feat(core): Record callback_error client reports for throwing user callbacks#23903

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feat(core): Record callback_error client reports for throwing user callbacks #23903

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2 changes: 1 addition & 1 deletion ...ages/node-integration-tests/suites/client-reports/drop-reasons/before-send-throws/test.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when beforeSend throws',
{
category: 'error',
quantity: 1,
reason: 'before_send',
reason: 'callback_error',
},
],
},
Expand Down
4 changes: 2 additions & 2 deletions .../node-integration-tests/suites/client-reports/drop-reasons/event-processor-throws/test.ts
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Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when an event processor t
{
category: 'error',
quantity: 1,
reason: 'event_processor',
reason: 'callback_error',
},
],
},
Expand All@@ -32,7 +32,7 @@ test('records a client report and no extra error event when an async event proce
{
category: 'error',
quantity: 1,
reason: 'event_processor',
reason: 'callback_error',
},
],
},
Expand Down
2 changes: 1 addition & 1 deletion ...s/node-integration-tests/suites/client-reports/drop-reasons/traces-sampler-throws/test.ts
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Expand Up@@ -14,7 +14,7 @@ test('records a client report and no error event when tracesSampler throws', asy
{
category: 'span',
quantity: 1,
reason: 'sample_rate',
reason: 'callback_error',
},
],
},
Expand Down
49 changes: 28 additions & 21 deletions packages/core/src/client.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,7 @@ import { parseSampleRate } from './utils/parseSampleRate';
import { prepareEvent } from './utils/prepareEvent';
import { makePromiseBuffer, type PromiseBuffer, SENTRY_BUFFER_FULL_ERROR } from './utils/promisebuffer';
import { safeMathRandom } from './utils/randomSafeContext';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { reparentChildSpans, shouldIgnoreSpan } from './utils/should-ignore-span';
import { safeUnref } from './utils/timer';
import { convertSpanJsonToTransactionEvent, convertTransactionEventToSpanJson } from './utils/transactionEvent';
Expand DownExpand Up@@ -1522,6 +1522,14 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
const parsedSampleRate = typeof sampleRate === 'undefined' ? undefined : parseSampleRate(sampleRate);
const dataCategory = getDataCategoryByType(event.type);

const recordDroppedEvent = (reason: EventDropReason): void => {
this.recordDroppedEvent(reason, dataCategory);
if (isTransaction) {
// the transaction itself counts as one span, plus all the child spans that are added
this.recordDroppedEvent(reason, 'span', 1 + (event.spans || []).length);
}
};

return this._prepareEvent(event, hint, currentScope, isolationScope)
.then(prepared => {
if (prepared === null) {
Expand All@@ -1539,13 +1547,7 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
})
.then(processedEvent => {
if (processedEvent === null) {
this.recordDroppedEvent('before_send', dataCategory);
if (isTransaction) {
const spans = event.spans || [];
// the transaction itself counts as one span, plus all the child spans that are added
const spanCount = 1 + spans.length;
this.recordDroppedEvent('before_send', 'span', spanCount);
}
recordDroppedEvent('before_send');
throw _makeDoNotSendEventError(`${beforeSendLabel} returned \`null\`, will not send event.`);
}

Expand DownExpand Up@@ -1587,6 +1589,11 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
return processedEvent;
})
.then(null, reason => {
if (reason === CALLBACK_ERROR) {
recordDroppedEvent('callback_error');
throw _makeDoNotSendEventError('A user callback threw an error, will not send event.');
}

if (_isDoNotSendEventError(reason) || _isInternalError(reason)) {
throw reason;
}
Expand DownExpand Up@@ -1702,17 +1709,13 @@ function _validateBeforeSendResult(
): PromiseLike<Event | null> | Event | null {
const invalidValueError = `${beforeSendLabel} must return \`null\` or a valid event.`;
if (isThenable(beforeSendResult)) {
return beforeSendResult.then(
event => {
if (!isPlainObject(event) && event !== null) {
throw _makeInternalError(invalidValueError);
}
return event;
},
e => {
throw _makeInternalError(`${beforeSendLabel} rejected with ${e}`);
},
);
// A rejection can only be `CALLBACK_ERROR` here, as `safeCallback` already handled the user callback rejecting
return beforeSendResult.then(event => {
if (!isPlainObject(event) && event !== null) {
throw _makeInternalError(invalidValueError);
}
return event;
});
} else if (!isPlainObject(beforeSendResult) && beforeSendResult !== null) {
throw _makeInternalError(invalidValueError);
}
Expand DownExpand Up@@ -1743,7 +1746,9 @@ function processBeforeSend(
return safeCallback(
DEBUG_BUILD ? 'The `beforeSend` callback threw an error, dropping the event:' : '',
() => beforeSend(errorEvent, hint),
() => null,
() => {
throw CALLBACK_ERROR;
},
);
}

Expand DownExpand Up@@ -1818,7 +1823,9 @@ function processBeforeSend(
return safeCallback(
DEBUG_BUILD ? 'The `beforeSendTransaction` callback threw an error, dropping the event:' : '',
() => beforeSendTransaction(processedEvent as TransactionEvent, hint),
() => null,
() => {
throw CALLBACK_ERROR;
},
);
}
}
Expand Down
7 changes: 5 additions & 2 deletions packages/core/src/eventProcessors.ts
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Expand Up@@ -3,11 +3,12 @@ import type { Event, EventHint } from './types/event';
import type { EventProcessor } from './types/eventprocessor';
import { debug } from './utils/debug-logger';
import { isThenable } from './utils/is';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { rejectedSyncPromise, resolvedSyncPromise } from './utils/syncpromise';

/**
* Process an array of event processors, returning the processed event (or `null` if the event was dropped).
* Rejects with `CALLBACK_ERROR` if a processor throws.
*/
export function notifyEventProcessors(
processors: EventProcessor[],
Expand DownExpand Up@@ -40,7 +41,9 @@ function _notifyEventProcessors(
const result = safeCallback(
DEBUG_BUILD ? `${processorName} threw an error, dropping event:` : '',
() => processor({ ...event }, hint),
() => null,
() => {
throw CALLBACK_ERROR;

@Lms24Lms24Sep 3, 2026•
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m: throwing here and in client.ts made me a bit suspicious because we have to be really careful to also catch our throws. Looks like there's a case in replay where we also call prepareEvent which doesn't try/catch the call. I think this only concerns event processor throws though. This leads to us trying to re-send the replay because we assume a network error. Ultimately, we stop recording.

I think we have two options how to avoid this:

  1. we try/catch in Replay so that this doesn't happen
  2. we don't throw at all. Instead, we could directly record an dropped event in notifyEventProcessors and distinguish there.

Tbqh: I haven't thought this through end-to-end, so maybe 1 is easier. I don't see us reusing prepareEvent much in the foreseeable future. But happy to let you make the call (also feel free to come up with something else).

},
);

DEBUG_BUILD && result === null && debug.log(`${processorName} dropped event`);
Expand Down
10 changes: 7 additions & 3 deletions packages/core/src/logs/internal.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Log, SerializedLog } from '../types/log';
import { consoleSandbox, debug } from '../utils/debug-logger';
import { isParameterizedString } from '../utils/is';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -144,13 +144,17 @@ export function _INTERNAL_captureLog(
client.emit('beforeCaptureLog', processedLog);

const log = beforeSendLog
? safeCallback(
? safeCallback<Log | null | typeof CALLBACK_ERROR>(
DEBUG_BUILD ? 'The `beforeSendLog` callback threw an error, dropping the log:' : '',
// We need to wrap this in `consoleSandbox` to avoid recursive calls to `beforeSendLog`
() => consoleSandbox(() => beforeSendLog(processedLog)),
() => null,
() => CALLBACK_ERROR,
)
: processedLog;
if (log === CALLBACK_ERROR) {
client.recordDroppedEvent('callback_error', 'log_item', 1);
return;
}
if (!log) {
client.recordDroppedEvent('before_send', 'log_item', 1);
DEBUG_BUILD && debug.warn('beforeSendLog returned null, log will not be captured.');
Expand Down
11 changes: 8 additions & 3 deletions packages/core/src/metrics/internal.ts
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Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Metric, SerializedMetric } from '../types/metric';
import type { User } from '../types/user';
import { debug } from '../utils/debug-logger';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -183,13 +183,18 @@ export function _INTERNAL_captureMetric(beforeMetric: Metric, options?: Internal
client.emit('processMetric', enrichedMetric);

const processedMetric = beforeSendMetric
? safeCallback(
? safeCallback<Metric | null | typeof CALLBACK_ERROR>(
DEBUG_BUILD ? 'The `beforeSendMetric` callback threw an error, dropping the metric:' : '',
() => beforeSendMetric(enrichedMetric),
() => null,
() => CALLBACK_ERROR,
)
: enrichedMetric;

if (processedMetric === CALLBACK_ERROR) {
client.recordDroppedEvent('callback_error', 'metric', 1);
return;
}

if (!processedMetric) {
client.recordDroppedEvent('before_send', 'metric', 1);
DEBUG_BUILD && debug.log('`beforeSendMetric` returned `null`, will not send metric.');
Expand Down
22 changes: 16 additions & 6 deletions packages/core/src/tracing/sampling.ts
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Expand Up@@ -6,6 +6,14 @@ import { hasSpansEnabled } from '../utils/hasSpansEnabled';
import { parseSampleRate } from '../utils/parseSampleRate';
import { safeCallback } from '../utils/safeCallback';

interface SamplingDecision {
sampled: boolean;
sampleRate?: number;
localSampleRateWasApplied?: boolean;
/** Set when the span was dropped for a reason other than the sampling decision itself. */
dropReason?: 'callback_error';
}

/**
* Makes a sampling decision for the given options.
*
Expand All@@ -16,15 +24,17 @@ export function sampleSpan(
options: Pick<CoreOptions, 'tracesSampleRate' | 'tracesSampler'>,
samplingContext: SamplingContext,
sampleRand: number,
): [sampled: boolean, sampleRate?: number, localSampleRateWasApplied?: boolean] {
): SamplingDecision {

@Lms24Lms24Sep 3, 2026

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m: this is API breaking, since sampleSpan is exported. I agree that the object is easier to read though . IIRC, we used the named tuple here for bundle size minimization but this is less readable than the refactor.

Breaking here isn't a big deal though, so we can also do it if the tuple no longer works. But if we do, let's add a note in the migration guide.

// nothing to do if span recording is not enabled
if (!hasSpansEnabled(options)) {
return [false];
return { sampled: false };
}

const resolved = resolveSampleRate(options, samplingContext);
if (!resolved) {
return [false];
// `hasSpansEnabled` guarantees either `tracesSampleRate` or `tracesSampler` is set, so the only way to end up
// without a sample rate is a throwing `tracesSampler` with nothing to fall back to.
return { sampled: false, dropReason: 'callback_error' };
}
const [sampleRate, localSampleRateWasApplied] = resolved;

Expand All@@ -39,7 +49,7 @@ export function sampleSpan(
sampleRate,
)} of type ${JSON.stringify(typeof sampleRate)}.`,
);
return [false];
return { sampled: false };
}

// if the function returned 0 (or false), or if `tracesSampleRate` is 0, it's a sign the transaction should be dropped
Expand All@@ -52,7 +62,7 @@ export function sampleSpan(
: 'a negative sampling decision was inherited or tracesSampleRate is set to 0'
}`,
);
return [false, parsedSampleRate, localSampleRateWasApplied];
return { sampled: false, sampleRate: parsedSampleRate, localSampleRateWasApplied };
}

// We always compare the sample rand for the current execution context against the chosen sample rate.
Expand All@@ -69,7 +79,7 @@ export function sampleSpan(
);
}

return [shouldSample, parsedSampleRate, localSampleRateWasApplied];
return { sampled: shouldSample, sampleRate: parsedSampleRate, localSampleRateWasApplied };
}

/**
Expand Down
6 changes: 3 additions & 3 deletions packages/core/src/tracing/trace.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -495,8 +495,8 @@ function _startRootSpan(
const currentPropagationContext = scope.getPropagationContext();
const _isTracingSuppressed = isTracingSuppressed(scope);

const [sampled, sampleRate, localSampleRateWasApplied] = _isTracingSuppressed
? [false]
const { sampled, sampleRate, localSampleRateWasApplied, dropReason } = _isTracingSuppressed
? { sampled: false }
: sampleSpan(
options,
{
Expand All@@ -522,7 +522,7 @@ function _startRootSpan(

if (!sampled && client && !_isTracingSuppressed) {
DEBUG_BUILD && debug.log('[Tracing] Discarding root span because its trace was not chosen to be sampled.');
client.recordDroppedEvent('sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
client.recordDroppedEvent(dropReason || 'sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
}

setCapturedScopesOnSpan(rootSpan, scope, isolationScope);
Expand Down
1 change: 1 addition & 0 deletions packages/core/src/types/clientreport.ts
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Expand Up@@ -2,6 +2,7 @@ import type { DataCategory } from './datacategory';

export type EventDropReason =
| 'before_send'
| 'callback_error'
| 'event_processor'
| 'network_error'
| 'queue_overflow'
Expand Down
7 changes: 7 additions & 0 deletions packages/core/src/utils/safeCallback.ts
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Expand Up@@ -2,6 +2,13 @@ import { DEBUG_BUILD } from '../debug-build';
import { debug } from './debug-logger';
import { isThenable } from './is';

/**
* Lets a `safeCallback` fallback signal "the callback failed" as opposed to "the callback returned `null`",
* so the call site can report the drop as `callback_error`. Return it from synchronous call sites; throw it
* to abort a promise chain.
*/
export const CALLBACK_ERROR = Symbol.for('SentryCallbackError');

