fix: keep agent tab before PR tab (#1360)

apps/web/components/task/dockview-session-tabs.test.ts

@@ -2,6 +2,7 @@ import { describe, it, expect, vi } from "vitest";
 import type { DockviewApi } from "dockview-react";
 import type { TaskSession } from "@/lib/types/http";
 import {
+  ensureSessionTabPrecedesNonSessionTabs,
   findSessionAnchorGroupId,
   reconcileRemovedSessionPanels,
   resolveInitialPosition,
@@ -16,10 +17,25 @@ type FakePanel = {
   api: { close: ReturnType<typeof vi.fn<[], void>> };
 };
 
+type MoveToOptions = {
+  group: unknown;
+  position: "center";
+  index: number;
+  skipSetActive: boolean;
+};
+
+type MoveToCall = {
+  panelId: string;
+  options: MoveToOptions;
+};
+
 const KEEP = "keep";
 const KEEP_PANEL = `session:${KEEP}`;
 const LEAKED_PANEL = "session:leaked";
 const PENDING_SESSION_ID = "session-new";
+const TEST_GROUP_CENTER = "group-center";
+const CENTER_POSITION = "center";
+const SIBLING_PANEL = "session:sibling";
 
 /**
  * Builds a fake DockviewApi where `panel.api.close()` mutates the underlying
@@ -68,6 +84,42 @@ function panelById(panels: FakePanel[], id: string): FakePanel | undefined {
   return panels.find((p) => p.id === id);
 }
 
+function makeTabOrderApi(panelIds: string[]): {
+  api: DockviewApi;
+  moveToCalls: MoveToCall[];
+} {
+  const moveToCalls: MoveToCall[] = [];
+  const group = { id: TEST_GROUP_CENTER, panels: [] as Array<{ id: string }> };
+  const panels = panelIds.map((id) => ({
+    id,
+    group,
+    api: {
+      moveTo: vi.fn((options: MoveToOptions) => {
+        moveToCalls.push({ panelId: id, options });
+      }),
+    },
+  }));
+  group.panels = panels;
+  return {
+    api: {
+      getPanel: (id: string) => panels.find((p) => p.id === id) ?? null,
+    } as unknown as DockviewApi,
+    moveToCalls,
+  };
+}
+
+function expectedMove(panelId: string, index: number): MoveToCall {
+  return {
+    panelId,
+    options: {
+      group: expect.objectContaining({ id: TEST_GROUP_CENTER }),
+      position: CENTER_POSITION,
+      index,
+      skipSetActive: true,
+    },
+  };
+}
+
 describe("reconcileRemovedSessionPanels", () => {
   it("closes a stale tracked panel that's still live in dockview", () => {
     // createdSet has session-A; A's panel is live; A is no longer in the task's
@@ -225,6 +277,56 @@ describe("resolveInitialPosition", () => {
   });
 });
 
+describe("ensureSessionTabPrecedesNonSessionTabs", () => {
+  it("moves a restored session tab before a PR tab that was saved first", () => {
+    const { api, moveToCalls } = makeTabOrderApi(["pr-detail", KEEP_PANEL, "preview:file-diff"]);
+
+    ensureSessionTabPrecedesNonSessionTabs(api, KEEP);
+
+    expect(moveToCalls).toEqual([expectedMove(KEEP_PANEL, 0)]);
+  });
+
+  it("moves interleaved session tabs as a stable block before non-session tabs", () => {
+    const { api, moveToCalls } = makeTabOrderApi(["pr-detail", SIBLING_PANEL, KEEP_PANEL]);
+
+    ensureSessionTabPrecedesNonSessionTabs(api, KEEP);
+
+    expect(moveToCalls).toEqual([expectedMove(KEEP_PANEL, 0), expectedMove(SIBLING_PANEL, 0)]);
+  });
+
+  it("does not move when session tabs already precede non-session tabs", () => {
+    const { api, moveToCalls } = makeTabOrderApi([KEEP_PANEL, SIBLING_PANEL, "pr-detail"]);
+
+    ensureSessionTabPrecedesNonSessionTabs(api, KEEP);
+
+    expect(moveToCalls).toEqual([]);
+  });
+
+  it("does not move when the session tab already precedes non-session tabs", () => {
+    const { api, moveToCalls } = makeTabOrderApi([KEEP_PANEL, "pr-detail"]);
+
+    ensureSessionTabPrecedesNonSessionTabs(api, KEEP);
+
+    expect(moveToCalls).toEqual([]);
+  });
+
+  it("keeps earlier session tabs ahead of the active session tab", () => {
+    const { api, moveToCalls } = makeTabOrderApi(["session:older", "pr-detail", KEEP_PANEL]);
+
+    ensureSessionTabPrecedesNonSessionTabs(api, KEEP);
+
+    expect(moveToCalls).toEqual([expectedMove(KEEP_PANEL, 1)]);
+  });
+
+  it("does not move when the target session panel is absent", () => {
+    const { api, moveToCalls } = makeTabOrderApi(["pr-detail", SIBLING_PANEL]);
+
+    ensureSessionTabPrecedesNonSessionTabs(api, KEEP);
+
+    expect(moveToCalls).toEqual([]);
+  });
+});
+
 describe("shouldRebuildDefaultForPendingSession", () => {
   it("does not rebuild when there is no effective session id", () => {
     const api = makePositionApi({

apps/web/components/task/dockview-session-tabs.ts

@@ -442,6 +442,36 @@ function removeChatPlaceholder(api: DockviewApi): void {
   if (chatPanel) api.removePanel(chatPanel);
 }
 
+/**
+ * Keep agent/session tabs before contextual siblings in their tab group.
+ *
+ * Dockview restores saved tab order verbatim. If a task previously saved
+ * `pr-detail` before `session:<id>`, the restored agent panel already exists,
+ * so `resolveInitialPosition(... index: 0)` never runs. Move session siblings
+ * as a stable block so multi-session ordering remains stable.
+ */
+export function ensureSessionTabPrecedesNonSessionTabs(api: DockviewApi, sessionId: string): void {
+  const panel = api.getPanel(`session:${sessionId}`);
+  const groupPanels = panel?.group?.panels;
+  if (!panel || !groupPanels) return;
+
+  const firstNonSessionIndex = groupPanels.findIndex((p) => !p.id.startsWith("session:"));
+  if (firstNonSessionIndex === -1) return;
+
+  const sessionPanelsToMove = groupPanels
+    .slice(firstNonSessionIndex + 1)
+    .filter((groupPanel) => groupPanel.id.startsWith("session:"));
+
+  for (const sessionPanel of sessionPanelsToMove.reverse()) {
+    sessionPanel.api.moveTo({
+      group: panel.group,
+      position: "center",
+      index: firstNonSessionIndex,
+      skipSetActive: true,
+    });
+  }
+}
+
 /**
  * Decide whether to force-activate the session panel after it (and any
  * sibling tabs) have been ensured.
@@ -690,6 +720,7 @@ function runAutoSessionTabEffect(
   // "chat" placeholder. Order matters: removing chat first would empty and
   // destroy the center group, collapsing the horizontal layout.
   removeChatPlaceholder(api);
+  ensureSessionTabPrecedesNonSessionTabs(api, effectiveSessionId);
 
   const activePanel = activateSessionPanel(
     api,