diff --git a/.buildkite/pipeline.yml b/.buildkite/pipeline.yml
index 98d4f67..ff37de0 100644
--- a/.buildkite/pipeline.yml
+++ b/.buildkite/pipeline.yml
@@ -55,10 +55,14 @@ steps:
           - "--app=/app/features/fixtures/mazerunner/build/ios/ipa/mazerunner.ipa"
           - "--farm=bb"
           - "--device=IOS_14|IOS_15|IOS_16"
+          - "--fail-fast"
           - "--no-tunnel"
           - "--aws-public-ip"
-          - "--fail-fast"
           - "--appium-version=1.22"
+      test-collector#v1.10.2:
+        files: "reports/TEST-*.xml"
+        format: "junit"
+        branch: "^main|next$$"
     concurrency: 25
     concurrency_group: 'bitbar'
     concurrency_method: eager
@@ -102,10 +106,14 @@ steps:
           - "--app=features/fixtures/mazerunner/build/app/outputs/flutter-apk/app-release.apk"
           - "--farm=bb"
           - "--device=ANDROID_10|ANDROID_11|ANDROID_12|ANDROID_13"
+          - "--fail-fast"
           - "--no-tunnel"
           - "--aws-public-ip"
-          - "--fail-fast"
           - "--appium-version=1.22"
+      test-collector#v1.10.2:
+        files: "reports/TEST-*.xml"
+        format: "junit"
+        branch: "^main|next$$"
     concurrency: 25
     concurrency_group: 'bitbar'
     concurrency_method: eager
diff --git a/CHANGELOG.md b/CHANGELOG.md
index c25f66f..7423fb0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,14 @@
 Changelog
 =========
 
+## 1.3.0 (2024-09-30)
+
+### Enhancements
+
+* Custom attributes can now be set on a span, including as lists of primitives (int, double, bool, String) [88](https://github.com/bugsnag/bugsnag-flutter-performance/pull/88)
+
+* Introduced OnSpanEndCallbacks that allow changes to spans when their end() method is called, but before they are sent [88](https://github.com/bugsnag/bugsnag-flutter-performance/pull/88)
+
 ## 1.2.1 (2024-09-18)
 
 ### Bug fixes
diff --git a/VERSION b/VERSION
index 6085e94..f0bb29e 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.2.1
+1.3.0
diff --git a/docker-compose.yml b/docker-compose.yml
index ddceb54..5aeee6c 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -20,14 +20,17 @@ services:
       BUILDKITE_REPO:
       BUILDKITE_RETRY_COUNT:
       BUILDKITE_STEP_KEY:
+      BUILDKITE_ANALYTICS_TOKEN:
       MAZE_BUGSNAG_API_KEY:
       MAZE_REPEATER_API_KEY:
+      MAZE_NO_FAIL_FAST:
     ports:
       - "9000-9499:9339"
     volumes:
       - ./features/:/app/features/
       - ./maze_output:/app/maze_output
       - /var/run/docker.sock:/var/run/docker.sock
+      - ./reports/:/app/reports/
 
 networks:
   default:
diff --git a/features/fixture_resources/lib/channels.dart b/features/fixture_resources/lib/channels.dart
index d270452..70d2b4a 100644
--- a/features/fixture_resources/lib/channels.dart
+++ b/features/fixture_resources/lib/channels.dart
@@ -1,4 +1,3 @@
-import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'package:flutter/services.dart';
 
 class MazeRunnerChannels {
diff --git a/features/fixture_resources/lib/main.dart b/features/fixture_resources/lib/main.dart
index 59c43de..fa04dcb 100644
--- a/features/fixture_resources/lib/main.dart
+++ b/features/fixture_resources/lib/main.dart
@@ -84,7 +84,7 @@ class Command {
 }
 
 class MazeRunnerFlutterApp extends StatelessWidget {
-  const MazeRunnerFlutterApp({Key? key}) : super(key: key);
+  const MazeRunnerFlutterApp({super.key});
 
   @override
   Widget build(BuildContext context) {
@@ -151,9 +151,9 @@ class MazeRunnerHomePage extends StatefulWidget {
   final String mazerunnerUrl;
 
   const MazeRunnerHomePage({
-    Key? key,
+    super.key,
     required this.mazerunnerUrl,
-  }) : super(key: key);
+  });
 
   @override
   State<MazeRunnerHomePage> createState() => _HomePageState();
@@ -332,9 +332,9 @@ class _HomePageState extends State<MazeRunnerHomePage> {
                 height: 400.0,
                 width: double.infinity,
                 child: TextButton(
-                  child: const Text("Run Command"),
                   onPressed: () => _onRunCommand(context),
                   key: const Key("runCommand"),
+                  child: const Text("Run Command"),
                 ),
               ),
               TextField(
@@ -373,14 +373,14 @@ class _HomePageState extends State<MazeRunnerHomePage> {
                 ),
               ),
               TextButton(
-                child: const Text("Start Bugsnag"),
                 onPressed: _onStartBugsnag,
                 key: const Key("startBugsnag"),
+                child: const Text("Start Bugsnag"),
               ),
               TextButton(
-                child: const Text("Run Scenario"),
                 onPressed: () => _onRunScenario(context),
                 key: const Key("startScenario"),
+                child: const Text("Run Scenario"),
               ),
             ],
           ),
diff --git a/features/fixture_resources/lib/scenarios/auto_instrument_app_starts_scenario.dart b/features/fixture_resources/lib/scenarios/auto_instrument_app_starts_scenario.dart
index f19836a..b56519b 100644
--- a/features/fixture_resources/lib/scenarios/auto_instrument_app_starts_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/auto_instrument_app_starts_scenario.dart
@@ -10,8 +10,8 @@ class AutoInstrumentAppStartsScenario extends Scenario {
     bugsnag_performance.setExtraConfig("probabilityValueExpireTime", 1000);
     bugsnag_performance.start(
         apiKey: '12312312312312312312312312312312',
-        endpoint: Uri.parse(FixtureConfig.MAZE_HOST.toString() + '/traces'));
-    bugsnag_performance.measureRunApp(() async => await Duration(seconds: 1));
+        endpoint: Uri.parse('${FixtureConfig.MAZE_HOST}/traces'));
+    bugsnag_performance.measureRunApp(() async => const Duration(seconds: 1));
     setMaxBatchSize(4);
   }
 }
diff --git a/features/fixture_resources/lib/scenarios/auto_instrument_navigation_basic_defer_scenario.dart b/features/fixture_resources/lib/scenarios/auto_instrument_navigation_basic_defer_scenario.dart
index 58c61b9..d50187d 100644
--- a/features/fixture_resources/lib/scenarios/auto_instrument_navigation_basic_defer_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/auto_instrument_navigation_basic_defer_scenario.dart
@@ -1,6 +1,5 @@
 import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'package:flutter/material.dart';
-import 'package:mazerunner/main.dart';
 
 import 'scenario.dart';
 
@@ -68,7 +67,7 @@ class _AutoInstrumentNavigationBasicDeferScenarioScreenState
         onTap: () => widget.runCommandCallback(),
       );
     }
-    return Text('AutoInstrumentNavigationBasicDeferScenarioScreen');
+    return const Text('AutoInstrumentNavigationBasicDeferScenarioScreen');
   }
 
   void setStage(int stage) {
diff --git a/features/fixture_resources/lib/scenarios/auto_instrument_navigation_basic_scenario.dart b/features/fixture_resources/lib/scenarios/auto_instrument_navigation_basic_scenario.dart
index 4c9f2f6..978b6e0 100644
--- a/features/fixture_resources/lib/scenarios/auto_instrument_navigation_basic_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/auto_instrument_navigation_basic_scenario.dart
@@ -1,7 +1,5 @@
-import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
-import 'package:mazerunner/main.dart';
 
 import 'scenario.dart';
 
@@ -15,11 +13,11 @@ class AutoInstrumentNavigationBasicScenario extends Scenario {
 
   @override
   Widget? createWidget() {
-    return Text('AutoInstrumentNavigationBasicScenario');
+    return const Text('AutoInstrumentNavigationBasicScenario');
   }
 
   @override
   RouteSettings? routeSettings() {
-    return RouteSettings(name: 'basic_navigation_scenario');
+    return const RouteSettings(name: 'basic_navigation_scenario');
   }
 }
diff --git a/features/fixture_resources/lib/scenarios/auto_instrument_navigation_complex_defer_scenario.dart b/features/fixture_resources/lib/scenarios/auto_instrument_navigation_complex_defer_scenario.dart
index 53536ca..64bb82d 100644
--- a/features/fixture_resources/lib/scenarios/auto_instrument_navigation_complex_defer_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/auto_instrument_navigation_complex_defer_scenario.dart
@@ -1,6 +1,5 @@
 import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'package:flutter/material.dart';
-import 'package:mazerunner/main.dart';
 
 import 'scenario.dart';
 
diff --git a/features/fixture_resources/lib/scenarios/auto_instrument_navigation_nested_navigation_scenario.dart b/features/fixture_resources/lib/scenarios/auto_instrument_navigation_nested_navigation_scenario.dart
index 1803414..d6bd7db 100644
--- a/features/fixture_resources/lib/scenarios/auto_instrument_navigation_nested_navigation_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/auto_instrument_navigation_nested_navigation_scenario.dart
@@ -1,7 +1,6 @@
 import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 
 import 'package:flutter/material.dart';
-import 'package:mazerunner/main.dart';
 
 import 'scenario.dart';
 
diff --git a/features/fixture_resources/lib/scenarios/auto_instrument_navigation_push_and_pop_scenario.dart b/features/fixture_resources/lib/scenarios/auto_instrument_navigation_push_and_pop_scenario.dart
index d52f5d7..3b1a964 100644
--- a/features/fixture_resources/lib/scenarios/auto_instrument_navigation_push_and_pop_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/auto_instrument_navigation_push_and_pop_scenario.dart
@@ -1,6 +1,4 @@
-import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'package:flutter/material.dart';
-import 'package:mazerunner/main.dart';
 
 import 'scenario.dart';
 
