Google I/O 2026 had the headline stuff. Gemma 4 in four sizes. The new agent-friendly Gemini surfaces. Genie. Project Mariner stuff. All worth talking about.
But the announcement that's actually going to change which agents make sense to build, and which ones I kill on the spreadsheet, isn't any of those. It's the cache-discount pricing tier on Gemini 2.5 Flash.
I'm the person who maintains GeminiLens, an open-source observability layer for Gemini agents. Cost calc is a core part of that lib. I had to rewrite the calc the day after the keynote. Here's why.
The old math
Before I/O 2026, my mental model for a high-frequency Gemini agent looked like this:
