fix(ui): give running tasks priority in the background-tasks rail (#113928)

ui/src/pages/chat/background-tasks.e2e.test.ts

@@ -160,6 +160,12 @@ describeControlUiE2e("Control UI chat background-tasks rail mocked Gateway E2E",
       const rail = page.locator(".chat-tasks-rail");
       await rail.locator('[data-task-id="task-subagent"]').waitFor({ state: "visible" });
       await rail.locator('[data-task-id="task-cron"]').waitFor({ state: "visible" });
+      // Finished history starts collapsed: only the section header with the
+      // count renders until it is expanded.
+      const finishedToggle = rail.getByRole("button", { name: "Finished (1)" });
+      await finishedToggle.waitFor({ state: "visible" });
+      expect(await rail.locator('[data-task-id="task-cli"]').count()).toBe(0);
+      await finishedToggle.click();
       await rail.locator('[data-task-id="task-cli"]').waitFor({ state: "visible" });
       const railText = await rail.textContent();
       expect(railText).toContain("Reading provider catalogs");

ui/src/pages/chat/components/chat-background-tasks.test.ts

@@ -87,6 +87,7 @@ describe("background tasks rail state", () => {
 
     const props = createBackgroundTasksProps(host, openSession);
     expect(props.collapsed).toBe(true);
+    expect(props.finishedCollapsed).toBe(true);
     expect(request).toHaveBeenCalledTimes(2);
     expect(props.tasks?.map((task) => task.id)).toEqual(["task-1"]);
   });
@@ -201,9 +202,10 @@ describe("background tasks rail state", () => {
       );
     };
     host.requestUpdate = renderRail;
+    // finishedCollapsed defaults to true; back-navigation from a finished
+    // detail must expand the section so the returned-to row stays visible.
     const initialProps = createBackgroundTasksProps(host, openSession);
     initialProps.onToggleCollapsed();
-    initialProps.onToggleFinished();
     renderRail();
 
     const disclosure = container.querySelector<HTMLButtonElement>(

ui/src/pages/chat/components/chat-background-tasks.ts

@@ -82,7 +82,9 @@ function getBackgroundTasksState(host: BackgroundTasksHost): BackgroundTasksStat
     // agent switches and only reload the task list for the new scope.
     collapsed: current?.collapsed ?? true,
     error: null,
-    finishedCollapsed: current?.finishedCollapsed ?? false,
+    // Finished history starts collapsed so active work owns the rail; the
+    // section header still shows the count for discoverability.
+    finishedCollapsed: current?.finishedCollapsed ?? true,
     loadedClient: null,
     loading: false,
     pendingReload: false,
@@ -588,7 +590,7 @@ export function renderBackgroundTasksRail(
             ${empty
               ? html`<div class="chat-tasks-rail__state">${t("chat.backgroundTasks.empty")}</div>`
               : nothing}
-            <div class="chat-tasks-rail__scroll">
+            <div class="chat-tasks-rail__scroll chat-tasks-rail__scroll--split">
               ${active.length > 0
                 ? html`
                     <section class="chat-tasks-rail__section" data-tasks-section="running">

ui/src/styles/chat/sidebar.css

@@ -39,13 +39,13 @@
    rules sit after the collapse/dock modifiers so the extra column wins at
    equal specificity. */
 .chat-workbench--tasks-open {
-  grid-template-columns: minmax(0, 1fr) minmax(230px, 280px);
+  grid-template-columns: minmax(0, 1fr) minmax(270px, 330px);
 }
 
 .chat-workbench--tasks-open:not(.chat-workbench--workspace-collapsed):not(
   .chat-workbench--dock-bottom
 ) {
-  grid-template-columns: minmax(0, 1fr) minmax(230px, 280px) minmax(230px, 280px);
+  grid-template-columns: minmax(0, 1fr) minmax(230px, 280px) minmax(270px, 330px);
 }
 
 /* Compact icon button shared by the pane header actions. Sizing only — chrome
@@ -873,6 +873,13 @@ openclaw-chat-sidebar-region,
   overflow: auto;
 }
 
+/* List mode splits scrolling per section: running work owns the rail and the
+   finished history pins to the bottom, so a long history can never clip the
+   active tasks (each section scrolls on its own instead of the container). */
+.chat-tasks-rail__scroll--split {
+  overflow: hidden;
+}
+
 .chat-tasks-rail__section {
   display: flex;
   flex: 0 1 auto;
@@ -882,6 +889,16 @@ openclaw-chat-sidebar-region,
   padding-top: 8px;
 }
 
+.chat-tasks-rail__scroll--split > [data-tasks-section="running"] {
+  flex: 1 1 auto;
+}
+
+/* Cap only when running work is present; alone, finished may fill the rail. */
+.chat-tasks-rail__scroll--split > [data-tasks-section="running"] + [data-tasks-section="finished"] {
+  max-height: 50%;
+  border-top: 1px solid color-mix(in srgb, var(--border) 42%, transparent);
+}
+
 .chat-tasks-rail__section-title {
   color: var(--muted);
   font-size: var(--control-ui-text-xs);
@@ -1836,6 +1853,10 @@ openclaw-session-discussion {
   flex: 1 0 260px;
   min-width: 0;
   overflow-y: auto;
+  /* Undo the vertical split's bottom-pin cap: strip sections are full-height
+     columns and separate with border-left instead. */
+  max-height: none;
+  border-top: none;
 }
 
 .chat-workbench--tasks-dock-bottom