diff --git a/veilid-flutter/build.sh b/veilid-flutter/build.sh
index 1f08284e..2a765035 100755
--- a/veilid-flutter/build.sh
+++ b/veilid-flutter/build.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 set -e
-dart run build_runner build
+dart run build_runner build --delete-conflicting-outputs
diff --git a/veilid-flutter/lib/routing_context.dart b/veilid-flutter/lib/routing_context.dart
index 5060e98e..e5cde3fa 100644
--- a/veilid-flutter/lib/routing_context.dart
+++ b/veilid-flutter/lib/routing_context.dart
@@ -123,7 +123,7 @@ class ValueData with _$ValueData {
   @Assert('seq >= 0', 'seq out of range')
   const factory ValueData({
     required int seq,
-    @Uint8ListJsonConverter() required Uint8List data,
+    @Uint8ListJsonConverter.jsIsArray() required Uint8List data,
     required PublicKey writer,
   }) = _ValueData;
 
diff --git a/veilid-flutter/lib/routing_context.freezed.dart b/veilid-flutter/lib/routing_context.freezed.dart
index 140c2214..af4f4aab 100644
--- a/veilid-flutter/lib/routing_context.freezed.dart
+++ b/veilid-flutter/lib/routing_context.freezed.dart
@@ -969,7 +969,7 @@ ValueData _$ValueDataFromJson(Map<String, dynamic> json) {
 /// @nodoc
 mixin _$ValueData {
   int get seq => throw _privateConstructorUsedError;
-  @Uint8ListJsonConverter()
+  @Uint8ListJsonConverter.jsIsArray()
   Uint8List get data => throw _privateConstructorUsedError;
   FixedEncodedString43 get writer => throw _privateConstructorUsedError;
 
@@ -986,7 +986,7 @@ abstract class $ValueDataCopyWith<$Res> {
   @useResult
   $Res call(
       {int seq,
-      @Uint8ListJsonConverter() Uint8List data,
+      @Uint8ListJsonConverter.jsIsArray() Uint8List data,
       FixedEncodedString43 writer});
 }
 
@@ -1033,7 +1033,7 @@ abstract class _$$_ValueDataCopyWith<$Res> implements $ValueDataCopyWith<$Res> {
   @useResult
   $Res call(
       {int seq,
-      @Uint8ListJsonConverter() Uint8List data,
+      @Uint8ListJsonConverter.jsIsArray() Uint8List data,
       FixedEncodedString43 writer});
 }
 
@@ -1074,7 +1074,7 @@ class __$$_ValueDataCopyWithImpl<$Res>
 class _$_ValueData implements _ValueData {
   const _$_ValueData(
       {required this.seq,
-      @Uint8ListJsonConverter() required this.data,
+      @Uint8ListJsonConverter.jsIsArray() required this.data,
       required this.writer})
       : assert(seq >= 0, 'seq out of range');
 
@@ -1084,7 +1084,7 @@ class _$_ValueData implements _ValueData {
   @override
   final int seq;
   @override
-  @Uint8ListJsonConverter()
+  @Uint8ListJsonConverter.jsIsArray()
   final Uint8List data;
   @override
   final FixedEncodedString43 writer;
@@ -1126,7 +1126,7 @@ class _$_ValueData implements _ValueData {
 abstract class _ValueData implements ValueData {
   const factory _ValueData(
       {required final int seq,
-      @Uint8ListJsonConverter() required final Uint8List data,
+      @Uint8ListJsonConverter.jsIsArray() required final Uint8List data,
       required final FixedEncodedString43 writer}) = _$_ValueData;
 
   factory _ValueData.fromJson(Map<String, dynamic> json) =
@@ -1135,7 +1135,7 @@ abstract class _ValueData implements ValueData {
   @override
   int get seq;
   @override
-  @Uint8ListJsonConverter()
+  @Uint8ListJsonConverter.jsIsArray()
   Uint8List get data;
   @override
   FixedEncodedString43 get writer;
diff --git a/veilid-flutter/lib/routing_context.g.dart b/veilid-flutter/lib/routing_context.g.dart
index da5aa313..d76ff703 100644
--- a/veilid-flutter/lib/routing_context.g.dart
+++ b/veilid-flutter/lib/routing_context.g.dart
@@ -80,14 +80,14 @@ Map<String, dynamic> _$$_ValueSubkeyRangeToJson(_$_ValueSubkeyRange instance) =>
 
