fix(server): preserve ambient Cursor MCP servers

packages/provider-cursor/src/server/adapter.test.ts

@@ -55,6 +55,17 @@ describe("CursorAdapterV2", () => {
         });
         const instanceId = ProviderInstanceId.make("cursor");
         const threadId = ThreadId.make("cursor-lifecycle-thread");
+        const mcpSessions = yield* McpProviderSessions.McpProviderSessions;
+        yield* mcpSessions.set({
+          environmentId: EnvironmentId.make("cursor-lifecycle-environment"),
+          threadId,
+          providerSessionId: "cursor-lifecycle-session",
+          providerInstanceId: instanceId,
+          endpoint: "http://127.0.0.1:43123/mcp",
+          authorizationHeader: "Bearer synthetic-cursor-token",
+          browserToolsAvailable: true,
+        });
+        let sentWithMcpOverride = true;
         const modelSelection = { instanceId, model: "composer-2.5" };
         const runtimePolicy = ProviderAdapter.ProviderAdapterV2RuntimePolicy.make({
           runtimeMode: "full-access",
@@ -75,6 +86,7 @@ describe("CursorAdapterV2", () => {
                 close: Effect.void,
                 send: (input) =>
                   Effect.gen(function* () {
+                    sentWithMcpOverride = Object.hasOwn(input.options ?? {}, "mcpServers");
                     // Recorded Cursor task calls (see fixtures/subagent) stream a
                     // partial-tool-call before tool-call-started with the same args.
                     // The run then ends without tool-call-completed, which a live
@@ -184,6 +196,8 @@ describe("CursorAdapterV2", () => {
           Stream.takeUntil((event) => event.type === "turn.terminal"),
           Stream.runCollect,
         );
+        // Keep injected MCP at agent creation so sends preserve Cursor's ambient servers.
+        assert.isFalse(sentWithMcpOverride);
         const rows = events.filter((event) => event.type === "subagent.updated");
         assert.equal(rows[0]?.subagent.status, "running");
         assert.equal(rows[0]?.subagent.model, model ?? null);

packages/provider-cursor/src/server/adapter.ts

@@ -2206,12 +2206,12 @@ export const makeCursorAdapterV2 = Effect.fn("makeCursorAdapterV2")(function* (
             const message = yield* resolveUserMessage(turnInput, mcpServers);
             const pendingUpdates: Array<InteractionUpdate> = [];
             let context: ActiveCursorTurn | null = null;
+            // MCP send overrides replace the ambient servers loaded when the agent opens.
             const sdkRun = yield* agent.session.send({
               message,
               options: {
                 model: cursorSdkModelSelection(turnInput.modelSelection),
                 mode: turnInput.runtimePolicy.interactionMode === "plan" ? "plan" : "agent",
-                ...(mcpServers === undefined ? {} : { mcpServers }),
               },
               onDelta: (update) => {
                 if (context === null) {