Gemini 3.5 Pro stays in limited Vertex preview

Gemini 3.5 Pro was expected for general availability in June 2026 but was pushed back after early enterprise testing surfaced token-efficiency issues, a coding performance regression compared to Gemini 3.1, and unresolved gaps in long multi-step reasoning. Google subsequently scrapped the Gemini 2.5 Pro base model entirely and launched a new pre-training cycle targeting mathematical reasoning, SVG scene generation, and image quality. GA is now confirmed for July 17. As of July 7, the model is available only to Vertex AI enterprise preview customers.