---
title: "ILHA002: Atom/watch slot count changed"
description: A component created a different number of atom and watch slots on a later render.
---

Primitives are order-based. Ilha stores each `atom()` and `watch()` in a slot and matches slots to calls by position. When a render creates a different number of slots than the last one, Ilha warns with `ILHA002`.

## Why it happens

You wrapped a primitive in a condition, a loop, or an early return, so the call count depends on state.

## Bad

```tsx
import { atom } from "ilha";

const Panel = ({ open }: { open: boolean }) => {
  if (open) {
    const draft = atom("");
    return <input value={draft()} />;
  }
  return <p>Closed</p>;
};
```

## Fixed

Call primitives unconditionally and in the same order. Put the condition inside the view:

```tsx twoslash
import { atom } from "ilha";

const Panel = ({ open }: { open: boolean }) => {
  const draft = atom("");
  return open ? <input value={draft()} /> : <p>Closed</p>;
};
```

For one-time or conditional work, use `atom.lazy(() => expensive())` or `watch.once()` instead of guarding the call.