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.agents/skills/vercel-composition-patterns/rules/architecture-avoid-boolean-props.md

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+---
+title: Avoid Boolean Prop Proliferation
+impact: CRITICAL
+impactDescription: prevents unmaintainable component variants
+tags: composition, props, architecture
+---
+
+## Avoid Boolean Prop Proliferation
+
+Don't add boolean props like `isThread`, `isEditing`, `isDMThread` to customize
+component behavior. Each boolean doubles possible states and creates
+unmaintainable conditional logic. Use composition instead.
+
+**Incorrect (boolean props create exponential complexity):**
+
+```tsx
+function Composer({
+  onSubmit,
+  isThread,
+  channelId,
+  isDMThread,
+  dmId,
+  isEditing,
+  isForwarding,
+}: Props) {
+  return (
+    <form>
+      <Header />
+      <Input />
+      {isDMThread ? (
+        <AlsoSendToDMField id={dmId} />
+      ) : isThread ? (
+        <AlsoSendToChannelField id={channelId} />
+      ) : null}
+      {isEditing ? <EditActions /> : isForwarding ? <ForwardActions /> : <DefaultActions />}
+      <Footer onSubmit={onSubmit} />
+    </form>
+  );
+}
+```
+
+**Correct (composition eliminates conditionals):**
+
+```tsx
+// Channel composer
+function ChannelComposer() {
+  return (
+    <Composer.Frame>
+      <Composer.Header />
+      <Composer.Input />
+      <Composer.Footer>
+        <Composer.Attachments />
+        <Composer.Formatting />
+        <Composer.Emojis />
+        <Composer.Submit />
+      </Composer.Footer>
+    </Composer.Frame>
+  );
+}
+
+// Thread composer - adds "also send to channel" field
+function ThreadComposer({ channelId }: { channelId: string }) {
+  return (
+    <Composer.Frame>
+      <Composer.Header />
+      <Composer.Input />
+      <AlsoSendToChannelField id={channelId} />
+      <Composer.Footer>
+        <Composer.Formatting />
+        <Composer.Emojis />
+        <Composer.Submit />
+      </Composer.Footer>
+    </Composer.Frame>
+  );
+}
+
+// Edit composer - different footer actions
+function EditComposer() {
+  return (
+    <Composer.Frame>
+      <Composer.Input />
+      <Composer.Footer>
+        <Composer.Formatting />
+        <Composer.Emojis />
+        <Composer.CancelEdit />
+        <Composer.SaveEdit />
+      </Composer.Footer>
+    </Composer.Frame>
+  );
+}
+```
+
+Each variant is explicit about what it renders. We can share internals without
+sharing a single monolithic parent.