diff --git a/CHANGELOG.md b/CHANGELOG.md
index cc5b1b7902a..045c069d218 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -111,6 +111,7 @@ Docs: https://docs.openclaw.ai
 - Signal/Loop protection: evaluate own-account detection before sync-message filtering (including UUID-only `accountUuid` configs) so `sentTranscript` sync events cannot bypass loop protection and self-reply loops. Landed from contributor PR #31093 by @kevinWangSheng. Thanks @kevinWangSheng.
 - Gateway/Control UI origins: support wildcard `"*"` in `gateway.controlUi.allowedOrigins` for trusted remote access setups. Landed from contributor PR #31088 by @frankekn. Thanks @frankekn.
 - Cron/Isolated CLI timeout ratio: avoid reusing persisted CLI session IDs on fresh isolated cron runs so the fresh watchdog profile is used and jobs do not abort at roughly one-third of configured `timeoutSeconds`. (#30140) Thanks @ningding97.
+- Cron/Session target guardrail: reject creating or patching `sessionTarget: "main"` cron jobs when `agentId` is not the default agent, preventing invalid cross-agent main-session bindings at write time. (#30217) Thanks @liaosvcaf.
 - Security/Sandbox media reads: eliminate sandbox media TOCTOU symlink-retarget escapes by enforcing root-scoped boundary-safe reads at attachment/image load time and consolidating shared safe-read helpers across sandbox media callsites. This ships in the next npm release. Thanks @tdjackey for reporting.
 - Node host/service auth env: include `OPENCLAW_GATEWAY_TOKEN` in `openclaw node install` service environments (with `CLAWDBOT_GATEWAY_TOKEN` compatibility fallback) so installed node services keep remote gateway token auth across restart/reboot. Fixes #31041. Thanks @OneStepAt4time for reporting, @byungsker, @liuxiaopai-ai, and @vincentkoc.
 - Security/Subagents sandbox inheritance: block sandboxed sessions from spawning cross-agent subagents that would run unsandboxed, preventing runtime sandbox downgrade via `sessions_spawn agentId`. Thanks @tdjackey for reporting.
diff --git a/src/cron/service.jobs.test.ts b/src/cron/service.jobs.test.ts
index e133197fbad..18eef9240d1 100644
--- a/src/cron/service.jobs.test.ts
+++ b/src/cron/service.jobs.test.ts
@@ -257,14 +257,105 @@ describe("applyJobPatch", () => {
   });
 });
 
-function createMockState(now: number): CronServiceState {
+function createMockState(now: number, opts?: { defaultAgentId?: string }): CronServiceState {
   return {
     deps: {
       nowMs: () => now,
+      defaultAgentId: opts?.defaultAgentId,
     },
   } as unknown as CronServiceState;
 }
 
