diff --git a/lib/src/shared/protocol.dart b/lib/src/shared/protocol.dart
index d2abe6dd..ae05f7f5 100644
--- a/lib/src/shared/protocol.dart
+++ b/lib/src/shared/protocol.dart
@@ -10,7 +10,9 @@ import 'transport.dart';
 final _logger = Logger("mcp_dart.shared.protocol");
 
 bool _isProgressToken(Object? token) =>
-    token is String || (token is num && token.isFinite);
+    token is String ||
+    token is int ||
+    (token is double && token.isFinite && token == token.truncateToDouble());
 
 const Set<String> _statelessCacheableResultMethods = {
   Method.toolsList,
@@ -204,7 +206,7 @@ class RequestHandlerExtra {
     if (!_isProgressToken(progressToken)) {
       _logger.warn(
         "Invalid progressToken type: ${progressToken.runtimeType}. "
-        "Expected string or finite number.",
+        "Expected string or integer.",
       );
       return;
     }
@@ -1428,7 +1430,7 @@ abstract class Protocol {
       _onerror(
         ArgumentError(
           "Received invalid progressToken: $progressToken. "
-          "Expected string or finite number.",
+          "Expected string or integer.",
         ),
       );
       return;
@@ -1650,7 +1652,7 @@ abstract class Protocol {
         if (!_isProgressToken(requestedProgressToken)) {
           return Future.error(
             ArgumentError(
-              'progressToken must be a string or finite number when '
+              'progressToken must be a string or integer when '
               'onprogress is set.',
             ),
           );
diff --git a/lib/src/shared/transport.dart b/lib/src/shared/transport.dart
index 1cfddae3..2011775e 100644
--- a/lib/src/shared/transport.dart
+++ b/lib/src/shared/transport.dart
@@ -45,14 +45,14 @@ abstract class Transport {
 }
 
 /// Optional capability for transports that can preserve JSON-RPC request IDs
-/// with their full MCP shape (string or finite number) for request/stream
+/// with their full MCP shape (string or integer) for request/stream
 /// correlation.
 ///
 /// Existing custom transports can keep implementing [Transport.send] with
 /// `int? relatedRequestId`. Transports that need to route messages by string
 /// request IDs should also implement this interface.
 abstract class RequestIdAwareTransport {
-  /// Sends a JSON-RPC message while preserving a string-or-number request ID.
+  /// Sends a JSON-RPC message while preserving a string-or-integer request ID.
   Future<void> sendWithRequestId(
     JsonRpcMessage message, {
     RequestId? relatedRequestId,
diff --git a/lib/src/types/json_rpc.dart b/lib/src/types/json_rpc.dart
index 107b325e..c64fa063 100644
--- a/lib/src/types/json_rpc.dart
+++ b/lib/src/types/json_rpc.dart
@@ -158,7 +158,7 @@ typedef ProgressToken = dynamic;
 
 /// Parses a wire progress token.
 ///
-/// MCP progress tokens are JSON strings or finite numbers. Reject malformed wire
+/// MCP progress tokens are JSON strings or integers. Reject malformed wire
 /// shapes at decode boundaries instead of allowing dynamic values to leak into
 /// higher-level protocol code.
 ProgressToken parseProgressToken(
@@ -168,11 +168,12 @@ ProgressToken parseProgressToken(
   if (value is String) {
     return value;
   }
-  if (value is num && value.isFinite) {
-    return value;
+  final integer = readOptionalInteger(value, fieldName);
+  if (integer != null) {
+    return integer;
   }
   throw FormatException(
-    'Invalid $fieldName: expected string or finite number, '
+    'Invalid $fieldName: expected string or integer, '
     'got ${value.runtimeType}',
   );
 }
@@ -185,18 +186,19 @@ typedef RequestId = dynamic;
 
 /// Parses a JSON-RPC request identifier.
 ///
-/// JSON-RPC/MCP request IDs are JSON strings or finite numbers for SDK request
+/// JSON-RPC/MCP request IDs are JSON strings or integers for SDK request
 /// boundaries. Notifications omit the `id` member entirely, and responses may
 /// omit the `id` member for JSON-RPC error cases.
