From 31caa5652b0d3d68660c914a85af5101c057f6a0 Mon Sep 17 00:00:00 2001
From: Jake Leventhal <jakeleventhal@me.com>
Date: Sat, 18 Jul 2026 07:18:18 -0400
Subject: [PATCH] Fix reopening existing Diff tab (#3973)

Co-authored-by: Julius Marminge <julius0216@outlook.com>
---
 apps/web/src/components/ChatView.tsx | 12 +++++++++++-
 apps/web/src/rightPanelStore.test.ts | 15 +++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/apps/web/src/components/ChatView.tsx b/apps/web/src/components/ChatView.tsx
index 69292e7e6aa3bd7fbf0c3c738443f14bbf72343a..8d39c6b69acf370a1b9c41d3da714f1c1b5fd6d0 100644
--- a/apps/web/src/components/ChatView.tsx
+++ b/apps/web/src/components/ChatView.tsx
@@ -2916,9 +2916,19 @@ function ChatViewContent(props: ChatViewProps) {
   }, [activeThreadRef, openPreview]);
   const addDiffSurface = useCallback(() => {
     if (!activeThreadRef || !isServerThread || !isGitRepo) return;
+    if (planSidebarOpen) {
+      dismissPlanSidebarForCurrentTurn();
+    }
     useRightPanelStore.getState().open(activeThreadRef, "diff");
     onDiffPanelOpen?.();
-  }, [activeThreadRef, isGitRepo, isServerThread, onDiffPanelOpen]);
+  }, [
+    activeThreadRef,
+    dismissPlanSidebarForCurrentTurn,
+    isGitRepo,
+    isServerThread,
+    onDiffPanelOpen,
+    planSidebarOpen,
+  ]);
   const addFilesSurface = useCallback(() => {
     if (!activeThreadRef || !activeProject) return;
     useRightPanelStore.getState().open(activeThreadRef, "files");
diff --git a/apps/web/src/rightPanelStore.test.ts b/apps/web/src/rightPanelStore.test.ts
index b48f6e7ebb56458908189b28dbdfe058cf5d2ff6..c7457cfd3040325cd9732b93f3d4eb54135b934d 100644
--- a/apps/web/src/rightPanelStore.test.ts
+++ b/apps/web/src/rightPanelStore.test.ts
@@ -117,6 +117,21 @@ describe("rightPanelStore", () => {
     ).toHaveLength(2);
   });
 
+  it("reopening an inactive singleton activates its existing surface", () => {
+    useRightPanelStore.getState().open(refA, "diff");
+    useRightPanelStore.getState().open(refA, "plan");
+    useRightPanelStore.getState().open(refA, "diff");
+
+    expect(selectThreadRightPanelState(useRightPanelStore.getState().byThreadKey, refA)).toEqual({
+      isOpen: true,
+      activeSurfaceId: "diff",
+      surfaces: [
+        { id: "diff", kind: "diff" },
+        { id: "plan", kind: "plan" },
+      ],
+    });
+  });
+
   it("keeps files as a singleton surface", () => {
     useRightPanelStore.getState().open(refA, "files");
     useRightPanelStore.getState().open(refA, "files");
-- 
2.54.0