Lenny's Newsletter · Hamel Husain
articleplaybookAdvanced evals: How to find (and fix) hidden AI failures in your product
22 September 2026Product
Source excerpt
About Lenny's NewsletterWhy you should never skip error discovery
This is a limited feed-provided excerpt, not the full original work.
Apollo layer
What a founder can learn
Founder takeaway
Treat error discovery as a required stage of AI product evaluation: first identify and categorize hidden failure modes, then prioritize fixes based on their impact on users.
Why it matters
AI products can appear effective while still failing in consequential edge cases. A repeatable discovery process helps teams direct scarce engineering effort toward failures that most undermine customer value and trust.
Relevant guides
Put it to work
Review a representative sample of recent AI outputs and ask: What recurring failure categories appear, which users or workflows do they affect, and which single category should we fix first?
Private notes