The Missing Layer: Design Taste in AI Agents — Hassan El Mghari, Together AI

Most people can spot a vibe coded app in two seconds and cannot say why. Hassan El Mghari names it: the purple gradient background, italics in the header, a scroll to explore prompt nobody asked for, all caps pills with wide letter spacing, too many emoji. He reckons you could list thirty such tells, and naming them is what lets you tell an agent to avoid them. That is most of what Hallmark does, the design skill he shipped six weeks ago to more than 10,000 users. It codifies the patterns as gates and hands the model a library of themes, on the through line that strong inspiration produces much better work. El Mghari leads developer experience at Together AI and is not a designer. He has shipped roughly ten apps a year for five years, a few reaching millions of users, and credits design for that reach. He starts an app in Codex or Claude Code, then iterates with a smaller open source model, and made the case by putting up two landing pages, one from GLM 5.2 and one from Opus 4.8, and asking the room to guess which was which. Almost nobody could. The rest is practical: keep a vault of screenshots you admire and paste them in, the one habit he says to take away; record a voice note and let the prompt run three paragraphs; send one or two features per prompt instead of seven; write accumulated preferences into a skill file or AGENTS.md. Whatever the agent hands back is a base, never the finished app. Speaker info: - https://x.com/nutlope - https://www.linkedin.com/in/nutlope/ - https://nutlope.com Timestamps: 0:00 - Ten apps a year, and why design is the edge 1:41 - The apps: logos, comics, subtitles, a cloud agent 3:08 - The tells that give away a vibe coded app 4:11 - Hallmark: slop gates and a theme library 6:53 - Iterating with a smaller open source model 7:30 - Guess which page came from which model 10:50 - Give the agent references and screenshots 12:18 - One or two features per prompt