OpenAI's naming chaos: GPT-4.5 and o1 were each once slated to be GPT-5

flowersslop · x · 2026-09-03

Leaker flowersslop recounts three "timelines" of OpenAI's model naming: GPT-4.5 was originally meant to be GPT-5; after reasoning was discovered, o1 was slated to be GPT-5; in the current timeline, 4.5 stayed 4.5, o1 stayed o1, and 4o became GPT-5. The author also admits having deleted a post denying GPT-4.5 would exist, illustrating how internal research shifts repeatedly scrambled release plans.

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