@@ -62,8 +60,8 @@ class AutoInstrumentNavigationPushAndPopScenarioScreenState
   Widget build(BuildContext context) {
     return GestureDetector(
       child: Container(
-        child: Text('AutoInstrumentNavigationPushAndPopScenarioScreen'),
         color: Colors.white,
+        child: Text('AutoInstrumentNavigationPushAndPopScenarioScreen'),
       ),
       onTap: () => widget.runCommandCallback(),
     );
diff --git a/features/fixture_resources/lib/scenarios/auto_instrument_navigation_with_view_load_scenario.dart b/features/fixture_resources/lib/scenarios/auto_instrument_navigation_with_view_load_scenario.dart
index cfe573b..cbc3fef 100644
--- a/features/fixture_resources/lib/scenarios/auto_instrument_navigation_with_view_load_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/auto_instrument_navigation_with_view_load_scenario.dart
@@ -1,6 +1,5 @@
 import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'package:flutter/material.dart';
-import 'package:mazerunner/main.dart';
 
 import 'scenario.dart';
 
diff --git a/features/fixture_resources/lib/scenarios/correlation_null_scenario.dart b/features/fixture_resources/lib/scenarios/correlation_null_scenario.dart
index d30a150..f490897 100644
--- a/features/fixture_resources/lib/scenarios/correlation_null_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/correlation_null_scenario.dart
@@ -1,6 +1,5 @@
 import 'package:bugsnag_flutter/bugsnag_flutter.dart';
 import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
-import 'package:mazerunner/main.dart';
 
 import 'scenario.dart';
 
diff --git a/features/fixture_resources/lib/scenarios/correlation_simple_scenario.dart b/features/fixture_resources/lib/scenarios/correlation_simple_scenario.dart
index e2f2f03..45d1f43 100644
--- a/features/fixture_resources/lib/scenarios/correlation_simple_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/correlation_simple_scenario.dart
@@ -1,6 +1,5 @@
 import 'package:bugsnag_flutter/bugsnag_flutter.dart';
 import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
-import 'package:mazerunner/main.dart';
 
 import 'scenario.dart';
 
diff --git a/features/fixture_resources/lib/scenarios/custom_app_version_scenario.dart b/features/fixture_resources/lib/scenarios/custom_app_version_scenario.dart
index e4c3874..0f3ce10 100644
--- a/features/fixture_resources/lib/scenarios/custom_app_version_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/custom_app_version_scenario.dart
@@ -1,4 +1,3 @@
-import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'scenario.dart';
 
 class CustomAppVersionScenario extends Scenario {
diff --git a/features/fixture_resources/lib/scenarios/custom_enabled_release_stage_scenario.dart b/features/fixture_resources/lib/scenarios/custom_enabled_release_stage_scenario.dart
index c9677c3..8e6cef2 100644
--- a/features/fixture_resources/lib/scenarios/custom_enabled_release_stage_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/custom_enabled_release_stage_scenario.dart
@@ -1,4 +1,3 @@
-import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'scenario.dart';
 
 class CustomEnabledReleaseStageScenario extends Scenario {
diff --git a/features/fixture_resources/lib/scenarios/custom_release_stage_scenario.dart b/features/fixture_resources/lib/scenarios/custom_release_stage_scenario.dart
index 6a521c9..93e0ac7 100644
--- a/features/fixture_resources/lib/scenarios/custom_release_stage_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/custom_release_stage_scenario.dart
@@ -1,4 +1,3 @@
-import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'scenario.dart';
 
 class CustomReleaseStageScenario extends Scenario {
diff --git a/features/fixture_resources/lib/scenarios/custom_service_name_scenario.dart b/features/fixture_resources/lib/scenarios/custom_service_name_scenario.dart
index d217547..54484b2 100644
--- a/features/fixture_resources/lib/scenarios/custom_service_name_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/custom_service_name_scenario.dart
@@ -1,4 +1,3 @@
-import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'scenario.dart';
 
 class CustomServiceNameScenario extends Scenario {
diff --git a/features/fixture_resources/lib/scenarios/custom_span_attributes_scenario.dart b/features/fixture_resources/lib/scenarios/custom_span_attributes_scenario.dart
new file mode 100644
index 0000000..36e542e
--- /dev/null
+++ b/features/fixture_resources/lib/scenarios/custom_span_attributes_scenario.dart
@@ -0,0 +1,49 @@
+import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
+
+import 'scenario.dart';
+
+class CustomSpanAttributesScenario extends Scenario {
+  @override
+  Future<void> run() async {
+    await startBugsnag(onSpanEndCallbacks: [
+      _setAttributesAndThrow,
+      _discardUnwantedSpan,
+      _setAttributes,
+    ]);
+    setMaxBatchSize(1);
+    doSimpleSpan('CustomSpanAttributesScenarioDiscaredSpan');
+    final span =
+        bugsnag_performance.startSpan('CustomSpanAttributesScenarioSpan');
+    span.setAttribute('customAttribute1', 42);
+    span.setAttribute('customAttribute2', 'Test');
+    span.setAttribute('customAttribute3', 1);
+    span.end();
+    span.setAttribute('customAttribute6', 'T');
+  }
+
+  Future<bool> _setAttributesAndThrow(BugsnagPerformanceSpan span) async {
+    span.setAttribute('customAttribute1', 'C');
+    throw Exception('');
+  }
+
+  Future<bool> _discardUnwantedSpan(BugsnagPerformanceSpan span) async {
+    if (span.name == 'CustomSpanAttributesScenarioDiscaredSpan') {
+      return false;
+    }
+    return true;
+  }
+
+  Future<bool> _setAttributes(BugsnagPerformanceSpan span) async {
+    span.setAttribute('customAttribute3', 2);
+    span.setAttribute('customAttribute3', 3);
+    span.setAttribute('customAttribute2', null);
+    span.setAttribute('customAttribute4', 42.0);
+    span.setAttribute('customAttribute5', [
+      'customString',
+      42,
+      true,
+      43.0,
+    ]);
+    return true;
+  }
+}
diff --git a/features/fixture_resources/lib/scenarios/custom_span_attributes_with_limits_scenario.dart b/features/fixture_resources/lib/scenarios/custom_span_attributes_with_limits_scenario.dart
new file mode 100644
index 0000000..bd103fb
--- /dev/null
+++ b/features/fixture_resources/lib/scenarios/custom_span_attributes_with_limits_scenario.dart
@@ -0,0 +1,35 @@
+import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
+
+import 'scenario.dart';
+
+class CustomSpanAttributesWithLimitsScenario extends Scenario {
+  @override
+  Future<void> run() async {
+    await startBugsnag(
+        attributeCountLimit: 8,
+        attributeStringValueLimit: 20,
+        attributeArrayLengthLimit: 6,
+        onSpanEndCallbacks: [
+          _setAttributes,
+        ]);
+    setMaxBatchSize(1);
+    final span = bugsnag_performance
+        .startSpan('CustomSpanAttributesWithLimitsScenarioSpan');
+    final tooLongKey = 'a' * 129;
+    span.setAttribute('customAttribute1', 42);
+    span.setAttribute(tooLongKey, 'Test');
+    span.setAttribute('customAttribute2', 1);
+    span.setAttribute('customAttribute3', [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
+    span.setAttribute(
+        'customAttribute4', 'VeryLongStringAttributeValueThatExceedsTheLimit');
+    span.setAttribute('customAttribute5', 42.0);
+    span.setAttribute('customAttribute6', 'Dropped');
+    span.end();
+  }
+
+  Future<bool> _setAttributes(BugsnagPerformanceSpan span) async {
+    span.setAttribute('customAttribute7', 'Droppedtoo');
+    span.setAttribute('customAttribute2', 'NotDropped');
+    return true;
+  }
+}
diff --git a/features/fixture_resources/lib/scenarios/dio_callback_cancel_span.dart b/features/fixture_resources/lib/scenarios/dio_callback_cancel_span.dart
index 6424be0..24a1e3a 100644
--- a/features/fixture_resources/lib/scenarios/dio_callback_cancel_span.dart
+++ b/features/fixture_resources/lib/scenarios/dio_callback_cancel_span.dart
@@ -1,5 +1,4 @@
 import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
-import 'package:bugsnag_http_client/bugsnag_http_client.dart';
 import 'package:dio/io.dart';
 import '../main.dart';
 import 'scenario.dart';
diff --git a/features/fixture_resources/lib/scenarios/dio_callback_edit_scenario.dart b/features/fixture_resources/lib/scenarios/dio_callback_edit_scenario.dart
index 1e74cbf..53f8741 100644
--- a/features/fixture_resources/lib/scenarios/dio_callback_edit_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/dio_callback_edit_scenario.dart
@@ -1,5 +1,4 @@
 import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
-import 'package:bugsnag_http_client/bugsnag_http_client.dart';
 import 'package:dio/io.dart';
 import '../main.dart';
 import 'scenario.dart';
diff --git a/features/fixture_resources/lib/scenarios/disable_custom_release_stage_scenario.dart b/features/fixture_resources/lib/scenarios/disable_custom_release_stage_scenario.dart
index da25733..14a4be9 100644
--- a/features/fixture_resources/lib/scenarios/disable_custom_release_stage_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/disable_custom_release_stage_scenario.dart
@@ -1,4 +1,3 @@
-import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'scenario.dart';
 
 class DisableCustomReleaseStageScenario extends Scenario {
diff --git a/features/fixture_resources/lib/scenarios/http_client_trace_propagation_urls_scenario.dart b/features/fixture_resources/lib/scenarios/http_client_trace_propagation_urls_scenario.dart
index fc79e20..9422159 100644
--- a/features/fixture_resources/lib/scenarios/http_client_trace_propagation_urls_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/http_client_trace_propagation_urls_scenario.dart
@@ -11,7 +11,7 @@ class HttpClientTracePropagationUrlsScenario extends Scenario {
     http.addSubscriber(bugsnag_performance.networkInstrumentation);
     http.get(
         Uri.parse('${FixtureConfig.MAZE_HOST.toString()}/reflect?dontsend'));
-    await Future.delayed(Duration(seconds: 1));
+    await Future.delayed(const Duration(seconds: 1));
     http.get(Uri.parse('${FixtureConfig.MAZE_HOST.toString()}/reflect?dosend'));
   }
 }
diff --git a/features/fixture_resources/lib/scenarios/initial_p_scenario.dart b/features/fixture_resources/lib/scenarios/initial_p_scenario.dart
index 6ae46e7..5b3f768 100644
--- a/features/fixture_resources/lib/scenarios/initial_p_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/initial_p_scenario.dart
@@ -1,10 +1,7 @@
-import 'dart:convert';
-
 import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'package:mazerunner/main.dart';
 