+describe("createJob rejects sessionTarget main for non-default agents", () => {
+  const now = Date.parse("2026-02-28T12:00:00.000Z");
+
+  const mainJobInput = (agentId?: string) => ({
+    name: "my-main-job",
+    enabled: true,
+    schedule: { kind: "every" as const, everyMs: 60_000 },
+    sessionTarget: "main" as const,
+    wakeMode: "now" as const,
+    payload: { kind: "systemEvent" as const, text: "tick" },
+    ...(agentId !== undefined ? { agentId } : {}),
+  });
+
+  it("allows creating a main-session job for the default agent", () => {
+    const state = createMockState(now, { defaultAgentId: "main" });
+    expect(() => createJob(state, mainJobInput())).not.toThrow();
+    expect(() => createJob(state, mainJobInput("main"))).not.toThrow();
+  });
+
+  it("allows creating a main-session job when defaultAgentId matches (case-insensitive)", () => {
+    const state = createMockState(now, { defaultAgentId: "Main" });
+    expect(() => createJob(state, mainJobInput("MAIN"))).not.toThrow();
+  });
+
+  it("rejects creating a main-session job for a non-default agentId", () => {
+    const state = createMockState(now, { defaultAgentId: "main" });
+    expect(() => createJob(state, mainJobInput("custom-agent"))).toThrow(
+      'cron: sessionTarget "main" is only valid for the default agent',
+    );
+  });
+
+  it("rejects main-session job for non-default agent even without explicit defaultAgentId", () => {
+    const state = createMockState(now);
+    expect(() => createJob(state, mainJobInput("custom-agent"))).toThrow(
+      'cron: sessionTarget "main" is only valid for the default agent',
+    );
+  });
+
+  it("allows isolated session job for non-default agents", () => {
+    const state = createMockState(now, { defaultAgentId: "main" });
+    expect(() =>
+      createJob(state, {
+        name: "isolated-job",
+        enabled: true,
+        schedule: { kind: "every", everyMs: 60_000 },
+        sessionTarget: "isolated",
+        wakeMode: "now",
+        payload: { kind: "agentTurn", message: "do it" },
+        agentId: "custom-agent",
+      }),
+    ).not.toThrow();
+  });
+});
+
+describe("applyJobPatch rejects sessionTarget main for non-default agents", () => {
+  const now = Date.now();
+
+  const createMainJob = (agentId?: string): CronJob => ({
+    id: "job-main-agent-check",
+    name: "main-agent-check",
+    enabled: true,
+    createdAtMs: now,
+    updatedAtMs: now,
+    schedule: { kind: "every", everyMs: 60_000 },
+    sessionTarget: "main",
+    wakeMode: "now",
+    payload: { kind: "systemEvent", text: "tick" },
+    state: {},
+    agentId,
+  });
+
+  it("rejects patching agentId to non-default on a main-session job", () => {
+    const job = createMainJob();
+    expect(() =>
+      applyJobPatch(job, { agentId: "custom-agent" } as CronJobPatch, {
+        defaultAgentId: "main",
+      }),
+    ).toThrow('cron: sessionTarget "main" is only valid for the default agent');
+  });
+
+  it("allows patching agentId to the default agent on a main-session job", () => {
+    const job = createMainJob();
+    expect(() =>
+      applyJobPatch(job, { agentId: "main" } as CronJobPatch, {
+        defaultAgentId: "main",
+      }),
+    ).not.toThrow();
+  });
+});
+
 describe("cron stagger defaults", () => {
   it("defaults top-of-hour cron jobs to 5m stagger", () => {
     const now = Date.parse("2026-02-08T10:00:00.000Z");
diff --git a/src/cron/service.runs-one-shot-main-job-disables-it.test.ts b/src/cron/service.runs-one-shot-main-job-disables-it.test.ts
index 5856a007b26..bcf5b919c34 100644
--- a/src/cron/service.runs-one-shot-main-job-disables-it.test.ts
+++ b/src/cron/service.runs-one-shot-main-job-disables-it.test.ts
@@ -509,39 +509,21 @@ describe("CronService", () => {
     await store.cleanup();
   });
 
-  it("passes agentId and preserves scoped session for wakeMode now main jobs", async () => {
+  it("rejects sessionTarget main for non-default agents at creation time", async () => {
     const runHeartbeatOnce = vi.fn(async () => ({ status: "ran" as const, durationMs: 1 }));
 
-    const { store, cron, enqueueSystemEvent, requestHeartbeatNow } =
-      await createWakeModeNowMainHarness({
-        runHeartbeatOnce,
-        // Perf: avoid advancing fake timers by 2+ minutes for the busy-heartbeat fallback.
-        wakeNowHeartbeatBusyMaxWaitMs: 1,
-        wakeNowHeartbeatBusyRetryDelayMs: 2,
-      });
-
-    const sessionKey = "agent:ops:discord:channel:alerts";
-    const job = await addWakeModeNowMainSystemEventJob(cron, {
-      name: "wakeMode now with agent",
-      agentId: "ops",
-      sessionKey,
+    const { store, cron } = await createWakeModeNowMainHarness({
+      runHeartbeatOnce,
+      wakeNowHeartbeatBusyMaxWaitMs: 1,
+      wakeNowHeartbeatBusyRetryDelayMs: 2,
     });
 
