OpenAI Ships GPT-5.5 Six Weeks After GPT-5.4

OpenAI shipped GPT-5.5 on April 23, with GPT-5.5 Pro and both API endpoints following on April 24. The company called it the smartest and most intuitive model yet. Six weeks after GPT-5.4. Six weeks. Model launches are starting to look like point releases of a productivity app, which is roughly the framing Fortune used to cover the announcement.

The visibility-side question is whether citation behavior changes again. It usually does. When ChatGPT moved from GPT-5.2 to GPT-5.3 Instant in early March, French SEO firm Resoneo measured a 20% drop in the average number of websites cited per response. Sources retrieved went up. Sources cited went down. The model got more selective.

Whether GPT-5.5 tightens that pattern further or loosens it isn’t measurable yet. What’s worth doing this week for any business with skin in the AI visibility game: rerun your usual prompt set against the new model. Note which pages still get cited and which ones dropped out. Look for new arrivals. Patterns shift fastest in the first ten days after a model swap.

A couple of details from the rollout. GPT-5.5 is the default for Plus, Pro, Business, and Enterprise plans in ChatGPT and Codex. GPT-5.5 Pro is rolling out to Pro, Business, and Enterprise. The API gained both versions on April 24. OpenAI also reported four million active Codex users and nine million paid business seats for ChatGPT, numbers that were not in the room a year ago.

Sources: OpenAI, April 23, 2026. Fortune, April 23, 2026. CNBC, April 23, 2026.