diff --git a/server/src/__tests__/built-in-agents.test.ts b/server/src/__tests__/built-in-agents.test.ts
index 51325c7899..3e6a475d04 100644
--- a/server/src/__tests__/built-in-agents.test.ts
+++ b/server/src/__tests__/built-in-agents.test.ts
@@ -161,9 +161,9 @@ describeEmbeddedPostgres("built-in agents", () => {
     const summarizer = definitions.find((definition) => definition.key === "summarizer");
     expect(summarizer).toMatchObject({
       defaultAdapterType: "claude_local",
-      defaultAdapterConfig: { model: "claude-haiku-4-5" },
+      defaultAdapterConfig: { model: "claude-haiku-4-5", engine: "cli" },
+      defaultRuntimeConfig: { heartbeat: { maxConcurrentRuns: 1 } },
     });
-    expect(summarizer?.defaultRuntimeConfig).toBeUndefined();
     expect(() => validateBuiltInAgentDefinitions([
       {
         key: "briefs",
diff --git a/server/src/services/built-in-agents.ts b/server/src/services/built-in-agents.ts
index 5a6bd015da..849ddcf61c 100644
--- a/server/src/services/built-in-agents.ts
+++ b/server/src/services/built-in-agents.ts
@@ -415,6 +415,10 @@ const DEFINITIONS = validateBuiltInAgentDefinitions([
     defaultAdapterType: "claude_local",
     defaultAdapterConfig: {
       model: "claude-haiku-4-5",
+      engine: "cli",
+    },
+    defaultRuntimeConfig: {
+      heartbeat: { maxConcurrentRuns: 1 },
     },
     defaultBudgetMonthlyCents: 0,
     bundle: {