Reviewing code you did not write

You are going to merge a lot of code you did not type. Reviewing it is a different skill from writing it, and it is the one that actually keeps a vibe-coded project alive past week three. Read the diff, not the summary. The summary is what the model believed it did. The diff is what it did. Check the edges the model was never told about. Empty inputs, a user who is signed out, a list with zero items, a network call that fails. Models write the happy path unprompted and the rest only when asked. Ask what else calls this. A change that fixes one caller and breaks two others still passes the test you were looking at. Be suspicious of new dependencies. A package added to save five lines of work is five lines of work plus a supply chain.