diff --git a/server/src/__tests__/agent-permissions-routes.test.ts b/server/src/__tests__/agent-permissions-routes.test.ts
index 7bd79f76..e553d0ac 100644
--- a/server/src/__tests__/agent-permissions-routes.test.ts
+++ b/server/src/__tests__/agent-permissions-routes.test.ts
@@ -213,6 +213,80 @@ describe("agent permission routes", () => {
     );
   });
 
+  it("normalizes direct agent creation to disable timer heartbeats by default", async () => {
+    const app = createApp({
+      type: "board",
+      userId: "board-user",
+      source: "local_implicit",
+      isInstanceAdmin: true,
+      companyIds: [companyId],
+    });
+
+    const res = await request(app)
+      .post(`/api/companies/${companyId}/agents`)
+      .send({
+        name: "Builder",
+        role: "engineer",
+        adapterType: "process",
+        adapterConfig: {},
+        runtimeConfig: {
+          heartbeat: {
+            intervalSec: 3600,
+          },
+        },
+      });
+
+    expect(res.status).toBe(201);
+    expect(mockAgentService.create).toHaveBeenCalledWith(
+      companyId,
+      expect.objectContaining({
+        runtimeConfig: {
+          heartbeat: {
+            enabled: false,
+            intervalSec: 3600,
+          },
+        },
+      }),
+    );
+  });
+
+  it("normalizes hire requests to disable timer heartbeats by default", async () => {
+    const app = createApp({
+      type: "board",
+      userId: "board-user",
+      source: "local_implicit",
+      isInstanceAdmin: true,
+      companyIds: [companyId],
+    });
+
+    const res = await request(app)
+      .post(`/api/companies/${companyId}/agent-hires`)
+      .send({
+        name: "Builder",
+        role: "engineer",
+        adapterType: "process",
+        adapterConfig: {},
+        runtimeConfig: {
+          heartbeat: {
+            intervalSec: 3600,
+          },
+        },
+      });
+
+    expect(res.status).toBe(201);
+    expect(mockAgentService.create).toHaveBeenCalledWith(
+      companyId,
+      expect.objectContaining({
+        runtimeConfig: {
+          heartbeat: {
+            enabled: false,
+            intervalSec: 3600,
+          },
+        },
+      }),
+    );
+  });
+
   it("exposes explicit task assignment access on agent detail", async () => {
     mockAccessService.listPrincipalGrants.mockResolvedValue([
       {
diff --git a/server/src/routes/agents.ts b/server/src/routes/agents.ts
index f1c15b8d..266803ec 100644
--- a/server/src/routes/agents.ts
+++ b/server/src/routes/agents.ts
@@ -449,11 +449,25 @@ export function agentRoutes(db: Db) {
   function parseSchedulerHeartbeatPolicy(runtimeConfig: unknown) {
     const heartbeat = asRecord(asRecord(runtimeConfig)?.heartbeat) ?? {};
     return {
-      enabled: parseBooleanLike(heartbeat.enabled) ?? true,
+      enabled: parseBooleanLike(heartbeat.enabled) ?? false,
       intervalSec: Math.max(0, parseNumberLike(heartbeat.intervalSec) ?? 0),
     };
   }
 
+  function normalizeNewAgentRuntimeConfig(runtimeConfig: unknown): Record<string, unknown> {
+    const parsedRuntimeConfig = asRecord(runtimeConfig);
+    const normalizedRuntimeConfig = parsedRuntimeConfig ? { ...parsedRuntimeConfig } : {};
+    const parsedHeartbeat = asRecord(normalizedRuntimeConfig.heartbeat);
+    const heartbeat = parsedHeartbeat ? { ...parsedHeartbeat } : {};
+
+    if (parseBooleanLike(heartbeat.enabled) == null) {
+      heartbeat.enabled = false;
+    }
+
+    normalizedRuntimeConfig.heartbeat = heartbeat;
