diff --git a/extensions/anthropic-vertex/region.adc.test.ts b/extensions/anthropic-vertex/region.adc.test.ts
index 5313a266ced..605820c9fce 100644
--- a/extensions/anthropic-vertex/region.adc.test.ts
+++ b/extensions/anthropic-vertex/region.adc.test.ts
@@ -38,6 +38,9 @@ describe("anthropic-vertex ADC reads", () => {
       GOOGLE_APPLICATION_CREDENTIALS: "/tmp/vertex-adc.json",
     } as NodeJS.ProcessEnv;
 
+    existsSyncMock.mockClear();
+    readFileSyncMock.mockClear();
+
     expect(resolveAnthropicVertexProjectId(env)).toBe("vertex-project");
     expect(hasAnthropicVertexAvailableAuth(env)).toBe(true);
     expect(existsSyncMock).not.toHaveBeenCalled();
diff --git a/src/plugin-sdk/anthropic-vertex-auth-presence.preflight.test.ts b/src/plugin-sdk/anthropic-vertex-auth-presence.preflight.test.ts
index 1d175765695..cc79c2b712e 100644
--- a/src/plugin-sdk/anthropic-vertex-auth-presence.preflight.test.ts
+++ b/src/plugin-sdk/anthropic-vertex-auth-presence.preflight.test.ts
@@ -34,6 +34,9 @@ describe("hasAnthropicVertexAvailableAuth ADC preflight", () => {
   });
 
   it("reads explicit ADC credentials without an existsSync preflight", () => {
+    existsSyncMock.mockClear();
+    readFileSyncMock.mockClear();
+
     expect(
       hasAnthropicVertexAvailableAuth({
         GOOGLE_APPLICATION_CREDENTIALS: "/tmp/vertex-adc.json",