diff --git a/app/src/store/__tests__/connectivitySlice.test.ts b/app/src/store/__tests__/connectivitySlice.test.ts
index bf478bc1c..e3dcf9e6b 100644
--- a/app/src/store/__tests__/connectivitySlice.test.ts
+++ b/app/src/store/__tests__/connectivitySlice.test.ts
@@ -39,6 +39,23 @@ describe('connectivitySlice', () => {
     expect(state.lastError.backend).toBeUndefined();
   });
 
+  it('setBackend clears the stale backend error when a reconnect begins (connecting)', () => {
+    // A prior disconnect leaves an error string in state…
+    let state = connectivityReducer(
+      undefined,
+      setBackend({ value: 'disconnected', error: 'transport close' })
+    );
+    expect(state.lastError.backend).toBe('transport close');
+
+    // …and the reconnect attempt ('connecting') must fully clear it rather than
+    // leave the key present-but-undefined, so the UI does not surface a stale
+    // disconnect message during the reconnection window.
+    state = connectivityReducer(state, setBackend({ value: 'connecting' }));
+    expect(state.backend).toBe('connecting');
+    expect(state.lastError.backend).toBeUndefined();
+    expect('backend' in state.lastError).toBe(false);
+  });
+
   it('initial internet state is "offline" when navigator.onLine is false (line 33)', () => {
     // Simulate the browser reporting no network at boot time.
     const originalOnLine = Object.getOwnPropertyDescriptor(navigator, 'onLine');
diff --git a/app/src/store/connectivitySlice.ts b/app/src/store/connectivitySlice.ts
index 7389c2dde..3223c900e 100644
--- a/app/src/store/connectivitySlice.ts
+++ b/app/src/store/connectivitySlice.ts
@@ -58,7 +58,13 @@ const slice = createSlice({
     },
     setBackend(state, action: PayloadAction<{ value: BackendState; error?: string }>) {
       state.backend = action.payload.value;
-      if (action.payload.value === 'connected') {
+      if (action.payload.value === 'connected' || action.payload.value === 'connecting') {
+        // Clear the stale error on both successful connection and reconnect
+        // attempts. Previously only 'connected' deleted lastError.backend,
+        // which meant a prior disconnect error (e.g. "transport close") was
+        // left set to `undefined` — not deleted — during 'connecting'. UI
+        // components that read lastError.backend could still surface a stale
+        // message in the reconnect window even though the key appeared falsy.
         delete state.lastError.backend;
       } else {
         state.lastError.backend = action.payload.error;