 import 'scenario.dart';
-import 'package:http/http.dart' as http;
 
 class InitialPScenario extends Scenario {
   @override
@@ -15,7 +12,7 @@ class InitialPScenario extends Scenario {
     bugsnag_performance.setExtraConfig("probabilityValueExpireTime", 25000);
     bugsnag_performance.start(
         apiKey: '12312312312312312312312312312312',
-        endpoint: Uri.parse(FixtureConfig.MAZE_HOST.toString() + '/traces'));
+        endpoint: Uri.parse('${FixtureConfig.MAZE_HOST}/traces'));
     setMaxBatchSize(1);
     doSimpleSpan('First');
   }
diff --git a/features/fixture_resources/lib/scenarios/manual_span_scenario.dart b/features/fixture_resources/lib/scenarios/manual_span_scenario.dart
index e1774b8..36a4252 100644
--- a/features/fixture_resources/lib/scenarios/manual_span_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/manual_span_scenario.dart
@@ -1,4 +1,3 @@
-import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'scenario.dart';
 
 class ManualSpanScenario extends Scenario {
diff --git a/features/fixture_resources/lib/scenarios/max_batch_age_scenario.dart b/features/fixture_resources/lib/scenarios/max_batch_age_scenario.dart
index 4ecc680..9db1e24 100644
--- a/features/fixture_resources/lib/scenarios/max_batch_age_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/max_batch_age_scenario.dart
@@ -1,4 +1,3 @@
-import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'scenario.dart';
 
 class MaxBatchAgeScenario extends Scenario {
diff --git a/features/fixture_resources/lib/scenarios/probability_expiry_scenario.dart b/features/fixture_resources/lib/scenarios/probability_expiry_scenario.dart
index f38996d..228cd8c 100644
--- a/features/fixture_resources/lib/scenarios/probability_expiry_scenario.dart
+++ b/features/fixture_resources/lib/scenarios/probability_expiry_scenario.dart
@@ -1,10 +1,7 @@
-import 'dart:convert';
-
 import 'package:bugsnag_flutter_performance/bugsnag_flutter_performance.dart';
 import 'package:mazerunner/main.dart';
 
 import 'scenario.dart';
-import 'package:http/http.dart' as http;
 
 class ProbabilityExpiryScenario extends Scenario {
   @override
@@ -14,9 +11,9 @@ class ProbabilityExpiryScenario extends Scenario {
     bugsnag_performance.setExtraConfig("probabilityValueExpireTime", 100);
     bugsnag_performance.start(
         apiKey: '12312312312312312312312312312312',
-        endpoint: Uri.parse(FixtureConfig.MAZE_HOST.toString() + '/traces'));
+        endpoint: Uri.parse('${FixtureConfig.MAZE_HOST}/traces'));
     setMaxBatchSize(1);
-    await Future.delayed(Duration(milliseconds: 500));
+    await Future.delayed(const Duration(milliseconds: 500));
     doSimpleSpan('myspan');
   }
 }
diff --git a/features/fixture_resources/lib/scenarios/scenario.dart b/features/fixture_resources/lib/scenarios/scenario.dart
index bc0c3d2..c8406e4 100644
--- a/features/fixture_resources/lib/scenarios/scenario.dart
+++ b/features/fixture_resources/lib/scenarios/scenario.dart
@@ -49,6 +49,10 @@ abstract class Scenario {
     String? appVersion,
     bool shouldUseNotifier = false,
     double? samplingProbability,
+    int? attributeCountLimit,
+    int? attributeStringValueLimit,
+    int? attributeArrayLengthLimit,
+    List<Future<bool> Function(BugsnagPerformanceSpan)>? onSpanEndCallbacks,
   }) async {
     bugsnag_performance.setExtraConfig("instrumentAppStart", false);
     bugsnag_performance.setExtraConfig("probabilityValueExpireTime", 1000);
@@ -61,6 +65,10 @@ abstract class Scenario {
       serviceName: serviceName,
       appVersion: appVersion,
       samplingProbability: samplingProbability,
+      attributeCountLimit: attributeCountLimit,
+      attributeStringValueLimit: attributeStringValueLimit,
+      attributeArrayLengthLimit: attributeArrayLengthLimit,
+      onSpanEndCallbacks: onSpanEndCallbacks,
     );
     if (shouldUseNotifier && endpointConfiguration != null) {
       await bugsnag.start(
diff --git a/features/fixture_resources/lib/scenarios/scenarios.dart b/features/fixture_resources/lib/scenarios/scenarios.dart
index bb0c40f..2a69a3a 100644
--- a/features/fixture_resources/lib/scenarios/scenarios.dart
+++ b/features/fixture_resources/lib/scenarios/scenarios.dart
@@ -9,6 +9,7 @@ import 'package:mazerunner/scenarios/auto_instrument_view_load_nested_scenario.d
 import 'package:mazerunner/scenarios/correlation_null_scenario.dart';
 import 'package:mazerunner/scenarios/correlation_simple_scenario.dart';
 import 'package:mazerunner/scenarios/custom_service_name_scenario.dart';
+import 'package:mazerunner/scenarios/custom_span_attributes_scenario.dart';
 import 'package:mazerunner/scenarios/dart_io_traceparent_scenario.dart';
 import 'package:mazerunner/scenarios/fixed_sampling_probability_one_scenario.dart';
 import 'package:mazerunner/scenarios/fixed_sampling_probability_zero_scenario.dart';
@@ -17,6 +18,7 @@ import 'package:mazerunner/scenarios/http_client_traceparent_scenario.dart';
 
 import 'auto_instrument_app_starts_scenario.dart';
 import 'auto_instrument_navigation_with_view_load_scenario.dart';
+import 'custom_span_attributes_with_limits_scenario.dart';
 import 'dio_callback_cancel_span.dart';
 import 'dio_callback_edit_scenario.dart';
 import 'initial_p_scenario.dart';
@@ -127,4 +129,8 @@ final List<ScenarioInfo<Scenario>> scenarios = [
   ScenarioInfo('FixedSamplingProbabilityZeroScenario',
       () => FixedSamplingProbabilityZeroScenario()),
   ScenarioInfo('CustomServiceNameScenario', () => CustomServiceNameScenario()),
+  ScenarioInfo(
+      'CustomSpanAttributesScenario', () => CustomSpanAttributesScenario()),
+  ScenarioInfo('CustomSpanAttributesWithLimitsScenario',
+      () => CustomSpanAttributesWithLimitsScenario())
 ];
diff --git a/features/manual_span.feature b/features/manual_span.feature
index 25c1f40..a436c85 100644
--- a/features/manual_span.feature
+++ b/features/manual_span.feature
@@ -51,7 +51,7 @@ Feature: Manual Spans
     * the span named "no-parent" exists
     * the span named "no-parent" has no parent
 
-Scenario: Manual Navigation Span
+  Scenario: Manual Navigation Span
     When I run "ManualNavigationSpanScenario"
     And I wait for 1 span
     Then the trace "Content-Type" header equals "application/json"
@@ -69,4 +69,60 @@ Scenario: Manual Navigation Span
     * every span string attribute "bugsnag.navigation.previous_route" equals "navigationScenarioPreviousRoute"
     * a span double attribute "bugsnag.sampling.p" equals 1.0
 
+  Scenario: Custom attributes
+    When I run "CustomSpanAttributesScenario"
+    And I wait for 1 span
+    Then the trace "Content-Type" header equals "application/json"
+    * the trace "Bugsnag-Sent-At" header matches the regex "^\d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d\.\d\d\dZ$"
+    * the trace "Bugsnag-Span-Sampling" header equals "1:1"
+    * every span field "name" equals "CustomSpanAttributesScenarioSpan"
+    * every span field "spanId" matches the regex "^[A-Fa-f0-9]{16}$"
+    * every span field "traceId" matches the regex "^[A-Fa-f0-9]{32}$"
+    * every span field "startTimeUnixNano" matches the regex "^[0-9]+$"
+    * every span field "endTimeUnixNano" matches the regex "^[0-9]+$"
+    * every span field "droppedAttributesCount" does not exist
+    * every span bool attribute "bugsnag.span.first_class" is true
+    * every span string attribute "bugsnag.span.category" equals "custom"
+    * a span double attribute "bugsnag.sampling.p" equals 1.0
+    * a span string attribute "customAttribute1" equals "C"
+    * every span string attribute "customAttribute2" does not exist
+    * a span integer attribute "customAttribute3" equals 3
+    * a span double attribute "customAttribute4" equals 42.0
+    * a span array attribute "customAttribute5" contains 4 items
+    * a span array attribute "customAttribute5" contains the string value "customString" at index 0
+    * a span array attribute "customAttribute5" contains the integer value 42 at index 1
+    * a span array attribute "customAttribute5" contains the value true at index 2
+    * a span array attribute "customAttribute5" contains the double value 43.0 at index 3
+    * every span string attribute "customAttribute6" does not exist
+
+  Scenario: Custom attributes - limits
+    When I run "CustomSpanAttributesWithLimitsScenario"
+    And I wait for 1 span
+    Then the trace "Content-Type" header equals "application/json"
+    * the trace "Bugsnag-Sent-At" header matches the regex "^\d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d\.\d\d\dZ$"
+    * the trace "Bugsnag-Span-Sampling" header equals "1:1"
+    * every span field "name" equals "CustomSpanAttributesWithLimitsScenarioSpan"
+    * every span field "spanId" matches the regex "^[A-Fa-f0-9]{16}$"
+    * every span field "traceId" matches the regex "^[A-Fa-f0-9]{32}$"
+    * every span field "startTimeUnixNano" matches the regex "^[0-9]+$"
+    * every span field "endTimeUnixNano" matches the regex "^[0-9]+$"
+    * every span field "droppedAttributesCount" equals 3
+    * every span bool attribute "bugsnag.span.first_class" is true
+    * every span string attribute "bugsnag.span.category" equals "custom"
+    * a span double attribute "bugsnag.sampling.p" equals 1.0
+    * a span integer attribute "customAttribute1" equals 42
+    * every span string attribute "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" does not exist
+    * a span string attribute "customAttribute2" equals "NotDropped"
+    * a span array attribute "customAttribute3" contains 6 items
+    * a span array attribute "customAttribute3" contains the integer value 1 at index 0
+    * a span array attribute "customAttribute3" contains the integer value 2 at index 1
+    * a span array attribute "customAttribute3" contains the integer value 3 at index 2
+    * a span array attribute "customAttribute3" contains the integer value 4 at index 3
+    * a span array attribute "customAttribute3" contains the integer value 5 at index 4
+    * a span array attribute "customAttribute3" contains the integer value 6 at index 5
+    * a span string attribute "customAttribute4" equals "VeryLongStringAttrib*** 27 CHARS TRUNCATED"
+    * a span double attribute "customAttribute5" equals 42.0
+    * every span string attribute "customAttribute6" does not exist
+    * every span string attribute "customAttribute7" does not exist
+
 
