fix(core): keep events buffered when a WaitingPlugin is added before …

packages/core/src/analytics.ts

@@ -334,10 +334,14 @@ export class SegmentClient {
       ]);
       await this.onReady();
       this.isReady.value = true;
-      // Set running to true to start event processing
-      await this.store.running.set(true);
-      // Process all pending events
-      await this.processPendingEvents();
+      if (this.waitingPlugins.size === 0) {
+        // Set running to true to start event processing
+        await this.store.running.set(true);
+      }
+      if (this.store.running.get()) {
+        // Process all pending events
+        await this.processPendingEvents();
+      }
       // Trigger manual flush
       this.flushPolicyExecuter.manualFlush();
     } catch (error) {
@@ -1131,15 +1135,11 @@ export class SegmentClient {
    * @param timeout - Milliseconds to wait before auto-resuming (default: 30000)
    */
   pauseEventProcessing(timeout = 30000) {
-    // IMPORTANT: ignore repeated pauses
-    const running = this.store.running.get();
-    if (!running) {
-      return;
+    if (this.store.running.get()) {
+      // Fire-and-forget: state is updated synchronously in-memory, persistence happens async
+      void this.store.running.set(false);
     }
 
-    // Fire-and-forget: state is updated synchronously in-memory, persistence happens async
-    void this.store.running.set(false);
-
     // Only set timeout if not already set (prevents multiple waiting plugins from overwriting)
     if (!this.resumeTimeoutId) {
       this.resumeTimeoutId = setTimeout(async () => {
@@ -1164,6 +1164,9 @@ export class SegmentClient {
       this.resumeTimeoutId = undefined;
     }
     await this.store.running.set(true);
-    await this.processPendingEvents();
+    if (this.isReady.value) {
+      // Before init the timeline isn't configured yet, init() drains the buffer instead
+      await this.processPendingEvents();
+    }
   }
 }

packages/core/src/plugins/__tests__/Waiting.test.ts

@@ -12,6 +12,8 @@ import {
 } from '../../test-helpers';
 import { TrackEventType } from '../../types';
 
+jest.mock('../../api');
+
 jest.useFakeTimers();
 
 // Type for accessing internal client properties in tests
@@ -526,6 +528,65 @@ describe('WaitingPlugin', () => {
     expect(await client.running.get(true)).toBe(true);
   });
 
+  test('WaitingPlugin added before init keeps events buffered until resume', async () => {
+    // Mirrors the real createClient() flow: the plugin is added before init() finishes
+    const preInitStore = new MockSegmentStore({
+      isReady: true,
+      running: false,
+    });
+
+    const client = new SegmentClient({
+      config: baseConfig,
+      logger: getMockLogger(),
+      store: preInitStore,
+    });
+
+    const plugin = new ManualResumeWaitingPlugin();
+    client.add({ plugin });
+
+    client.track('Application Opened');
+    await Promise.resolve();
+
+    expect(plugin.tracked).toBe(false);
+
+    await client.init();
+
+    expect(await client.running.get(true)).toBe(false);
+    expect(plugin.tracked).toBe(false);
+
+    await plugin.resume();
+
+    expect(await client.running.get(true)).toBe(true);
+    expect(plugin.tracked).toBe(true);
+    expect(await preInitStore.pendingEvents.get(true)).toHaveLength(0);
+  });
+
+  test('WaitingPlugin added before init still force resumes on timeout', async () => {
+    const preInitStore = new MockSegmentStore({
+      isReady: true,
+      running: false,
+    });
+
+    const client = new SegmentClient({
+      config: baseConfig,
+      logger: getMockLogger(),
+      store: preInitStore,
+    });
+
+    const plugin = new ManualResumeWaitingPlugin();
+    client.add({ plugin });
+
+    client.track('Application Opened');
+    await client.init();
+
+    expect(plugin.tracked).toBe(false);
+
+    await jest.advanceTimersByTimeAsync(30000);
+
+    expect(await client.running.get(true)).toBe(true);
+    expect(plugin.tracked).toBe(true);
+  });
+
   test('pending events queue is capped at maxPendingEvents', async () => {
     const client = new SegmentClient({
       config: baseConfig,