/**
* Invokes a user-provided callback (e.g. `beforeSend`, `tracesSampler`, an integration hook) so that
* neither a synchronous throw nor a rejected promise escapes into the caller. On failure the error is
Expand Down
16 changes: 8 additions & 8 deletions packages/core/test/lib/client.test.ts
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Expand Up@@ -2222,7 +2222,7 @@ describe('Client', () => {

expect(TestClient.instance!.event).toBeUndefined();
expect(captureExceptionSpy).not.toHaveBeenCalled();
expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
});

Expand All@@ -2244,7 +2244,7 @@ describe('Client', () => {

expect(TestClient.instance!.event).toBeUndefined();
expect(captureExceptionSpy).not.toHaveBeenCalled();
expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
});

Expand DownExpand Up@@ -2277,7 +2277,7 @@ describe('Client', () => {

expect(TestClient.instance!.event).toBeUndefined();
expect(captureExceptionSpy).not.toHaveBeenCalled();
expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
});

test('a rejecting event processor stops the processor chain', async () => {
Expand DownExpand Up@@ -2312,7 +2312,7 @@ describe('Client', () => {

expect(TestClient.instance!.event).toBeUndefined();
expect(captureExceptionSpy).not.toHaveBeenCalled();
expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
});

test('client-level event processor that throws on all events does not capture a new event', () => {
Expand DownExpand Up@@ -2348,7 +2348,7 @@ describe('Client', () => {
expect(beforeSend).toHaveBeenCalledTimes(1);
expect(TestClient.instance!.event).toBeUndefined();
expect(captureExceptionSpy).not.toHaveBeenCalled();
expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
expect(recordDroppedEventSpy).toHaveBeenCalledTimes(1);
expect(debugErrorSpy).toHaveBeenCalledWith(
'The `beforeSend` callback threw an error, dropping the event:',
Expand All@@ -2373,7 +2373,7 @@ describe('Client', () => {
expect(beforeSend).toHaveBeenCalledTimes(1);
expect(TestClient.instance!.event).toBeUndefined();
expect(captureExceptionSpy).not.toHaveBeenCalled();
expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
expect(debugErrorSpy).toHaveBeenCalledWith(
'The `beforeSend` callback threw an error, dropping the event:',
exception,
Expand DownExpand Up@@ -2416,8 +2416,8 @@ describe('Client', () => {

expect(TestClient.instance!.event).toBeUndefined();
expect(captureExceptionSpy).not.toHaveBeenCalled();
expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'transaction');
expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'span', 3);
expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'transaction');
expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'span', 3);
expect(debugErrorSpy).toHaveBeenCalledWith(
'The `beforeSendTransaction` callback threw an error, dropping the event:',
exception,
Expand Down
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 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

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feat(core): Record callback_error client reports for throwing user callbacks#23903

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msonnb
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+114

−75

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feat(core): Record callback_error client reports for throwing user callbacks
#23903
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2 changes: 1 addition & 1 deletion
...ages/node-integration-tests/suites/client-reports/drop-reasons/before-send-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when beforeSend throws',
 {
 category: 'error',
 quantity: 1,
 reason: 'before_send',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

4 changes: 2 additions & 2 deletions
.../node-integration-tests/suites/client-reports/drop-reasons/event-processor-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when an event processor t
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand All@@ -32,7 +32,7 @@ test('records a client report and no extra error event when an async event proce
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

2 changes: 1 addition & 1 deletion
...s/node-integration-tests/suites/client-reports/drop-reasons/traces-sampler-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no error event when tracesSampler throws', asy
 {
 category: 'span',
 quantity: 1,
 reason: 'sample_rate',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

49 changes: 28 additions & 21 deletions
packages/core/src/client.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,7 @@ import { parseSampleRate } from './utils/parseSampleRate';
import { prepareEvent } from './utils/prepareEvent';
import { makePromiseBuffer, type PromiseBuffer, SENTRY_BUFFER_FULL_ERROR } from './utils/promisebuffer';
import { safeMathRandom } from './utils/randomSafeContext';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { reparentChildSpans, shouldIgnoreSpan } from './utils/should-ignore-span';
import { safeUnref } from './utils/timer';
import { convertSpanJsonToTransactionEvent, convertTransactionEventToSpanJson } from './utils/transactionEvent';
Expand DownExpand Up@@ -1522,6 +1522,14 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 const parsedSampleRate = typeof sampleRate === 'undefined' ? undefined : parseSampleRate(sampleRate);
 const dataCategory = getDataCategoryByType(event.type);

 const recordDroppedEvent = (reason: EventDropReason): void => {
 this.recordDroppedEvent(reason, dataCategory);
 if (isTransaction) {
 // the transaction itself counts as one span, plus all the child spans that are added
 this.recordDroppedEvent(reason, 'span', 1 + (event.spans || []).length);
 }
 };

 return this._prepareEvent(event, hint, currentScope, isolationScope)
 .then(prepared => {
 if (prepared === null) {
Expand All@@ -1539,13 +1547,7 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 })
 .then(processedEvent => {
 if (processedEvent === null) {
 this.recordDroppedEvent('before_send', dataCategory);
 if (isTransaction) {
 const spans = event.spans || [];
 // the transaction itself counts as one span, plus all the child spans that are added
 const spanCount = 1 + spans.length;
 this.recordDroppedEvent('before_send', 'span', spanCount);
 }
 recordDroppedEvent('before_send');
 throw _makeDoNotSendEventError(`${beforeSendLabel} returned \`null\`, will not send event.`);
 }

Expand DownExpand Up@@ -1587,6 +1589,11 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 return processedEvent;
 })
 .then(null, reason => {
 if (reason === CALLBACK_ERROR) {
 recordDroppedEvent('callback_error');
 throw _makeDoNotSendEventError('A user callback threw an error, will not send event.');
 }

 if (_isDoNotSendEventError(reason) || _isInternalError(reason)) {
 throw reason;
 }
Expand DownExpand Up@@ -1702,17 +1709,13 @@ function _validateBeforeSendResult(
): PromiseLike<Event | null> | Event | null {
 const invalidValueError = `${beforeSendLabel} must return \`null\` or a valid event.`;
 if (isThenable(beforeSendResult)) {
 return beforeSendResult.then(
 event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 },
 e => {
 throw _makeInternalError(`${beforeSendLabel} rejected with ${e}`);
 },
 );
 // A rejection can only be `CALLBACK_ERROR` here, as `safeCallback` already handled the user callback rejecting
 return beforeSendResult.then(event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 });
 } else if (!isPlainObject(beforeSendResult) && beforeSendResult !== null) {
 throw _makeInternalError(invalidValueError);
 }
Expand DownExpand Up@@ -1743,7 +1746,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSend` callback threw an error, dropping the event:' : '',
 () => beforeSend(errorEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }

Expand DownExpand Up@@ -1818,7 +1823,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSendTransaction` callback threw an error, dropping the event:' : '',
 () => beforeSendTransaction(processedEvent as TransactionEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }
 }
Expand Down

7 changes: 5 additions & 2 deletions
packages/core/src/eventProcessors.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -3,11 +3,12 @@ import type { Event, EventHint } from './types/event';
import type { EventProcessor } from './types/eventprocessor';
import { debug } from './utils/debug-logger';
import { isThenable } from './utils/is';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { rejectedSyncPromise, resolvedSyncPromise } from './utils/syncpromise';

/**
 * Process an array of event processors, returning the processed event (or `null` if the event was dropped).
 * Rejects with `CALLBACK_ERROR` if a processor throws.
 */
export function notifyEventProcessors(
 processors: EventProcessor[],
Expand DownExpand Up@@ -40,7 +41,9 @@ function _notifyEventProcessors(
 const result = safeCallback(
 DEBUG_BUILD ? `${processorName} threw an error, dropping event:` : '',
 () => processor({ ...event }, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
@Lms24Lms24Sep 3, 2026•

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m: throwing here and in client.ts made me a bit suspicious because we have to be really careful to also catch our throws. Looks like there's a case in replay where we also call prepareEvent which doesn't try/catch the call. I think this only concerns event processor throws though. This leads to us trying to re-send the replay because we assume a network error. Ultimately, we stop recording.
I think we have two options how to avoid this:
  1. we try/catch in Replay so that this doesn't happen
  2. we don't throw at all. Instead, we could directly record an dropped event in notifyEventProcessors and distinguish there.
Tbqh: I haven't thought this through end-to-end, so maybe 1 is easier. I don't see us reusing prepareEvent much in the foreseeable future. But happy to let you make the call (also feel free to come up with something else).
 },
 );

 DEBUG_BUILD && result === null && debug.log(`${processorName} dropped event`);
Expand Down

10 changes: 7 additions & 3 deletions
packages/core/src/logs/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Log, SerializedLog } from '../types/log';
import { consoleSandbox, debug } from '../utils/debug-logger';
import { isParameterizedString } from '../utils/is';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -144,13 +144,17 @@ export function _INTERNAL_captureLog(
 client.emit('beforeCaptureLog', processedLog);

 const log = beforeSendLog
 ? safeCallback(
 ? safeCallback<Log | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendLog` callback threw an error, dropping the log:' : '',
 // We need to wrap this in `consoleSandbox` to avoid recursive calls to `beforeSendLog`
 () => consoleSandbox(() => beforeSendLog(processedLog)),
 () => null,
 () => CALLBACK_ERROR,
 )
 : processedLog;
 if (log === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'log_item', 1);
 return;
 }
 if (!log) {
 client.recordDroppedEvent('before_send', 'log_item', 1);
 DEBUG_BUILD && debug.warn('beforeSendLog returned null, log will not be captured.');
Expand Down

11 changes: 8 additions & 3 deletions
packages/core/src/metrics/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Metric, SerializedMetric } from '../types/metric';
import type { User } from '../types/user';
import { debug } from '../utils/debug-logger';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -183,13 +183,18 @@ export function _INTERNAL_captureMetric(beforeMetric: Metric, options?: Internal
 client.emit('processMetric', enrichedMetric);

 const processedMetric = beforeSendMetric
 ? safeCallback(
 ? safeCallback<Metric | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendMetric` callback threw an error, dropping the metric:' : '',
 () => beforeSendMetric(enrichedMetric),
 () => null,
 () => CALLBACK_ERROR,
 )
 : enrichedMetric;

 if (processedMetric === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'metric', 1);
 return;
 }

 if (!processedMetric) {
 client.recordDroppedEvent('before_send', 'metric', 1);
 DEBUG_BUILD && debug.log('`beforeSendMetric` returned `null`, will not send metric.');
Expand Down

22 changes: 16 additions & 6 deletions
packages/core/src/tracing/sampling.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -6,6 +6,14 @@ import { hasSpansEnabled } from '../utils/hasSpansEnabled';
import { parseSampleRate } from '../utils/parseSampleRate';
import { safeCallback } from '../utils/safeCallback';

interface SamplingDecision {
 sampled: boolean;
 sampleRate?: number;
 localSampleRateWasApplied?: boolean;
 /** Set when the span was dropped for a reason other than the sampling decision itself. */
 dropReason?: 'callback_error';
}

/**
 * Makes a sampling decision for the given options.
 *
Expand All@@ -16,15 +24,17 @@ export function sampleSpan(
 options: Pick<CoreOptions, 'tracesSampleRate' | 'tracesSampler'>,
 samplingContext: SamplingContext,
 sampleRand: number,
): [sampled: boolean, sampleRate?: number, localSampleRateWasApplied?: boolean] {
): SamplingDecision {
@Lms24Lms24Sep 3, 2026

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m: this is API breaking, since sampleSpan is exported. I agree that the object is easier to read though . IIRC, we used the named tuple here for bundle size minimization but this is less readable than the refactor.
Breaking here isn't a big deal though, so we can also do it if the tuple no longer works. But if we do, let's add a note in the migration guide.
 // nothing to do if span recording is not enabled
 if (!hasSpansEnabled(options)) {
 return [false];
 return { sampled: false };
 }

 const resolved = resolveSampleRate(options, samplingContext);
 if (!resolved) {
 return [false];
 // `hasSpansEnabled` guarantees either `tracesSampleRate` or `tracesSampler` is set, so the only way to end up
 // without a sample rate is a throwing `tracesSampler` with nothing to fall back to.
 return { sampled: false, dropReason: 'callback_error' };
 }
 const [sampleRate, localSampleRateWasApplied] = resolved;

Expand All@@ -39,7 +49,7 @@ export function sampleSpan(
 sampleRate,
 )} of type ${JSON.stringify(typeof sampleRate)}.`,
 );
 return [false];
 return { sampled: false };
 }

 // if the function returned 0 (or false), or if `tracesSampleRate` is 0, it's a sign the transaction should be dropped
Expand All@@ -52,7 +62,7 @@ export function sampleSpan(
 : 'a negative sampling decision was inherited or tracesSampleRate is set to 0'
 }`,
 );
 return [false, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: false, sampleRate: parsedSampleRate, localSampleRateWasApplied };
 }

 // We always compare the sample rand for the current execution context against the chosen sample rate.
Expand All@@ -69,7 +79,7 @@ export function sampleSpan(
 );
 }

 return [shouldSample, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: shouldSample, sampleRate: parsedSampleRate, localSampleRateWasApplied };
}

/**
Expand Down

6 changes: 3 additions & 3 deletions
packages/core/src/tracing/trace.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -495,8 +495,8 @@ function _startRootSpan(
 const currentPropagationContext = scope.getPropagationContext();
 const _isTracingSuppressed = isTracingSuppressed(scope);

 const [sampled, sampleRate, localSampleRateWasApplied] = _isTracingSuppressed
 ? [false]
 const { sampled, sampleRate, localSampleRateWasApplied, dropReason } = _isTracingSuppressed
 ? { sampled: false }
 : sampleSpan(
 options,
 {
Expand All@@ -522,7 +522,7 @@ function _startRootSpan(

 if (!sampled && client && !_isTracingSuppressed) {
 DEBUG_BUILD && debug.log('[Tracing] Discarding root span because its trace was not chosen to be sampled.');
 client.recordDroppedEvent('sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 client.recordDroppedEvent(dropReason || 'sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 }

 setCapturedScopesOnSpan(rootSpan, scope, isolationScope);
Expand Down

1 change: 1 addition & 0 deletions
packages/core/src/types/clientreport.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,7 @@ import type { DataCategory } from './datacategory';

export type EventDropReason =
 | 'before_send'
 | 'callback_error'
 | 'event_processor'
 | 'network_error'
 | 'queue_overflow'
Expand Down

