Simon Willison — 2026-04-15#

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The standout exploration today is Simon’s hands-on dive into Google’s new Gemini 3.1 Flash TTS API. It perfectly captures his rapid-prototyping ethos: encountering a surprisingly complex new prompting paradigm for an audio model and immediately using Gemini 3.1 Pro to “vibe code” a UI to stress-test regional British accents.

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Gemini 3.1 Flash TTS Google released Gemini 3.1 Flash TTS, an audio-only output model controlled via standard Gemini API prompts. Simon points out that the prompting guide is highly unusual, so he put it to the test by prompting for charismatic Newcastle and Exeter accents. To speed up his experimentation, he used Gemini 3.1 Pro to instantly vibe code a custom UI for the API.