Add TS 2026 RC interop smoke

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ### Conformance and release readiness
 
+- Added a manual TypeScript SDK 2026 RC interop fixture pinned to the upstream
+  PR #2327 preview package, covering modern negotiation, `tools/list`, and
+  `tools/call` against the Dart 2026 RC conformance server.
+- Marked `server/discover` as a 2026 cacheable result so stateless responses
+  include default `ttlMs` and `cacheScope` hints.
 - Updated official conformance gates to
   `@modelcontextprotocol/conformance@0.2.0-alpha.4`, with 2026 RC runs pinned
   to `2026-07-28`, the full 2026 server scenario list covered in CI, the 2026

doc/interoperability.md

@@ -21,6 +21,7 @@ For requirement-level MCP 2025-11-25 coverage, see the
 | Dart client -> TypeScript SDK server | Streamable HTTP | `2025-11-25` | [`test/interop/dart_client_with_ts_server_test.dart`](../test/interop/dart_client_with_ts_server_test.dart), [`test/interop/ts/`](../test/interop/ts/) | Verified | Covers tool calls and stale preconfigured session-id recovery. |
 | TypeScript SDK client -> Dart server | stdio | `2025-11-25` | [`test/interop/ts_client_with_dart_server_test.dart`](../test/interop/ts_client_with_dart_server_test.dart), [`test/interop/test_dart_server.dart`](../test/interop/test_dart_server.dart) | Verified | Runs the compiled TypeScript client fixture against a Dart server process and checks that an official TS client can list tools immediately after the lifecycle handshake. |
 | TypeScript SDK client -> Dart server | Streamable HTTP | `2025-11-25` | [`test/interop/ts_client_with_dart_server_test.dart`](../test/interop/ts_client_with_dart_server_test.dart), [`test/interop/test_dart_server.dart`](../test/interop/test_dart_server.dart) | Verified | Includes official TS Streamable HTTP client lifecycle coverage, pre-`initialized` operation rejection, GET SSE streams, and `Last-Event-ID` replay behavior. |
+| TypeScript SDK preview client -> Dart server | Streamable HTTP | `2026-07-28` draft/RC | [`test/interop/ts_2026_rc/`](../test/interop/ts_2026_rc/), [`tool/testing/run_ts_2026_rc_interop.dart`](../tool/testing/run_ts_2026_rc_interop.dart) | Experimental manual check | Uses a pinned `pkg.pr.new` preview from TypeScript SDK PR #2327 because published TS packages do not yet advertise `2026-07-28`. Covers modern negotiation, `tools/list`, and `tools/call` against the Dart 2026 RC conformance server. Not a CI gate yet. |
 | Dart client -> Python MCP server | stdio | Server-dependent | [`doc/transports.md`](transports.md#connect-to-python-server) | Documented recipe | The transport can spawn Python servers over stdio, but this repo does not yet include an automated Python SDK fixture. |
 | Flutter/Web client -> Dart server | Streamable HTTP | `2025-11-25` | [`example/flutter_http_client/`](../example/flutter_http_client/), [`doc/flutter-recipes.md`](flutter-recipes.md) | Documented recipe | Flutter Web cannot spawn stdio servers; use Streamable HTTP or another browser-safe transport. |
 | MCP Apps host/client metadata | stdio or Streamable HTTP | `2025-11-25` plus `io.modelcontextprotocol/ui` extension | [`doc/mcp-apps.md`](mcp-apps.md), [`example/mcp_apps_helpers_server.dart`](../example/mcp_apps_helpers_server.dart), [`test/types/mcp_ui_test.dart`](../test/types/mcp_ui_test.dart), [`test/server/mcp_ui_test.dart`](../test/server/mcp_ui_test.dart) | Verified | Verified coverage is limited to SDK metadata helpers, serialization, and checked-in examples; host rendering behavior varies by host, so verify UI metadata against your target host. |
@@ -42,6 +43,20 @@ dart test --tags interop
 
 If the compiled fixtures are missing, local test runs skip the interop groups; CI should fail when required fixtures are unavailable.
 