7 changes: 7 additions & 0 deletions
packages/core/src/utils/safeCallback.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,13 @@ import { DEBUG_BUILD } from '../debug-build';
import { debug } from './debug-logger';
import { isThenable } from './is';

/**
 * Lets a `safeCallback` fallback signal "the callback failed" as opposed to "the callback returned `null`",
 * so the call site can report the drop as `callback_error`. Return it from synchronous call sites; throw it
 * to abort a promise chain.
 */
export const CALLBACK_ERROR = Symbol.for('SentryCallbackError');

/**
 * Invokes a user-provided callback (e.g. `beforeSend`, `tracesSampler`, an integration hook) so that
 * neither a synchronous throw nor a rejected promise escapes into the caller. On failure the error is
Expand Down

16 changes: 8 additions & 8 deletions
packages/core/test/lib/client.test.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -2222,7 +2222,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand All@@ -2244,7 +2244,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand DownExpand Up@@ -2277,7 +2277,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('a rejecting event processor stops the processor chain', async () => {
Expand DownExpand Up@@ -2312,7 +2312,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('client-level event processor that throws on all events does not capture a new event', () => {
Expand DownExpand Up@@ -2348,7 +2348,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledTimes(1);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
Expand All@@ -2373,7 +2373,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
 exception,
Expand DownExpand Up@@ -2416,8 +2416,8 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'span', 3);
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'span', 3);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSendTransaction` callback threw an error, dropping the event:',
 exception,
Expand Down
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injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
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feat(core): Record callback_error client reports for throwing user callbacks#23903

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feat(core): Record callback_error client reports for throwing user callbacks
#23903
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2 changes: 1 addition & 1 deletion
...ages/node-integration-tests/suites/client-reports/drop-reasons/before-send-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when beforeSend throws',
 {
 category: 'error',
 quantity: 1,
 reason: 'before_send',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

4 changes: 2 additions & 2 deletions
.../node-integration-tests/suites/client-reports/drop-reasons/event-processor-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when an event processor t
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand All@@ -32,7 +32,7 @@ test('records a client report and no extra error event when an async event proce
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

2 changes: 1 addition & 1 deletion
...s/node-integration-tests/suites/client-reports/drop-reasons/traces-sampler-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no error event when tracesSampler throws', asy
 {
 category: 'span',
 quantity: 1,
 reason: 'sample_rate',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

49 changes: 28 additions & 21 deletions
packages/core/src/client.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,7 @@ import { parseSampleRate } from './utils/parseSampleRate';
import { prepareEvent } from './utils/prepareEvent';
import { makePromiseBuffer, type PromiseBuffer, SENTRY_BUFFER_FULL_ERROR } from './utils/promisebuffer';
import { safeMathRandom } from './utils/randomSafeContext';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { reparentChildSpans, shouldIgnoreSpan } from './utils/should-ignore-span';
import { safeUnref } from './utils/timer';
import { convertSpanJsonToTransactionEvent, convertTransactionEventToSpanJson } from './utils/transactionEvent';
Expand DownExpand Up@@ -1522,6 +1522,14 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 const parsedSampleRate = typeof sampleRate === 'undefined' ? undefined : parseSampleRate(sampleRate);
 const dataCategory = getDataCategoryByType(event.type);

 const recordDroppedEvent = (reason: EventDropReason): void => {
 this.recordDroppedEvent(reason, dataCategory);
 if (isTransaction) {
 // the transaction itself counts as one span, plus all the child spans that are added
 this.recordDroppedEvent(reason, 'span', 1 + (event.spans || []).length);
 }
 };

 return this._prepareEvent(event, hint, currentScope, isolationScope)
 .then(prepared => {
 if (prepared === null) {
Expand All@@ -1539,13 +1547,7 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 })
 .then(processedEvent => {
 if (processedEvent === null) {
 this.recordDroppedEvent('before_send', dataCategory);
 if (isTransaction) {
 const spans = event.spans || [];
 // the transaction itself counts as one span, plus all the child spans that are added
 const spanCount = 1 + spans.length;
 this.recordDroppedEvent('before_send', 'span', spanCount);
 }
 recordDroppedEvent('before_send');
 throw _makeDoNotSendEventError(`${beforeSendLabel} returned \`null\`, will not send event.`);
 }

Expand DownExpand Up@@ -1587,6 +1589,11 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 return processedEvent;
 })
 .then(null, reason => {
 if (reason === CALLBACK_ERROR) {
 recordDroppedEvent('callback_error');
 throw _makeDoNotSendEventError('A user callback threw an error, will not send event.');
 }

 if (_isDoNotSendEventError(reason) || _isInternalError(reason)) {
 throw reason;
 }
Expand DownExpand Up@@ -1702,17 +1709,13 @@ function _validateBeforeSendResult(
): PromiseLike<Event | null> | Event | null {
 const invalidValueError = `${beforeSendLabel} must return \`null\` or a valid event.`;
 if (isThenable(beforeSendResult)) {
 return beforeSendResult.then(
 event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 },
 e => {
 throw _makeInternalError(`${beforeSendLabel} rejected with ${e}`);
 },
 );
 // A rejection can only be `CALLBACK_ERROR` here, as `safeCallback` already handled the user callback rejecting
 return beforeSendResult.then(event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 });
 } else if (!isPlainObject(beforeSendResult) && beforeSendResult !== null) {
 throw _makeInternalError(invalidValueError);
 }
Expand DownExpand Up@@ -1743,7 +1746,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSend` callback threw an error, dropping the event:' : '',
 () => beforeSend(errorEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }

Expand DownExpand Up@@ -1818,7 +1823,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSendTransaction` callback threw an error, dropping the event:' : '',
 () => beforeSendTransaction(processedEvent as TransactionEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }
 }
Expand Down

7 changes: 5 additions & 2 deletions
packages/core/src/eventProcessors.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -3,11 +3,12 @@ import type { Event, EventHint } from './types/event';
import type { EventProcessor } from './types/eventprocessor';
import { debug } from './utils/debug-logger';
import { isThenable } from './utils/is';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { rejectedSyncPromise, resolvedSyncPromise } from './utils/syncpromise';

/**
 * Process an array of event processors, returning the processed event (or `null` if the event was dropped).
 * Rejects with `CALLBACK_ERROR` if a processor throws.
 */
export function notifyEventProcessors(
 processors: EventProcessor[],
Expand DownExpand Up@@ -40,7 +41,9 @@ function _notifyEventProcessors(
 const result = safeCallback(
 DEBUG_BUILD ? `${processorName} threw an error, dropping event:` : '',
 () => processor({ ...event }, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
@Lms24Lms24Sep 3, 2026•

edited

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m: throwing here and in client.ts made me a bit suspicious because we have to be really careful to also catch our throws. Looks like there's a case in replay where we also call prepareEvent which doesn't try/catch the call. I think this only concerns event processor throws though. This leads to us trying to re-send the replay because we assume a network error. Ultimately, we stop recording.
I think we have two options how to avoid this:
  1. we try/catch in Replay so that this doesn't happen
  2. we don't throw at all. Instead, we could directly record an dropped event in notifyEventProcessors and distinguish there.
Tbqh: I haven't thought this through end-to-end, so maybe 1 is easier. I don't see us reusing prepareEvent much in the foreseeable future. But happy to let you make the call (also feel free to come up with something else).
 },
 );

 DEBUG_BUILD && result === null && debug.log(`${processorName} dropped event`);
Expand Down

10 changes: 7 additions & 3 deletions
packages/core/src/logs/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Log, SerializedLog } from '../types/log';
import { consoleSandbox, debug } from '../utils/debug-logger';
import { isParameterizedString } from '../utils/is';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -144,13 +144,17 @@ export function _INTERNAL_captureLog(
 client.emit('beforeCaptureLog', processedLog);

 const log = beforeSendLog
 ? safeCallback(
 ? safeCallback<Log | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendLog` callback threw an error, dropping the log:' : '',
 // We need to wrap this in `consoleSandbox` to avoid recursive calls to `beforeSendLog`
 () => consoleSandbox(() => beforeSendLog(processedLog)),
 () => null,
 () => CALLBACK_ERROR,
 )
 : processedLog;
 if (log === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'log_item', 1);
 return;
 }
 if (!log) {
 client.recordDroppedEvent('before_send', 'log_item', 1);
 DEBUG_BUILD && debug.warn('beforeSendLog returned null, log will not be captured.');
Expand Down

11 changes: 8 additions & 3 deletions
packages/core/src/metrics/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Metric, SerializedMetric } from '../types/metric';
import type { User } from '../types/user';
import { debug } from '../utils/debug-logger';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -183,13 +183,18 @@ export function _INTERNAL_captureMetric(beforeMetric: Metric, options?: Internal
 client.emit('processMetric', enrichedMetric);

 const processedMetric = beforeSendMetric
 ? safeCallback(
 ? safeCallback<Metric | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendMetric` callback threw an error, dropping the metric:' : '',
 () => beforeSendMetric(enrichedMetric),
 () => null,
 () => CALLBACK_ERROR,
 )
 : enrichedMetric;

 if (processedMetric === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'metric', 1);
 return;
 }

 if (!processedMetric) {
 client.recordDroppedEvent('before_send', 'metric', 1);
 DEBUG_BUILD && debug.log('`beforeSendMetric` returned `null`, will not send metric.');
Expand Down

22 changes: 16 additions & 6 deletions
packages/core/src/tracing/sampling.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -6,6 +6,14 @@ import { hasSpansEnabled } from '../utils/hasSpansEnabled';
import { parseSampleRate } from '../utils/parseSampleRate';
import { safeCallback } from '../utils/safeCallback';

interface SamplingDecision {
 sampled: boolean;
 sampleRate?: number;
 localSampleRateWasApplied?: boolean;
 /** Set when the span was dropped for a reason other than the sampling decision itself. */
 dropReason?: 'callback_error';
}

/**
 * Makes a sampling decision for the given options.
 *
Expand All@@ -16,15 +24,17 @@ export function sampleSpan(
 options: Pick<CoreOptions, 'tracesSampleRate' | 'tracesSampler'>,
 samplingContext: SamplingContext,
 sampleRand: number,
): [sampled: boolean, sampleRate?: number, localSampleRateWasApplied?: boolean] {
): SamplingDecision {
@Lms24Lms24Sep 3, 2026

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m: this is API breaking, since sampleSpan is exported. I agree that the object is easier to read though . IIRC, we used the named tuple here for bundle size minimization but this is less readable than the refactor.
Breaking here isn't a big deal though, so we can also do it if the tuple no longer works. But if we do, let's add a note in the migration guide.
 // nothing to do if span recording is not enabled
 if (!hasSpansEnabled(options)) {
 return [false];
 return { sampled: false };
 }

 const resolved = resolveSampleRate(options, samplingContext);
 if (!resolved) {
 return [false];
 // `hasSpansEnabled` guarantees either `tracesSampleRate` or `tracesSampler` is set, so the only way to end up
 // without a sample rate is a throwing `tracesSampler` with nothing to fall back to.
 return { sampled: false, dropReason: 'callback_error' };
 }
 const [sampleRate, localSampleRateWasApplied] = resolved;

Expand All@@ -39,7 +49,7 @@ export function sampleSpan(
 sampleRate,
 )} of type ${JSON.stringify(typeof sampleRate)}.`,
 );
 return [false];
 return { sampled: false };
 }

 // if the function returned 0 (or false), or if `tracesSampleRate` is 0, it's a sign the transaction should be dropped
Expand All@@ -52,7 +62,7 @@ export function sampleSpan(
 : 'a negative sampling decision was inherited or tracesSampleRate is set to 0'
 }`,
 );
 return [false, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: false, sampleRate: parsedSampleRate, localSampleRateWasApplied };
 }

 // We always compare the sample rand for the current execution context against the chosen sample rate.
Expand All@@ -69,7 +79,7 @@ export function sampleSpan(
 );
 }

 return [shouldSample, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: shouldSample, sampleRate: parsedSampleRate, localSampleRateWasApplied };
}

/**
Expand Down

6 changes: 3 additions & 3 deletions
packages/core/src/tracing/trace.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -495,8 +495,8 @@ function _startRootSpan(
 const currentPropagationContext = scope.getPropagationContext();
 const _isTracingSuppressed = isTracingSuppressed(scope);

 const [sampled, sampleRate, localSampleRateWasApplied] = _isTracingSuppressed
 ? [false]
 const { sampled, sampleRate, localSampleRateWasApplied, dropReason } = _isTracingSuppressed
 ? { sampled: false }
 : sampleSpan(
 options,
 {
Expand All@@ -522,7 +522,7 @@ function _startRootSpan(

 if (!sampled && client && !_isTracingSuppressed) {
 DEBUG_BUILD && debug.log('[Tracing] Discarding root span because its trace was not chosen to be sampled.');
 client.recordDroppedEvent('sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 client.recordDroppedEvent(dropReason || 'sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 }

 setCapturedScopesOnSpan(rootSpan, scope, isolationScope);
Expand Down

1 change: 1 addition & 0 deletions
packages/core/src/types/clientreport.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,7 @@ import type { DataCategory } from './datacategory';

export type EventDropReason =
 | 'before_send'
 | 'callback_error'
 | 'event_processor'
 | 'network_error'
 | 'queue_overflow'
Expand Down

7 changes: 7 additions & 0 deletions
packages/core/src/utils/safeCallback.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,13 @@ import { DEBUG_BUILD } from '../debug-build';
import { debug } from './debug-logger';
import { isThenable } from './is';

