Real Bugs We Found in Popular Repos

Auto-save effect re-runs on every render

const handleAutoSave = () => { ... scheduleSave(fieldState); };

useEffect(() => {
  localStorage.setItem(localStorageKey, JSON.stringify(fieldState));
  handleAutoSave();
}, [fieldState, localStorageKey, handleAutoSave]);

Why it breaks: handleAutoSave is a new function on every render, so the dependency array changes every time. The effect writes to localStorage and schedules a remote save after every render, not only when the field changes.

Fix: Wrap handleAutoSave in useCallback, or drop it from the dependencies and call scheduleSave directly inside the effect.

Deleting a user fails because of the schema

create table users (
  id uuid references auth.users not null primary key,
  ...
);

Why it breaks: The foreign key to auth.users has no ON DELETE rule. When you delete the user from the Supabase dashboard (or a GDPR request comes in), Postgres refuses with a foreign key violation. Supabase has a public issue about exactly this error.

Fix: Use references auth.users on delete cascade, so the profile row goes away with the account.

Fixed 800px width overflows phones

<div className="mx-auto w-[800px] space-y-6">

Why it breaks: A hard 800px width is wider than every phone screen, so the editor loading state scrolls sideways on mobile.

Fix: Use w-full max-w-[800px] so it fills small screens and caps at 800px on desktop.

Same user-deletion trap in an example migration

user_id UUID REFERENCES auth.users(id)

Why it breaks: Even the official client repo has a table that blocks deleting a user who owns todos. Code copied from examples like this is how the bug spreads into AI-generated apps.

Fix: REFERENCES auth.users(id) ON DELETE CASCADE (or SET NULL if the rows must outlive the user).

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