Mechanism◆Article
Under-prompting frontier models — giving goals rather than detailed step-by-step instructions — produces better results because it forces the model to reason through the problem rather than mechanistically follow a script.
The counterintuitive insight that less-detailed prompts yield superior outcomes with advanced models by compelling genuine reasoning. ✦ AI generated
Claire Vo · Lenny's Newsletter · 2026-07-22 · original ↗
Why under-prompting frontier models gets better results than detailed step-by-step instructions
Read full article ↗excerpt · fair-use quotation
- ·Under-prompting frontier models outperforms detailed instructions
- ·Giving goals — not step-by-step scripts — forces genuine reasoning
- ·Mechanistic following of a script bypasses the model's strengths
- ·Detailed prompts let the model short-circuit its reasoning
- ·Goals compel the model to work through the problem itself
- ·Works best with frontier models capable of autonomous reasoning
Around this claim
This moment responds to
gives example → Codex browser use handles real-world personal tasks autonomously: clearing a LinkedIn inbox, shopping Free People for breastfeeding-friendly Hawaii clothes, and managing a router from out of state.Claire Vo · Lenny's Newslettersupports → Frontier models perform better and produce broader coverage when given room to decide how to approach a task rather than being handed a detailed checklist of steps.Claire · Lenny's Newslettergives example → Codex performed exhaustive QA testing on the onboarding flow, surfacing 11 issues including one high-severity blocker, with a Google Sheet of screenshots.Claire Vo · Lenny's Newslettergives example → EJ Lawless's persona-impersonation trick allows Codex to simulate different user perspectives, surfacing friction points the builder cannot see.Claire Vo · Lenny's Newsletterextends → Computer use can control iPhone mirroring, enabling a Mac to operate an iPhone and extending automation to mobile workflows.Claire Vo · Lenny's Newslettersupports → Enterprises should not rush to build cheaper structured workflows around lesser models to save money, because frontier models like Fable still deliver more value on an ad hoc basis and are themselves better at routing/delegating to cheaper models than most people are.Nathan · The Cognitive Revolution