/**
 * Lets a `safeCallback` fallback signal "the callback failed" as opposed to "the callback returned `null`",
 * so the call site can report the drop as `callback_error`. Return it from synchronous call sites; throw it
 * to abort a promise chain.
 */
export const CALLBACK_ERROR = Symbol.for('SentryCallbackError');

/**
 * Invokes a user-provided callback (e.g. `beforeSend`, `tracesSampler`, an integration hook) so that
 * neither a synchronous throw nor a rejected promise escapes into the caller. On failure the error is
Expand Down

16 changes: 8 additions & 8 deletions
packages/core/test/lib/client.test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2222,7 +2222,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand All@@ -2244,7 +2244,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand DownExpand Up@@ -2277,7 +2277,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('a rejecting event processor stops the processor chain', async () => {
Expand DownExpand Up@@ -2312,7 +2312,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('client-level event processor that throws on all events does not capture a new event', () => {
Expand DownExpand Up@@ -2348,7 +2348,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledTimes(1);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
Expand All@@ -2373,7 +2373,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
 exception,
Expand DownExpand Up@@ -2416,8 +2416,8 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'span', 3);
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'span', 3);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSendTransaction` callback threw an error, dropping the event:',
 exception,
Expand Down
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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feat(core): Record callback_error client reports for throwing user callbacks#23903

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feat(core): Record callback_error client reports for throwing user callbacks
#23903
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2 changes: 1 addition & 1 deletion
...ages/node-integration-tests/suites/client-reports/drop-reasons/before-send-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when beforeSend throws',
 {
 category: 'error',
 quantity: 1,
 reason: 'before_send',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

4 changes: 2 additions & 2 deletions
.../node-integration-tests/suites/client-reports/drop-reasons/event-processor-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when an event processor t
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand All@@ -32,7 +32,7 @@ test('records a client report and no extra error event when an async event proce
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

2 changes: 1 addition & 1 deletion
...s/node-integration-tests/suites/client-reports/drop-reasons/traces-sampler-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no error event when tracesSampler throws', asy
 {
 category: 'span',
 quantity: 1,
 reason: 'sample_rate',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

49 changes: 28 additions & 21 deletions
packages/core/src/client.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,7 @@ import { parseSampleRate } from './utils/parseSampleRate';
import { prepareEvent } from './utils/prepareEvent';
import { makePromiseBuffer, type PromiseBuffer, SENTRY_BUFFER_FULL_ERROR } from './utils/promisebuffer';
import { safeMathRandom } from './utils/randomSafeContext';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { reparentChildSpans, shouldIgnoreSpan } from './utils/should-ignore-span';
import { safeUnref } from './utils/timer';
import { convertSpanJsonToTransactionEvent, convertTransactionEventToSpanJson } from './utils/transactionEvent';
Expand DownExpand Up@@ -1522,6 +1522,14 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 const parsedSampleRate = typeof sampleRate === 'undefined' ? undefined : parseSampleRate(sampleRate);
 const dataCategory = getDataCategoryByType(event.type);

 const recordDroppedEvent = (reason: EventDropReason): void => {
 this.recordDroppedEvent(reason, dataCategory);
 if (isTransaction) {
 // the transaction itself counts as one span, plus all the child spans that are added
 this.recordDroppedEvent(reason, 'span', 1 + (event.spans || []).length);
 }
 };

 return this._prepareEvent(event, hint, currentScope, isolationScope)
 .then(prepared => {
 if (prepared === null) {
Expand All@@ -1539,13 +1547,7 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 })
 .then(processedEvent => {
 if (processedEvent === null) {
 this.recordDroppedEvent('before_send', dataCategory);
 if (isTransaction) {
 const spans = event.spans || [];
 // the transaction itself counts as one span, plus all the child spans that are added
 const spanCount = 1 + spans.length;
 this.recordDroppedEvent('before_send', 'span', spanCount);
 }
 recordDroppedEvent('before_send');
 throw _makeDoNotSendEventError(`${beforeSendLabel} returned \`null\`, will not send event.`);
 }

Expand DownExpand Up@@ -1587,6 +1589,11 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 return processedEvent;
 })
 .then(null, reason => {
 if (reason === CALLBACK_ERROR) {
 recordDroppedEvent('callback_error');
 throw _makeDoNotSendEventError('A user callback threw an error, will not send event.');
 }

 if (_isDoNotSendEventError(reason) || _isInternalError(reason)) {
 throw reason;
 }
Expand DownExpand Up@@ -1702,17 +1709,13 @@ function _validateBeforeSendResult(
): PromiseLike<Event | null> | Event | null {
 const invalidValueError = `${beforeSendLabel} must return \`null\` or a valid event.`;
 if (isThenable(beforeSendResult)) {
 return beforeSendResult.then(
 event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 },
 e => {
 throw _makeInternalError(`${beforeSendLabel} rejected with ${e}`);
 },
 );
 // A rejection can only be `CALLBACK_ERROR` here, as `safeCallback` already handled the user callback rejecting
 return beforeSendResult.then(event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 });
 } else if (!isPlainObject(beforeSendResult) && beforeSendResult !== null) {
 throw _makeInternalError(invalidValueError);
 }
Expand DownExpand Up@@ -1743,7 +1746,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSend` callback threw an error, dropping the event:' : '',
 () => beforeSend(errorEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }

Expand DownExpand Up@@ -1818,7 +1823,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSendTransaction` callback threw an error, dropping the event:' : '',
 () => beforeSendTransaction(processedEvent as TransactionEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }
 }
Expand Down

7 changes: 5 additions & 2 deletions
packages/core/src/eventProcessors.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -3,11 +3,12 @@ import type { Event, EventHint } from './types/event';
import type { EventProcessor } from './types/eventprocessor';
import { debug } from './utils/debug-logger';
import { isThenable } from './utils/is';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { rejectedSyncPromise, resolvedSyncPromise } from './utils/syncpromise';

/**
 * Process an array of event processors, returning the processed event (or `null` if the event was dropped).
 * Rejects with `CALLBACK_ERROR` if a processor throws.
 */
export function notifyEventProcessors(
 processors: EventProcessor[],
Expand DownExpand Up@@ -40,7 +41,9 @@ function _notifyEventProcessors(
 const result = safeCallback(
 DEBUG_BUILD ? `${processorName} threw an error, dropping event:` : '',
 () => processor({ ...event }, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
@Lms24Lms24Sep 3, 2026•

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m: throwing here and in client.ts made me a bit suspicious because we have to be really careful to also catch our throws. Looks like there's a case in replay where we also call prepareEvent which doesn't try/catch the call. I think this only concerns event processor throws though. This leads to us trying to re-send the replay because we assume a network error. Ultimately, we stop recording.
I think we have two options how to avoid this:
  1. we try/catch in Replay so that this doesn't happen
  2. we don't throw at all. Instead, we could directly record an dropped event in notifyEventProcessors and distinguish there.
Tbqh: I haven't thought this through end-to-end, so maybe 1 is easier. I don't see us reusing prepareEvent much in the foreseeable future. But happy to let you make the call (also feel free to come up with something else).
 },
 );

 DEBUG_BUILD && result === null && debug.log(`${processorName} dropped event`);
Expand Down

10 changes: 7 additions & 3 deletions
packages/core/src/logs/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Log, SerializedLog } from '../types/log';
import { consoleSandbox, debug } from '../utils/debug-logger';
import { isParameterizedString } from '../utils/is';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -144,13 +144,17 @@ export function _INTERNAL_captureLog(
 client.emit('beforeCaptureLog', processedLog);

 const log = beforeSendLog
 ? safeCallback(
 ? safeCallback<Log | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendLog` callback threw an error, dropping the log:' : '',
 // We need to wrap this in `consoleSandbox` to avoid recursive calls to `beforeSendLog`
 () => consoleSandbox(() => beforeSendLog(processedLog)),
 () => null,
 () => CALLBACK_ERROR,
 )
 : processedLog;
 if (log === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'log_item', 1);
 return;
 }
 if (!log) {
 client.recordDroppedEvent('before_send', 'log_item', 1);
 DEBUG_BUILD && debug.warn('beforeSendLog returned null, log will not be captured.');
Expand Down

11 changes: 8 additions & 3 deletions
packages/core/src/metrics/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Metric, SerializedMetric } from '../types/metric';
import type { User } from '../types/user';
import { debug } from '../utils/debug-logger';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -183,13 +183,18 @@ export function _INTERNAL_captureMetric(beforeMetric: Metric, options?: Internal
 client.emit('processMetric', enrichedMetric);

 const processedMetric = beforeSendMetric
 ? safeCallback(
 ? safeCallback<Metric | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendMetric` callback threw an error, dropping the metric:' : '',
 () => beforeSendMetric(enrichedMetric),
 () => null,
 () => CALLBACK_ERROR,
 )
 : enrichedMetric;

 if (processedMetric === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'metric', 1);
 return;
 }

 if (!processedMetric) {
 client.recordDroppedEvent('before_send', 'metric', 1);
 DEBUG_BUILD && debug.log('`beforeSendMetric` returned `null`, will not send metric.');
Expand Down

22 changes: 16 additions & 6 deletions
packages/core/src/tracing/sampling.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -6,6 +6,14 @@ import { hasSpansEnabled } from '../utils/hasSpansEnabled';
import { parseSampleRate } from '../utils/parseSampleRate';
import { safeCallback } from '../utils/safeCallback';

interface SamplingDecision {
 sampled: boolean;
 sampleRate?: number;
 localSampleRateWasApplied?: boolean;
 /** Set when the span was dropped for a reason other than the sampling decision itself. */
 dropReason?: 'callback_error';
}

/**
 * Makes a sampling decision for the given options.
 *
Expand All@@ -16,15 +24,17 @@ export function sampleSpan(
 options: Pick<CoreOptions, 'tracesSampleRate' | 'tracesSampler'>,
 samplingContext: SamplingContext,
 sampleRand: number,
): [sampled: boolean, sampleRate?: number, localSampleRateWasApplied?: boolean] {
): SamplingDecision {
@Lms24Lms24Sep 3, 2026

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m: this is API breaking, since sampleSpan is exported. I agree that the object is easier to read though . IIRC, we used the named tuple here for bundle size minimization but this is less readable than the refactor.
Breaking here isn't a big deal though, so we can also do it if the tuple no longer works. But if we do, let's add a note in the migration guide.
 // nothing to do if span recording is not enabled
 if (!hasSpansEnabled(options)) {
 return [false];
 return { sampled: false };
 }

 const resolved = resolveSampleRate(options, samplingContext);
 if (!resolved) {
 return [false];
 // `hasSpansEnabled` guarantees either `tracesSampleRate` or `tracesSampler` is set, so the only way to end up
 // without a sample rate is a throwing `tracesSampler` with nothing to fall back to.
 return { sampled: false, dropReason: 'callback_error' };
 }
 const [sampleRate, localSampleRateWasApplied] = resolved;

Expand All@@ -39,7 +49,7 @@ export function sampleSpan(
 sampleRate,
 )} of type ${JSON.stringify(typeof sampleRate)}.`,
 );
 return [false];
 return { sampled: false };
 }

 // if the function returned 0 (or false), or if `tracesSampleRate` is 0, it's a sign the transaction should be dropped
Expand All@@ -52,7 +62,7 @@ export function sampleSpan(
 : 'a negative sampling decision was inherited or tracesSampleRate is set to 0'
 }`,
 );
 return [false, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: false, sampleRate: parsedSampleRate, localSampleRateWasApplied };
 }

 // We always compare the sample rand for the current execution context against the chosen sample rate.
Expand All@@ -69,7 +79,7 @@ export function sampleSpan(
 );
 }

 return [shouldSample, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: shouldSample, sampleRate: parsedSampleRate, localSampleRateWasApplied };
}

/**
Expand Down

6 changes: 3 additions & 3 deletions
packages/core/src/tracing/trace.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -495,8 +495,8 @@ function _startRootSpan(
 const currentPropagationContext = scope.getPropagationContext();
 const _isTracingSuppressed = isTracingSuppressed(scope);

 const [sampled, sampleRate, localSampleRateWasApplied] = _isTracingSuppressed
 ? [false]
 const { sampled, sampleRate, localSampleRateWasApplied, dropReason } = _isTracingSuppressed
 ? { sampled: false }
 : sampleSpan(
 options,
 {
Expand All@@ -522,7 +522,7 @@ function _startRootSpan(

 if (!sampled && client && !_isTracingSuppressed) {
 DEBUG_BUILD && debug.log('[Tracing] Discarding root span because its trace was not chosen to be sampled.');
 client.recordDroppedEvent('sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 client.recordDroppedEvent(dropReason || 'sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 }

 setCapturedScopesOnSpan(rootSpan, scope, isolationScope);
Expand Down

1 change: 1 addition & 0 deletions
packages/core/src/types/clientreport.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,7 @@ import type { DataCategory } from './datacategory';

export type EventDropReason =
 | 'before_send'
 | 'callback_error'
 | 'event_processor'
 | 'network_error'
 | 'queue_overflow'
Expand Down

7 changes: 7 additions & 0 deletions
packages/core/src/utils/safeCallback.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,13 @@ import { DEBUG_BUILD } from '../debug-build';
import { debug } from './debug-logger';
import { isThenable } from './is';

/**
 * Lets a `safeCallback` fallback signal "the callback failed" as opposed to "the callback returned `null`",
 * so the call site can report the drop as `callback_error`. Return it from synchronous call sites; throw it
 * to abort a promise chain.
 */
export const CALLBACK_ERROR = Symbol.for('SentryCallbackError');

/**
 * Invokes a user-provided callback (e.g. `beforeSend`, `tracesSampler`, an integration hook) so that
 * neither a synchronous throw nor a rejected promise escapes into the caller. On failure the error is
Expand Down

