
| rare-word-x5 | 31 | 31 | match |
| repeat-tok | 22 | 22 | match |
| base64 | 34 | 34 | match |
| hex | 11 | 11 | match |
| url | 17 | 17 | match |
| uuid | 27 | 27 | match |
Values are the marginal prompt-token cost of each string with the model's fixed overhead subtracted. An x marks a row excluded as corrupt for that model.
API surface
The declared serving contracts differ| Field | OpenAI: GPT-5.6 Luna | OpenAI: o4 Mini High | Verdict |
|---|---|---|---|
| Context length | 1050000 | 200000 | × differs |
| Max output tokens | 128000 | 100000 | × differs |
| Supported parameters | include_reasoning, max_completion_tokens, max_tokens, reasoning, reasoning_effort, response_format, seed, structured_outputs, tool_choice, tools | include_reasoning, max_tokens, reasoning, reasoning_effort, response_format, seed, structured_outputs, tool_choice, tools | × differs |
| Defaults | {"temperature":null,"top_p":null,"top_k":null,"frequency_penalty":null,"presence_penalty":null,"repetition_penalty":null} | {"temperature":null,"top_p":null,"frequency_penalty":null} | × differs |
| Reasoning contract | {"mandatory":false,"default_enabled":true,"supported_efforts":["max","xhigh","high","medium","low","none"],"default_effort":"medium"} | {"mandatory":true,"supported_efforts":["high"],"default_effort":"high"} | × differs |
| Modalities | text+image+file->text | text+image+file->text | ✓ match |
Method: tokenizer fingerprinting, v1, 50 strings. This page is static and dated; the interactive bench compares any two of the 486 catalogue models.