 RequestId parseRequestId(Object? value, {String fieldName = 'id'}) {
   if (value is String) {
     return value;
   }
-  if (value is num && value.isFinite) {
-    return value;
+  final integer = readOptionalInteger(value, fieldName);
+  if (integer != null) {
+    return integer;
   }
   throw FormatException(
-    'Invalid $fieldName: expected string or finite number, '
+    'Invalid $fieldName: expected string or integer, '
     'got ${value.runtimeType}',
   );
 }
@@ -293,8 +295,8 @@ void validateMetaKeyName(String key, {String fieldName = '_meta'}) {
 
 /// Validates request metadata that can affect protocol behavior.
 ///
-/// `_meta.progressToken` is an MCP wire token and must be a string or finite
-/// number when present. [validateKeys] opts in to the MCP 2026 `_meta`
+/// `_meta.progressToken` is an MCP wire token and must be a string or integer
+/// when present. [validateKeys] opts in to the MCP 2026 `_meta`
 /// key-name grammar without changing stable/legacy request parsing.
 Map<String, dynamic>? validateRequestMeta(
   Map<String, dynamic>? meta, {
@@ -508,7 +510,10 @@ class JsonRpcRequest extends JsonRpcMessage {
             if (params != null)
               ...readJsonObject(params, 'JsonRpcRequest.params'),
             if (meta != null)
-              '_meta': readJsonObject(meta, 'JsonRpcRequest._meta'),
+              '_meta': readJsonObject(
+                validateRequestMeta(meta),
+                'JsonRpcRequest._meta',
+              ),
           },
       };
 }
diff --git a/packages/mcp_dart_cli/README.md b/packages/mcp_dart_cli/README.md
index 6e0c56ea..73534f3d 100644
--- a/packages/mcp_dart_cli/README.md
+++ b/packages/mcp_dart_cli/README.md
@@ -127,7 +127,7 @@ The CLI supports `sampling/createMessage` requests from the server (often used b
 
 ### Conformance
 
-Run built-in fixture checks, MCP 2025-11-25 spec-critical checks, and deterministic fuzz checks for MCP protocol edge cases. The fixture suite covers JSON-RPC malformed-message handling, string and numeric request IDs, string and numeric progress tokens, and advertised protocol-version support. The spec suite covers raw-wire lifecycle, capability, elicitation, task-metadata, and progress-token dispatch and negative cases.
+Run built-in fixture checks, MCP 2025-11-25 spec-critical checks, and deterministic fuzz checks for MCP protocol edge cases. The fixture suite covers JSON-RPC malformed-message handling, string and integer request IDs, string and integer progress tokens, fractional ID/token rejection, and advertised protocol-version support. The spec suite covers raw-wire lifecycle, capability, elicitation, task-metadata, and progress-token dispatch and negative cases.
 
 ```bash
 # Run all built-in fixture cases
diff --git a/packages/mcp_dart_cli/lib/src/conformance_runner.dart b/packages/mcp_dart_cli/lib/src/conformance_runner.dart
index 403f4f9b..ae720994 100644
--- a/packages/mcp_dart_cli/lib/src/conformance_runner.dart
+++ b/packages/mcp_dart_cli/lib/src/conformance_runner.dart
@@ -140,10 +140,10 @@ class ConformanceRunner {
           ),
           _ConformanceCase(
             suite: _fixtureSuite,
-            name: 'jsonrpc.preserves-numeric-response-id',
+            name: 'jsonrpc.preserves-integer-response-id',
             description:
-                'Parses and serializes successful responses with numeric JSON-RPC IDs.',
-            check: _preservesNumericResponseId,
+                'Parses and serializes successful responses with integer JSON-RPC IDs.',
+            check: _preservesIntegerResponseId,
           ),
           _ConformanceCase(
             suite: _fixtureSuite,
@@ -154,10 +154,17 @@ class ConformanceRunner {
           ),
           _ConformanceCase(
             suite: _fixtureSuite,
-            name: 'jsonrpc.preserves-numeric-progress-token',
+            name: 'jsonrpc.preserves-integer-progress-token',
             description:
-                'Parses and serializes progress notifications with numeric progress tokens.',
-            check: _preservesNumericProgressToken,
+                'Parses and serializes progress notifications with integer progress tokens.',
+            check: _preservesIntegerProgressToken,
+          ),
+          _ConformanceCase(
+            suite: _fixtureSuite,