diff --git a/features/steps/flutter_steps.rb b/features/steps/flutter_steps.rb
index e7f2b51..221825e 100644
--- a/features/steps/flutter_steps.rb
+++ b/features/steps/flutter_steps.rb
@@ -123,6 +123,13 @@ def execute_command(action, scenario_name)
   Maze.check.false(attribute_values.empty?)
 end
 
+Then('a span integer attribute {string} equals {int}') do |attribute, expected|
+  spans = spans_from_request_list(Maze::Server.list_for('traces'))
+  selected_attributes = spans.map { |span| span['attributes'].find { |a| a['key'].eql?(attribute) && a['value'].has_key?('intValue') } }.compact
+  attribute_values = selected_attributes.map { |a| a['value']['intValue'].to_i == expected }
+  Maze.check.false(attribute_values.empty?)
+end
+
 Then('a span double attribute {string} equals {float}') do |attribute, value|
   spans = spans_from_request_list(Maze::Server.list_for('traces'))
   selected_attributes = spans.map { |span| span['attributes'].find { |a| a['key'].eql?(attribute) && a['value'].has_key?('doubleValue') } }.compact
@@ -201,3 +208,67 @@ def execute_command(action, scenario_name)
 
   Maze.check.true(spans_with_name.length() == 0);
 end
+
+Then('every span field {string} does not exist') do |key|
+  spans = spans_from_request_list(Maze::Server.list_for('traces'))
+  spans.map { |span| Maze.check.nil span[key] }
+end
+
+Then('every span field {string} equals {int}') do |key, expected|
+  spans = spans_from_request_list(Maze::Server.list_for('traces'))
+  selected_keys = spans.map { |span| span[key] == expected }
+  Maze.check.not_includes selected_keys, false
+end
+
+Then('a span array attribute {string} contains the string value {string} at index {int}') do |attribute, expected, index|
+  value = get_array_value_at_index(attribute, index, 'stringValue')
+  Maze.check.true(value == expected)
+end
+
+Then('a span array attribute {string} contains the integer value {int} at index {int}') do |attribute, expected, index|
+  value = get_array_value_at_index(attribute, index, 'intValue')
+  Maze.check.true(value.to_i == expected)
+end
+
+Then('a span array attribute {string} contains the double value {float} at index {int}') do |attribute, expected, index|
+  value = get_array_value_at_index(attribute, index, 'doubleValue')
+  Maze.check.true(value == expected)
+end
+
+Then('a span array attribute {string} contains the value true at index {int}') do |attribute, index|
+  value = get_array_value_at_index(attribute, index, 'boolValue')
+  Maze.check.true(value == true)
+end
+
+Then('a span array attribute {string} contains the value false at index {int}') do |attribute, index|
+  value = get_array_value_at_index(attribute, index, 'boolValue')
+  Maze.check.true(value == false)
+end
+
+Then('a span array attribute {string} contains {int} items') do |attribute, length|
+  array = get_array_attribute_contents(attribute)
+  Maze.check.true(array.length() == length)
+end
+
+Then('a span array attribute {string} is empty') do |attribute|
+  array_contents = get_array_attribute_contents(attribute)
+  Maze.check.true(array_contents.empty?)
+end
+
+def get_array_value_at_index(attribute, index, type)
+  array = get_array_attribute_contents(attribute)
+  Maze.check.true(array.length() > index)
+  value = array[index]
+  Maze.check.true(value.has_key?(type))
+  return value[type]
+end
+
+def get_array_attribute_contents(attribute)
+  spans = spans_from_request_list(Maze::Server.list_for('traces'))
+  selected_attributes = spans.map { |span| span['attributes'].find { |a| a['key'].eql?(attribute) &&
+                                                                         a['value'].has_key?('arrayValue') &&
+                                                                         a['value']['arrayValue'].has_key?('values') } }.compact
+  array_attributes = selected_attributes.map { |a| a['value']['arrayValue']['values'] }
+  Maze.check.false(array_attributes.empty?)
+  return array_attributes[0]
+end
diff --git a/features/support/maze.buildkite.cfg b/features/support/maze.buildkite.cfg
new file mode 100644
index 0000000..c5bc182
--- /dev/null
+++ b/features/support/maze.buildkite.cfg
@@ -0,0 +1,3 @@
+--format=junit
+--out=reports
+--format=pretty
diff --git a/packages/bugsnag_flutter_performance/lib/bugsnag_flutter_performance.dart b/packages/bugsnag_flutter_performance/lib/bugsnag_flutter_performance.dart
index f24e91e..c630d14 100644
--- a/packages/bugsnag_flutter_performance/lib/bugsnag_flutter_performance.dart
+++ b/packages/bugsnag_flutter_performance/lib/bugsnag_flutter_performance.dart
@@ -44,6 +44,10 @@ class BugsnagPerformance {
     String? serviceName,
     String? appVersion,
     double? samplingProbability,
+    int? attributeCountLimit,
+    int? attributeStringValueLimit,
+    int? attributeArrayLengthLimit,
+    List<Future<bool> Function(BugsnagPerformanceSpan)>? onSpanEndCallbacks,
   }) {
     _validateApiKey(apiKey);
     return _client.start(
@@ -56,6 +60,10 @@ class BugsnagPerformance {
       serviceName: serviceName,
       appVersion: appVersion,
       samplingProbability: samplingProbability,
+      attributeCountLimit: attributeCountLimit,
+      attributeStringValueLimit: attributeStringValueLimit,
+      attributeArrayLengthLimit: attributeArrayLengthLimit,
+      onSpanEndCallbacks: onSpanEndCallbacks,
     );
   }
 
diff --git a/packages/bugsnag_flutter_performance/lib/src/client.dart b/packages/bugsnag_flutter_performance/lib/src/client.dart
index 7eb3260..98cea80 100644
--- a/packages/bugsnag_flutter_performance/lib/src/client.dart
+++ b/packages/bugsnag_flutter_performance/lib/src/client.dart
@@ -10,6 +10,7 @@ import 'package:bugsnag_flutter_performance/src/instrumentation/navigation/navig
 import 'package:bugsnag_flutter_performance/src/instrumentation/view_load/measured_widget_callbacks.dart';
 import 'package:bugsnag_flutter_performance/src/instrumentation/view_load/view_load_instrumentation.dart';
 import 'package:bugsnag_flutter_performance/src/span_attributes.dart';
+import 'package:bugsnag_flutter_performance/src/span_attributes_limits.dart';
 import 'package:bugsnag_flutter_performance/src/span_context.dart';
 import 'package:bugsnag_flutter_performance/src/uploader/package_builder.dart';
 import 'package:bugsnag_flutter_performance/src/uploader/retry_queue.dart';
@@ -27,6 +28,8 @@ import 'bugsnag_network_request_info.dart';
 import 'configuration.dart';
 import 'span.dart';
 
+typedef OnSpanEndCallback = Future<bool> Function(BugsnagPerformanceSpan);
+
 String _defaultEndpoint(String? apiKey) =>
     'https://${apiKey != null ? '$apiKey.' : ''}otlp.bugsnag.com/v1/traces';
 
@@ -40,6 +43,8 @@ abstract class BugsnagPerformanceClient {
     List<String>? enabledReleaseStages,
     String? serviceName,
     String? appVersion,
+    double? samplingProbability,
+    List<OnSpanEndCallback>? onSpanEndCallbacks,
   });
 
