From f13b1ab184a0d660c2808bd32ec2db64d2f83bf0 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Thu, 24 Sep 2026 15:21:07 +0200
Subject: [PATCH 1/3] fix: Drop events if processor raises

This reverts commit b499d89b689157385a1b85f6f9f8d5f845f40b9f.
---
 sentry_sdk/scope.py  |  4 ++--
 tests/test_basics.py | 43 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/sentry_sdk/scope.py b/sentry_sdk/scope.py
index 3081d95140..8519bc5263 100644
--- a/sentry_sdk/scope.py
+++ b/sentry_sdk/scope.py
@@ -1480,7 +1480,7 @@ def run_error_processors(self, event: "Event", hint: "Hint") -> "Optional[Event]
             )
 
             for error_processor in error_processors:
-                new_event = event
+                new_event = None
                 with capture_internal_exceptions():
                     new_event = error_processor(event, exc_info)
                 if new_event is None:
@@ -1510,7 +1510,7 @@ def run_event_processors(self, event: "Event", hint: "Hint") -> "Optional[Event]
             )
 
             for event_processor in event_processors:
-                new_event = event
+                new_event = None
                 with capture_internal_exceptions():
                     new_event = event_processor(event, hint)
                 if new_event is None:
diff --git a/tests/test_basics.py b/tests/test_basics.py
index d746146baa..131895c8e7 100644
--- a/tests/test_basics.py
+++ b/tests/test_basics.py
@@ -661,6 +661,49 @@ def foo(event, hint):
         sentry_sdk.scope.global_event_processors = old_processors
 
 
+@pytest.mark.tests_internal_exceptions
+def test_event_processor_exception_drops_event_and_records_client_report(
+    sentry_init, capture_events, capture_record_lost_event_calls
+):
+    sentry_init(default_integrations=False)
+    events = capture_events()
+    record_lost_event_calls = capture_record_lost_event_calls()
+
+    scope = sentry_sdk.get_isolation_scope()
+
+    @scope.add_event_processor
+    def bad_processor(event, hint):
+        raise ValueError("processor error")
+
+    capture_message("should be dropped")
+
+    assert len(events) == 0
+    assert ("event_processor", "error", None, 1) in record_lost_event_calls
+
+
+@pytest.mark.tests_internal_exceptions
+def test_error_processor_exception_drops_event(
+    sentry_init, capture_events, capture_record_lost_event_calls
+):
+    sentry_init(default_integrations=False)
+    events = capture_events()
+    record_lost_event_calls = capture_record_lost_event_calls()
+
+    scope = sentry_sdk.get_isolation_scope()
+
+    @scope.add_error_processor
+    def bad_error_processor(event, exc_info):
+        raise ValueError("error processor error")
+
+    try:
+        raise ValueError("original error")
+    except Exception:
+        capture_exception()
+
+    assert len(events) == 0
+    assert ("event_processor", "error", None, 1) in record_lost_event_calls
+
+
 @pytest.mark.tests_internal_exceptions
 def test_before_send_exception_records_callback_error(
     sentry_init, capture_events, capture_record_lost_event_calls

From 593af0ca6c47dfd8ef06f68152983ed970f915a9 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Thu, 24 Sep 2026 15:23:39 +0200
Subject: [PATCH 2/3] breadcrumbs, too

---
 sentry_sdk/scope.py  | 2 +-
 tests/test_basics.py | 7 ++-----
 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/sentry_sdk/scope.py b/sentry_sdk/scope.py
index 8519bc5263..4f0830bf97 100644
--- a/sentry_sdk/scope.py
+++ b/sentry_sdk/scope.py
@@ -917,7 +917,7 @@ def add_breadcrumb(
         if crumb.get("type") is None:
             crumb["type"] = "default"
 
-        new_crumb = crumb
+        new_crumb = None
         if before_breadcrumb is not None:
             with capture_internal_exceptions():
                 new_crumb = before_breadcrumb(crumb, hint)
diff --git a/tests/test_basics.py b/tests/test_basics.py
index 131895c8e7..38861c4cf9 100644
--- a/tests/test_basics.py
+++ b/tests/test_basics.py
@@ -214,7 +214,7 @@ def do_this():
 
 @pytest.mark.tests_internal_exceptions
 def test_option_before_breadcrumb_exception(sentry_init, capture_events):
-    """Exceptions in before_breadcrumb are contained."""
+    """Breadcrumb is dropped if before_breadcrumb raises an exception."""
 
     def before_breadcrumb(crumb, hint):
         1 / 0
@@ -234,10 +234,7 @@ def do_this():
     (event,) = events
 
     assert event["exception"]["values"][0]["type"] == "ValueError"
-    (crumb,) = event["breadcrumbs"]["values"]
-    assert "timestamp" in crumb
-    assert crumb["message"] == "Hello"
-    assert crumb["type"] == "default"
+    assert event["breadcrumbs"]["values"] == []
 
 
 def test_breadcrumb_arguments(sentry_init, capture_events):

From 21121d1b4e99b761a84fb3fd8165b93e168b2b5f Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Thu, 24 Sep 2026 16:11:07 +0200
Subject: [PATCH 3/3] fix

---
 sentry_sdk/scope.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sentry_sdk/scope.py b/sentry_sdk/scope.py
index 4f0830bf97..4a0fbcac28 100644
--- a/sentry_sdk/scope.py
+++ b/sentry_sdk/scope.py
@@ -917,8 +917,9 @@ def add_breadcrumb(
         if crumb.get("type") is None:
             crumb["type"] = "default"
 
-        new_crumb = None
+        new_crumb = crumb
         if before_breadcrumb is not None:
+            new_crumb = None
             with capture_internal_exceptions():
                 new_crumb = before_breadcrumb(crumb, hint)