+            name: 'jsonrpc.rejects-fractional-ids-and-progress-tokens',
+            description:
+                'Rejects fractional JSON-RPC request IDs, response IDs, and progress tokens.',
+            check: _rejectsFractionalIdsAndProgressTokens,
           ),
           _ConformanceCase(
             suite: _fixtureSuite,
@@ -200,15 +207,15 @@ class ConformanceRunner {
             suite: _specSuite,
             name: 'progress.rejects-malformed-progress-token',
             description:
-                'Rejects progress notifications whose progressToken is not a string or finite number.',
+                'Rejects progress notifications whose progressToken is not a string or integer.',
             check: _rejectsMalformedProgressToken,
           ),
           _ConformanceCase(
             suite: _specSuite,
-            name: 'progress.dispatches-numeric-progress-token',
+            name: 'progress.dispatches-integer-progress-token',
             description:
-                'Dispatches progress notifications for finite numeric progress tokens.',
-            check: _dispatchesNumericProgressToken,
+                'Dispatches progress notifications for integer progress tokens.',
+            check: _dispatchesIntegerProgressToken,
           ),
         ];
 
@@ -338,12 +345,9 @@ class _GeneratedJsonRpcFixture {
 }
 
 _GeneratedJsonRpcFixture _generatedJsonRpcFixture(Random random, int index) {
-  final numericId = random.nextInt(1000000);
-  final numericIdValue =
-      random.nextBool() ? numericId : numericId + random.nextDouble();
+  final integerId = random.nextInt(1000000);
   final stringId = 'req-${random.nextInt(1000000)}';
-  final progressToken =
-      random.nextBool() ? numericIdValue : 'progress-$numericId';
+  final progressToken = random.nextBool() ? integerId : 'progress-$integerId';
 
   return switch (random.nextInt(6)) {
     0 => _GeneratedJsonRpcFixture(
@@ -352,7 +356,7 @@ _GeneratedJsonRpcFixture _generatedJsonRpcFixture(Random random, int index) {
             'Generated request with an invalid JSON-RPC version is rejected.',
         message: <String, dynamic>{
           'jsonrpc': '2.${random.nextInt(9) + 1}',
-          'id': random.nextBool() ? numericId : stringId,
+          'id': random.nextBool() ? integerId : stringId,
           'method': Method.ping,
         },
         expectation: _expectFormatExceptionForPayload,
@@ -363,27 +367,27 @@ _GeneratedJsonRpcFixture _generatedJsonRpcFixture(Random random, int index) {
             'Generated JSON-RPC envelope without request/response members is rejected.',
         message: <String, dynamic>{
           'jsonrpc': jsonRpcVersion,
-          'id': random.nextBool() ? numericId : stringId,
+          'id': random.nextBool() ? integerId : stringId,
           'params': <String, dynamic>{'noise': random.nextInt(100)},
         },
         expectation: _expectFormatExceptionForPayload,
       ),
     2 => _GeneratedJsonRpcFixture(
         name: 'fuzz.jsonrpc.request-id.$index',
-        description: 'Generated requests preserve string-or-number IDs.',
+        description: 'Generated requests preserve string-or-integer IDs.',
         message: <String, dynamic>{
           'jsonrpc': jsonRpcVersion,
-          'id': random.nextBool() ? numericIdValue : stringId,
+          'id': random.nextBool() ? integerId : stringId,
           'method': Method.ping,
         },
         expectation: _expectRequestIdRoundTrip,
       ),
     3 => _GeneratedJsonRpcFixture(
         name: 'fuzz.jsonrpc.response-id.$index',
-        description: 'Generated responses preserve string-or-number IDs.',
+        description: 'Generated responses preserve string-or-integer IDs.',
         message: <String, dynamic>{
           'jsonrpc': jsonRpcVersion,
-          'id': random.nextBool() ? numericIdValue : stringId,
+          'id': random.nextBool() ? integerId : stringId,
           'result': <String, dynamic>{},
         },
         expectation: _expectResponseIdRoundTrip,
@@ -391,7 +395,7 @@ _GeneratedJsonRpcFixture _generatedJsonRpcFixture(Random random, int index) {
     4 => _GeneratedJsonRpcFixture(
         name: 'fuzz.jsonrpc.progress-token.$index',
         description:
-            'Generated progress notifications preserve string-or-number progress tokens.',
