diff --git a/src/cron/normalize.test.ts b/src/cron/normalize.test.ts
index 8b7ffe4a3e6..ec77e6a72d5 100644
--- a/src/cron/normalize.test.ts
+++ b/src/cron/normalize.test.ts
@@ -195,6 +195,42 @@ describe("normalizeCronJobCreate", () => {
     expectAnnounceDeliveryTarget(delivery, { channel: "telegram", to: "7200373102" });
   });
 
+  it("normalizes whitespace-only payload text to empty strings so validation rejects it", () => {
+    const agentTurn = normalizeCronJobCreate({
+      name: "blank agent turn",
+      enabled: true,
+      schedule: { kind: "every", everyMs: 60_000 },
+      sessionTarget: "isolated",
+      wakeMode: "now",
+      payload: {
+        kind: "agentTurn",
+        message: "   ",
+      },
+    }) as unknown as Record<string, unknown>;
+    expect(agentTurn.payload).toEqual({ kind: "agentTurn", message: "" });
+    expect(validateCronAddParams(agentTurn)).toBe(false);
+
+    const systemEvent = normalizeCronJobCreate({
+      name: "blank system event",
+      enabled: true,
+      schedule: { kind: "every", everyMs: 60_000 },
+      sessionTarget: "main",
+      wakeMode: "now",
+      payload: {
+        kind: "systemEvent",
+        text: "   ",
+      },
+    }) as unknown as Record<string, unknown>;
+    expect(systemEvent.payload).toEqual({ kind: "systemEvent", text: "" });
+    expect(validateCronAddParams(systemEvent)).toBe(false);
+
+    const update = normalizeCronJobPatch({
+      payload: { kind: "agentTurn", message: "   " },
+    }) as unknown as Record<string, unknown>;
+    expect(update.payload).toEqual({ kind: "agentTurn", message: "" });
+    expect(validateCronUpdateParams({ id: "job-1", patch: update })).toBe(false);
+  });
+
   it("normalizes delivery accountId and strips blanks", () => {
     const normalized = normalizeIsolatedAgentTurnCreateJob({
       name: "delivery account",
diff --git a/src/cron/normalize.ts b/src/cron/normalize.ts
index c68289b1974..fdfbf738004 100644
--- a/src/cron/normalize.ts
+++ b/src/cron/normalize.ts
@@ -128,12 +128,16 @@ function coercePayload(payload: UnknownRecord) {
     const trimmed = normalizeOptionalString(next.message) ?? "";
     if (trimmed) {
       next.message = trimmed;
+    } else {
+      next.message = "";
     }
   }
   if (typeof next.text === "string") {
     const trimmed = normalizeOptionalString(next.text) ?? "";
     if (trimmed) {
       next.text = trimmed;
+    } else {
+      next.text = "";
     }
   }
   if ("model" in next) {
diff --git a/src/gateway/server-methods/cron.validation.test.ts b/src/gateway/server-methods/cron.validation.test.ts
index cb70e7de6b5..c2205de4c40 100644
--- a/src/gateway/server-methods/cron.validation.test.ts
+++ b/src/gateway/server-methods/cron.validation.test.ts
@@ -404,6 +404,28 @@ describe("cron method validation", () => {
     expectResponseError(respond, { code: "INVALID_REQUEST" });
   });
 
+  it("rejects whitespace-only cron payloads before calling add", async () => {
+    const agentTurn = await invokeCronAdd(
+      agentTurnCronParams({
+        name: "blank agent turn",
+        payload: { kind: "agentTurn", message: "   " },
+      }),
+    );
+    expect(agentTurn.context.cron.add).not.toHaveBeenCalled();
+    expectResponseError(agentTurn.respond, { code: "INVALID_REQUEST", messageIncludes: "message" });
+
+    const systemEvent = await invokeCronAdd({
+      name: "blank system event",
+      enabled: true,
+      schedule: { kind: "every", everyMs: 60_000 },
+      sessionTarget: "main",
+      wakeMode: "next-heartbeat",
+      payload: { kind: "systemEvent", text: "   " },
+    });
+    expect(systemEvent.context.cron.add).not.toHaveBeenCalled();
+    expectResponseError(systemEvent.respond, { code: "INVALID_REQUEST", messageIncludes: "text" });
+  });
+
   it("rejects ambiguous announce delivery on add when multiple channels are configured", async () => {
     setRuntimeConfig(telegramSlackConfig({ includeMainSession: true }));