 _$_ValueData _$$_ValueDataFromJson(Map<String, dynamic> json) => _$_ValueData(
       seq: json['seq'] as int,
-      data: const Uint8ListJsonConverter().fromJson(json['data'] as String),
+      data: const Uint8ListJsonConverter.jsIsArray().fromJson(json['data']),
       writer: FixedEncodedString43.fromJson(json['writer']),
     );
 
 Map<String, dynamic> _$$_ValueDataToJson(_$_ValueData instance) =>
     <String, dynamic>{
       'seq': instance.seq,
-      'data': const Uint8ListJsonConverter().toJson(instance.data),
+      'data': const Uint8ListJsonConverter.jsIsArray().toJson(instance.data),
       'writer': instance.writer.toJson(),
     };
 
@@ -109,7 +109,7 @@ Map<String, dynamic> _$$_SafetySpecToJson(_$_SafetySpec instance) =>
 
 _$_RouteBlob _$$_RouteBlobFromJson(Map<String, dynamic> json) => _$_RouteBlob(
       routeId: json['route_id'] as String,
-      blob: const Uint8ListJsonConverter().fromJson(json['blob'] as String),
+      blob: const Uint8ListJsonConverter().fromJson(json['blob']),
     );
 
 Map<String, dynamic> _$$_RouteBlobToJson(_$_RouteBlob instance) =>
diff --git a/veilid-flutter/lib/veilid_encoding.dart b/veilid-flutter/lib/veilid_encoding.dart
index 7962dbc5..5022bd84 100644
--- a/veilid-flutter/lib/veilid_encoding.dart
+++ b/veilid-flutter/lib/veilid_encoding.dart
@@ -1,9 +1,13 @@
 import 'dart:convert';
-import 'dart:typed_data';
 
 import 'package:equatable/equatable.dart';
+import 'package:flutter/foundation.dart';
 import 'package:freezed_annotation/freezed_annotation.dart';
 
+import 'veilid_stub.dart'
+    if (dart.library.io) 'veilid_ffi.dart'
+    if (dart.library.js) 'veilid_js.dart';
+
 String base64UrlNoPadEncode(List<int> bytes) {
   var x = base64Url.encode(bytes);
   while (x.endsWith('=')) {
@@ -20,13 +24,20 @@ Uint8List base64UrlNoPadDecode(String source) {
 Uint8List base64UrlNoPadDecodeDynamic(dynamic source) =>
     base64UrlNoPadDecode(source as String);
 
-class Uint8ListJsonConverter implements JsonConverter<Uint8List, String> {
-  const Uint8ListJsonConverter();
+class Uint8ListJsonConverter implements JsonConverter<Uint8List, dynamic> {
+  const Uint8ListJsonConverter() : _jsIsArray = false;
+  const Uint8ListJsonConverter.jsIsArray() : _jsIsArray = true;
+
+  final bool _jsIsArray;
 
   @override
-  Uint8List fromJson(dynamic json) => base64UrlNoPadDecode(json as String);
+  Uint8List fromJson(dynamic json) => kIsWeb && _jsIsArray
+      ? convertUint8ListFromJson(json)
+      : base64UrlNoPadDecode(json as String);
   @override
-  String toJson(Uint8List data) => base64UrlNoPadEncode(data);
+  dynamic toJson(Uint8List data) => kIsWeb && _jsIsArray
+      ? convertUint8ListToJson(data)
+      : base64UrlNoPadEncode(data);
 }
 
 @immutable
diff --git a/veilid-flutter/lib/veilid_ffi.dart b/veilid-flutter/lib/veilid_ffi.dart
index cf899832..373c653e 100644
--- a/veilid-flutter/lib/veilid_ffi.dart
+++ b/veilid-flutter/lib/veilid_ffi.dart
@@ -246,6 +246,11 @@ const int messageStreamClose = 8;
 // Interface factory for high level Veilid API
 Veilid getVeilid() => VeilidFFI(_dylib);
 
