diff --git a/src/agents/pi-embedded-runner/run/attempt.spawn-workspace.test-support.ts b/src/agents/pi-embedded-runner/run/attempt.spawn-workspace.test-support.ts
index f9dc87c0e15..c9d4d6e0cb7 100644
--- a/src/agents/pi-embedded-runner/run/attempt.spawn-workspace.test-support.ts
+++ b/src/agents/pi-embedded-runner/run/attempt.spawn-workspace.test-support.ts
@@ -350,6 +350,7 @@ vi.mock("../../pi-settings.js", () => ({
     },
   }),
   isSilentOverflowProneModel: () => false,
+  resolveEffectiveCompactionMode: () => "default",
 }));
 
 vi.mock("../extensions.js", () => ({