+            'Generated progress notifications preserve string-or-integer progress tokens.',
         message: <String, dynamic>{
           'jsonrpc': jsonRpcVersion,
           'method': Method.notificationsProgress,
@@ -405,10 +409,11 @@ _GeneratedJsonRpcFixture _generatedJsonRpcFixture(Random random, int index) {
       ),
     _ => _GeneratedJsonRpcFixture(
         name: 'fuzz.jsonrpc.error-id.$index',
-        description: 'Generated error responses preserve string-or-number IDs.',
+        description:
+            'Generated error responses preserve string-or-integer IDs.',
         message: <String, dynamic>{
           'jsonrpc': jsonRpcVersion,
-          'id': random.nextBool() ? numericIdValue : stringId,
+          'id': random.nextBool() ? integerId : stringId,
           'error': <String, dynamic>{
             'code': ErrorCode.invalidRequest.value,
             'message': 'generated invalid request',
@@ -683,7 +688,7 @@ Future<void> _rejectsMalformedProgressToken() async {
   );
 }
 
-Future<void> _dispatchesNumericProgressToken() async {
+Future<void> _dispatchesIntegerProgressToken() async {
   final transport = _ConformanceTransport();
   final server = McpServer(
     const Implementation(name: 'server', version: '1.0.0'),
@@ -709,7 +714,7 @@ Future<void> _dispatchesNumericProgressToken() async {
         'name': 'progress_probe',
         'arguments': <String, dynamic>{},
         '_meta': <String, dynamic>{
-          'progressToken': 1.5,
+          'progressToken': 15,
         },
       },
     ),
@@ -728,8 +733,8 @@ Future<void> _dispatchesNumericProgressToken() async {
   final progress = ProgressNotification.fromJson(
     progressMessages.single.params ?? const <String, dynamic>{},
   );
-  if (progress.progressToken != 1.5) {
-    throw StateError('Expected numeric progress token to be preserved.');
+  if (progress.progressToken != 15) {
+    throw StateError('Expected integer progress token to be preserved.');
   }
   if (progress.progress != 1 || progress.total != 2) {
     throw StateError('Expected progress values to be preserved.');
@@ -828,6 +833,47 @@ Future<void> _rejectsNullJsonRpcParamsMember() async {
   }
 }
 
+Future<void> _rejectsFractionalIdsAndProgressTokens() async {
+  for (final message in const [
+    <String, dynamic>{
+      'jsonrpc': jsonRpcVersion,
+      'id': 1.5,
+      'method': Method.ping,
+    },
+    <String, dynamic>{
+      'jsonrpc': jsonRpcVersion,
+      'id': 1.5,
+      'result': <String, dynamic>{},
+    },
+    <String, dynamic>{
+      'jsonrpc': jsonRpcVersion,
+      'id': 1.5,
+      'error': <String, dynamic>{
+        'code': -32600,
+        'message': 'Invalid request',
+      },
+    },
+    <String, dynamic>{
+      'jsonrpc': jsonRpcVersion,
+      'id': 1,
+      'method': Method.ping,
+      'params': <String, dynamic>{
+        '_meta': <String, dynamic>{'progressToken': 1.5},
+      },
+    },
+    <String, dynamic>{
+      'jsonrpc': jsonRpcVersion,
+      'method': Method.notificationsProgress,
+      'params': <String, dynamic>{
+        'progressToken': 1.5,
+        'progress': 1,
+      },
+    },
+  ]) {
+    _expectThrowsFormatException(() => JsonRpcMessage.fromJson(message));
+  }
+}
+
 Future<void> _preservesStringResponseId() async {
   final message = JsonRpcMessage.fromJson(const <String, dynamic>{
     'jsonrpc': jsonRpcVersion,
@@ -846,21 +892,21 @@ Future<void> _preservesStringResponseId() async {
   }
 }
 
-Future<void> _preservesNumericResponseId() async {
+Future<void> _preservesIntegerResponseId() async {
   final message = JsonRpcMessage.fromJson(const <String, dynamic>{
     'jsonrpc': jsonRpcVersion,
-    'id': 1.5,
+    'id': 15,
     'result': <String, dynamic>{},
   });
 
   if (message is! JsonRpcResponse) {
     throw StateError('Expected JsonRpcResponse, got ${message.runtimeType}.');
   }
-  if (message.id != 1.5) {
-    throw StateError('Expected numeric response ID to be preserved.');
+  if (message.id != 15) {
+    throw StateError('Expected integer response ID to be preserved.');
   }
-  if (message.toJson()['id'] != 1.5) {
-    throw StateError('Expected serialized response ID to stay numeric.');
+  if (message.toJson()['id'] != 15) {
+    throw StateError('Expected serialized response ID to stay an integer.');
   }
 }
 
