Do not retry 4xx uploads

CHANGELOG.md

@@ -49,6 +49,7 @@
   - Add layer class filtering for views used in multiple contexts (e.g., SwiftUI._UIGraphicsView)
   - Improve transform calculations for views with custom anchor points
   - Fix axis-aligned transform detection for optimized opaque view clipping
+- Fix issue where a too-large breadcrumb would prevent future errors and messages from being uploaded (#6617)
 
 ### Improvements
 

Sources/Sentry/SentryHttpTransport.m

@@ -414,6 +414,13 @@ - (void)sendEnvelope:(SentryEnvelope *)envelope
                 return;
             }
 
+            if (response.statusCode >= 400 && response.statusCode < 500) {
+                SENTRY_LOG_DEBUG(@"Received 4xx response code: %li", (long)response.statusCode);
+                // 4xx means the payload is bad and will not succeed on retry. Drop it on the floor and enable sending the next one.
+                [weakSelf deleteEnvelopeAndSendNext:envelopePath];
+                return;
+            }
+
             SENTRY_LOG_DEBUG(@"Received non-200 response code: %li", (long)response.statusCode);
             [weakSelf finishedSending];
         }];