16 changes: 8 additions & 8 deletions
packages/core/test/lib/client.test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2222,7 +2222,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand All@@ -2244,7 +2244,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand DownExpand Up@@ -2277,7 +2277,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('a rejecting event processor stops the processor chain', async () => {
Expand DownExpand Up@@ -2312,7 +2312,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('client-level event processor that throws on all events does not capture a new event', () => {
Expand DownExpand Up@@ -2348,7 +2348,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledTimes(1);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
Expand All@@ -2373,7 +2373,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
 exception,
Expand DownExpand Up@@ -2416,8 +2416,8 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'span', 3);
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'span', 3);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSendTransaction` callback threw an error, dropping the event:',
 exception,
Expand Down
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

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feat(core): Record callback_error client reports for throwing user callbacks#23903

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feat(core): Record callback_error client reports for throwing user callbacks
#23903
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2 changes: 1 addition & 1 deletion
...ages/node-integration-tests/suites/client-reports/drop-reasons/before-send-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when beforeSend throws',
 {
 category: 'error',
 quantity: 1,
 reason: 'before_send',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

4 changes: 2 additions & 2 deletions
.../node-integration-tests/suites/client-reports/drop-reasons/event-processor-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when an event processor t
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand All@@ -32,7 +32,7 @@ test('records a client report and no extra error event when an async event proce
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

2 changes: 1 addition & 1 deletion
...s/node-integration-tests/suites/client-reports/drop-reasons/traces-sampler-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no error event when tracesSampler throws', asy
 {
 category: 'span',
 quantity: 1,
 reason: 'sample_rate',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

49 changes: 28 additions & 21 deletions
packages/core/src/client.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,7 @@ import { parseSampleRate } from './utils/parseSampleRate';
import { prepareEvent } from './utils/prepareEvent';
import { makePromiseBuffer, type PromiseBuffer, SENTRY_BUFFER_FULL_ERROR } from './utils/promisebuffer';
import { safeMathRandom } from './utils/randomSafeContext';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { reparentChildSpans, shouldIgnoreSpan } from './utils/should-ignore-span';
import { safeUnref } from './utils/timer';
import { convertSpanJsonToTransactionEvent, convertTransactionEventToSpanJson } from './utils/transactionEvent';
Expand DownExpand Up@@ -1522,6 +1522,14 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 const parsedSampleRate = typeof sampleRate === 'undefined' ? undefined : parseSampleRate(sampleRate);
 const dataCategory = getDataCategoryByType(event.type);

 const recordDroppedEvent = (reason: EventDropReason): void => {
 this.recordDroppedEvent(reason, dataCategory);
 if (isTransaction) {
 // the transaction itself counts as one span, plus all the child spans that are added
 this.recordDroppedEvent(reason, 'span', 1 + (event.spans || []).length);
 }
 };

 return this._prepareEvent(event, hint, currentScope, isolationScope)
 .then(prepared => {
 if (prepared === null) {
Expand All@@ -1539,13 +1547,7 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 })
 .then(processedEvent => {
 if (processedEvent === null) {
 this.recordDroppedEvent('before_send', dataCategory);
 if (isTransaction) {
 const spans = event.spans || [];
 // the transaction itself counts as one span, plus all the child spans that are added
 const spanCount = 1 + spans.length;
 this.recordDroppedEvent('before_send', 'span', spanCount);
 }
 recordDroppedEvent('before_send');
 throw _makeDoNotSendEventError(`${beforeSendLabel} returned \`null\`, will not send event.`);
 }

Expand DownExpand Up@@ -1587,6 +1589,11 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 return processedEvent;
 })
 .then(null, reason => {
 if (reason === CALLBACK_ERROR) {
 recordDroppedEvent('callback_error');
 throw _makeDoNotSendEventError('A user callback threw an error, will not send event.');
 }

 if (_isDoNotSendEventError(reason) || _isInternalError(reason)) {
 throw reason;
 }
Expand DownExpand Up@@ -1702,17 +1709,13 @@ function _validateBeforeSendResult(
): PromiseLike<Event | null> | Event | null {
 const invalidValueError = `${beforeSendLabel} must return \`null\` or a valid event.`;
 if (isThenable(beforeSendResult)) {
 return beforeSendResult.then(
 event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 },
 e => {
 throw _makeInternalError(`${beforeSendLabel} rejected with ${e}`);
 },
 );
 // A rejection can only be `CALLBACK_ERROR` here, as `safeCallback` already handled the user callback rejecting
 return beforeSendResult.then(event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 });
 } else if (!isPlainObject(beforeSendResult) && beforeSendResult !== null) {
 throw _makeInternalError(invalidValueError);
 }
Expand DownExpand Up@@ -1743,7 +1746,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSend` callback threw an error, dropping the event:' : '',
 () => beforeSend(errorEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }

Expand DownExpand Up@@ -1818,7 +1823,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSendTransaction` callback threw an error, dropping the event:' : '',
 () => beforeSendTransaction(processedEvent as TransactionEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }
 }
Expand Down

7 changes: 5 additions & 2 deletions
packages/core/src/eventProcessors.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -3,11 +3,12 @@ import type { Event, EventHint } from './types/event';
import type { EventProcessor } from './types/eventprocessor';
import { debug } from './utils/debug-logger';
import { isThenable } from './utils/is';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { rejectedSyncPromise, resolvedSyncPromise } from './utils/syncpromise';

/**
 * Process an array of event processors, returning the processed event (or `null` if the event was dropped).
 * Rejects with `CALLBACK_ERROR` if a processor throws.
 */
export function notifyEventProcessors(
 processors: EventProcessor[],
Expand DownExpand Up@@ -40,7 +41,9 @@ function _notifyEventProcessors(
 const result = safeCallback(
 DEBUG_BUILD ? `${processorName} threw an error, dropping event:` : '',
 () => processor({ ...event }, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
@Lms24Lms24Sep 3, 2026•

edited

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m: throwing here and in client.ts made me a bit suspicious because we have to be really careful to also catch our throws. Looks like there's a case in replay where we also call prepareEvent which doesn't try/catch the call. I think this only concerns event processor throws though. This leads to us trying to re-send the replay because we assume a network error. Ultimately, we stop recording.
I think we have two options how to avoid this:
  1. we try/catch in Replay so that this doesn't happen
  2. we don't throw at all. Instead, we could directly record an dropped event in notifyEventProcessors and distinguish there.
Tbqh: I haven't thought this through end-to-end, so maybe 1 is easier. I don't see us reusing prepareEvent much in the foreseeable future. But happy to let you make the call (also feel free to come up with something else).
 },
 );

 DEBUG_BUILD && result === null && debug.log(`${processorName} dropped event`);
Expand Down

10 changes: 7 additions & 3 deletions
packages/core/src/logs/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Log, SerializedLog } from '../types/log';
import { consoleSandbox, debug } from '../utils/debug-logger';
import { isParameterizedString } from '../utils/is';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -144,13 +144,17 @@ export function _INTERNAL_captureLog(
 client.emit('beforeCaptureLog', processedLog);

 const log = beforeSendLog
 ? safeCallback(
 ? safeCallback<Log | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendLog` callback threw an error, dropping the log:' : '',
 // We need to wrap this in `consoleSandbox` to avoid recursive calls to `beforeSendLog`
 () => consoleSandbox(() => beforeSendLog(processedLog)),
 () => null,
 () => CALLBACK_ERROR,
 )
 : processedLog;
 if (log === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'log_item', 1);
 return;
 }
 if (!log) {
 client.recordDroppedEvent('before_send', 'log_item', 1);
 DEBUG_BUILD && debug.warn('beforeSendLog returned null, log will not be captured.');
Expand Down

11 changes: 8 additions & 3 deletions
packages/core/src/metrics/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Metric, SerializedMetric } from '../types/metric';
import type { User } from '../types/user';
import { debug } from '../utils/debug-logger';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -183,13 +183,18 @@ export function _INTERNAL_captureMetric(beforeMetric: Metric, options?: Internal
 client.emit('processMetric', enrichedMetric);

 const processedMetric = beforeSendMetric
 ? safeCallback(
 ? safeCallback<Metric | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendMetric` callback threw an error, dropping the metric:' : '',
 () => beforeSendMetric(enrichedMetric),
 () => null,
 () => CALLBACK_ERROR,
 )
 : enrichedMetric;

 if (processedMetric === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'metric', 1);
 return;
 }

 if (!processedMetric) {
 client.recordDroppedEvent('before_send', 'metric', 1);
 DEBUG_BUILD && debug.log('`beforeSendMetric` returned `null`, will not send metric.');
Expand Down

22 changes: 16 additions & 6 deletions
packages/core/src/tracing/sampling.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -6,6 +6,14 @@ import { hasSpansEnabled } from '../utils/hasSpansEnabled';
import { parseSampleRate } from '../utils/parseSampleRate';
import { safeCallback } from '../utils/safeCallback';

interface SamplingDecision {
 sampled: boolean;
 sampleRate?: number;
 localSampleRateWasApplied?: boolean;
 /** Set when the span was dropped for a reason other than the sampling decision itself. */
 dropReason?: 'callback_error';
}

/**
 * Makes a sampling decision for the given options.
 *
Expand All@@ -16,15 +24,17 @@ export function sampleSpan(
 options: Pick<CoreOptions, 'tracesSampleRate' | 'tracesSampler'>,
 samplingContext: SamplingContext,
 sampleRand: number,
): [sampled: boolean, sampleRate?: number, localSampleRateWasApplied?: boolean] {
): SamplingDecision {
@Lms24Lms24Sep 3, 2026

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m: this is API breaking, since sampleSpan is exported. I agree that the object is easier to read though . IIRC, we used the named tuple here for bundle size minimization but this is less readable than the refactor.
Breaking here isn't a big deal though, so we can also do it if the tuple no longer works. But if we do, let's add a note in the migration guide.
 // nothing to do if span recording is not enabled
 if (!hasSpansEnabled(options)) {
 return [false];
 return { sampled: false };
 }

 const resolved = resolveSampleRate(options, samplingContext);
 if (!resolved) {
 return [false];
 // `hasSpansEnabled` guarantees either `tracesSampleRate` or `tracesSampler` is set, so the only way to end up
 // without a sample rate is a throwing `tracesSampler` with nothing to fall back to.
 return { sampled: false, dropReason: 'callback_error' };
 }
 const [sampleRate, localSampleRateWasApplied] = resolved;

Expand All@@ -39,7 +49,7 @@ export function sampleSpan(
 sampleRate,
 )} of type ${JSON.stringify(typeof sampleRate)}.`,
 );
 return [false];
 return { sampled: false };
 }

 // if the function returned 0 (or false), or if `tracesSampleRate` is 0, it's a sign the transaction should be dropped
Expand All@@ -52,7 +62,7 @@ export function sampleSpan(
 : 'a negative sampling decision was inherited or tracesSampleRate is set to 0'
 }`,
 );
 return [false, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: false, sampleRate: parsedSampleRate, localSampleRateWasApplied };
 }

 // We always compare the sample rand for the current execution context against the chosen sample rate.
Expand All@@ -69,7 +79,7 @@ export function sampleSpan(
 );
 }

 return [shouldSample, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: shouldSample, sampleRate: parsedSampleRate, localSampleRateWasApplied };
}

/**
Expand Down

6 changes: 3 additions & 3 deletions
packages/core/src/tracing/trace.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -495,8 +495,8 @@ function _startRootSpan(
 const currentPropagationContext = scope.getPropagationContext();
 const _isTracingSuppressed = isTracingSuppressed(scope);

 const [sampled, sampleRate, localSampleRateWasApplied] = _isTracingSuppressed
 ? [false]
 const { sampled, sampleRate, localSampleRateWasApplied, dropReason } = _isTracingSuppressed
 ? { sampled: false }
 : sampleSpan(
 options,
 {
Expand All@@ -522,7 +522,7 @@ function _startRootSpan(

 if (!sampled && client && !_isTracingSuppressed) {
 DEBUG_BUILD && debug.log('[Tracing] Discarding root span because its trace was not chosen to be sampled.');
 client.recordDroppedEvent('sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 client.recordDroppedEvent(dropReason || 'sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 }

 setCapturedScopesOnSpan(rootSpan, scope, isolationScope);
Expand Down

1 change: 1 addition & 0 deletions
packages/core/src/types/clientreport.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,7 @@ import type { DataCategory } from './datacategory';

export type EventDropReason =
 | 'before_send'
 | 'callback_error'
 | 'event_processor'
 | 'network_error'
 | 'queue_overflow'
Expand Down

7 changes: 7 additions & 0 deletions
packages/core/src/utils/safeCallback.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,13 @@ import { DEBUG_BUILD } from '../debug-build';
import { debug } from './debug-logger';
import { isThenable } from './is';

/**
 * Lets a `safeCallback` fallback signal "the callback failed" as opposed to "the callback returned `null`",
 * so the call site can report the drop as `callback_error`. Return it from synchronous call sites; throw it
 * to abort a promise chain.
 */
export const CALLBACK_ERROR = Symbol.for('SentryCallbackError');

/**
 * Invokes a user-provided callback (e.g. `beforeSend`, `tracesSampler`, an integration hook) so that
 * neither a synchronous throw nor a rejected promise escapes into the caller. On failure the error is
Expand Down

16 changes: 8 additions & 8 deletions
packages/core/test/lib/client.test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2222,7 +2222,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand All@@ -2244,7 +2244,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand DownExpand Up@@ -2277,7 +2277,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('a rejecting event processor stops the processor chain', async () => {
Expand DownExpand Up@@ -2312,7 +2312,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('client-level event processor that throws on all events does not capture a new event', () => {
Expand DownExpand Up@@ -2348,7 +2348,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledTimes(1);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
Expand All@@ -2373,7 +2373,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
 exception,
Expand DownExpand Up@@ -2416,8 +2416,8 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'span', 3);
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'span', 3);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSendTransaction` callback threw an error, dropping the event:',
 exception,
Expand Down
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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feat(core): Record callback_error client reports for throwing user callbacks#23903