+// Uint8List marshaling
+Uint8List convertUint8ListFromJson(dynamic json) =>
+    base64UrlNoPadDecode(json as String);
+dynamic convertUint8ListToJson(Uint8List data) => base64UrlNoPadEncode(data);
+
 // Parse handle async returns
 Future<T> processFuturePlain<T>(Future<dynamic> future) async =>
     future.then((value) {
diff --git a/veilid-flutter/lib/veilid_js.dart b/veilid-flutter/lib/veilid_js.dart
index 3ef1f283..e7e3d223 100644
--- a/veilid-flutter/lib/veilid_js.dart
+++ b/veilid-flutter/lib/veilid_js.dart
@@ -2,6 +2,7 @@ import 'dart:async';
 import 'dart:convert';
 import 'dart:html' as html;
 import 'dart:js' as js;
+import 'dart:js_interop' as js_interop;
 import 'dart:js_util' as js_util;
 import 'dart:typed_data';
 
@@ -13,14 +14,26 @@ Veilid getVeilid() => VeilidJS();
 
 Object wasm = js_util.getProperty(html.window, 'veilid_wasm');
 
+Uint8List convertUint8ListFromJson(dynamic json) => Uint8List.fromList(
+    ((json as js_interop.JSArray).dartify()! as List<Object?>)
+        .map((e) => e! as int)
+        .toList());
+
+dynamic convertUint8ListToJson(Uint8List data) => data.toList().jsify();
+
 Future<T> _wrapApiPromise<T>(Object p) => js_util
         .promiseToFuture<T>(p)
         .then((value) => value)
         // ignore: inference_failure_on_untyped_parameter
         .catchError((e) {
-      // Wrap all other errors in VeilidAPIExceptionInternal
-      throw VeilidAPIExceptionInternal(e.toString());
-    }, test: (e) => e is! VeilidAPIException);
+      try {
+        final ex = VeilidAPIException.fromJson(jsonDecode(e as String));
+        throw ex;
+      } on Exception catch (_) {
+        // Wrap all other errors in VeilidAPIExceptionInternal
+        throw VeilidAPIExceptionInternal(e.toString());
+      }
+    });
 
 class _Ctx {
   _Ctx(int id, this.js) : _id = id;
@@ -142,7 +155,11 @@ class VeilidRoutingContextJS extends VeilidRoutingContext {
         wasm,
         'routing_context_get_dht_value',
         [id, jsonEncode(key), subkey, forceRefresh]));
-    return opt == null ? null : ValueData.fromJson(jsonDecode(opt));
+    if (opt == null) {
+      return null;
+    }
+    final jsonOpt = jsonDecode(opt);
+    return jsonOpt == null ? null : ValueData.fromJson(jsonOpt);
   }
 
   @override
@@ -153,7 +170,11 @@ class VeilidRoutingContextJS extends VeilidRoutingContext {
         wasm,
         'routing_context_set_dht_value',
         [id, jsonEncode(key), subkey, base64UrlNoPadEncode(data)]));
-    return opt == null ? null : ValueData.fromJson(jsonDecode(opt));
+    if (opt == null) {
+      return null;
+    }
+    final jsonOpt = jsonDecode(opt);
+    return jsonOpt == null ? null : ValueData.fromJson(jsonOpt);
   }
 
   @override
diff --git a/veilid-flutter/lib/veilid_state.g.dart b/veilid-flutter/lib/veilid_state.g.dart
index d3797e28..8ed1eb66 100644
--- a/veilid-flutter/lib/veilid_state.g.dart
+++ b/veilid-flutter/lib/veilid_state.g.dart
@@ -129,8 +129,7 @@ Map<String, dynamic> _$$VeilidLogToJson(_$VeilidLog instance) =>
 
 _$VeilidAppMessage _$$VeilidAppMessageFromJson(Map<String, dynamic> json) =>
     _$VeilidAppMessage(
-      message:
-          const Uint8ListJsonConverter().fromJson(json['message'] as String),
+      message: const Uint8ListJsonConverter().fromJson(json['message']),
       sender: json['sender'] == null
           ? null
           : Typed<FixedEncodedString43>.fromJson(json['sender']),
@@ -146,8 +145,7 @@ Map<String, dynamic> _$$VeilidAppMessageToJson(_$VeilidAppMessage instance) =>
 