@@ -933,12 +979,12 @@ Future<void> _preservesStringProgressToken() async {
   }
 }
 
-Future<void> _preservesNumericProgressToken() async {
+Future<void> _preservesIntegerProgressToken() async {
   final message = JsonRpcMessage.fromJson(const <String, dynamic>{
     'jsonrpc': jsonRpcVersion,
     'method': Method.notificationsProgress,
     'params': <String, dynamic>{
-      'progressToken': 1.5,
+      'progressToken': 15,
       'progress': 1,
       'total': 2,
     },
@@ -949,11 +995,11 @@ Future<void> _preservesNumericProgressToken() async {
       'Expected JsonRpcProgressNotification, got ${message.runtimeType}.',
     );
   }
-  if (message.progressParams.progressToken != 1.5) {
-    throw StateError('Expected numeric progress token to be preserved.');
+  if (message.progressParams.progressToken != 15) {
+    throw StateError('Expected integer progress token to be preserved.');
   }
-  if (message.toJson()['params']['progressToken'] != 1.5) {
-    throw StateError('Expected serialized progress token to stay numeric.');
+  if (message.toJson()['params']['progressToken'] != 15) {
+    throw StateError('Expected serialized progress token to stay an integer.');
   }
 }
 
diff --git a/packages/mcp_dart_cli/test/src/conformance_command_test.dart b/packages/mcp_dart_cli/test/src/conformance_command_test.dart
index 401c8cc4..d3ac7ef3 100644
--- a/packages/mcp_dart_cli/test/src/conformance_command_test.dart
+++ b/packages/mcp_dart_cli/test/src/conformance_command_test.dart
@@ -26,9 +26,10 @@ void main() {
           'jsonrpc.rejects-null-error-response-id',
           'jsonrpc.rejects-null-params-member',
           'jsonrpc.preserves-string-response-id',
-          'jsonrpc.preserves-numeric-response-id',
+          'jsonrpc.preserves-integer-response-id',
           'jsonrpc.preserves-string-progress-token',
-          'jsonrpc.preserves-numeric-progress-token',
+          'jsonrpc.preserves-integer-progress-token',
+          'jsonrpc.rejects-fractional-ids-and-progress-tokens',
           'protocol-version.advertises-latest-2025-11-25',
         ]),
       );
@@ -47,7 +48,7 @@ void main() {
           'elicitation.rejects-invalid-form-url-union',
           'tasks.strips-unnegotiated-related-task-metadata',
           'progress.rejects-malformed-progress-token',
-          'progress.dispatches-numeric-progress-token',
+          'progress.dispatches-integer-progress-token',
         ]),
       );
       expect(
diff --git a/test/mcp_2026_07_28_test.dart b/test/mcp_2026_07_28_test.dart
index fdcfd354..b0f747c7 100644
--- a/test/mcp_2026_07_28_test.dart
+++ b/test/mcp_2026_07_28_test.dart
@@ -322,24 +322,24 @@ void main() {
       }
     });
 
-    test('preserves finite numeric request ids and progress tokens', () {
+    test('preserves integer request ids and progress tokens', () {
       final message = JsonRpcMessage.fromJson(
         const {
           'jsonrpc': jsonRpcVersion,
-          'id': 1.5,
+          'id': 1,
           'method': Method.toolsList,
           'params': {
-            '_meta': {'progressToken': 2.5},
+            '_meta': {'progressToken': 2},
           },
         },
       );
 
       expect(message, isA<JsonRpcListToolsRequest>());
       final request = message as JsonRpcListToolsRequest;
-      expect(request.id, 1.5);
-      expect(request.progressToken, 2.5);
-      expect(request.toJson()['id'], 1.5);
-      expect(request.toJson()['params']['_meta']['progressToken'], 2.5);
+      expect(request.id, 1);
+      expect(request.progressToken, 2);
+      expect(request.toJson()['id'], 1);
+      expect(request.toJson()['params']['_meta']['progressToken'], 2);
     });
 
     test('rejects URL elicitation relative URI values', () {
diff --git a/test/server/stdio_test.dart b/test/server/stdio_test.dart
index 4bf31761..07eadc36 100644
--- a/test/server/stdio_test.dart
+++ b/test/server/stdio_test.dart
@@ -343,6 +343,14 @@ void main() {
             'method': 'ping',
           },
         ),
+        (
+          field: 'id',
+          message: {
+            'jsonrpc': '2.0',
+            'id': 1.5,
+            'method': 'ping',
+          },
+        ),
         (
           field: 'id',
           message: {
@@ -351,6 +359,19 @@ void main() {
             'method': 'ping',
           },
         ),