   Future<void> measureRunApp(FutureOr<void> Function() runApp);
@@ -89,6 +94,7 @@ class BugsnagPerformanceClientImpl implements BugsnagPerformanceClient {
   RetryQueue? _retryQueue;
   Sampler? _sampler;
   DateTime? _lastSamplingProbabilityRefreshDate;
+  List<OnSpanEndCallback> _onSpanEndCallbacks = [];
   late final PackageBuilder _packageBuilder;
   late final BugsnagClock _clock;
   late final BugsnagLifecycleListener? _lifecycleListener;
@@ -136,6 +142,10 @@ class BugsnagPerformanceClientImpl implements BugsnagPerformanceClient {
     String? serviceName,
     String? appVersion,
     double? samplingProbability,
+    int? attributeCountLimit,
+    int? attributeStringValueLimit,
+    int? attributeArrayLengthLimit,
+    List<OnSpanEndCallback>? onSpanEndCallbacks,
   }) async {
     if (!_isEnabledOnCurrentPlatform()) {
       _appStartInstrumentation.setEnabled(false);
@@ -144,6 +154,12 @@ class BugsnagPerformanceClientImpl implements BugsnagPerformanceClient {
     }
     WidgetsFlutterBinding.ensureInitialized();
     _networkRequestCallback = networkRequestCallback;
+    _onSpanEndCallbacks = onSpanEndCallbacks ?? [];
+    BugsnagPerformanceSpanImpl.globalAttributeCountLimit =
+        SpanAttributesLimits.limitValue(
+      type: SpanAttributesLimitType.attributeCountLimit,
+      providedValue: attributeCountLimit,
+    );
     configuration = BugsnagPerformanceConfiguration(
       apiKey: apiKey,
       endpoint: endpoint ?? Uri.parse(_defaultEndpoint(apiKey)),
@@ -153,7 +169,21 @@ class BugsnagPerformanceClientImpl implements BugsnagPerformanceClient {
       serviceName: serviceName,
       appVersion: appVersion,
       samplingProbability: samplingProbability,
+      attributeCountLimit: SpanAttributesLimits.limitValue(
+        type: SpanAttributesLimitType.attributeCountLimit,
+        providedValue: attributeCountLimit,
+      ),
+      attributeStringValueLimit: SpanAttributesLimits.limitValue(
+        type: SpanAttributesLimitType.stringValueLimit,
+        providedValue: attributeStringValueLimit,
+      ),
+      attributeArrayLengthLimit: SpanAttributesLimits.limitValue(
+        type: SpanAttributesLimitType.arrayLengthLimit,
+        providedValue: attributeArrayLengthLimit,
+      ),
     );
+    BugsnagPerformanceSpanImpl.globalAttributeCountLimit =
+        configuration!.attributeCountLimit;
     _packageBuilder.setConfig(configuration);
     _initialExtraConfig.forEach((key, value) {
       setExtraConfig(key, value);
@@ -200,7 +230,8 @@ class BugsnagPerformanceClientImpl implements BugsnagPerformanceClient {
       startTime: startTime ?? _clock.now(),
       onEnded: (endedSpan) async {
         await _updateSamplingProbabilityIfNeeded();
-        if (await _sampler?.sample(endedSpan) ?? true) {
+        if ((await _sampler?.sample(endedSpan) ?? true) &&
+            (await _callOnSpanEndedCallbacks(endedSpan))) {
           _currentBatch?.add(endedSpan);
         }
         _potentiallyOpenSpans.remove(endedSpan.spanId);
@@ -211,6 +242,7 @@ class BugsnagPerformanceClientImpl implements BugsnagPerformanceClient {
       parentSpanId: parent?.spanId,
       traceId: parent?.traceId,
       attributes: attributes,
+      attributeCountLimit: configuration?.attributeCountLimit,
     );
     span.clock = _clock;
     if (configuration != null) {
@@ -540,4 +572,28 @@ class BugsnagPerformanceClientImpl implements BugsnagPerformanceClient {
   bool _isEnabledOnCurrentPlatform() {
     return !kIsWeb;
   }
+
+  Future<bool> _callOnSpanEndedCallbacks(BugsnagPerformanceSpan span) async {
+    if (span is BugsnagPerformanceSpanImpl) {
+      span.makeMutable(true);
+    }
+    try {
+      for (OnSpanEndCallback callback in _onSpanEndCallbacks) {
+        try {
+          if (!(await callback(span))) {
+            return false;
+          }
+        } catch (e) {
+          if (kDebugMode) {
+            print('onSpanEnd callback threw exception: $e');
+          }
+        }
+      }
+    } finally {
+      if (span is BugsnagPerformanceSpanImpl) {
+        span.makeMutable(false);
+      }
+    }
+    return true;
+  }
 }
diff --git a/packages/bugsnag_flutter_performance/lib/src/configuration.dart b/packages/bugsnag_flutter_performance/lib/src/configuration.dart
index 73103d4..7e963b4 100644
--- a/packages/bugsnag_flutter_performance/lib/src/configuration.dart
+++ b/packages/bugsnag_flutter_performance/lib/src/configuration.dart
@@ -8,6 +8,9 @@ class BugsnagPerformanceConfiguration {
     this.serviceName,
     this.appVersion,
     this.samplingProbability,
+    required this.attributeCountLimit,
+    required this.attributeStringValueLimit,
+    required this.attributeArrayLengthLimit,
   });
   String? apiKey;
   Uri? endpoint;
@@ -24,6 +27,9 @@ class BugsnagPerformanceConfiguration {
   String? serviceName;
   String? appVersion;
   double? samplingProbability;
+  int attributeCountLimit;
+  int attributeStringValueLimit;
+  int attributeArrayLengthLimit;
 
   bool releaseStageEnabled() {
     return releaseStage == null ||
diff --git a/packages/bugsnag_flutter_performance/lib/src/extensions/resource_attributes.dart b/packages/bugsnag_flutter_performance/lib/src/extensions/resource_attributes.dart
index 6b9146a..d94ba2d 100644
--- a/packages/bugsnag_flutter_performance/lib/src/extensions/resource_attributes.dart
+++ b/packages/bugsnag_flutter_performance/lib/src/extensions/resource_attributes.dart
@@ -196,5 +196,5 @@ class ResourceAttributesProviderImpl implements ResourceAttributesProvider {
     return "Unknown";
   }
 
-  static String get _getSDKVersion => '1.2.1';
+  static String get _getSDKVersion => '1.3.0';
 }
diff --git a/packages/bugsnag_flutter_performance/lib/src/span.dart b/packages/bugsnag_flutter_performance/lib/src/span.dart
index 5e3203f..3b150a0 100644
--- a/packages/bugsnag_flutter_performance/lib/src/span.dart
+++ b/packages/bugsnag_flutter_performance/lib/src/span.dart
@@ -1,9 +1,12 @@
+import 'package:bugsnag_flutter_performance/src/configuration.dart';
 import 'package:bugsnag_flutter_performance/src/extensions/date_time.dart';
 import 'package:bugsnag_flutter_performance/src/extensions/int.dart';
 import 'package:bugsnag_flutter_performance/src/span_attributes.dart';
+import 'package:bugsnag_flutter_performance/src/span_attributes_limits.dart';
 import 'package:bugsnag_flutter_performance/src/span_context.dart';
 import 'package:bugsnag_flutter_performance/src/util/clock.dart';
 import 'package:bugsnag_flutter_performance/src/util/random.dart';
+import 'package:flutter/foundation.dart';
 
 typedef TraceId = BigInt;
 typedef SpanId = BigInt;
@@ -23,7 +26,13 @@ abstract class BugsnagPerformanceSpan implements BugsnagPerformanceSpanContext {
   });
   String get encodedTraceId;
   String get encodedSpanId;
-  dynamic toJson();
+  String get name;
+  DateTime get startTime;
+  DateTime? get endTime;
+  void setAttribute(String key, dynamic value);
+  dynamic toJson({
+    BugsnagPerformanceConfiguration? config,
+  });
 }
 
 class BugsnagPerformanceSpanImpl
@@ -36,13 +45,20 @@ class BugsnagPerformanceSpanImpl
       TraceId? traceId,
       SpanId? spanId,
       this.parentSpanId,
+      int? attributeCountLimit,
       BugsnagPerformanceSpanAttributes? attributes}) {
     this.traceId = traceId ?? randomTraceId();
     this.spanId = spanId ?? randomSpanId();
     this.onEnded = onEnded ?? _onEnded;
     this.onCanceled = onCanceled ?? _onCanceled;
+    this.attributeCountLimit = attributeCountLimit ?? globalAttributeCountLimit;
     this.attributes = attributes ?? BugsnagPerformanceSpanAttributes();
   }
+
+  static int globalAttributeCountLimit = SpanAttributesLimits.limitValue(
+      type: SpanAttributesLimitType.attributeCountLimit);
+
+  @override
   final String name;
   @override
   late final TraceId traceId;
@@ -50,13 +66,19 @@ class BugsnagPerformanceSpanImpl
   late final SpanId spanId;
   @override
   SpanId? parentSpanId;
+  @override
   final DateTime startTime;
   late final BugsnagPerformanceSpanAttributes attributes;
-  DateTime? endTime;
+  DateTime? _endTime;
   var isSampled = false;
+  var _isMutable = true;
   late final void Function(BugsnagPerformanceSpan) onEnded;
   late final void Function(BugsnagPerformanceSpan) onCanceled;
   late final BugsnagClock clock;
+  late final int attributeCountLimit;
+  @override
+  DateTime? get endTime => _endTime;
+  var _droppedAttributesCountBeforeEncoding = 0;
 
   @override
   void end({
@@ -69,7 +91,8 @@ class BugsnagPerformanceSpanImpl
     if (!isOpen()) {
       return;
     }
-    this.endTime = endTime ?? clock.now();
+    _endTime = endTime ?? clock.now();
+    makeMutable(false);
     if (cancelled) {
       onCanceled(this);
       return;
@@ -85,11 +108,34 @@ class BugsnagPerformanceSpanImpl
     onEnded(this);
   }
 
+  @override
+  void setAttribute(String key, dynamic value) {
+    if (!_isMutable) {
+      if (kDebugMode) {
+        print(
+            'Span attribute "$key" in span $name was dropped as the span is no longer open');
+      }
+      return;
+    }
+    if (!attributes.hasAttribute(key) &&
+        value != null &&
+        attributes.count >= attributeCountLimit) {
+      _droppedAttributesCountBeforeEncoding++;
+      if (kDebugMode) {
+        print(
+            'Span attribute "$key" in span $name was dropped as the number of attributes exceeds the $attributeCountLimit attribute limit set by AttributeCountLimit.');
+      }
+      return;
+    }
+
+    attributes.setAttribute(key, value);
+  }
+
   BugsnagPerformanceSpanImpl.fromJson(Map<String, dynamic> json,
       [void Function(BugsnagPerformanceSpan)? onEnded])
       : startTime = int.parse(json['startTimeUnixNano']).timeFromNanos,
         name = json['name'] as String,
-        endTime = json['endTimeUnixNano'] != null
+        _endTime = json['endTimeUnixNano'] != null
             ? int.parse(json['endTimeUnixNano']).timeFromNanos
             : null,
         traceId = _decodeTraceId(json['traceId'] as String?) ?? randomTraceId(),
@@ -100,18 +146,27 @@ class BugsnagPerformanceSpanImpl
             BugsnagPerformanceSpanAttributes.fromJson(json['attributes']);
 
