fix(coding-agent): close own custom ui overlay (#10999)

done() from ctx.ui.custom({ overlay: true }) closed the overlay with
ui.hideOverlay(), which removes the topmost overlay instead of the one
that called done(). With a shell overlay open under a dialog overlay
from another extension, the shell's exit removed the dialog: the
finished shell overlay stayed on screen ignoring input and the dialog's
promise never resolved. Hide the overlay through its own handle.

closes #10648

packages/coding-agent/src/modes/interactive/interactive-mode.ts

@@ -2989,12 +2989,14 @@ export class InteractiveMode {
 
 		return new Promise((resolve, reject) => {
 			let component: Component & { dispose?(): void };
+			let overlayHandle: OverlayHandle | undefined;
 			let closed = false;
 
 			const close = (result: T) => {
 				if (closed) return;
 				closed = true;
-				if (isOverlay) this.ui.hideOverlay();
+				// Remove this overlay, not the topmost one: another overlay may have opened above it.
+				if (isOverlay) overlayHandle?.hide();
 				else restoreEditor();
 				// Note: both branches above already call requestRender
 				resolve(result);
@@ -3023,9 +3025,9 @@ export class InteractiveMode {
 							const w = (component as { width?: number }).width;
 							return w ? { width: w } : undefined;
 						};
-						const handle = this.ui.showOverlay(component, resolveOptions());
+						overlayHandle = this.ui.showOverlay(component, resolveOptions());
 						// Expose handle to caller for visibility control
-						options?.onHandle?.(handle);
+						options?.onHandle?.(overlayHandle);
 					} else {
 						this.disposeActiveSelector();
 						this.editorContainer.clear();

packages/coding-agent/test/interactive-mode-status.test.ts

@@ -300,6 +300,84 @@ describe("InteractiveMode.showExtensionCustom", () => {
 			ui.stop();
 		}
 	});
+
+	// Regression test for #10648: closing a lower overlay removed the topmost overlay instead.
+	test.each([
+		{ lowerKind: "capturing", nonCapturing: false },
+		{ lowerKind: "non-capturing", nonCapturing: true },
+	])(
+		"closing a lower $lowerKind overlay custom UI removes its own overlay, not the topmost one",
+		async ({ nonCapturing }) => {
+			const terminal = new VirtualTerminal(80, 24);
+			const ui: TUI = new TuiMainScreen(terminal);
+			const editorContainer = new Container();
+			const editor = new TestFocusableComponent("EDITOR");
+			const lower = new TestFocusableComponent("LOWER");
+			const upper = new TestFocusableComponent("UPPER");
+			let closeLower: (value: string) => void = () => {
+				throw new Error("closeLower was not initialized");
+			};
+			let closeUpper: (value: string) => void = () => {
+				throw new Error("closeUpper was not initialized");
+			};
+			const fakeThis = {
+				editor,
+				editorContainer,
+				keybindings: {},
+				ui,
+				disposeActiveSelector: vi.fn(),
+			};
+			const showExtensionCustom = <T>(
+				factory: (tui: TUI, theme: unknown, keybindings: unknown, done: (result: T) => void) => Component,
+				options?: { overlay?: boolean; overlayOptions?: { nonCapturing?: boolean } },
+			): Promise<T> =>
+				(InteractiveMode as any).prototype.showExtensionCustom.call(fakeThis, factory, options) as Promise<T>;
+
+			editorContainer.addChild(editor);
+			ui.addChild(editorContainer);
+			ui.setFocus(editor);
+			ui.start();
+			try {
+				const lowerPromise = showExtensionCustom<string>(
+					(_tui, _theme, _keybindings, done) => {
+						closeLower = done;
+						return lower;
+					},
+					{ overlay: true, overlayOptions: { nonCapturing } },
+				);
+				await flushTui(ui, terminal);
+				const upperPromise = showExtensionCustom<string>(
+					(_tui, _theme, _keybindings, done) => {
+						closeUpper = done;
+						return upper;
+					},
+					{ overlay: true },
+				);
+				await flushTui(ui, terminal);
+				expect(upper.focused).toBe(true);
+
+				closeLower("lower closed");
+				await expect(lowerPromise).resolves.toBe("lower closed");
+				await flushTui(ui, terminal);
+
+				const viewport = terminal.getViewport().join("\n");
+				expect(viewport).toContain("UPPER");
+				expect(viewport).not.toContain("LOWER");
+				terminal.sendInput("x");
+				await flushTui(ui, terminal);
+				expect(upper.inputs).toEqual(["x"]);
+				expect(lower.inputs).toEqual([]);
+
+				closeUpper("upper closed");
+				await expect(upperPromise).resolves.toBe("upper closed");
+				await flushTui(ui, terminal);
+				expect(ui.hasOverlay()).toBe(false);
+				expect(editor.focused).toBe(true);
+			} finally {
+				ui.stop();
+			}
+		},
+	);
 });
 
 describe("InteractiveMode.createExtensionUIContext addAutocompleteProvider", () => {