 _$VeilidAppCall _$$VeilidAppCallFromJson(Map<String, dynamic> json) =>
     _$VeilidAppCall(
-      message:
-          const Uint8ListJsonConverter().fromJson(json['message'] as String),
+      message: const Uint8ListJsonConverter().fromJson(json['message']),
       callId: json['call_id'] as String,
       sender: json['sender'] == null
           ? null
diff --git a/veilid-flutter/lib/veilid_stub.dart b/veilid-flutter/lib/veilid_stub.dart
index 1606518d..639cbe15 100644
--- a/veilid-flutter/lib/veilid_stub.dart
+++ b/veilid-flutter/lib/veilid_stub.dart
@@ -1,3 +1,9 @@
+import 'dart:typed_data';
+
 import 'veilid.dart';
 
 Veilid getVeilid() => throw UnsupportedError('Cannot create Veilid object');
+Uint8List convertUint8ListFromJson(dynamic json) =>
+    throw UnsupportedError('Cannot convertUint8ListFromJson');
+dynamic convertUint8ListToJson(Uint8List data) =>
+    throw UnsupportedError('Cannot convertUint8ListToJson');
diff --git a/veilid-wasm/src/lib.rs b/veilid-wasm/src/lib.rs
index 1521640c..05d7ae25 100644
--- a/veilid-wasm/src/lib.rs
+++ b/veilid-wasm/src/lib.rs
@@ -345,11 +345,14 @@ pub fn release_routing_context(id: u32) -> i32 {
 
 #[wasm_bindgen()]
 pub fn routing_context_with_privacy(id: u32) -> u32 {
-    let rc = (*ROUTING_CONTEXTS).borrow();
-    let Some(routing_context) = rc.get(&id) else {
-        return 0;
+    let routing_context = {
+        let rc = (*ROUTING_CONTEXTS).borrow();
+        let Some(routing_context) = rc.get(&id) else {
+            return 0;
+        };
+        routing_context.clone()
     };
-    let Ok(routing_context) = routing_context.clone().with_privacy() else {
+    let Ok(routing_context) = routing_context.with_privacy() else {
         return 0;
     };
     add_routing_context(routing_context)
@@ -360,14 +363,14 @@ pub fn routing_context_with_custom_privacy(id: u32, safety_selection: String) ->
     let safety_selection: veilid_core::SafetySelection =
         veilid_core::deserialize_json(&safety_selection).unwrap();
 
-    let rc = (*ROUTING_CONTEXTS).borrow();
-    let Some(routing_context) = rc.get(&id) else {
-        return 0;
+    let routing_context = {
+        let rc = (*ROUTING_CONTEXTS).borrow();
+        let Some(routing_context) = rc.get(&id) else {
+            return 0;
+        };
+        routing_context.clone()
     };
-    let Ok(routing_context) = routing_context
-        .clone()
-        .with_custom_privacy(safety_selection)
-    else {
+    let Ok(routing_context) = routing_context.with_custom_privacy(safety_selection) else {
         return 0;
     };
     add_routing_context(routing_context)
@@ -377,11 +380,14 @@ pub fn routing_context_with_custom_privacy(id: u32, safety_selection: String) ->
 pub fn routing_context_with_sequencing(id: u32, sequencing: String) -> u32 {
     let sequencing: veilid_core::Sequencing = veilid_core::deserialize_json(&sequencing).unwrap();
 
-    let rc = (*ROUTING_CONTEXTS).borrow();
-    let Some(routing_context) = rc.get(&id) else {
-        return 0;
+    let routing_context = {
+        let rc = (*ROUTING_CONTEXTS).borrow();
+        let Some(routing_context) = rc.get(&id) else {
+            return 0;
+        };
+        routing_context.clone()
     };
-    let routing_context = routing_context.clone().with_sequencing(sequencing);
+    let routing_context = routing_context.with_sequencing(sequencing);
     add_routing_context(routing_context)
 }
 
@@ -1544,8 +1550,8 @@ pub fn crypto_crypt_no_auth(
 }
 
 #[wasm_bindgen()]
-pub fn now() -> u64 {
-    veilid_core::get_aligned_timestamp().as_u64()
+pub fn now() -> String {
+    veilid_core::get_aligned_timestamp().as_u64().to_string()
 }
 
 #[wasm_bindgen()]