-    await cron.run(job.id, "force");
-
-    expect(runHeartbeatOnce).toHaveBeenCalledTimes(1);
-    expect(runHeartbeatOnce).toHaveBeenCalledWith(
-      expect.objectContaining({
-        reason: `cron:${job.id}`,
+    await expect(
+      addWakeModeNowMainSystemEventJob(cron, {
+        name: "wakeMode now with agent",
         agentId: "ops",
-        sessionKey,
       }),
-    );
-    expect(requestHeartbeatNow).not.toHaveBeenCalled();
-    expect(enqueueSystemEvent).toHaveBeenCalledWith(
-      "hello",
-      expect.objectContaining({ agentId: "ops", sessionKey }),
-    );
+    ).rejects.toThrow('cron: sessionTarget "main" is only valid for the default agent');
 
     cron.stop();
     await store.cleanup();
diff --git a/src/cron/service/jobs.ts b/src/cron/service/jobs.ts
index 5ccca6c43d3..7bb80ef37ac 100644
--- a/src/cron/service/jobs.ts
+++ b/src/cron/service/jobs.ts
@@ -1,4 +1,5 @@
 import crypto from "node:crypto";
+import { normalizeAgentId } from "../../routing/session-key.js";
 import { parseAbsoluteTimeMs } from "../parse.js";
 import { computeNextRunAtMs } from "../schedule.js";
 import {
@@ -91,6 +92,25 @@ export function assertSupportedJobSpec(job: Pick<CronJob, "sessionTarget" | "pay
   }
 }
 
+function assertMainSessionAgentId(
+  job: Pick<CronJob, "sessionTarget" | "agentId">,
+  defaultAgentId: string | undefined,
+) {
+  if (job.sessionTarget !== "main") {
+    return;
+  }
+  if (!job.agentId) {
+    return;
+  }
+  const normalized = normalizeAgentId(job.agentId);
+  const normalizedDefault = normalizeAgentId(defaultAgentId);
+  if (normalized !== normalizedDefault) {
+    throw new Error(
+      `cron: sessionTarget "main" is only valid for the default agent. Use sessionTarget "isolated" with payload.kind "agentTurn" for non-default agents (agentId: ${job.agentId})`,
+    );
+  }
+}
+
 const TELEGRAM_TME_URL_REGEX = /^https?:\/\/t\.me\/|t\.me\//i;
 const TELEGRAM_SLASH_TOPIC_REGEX = /^-?\d+\/\d+$/;
 
@@ -426,12 +446,17 @@ export function createJob(state: CronServiceState, input: CronJobCreate): CronJo
     },
   };
   assertSupportedJobSpec(job);
+  assertMainSessionAgentId(job, state.deps.defaultAgentId);
   assertDeliverySupport(job);
   job.state.nextRunAtMs = computeJobNextRunAtMs(job, now);
   return job;
 }
 
-export function applyJobPatch(job: CronJob, patch: CronJobPatch) {
+export function applyJobPatch(
+  job: CronJob,
+  patch: CronJobPatch,
+  opts?: { defaultAgentId?: string },
+) {
   if ("name" in patch) {
     job.name = normalizeRequiredName(patch.name);
   }
@@ -501,6 +526,7 @@ export function applyJobPatch(job: CronJob, patch: CronJobPatch) {
     job.sessionKey = normalizeOptionalSessionKey((patch as { sessionKey?: unknown }).sessionKey);
   }
   assertSupportedJobSpec(job);
+  assertMainSessionAgentId(job, opts?.defaultAgentId);
   assertDeliverySupport(job);
 }
 
diff --git a/src/cron/service/ops.ts b/src/cron/service/ops.ts
index af552acaabb..2b7ebf57f75 100644
--- a/src/cron/service/ops.ts
+++ b/src/cron/service/ops.ts
@@ -270,7 +270,7 @@ export async function update(state: CronServiceState, id: string, patch: CronJob
     await ensureLoaded(state, { skipRecompute: true });
     const job = findJobOrThrow(state, id);
     const now = state.deps.nowMs();
-    applyJobPatch(job, patch);
+    applyJobPatch(job, patch, { defaultAgentId: state.deps.defaultAgentId });
     if (job.schedule.kind === "every") {
       const anchor = job.schedule.anchorMs;
       if (typeof anchor !== "number" || !Number.isFinite(anchor)) {