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feat(core): Record callback_error client reports for throwing user callbacks
#23903
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2 changes: 1 addition & 1 deletion
...ages/node-integration-tests/suites/client-reports/drop-reasons/before-send-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when beforeSend throws',
 {
 category: 'error',
 quantity: 1,
 reason: 'before_send',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

4 changes: 2 additions & 2 deletions
.../node-integration-tests/suites/client-reports/drop-reasons/event-processor-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when an event processor t
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand All@@ -32,7 +32,7 @@ test('records a client report and no extra error event when an async event proce
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

2 changes: 1 addition & 1 deletion
...s/node-integration-tests/suites/client-reports/drop-reasons/traces-sampler-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no error event when tracesSampler throws', asy
 {
 category: 'span',
 quantity: 1,
 reason: 'sample_rate',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

49 changes: 28 additions & 21 deletions
packages/core/src/client.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,7 @@ import { parseSampleRate } from './utils/parseSampleRate';
import { prepareEvent } from './utils/prepareEvent';
import { makePromiseBuffer, type PromiseBuffer, SENTRY_BUFFER_FULL_ERROR } from './utils/promisebuffer';
import { safeMathRandom } from './utils/randomSafeContext';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { reparentChildSpans, shouldIgnoreSpan } from './utils/should-ignore-span';
import { safeUnref } from './utils/timer';
import { convertSpanJsonToTransactionEvent, convertTransactionEventToSpanJson } from './utils/transactionEvent';
Expand DownExpand Up@@ -1522,6 +1522,14 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 const parsedSampleRate = typeof sampleRate === 'undefined' ? undefined : parseSampleRate(sampleRate);
 const dataCategory = getDataCategoryByType(event.type);

 const recordDroppedEvent = (reason: EventDropReason): void => {
 this.recordDroppedEvent(reason, dataCategory);
 if (isTransaction) {
 // the transaction itself counts as one span, plus all the child spans that are added
 this.recordDroppedEvent(reason, 'span', 1 + (event.spans || []).length);
 }
 };

 return this._prepareEvent(event, hint, currentScope, isolationScope)
 .then(prepared => {
 if (prepared === null) {
Expand All@@ -1539,13 +1547,7 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 })
 .then(processedEvent => {
 if (processedEvent === null) {
 this.recordDroppedEvent('before_send', dataCategory);
 if (isTransaction) {
 const spans = event.spans || [];
 // the transaction itself counts as one span, plus all the child spans that are added
 const spanCount = 1 + spans.length;
 this.recordDroppedEvent('before_send', 'span', spanCount);
 }
 recordDroppedEvent('before_send');
 throw _makeDoNotSendEventError(`${beforeSendLabel} returned \`null\`, will not send event.`);
 }

Expand DownExpand Up@@ -1587,6 +1589,11 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 return processedEvent;
 })
 .then(null, reason => {
 if (reason === CALLBACK_ERROR) {
 recordDroppedEvent('callback_error');
 throw _makeDoNotSendEventError('A user callback threw an error, will not send event.');
 }

 if (_isDoNotSendEventError(reason) || _isInternalError(reason)) {
 throw reason;
 }
Expand DownExpand Up@@ -1702,17 +1709,13 @@ function _validateBeforeSendResult(
): PromiseLike<Event | null> | Event | null {
 const invalidValueError = `${beforeSendLabel} must return \`null\` or a valid event.`;
 if (isThenable(beforeSendResult)) {
 return beforeSendResult.then(
 event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 },
 e => {
 throw _makeInternalError(`${beforeSendLabel} rejected with ${e}`);
 },
 );
 // A rejection can only be `CALLBACK_ERROR` here, as `safeCallback` already handled the user callback rejecting
 return beforeSendResult.then(event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 });
 } else if (!isPlainObject(beforeSendResult) && beforeSendResult !== null) {
 throw _makeInternalError(invalidValueError);
 }
Expand DownExpand Up@@ -1743,7 +1746,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSend` callback threw an error, dropping the event:' : '',
 () => beforeSend(errorEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }

Expand DownExpand Up@@ -1818,7 +1823,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSendTransaction` callback threw an error, dropping the event:' : '',
 () => beforeSendTransaction(processedEvent as TransactionEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }
 }
Expand Down

7 changes: 5 additions & 2 deletions
packages/core/src/eventProcessors.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -3,11 +3,12 @@ import type { Event, EventHint } from './types/event';
import type { EventProcessor } from './types/eventprocessor';
import { debug } from './utils/debug-logger';
import { isThenable } from './utils/is';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { rejectedSyncPromise, resolvedSyncPromise } from './utils/syncpromise';

/**
 * Process an array of event processors, returning the processed event (or `null` if the event was dropped).
 * Rejects with `CALLBACK_ERROR` if a processor throws.
 */
export function notifyEventProcessors(
 processors: EventProcessor[],
Expand DownExpand Up@@ -40,7 +41,9 @@ function _notifyEventProcessors(
 const result = safeCallback(
 DEBUG_BUILD ? `${processorName} threw an error, dropping event:` : '',
 () => processor({ ...event }, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
@Lms24Lms24Sep 3, 2026•

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m: throwing here and in client.ts made me a bit suspicious because we have to be really careful to also catch our throws. Looks like there's a case in replay where we also call prepareEvent which doesn't try/catch the call. I think this only concerns event processor throws though. This leads to us trying to re-send the replay because we assume a network error. Ultimately, we stop recording.
I think we have two options how to avoid this:
  1. we try/catch in Replay so that this doesn't happen
  2. we don't throw at all. Instead, we could directly record an dropped event in notifyEventProcessors and distinguish there.
Tbqh: I haven't thought this through end-to-end, so maybe 1 is easier. I don't see us reusing prepareEvent much in the foreseeable future. But happy to let you make the call (also feel free to come up with something else).
 },
 );

 DEBUG_BUILD && result === null && debug.log(`${processorName} dropped event`);
Expand Down

10 changes: 7 additions & 3 deletions
packages/core/src/logs/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Log, SerializedLog } from '../types/log';
import { consoleSandbox, debug } from '../utils/debug-logger';
import { isParameterizedString } from '../utils/is';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -144,13 +144,17 @@ export function _INTERNAL_captureLog(
 client.emit('beforeCaptureLog', processedLog);

 const log = beforeSendLog
 ? safeCallback(
 ? safeCallback<Log | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendLog` callback threw an error, dropping the log:' : '',
 // We need to wrap this in `consoleSandbox` to avoid recursive calls to `beforeSendLog`
 () => consoleSandbox(() => beforeSendLog(processedLog)),
 () => null,
 () => CALLBACK_ERROR,
 )
 : processedLog;
 if (log === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'log_item', 1);
 return;
 }
 if (!log) {
 client.recordDroppedEvent('before_send', 'log_item', 1);
 DEBUG_BUILD && debug.warn('beforeSendLog returned null, log will not be captured.');
Expand Down

11 changes: 8 additions & 3 deletions
packages/core/src/metrics/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Metric, SerializedMetric } from '../types/metric';
import type { User } from '../types/user';
import { debug } from '../utils/debug-logger';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -183,13 +183,18 @@ export function _INTERNAL_captureMetric(beforeMetric: Metric, options?: Internal
 client.emit('processMetric', enrichedMetric);

 const processedMetric = beforeSendMetric
 ? safeCallback(
 ? safeCallback<Metric | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendMetric` callback threw an error, dropping the metric:' : '',
 () => beforeSendMetric(enrichedMetric),
 () => null,
 () => CALLBACK_ERROR,
 )
 : enrichedMetric;

 if (processedMetric === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'metric', 1);
 return;
 }

 if (!processedMetric) {
 client.recordDroppedEvent('before_send', 'metric', 1);
 DEBUG_BUILD && debug.log('`beforeSendMetric` returned `null`, will not send metric.');
Expand Down

22 changes: 16 additions & 6 deletions
packages/core/src/tracing/sampling.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -6,6 +6,14 @@ import { hasSpansEnabled } from '../utils/hasSpansEnabled';
import { parseSampleRate } from '../utils/parseSampleRate';
import { safeCallback } from '../utils/safeCallback';

interface SamplingDecision {
 sampled: boolean;
 sampleRate?: number;
 localSampleRateWasApplied?: boolean;
 /** Set when the span was dropped for a reason other than the sampling decision itself. */
 dropReason?: 'callback_error';
}

/**
 * Makes a sampling decision for the given options.
 *
Expand All@@ -16,15 +24,17 @@ export function sampleSpan(
 options: Pick<CoreOptions, 'tracesSampleRate' | 'tracesSampler'>,
 samplingContext: SamplingContext,
 sampleRand: number,
): [sampled: boolean, sampleRate?: number, localSampleRateWasApplied?: boolean] {
): SamplingDecision {
@Lms24Lms24Sep 3, 2026

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m: this is API breaking, since sampleSpan is exported. I agree that the object is easier to read though . IIRC, we used the named tuple here for bundle size minimization but this is less readable than the refactor.
Breaking here isn't a big deal though, so we can also do it if the tuple no longer works. But if we do, let's add a note in the migration guide.
 // nothing to do if span recording is not enabled
 if (!hasSpansEnabled(options)) {
 return [false];
 return { sampled: false };
 }

 const resolved = resolveSampleRate(options, samplingContext);
 if (!resolved) {
 return [false];
 // `hasSpansEnabled` guarantees either `tracesSampleRate` or `tracesSampler` is set, so the only way to end up
 // without a sample rate is a throwing `tracesSampler` with nothing to fall back to.
 return { sampled: false, dropReason: 'callback_error' };
 }
 const [sampleRate, localSampleRateWasApplied] = resolved;

Expand All@@ -39,7 +49,7 @@ export function sampleSpan(
 sampleRate,
 )} of type ${JSON.stringify(typeof sampleRate)}.`,
 );
 return [false];
 return { sampled: false };
 }

 // if the function returned 0 (or false), or if `tracesSampleRate` is 0, it's a sign the transaction should be dropped
Expand All@@ -52,7 +62,7 @@ export function sampleSpan(
 : 'a negative sampling decision was inherited or tracesSampleRate is set to 0'
 }`,
 );
 return [false, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: false, sampleRate: parsedSampleRate, localSampleRateWasApplied };
 }

 // We always compare the sample rand for the current execution context against the chosen sample rate.
Expand All@@ -69,7 +79,7 @@ export function sampleSpan(
 );
 }

 return [shouldSample, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: shouldSample, sampleRate: parsedSampleRate, localSampleRateWasApplied };
}

/**
Expand Down

6 changes: 3 additions & 3 deletions
packages/core/src/tracing/trace.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -495,8 +495,8 @@ function _startRootSpan(
 const currentPropagationContext = scope.getPropagationContext();
 const _isTracingSuppressed = isTracingSuppressed(scope);

 const [sampled, sampleRate, localSampleRateWasApplied] = _isTracingSuppressed
 ? [false]
 const { sampled, sampleRate, localSampleRateWasApplied, dropReason } = _isTracingSuppressed
 ? { sampled: false }
 : sampleSpan(
 options,
 {
Expand All@@ -522,7 +522,7 @@ function _startRootSpan(

 if (!sampled && client && !_isTracingSuppressed) {
 DEBUG_BUILD && debug.log('[Tracing] Discarding root span because its trace was not chosen to be sampled.');
 client.recordDroppedEvent('sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 client.recordDroppedEvent(dropReason || 'sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 }

 setCapturedScopesOnSpan(rootSpan, scope, isolationScope);
Expand Down

1 change: 1 addition & 0 deletions
packages/core/src/types/clientreport.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,7 @@ import type { DataCategory } from './datacategory';

export type EventDropReason =
 | 'before_send'
 | 'callback_error'
 | 'event_processor'
 | 'network_error'
 | 'queue_overflow'
Expand Down

7 changes: 7 additions & 0 deletions
packages/core/src/utils/safeCallback.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,13 @@ import { DEBUG_BUILD } from '../debug-build';
import { debug } from './debug-logger';
import { isThenable } from './is';

/**
 * Lets a `safeCallback` fallback signal "the callback failed" as opposed to "the callback returned `null`",
 * so the call site can report the drop as `callback_error`. Return it from synchronous call sites; throw it
 * to abort a promise chain.
 */
export const CALLBACK_ERROR = Symbol.for('SentryCallbackError');

/**
 * Invokes a user-provided callback (e.g. `beforeSend`, `tracesSampler`, an integration hook) so that
 * neither a synchronous throw nor a rejected promise escapes into the caller. On failure the error is
Expand Down

16 changes: 8 additions & 8 deletions
packages/core/test/lib/client.test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2222,7 +2222,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand All@@ -2244,7 +2244,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand DownExpand Up@@ -2277,7 +2277,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('a rejecting event processor stops the processor chain', async () => {
Expand DownExpand Up@@ -2312,7 +2312,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('client-level event processor that throws on all events does not capture a new event', () => {
Expand DownExpand Up@@ -2348,7 +2348,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledTimes(1);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
Expand All@@ -2373,7 +2373,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
 exception,
Expand DownExpand Up@@ -2416,8 +2416,8 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'span', 3);
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'span', 3);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSendTransaction` callback threw an error, dropping the event:',
 exception,
Expand Down
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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feat(core): Record callback_error client reports for throwing user callbacks#23903

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msonnb
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commit into

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+114

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feat(core): Record callback_error client reports for throwing user callbacks
#23903
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2 changes: 1 addition & 1 deletion
...ages/node-integration-tests/suites/client-reports/drop-reasons/before-send-throws/test.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when beforeSend throws',
 {
 category: 'error',
 quantity: 1,
 reason: 'before_send',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

4 changes: 2 additions & 2 deletions
.../node-integration-tests/suites/client-reports/drop-reasons/event-processor-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when an event processor t
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand All@@ -32,7 +32,7 @@ test('records a client report and no extra error event when an async event proce
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

2 changes: 1 addition & 1 deletion
...s/node-integration-tests/suites/client-reports/drop-reasons/traces-sampler-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no error event when tracesSampler throws', asy
 {
 category: 'span',
 quantity: 1,
 reason: 'sample_rate',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

