GPT-5.5 (Spud) Deep Dive: First From-Scratch Base Model Since GPT-4.5, and Why Most Users Won't Notice

GPT-5.5 (Spud) Deep Dive: First From-Scratch Base Model Since GPT-4.5 OpenAI released GPT-5.5 (internal codename "Spud") on April 23, 2026, with API access following on April 24. On the surface this looks like an incremental 0.5-version bump. Underne...