diff --git a/src/agents/openclaw-tools.subagents.sessions-spawn-default-timeout-absent.test.ts b/src/agents/openclaw-tools.subagents.sessions-spawn-default-timeout-absent.test.ts
new file mode 100644
index 00000000000..947c83333fd
--- /dev/null
+++ b/src/agents/openclaw-tools.subagents.sessions-spawn-default-timeout-absent.test.ts
@@ -0,0 +1,69 @@
+import { describe, expect, it, vi } from "vitest";
+import { createSessionsSpawnTool } from "./tools/sessions-spawn-tool.js";
+
+vi.mock("../config/config.js", async () => {
+  const actual = await vi.importActual("../config/config.js");
+  return {
+    ...actual,
+    loadConfig: () => ({
+      agents: {
+        defaults: {
+          subagents: {
+            maxConcurrent: 8,
+          },
+        },
+      },
+      routing: {
+        sessions: {
+          mainKey: "agent:test:main",
+        },
+      },
+    }),
+  };
+});
+
+vi.mock("../gateway/call.js", () => {
+  return {
+    callGateway: vi.fn(async ({ method }: { method: string }) => {
+      if (method === "agent") {
+        return { runId: "run-456" };
+      }
+      return {};
+    }),
+  };
+});
+
+vi.mock("../plugins/hook-runner-global.js", () => ({
+  getGlobalHookRunner: () => null,
+}));
+
+type GatewayCall = { method: string; params?: Record<string, unknown> };
+
+async function getGatewayCalls(): Promise<GatewayCall[]> {
+  const { callGateway } = await import("../gateway/call.js");
+  return (callGateway as unknown as ReturnType<typeof vi.fn>).mock.calls.map(
+    (call) => call[0] as GatewayCall,
+  );
+}
+
+function findLastCall(calls: GatewayCall[], predicate: (call: GatewayCall) => boolean) {
+  for (let i = calls.length - 1; i >= 0; i -= 1) {
+    const call = calls[i];
+    if (call && predicate(call)) {
+      return call;
+    }
+  }
+  return undefined;
+}
+
+describe("sessions_spawn default runTimeoutSeconds (config absent)", () => {
+  it("falls back to 0 (no timeout) when config key is absent", async () => {
+    const tool = createSessionsSpawnTool({ agentSessionKey: "agent:test:main" });
+    const result = await tool.execute("call-1", { task: "hello" });
+    expect(result.details).toMatchObject({ status: "accepted" });
+
+    const calls = await getGatewayCalls();
+    const agentCall = findLastCall(calls, (call) => call.method === "agent");
+    expect(agentCall?.params?.timeout).toBe(0);
+  });
+});
diff --git a/src/agents/openclaw-tools.subagents.sessions-spawn-default-timeout.test.ts b/src/agents/openclaw-tools.subagents.sessions-spawn-default-timeout.test.ts
new file mode 100644
index 00000000000..8186b8bde95
--- /dev/null
+++ b/src/agents/openclaw-tools.subagents.sessions-spawn-default-timeout.test.ts
@@ -0,0 +1,79 @@
+import { describe, expect, it, vi } from "vitest";
+import { createSessionsSpawnTool } from "./tools/sessions-spawn-tool.js";
+
+vi.mock("../config/config.js", async () => {
+  const actual = await vi.importActual("../config/config.js");
+  return {
+    ...actual,
+    loadConfig: () => ({
+      agents: {
+        defaults: {
+          subagents: {
+            runTimeoutSeconds: 900,
+          },
+        },
+      },
+      routing: {
+        sessions: {
+          mainKey: "agent:test:main",
+        },
+      },
+    }),
+  };
+});
+
+vi.mock("../gateway/call.js", () => {
+  return {
+    callGateway: vi.fn(async ({ method }: { method: string }) => {
+      if (method === "agent") {
+        return { runId: "run-123" };
+      }
+      return {};
+    }),
+  };
+});
+
+vi.mock("../plugins/hook-runner-global.js", () => ({
+  getGlobalHookRunner: () => null,
+}));
+
+type GatewayCall = { method: string; params?: Record<string, unknown> };
+
+async function getGatewayCalls(): Promise<GatewayCall[]> {
+  const { callGateway } = await import("../gateway/call.js");
+  return (callGateway as unknown as ReturnType<typeof vi.fn>).mock.calls.map(
+    (call) => call[0] as GatewayCall,