49 changes: 28 additions & 21 deletions
packages/core/src/client.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,7 @@ import { parseSampleRate } from './utils/parseSampleRate';
import { prepareEvent } from './utils/prepareEvent';
import { makePromiseBuffer, type PromiseBuffer, SENTRY_BUFFER_FULL_ERROR } from './utils/promisebuffer';
import { safeMathRandom } from './utils/randomSafeContext';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { reparentChildSpans, shouldIgnoreSpan } from './utils/should-ignore-span';
import { safeUnref } from './utils/timer';
import { convertSpanJsonToTransactionEvent, convertTransactionEventToSpanJson } from './utils/transactionEvent';
Expand DownExpand Up@@ -1522,6 +1522,14 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 const parsedSampleRate = typeof sampleRate === 'undefined' ? undefined : parseSampleRate(sampleRate);
 const dataCategory = getDataCategoryByType(event.type);

 const recordDroppedEvent = (reason: EventDropReason): void => {
 this.recordDroppedEvent(reason, dataCategory);
 if (isTransaction) {
 // the transaction itself counts as one span, plus all the child spans that are added
 this.recordDroppedEvent(reason, 'span', 1 + (event.spans || []).length);
 }
 };

 return this._prepareEvent(event, hint, currentScope, isolationScope)
 .then(prepared => {
 if (prepared === null) {
Expand All@@ -1539,13 +1547,7 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 })
 .then(processedEvent => {
 if (processedEvent === null) {
 this.recordDroppedEvent('before_send', dataCategory);
 if (isTransaction) {
 const spans = event.spans || [];
 // the transaction itself counts as one span, plus all the child spans that are added
 const spanCount = 1 + spans.length;
 this.recordDroppedEvent('before_send', 'span', spanCount);
 }
 recordDroppedEvent('before_send');
 throw _makeDoNotSendEventError(`${beforeSendLabel} returned \`null\`, will not send event.`);
 }

Expand DownExpand Up@@ -1587,6 +1589,11 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 return processedEvent;
 })
 .then(null, reason => {
 if (reason === CALLBACK_ERROR) {
 recordDroppedEvent('callback_error');
 throw _makeDoNotSendEventError('A user callback threw an error, will not send event.');
 }

 if (_isDoNotSendEventError(reason) || _isInternalError(reason)) {
 throw reason;
 }
Expand DownExpand Up@@ -1702,17 +1709,13 @@ function _validateBeforeSendResult(
): PromiseLike<Event | null> | Event | null {
 const invalidValueError = `${beforeSendLabel} must return \`null\` or a valid event.`;
 if (isThenable(beforeSendResult)) {
 return beforeSendResult.then(
 event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 },
 e => {
 throw _makeInternalError(`${beforeSendLabel} rejected with ${e}`);
 },
 );
 // A rejection can only be `CALLBACK_ERROR` here, as `safeCallback` already handled the user callback rejecting
 return beforeSendResult.then(event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 });
 } else if (!isPlainObject(beforeSendResult) && beforeSendResult !== null) {
 throw _makeInternalError(invalidValueError);
 }
Expand DownExpand Up@@ -1743,7 +1746,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSend` callback threw an error, dropping the event:' : '',
 () => beforeSend(errorEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }

Expand DownExpand Up@@ -1818,7 +1823,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSendTransaction` callback threw an error, dropping the event:' : '',
 () => beforeSendTransaction(processedEvent as TransactionEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }
 }
Expand Down

7 changes: 5 additions & 2 deletions
packages/core/src/eventProcessors.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -3,11 +3,12 @@ import type { Event, EventHint } from './types/event';
import type { EventProcessor } from './types/eventprocessor';
import { debug } from './utils/debug-logger';
import { isThenable } from './utils/is';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { rejectedSyncPromise, resolvedSyncPromise } from './utils/syncpromise';

/**
 * Process an array of event processors, returning the processed event (or `null` if the event was dropped).
 * Rejects with `CALLBACK_ERROR` if a processor throws.
 */
export function notifyEventProcessors(
 processors: EventProcessor[],
Expand DownExpand Up@@ -40,7 +41,9 @@ function _notifyEventProcessors(
 const result = safeCallback(
 DEBUG_BUILD ? `${processorName} threw an error, dropping event:` : '',
 () => processor({ ...event }, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
@Lms24Lms24Sep 3, 2026•

edited

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m: throwing here and in client.ts made me a bit suspicious because we have to be really careful to also catch our throws. Looks like there's a case in replay where we also call prepareEvent which doesn't try/catch the call. I think this only concerns event processor throws though. This leads to us trying to re-send the replay because we assume a network error. Ultimately, we stop recording.
I think we have two options how to avoid this:
  1. we try/catch in Replay so that this doesn't happen
  2. we don't throw at all. Instead, we could directly record an dropped event in notifyEventProcessors and distinguish there.
Tbqh: I haven't thought this through end-to-end, so maybe 1 is easier. I don't see us reusing prepareEvent much in the foreseeable future. But happy to let you make the call (also feel free to come up with something else).
 },
 );

 DEBUG_BUILD && result === null && debug.log(`${processorName} dropped event`);
Expand Down

10 changes: 7 additions & 3 deletions
packages/core/src/logs/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Log, SerializedLog } from '../types/log';
import { consoleSandbox, debug } from '../utils/debug-logger';
import { isParameterizedString } from '../utils/is';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -144,13 +144,17 @@ export function _INTERNAL_captureLog(
 client.emit('beforeCaptureLog', processedLog);

 const log = beforeSendLog
 ? safeCallback(
 ? safeCallback<Log | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendLog` callback threw an error, dropping the log:' : '',
 // We need to wrap this in `consoleSandbox` to avoid recursive calls to `beforeSendLog`
 () => consoleSandbox(() => beforeSendLog(processedLog)),
 () => null,
 () => CALLBACK_ERROR,
 )
 : processedLog;
 if (log === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'log_item', 1);
 return;
 }
 if (!log) {
 client.recordDroppedEvent('before_send', 'log_item', 1);
 DEBUG_BUILD && debug.warn('beforeSendLog returned null, log will not be captured.');
Expand Down

11 changes: 8 additions & 3 deletions
packages/core/src/metrics/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Metric, SerializedMetric } from '../types/metric';
import type { User } from '../types/user';
import { debug } from '../utils/debug-logger';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -183,13 +183,18 @@ export function _INTERNAL_captureMetric(beforeMetric: Metric, options?: Internal
 client.emit('processMetric', enrichedMetric);

 const processedMetric = beforeSendMetric
 ? safeCallback(
 ? safeCallback<Metric | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendMetric` callback threw an error, dropping the metric:' : '',
 () => beforeSendMetric(enrichedMetric),
 () => null,
 () => CALLBACK_ERROR,
 )
 : enrichedMetric;

 if (processedMetric === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'metric', 1);
 return;
 }

 if (!processedMetric) {
 client.recordDroppedEvent('before_send', 'metric', 1);
 DEBUG_BUILD && debug.log('`beforeSendMetric` returned `null`, will not send metric.');
Expand Down

22 changes: 16 additions & 6 deletions
packages/core/src/tracing/sampling.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -6,6 +6,14 @@ import { hasSpansEnabled } from '../utils/hasSpansEnabled';
import { parseSampleRate } from '../utils/parseSampleRate';
import { safeCallback } from '../utils/safeCallback';

interface SamplingDecision {
 sampled: boolean;
 sampleRate?: number;
 localSampleRateWasApplied?: boolean;
 /** Set when the span was dropped for a reason other than the sampling decision itself. */
 dropReason?: 'callback_error';
}

/**
 * Makes a sampling decision for the given options.
 *
Expand All@@ -16,15 +24,17 @@ export function sampleSpan(
 options: Pick<CoreOptions, 'tracesSampleRate' | 'tracesSampler'>,
 samplingContext: SamplingContext,
 sampleRand: number,
): [sampled: boolean, sampleRate?: number, localSampleRateWasApplied?: boolean] {
): SamplingDecision {
@Lms24Lms24Sep 3, 2026

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m: this is API breaking, since sampleSpan is exported. I agree that the object is easier to read though . IIRC, we used the named tuple here for bundle size minimization but this is less readable than the refactor.
Breaking here isn't a big deal though, so we can also do it if the tuple no longer works. But if we do, let's add a note in the migration guide.
 // nothing to do if span recording is not enabled
 if (!hasSpansEnabled(options)) {
 return [false];
 return { sampled: false };
 }

 const resolved = resolveSampleRate(options, samplingContext);
 if (!resolved) {
 return [false];
 // `hasSpansEnabled` guarantees either `tracesSampleRate` or `tracesSampler` is set, so the only way to end up
 // without a sample rate is a throwing `tracesSampler` with nothing to fall back to.
 return { sampled: false, dropReason: 'callback_error' };
 }
 const [sampleRate, localSampleRateWasApplied] = resolved;

Expand All@@ -39,7 +49,7 @@ export function sampleSpan(
 sampleRate,
 )} of type ${JSON.stringify(typeof sampleRate)}.`,
 );
 return [false];
 return { sampled: false };
 }

 // if the function returned 0 (or false), or if `tracesSampleRate` is 0, it's a sign the transaction should be dropped
Expand All@@ -52,7 +62,7 @@ export function sampleSpan(
 : 'a negative sampling decision was inherited or tracesSampleRate is set to 0'
 }`,
 );
 return [false, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: false, sampleRate: parsedSampleRate, localSampleRateWasApplied };
 }

 // We always compare the sample rand for the current execution context against the chosen sample rate.
Expand All@@ -69,7 +79,7 @@ export function sampleSpan(
 );
 }

 return [shouldSample, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: shouldSample, sampleRate: parsedSampleRate, localSampleRateWasApplied };
}

/**
Expand Down

6 changes: 3 additions & 3 deletions
packages/core/src/tracing/trace.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -495,8 +495,8 @@ function _startRootSpan(
 const currentPropagationContext = scope.getPropagationContext();
 const _isTracingSuppressed = isTracingSuppressed(scope);

 const [sampled, sampleRate, localSampleRateWasApplied] = _isTracingSuppressed
 ? [false]
 const { sampled, sampleRate, localSampleRateWasApplied, dropReason } = _isTracingSuppressed
 ? { sampled: false }
 : sampleSpan(
 options,
 {
Expand All@@ -522,7 +522,7 @@ function _startRootSpan(

 if (!sampled && client && !_isTracingSuppressed) {
 DEBUG_BUILD && debug.log('[Tracing] Discarding root span because its trace was not chosen to be sampled.');
 client.recordDroppedEvent('sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 client.recordDroppedEvent(dropReason || 'sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 }

 setCapturedScopesOnSpan(rootSpan, scope, isolationScope);
Expand Down

1 change: 1 addition & 0 deletions
packages/core/src/types/clientreport.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,7 @@ import type { DataCategory } from './datacategory';

export type EventDropReason =
 | 'before_send'
 | 'callback_error'
 | 'event_processor'
 | 'network_error'
 | 'queue_overflow'
Expand Down

7 changes: 7 additions & 0 deletions
packages/core/src/utils/safeCallback.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,13 @@ import { DEBUG_BUILD } from '../debug-build';
import { debug } from './debug-logger';
import { isThenable } from './is';

/**
 * Lets a `safeCallback` fallback signal "the callback failed" as opposed to "the callback returned `null`",
 * so the call site can report the drop as `callback_error`. Return it from synchronous call sites; throw it
 * to abort a promise chain.
 */
export const CALLBACK_ERROR = Symbol.for('SentryCallbackError');

/**
 * Invokes a user-provided callback (e.g. `beforeSend`, `tracesSampler`, an integration hook) so that
 * neither a synchronous throw nor a rejected promise escapes into the caller. On failure the error is
Expand Down

16 changes: 8 additions & 8 deletions
packages/core/test/lib/client.test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2222,7 +2222,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand All@@ -2244,7 +2244,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand DownExpand Up@@ -2277,7 +2277,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('a rejecting event processor stops the processor chain', async () => {
Expand DownExpand Up@@ -2312,7 +2312,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('client-level event processor that throws on all events does not capture a new event', () => {
Expand DownExpand Up@@ -2348,7 +2348,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledTimes(1);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
Expand All@@ -2373,7 +2373,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
 exception,
Expand DownExpand Up@@ -2416,8 +2416,8 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'span', 3);
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'span', 3);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSendTransaction` callback threw an error, dropping the event:',
 exception,
Expand Down
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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feat(core): Record callback_error client reports for throwing user callbacks
#23903
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2 changes: 1 addition & 1 deletion
...ages/node-integration-tests/suites/client-reports/drop-reasons/before-send-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when beforeSend throws',
 {
 category: 'error',
 quantity: 1,
 reason: 'before_send',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

4 changes: 2 additions & 2 deletions
.../node-integration-tests/suites/client-reports/drop-reasons/event-processor-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no extra error event when an event processor t
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand All@@ -32,7 +32,7 @@ test('records a client report and no extra error event when an async event proce
 {
 category: 'error',
 quantity: 1,
 reason: 'event_processor',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

2 changes: 1 addition & 1 deletion
...s/node-integration-tests/suites/client-reports/drop-reasons/traces-sampler-throws/test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -14,7 +14,7 @@ test('records a client report and no error event when tracesSampler throws', asy
 {
 category: 'span',
 quantity: 1,
 reason: 'sample_rate',
 reason: 'callback_error',
 },
 ],
 },
Expand Down