+        (
+          field: 'progressToken',
+          message: {
+            'jsonrpc': '2.0',
+            'id': 'with-bad-meta',
+            'method': 'ping',
+            'params': {
+              '_meta': {
+                'progressToken': 1.5,
+              },
+            },
+          },
+        ),
         (
           field: 'progressToken',
           message: {
@@ -375,6 +396,17 @@ void main() {
             },
           },
         ),
+        (
+          field: 'progressToken',
+          message: {
+            'jsonrpc': '2.0',
+            'method': 'notifications/progress',
+            'params': {
+              'progressToken': 1.5,
+              'progress': 0,
+            },
+          },
+        ),
         (
           field: 'progressToken',
           message: {
diff --git a/test/shared/progress_test.dart b/test/shared/progress_test.dart
index 32404899..07ffef74 100644
--- a/test/shared/progress_test.dart
+++ b/test/shared/progress_test.dart
@@ -264,26 +264,26 @@ void main() {
       expect(msg3, isA<JsonRpcResponse>());
     });
 
-    test('Server sends progress with finite numeric progress token', () async {
+    test('Server sends progress with integer progress token', () async {
       protocol.setRequestHandler<JsonRpcRequest>(
-        'test/numeric-token-task',
+        'test/integer-token-task',
         (request, extra) async {
           await extra.sendProgress(10, total: 100, message: 'Starting');
           return TestResult(value: 'success');
         },
         (id, params, meta) => JsonRpcRequest(
           id: id,
-          method: 'test/numeric-token-task',
+          method: 'test/integer-token-task',
           params: params,
           meta: meta,
         ),
       );
 
-      const progressToken = 12345.5;
+      const progressToken = 12345;
       transport.receiveMessage(
         const JsonRpcRequest(
           id: 99,
-          method: 'test/numeric-token-task',
+          method: 'test/integer-token-task',
           meta: {'progressToken': progressToken},
         ),
       );
@@ -304,7 +304,7 @@ void main() {
       expect(msg2, isA<JsonRpcResponse>());
     });
 
-    test('RequestHandlerExtra ignores non-finite progress token', () async {
+    test('RequestHandlerExtra ignores malformed progress token', () async {
       final sentNotifications = <JsonRpcNotification>[];
       final extra = RequestHandlerExtra(
         signal: BasicAbortController().signal,
@@ -327,6 +327,29 @@ void main() {
       expect(sentNotifications, isEmpty);
     });
 
+    test('RequestHandlerExtra ignores fractional progress token', () async {
+      final sentNotifications = <JsonRpcNotification>[];
+      final extra = RequestHandlerExtra(
+        signal: BasicAbortController().signal,
+        requestId: 101,
+        meta: const {'progressToken': 123.5},
+        sendNotification: (notification, {relatedTask}) async {
+          sentNotifications.add(notification);
+        },
+        sendRequest: <T extends BaseResultData>(
+          JsonRpcRequest request,
+          T Function(Map<String, dynamic>) resultFactory,
+          RequestOptions options,
+        ) async {
+          return resultFactory({});
+        },
+      );
+
+      await extra.sendProgress(10);
+
+      expect(sentNotifications, isEmpty);
+    });
+
     test('RequestHandlerExtra rejects non-increasing progress', () async {
       final sentNotifications = <JsonRpcNotification>[];
       final extra = RequestHandlerExtra(
diff --git a/test/shared/protocol_test.dart b/test/shared/protocol_test.dart
index 9cb05b3d..d65d86b5 100644
--- a/test/shared/protocol_test.dart
+++ b/test/shared/protocol_test.dart
@@ -505,17 +505,16 @@ void main() {
       expect((await requestFuture).value, 'ok');
     });
 
-    test('public notification preserves finite numeric relatedRequestId',
-        () async {
+    test('public notification preserves integer relatedRequestId', () async {
       await protocol.connect(transport);
 
       await protocol.notification(
         const JsonRpcNotification(method: 'test/notification'),
-        relatedRequestId: 1.5,
+        relatedRequestId: 15,
       );
 
       expect(transport.sentMessages.single, isA<JsonRpcNotification>());
-      expect(transport.relatedRequestIds.single, 1.5);
