diff --git a/apps/web/src/stores/connection-store.ts b/apps/web/src/stores/connection-store.ts
index cb9159e9..3dff6e46 100644
--- a/apps/web/src/stores/connection-store.ts
+++ b/apps/web/src/stores/connection-store.ts
@@ -51,6 +51,10 @@ export const useConnectionStore = create<ConnectionState>((set, get) => ({
         } else {
           set({ lastHealthCheck: Date.now() });
         }
+      } else {
+        if (get().status === "connected") {
+          get().setDisconnected();
+        }
       }
     } catch {
       if (get().status === "connected") {
diff --git a/tests/unit/web/connection-store.test.ts b/tests/unit/web/connection-store.test.ts
index 601d435a..4527e894 100644
--- a/tests/unit/web/connection-store.test.ts
+++ b/tests/unit/web/connection-store.test.ts
@@ -81,6 +81,24 @@ describe("connection-store", () => {
     expect(fetchMock).toHaveBeenCalledTimes(1);
   });
 
+  it("checkHealth transitions connected → disconnected on fetch failure", async () => {
+    fetchMock.mockImplementation(failHealth);
+    expect(useConnectionStore.getState().status).toBe("connected");
+    await useConnectionStore.getState().checkHealth();
+    expect(useConnectionStore.getState().status).toBe("disconnected");
+    expect(useConnectionStore.getState().failedSince).toBeTypeOf("number");
+  });
+
+  it("checkHealth transitions offline → reconnected on success", async () => {
+    fetchMock.mockImplementation(okHealth);
+    useConnectionStore.getState().setOffline();
+    expect(useConnectionStore.getState().status).toBe("offline");
+    await useConnectionStore.getState().checkHealth();
+    expect(useConnectionStore.getState().status).toBe("reconnected");
+    expect(useConnectionStore.getState().failedSince).toBeNull();
+    expect(useConnectionStore.getState().lastHealthCheck).toBeTypeOf("number");
+  });
+
   it("startPolling is idempotent", () => {
     useConnectionStore.getState().setDisconnected();
     useConnectionStore.getState().startPolling();