+  );
+}
+
+function findLastCall(calls: GatewayCall[], predicate: (call: GatewayCall) => boolean) {
+  for (let i = calls.length - 1; i >= 0; i -= 1) {
+    const call = calls[i];
+    if (call && predicate(call)) {
+      return call;
+    }
+  }
+  return undefined;
+}
+
+describe("sessions_spawn default runTimeoutSeconds", () => {
+  it("uses config default when agent omits runTimeoutSeconds", async () => {
+    const tool = createSessionsSpawnTool({ agentSessionKey: "agent:test:main" });
+    const result = await tool.execute("call-1", { task: "hello" });
+    expect(result.details).toMatchObject({ status: "accepted" });
+
+    const calls = await getGatewayCalls();
+    const agentCall = findLastCall(calls, (call) => call.method === "agent");
+    expect(agentCall?.params?.timeout).toBe(900);
+  });
+
+  it("explicit runTimeoutSeconds wins over config default", async () => {
+    const tool = createSessionsSpawnTool({ agentSessionKey: "agent:test:main" });
+    const result = await tool.execute("call-2", { task: "hello", runTimeoutSeconds: 300 });
+    expect(result.details).toMatchObject({ status: "accepted" });
+
+    const calls = await getGatewayCalls();
+    const agentCall = findLastCall(calls, (call) => call.method === "agent");
+    expect(agentCall?.params?.timeout).toBe(300);
+  });
+});
diff --git a/src/agents/subagent-spawn.ts b/src/agents/subagent-spawn.ts
index d033c78bc3e..7d4f672f2f1 100644
--- a/src/agents/subagent-spawn.ts
+++ b/src/agents/subagent-spawn.ts
@@ -193,14 +193,22 @@ export async function spawnSubagentDirect(
     threadId: ctx.agentThreadId,
   });
   const hookRunner = getGlobalHookRunner();
+  const cfg = loadConfig();
+
+  // When agent omits runTimeoutSeconds, use the config default.
+  // Falls back to 0 (no timeout) if config key is also unset,
+  // preserving current behavior for existing deployments.
+  const cfgSubagentTimeout =
+    typeof cfg?.agents?.defaults?.subagents?.runTimeoutSeconds === "number" &&
+    Number.isFinite(cfg.agents.defaults.subagents.runTimeoutSeconds)
+      ? Math.max(0, Math.floor(cfg.agents.defaults.subagents.runTimeoutSeconds))
+      : 0;
   const runTimeoutSeconds =
     typeof params.runTimeoutSeconds === "number" && Number.isFinite(params.runTimeoutSeconds)
       ? Math.max(0, Math.floor(params.runTimeoutSeconds))
-      : 0;
+      : cfgSubagentTimeout;
   let modelApplied = false;
   let threadBindingReady = false;
-
-  const cfg = loadConfig();
   const { mainKey, alias } = resolveMainSessionAlias(cfg);
   const requesterSessionKey = ctx.agentSessionKey;
   const requesterInternalKey = requesterSessionKey
diff --git a/src/config/types.agent-defaults.ts b/src/config/types.agent-defaults.ts
index 7ecfc6d4193..e8eac685086 100644
--- a/src/config/types.agent-defaults.ts
+++ b/src/config/types.agent-defaults.ts
@@ -247,6 +247,8 @@ export type AgentDefaultsConfig = {
     model?: AgentModelConfig;
     /** Default thinking level for spawned sub-agents (e.g. "off", "low", "medium", "high"). */
     thinking?: string;
+    /** Default run timeout in seconds for spawned sub-agents (0 = no timeout). */
+    runTimeoutSeconds?: number;
     /** Gateway timeout in ms for sub-agent announce delivery calls (default: 60000). */
     announceTimeoutMs?: number;
   };
diff --git a/src/config/zod-schema.agent-defaults.ts b/src/config/zod-schema.agent-defaults.ts
index a4fb3c2443b..6f80698f079 100644
--- a/src/config/zod-schema.agent-defaults.ts
+++ b/src/config/zod-schema.agent-defaults.ts
@@ -146,6 +146,7 @@ export const AgentDefaultsSchema = z
         archiveAfterMinutes: z.number().int().positive().optional(),
         model: AgentModelSchema.optional(),
         thinking: z.string().optional(),
+        runTimeoutSeconds: z.number().min(0).optional(),
         announceTimeoutMs: z.number().int().positive().optional(),
       })
       .strict()