+      expect(transport.relatedRequestIds.single, 15);
     });
 
     test('routes nested cancellation notifications for string request IDs',
@@ -658,8 +657,7 @@ void main() {
       expect(result.value, 'response-data');
     });
 
-    test('dispatches finite numeric progress tokens from request metadata',
-        () async {
+    test('dispatches integer progress tokens from request metadata', () async {
       await protocol.connect(transport);
 
       final progressUpdates = <Progress>[];
@@ -668,7 +666,7 @@ void main() {
             const JsonRpcRequest(
               id: 0,
               method: 'test/method',
-              meta: {'progressToken': 1.5},
+              meta: {'progressToken': 15},
             ),
             (json) => TestResult(value: json['value'] as String),
             RequestOptions(
@@ -680,12 +678,12 @@ void main() {
 
       expect(transport.sentMessages, hasLength(1));
       final sentRequest = transport.sentMessages.single as JsonRpcRequest;
-      expect(sentRequest.meta?['progressToken'], 1.5);
+      expect(sentRequest.meta?['progressToken'], 15);
 
       transport.receiveMessage(
         JsonRpcProgressNotification(
           progressParams: const ProgressNotification(
-            progressToken: 1.5,
+            progressToken: 15,
             progress: 50,
             total: 100,
             message: 'halfway',
@@ -1261,6 +1259,27 @@ void main() {
       expect(transport.sentMessages, isEmpty);
     });
 
+    test(
+        'rejects fractional request progress tokens when progress handler is set',
+        () async {
+      await protocol.connect(transport);
+
+      await expectLater(
+        protocol.request<TestResult>(
+          const JsonRpcRequest(
+            id: 0,
+            method: 'test/method',
+            meta: {'progressToken': 1.5},
+          ),
+          (json) => TestResult(value: json['value'] as String),
+          RequestOptions(onprogress: (_) {}),
+        ),
+        throwsA(isA<ArgumentError>()),
+      );
+
+      expect(transport.sentMessages, isEmpty);
+    });
+
     test('keeps task-augmented progress tokens until terminal task status',
         () async {
       await protocol.connect(transport);
diff --git a/test/shared/transport_api_compatibility_test.dart b/test/shared/transport_api_compatibility_test.dart
index 9a2f2ab0..00473749 100644
--- a/test/shared/transport_api_compatibility_test.dart
+++ b/test/shared/transport_api_compatibility_test.dart
@@ -59,7 +59,8 @@ void main() {
       expect(transport.lastRelatedRequestId, isNull);
     });
 
-    test('request-id-aware transports preserve non-integer relatedRequestId',
+    test(
+        'request-id-aware transports preserve string and integer relatedRequestId',
         () async {
       final transport = FullRequestIdAwareTransport();
 
@@ -74,10 +75,10 @@ void main() {
 
       await transport.sendPreservingRequestId(
         const JsonRpcNotification(method: 'test/notification'),
-        relatedRequestId: 1.5,
+        relatedRequestId: 15,
       );
 
-      expect(transport.lastRequestIdAwareRelatedRequestId, 1.5);
+      expect(transport.lastRequestIdAwareRelatedRequestId, 15);
     });
   });
 }
diff --git a/test/types_edge_cases_test.dart b/test/types_edge_cases_test.dart
index 6ac933c1..aff5633d 100644
--- a/test/types_edge_cases_test.dart
+++ b/test/types_edge_cases_test.dart
@@ -181,6 +181,7 @@ void main() {
       for (final requestId in [
         null,
         true,
+        123.5,
         double.nan,
         double.infinity,
         <String, dynamic>{},
@@ -202,9 +203,14 @@ void main() {
       }
 
       expect(
-        () => const CancelledNotificationParams(
-          requestId: double.nan,
-        ).toJson(),
+        () => const CancelledNotificationParams(requestId: 123.5).toJson(),
+        throwsA(
+          isA<FormatException>()
+              .having((e) => e.message, 'message', contains('requestId')),
+        ),
+      );
+      expect(
+        () => const CancelledNotificationParams(requestId: double.nan).toJson(),
         throwsA(
           isA<FormatException>()
               .having((e) => e.message, 'message', contains('requestId')),
@@ -212,8 +218,8 @@ void main() {
       );
     });
 
-    test('preserves string and finite number requestId wire values', () {