   @override
-  dynamic toJson() => {
-        'startTimeUnixNano': startTime.nanosecondsSinceEpoch.toString(),
-        'name': name,
-        if (endTime != null)
-          'endTimeUnixNano': endTime!.nanosecondsSinceEpoch.toString(),
-        'traceId': encodedTraceId,
-        'spanId': encodedSpanId,
-        'kind': 1,
-        if (parentSpanId != null)
-          'parentSpanId': _encodeSpanId(parentSpanId ?? BigInt.zero),
-        'attributes': attributes.toJson(),
-      };
+  dynamic toJson({
+    BugsnagPerformanceConfiguration? config,
+  }) {
+    final attributesEncodingResult = attributes.toJson(config: config);
+    final droppedAttributesCount = _droppedAttributesCountBeforeEncoding +
+        attributesEncodingResult.droppedAttributesCount;
+    return {
+      'startTimeUnixNano': startTime.nanosecondsSinceEpoch.toString(),
+      'name': name,
+      if (_endTime != null)
+        'endTimeUnixNano': _endTime!.nanosecondsSinceEpoch.toString(),
+      'traceId': encodedTraceId,
+      'spanId': encodedSpanId,
+      'kind': 1,
+      if (parentSpanId != null)
+        'parentSpanId': _encodeSpanId(parentSpanId ?? BigInt.zero),
+      'attributes': attributesEncodingResult.jsonValue,
+      if (droppedAttributesCount > 0)
+        'droppedAttributesCount': droppedAttributesCount,
+    };
+  }
 
   @override
   bool operator ==(Object other) =>
@@ -132,7 +187,7 @@ class BugsnagPerformanceSpanImpl
 
   @override
   bool isOpen() {
-    return endTime == null;
+    return _endTime == null;
   }
 
   @override
@@ -140,6 +195,10 @@ class BugsnagPerformanceSpanImpl
 
   @override
   String get encodedSpanId => _encodeSpanId(spanId);
+
+  void makeMutable(bool mutable) {
+    _isMutable = mutable;
+  }
 }
 
 String _encodeSpanId(SpanId spanId) {
diff --git a/packages/bugsnag_flutter_performance/lib/src/span_attributes.dart b/packages/bugsnag_flutter_performance/lib/src/span_attributes.dart
index 5330d5e..b031e43 100644
--- a/packages/bugsnag_flutter_performance/lib/src/span_attributes.dart
+++ b/packages/bugsnag_flutter_performance/lib/src/span_attributes.dart
@@ -1,3 +1,17 @@
+import 'package:bugsnag_flutter_performance/src/configuration.dart';
+import 'package:bugsnag_flutter_performance/src/span_attributes_limits.dart';
+import 'package:flutter/foundation.dart';
+
+class BugsnagPerformanceSpanAttributesEncodingResult {
+  final dynamic jsonValue;
+  final int droppedAttributesCount;
+
+  BugsnagPerformanceSpanAttributesEncodingResult({
+    required this.jsonValue,
+    required this.droppedAttributesCount,
+  });
+}
+
 class BugsnagPerformanceSpanAttributes {
   final Map<String, dynamic> attributes = {};
 
@@ -26,6 +40,8 @@ class BugsnagPerformanceSpanAttributes {
   void setAttribute(String key, dynamic value) {
     if (value != null) {
       attributes[key] = value;
+    } else {
+      attributes.remove(key);
     }
   }
 
@@ -49,44 +65,37 @@ class BugsnagPerformanceSpanAttributes {
     return attributes['bugsnag.sampling.p'];
   }
 
-  dynamic toJson() {
-    const typeMap = {
-      bool: 'boolValue',
-      double: 'doubleValue',
-      int: 'intValue',
-      String: 'stringValue',
-    };
+  int get count => attributes.length;
 
-    return attributes.entries.map((entry) {
-      final key = entry.key;
-      final value = entry.value;
-      String valueType = typeMap[value.runtimeType] ?? 'stringValue';
-      dynamic formattedValue = value is int ? value.toString() : value;
+  bool hasAttribute(String key) {
+    return attributes.containsKey(key);
+  }
 
-      return {
-        'key': key,
-        'value': {valueType: formattedValue},
-      };
-    }).toList();
+  BugsnagPerformanceSpanAttributesEncodingResult toJson({
+    BugsnagPerformanceConfiguration? config,
+  }) {
+    final attributeKeyLengthLimit = SpanAttributesLimits.limitValue(
+        type: SpanAttributesLimitType.keyLengthLimit);
+    final attributeStringValueLimit = config?.attributeStringValueLimit ??
+        SpanAttributesLimits.limitValue(
+            type: SpanAttributesLimitType.stringValueLimit);
+    final attributeArrayLengthLimit = config?.attributeArrayLengthLimit ??
+        SpanAttributesLimits.limitValue(
+            type: SpanAttributesLimitType.arrayLengthLimit);
+
+    return BugsnagPerformanceSpanAttributesEncoder(
+      attributeKeyLengthLimit: attributeKeyLengthLimit,
+      attributeStringValueLimit: attributeStringValueLimit,
+      attributeArrayLengthLimit: attributeArrayLengthLimit,
+    ).toJson(attributes);
   }
 
   factory BugsnagPerformanceSpanAttributes.fromJson(
       List<Map<String, dynamic>> json) {
     final attributes = <String, dynamic>{};
-    for (var element in json) {
+    for (final element in json) {
       final key = element['key'];
-      final Map<String, dynamic> valueMap = element['value'];
-      dynamic value;
-
-      if (valueMap.containsKey('stringValue')) {
-        value = valueMap['stringValue'];
-      } else if (valueMap.containsKey('boolValue')) {
-        value = valueMap['boolValue'];
-      } else if (valueMap.containsKey('doubleValue')) {
-        value = double.tryParse(valueMap['doubleValue'].toString());
-      } else if (valueMap.containsKey('intValue')) {
-        value = int.tryParse(valueMap['intValue']);
-      }
+      dynamic value = _decodeAttributeValue(element['value']);
 
