diff --git a/src/plugin-sdk/test-helpers/plugin-runtime-mock.test.ts b/src/plugin-sdk/test-helpers/plugin-runtime-mock.test.ts
new file mode 100644
index 00000000000..720015c7f89
--- /dev/null
+++ b/src/plugin-sdk/test-helpers/plugin-runtime-mock.test.ts
@@ -0,0 +1,16 @@
+import { createPluginRuntimeMock } from "openclaw/plugin-sdk/channel-test-helpers";
+import { describe, expect, it, vi } from "vitest";
+
+describe("createPluginRuntimeMock", () => {
+  it("keeps the inbound debouncer mock aligned with the runtime contract", () => {
+    const runtime = createPluginRuntimeMock();
+    const debouncer = runtime.channel.debounce.createInboundDebouncer({
+      debounceMs: 0,
+      buildKey: () => "key",
+      onFlush: vi.fn(),
+    });
+
+    expect(debouncer.cancelKey("key")).toBe(false);
+    expect(vi.isMockFunction(debouncer.cancelKey)).toBe(true);
+  });
+});
diff --git a/src/plugin-sdk/test-helpers/plugin-runtime-mock.ts b/src/plugin-sdk/test-helpers/plugin-runtime-mock.ts
index e300e1a4148..5d51449ed87 100644
--- a/src/plugin-sdk/test-helpers/plugin-runtime-mock.ts
+++ b/src/plugin-sdk/test-helpers/plugin-runtime-mock.ts
@@ -605,6 +605,7 @@ export function createPluginRuntimeMock(overrides: DeepPartial<PluginRuntime> =
               await params.onFlush([item]);
             },
             flushKey: vi.fn(),
+            cancelKey: vi.fn(() => false),
           }),
         ) as unknown as PluginRuntime["channel"]["debounce"]["createInboundDebouncer"],
         resolveInboundDebounceMs: vi.fn((params: unknown) => {