-      for (final requestId in <Object>[123, 123.5, 'request-123']) {
+    test('preserves string and integer requestId wire values', () {
+      for (final requestId in <Object>[123, 'request-123']) {
         final notification = JsonRpcCancelledNotification.fromJson({
           'jsonrpc': '2.0',
           'method': 'notifications/cancelled',
@@ -341,6 +347,7 @@ void main() {
       for (final progressToken in [
         null,
         false,
+        123.5,
         double.nan,
         double.infinity,
         <String, dynamic>{},
@@ -366,10 +373,16 @@ void main() {
       }
 
       expect(
-        () => const ProgressNotification(
-          progressToken: double.nan,
-          progress: 1,
-        ).toJson(),
+        () => const ProgressNotification(progressToken: 123.5, progress: 1)
+            .toJson(),
+        throwsA(
+          isA<FormatException>()
+              .having((e) => e.message, 'message', contains('progressToken')),
+        ),
+      );
+      expect(
+        () => const ProgressNotification(progressToken: double.nan, progress: 1)
+            .toJson(),
         throwsA(
           isA<FormatException>()
               .having((e) => e.message, 'message', contains('progressToken')),
@@ -377,8 +390,8 @@ void main() {
       );
     });
 
-    test('preserves string and finite number progressToken wire values', () {
-      for (final progressToken in <Object>[123, 123.5, 'progress-123']) {
+    test('preserves string and integer progressToken wire values', () {
+      for (final progressToken in <Object>[123, 'progress-123']) {
         final notification = JsonRpcProgressNotification.fromJson({
           'jsonrpc': '2.0',
           'method': 'notifications/progress',
@@ -496,6 +509,7 @@ void main() {
       for (final id in [
         null,
         false,
+        123.5,
         double.nan,
         double.infinity,
         <String, dynamic>{},
@@ -514,6 +528,19 @@ void main() {
         );
       }
 
+      expect(
+        () => const JsonRpcRequest(
+          id: 123.5,
+          method: 'unknown/request',
+        ).toJson(),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            contains('JsonRpcRequest.id'),
+          ),
+        ),
+      );
       expect(
         () => const JsonRpcRequest(
           id: double.nan,
@@ -529,8 +556,8 @@ void main() {
       );
     });
 
-    test('preserves string and finite number request ids', () {
-      for (final id in <Object>[123, 123.5, 'request-123']) {
+    test('preserves string and integer request ids', () {
+      for (final id in <Object>[123, 'request-123']) {
         final message = JsonRpcMessage.fromJson({
           'jsonrpc': '2.0',
           'id': id,
@@ -547,6 +574,7 @@ void main() {
       for (final token in [
         null,
         false,
+        123.5,
         double.nan,
         double.infinity,
         <String, dynamic>{},
@@ -570,6 +598,21 @@ void main() {
           ),
         );
       }
+
+      expect(
+        () => const JsonRpcRequest(
+          id: 'request-1',
+          method: 'unknown/request',
+          meta: {'progressToken': 123.5},
+        ).toJson(),
+        throwsA(
+          isA<FormatException>().having(
+            (e) => e.message,
+            'message',
+            contains('_meta.progressToken'),
+          ),
+        ),
+      );
     });
 
     test('rejects malformed request _meta wire values', () {
@@ -604,9 +647,8 @@ void main() {
       );
     });
 
-    test('preserves string and finite number request progressToken wire values',
-        () {
-      for (final token in <Object>[123, 123.5, 'progress-123']) {
+    test('preserves string and integer request progressToken wire values', () {
+      for (final token in <Object>[123, 'progress-123']) {
         final message = JsonRpcMessage.fromJson({
           'jsonrpc': '2.0',
           'id': 'request-1',
@@ -665,6 +707,7 @@ void main() {
     test('rejects malformed response id wire values', () {
       for (final id in [
         false,
+        123.5,
         double.nan,
         double.infinity,
         <String, dynamic>{},
@@ -715,6 +758,7 @@ void main() {
       for (final id in [
         null,
         false,
+        123.5,
         double.nan,
         double.infinity,
         <String, dynamic>{},