diff --git a/extensions/matrix/src/matrix/monitor/index.test.ts b/extensions/matrix/src/matrix/monitor/index.test.ts
index 237bcf699b3..7cd28046365 100644
--- a/extensions/matrix/src/matrix/monitor/index.test.ts
+++ b/extensions/matrix/src/matrix/monitor/index.test.ts
@@ -71,6 +71,7 @@ vi.mock("../../runtime-api.js", () => {
       ...(extra ?? {}),
     }),
     buildSecretInputSchema: () => z.string(),
+    chunkTextForOutbound: vi.fn((text: string) => [text]),
     collectStatusIssuesFromLastError: () => [],
     createActionGate: () => () => true,
     createReplyPrefixOptions: () => ({}),