diff --git a/ui/src/ui/app-tool-stream.node.test.ts b/ui/src/ui/app-tool-stream.node.test.ts
index 77350298e17..05ff73873e1 100644
--- a/ui/src/ui/app-tool-stream.node.test.ts
+++ b/ui/src/ui/app-tool-stream.node.test.ts
@@ -2,7 +2,7 @@ import { beforeAll, describe, expect, it, vi } from "vitest";
 import { handleAgentEvent, type FallbackStatus, type ToolStreamEntry } from "./app-tool-stream.ts";
 
 type ToolStreamHost = Parameters<typeof handleAgentEvent>[0];
-type AgentEvent = Parameters<typeof handleAgentEvent>[1];
+type AgentEvent = NonNullable<Parameters<typeof handleAgentEvent>[1]>;
 type MutableHost = ToolStreamHost & {
   compactionStatus?: unknown;
   compactionClearTimer?: number | null;