49 changes: 28 additions & 21 deletions
packages/core/src/client.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,7 @@ import { parseSampleRate } from './utils/parseSampleRate';
import { prepareEvent } from './utils/prepareEvent';
import { makePromiseBuffer, type PromiseBuffer, SENTRY_BUFFER_FULL_ERROR } from './utils/promisebuffer';
import { safeMathRandom } from './utils/randomSafeContext';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { reparentChildSpans, shouldIgnoreSpan } from './utils/should-ignore-span';
import { safeUnref } from './utils/timer';
import { convertSpanJsonToTransactionEvent, convertTransactionEventToSpanJson } from './utils/transactionEvent';
Expand DownExpand Up@@ -1522,6 +1522,14 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 const parsedSampleRate = typeof sampleRate === 'undefined' ? undefined : parseSampleRate(sampleRate);
 const dataCategory = getDataCategoryByType(event.type);

 const recordDroppedEvent = (reason: EventDropReason): void => {
 this.recordDroppedEvent(reason, dataCategory);
 if (isTransaction) {
 // the transaction itself counts as one span, plus all the child spans that are added
 this.recordDroppedEvent(reason, 'span', 1 + (event.spans || []).length);
 }
 };

 return this._prepareEvent(event, hint, currentScope, isolationScope)
 .then(prepared => {
 if (prepared === null) {
Expand All@@ -1539,13 +1547,7 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 })
 .then(processedEvent => {
 if (processedEvent === null) {
 this.recordDroppedEvent('before_send', dataCategory);
 if (isTransaction) {
 const spans = event.spans || [];
 // the transaction itself counts as one span, plus all the child spans that are added
 const spanCount = 1 + spans.length;
 this.recordDroppedEvent('before_send', 'span', spanCount);
 }
 recordDroppedEvent('before_send');
 throw _makeDoNotSendEventError(`${beforeSendLabel} returned \`null\`, will not send event.`);
 }

Expand DownExpand Up@@ -1587,6 +1589,11 @@ export abstract class Client<O extends ClientOptions = ClientOptions> {
 return processedEvent;
 })
 .then(null, reason => {
 if (reason === CALLBACK_ERROR) {
 recordDroppedEvent('callback_error');
 throw _makeDoNotSendEventError('A user callback threw an error, will not send event.');
 }

 if (_isDoNotSendEventError(reason) || _isInternalError(reason)) {
 throw reason;
 }
Expand DownExpand Up@@ -1702,17 +1709,13 @@ function _validateBeforeSendResult(
): PromiseLike<Event | null> | Event | null {
 const invalidValueError = `${beforeSendLabel} must return \`null\` or a valid event.`;
 if (isThenable(beforeSendResult)) {
 return beforeSendResult.then(
 event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 },
 e => {
 throw _makeInternalError(`${beforeSendLabel} rejected with ${e}`);
 },
 );
 // A rejection can only be `CALLBACK_ERROR` here, as `safeCallback` already handled the user callback rejecting
 return beforeSendResult.then(event => {
 if (!isPlainObject(event) && event !== null) {
 throw _makeInternalError(invalidValueError);
 }
 return event;
 });
 } else if (!isPlainObject(beforeSendResult) && beforeSendResult !== null) {
 throw _makeInternalError(invalidValueError);
 }
Expand DownExpand Up@@ -1743,7 +1746,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSend` callback threw an error, dropping the event:' : '',
 () => beforeSend(errorEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }

Expand DownExpand Up@@ -1818,7 +1823,9 @@ function processBeforeSend(
 return safeCallback(
 DEBUG_BUILD ? 'The `beforeSendTransaction` callback threw an error, dropping the event:' : '',
 () => beforeSendTransaction(processedEvent as TransactionEvent, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
 },
 );
 }
 }
Expand Down

7 changes: 5 additions & 2 deletions
packages/core/src/eventProcessors.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -3,11 +3,12 @@ import type { Event, EventHint } from './types/event';
import type { EventProcessor } from './types/eventprocessor';
import { debug } from './utils/debug-logger';
import { isThenable } from './utils/is';
import { safeCallback } from './utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from './utils/safeCallback';
import { rejectedSyncPromise, resolvedSyncPromise } from './utils/syncpromise';

/**
 * Process an array of event processors, returning the processed event (or `null` if the event was dropped).
 * Rejects with `CALLBACK_ERROR` if a processor throws.
 */
export function notifyEventProcessors(
 processors: EventProcessor[],
Expand DownExpand Up@@ -40,7 +41,9 @@ function _notifyEventProcessors(
 const result = safeCallback(
 DEBUG_BUILD ? `${processorName} threw an error, dropping event:` : '',
 () => processor({ ...event }, hint),
 () => null,
 () => {
 throw CALLBACK_ERROR;
@Lms24Lms24Sep 3, 2026•

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m: throwing here and in client.ts made me a bit suspicious because we have to be really careful to also catch our throws. Looks like there's a case in replay where we also call prepareEvent which doesn't try/catch the call. I think this only concerns event processor throws though. This leads to us trying to re-send the replay because we assume a network error. Ultimately, we stop recording.
I think we have two options how to avoid this:
  1. we try/catch in Replay so that this doesn't happen
  2. we don't throw at all. Instead, we could directly record an dropped event in notifyEventProcessors and distinguish there.
Tbqh: I haven't thought this through end-to-end, so maybe 1 is easier. I don't see us reusing prepareEvent much in the foreseeable future. But happy to let you make the call (also feel free to come up with something else).
 },
 );

 DEBUG_BUILD && result === null && debug.log(`${processorName} dropped event`);
Expand Down

10 changes: 7 additions & 3 deletions
packages/core/src/logs/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Log, SerializedLog } from '../types/log';
import { consoleSandbox, debug } from '../utils/debug-logger';
import { isParameterizedString } from '../utils/is';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -144,13 +144,17 @@ export function _INTERNAL_captureLog(
 client.emit('beforeCaptureLog', processedLog);

 const log = beforeSendLog
 ? safeCallback(
 ? safeCallback<Log | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendLog` callback threw an error, dropping the log:' : '',
 // We need to wrap this in `consoleSandbox` to avoid recursive calls to `beforeSendLog`
 () => consoleSandbox(() => beforeSendLog(processedLog)),
 () => null,
 () => CALLBACK_ERROR,
 )
 : processedLog;
 if (log === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'log_item', 1);
 return;
 }
 if (!log) {
 client.recordDroppedEvent('before_send', 'log_item', 1);
 DEBUG_BUILD && debug.warn('beforeSendLog returned null, log will not be captured.');
Expand Down

11 changes: 8 additions & 3 deletions
packages/core/src/metrics/internal.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -8,7 +8,7 @@ import type { Integration } from '../types/integration';
import type { Metric, SerializedMetric } from '../types/metric';
import type { User } from '../types/user';
import { debug } from '../utils/debug-logger';
import { safeCallback } from '../utils/safeCallback';
import { CALLBACK_ERROR, safeCallback } from '../utils/safeCallback';
import { getCombinedScopeData } from '../utils/scopeData';
import { getActiveSpan } from '../utils/spanUtils';
import { timestampInSeconds } from '../utils/time';
Expand DownExpand Up@@ -183,13 +183,18 @@ export function _INTERNAL_captureMetric(beforeMetric: Metric, options?: Internal
 client.emit('processMetric', enrichedMetric);

 const processedMetric = beforeSendMetric
 ? safeCallback(
 ? safeCallback<Metric | null | typeof CALLBACK_ERROR>(
 DEBUG_BUILD ? 'The `beforeSendMetric` callback threw an error, dropping the metric:' : '',
 () => beforeSendMetric(enrichedMetric),
 () => null,
 () => CALLBACK_ERROR,
 )
 : enrichedMetric;

 if (processedMetric === CALLBACK_ERROR) {
 client.recordDroppedEvent('callback_error', 'metric', 1);
 return;
 }

 if (!processedMetric) {
 client.recordDroppedEvent('before_send', 'metric', 1);
 DEBUG_BUILD && debug.log('`beforeSendMetric` returned `null`, will not send metric.');
Expand Down

22 changes: 16 additions & 6 deletions
packages/core/src/tracing/sampling.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -6,6 +6,14 @@ import { hasSpansEnabled } from '../utils/hasSpansEnabled';
import { parseSampleRate } from '../utils/parseSampleRate';
import { safeCallback } from '../utils/safeCallback';

interface SamplingDecision {
 sampled: boolean;
 sampleRate?: number;
 localSampleRateWasApplied?: boolean;
 /** Set when the span was dropped for a reason other than the sampling decision itself. */
 dropReason?: 'callback_error';
}

/**
 * Makes a sampling decision for the given options.
 *
Expand All@@ -16,15 +24,17 @@ export function sampleSpan(
 options: Pick<CoreOptions, 'tracesSampleRate' | 'tracesSampler'>,
 samplingContext: SamplingContext,
 sampleRand: number,
): [sampled: boolean, sampleRate?: number, localSampleRateWasApplied?: boolean] {
): SamplingDecision {
@Lms24Lms24Sep 3, 2026

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m: this is API breaking, since sampleSpan is exported. I agree that the object is easier to read though . IIRC, we used the named tuple here for bundle size minimization but this is less readable than the refactor.
Breaking here isn't a big deal though, so we can also do it if the tuple no longer works. But if we do, let's add a note in the migration guide.
 // nothing to do if span recording is not enabled
 if (!hasSpansEnabled(options)) {
 return [false];
 return { sampled: false };
 }

 const resolved = resolveSampleRate(options, samplingContext);
 if (!resolved) {
 return [false];
 // `hasSpansEnabled` guarantees either `tracesSampleRate` or `tracesSampler` is set, so the only way to end up
 // without a sample rate is a throwing `tracesSampler` with nothing to fall back to.
 return { sampled: false, dropReason: 'callback_error' };
 }
 const [sampleRate, localSampleRateWasApplied] = resolved;

Expand All@@ -39,7 +49,7 @@ export function sampleSpan(
 sampleRate,
 )} of type ${JSON.stringify(typeof sampleRate)}.`,
 );
 return [false];
 return { sampled: false };
 }

 // if the function returned 0 (or false), or if `tracesSampleRate` is 0, it's a sign the transaction should be dropped
Expand All@@ -52,7 +62,7 @@ export function sampleSpan(
 : 'a negative sampling decision was inherited or tracesSampleRate is set to 0'
 }`,
 );
 return [false, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: false, sampleRate: parsedSampleRate, localSampleRateWasApplied };
 }

 // We always compare the sample rand for the current execution context against the chosen sample rate.
Expand All@@ -69,7 +79,7 @@ export function sampleSpan(
 );
 }

 return [shouldSample, parsedSampleRate, localSampleRateWasApplied];
 return { sampled: shouldSample, sampleRate: parsedSampleRate, localSampleRateWasApplied };
}

/**
Expand Down

6 changes: 3 additions & 3 deletions
packages/core/src/tracing/trace.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -495,8 +495,8 @@ function _startRootSpan(
 const currentPropagationContext = scope.getPropagationContext();
 const _isTracingSuppressed = isTracingSuppressed(scope);

 const [sampled, sampleRate, localSampleRateWasApplied] = _isTracingSuppressed
 ? [false]
 const { sampled, sampleRate, localSampleRateWasApplied, dropReason } = _isTracingSuppressed
 ? { sampled: false }
 : sampleSpan(
 options,
 {
Expand All@@ -522,7 +522,7 @@ function _startRootSpan(

 if (!sampled && client && !_isTracingSuppressed) {
 DEBUG_BUILD && debug.log('[Tracing] Discarding root span because its trace was not chosen to be sampled.');
 client.recordDroppedEvent('sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 client.recordDroppedEvent(dropReason || 'sample_rate', hasSpanStreamingEnabled(client) ? 'span' : 'transaction');
 }

 setCapturedScopesOnSpan(rootSpan, scope, isolationScope);
Expand Down

1 change: 1 addition & 0 deletions
packages/core/src/types/clientreport.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,7 @@ import type { DataCategory } from './datacategory';

export type EventDropReason =
 | 'before_send'
 | 'callback_error'
 | 'event_processor'
 | 'network_error'
 | 'queue_overflow'
Expand Down

7 changes: 7 additions & 0 deletions
packages/core/src/utils/safeCallback.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2,6 +2,13 @@ import { DEBUG_BUILD } from '../debug-build';
import { debug } from './debug-logger';
import { isThenable } from './is';

/**
 * Lets a `safeCallback` fallback signal "the callback failed" as opposed to "the callback returned `null`",
 * so the call site can report the drop as `callback_error`. Return it from synchronous call sites; throw it
 * to abort a promise chain.
 */
export const CALLBACK_ERROR = Symbol.for('SentryCallbackError');

/**
 * Invokes a user-provided callback (e.g. `beforeSend`, `tracesSampler`, an integration hook) so that
 * neither a synchronous throw nor a rejected promise escapes into the caller. On failure the error is
Expand Down

16 changes: 8 additions & 8 deletions
packages/core/test/lib/client.test.ts

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Original file line numberDiff line numberDiff line change
Expand Up@@ -2222,7 +2222,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand All@@ -2244,7 +2244,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith('Event processor "?" threw an error, dropping event:', exception);
 });

Expand DownExpand Up@@ -2277,7 +2277,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('a rejecting event processor stops the processor chain', async () => {
Expand DownExpand Up@@ -2312,7 +2312,7 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('event_processor', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 });

 test('client-level event processor that throws on all events does not capture a new event', () => {
Expand DownExpand Up@@ -2348,7 +2348,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledTimes(1);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
Expand All@@ -2373,7 +2373,7 @@ describe('Client', () => {
 expect(beforeSend).toHaveBeenCalledTimes(1);
 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'error');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'error');
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSend` callback threw an error, dropping the event:',
 exception,
Expand DownExpand Up@@ -2416,8 +2416,8 @@ describe('Client', () => {

 expect(TestClient.instance!.event).toBeUndefined();
 expect(captureExceptionSpy).not.toHaveBeenCalled();
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('before_send', 'span', 3);
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'transaction');
 expect(recordDroppedEventSpy).toHaveBeenCalledWith('callback_error', 'span', 3);
 expect(debugErrorSpy).toHaveBeenCalledWith(
 'The `beforeSendTransaction` callback threw an error, dropping the event:',
 exception,
Expand Down
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