Google released Gemini 2.5 Pro as an experimental preview, a state-of-the-art reasoning model that led major benchmarks through the middle of 2025. It combined the 2.x generation's tool use with substantially stronger step-by-step thinking.

The experimental label didn't stop developers from adopting it widely; 2.5 Pro became the model to beat on coding and math evaluations for months. Google iterated it rapidly through the spring before a stable release.

Gemini 2.5 Pro's long benchmark reign set the stage for the Gemini 3 generation, which Google teased as a bigger leap later in 2025.