Gemini 2.5 Flash Preview 09-2025 is Google's September 2025 preview of the next Gemini 2.5 Flash, scoring 54% on SWE-Bench Verified (up from 48.9%), improving agentic tool use, and producing 24% fewer output tokens with thinking enabled.
import { streamText } from 'ai'
const result = streamText({ model: 'google/gemini-2.5-flash-preview-09-2025', prompt: 'Why is the sky blue?'})Gemini 2.5 Flash Preview 09-2025 is a preview release from Google dated September 25, 2025. It advances the hybrid reasoning model that defined the 2.5 Flash tier. Two improvements stand out.
First, agentic tool use. Google called out better performance on complex, multi-step applications. The SWE-Bench Verified score moved from 48.9% to 54%, a five-point gain on real-world software engineering tasks involving bug fixes and feature implementations across production codebases.
Second, efficiency with thinking enabled. The preview produces 24% fewer output tokens compared to the stable model when thinking mode is active. Fewer thinking tokens means lower cost and faster responses on reasoning-intensive prompts while maintaining quality.
Like the Flash Lite preview released alongside it, this model uses Google's -latest alias system with two-week deprecation notices. Pin to gemini-2.5-flash-preview-09-2025 for stable evaluation. Google intends the preview for feedback collection, not as a direct replacement for the stable 2.5 Flash.