+    return normalizedRuntimeConfig;
+  }
+
   function generateEd25519PrivateKeyPem(): string {
     const { privateKey } = generateKeyPairSync("ed25519");
     return privateKey.export({ type: "pkcs8", format: "pem" }).toString();
@@ -1308,6 +1322,7 @@ export function agentRoutes(db: Db) {
     const normalizedHireInput = {
       ...hireInput,
       adapterConfig: normalizedAdapterConfig,
+      runtimeConfig: normalizeNewAgentRuntimeConfig(hireInput.runtimeConfig),
     };
 
     const company = await db
@@ -1474,6 +1489,7 @@ export function agentRoutes(db: Db) {
     const createdAgent = await svc.create(companyId, {
       ...createInput,
       adapterConfig: normalizedAdapterConfig,
+      runtimeConfig: normalizeNewAgentRuntimeConfig(createInput.runtimeConfig),
       status: "idle",
       spentMonthlyCents: 0,
       lastHeartbeatAt: null,
diff --git a/server/src/services/heartbeat.ts b/server/src/services/heartbeat.ts
index 2eda0ef5..32dc4913 100644
--- a/server/src/services/heartbeat.ts
+++ b/server/src/services/heartbeat.ts
@@ -2159,7 +2159,7 @@ export function heartbeatService(db: Db) {
     const heartbeat = parseObject(runtimeConfig.heartbeat);
 
     return {
-      enabled: asBoolean(heartbeat.enabled, true),
+      enabled: asBoolean(heartbeat.enabled, false),
       intervalSec: Math.max(0, asNumber(heartbeat.intervalSec, 0)),
       wakeOnDemand: asBoolean(heartbeat.wakeOnDemand ?? heartbeat.wakeOnAssignment ?? heartbeat.wakeOnOnDemand ?? heartbeat.wakeOnAutomation, true),
       maxConcurrentRuns: normalizeMaxConcurrentRuns(heartbeat.maxConcurrentRuns),
diff --git a/ui/src/components/AgentConfigForm.tsx b/ui/src/components/AgentConfigForm.tsx
index 314ae719..dd74c376 100644
--- a/ui/src/components/AgentConfigForm.tsx
+++ b/ui/src/components/AgentConfigForm.tsx
@@ -923,14 +923,14 @@ export function AgentConfigForm(props: AgentConfigFormProps) {
               <ToggleWithNumber
                 label="Heartbeat on interval"
                 hint={help.heartbeatInterval}
-                checked={eff("heartbeat", "enabled", heartbeat.enabled !== false)}
+                checked={eff("heartbeat", "enabled", heartbeat.enabled === true)}
                 onCheckedChange={(v) => mark("heartbeat", "enabled", v)}
                 number={eff("heartbeat", "intervalSec", Number(heartbeat.intervalSec ?? 300))}
                 onNumberChange={(v) => mark("heartbeat", "intervalSec", v)}
                 numberLabel="sec"
                 numberPrefix="Run heartbeat every"
                 numberHint={help.intervalSec}
-                showNumber={eff("heartbeat", "enabled", heartbeat.enabled !== false)}
+                showNumber={eff("heartbeat", "enabled", heartbeat.enabled === true)}
               />
             </div>
             <CollapsibleSection
diff --git a/ui/src/components/OnboardingWizard.tsx b/ui/src/components/OnboardingWizard.tsx
index 8638d4d3..37509fee 100644
--- a/ui/src/components/OnboardingWizard.tsx
+++ b/ui/src/components/OnboardingWizard.tsx
@@ -33,6 +33,7 @@ import {
   buildOnboardingProjectPayload,
   selectDefaultCompanyGoalId
 } from "../lib/onboarding-launch";
+import { buildNewAgentRuntimeConfig } from "../lib/new-agent-runtime-config";
 import {
   DEFAULT_CODEX_LOCAL_BYPASS_APPROVALS_AND_SANDBOX,
   DEFAULT_CODEX_LOCAL_MODEL
@@ -460,15 +461,7 @@ export function OnboardingWizard() {
         role: "ceo",
         adapterType,
         adapterConfig: buildAdapterConfig(),