+The TypeScript 2026 RC fixture is manual while the upstream SDK support remains
+unreleased and split across preview PRs:
+
+```bash
+# From repository root
+cd test/interop/ts_2026_rc
+npm install
+cd ../../..
+dart run tool/testing/run_ts_2026_rc_interop.dart
+```
+
+This starts the Dart 2026 RC conformance server and runs the pinned TypeScript
+SDK preview client against it.
+
 The CLI spec conformance gate covers raw-wire negative cases that do not need a
 cross-SDK fixture, including stable MCP 2025-11-25 checks and MCP 2026-07-28 RC
 stateless/discovery/task-extension checks:
@@ -65,6 +80,8 @@ When adding a new interoperability claim:
 ## Known gaps worth tracking
 
 - Automated Python SDK fixture coverage.
+- CI promotion for the TypeScript 2026 RC interop fixture after the TypeScript
+  SDK publishes a 2026-compatible alpha package.
 - Host-specific MCP Apps rendering compatibility notes.
 - More OAuth-protected remote server scenarios beyond the checked-in examples.
 - A broader compatibility table once additional SDKs expose stable 2025-11-25 fixtures.

doc/mcp-2026-rc.md

@@ -130,7 +130,7 @@ Before creating follow-up dev tags from `dev/2026-07-28-rc`, run:
 ```sh
 dart analyze
 dart run test/conformance/run_2025_server_conformance.dart
-npx -y @modelcontextprotocol/conformance@0.2.0-alpha.3 client \
+npx -y @modelcontextprotocol/conformance@0.2.0-alpha.4 client \
   --command "dart run test/conformance/mcp_2026_rc_client.dart" \
   --suite all \
   --spec-version 2025-11-25
@@ -142,10 +142,16 @@ dart run tool/validate_cli_publish.dart
 ```
 
 The `run_2026_rc_server_conformance.dart` gate runs the full
-`@modelcontextprotocol/conformance@0.2.0-alpha.3` server scenario list for
+`@modelcontextprotocol/conformance@0.2.0-alpha.4` server scenario list for
 `--spec-version 2026-07-28`, including the stable-style tool, resource, prompt,
 completion, and JSON Schema scenarios that the alpha package tags for the RC.
 
+For cross-SDK smoke coverage against the TypeScript SDK 2026 preview client,
+run the manual fixture documented in
+[`doc/interoperability.md`](interoperability.md#running-interop-checks-locally).
+Keep that fixture out of CI until upstream publishes a 2026-compatible alpha
+package instead of requiring a `pkg.pr.new` PR preview.
+
 For dev packages, keep package documentation links pointed at
 `dev/2026-07-28-rc` until the draft work is ready to merge back to `main`.
 Restore those links to `main` as part of the final spec release prep.

lib/src/server/server.dart

@@ -873,6 +873,7 @@ class Server extends Protocol {
 
   bool _requiresCacheableResult(String method) {
     return switch (method) {
+      Method.serverDiscover ||
       Method.toolsList ||
       Method.promptsList ||
       Method.resourcesList ||

lib/src/shared/protocol.dart

@@ -16,6 +16,7 @@ bool _isProgressToken(Object? token) =>
     (token is double && token.isFinite && token == token.truncateToDouble());
 
 const Set<String> _statelessCacheableResultMethods = {
+  Method.serverDiscover,
   Method.toolsList,
   Method.promptsList,
   Method.resourcesList,

lib/src/types/initialization.dart

@@ -1345,7 +1345,7 @@ class InitializeResult implements BaseResultData {
 }
 
 /// Result data for a successful `server/discover` request.
-class DiscoverResult implements BaseResultData {
+class DiscoverResult implements CacheableResultData {
   /// Result discriminator used by the 2026 result model.
   final String resultType;
 
@@ -1361,6 +1361,14 @@ class DiscoverResult implements BaseResultData {
   /// Instructions describing how to use the server and its features.
   final String? instructions;
 
+  /// How long, in milliseconds, the client may consider this result fresh.
+  @override
+  final int? ttlMs;
+
+  /// Intended cache visibility: `public` or `private`.
+  @override
+  final String? cacheScope;
+
   /// Optional metadata.
   @override
   final Map<String, dynamic>? meta;
@@ -1371,6 +1379,8 @@ class DiscoverResult implements BaseResultData {
     required this.capabilities,
     required this.serverInfo,
     this.instructions,
+    this.ttlMs,
+    this.cacheScope,
     this.meta,
   });
 