       if (key != null && value != null) {
         attributes[key] = value;
@@ -94,4 +103,140 @@ class BugsnagPerformanceSpanAttributes {
     }
     return BugsnagPerformanceSpanAttributes(additionalAttributes: attributes);
   }
+
+  static dynamic _decodeAttributeValue(Map<String, dynamic> valueMap) {
+    if (valueMap.containsKey('stringValue')) {
+      return valueMap['stringValue'];
+    } else if (valueMap.containsKey('boolValue')) {
+      return valueMap['boolValue'];
+    } else if (valueMap.containsKey('doubleValue')) {
+      return double.tryParse(valueMap['doubleValue'].toString());
+    } else if (valueMap.containsKey('intValue')) {
+      return int.tryParse(valueMap['intValue']);
+    } else if (valueMap.containsKey('arrayValue')) {
+      final arrayValue = valueMap['arrayValue'];
+      if (arrayValue is Map<String, List> && arrayValue.containsKey('values')) {
+        List result = [];
+        for (final element in arrayValue['values']!) {
+          dynamic decodedValue = _decodeAttributeValue(element);
+          if (decodedValue != null) {
+            result.add(decodedValue);
+          }
+        }
+        return result;
+      }
+    }
+    return null;
+  }
+}
+
+class BugsnagPerformanceSpanAttributesEncoder {
+  int attributeKeyLengthLimit;
+  int attributeStringValueLimit;
+  int attributeArrayLengthLimit;
+
+  BugsnagPerformanceSpanAttributesEncoder({
+    required this.attributeKeyLengthLimit,
+    required this.attributeStringValueLimit,
+    required this.attributeArrayLengthLimit,
+  });
+
+  static const _typeMap = {
+    bool: 'boolValue',
+    double: 'doubleValue',
+    int: 'intValue',
+    String: 'stringValue'
+  };
+
+  static const _listTypeMap = {
+    List<bool>: 'arrayValue',
+    List<double>: 'arrayValue',
+    List<int>: 'arrayValue',
+    List<String>: 'arrayValue',
+    List<Object>: 'arrayValue'
+  };
+
+  BugsnagPerformanceSpanAttributesEncodingResult toJson(
+    Map<String, dynamic> attributes,
+  ) {
+    final validKeys =
+        attributes.keys.where((key) => key.length <= attributeKeyLengthLimit);
+
+    final jsonValue = validKeys.map((key) {
+      final value = attributes[key];
+
+      return {
+        'key': key,
+        'value': _encodeAttributeValue(key, value),
+      };
+    }).toList();
+
+    return BugsnagPerformanceSpanAttributesEncodingResult(
+      jsonValue: jsonValue,
+      droppedAttributesCount: attributes.length - validKeys.length,
+    );
+  }
+
+  dynamic _encodeAttributeValue(
+    String key,
+    dynamic value,
+  ) {
+    final runtimeType = value.runtimeType;
+    String valueType =
+        _typeMap[runtimeType] ?? _listTypeMap[runtimeType] ?? 'stringValue';
+    dynamic formattedValue = _formattedValue(key, value);
+    return {valueType: formattedValue};
+  }
+
+  dynamic _formattedValue(
+    String key,
+    dynamic value,
+  ) {
+    if (value is String) {
+      if (value.length > attributeStringValueLimit) {
+        if (kDebugMode) {
+          print(
+              'The value for span attribute "$key" was truncated as it exceeds the $attributeStringValueLimit attribute limit set by AttributeStringValueLimit');
+        }
+        return '${value.substring(0, attributeStringValueLimit)}*** ${value.length - attributeStringValueLimit} CHARS TRUNCATED';
+      }
+      return value;
+    }
+    if (value is int) {
+      return value.toString();
+    }
+    if (value is List) {
+      return _encodeListAttributeValue(key, value);
+    }
+    if (value is double || value is bool) {
+      return value;
+    }
+    return value.toString();
+  }
+
+  dynamic _encodeListAttributeValue(
+    String key,
+    List listAttribute,
+  ) {
+    List result = [];
+    for (final (index, value) in listAttribute.indexed) {
+      final runtimeType = value.runtimeType;
+      if (_typeMap[runtimeType] != null) {
+        result.add(_encodeAttributeValue(key, value));
+      } else {
+        if (kDebugMode) {
+          print(
+              'The element at index $index for span attribute "$key" was excluded as its type is not valid.');
+        }
+      }
+    }
+    if (result.length > attributeArrayLengthLimit) {
+      if (kDebugMode) {
+        print(
+            'The value for span attribute "$key" was truncated as it exceeds the $attributeArrayLengthLimit attribute limit set by AttributeArrayLengthLimit');
+      }
+      result = result.sublist(0, attributeArrayLengthLimit).toList();
+    }
+    return {'values': result};
+  }
 }
diff --git a/packages/bugsnag_flutter_performance/lib/src/span_attributes_limits.dart b/packages/bugsnag_flutter_performance/lib/src/span_attributes_limits.dart
new file mode 100644
index 0000000..aa8fdd7
--- /dev/null
+++ b/packages/bugsnag_flutter_performance/lib/src/span_attributes_limits.dart
@@ -0,0 +1,77 @@
+enum SpanAttributesLimitType {
+  keyLengthLimit,
+  stringValueLimit,
+  arrayLengthLimit,
+  attributeCountLimit,
+}
+
+class SpanAttributesLimits {
+  static const _attributeKeyLengthLimit = 128;
+
+  static const _defaultAttributeStringValueLimit = 1024;
+  static const _minAttributeStringValueLimit = 1;
+  static const _maxAttributeStringValueLimit = 10000;
+
+  static const _defaultAttributeArrayLengthLimit = 1000;
+  static const _minAttributeArrayLengthLimit = 1;
+  static const _maxAttributeArrayLengthLimit = 10000;
+
+  static const _defaultAttributeCountLimit = 128;
+  static const _minAttributeCountLimit = 1;
+  static const _maxAttributeCountLimit = 1000;
+
+  static int limitValue({
+    required SpanAttributesLimitType type,
+    int? providedValue,
+  }) {
+    if (providedValue == null) {
+      return _defaultValue(type);
+    }
+    if (providedValue < _minValue(type)) {
+      return _defaultValue(type);
+    }
+    if (providedValue > _maxValue(type)) {
+      return _maxValue(type);
+    }
+    return providedValue;
+  }
+
+  static int _defaultValue(SpanAttributesLimitType type) {
+    switch (type) {
+      case SpanAttributesLimitType.keyLengthLimit:
+        return _attributeKeyLengthLimit;
+      case SpanAttributesLimitType.stringValueLimit:
+        return _defaultAttributeStringValueLimit;
+      case SpanAttributesLimitType.arrayLengthLimit:
+        return _defaultAttributeArrayLengthLimit;
+      case SpanAttributesLimitType.attributeCountLimit:
+        return _defaultAttributeCountLimit;
+    }
+  }
+
+  static int _minValue(SpanAttributesLimitType type) {
+    switch (type) {
+      case SpanAttributesLimitType.keyLengthLimit:
+        return _attributeKeyLengthLimit;
+      case SpanAttributesLimitType.stringValueLimit:
+        return _minAttributeStringValueLimit;
+      case SpanAttributesLimitType.arrayLengthLimit:
+        return _minAttributeArrayLengthLimit;
+      case SpanAttributesLimitType.attributeCountLimit:
+        return _minAttributeCountLimit;
+    }
+  }
+
+  static int _maxValue(SpanAttributesLimitType type) {
+    switch (type) {
+      case SpanAttributesLimitType.keyLengthLimit:
+        return _attributeKeyLengthLimit;
+      case SpanAttributesLimitType.stringValueLimit:
+        return _maxAttributeStringValueLimit;
+      case SpanAttributesLimitType.arrayLengthLimit:
+        return _maxAttributeArrayLengthLimit;
+      case SpanAttributesLimitType.attributeCountLimit:
+        return _maxAttributeCountLimit;
+    }
+  }
+}
diff --git a/packages/bugsnag_flutter_performance/lib/src/uploader/package_builder.dart b/packages/bugsnag_flutter_performance/lib/src/uploader/package_builder.dart
index 2d5d259..63e8274 100644
--- a/packages/bugsnag_flutter_performance/lib/src/uploader/package_builder.dart
+++ b/packages/bugsnag_flutter_performance/lib/src/uploader/package_builder.dart
@@ -61,7 +61,7 @@ class PackageBuilderImpl implements PackageBuilder {
   Future<List<int>> _buildPayload({
     required List<BugsnagPerformanceSpan> spans,
   }) async {
-    final jsonList = spans.map((span) => span.toJson()).toList();
+    final jsonList = spans.map((span) => span.toJson(config: _config)).toList();
     final jsonRequest = {
       'resourceSpans': [
         {
diff --git a/packages/bugsnag_flutter_performance/lib/src/uploader/retry_queue.dart b/packages/bugsnag_flutter_performance/lib/src/uploader/retry_queue.dart
index 4881ca6..b4d70d2 100644
--- a/packages/bugsnag_flutter_performance/lib/src/uploader/retry_queue.dart
+++ b/packages/bugsnag_flutter_performance/lib/src/uploader/retry_queue.dart
@@ -44,8 +44,11 @@ class FileRetryQueue implements RetryQueue {
 
   final Uploader? _uploader;
   var _isFlushing = false;
+  final Directory? _cacheDirectory;
 
-  FileRetryQueue(Uploader uploader) : _uploader = uploader;
+  FileRetryQueue(Uploader uploader, {Directory? cacheDirectory})
+      : _uploader = uploader,
+        _cacheDirectory = cacheDirectory;
 
   @override
   Future<void> enqueue({
@@ -60,7 +63,7 @@ class FileRetryQueue implements RetryQueue {
 
   @override
   Future<void> flush() async {
-    final cacheDirectory = await _getCacheDirectory();
+    final cacheDirectory = _cacheDirectory ?? await _getCacheDirectory();
     if (_isFlushing || !cacheDirectory.existsSync()) {
       return;
     }
diff --git a/packages/bugsnag_flutter_performance/pubspec.yaml b/packages/bugsnag_flutter_performance/pubspec.yaml
index 6446555..ceece08 100644
--- a/packages/bugsnag_flutter_performance/pubspec.yaml
+++ b/packages/bugsnag_flutter_performance/pubspec.yaml
@@ -1,6 +1,6 @@
 name: bugsnag_flutter_performance
 description: BugSnag performance monitoring tool for Flutter apps
-version: 1.2.1
+version: 1.3.0
 homepage: https://www.bugsnag.com/
 documentation: https://docs.bugsnag.com/performance/flutter/
 repository: https://github.com/bugsnag/bugsnag-flutter-performance
@@ -26,6 +26,7 @@ dev_dependencies:
   flutter_test:
     sdk: flutter
   flutter_lints: ^2.0.0
+  path_provider_platform_interface: ^2.0.4
 
 flutter:
   # This section identifies this Flutter project as a plugin project.
diff --git a/packages/bugsnag_flutter_performance/test/src/span_test.dart b/packages/bugsnag_flutter_performance/test/src/span_test.dart
index 8db1a5f..ca70a9d 100644
--- a/packages/bugsnag_flutter_performance/test/src/span_test.dart
+++ b/packages/bugsnag_flutter_performance/test/src/span_test.dart
@@ -1,3 +1,4 @@
+import 'package:bugsnag_flutter_performance/src/configuration.dart';
 import 'package:bugsnag_flutter_performance/src/extensions/bugsnag_lifecycle_listener.dart';
 import 'package:bugsnag_flutter_performance/src/extensions/date_time.dart';
 import 'package:bugsnag_flutter_performance/src/extensions/int.dart';
@@ -127,6 +128,19 @@ void main() {
               'key': 'custom',
               'value': {'stringValue': 'value'}
             },
+            {
+              'key': 'customArray',
+              'value': {
+                'arrayValue': {
+                  'values': [
+                    {'stringValue': 'testValue'},
+                    {'intValue': '1'},
+                    {'doubleValue': 4.2},
+                    {'boolValue': true},
+                  ]
+                }
+              }
+            },
           ],
         };
         final span = BugsnagPerformanceSpanImpl.fromJson(json);
@@ -147,6 +161,14 @@ void main() {
             span.parentSpanId,
             equals(
                 BigInt.tryParse(json['parentSpanId'] as String, radix: 16)!));
+        expect(
+            span.attributes.attributes['customArray'],
+            equals([
+              'testValue',
+              1,
+              4.2,
+              true,
+            ]));
       });
 
       test('should decode a running span', () {
@@ -185,6 +207,9 @@ void main() {
           parentSpanId: randomSpanId(),
         );
         span.clock = BugsnagClockImpl.instance;
+        span.setAttribute('customString', 'testValue');
+        span.setAttribute('customInt', 2);
+        span.setAttribute('list', [42, 43.0, 'testString', false, true, 1]);
         span.end();
         final json = span.toJson();
         expect(json['name'], equals(span.name));
@@ -199,6 +224,40 @@ void main() {
             equals(span.spanId.toRadixString(16).padLeft(16, '0')));
         expect(json['parentSpanId'],
             equals(span.parentSpanId!.toRadixString(16).padLeft(16, '0')));
+        final attributes = json['attributes'] as List<Map<String, dynamic>>;
+        expect(
+          attributes[0],
+          equals({
+            'key': 'customString',
+            'value': {'stringValue': 'testValue'},
+          }),
+        );
+        expect(
+          attributes[1],
+          equals({
+            'key': 'customInt',
+            'value': {'intValue': '2'},
+          }),
+        );
+        expect(
+          attributes[2],
+          equals({
+            'key': 'list',
+            'value': {
+              'arrayValue': {
+                'values': [
+                  {'intValue': '42'},
+                  {'doubleValue': 43.0},
+                  {'stringValue': 'testString'},
+                  {'boolValue': false},
+                  {'boolValue': true},
+                  {'intValue': '1'},
+                ],
+              }
+            },
+          }),
+        );
+        expect(json['droppedAttributesCount'], isNull);
       });
 
