o-series (reasoning)

Release history (8)

1. o4

   stableSep 15, 2025
   o4

   Full o4 (folded into GPT-5 router for many tiers).

2. o3 pro

   deprecatedJun 10, 2025
   o3-pro

   Higher compute o3.

3. o3

   deprecatedApr 16, 2025
   o3

   Full o3.

4. o4-mini

   stableApr 16, 2025
   o4-mini

   Reasoning at 4.1 cost.

5. o3-mini

   deprecatedJan 31, 2025
   o3-mini

   First o3 tier shipped.

6. o1

   deprecatedDec 5, 2024
   o1

   Full o1.

7. o1 pro

   deprecatedDec 5, 2024
   o1-pro

   Higher compute o1 tier.

8. o1-preview

   deprecatedSep 12, 2024
   o1-preview

   First inference-time-compute model.