-        runtimeConfig: {
-          heartbeat: {
-            enabled: true,
-            intervalSec: 3600,
-            wakeOnDemand: true,
-            cooldownSec: 10,
-            maxConcurrentRuns: 1
-          }
-        }
+        runtimeConfig: buildNewAgentRuntimeConfig()
       });
       setCreatedAgentId(agent.id);
       queryClient.invalidateQueries({
diff --git a/ui/src/lib/new-agent-runtime-config.test.ts b/ui/src/lib/new-agent-runtime-config.test.ts
new file mode 100644
index 00000000..d4526471
--- /dev/null
+++ b/ui/src/lib/new-agent-runtime-config.test.ts
@@ -0,0 +1,34 @@
+// @vitest-environment node
+import { describe, expect, it } from "vitest";
+import { buildNewAgentRuntimeConfig } from "./new-agent-runtime-config";
+
+describe("buildNewAgentRuntimeConfig", () => {
+  it("defaults new agents to no timer heartbeat", () => {
+    expect(buildNewAgentRuntimeConfig()).toEqual({
+      heartbeat: {
+        enabled: false,
+        intervalSec: 300,
+        wakeOnDemand: true,
+        cooldownSec: 10,
+        maxConcurrentRuns: 1,
+      },
+    });
+  });
+
+  it("preserves explicit heartbeat settings", () => {
+    expect(
+      buildNewAgentRuntimeConfig({
+        heartbeatEnabled: true,
+        intervalSec: 3600,
+      }),
+    ).toEqual({
+      heartbeat: {
+        enabled: true,
+        intervalSec: 3600,
+        wakeOnDemand: true,
+        cooldownSec: 10,
+        maxConcurrentRuns: 1,
+      },
+    });
+  });
+});
diff --git a/ui/src/lib/new-agent-runtime-config.ts b/ui/src/lib/new-agent-runtime-config.ts
new file mode 100644
index 00000000..2de094b3
--- /dev/null
+++ b/ui/src/lib/new-agent-runtime-config.ts
@@ -0,0 +1,16 @@
+import { defaultCreateValues } from "../components/agent-config-defaults";
+
+export function buildNewAgentRuntimeConfig(input?: {
+  heartbeatEnabled?: boolean;
+  intervalSec?: number;
+}) {
+  return {
+    heartbeat: {
+      enabled: input?.heartbeatEnabled ?? defaultCreateValues.heartbeatEnabled,
+      intervalSec: input?.intervalSec ?? defaultCreateValues.intervalSec,
+      wakeOnDemand: true,
+      cooldownSec: 10,
+      maxConcurrentRuns: 1,
+    },
+  };
+}
diff --git a/ui/src/pages/NewAgent.tsx b/ui/src/pages/NewAgent.tsx
index 9b1dd12c..498f8fad 100644
--- a/ui/src/pages/NewAgent.tsx
+++ b/ui/src/pages/NewAgent.tsx
@@ -23,6 +23,7 @@ import { getUIAdapter, listUIAdapters } from "../adapters";
 import { useDisabledAdaptersSync } from "../adapters/use-disabled-adapters";
 import { isValidAdapterType } from "../adapters/metadata";
 import { ReportsToPicker } from "../components/ReportsToPicker";
+import { buildNewAgentRuntimeConfig } from "../lib/new-agent-runtime-config";
 import {
   DEFAULT_CODEX_LOCAL_BYPASS_APPROVALS_AND_SANDBOX,
   DEFAULT_CODEX_LOCAL_MODEL,
@@ -175,15 +176,10 @@ export function NewAgent() {
       ...(selectedSkillKeys.length > 0 ? { desiredSkills: selectedSkillKeys } : {}),
       adapterType: configValues.adapterType,
       adapterConfig: buildAdapterConfig(),
-      runtimeConfig: {
-        heartbeat: {
-          enabled: configValues.heartbeatEnabled,
-          intervalSec: configValues.intervalSec,
-          wakeOnDemand: true,
-          cooldownSec: 10,
-          maxConcurrentRuns: 1,
-        },
-      },
+      runtimeConfig: buildNewAgentRuntimeConfig({
+        heartbeatEnabled: configValues.heartbeatEnabled,
+        intervalSec: configValues.intervalSec,
+      }),
       budgetMonthlyCents: 0,
     });
   }