diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0e69f825c8..e08f1c463a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@ Docs: https://docs.openclaw.ai
 
 ### Fixes
 
+- Cron/Heartbeat: canonicalize session-scoped reminder `sessionKey` routing and preserve explicit flat `sessionKey` cron tool inputs, preventing enqueue/wake namespace drift for session-targeted reminders. (#18637) Thanks @vignesh07.
 - OpenClawKit/iOS ChatUI: accept canonical session-key completion events for local pending runs and preserve message IDs across history refreshes, preventing stuck "thinking" state and message flicker after gateway replies. (#18165) Thanks @mbelinky.
 - iOS/Onboarding: add QR-first onboarding wizard with setup-code deep link support, pairing/auth issue guidance, and device-pair QR generation improvements for Telegram/Web/TUI fallback flows. (#18162) Thanks @mbelinky and @Marvae.
 - iOS/Gateway: stabilize connect/discovery state handling, add onboarding reset recovery in Settings, and fix iOS gateway-controller coverage for command-surface and last-connection persistence behavior. (#18164) Thanks @mbelinky.
diff --git a/src/agents/tools/cron-tool.flat-params.test.ts b/src/agents/tools/cron-tool.flat-params.test.ts
new file mode 100644
index 0000000000..2a96b45107
--- /dev/null
+++ b/src/agents/tools/cron-tool.flat-params.test.ts
@@ -0,0 +1,36 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const callGatewayMock = vi.fn();
+vi.mock("../../gateway/call.js", () => ({
+  callGateway: (opts: unknown) => callGatewayMock(opts),
+}));
+
+vi.mock("../agent-scope.js", () => ({
+  resolveSessionAgentId: () => "agent-123",
+}));
+
+import { createCronTool } from "./cron-tool.js";
+
+describe("cron tool flat-params", () => {
+  beforeEach(() => {
+    callGatewayMock.mockReset();
+    callGatewayMock.mockResolvedValue({ ok: true });
+  });
+
+  it("preserves explicit top-level sessionKey during flat-params recovery", async () => {
+    const tool = createCronTool({ agentSessionKey: "agent:main:discord:channel:ops" });
+    await tool.execute("call-flat-session-key", {
+      action: "add",
+      sessionKey: "agent:main:telegram:group:-100123:topic:99",
+      schedule: { kind: "at", at: new Date(123).toISOString() },
+      message: "do stuff",
+    });
+
+    const call = callGatewayMock.mock.calls[0]?.[0] as {
+      method?: string;
+      params?: { sessionKey?: string };
+    };
+    expect(call.method).toBe("cron.add");
+    expect(call.params?.sessionKey).toBe("agent:main:telegram:group:-100123:topic:99");
+  });
+});
diff --git a/src/agents/tools/cron-tool.ts b/src/agents/tools/cron-tool.ts
index 3cae9b24f9..e977ed8302 100644
--- a/src/agents/tools/cron-tool.ts
+++ b/src/agents/tools/cron-tool.ts
@@ -299,6 +299,7 @@ Use jobId as the canonical identifier; id is accepted for compatibility. Use con
               "description",
               "deleteAfterRun",
               "agentId",
+              "sessionKey",
               "message",
               "text",
               "model",
diff --git a/src/gateway/server-cron.test.ts b/src/gateway/server-cron.test.ts
new file mode 100644
index 0000000000..1cbf93c625
--- /dev/null
+++ b/src/gateway/server-cron.test.ts
@@ -0,0 +1,81 @@
+import os from "node:os";
+import path from "node:path";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import type { CliDeps } from "../cli/deps.js";
+import type { OpenClawConfig } from "../config/config.js";
+
+const enqueueSystemEventMock = vi.fn();
+const requestHeartbeatNowMock = vi.fn();
+const loadConfigMock = vi.fn();
+
+vi.mock("../infra/system-events.js", () => ({
+  enqueueSystemEvent: (...args: unknown[]) => enqueueSystemEventMock(...args),
+}));
+
+vi.mock("../infra/heartbeat-wake.js", () => ({
+  requestHeartbeatNow: (...args: unknown[]) => requestHeartbeatNowMock(...args),
+}));
+
+vi.mock("../config/config.js", async () => {
+  const actual = await vi.importActual<typeof import("../config/config.js")>("../config/config.js");
+  return {
+    ...actual,
+    loadConfig: () => loadConfigMock(),
+  };
+});
+
+import { buildGatewayCronService } from "./server-cron.js";
+
+describe("buildGatewayCronService", () => {
+  beforeEach(() => {
+    enqueueSystemEventMock.mockReset();
+    requestHeartbeatNowMock.mockReset();
+    loadConfigMock.mockReset();
+  });
+
+  it("canonicalizes non-agent sessionKey to agent store key for enqueue + wake", async () => {
+    const tmpDir = path.join(os.tmpdir(), `server-cron-${Date.now()}`);
+    const cfg = {
+      session: {
+        mainKey: "main",
+      },
+      cron: {
+        store: path.join(tmpDir, "cron.json"),
+      },
+    } as OpenClawConfig;
+    loadConfigMock.mockReturnValue(cfg);
+
+    const state = buildGatewayCronService({
+      cfg,
+      deps: {} as CliDeps,
+      broadcast: () => {},
+    });
+    try {
+      const job = await state.cron.add({
+        name: "canonicalize-session-key",
+        enabled: true,
+        schedule: { kind: "at", at: new Date(1).toISOString() },
+        sessionTarget: "main",
+        wakeMode: "next-heartbeat",
+        sessionKey: "discord:channel:ops",
+        payload: { kind: "systemEvent", text: "hello" },
+      });
+
+      await state.cron.run(job.id, "force");
+
+      expect(enqueueSystemEventMock).toHaveBeenCalledWith(
+        "hello",
+        expect.objectContaining({
+          sessionKey: "agent:main:discord:channel:ops",
+        }),
+      );
+      expect(requestHeartbeatNowMock).toHaveBeenCalledWith(
+        expect.objectContaining({
+          sessionKey: "agent:main:discord:channel:ops",
+        }),
+      );
+    } finally {
+      state.cron.stop();
+    }
+  });
+});
diff --git a/src/gateway/server-cron.ts b/src/gateway/server-cron.ts
index 68ba542394..cd0b565cb9 100644
--- a/src/gateway/server-cron.ts
+++ b/src/gateway/server-cron.ts
@@ -16,7 +16,7 @@ import { runHeartbeatOnce } from "../infra/heartbeat-runner.js";
 import { requestHeartbeatNow } from "../infra/heartbeat-wake.js";
 import { enqueueSystemEvent } from "../infra/system-events.js";
 import { getChildLogger } from "../logging.js";
-import { normalizeAgentId } from "../routing/session-key.js";
+import { normalizeAgentId, toAgentStoreSessionKey } from "../routing/session-key.js";
 import { defaultRuntime } from "../runtime.js";
 
 export type GatewayCronState = {
@@ -98,10 +98,15 @@ export function buildGatewayCronService(params: {
         agentId: params.agentId,
       });
     }
+    const candidate = toAgentStoreSessionKey({
+      agentId: params.agentId,
+      requestKey: requested,
+      mainKey: params.runtimeConfig.session?.mainKey,
+    });
     const canonical = canonicalizeMainSessionAlias({
       cfg: params.runtimeConfig,
       agentId: params.agentId,
-      sessionKey: requested,
+      sessionKey: candidate,
     });
     if (canonical !== "global") {
       const sessionAgentId = resolveAgentIdFromSessionKey(canonical);