       test('should encode a running span', () {
@@ -212,6 +271,117 @@ void main() {
         expect(int.parse(json['startTimeUnixNano']),
             equals(span.startTime.nanosecondsSinceEpoch));
         expect(json['endTimeUnixNano'], isNull);
+        expect(json['droppedAttributesCount'], isNull);
+      });
+
+      test('should drop attributes with too long keys', () {
+        const tooLongKey =
+            'trberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwc';
+        const tooLongKey2 =
+            'Atrbesfsdffrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwc';
+        final span = BugsnagPerformanceSpanImpl(
+            name: 'Test name',
+            startTime: DateTime.fromMillisecondsSinceEpoch(
+                millisecondsSinceEpoch,
+                isUtc: true));
+        span.clock = BugsnagClockImpl.instance;
+        span.setAttribute(tooLongKey, 'test');
+        span.setAttribute(tooLongKey2, 'test2');
+        span.setAttribute('TestBool', false);
+        span.end();
+        final json = span.toJson();
+        final attributes = json['attributes'] as List<Map<String, dynamic>>;
+        expect(attributes.length, equals(1));
+        expect(
+            attributes[0],
+            equals({
+              'key': 'TestBool',
+              'value': {'boolValue': false},
+            }));
+        expect(json['droppedAttributesCount'], equals(2));
+      });
+
+      test(
+          'should include attributes added over limit along with those with too long keys in droppedAttributesCount',
+          () {
+        const tooLongKey =
+            'trberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwc';
+        const tooLongKey2 =
+            'Atrbesfsdffrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwctrberwfqfrefwefrgrewfrfwefwftvrvwreqwcwc';
+        final span = BugsnagPerformanceSpanImpl(
+          name: 'Test name',
+          startTime: DateTime.fromMillisecondsSinceEpoch(millisecondsSinceEpoch,
+              isUtc: true),
+          attributeCountLimit: 3,
+        );
+        span.clock = BugsnagClockImpl.instance;
+        span.setAttribute('TestInt', 1);
+        span.setAttribute(tooLongKey, 'test');
+        span.setAttribute(tooLongKey2, 'test2');
+        span.setAttribute('TestBool', false);
+        span.setAttribute('TestBool2', true);
+        span.setAttribute('TestInt', 2);
+        span.setAttribute('TestInt', 3);
+        span.end();
+        final json = span.toJson();
+        final attributes = json['attributes'] as List<Map<String, dynamic>>;
+        expect(attributes.length, equals(1));
+        expect(
+            attributes[0],
+            equals({
+              'key': 'TestInt',
+              'value': {'intValue': '3'},
+            }));
+        expect(json['droppedAttributesCount'], equals(4));
+      });
+
+      test('should truncate strings and arrays that go over the limits', () {
+        final span = BugsnagPerformanceSpanImpl(
+          name: 'Test name',
+          startTime: DateTime.fromMillisecondsSinceEpoch(millisecondsSinceEpoch,
+              isUtc: true),
+        );
+        span.clock = BugsnagClockImpl.instance;
+        span.setAttribute('TestString', 'test');
+        span.setAttribute('LongTestString', 'This is a very long string');
+        span.setAttribute('TestArray', [true, '2', 3.0, 4, '5', 6.0, 7]);
+        span.end();
+        final config = BugsnagPerformanceConfiguration(
+          attributeCountLimit: 100,
+          attributeStringValueLimit: 10,
+          attributeArrayLengthLimit: 4,
+        );
+        final json = span.toJson(config: config);
+        final attributes = json['attributes'] as List<Map<String, dynamic>>;
+        expect(attributes.length, equals(3));
+        expect(
+            attributes[0],
+            equals({
+              'key': 'TestString',
+              'value': {'stringValue': 'test'},
+            }));
+        expect(
+            attributes[1],
+            equals({
+              'key': 'LongTestString',
+              'value': {'stringValue': 'This is a *** 16 CHARS TRUNCATED'},
+            }));
+        expect(
+            attributes[2],
+            equals({
+              'key': 'TestArray',
+              'value': {
+                'arrayValue': {
+                  'values': [
+                    {'boolValue': true},
+                    {'stringValue': '2'},
+                    {'doubleValue': 3.0},
+                    {'intValue': '4'}
+                  ],
+                }
+              },
+            }));
+        expect(json['droppedAttributesCount'], isNull);
       });
     });
   });
diff --git a/packages/bugsnag_flutter_performance/test/src/uploader/retry_queue_test.dart b/packages/bugsnag_flutter_performance/test/src/uploader/retry_queue_test.dart
new file mode 100644
index 0000000..d8df958
--- /dev/null
+++ b/packages/bugsnag_flutter_performance/test/src/uploader/retry_queue_test.dart
@@ -0,0 +1,123 @@
+import 'dart:convert';
+import 'dart:io';
+import 'dart:typed_data';
+import 'package:bugsnag_flutter_performance/src/uploader/model/otlp_package.dart';
+import 'package:bugsnag_flutter_performance/src/util/clock.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:path_provider/path_provider.dart';
+import 'package:path_provider_platform_interface/path_provider_platform_interface.dart';
+import 'package:bugsnag_flutter_performance/src/uploader/uploader.dart';
+import 'package:bugsnag_flutter_performance/src/uploader/retry_queue.dart';
+
+class TestUploader implements Uploader {
+  final RequestResult resultToReturn;
+  final bool throwError;
+
+  TestUploader({this.resultToReturn = RequestResult.success, this.throwError = false});
+
+  @override
+  Future<RequestResult> upload({required OtlpPackage package}) async {
+    if (throwError) {
+      throw Exception('Upload error');
+    }
+    return resultToReturn;
+  }
+}
+
+class MockPathProviderPlatform extends PathProviderPlatform {
+  @override
+  Future<String?> getApplicationSupportPath() async {
+    final directory = await Directory.systemTemp.createTemp('bugsnag_test');
+    return directory.path;
+  }
+}
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  group('FileRetryQueue', () {
+    late FileRetryQueue retryQueue;
+    late TestUploader testUploader;
+    late Directory mockCacheDirectory;
+
+    setUp(() async {
+      BugsnagClockImpl.ensureInitialized();
+      PathProviderPlatform.instance = MockPathProviderPlatform();
+      final supportDir = await getApplicationSupportDirectory();
+      final mockCachePath = '${supportDir.path}/bugsnag-performance/v1/batches';
+      mockCacheDirectory = Directory(mockCachePath);
+      await mockCacheDirectory.create(recursive: true);
+
+    });
+
+    tearDown(() async {
+      if (await mockCacheDirectory.exists()) {
+        await mockCacheDirectory.delete(recursive: true);
+      }
+    });
+
+    test('should delete the file after successful upload', () async {
+      // Setup uploader to return success
+      testUploader = TestUploader(resultToReturn: RequestResult.success);
+      retryQueue = FileRetryQueue(testUploader, cacheDirectory: mockCacheDirectory);
+
+      // Create a valid payload file
+      final fileName = '${mockCacheDirectory.path}/payload_success.json';
+      final file = File(fileName);
+      final payloadModel = CachedPayloadModel(headers: {}, body: Uint8List(0));
+      await file.writeAsString(jsonEncode(payloadModel.toJson()));
+
+      await retryQueue.flush();
+
+      // Ensure the file is deleted after flush
+      expect(await file.exists(), isFalse);
+    });
+
+    test('should not delete the file after failed upload', () async {
+      // Setup uploader to return failure
+      testUploader = TestUploader(resultToReturn: RequestResult.retriableFailure);
+      retryQueue = FileRetryQueue(testUploader, cacheDirectory: mockCacheDirectory);
+
+      // Create a valid payload file
+      final fileName = '${mockCacheDirectory.path}/payload_failure.json';
+      final file = File(fileName);
+      final payloadModel = CachedPayloadModel(headers: {}, body: Uint8List(0));
+      await file.writeAsString(jsonEncode(payloadModel.toJson()));
+
+      await retryQueue.flush();
+
+      // Ensure the file is not deleted after flush
+      expect(await file.exists(), isTrue);
+    });
+
+    test('should handle malformed JSON and delete the file', () async {
+      testUploader = TestUploader();
+      retryQueue = FileRetryQueue(testUploader, cacheDirectory: mockCacheDirectory);
+      // Create a file with malformed JSON
+      final fileName = '${mockCacheDirectory.path}/malformed_payload.json';
+      final file = File(fileName);
+      await file.writeAsString('malformed_json');
+
+      await retryQueue.flush();
+
+      // Ensure the file is deleted after flush
+      expect(await file.exists(), isFalse);
+    });
+
+    test('should delete files older than 24 hours', () async {
+      testUploader = TestUploader();
+      retryQueue = FileRetryQueue(testUploader, cacheDirectory: mockCacheDirectory);
+      // Create a file older than 24 hours
+      final oldTimestamp = BugsnagClockImpl.instance.now().subtract(const Duration(hours: 25));
+      final fileName = '${mockCacheDirectory.path}/old_payload.json';
+      final file = File(fileName);
+      await file.writeAsString('{"headers": {}, "body": ""}');
+      file.setLastModifiedSync(oldTimestamp);
+
+      await retryQueue.flush();
+
+      // Ensure the file is deleted after flush
+      expect(file.existsSync(), isFalse);
+    });
+  });
+}
diff --git a/packages/bugsnag_flutter_performance/test/src/uploader/span_batch_test.dart b/packages/bugsnag_flutter_performance/test/src/uploader/span_batch_test.dart
index b657621..684014f 100644
--- a/packages/bugsnag_flutter_performance/test/src/uploader/span_batch_test.dart
+++ b/packages/bugsnag_flutter_performance/test/src/uploader/span_batch_test.dart
@@ -1,5 +1,6 @@
 import 'package:bugsnag_flutter_performance/src/configuration.dart';
 import 'package:bugsnag_flutter_performance/src/span.dart';
+import 'package:bugsnag_flutter_performance/src/span_attributes_limits.dart';
 import 'package:bugsnag_flutter_performance/src/uploader/span_batch.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -32,7 +33,14 @@ void main() {
 
       setUp(() {
         batch.configure(
-          BugsnagPerformanceConfiguration()..maxBatchSize = batchSize,
+          BugsnagPerformanceConfiguration(
+            attributeCountLimit: SpanAttributesLimits.limitValue(
+                type: SpanAttributesLimitType.attributeCountLimit),
+            attributeStringValueLimit: SpanAttributesLimits.limitValue(
+                type: SpanAttributesLimitType.stringValueLimit),
+            attributeArrayLengthLimit: SpanAttributesLimits.limitValue(
+                type: SpanAttributesLimitType.arrayLengthLimit),
+          )..maxBatchSize = batchSize,
         );
       });