@@ -1407,12 +1417,19 @@ class DiscoverResult implements BaseResultData {
         json['instructions'],
         'DiscoverResult.instructions',
       ),
+      ttlMs: readOptionalTtlMs(json['ttlMs'], 'DiscoverResult.ttlMs'),
+      cacheScope: readOptionalCacheScope(
+        json['cacheScope'],
+        'DiscoverResult.cacheScope',
+      ),
       meta: readOptionalJsonObject(json['_meta'], 'DiscoverResult._meta'),
     );
   }
 
   @override
   Map<String, dynamic> toJson() {
+    validateTtlMs(ttlMs, 'DiscoverResult.ttlMs');
+    validateCacheScope(cacheScope, 'DiscoverResult.cacheScope');
     if (resultType != resultTypeComplete) {
       throw ArgumentError.value(
         resultType,
@@ -1427,6 +1444,8 @@ class DiscoverResult implements BaseResultData {
       'capabilities': capabilities.toJson(omitLegacyTasks: true),
       'serverInfo': serverInfo.toJson(),
       if (instructions != null) 'instructions': instructions,
+      if (ttlMs != null) 'ttlMs': ttlMs,
+      if (cacheScope != null) 'cacheScope': cacheScope,
       if (meta != null) '_meta': readJsonObject(meta, 'DiscoverResult._meta'),
     };
   }

packages/mcp_dart_cli/lib/src/conformance_runner.dart

@@ -922,6 +922,8 @@ class _DiscoveringConformanceTransport extends Transport
               'name': 'conformance-server',
               'version': '1.0.0',
             },
+            'ttlMs': 0,
+            'cacheScope': _cacheScopePrivate,
           },
         ),
       );
@@ -1480,18 +1482,21 @@ Future<void> _httpModernProtocolErrorsRetryDiscovery() async {
               jsonEncode(
                 JsonRpcResponse(
                   id: id,
-                  result: const DiscoverResult(
-                    supportedVersions: <String>[
+                  result: const <String, dynamic>{
+                    'resultType': _resultTypeComplete,
+                    'supportedVersions': <String>[
                       _draftProtocolVersion2026_07_28,
                     ],
-                    capabilities: ServerCapabilities(
-                      tools: ServerCapabilitiesTools(),
-                    ),
-                    serverInfo: Implementation(
-                      name: 'modern-http-server',
-                      version: '1.0.0',
-                    ),
-                  ).toJson(),
+                    'capabilities': <String, dynamic>{
+                      'tools': <String, dynamic>{},
+                    },
+                    'serverInfo': <String, dynamic>{
+                      'name': 'modern-http-server',
+                      'version': '1.0.0',
+                    },
+                    'ttlMs': 0,
+                    'cacheScope': _cacheScopePrivate,
+                  },
                 ).toJson(),
               ),
             );

test/interop/ts_2026_rc/.gitignore

@@ -0,0 +1,3 @@
+node_modules/
+npm-debug.log*
+

test/interop/ts_2026_rc/README.md

@@ -0,0 +1,35 @@
+# TypeScript SDK 2026 RC Interop
+
+This fixture is an experimental smoke test for the unreleased MCP
+`2026-07-28` draft/RC path against the official TypeScript SDK work in
+progress.
+
+It is intentionally separate from `test/interop/ts`, which tracks the published
+stable TypeScript SDK and MCP `2025-11-25` behavior. The published split
+TypeScript packages still do not advertise `2026-07-28`, so this fixture pins a
+`pkg.pr.new` preview package from TypeScript SDK PR #2327. That PR includes the
+modern Streamable HTTP `Mcp-Name` header support needed to interoperate with the
+Dart 2026 RC server.
+
+## Run
+
+From the repository root:
+
+```bash
+cd test/interop/ts_2026_rc
+npm install
+cd ../../..
+dart run tool/testing/run_ts_2026_rc_interop.dart
+```
+
+The runner starts `test/conformance/mcp_2026_rc_server.dart`, waits for its
+bound local URL, and then runs `src/client.mjs` against it. The smoke asserts:
+
+- TypeScript client negotiation selects the modern `2026-07-28` era.
+- `tools/list` returns the Dart fixture tools.
+- `tools/call` can invoke the Dart `echo` tool over modern Streamable HTTP.
+
+Keep this as a manual, non-blocking check until the TypeScript SDK publishes a
+stable 2026-compatible alpha package or the upstream PR stack lands on the
+`v2-2026-07-28` branch.
+