getsentry · s1gr1d · Jul 29, 2026 · Jul 29, 2026 · Jul 29, 2026 · Jul 29, 2026
@@ -2,13 +2,7 @@ import * as Sentry from '@sentry/browser';
 
 window.Sentry = Sentry;
 
-window._errorCount = 0;
-
 Sentry.init({
   dsn: 'https://public@dsn.ingest.sentry.io/1337',
   sampleRate: '0',
-  beforeSend() {
-    window._errorCount++;
-    return null;
-  },
 });
@@ -1,15 +1,14 @@
 import { expect } from '@playwright/test';
 import { sentryTest } from '../../../../utils/fixtures';
+import { countEnvelopes } from '../../../../utils/helpers';
 
-sentryTest('parses a string sample rate', async ({ getLocalTestUrl, page }) => {
+sentryTest('drops error events when sampleRate is the string "0"', async ({ getLocalTestUrl, page }) => {
   const url = await getLocalTestUrl({ testDir: __dirname });
+  const errorCountPromise = countEnvelopes(page, { envelopeType: 'event', timeout: 2000 });
 
   await page.goto(url);
-
   await page.waitForFunction('window._testDone');
   await page.evaluate('window.Sentry.getClient().flush()');
 
-  const count = await page.evaluate('window._errorCount');
-
-  expect(count).toStrictEqual(0);
+  expect(await errorCountPromise).toBe(0);
 });
@@ -0,0 +1,10 @@
+import * as Sentry from '@sentry/browser';
+
+window.Sentry = Sentry;
+
+Sentry.init({
+  traceLifecycle: 'static',
+  dsn: 'https://public@dsn.ingest.sentry.io/1337',
+  release: '0.1',
+  sampleRate: 0,
+});
@@ -0,0 +1,7 @@
+document.getElementById('throw-error').addEventListener('click', () => {
+  throw new Error('unhandled crash');
+});
+
+document.getElementById('capture-exception').addEventListener('click', () => {
+  Sentry.captureException(new Error('handled capture'));
+});
@@ -0,0 +1,10 @@
+<!doctype html>
+<html>
+  <head>
+    <meta charset="utf-8" />
+  </head>
+  <body>
+    <button id="throw-error">Throw Error</button>
+    <button id="capture-exception">Capture Exception</button>
+  </body>
+</html>
@@ -0,0 +1,53 @@
+import { expect } from '@playwright/test';
+import { sentryTest } from '../../../utils/fixtures';
+import { countEnvelopes, waitForSession } from '../../../utils/helpers';
+
+sentryTest(
+  'marks session as crashed when unhandled error is sampled out by sampleRate',
+  async ({ getLocalTestUrl, page }) => {
+    const url = await getLocalTestUrl({ testDir: __dirname });
+
+    const pageloadSessionPromise = waitForSession(page, s => !!s.init && s.status === 'ok');
+    await page.goto(url);
+    const pageloadSession = await pageloadSessionPromise;
+
+    const updatedSessionPromise = waitForSession(page, s => !s.init && s.status !== 'ok');
+    const errorCountPromise = countEnvelopes(page, { envelopeType: 'event', timeout: 2000 });
+    await page.locator('#throw-error').click();
+    const updatedSession = await updatedSessionPromise;
+    const errorCount = await errorCountPromise;
+
+    // The error event is not sent — it was sampled out
+    expect(errorCount).toBe(0);
+
+    // But the session update is still sent, reflecting the crash
+    expect(updatedSession.sid).toBe(pageloadSession.sid);
+    expect(updatedSession.errors).toBe(1);
+    expect(updatedSession.status).toBe('crashed');
+  },
+);
+
+sentryTest(
+  'marks session as errored when handled exception is sampled out by sampleRate',
+  async ({ getLocalTestUrl, page }) => {
+    const url = await getLocalTestUrl({ testDir: __dirname });
+
+    const pageloadSessionPromise = waitForSession(page, s => !!s.init && s.status === 'ok');
+    await page.goto(url);
+    const pageloadSession = await pageloadSessionPromise;
+
+    const updatedSessionPromise = waitForSession(page, s => !s.init);
+    const errorCountPromise = countEnvelopes(page, { envelopeType: 'event', timeout: 2000 });
+    await page.locator('#capture-exception').click();
+    const updatedSession = await updatedSessionPromise;
+    const errorCount = await errorCountPromise;
+
+    // The error event is not sent — it was sampled out
+    expect(errorCount).toBe(0);
+
+    // But the session update is still sent, recording the error
+    expect(updatedSession.sid).toBe(pageloadSession.sid);
+    expect(updatedSession.errors).toBe(1);
+    expect(updatedSession.status).toBe('ok');
+  },
+);
diff --git a/packages/core/src/client.ts b/packages/core/src/client.ts
@@ -52,7 +52,6 @@ import { makePromiseBuffer, type PromiseBuffer, SENTRY_BUFFER_FULL_ERROR } from
 import { safeMathRandom } from './utils/randomSafeContext';
 import { reparentChildSpans, shouldIgnoreSpan } from './utils/should-ignore-span';
 import { showSpanDropWarning } from './utils/spanUtils';
-import { rejectedSyncPromise } from './utils/syncpromise';
 import { safeUnref } from './utils/timer';
 import { convertSpanJsonToTransactionEvent, convertTransactionEventToSpanJson } from './utils/transactionEvent';
 import { resolveDataCollectionOptions } from './utils/data-collection/resolveDataCollectionOptions';
@@ -1438,15 +1437,6 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
     // 0.0 === 0% events are sent
     // Sampling for transaction happens somewhere else
     const parsedSampleRate = typeof sampleRate === 'undefined' ? undefined : parseSampleRate(sampleRate);
-    if (isError && typeof parsedSampleRate === 'number' && safeMathRandom() > parsedSampleRate) {
-      this.recordDroppedEvent('sample_rate', 'error');
-      return rejectedSyncPromise(
-        _makeDoNotSendEventError(
-          `Discarding event because it's not included in the random sample (sampling rate = ${sampleRate})`,
-        ),
-      );
-    }
-
     const dataCategory = getDataCategoryByType(event.type);
 
     return this._prepareEvent(event, hint, currentScope, isolationScope)
@@ -1481,6 +1471,13 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
           this._updateSessionFromEvent(session, processedEvent);
         }
 
+        if (isError && typeof parsedSampleRate === 'number' && safeMathRandom() > parsedSampleRate) {
+          this.recordDroppedEvent('sample_rate', 'error');
+          throw _makeDoNotSendEventError(
+            `Discarding event because it's not included in the random sample (sampling rate = ${sampleRate})`,
+          );
+        }
+
         if (isTransaction) {
           const spanCountBefore = processedEvent.sdkProcessingMetadata?.spanCountBeforeProcessing || 0;
           const spanCountAfter = processedEvent.spans ? processedEvent.spans.length : 0;

diff --git a/packages/core/src/exports.ts b/packages/core/src/exports.ts
@@ -174,7 +174,7 @@ export function setConversationId(conversationId: string | null | undefined): vo
  * isolation scope. If you call this function after handling a certain error and another error
  * is captured in between, the last one is returned instead of the one you might expect.
  * Also, ids of events that were never sent to Sentry (for example because
- * they were dropped in `beforeSend`) could be returned.
+ * they were dropped by sampling or `beforeSend`) could be returned.
  *
  * @returns The last event id of the isolation scope.
  */