diff --git a/extensions/feishu/src/client.test.ts b/extensions/feishu/src/client.test.ts
index 8a4ba4f2ebf0..2f3202d531f1 100644
--- a/extensions/feishu/src/client.test.ts
+++ b/extensions/feishu/src/client.test.ts
@@ -386,6 +386,31 @@ describe("createFeishuClient HTTP timeout", () => {
       timeout: 45_000,
     });
   });
+
+  it("evicts client cache when SDK is replaced via setFeishuClientRuntimeForTest (#83911)", () => {
+    const ctorCountA = clientCtorMock.mock.calls.length;
+
+    // First client gets cached
+    createFeishuClient({ appId: "app_7", appSecret: "secret_7", accountId: "cache-clear-test" }); // pragma: allowlist secret
+    expect(clientCtorMock.mock.calls.length).toBe(ctorCountA + 1);
+
+    // SDK swap via setFeishuClientRuntimeForTest should clear the cache
+    setFeishuClientRuntimeForTest({
+      sdk: {
+        AppType: { SelfBuild: "self" } as never,
+        Client: clientCtorMock as never,
+        Domain: { Feishu: "https://open.feishu.cn", Lark: "https://open.larksuite.com" } as never,
+        LoggerLevel: { info: "info" } as never,
+        WSClient: vi.fn() as never,
+        EventDispatcher: vi.fn() as never,
+        defaultHttpInstance: mockBaseHttpInstance as never,
+      },
+    });
+
+    // Same credentials — would hit cache before the fix; now evicted
+    createFeishuClient({ appId: "app_7", appSecret: "secret_7", accountId: "cache-clear-test" }); // pragma: allowlist secret
+    expect(clientCtorMock.mock.calls.length).toBe(ctorCountA + 2);
+  });
 });
 
 describe("createFeishuWSClient proxy handling", () => {
diff --git a/extensions/feishu/src/client.ts b/extensions/feishu/src/client.ts
index 22b091920c2c..194d68e075d7 100644
--- a/extensions/feishu/src/client.ts
+++ b/extensions/feishu/src/client.ts
@@ -260,4 +260,5 @@ export function setFeishuClientRuntimeForTest(overrides?: {
   feishuClientSdk = overrides?.sdk
     ? { ...defaultFeishuClientSdk, ...overrides.sdk }
     : defaultFeishuClientSdk;
+  clearClientCache();
 }