diff --git a/plugin/index.ts b/plugin/index.ts
index 253acb0..65b5c12 100644
--- a/plugin/index.ts
+++ b/plugin/index.ts
@@ -25,6 +25,25 @@ import {
   CalendarScheduler,
 } from './calendar/index.js';
 
+// ---------------------------------------------------------------------------
+// Module-scope calendar scheduler singleton.
+//
+// `register()` is called multiple times per gateway boot — once per agent
+// (we see 5 `HarborForge plugin registered` lines for 5 agents on dind-t2).
+// `gateway_start` only fires once, so before this lift the
+// `startCalendarScheduler()` setup ran inside ONE closure while four other
+// closures kept their own `calendarScheduler = null`. Whichever of the five
+// tool registrations the gateway picked at call time was effectively a coin
+// flip, and four times out of five `harborforge_calendar_status` returned
+// `Calendar scheduler not running` even though the scheduler was active.
+//
+// Keeping the singleton at module scope removes the per-`register()` shadow:
+// the scheduler is started once, every closure reads the same binding, and
+// `startCalendarScheduler()` is idempotent so duplicate `gateway_start`
+// firings are harmless.
+// ---------------------------------------------------------------------------
+let calendarScheduler: MultiAgentSchedulerHandle | CalendarScheduler | null = null;
+
 interface PluginAPI {
   logger: {
     info: (...args: any[]) => void;
@@ -108,7 +127,7 @@ function register(api: PluginAPI): void {
         },
         openclaw: {
           version: api.runtime?.version || api.version || 'unknown',
-          pluginVersion: '0.3.2', // Bumped for PLG-CAL-004
+          pluginVersion: '0.3.3', // Bumped for PLG-CAL-004
         },
         timestamp: new Date().toISOString(),
       };
@@ -117,13 +136,9 @@ function register(api: PluginAPI): void {
     // Periodic metadata push interval handle
     let metaPushInterval: ReturnType<typeof setInterval> | null = null;
 
-    // Calendar scheduler instance.
-    //
-    // In multi-agent sync mode (the only path today) this is a
-    // {@link MultiAgentSchedulerHandle}. The legacy `CalendarScheduler` type
-    // is retained in the union for compatibility with the typed-only single-
-    // agent path that may be reintroduced later.
-    let calendarScheduler: MultiAgentSchedulerHandle | CalendarScheduler | null = null;
+    // (calendarScheduler is module-scope — see top of file for the why.
+    //  Tools and lifecycle hooks all reference the same binding so the
+    //  multi-register/single-start mismatch can't shadow them again.)
 
     /**
      * Push OpenClaw metadata to the Monitor bridge.
@@ -147,7 +162,7 @@ function register(api: PluginAPI): void {
 
       const meta: OpenClawMeta = {
         version: api.runtime?.version || api.version || 'unknown',
-        plugin_version: '0.3.2',
+        plugin_version: '0.3.3',
         agents: agentNames.map(name => ({ name })),
       };
 
@@ -291,8 +306,16 @@ function register(api: PluginAPI): void {
 
     /**
      * Initialize and start the calendar scheduler.
+     *
+     * Idempotent — `gateway_start` may fire once per `register()` invocation
+     * (the host calls `register` per agent), and we only want one set of
+     * sync/check intervals across the whole process.
      */
     function startCalendarScheduler(): void {
+      if (calendarScheduler) {
+        logger.info('Calendar scheduler already started, skipping duplicate gateway_start');
+        return;
+      }
       const live = resolveConfig();
 
       // Create bridge client (claw-instance level, not per-agent)
diff --git a/plugin/package.json b/plugin/package.json
index cc77f67..afd2b44 100644
--- a/plugin/package.json
+++ b/plugin/package.json
@@ -1,6 +1,6 @@
 {
   "name": "harbor-forge-plugin",
-  "version": "0.3.2",
+  "version": "0.3.3",
   "description": "OpenClaw plugin for HarborForge monitor bridge and CLI integration",
   "type": "module",
   "main": "dist/index.js",