From 59a68d0e800d6c75283123ca8cee5add51a2117b Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 14 Jan 2026 14:26:57 +0100
Subject: [PATCH 1/2] fix: Send client reports for span recorder overflow

---
 sentry_sdk/client.py       | 14 +++++++++++++-
 tests/tracing/test_misc.py | 20 ++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/sentry_sdk/client.py b/sentry_sdk/client.py
index e3821f48ca..409ce6551f 100644
--- a/sentry_sdk/client.py
+++ b/sentry_sdk/client.py
@@ -532,7 +532,19 @@ def _prepare_event(
                     "event_processor", data_category="span", quantity=spans_delta
                 )
 
-            dropped_spans: int = event.pop("_dropped_spans", 0) + spans_delta
+            span_recorder_dropped_spans: int = event.pop("_dropped_spans", 0)
+            if (
+                is_transaction
+                and span_recorder_dropped_spans > 0
+                and self.transport is not None
+            ):
+                self.transport.record_lost_event(
+                    "buffer_overflow",
+                    data_category="span",
+                    quantity=span_recorder_dropped_spans,
+                )
+
+            dropped_spans: int = span_recorder_dropped_spans + spans_delta
             if dropped_spans > 0:
                 previous_total_spans = spans_before + dropped_spans
             if scope._n_breadcrumbs_truncated > 0:
diff --git a/tests/tracing/test_misc.py b/tests/tracing/test_misc.py
index e1de847102..619fff913b 100644
--- a/tests/tracing/test_misc.py
+++ b/tests/tracing/test_misc.py
@@ -37,6 +37,26 @@ def test_span_trimming(sentry_init, capture_events):
     assert "dropped_spans" not in event
 
 
+def test_span_trimming_produces_client_report(
+    sentry_init, capture_events, capture_record_lost_event_calls
+):
+    sentry_init(traces_sample_rate=1.0, _experiments={"max_spans": 3})
+    events = capture_events()
+    record_lost_event_calls = capture_record_lost_event_calls()
+
+    with start_transaction(name="hi"):
+        for i in range(10):
+            with start_span(op="foo{}".format(i)):
+                pass
+
+    (event,) = events
+
+    assert len(event["spans"]) == 3
+
+    # 7 spans were dropped (10 total - 3 kept = 7 dropped)
+    assert ("buffer_overflow", "span", None, 7) in record_lost_event_calls
+
+
 def test_span_data_scrubbing_and_trimming(sentry_init, capture_events):
     sentry_init(traces_sample_rate=1.0, _experiments={"max_spans": 3})
     events = capture_events()

From e853aa4e4a5786948b3d581d30a111d7b403161a Mon Sep 17 00:00:00 2001
From: Ivana Kellyer <ivana.kellyer@sentry.io>
Date: Wed, 14 Jan 2026 14:33:03 +0100
Subject: [PATCH 2/2] ref

---
 sentry_sdk/client.py | 27 ++++++++++++---------------
 1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/sentry_sdk/client.py b/sentry_sdk/client.py
index 409ce6551f..fb14d8e36a 100644
--- a/sentry_sdk/client.py
+++ b/sentry_sdk/client.py
@@ -527,22 +527,19 @@ def _prepare_event(
             spans_delta = spans_before - len(
                 cast(List[Dict[str, object]], event.get("spans", []))
             )
-            if is_transaction and spans_delta > 0 and self.transport is not None:
-                self.transport.record_lost_event(
-                    "event_processor", data_category="span", quantity=spans_delta
-                )
-
             span_recorder_dropped_spans: int = event.pop("_dropped_spans", 0)
-            if (
-                is_transaction
-                and span_recorder_dropped_spans > 0
-                and self.transport is not None
-            ):
-                self.transport.record_lost_event(
-                    "buffer_overflow",
-                    data_category="span",
-                    quantity=span_recorder_dropped_spans,
-                )
+
+            if is_transaction and self.transport is not None:
+                if spans_delta > 0:
+                    self.transport.record_lost_event(
+                        "event_processor", data_category="span", quantity=spans_delta
+                    )
+                if span_recorder_dropped_spans > 0:
+                    self.transport.record_lost_event(
+                        "buffer_overflow",
+                        data_category="span",
+                        quantity=span_recorder_dropped_spans,
+                    )
 
             dropped_spans: int = span_recorder_dropped_spans + spans_delta
             if dropped_spans > 0: