Gemini 2.5 Flash, released April 17, 2025, brought hybrid reasoning to Google's high-volume tier: developers could turn thinking on or off and set an exact token budget for it, trading accuracy against latency and cost per request. It was the first model to expose that dial explicitly, and the design was widely copied.

Positioned as the workhorse of the 2.5 generation, Flash delivered a large share of 2.5 Pro's capability at a fraction of the price, making it one of the most heavily used API models of 2025 for chat products, summarisation, and agent sub-tasks. Flash-Lite followed in June 2025 to cover the ultra-low-cost end of the lineup.