From 25d07debba5d8a4cfa06ca90d7055843caaac013 Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Fri, 7 Aug 2026 11:19:48 +0200
Subject: [PATCH] fix: Do not let exceptions in before_breadcrumb bubble up

---
 sentry_sdk/scope.py  |  6 +++---
 tests/test_basics.py | 28 ++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/sentry_sdk/scope.py b/sentry_sdk/scope.py
index 09e8876d6d..09c580defa 100644
--- a/sentry_sdk/scope.py
+++ b/sentry_sdk/scope.py
@@ -1090,10 +1090,10 @@ def add_breadcrumb(
         if crumb.get("type") is None:
             crumb["type"] = "default"
 
+        new_crumb = crumb
         if before_breadcrumb is not None:
-            new_crumb = before_breadcrumb(crumb, hint)
-        else:
-            new_crumb = crumb
+            with capture_internal_exceptions():
+                new_crumb = before_breadcrumb(crumb, hint)
 
         if new_crumb is not None:
             self._breadcrumbs.append(new_crumb)
diff --git a/tests/test_basics.py b/tests/test_basics.py
index db1a028c45..2d7dfc4a68 100644
--- a/tests/test_basics.py
+++ b/tests/test_basics.py
@@ -250,6 +250,34 @@ def do_this():
     assert crumb["type"] == "default"
 
 
+@pytest.mark.tests_internal_exceptions
+def test_option_before_breadcrumb_exception(sentry_init, capture_events):
+    """Exceptions in before_breadcrumb are contained."""
+
+    def before_breadcrumb(crumb, hint):
+        1 / 0
+
+    sentry_init(before_breadcrumb=before_breadcrumb)
+    events = capture_events()
+
+    def do_this():
+        add_breadcrumb(message="Hello", hint={"foo": 42})
+        try:
+            raise ValueError("aha!")
+        except Exception:
+            capture_exception()
+
+    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"
+
+
 @pytest.mark.parametrize(
     "enable_tracing, traces_sample_rate, tracing_enabled, updated_traces_sample_rate",
     [