fix: remove document listeners on dispose

lib/selection-manager.ts

@@ -61,6 +61,7 @@ export class SelectionManager {
   private boundContextMenuHandler: ((e: MouseEvent) => void) | null = null;
   private boundClickHandler: ((e: MouseEvent) => void) | null = null;
   private boundDocumentMouseMoveHandler: ((e: MouseEvent) => void) | null = null;
+  private boundDocumentMouseDownHandler: ((e: MouseEvent) => void) | null = null;
 
   // Auto-scroll state for drag selection
   private autoScrollInterval: ReturnType<typeof setInterval> | null = null;
@@ -405,6 +406,12 @@ export class SelectionManager {
       this.boundDocumentMouseMoveHandler = null;
     }
 
+    // Clean up document mousedown listener
+    if (this.boundDocumentMouseDownHandler) {
+      document.removeEventListener('mousedown', this.boundDocumentMouseDownHandler);
+      this.boundDocumentMouseDownHandler = null;
+    }
+
     // Clean up context menu event listener
     if (this.boundContextMenuHandler) {
       const canvas = this.renderer.getCanvas();
@@ -566,9 +573,10 @@ export class SelectionManager {
     document.addEventListener('mousemove', this.boundDocumentMouseMoveHandler);
 
     // Track mousedown on document to know if a click started inside the canvas
-    document.addEventListener('mousedown', (e: MouseEvent) => {
+    this.boundDocumentMouseDownHandler = (e: MouseEvent) => {
       this.mouseDownTarget = e.target;
-    });
+    };
+    document.addEventListener('mousedown', this.boundDocumentMouseDownHandler);
 
     // CRITICAL FIX: Listen for mouseup on DOCUMENT, not just canvas
     // This catches mouseup events that happen outside the canvas (common during drag)

lib/terminal.test.ts

@@ -160,6 +160,44 @@ describe('Terminal', () => {
       // open() is synchronous and throws immediately
       expect(() => term.open(container!)).toThrow('has been disposed');
     });
+
+    test('removes every document listener it added on dispose', async () => {
+      // A listener left on document keeps the terminal, its renderer and its
+      // canvas alive after dispose().
+      const added = new Set<EventListenerOrEventListenerObject>();
+      const originalAdd = document.addEventListener;
+      const originalRemove = document.removeEventListener;
+      document.addEventListener = function (
+        this: Document,
+        type: string,
+        listener: any,
+        opts?: any
+      ) {
+        added.add(listener);
+        return originalAdd.call(this, type, listener, opts);
+      } as typeof document.addEventListener;
+      document.removeEventListener = function (
+        this: Document,
+        type: string,
+        listener: any,
+        opts?: any
+      ) {
+        added.delete(listener);
+        return originalRemove.call(this, type, listener, opts);
+      } as typeof document.removeEventListener;
+
+      try {
+        const term = await createIsolatedTerminal();
+        term.open(container!);
+        expect(added.size).toBeGreaterThan(0);
+
+        term.dispose();
+        expect(added.size).toBe(0);
+      } finally {
+        document.addEventListener = originalAdd;
+        document.removeEventListener = originalRemove;
+      }
+    });
   });
 
   describe('Properties', () => {

lib/terminal.ts

@@ -1260,8 +1260,10 @@ export class Terminal implements ITerminalCore {
       this.element.removeAttribute('aria-multiline');
     }
 
-    // Remove document-level listeners (only if opened)
-    if (this.isOpen && typeof document !== 'undefined') {
+    // Remove document-level listeners. dispose() clears isOpen before it
+    // gets here, so this cannot depend on it; removing a listener that was
+    // never added is a no-op.
+    if (typeof document !== 'undefined') {
       document.removeEventListener('mouseup', this.handleMouseUp);
     }