diff --git a/packages/app/e2e/browser/split-pane-drag-tracking.spec.ts b/packages/app/e2e/browser/split-pane-drag-tracking.spec.ts
new file mode 100644
index 0000000000..02ad911765
--- /dev/null
+++ b/packages/app/e2e/browser/split-pane-drag-tracking.spec.ts
@@ -0,0 +1,60 @@
+import { expect, type Locator, type Page } from "@playwright/test";
+import { test } from "../support/fixtures";
+import { runWorkspaceActionFromCommandCenter } from "../support/helpers/command-center-workspace-actions";
+import { clickNewChat, gotoWorkspace } from "../support/helpers/launcher";
+import { seedWorkspace } from "../support/helpers/seed-client";
+import { waitForWorkspaceTabsVisible } from "../support/helpers/workspace-tabs";
+
+const DRAG_DISTANCE = -40;
+const TOLERANCE_PX = 2;
+
+function splitDividers(page: Page): Locator {
+  return page.getByTestId("workspace-split-resize-handle").filter({ visible: true });
+}
+
+async function dividerX(divider: Locator): Promise<number> {
+  const box = await divider.boundingBox();
+  if (!box) throw new Error("Divider has no bounding box");
+  return box.x;
+}
+
+async function dragDivider(divider: Locator, deltaX: number): Promise<void> {
+  const page = divider.page();
+  const box = await divider.boundingBox();
+  if (!box) throw new Error("Divider has no bounding box");
+  const x = box.x + box.width / 2;
+  const y = box.y + box.height / 2;
+  await page.mouse.move(x, y);
+  await page.mouse.down();
+  await page.mouse.move(x + deltaX, y, { steps: 8 });
+  await page.mouse.up();
+}
+
+test.describe("Split pane drag tracking", () => {
+  test("a divider moves as far as the mouse in the main row", async ({ page }) => {
+    await page.setViewportSize({ width: 1600, height: 900 });
+    const workspace = await seedWorkspace({ repoPrefix: "split-drag-tracking-" });
+    try {
+      await gotoWorkspace(page, workspace.workspaceId);
+      await waitForWorkspaceTabsVisible(page);
+      await clickNewChat(page);
+      for (const expectedDividers of [1, 2, 3]) {
+        await runWorkspaceActionFromCommandCenter(page, "Split pane right");
+        await expect(splitDividers(page)).toHaveCount(expectedDividers);
+      }
+
+      for (const index of [0, 1, 2]) {
+        const divider = splitDividers(page).nth(index);
+        const before = await dividerX(divider);
+        await dragDivider(divider, DRAG_DISTANCE);
+        await expect
+          .poll(async () => Math.abs((await dividerX(divider)) - before - DRAG_DISTANCE), {
+            message: `divider ${index + 1} should stay under the mouse`,
+          })
+          .toBeLessThanOrEqual(TOLERANCE_PX);
+      }
+    } finally {
+      await workspace.cleanup();
+    }
+  });
+});
diff --git a/packages/app/src/components/split-container.tsx b/packages/app/src/components/split-container.tsx
index 9705f3be15..b06d22438f 100644
--- a/packages/app/src/components/split-container.tsx
+++ b/packages/app/src/components/split-container.tsx
@@ -82,6 +82,7 @@ import type { WorkspaceTabDescriptor } from "@/screens/workspace/workspace-tabs-
 import {
   createDefaultLayout,
   findPaneById,
+  selectExplorerSidebarPaneId,
   useWorkspaceLayoutStore,
   type SplitNode,
   type SplitPane,
@@ -351,8 +352,8 @@ export function SplitContainer({
   } | null>(null);
   const maximizedPaneId =
     maximizedPane?.workspaceKey === workspaceKey ? maximizedPane.paneId : null;
-  const explorerSidebarPaneId = useWorkspaceLayoutStore(
-    (state) => state.explorerSidebarPaneIdByWorkspace[workspaceKey] ?? null,
+  const explorerSidebarPaneId = useWorkspaceLayoutStore((state) =>
+    selectExplorerSidebarPaneId(state, workspaceKey),
   );
 
   const sensors = useSensors(