fix: restore MCP SDK v1 interoperability

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- Restored the MCP SDK v1 client for compatibility with deployed MCP servers and OAuth providers. This rollback temporarily removes SDK v2-only protocol negotiation while retaining OAuth issuer binding and callback issuer validation. See issue #236.
+
 ## [2.15.0] - 2026-07-25
 
 ### Added

OAUTH.md

@@ -300,15 +300,15 @@ The OAuth implementation uses the following modules:
 
 ## SDK Integration
 
-The implementation uses these MCP SDK v2 exports:
+The implementation uses the MCP SDK v1 client and OAuth APIs:
 
 ```typescript
+import { StreamableHTTPClientTransport } from "@modelcontextprotocol/sdk/client/streamableHttp.js"
 import {
   auth,
-  StreamableHTTPClientTransport,
   UnauthorizedError,
   type OAuthClientProvider,
-} from "@modelcontextprotocol/client"
+} from "@modelcontextprotocol/sdk/client/auth.js"
 ```
 
 The `McpOAuthProvider` class implements `OAuthClientProvider` and is passed to `StreamableHTTPClientTransport`:

__tests__/abort-signal.test.ts

@@ -71,6 +71,7 @@ describe("AbortSignal propagation", () => {
     expect(result.details.error).toBe("aborted");
     expect(callTool).toHaveBeenCalledWith(
       { name: "slow", arguments: {}, _meta: undefined },
+      undefined,
       { signal: controller.signal },
     );
     expect(state.manager.decrementInFlight).toHaveBeenCalledWith("demo");
@@ -90,6 +91,7 @@ describe("AbortSignal propagation", () => {
     expect(result.details.error).toBe("aborted");
     expect(callTool).toHaveBeenCalledWith(
       { name: "slow", arguments: {}, _meta: undefined },
+      undefined,
       { signal: controller.signal },
     );
     expect(state.manager.decrementInFlight).toHaveBeenCalledWith("demo");

__tests__/direct-tools-auto-auth.test.ts

@@ -110,6 +110,7 @@ describe("direct tools auto auth", () => {
         arguments: { q: "hello" },
         _meta: undefined,
       },
+      undefined,
       { timeout: 4321 },
     );
     expect(result.content[0].text).toContain("ok");
@@ -156,6 +157,7 @@ describe("direct tools auto auth", () => {
     expect(state.manager.getRequestOptions).toHaveBeenCalledWith("demo", controller.signal);
     expect(connection.client.callTool).toHaveBeenCalledWith(
       { name: "search", arguments: {}, _meta: undefined },
+      undefined,
       requestOptions,
     );
     expect(result.details).toMatchObject({ error: "aborted", server: "demo" });
@@ -244,7 +246,7 @@ describe("direct tools auto auth", () => {
   });
 
   it("runs URL elicitations returned by a URL-required tool error", async () => {
-    const { UrlElicitationRequiredError } = await import("@modelcontextprotocol/client");
+    const { UrlElicitationRequiredError } = await import("@modelcontextprotocol/sdk/types.js");
     const { createDirectToolExecutor } = await import("../direct-tools.ts");
     const error = new UrlElicitationRequiredError([{
       mode: "url",

__tests__/elicitation-handler.test.ts

@@ -1,5 +1,5 @@
 import { beforeEach, describe, expect, it, vi } from "vitest";
-import type { ElicitRequest } from "@modelcontextprotocol/client";
+import type { ElicitRequest } from "@modelcontextprotocol/sdk/types.js";
 
 const mocks = vi.hoisted(() => ({
   open: vi.fn(async () => undefined),

__tests__/fixtures/delayed-mcp-server.mjs

@@ -1,7 +1,8 @@
 import { rename, writeFile } from "node:fs/promises";
 import { join } from "node:path";
-import { Server } from "@modelcontextprotocol/server";
-import { StdioServerTransport } from "@modelcontextprotocol/server/stdio";
+import { Server } from "@modelcontextprotocol/sdk/server/index.js";
+import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
+import { ListResourcesRequestSchema, ListToolsRequestSchema } from "@modelcontextprotocol/sdk/types.js";
 
 const pidPath = process.env.MCP_RELOAD_PID_DIR ? join(process.env.MCP_RELOAD_PID_DIR, `${process.pid}.json`) : undefined;
 const identity = { pid: process.pid, toolName: "reload_identity" };
@@ -18,11 +19,11 @@ const server = new Server(
   { name: "delayed-reload-fixture", version: "1.0.0" },
   { capabilities: { tools: {}, resources: {} } },
 );
-server.setRequestHandler("tools/list", async () => {
+server.setRequestHandler(ListToolsRequestSchema, async () => {
   await new Promise(resolve => setTimeout(resolve, 100));
   return {
     tools: [{ name: identity.toolName, description: "reload identity", inputSchema: { type: "object", properties: {} } }],
   };
 });
-server.setRequestHandler("resources/list", async () => ({ resources: [] }));
+server.setRequestHandler(ListResourcesRequestSchema, async () => ({ resources: [] }));
 await server.connect(new StdioServerTransport());

__tests__/fixtures/elicitation-server.mjs

@@ -1,5 +1,13 @@
-import { Server, UrlElicitationRequiredError } from "@modelcontextprotocol/server";
-import { StdioServerTransport } from "@modelcontextprotocol/server/stdio";
+import { Server } from "@modelcontextprotocol/sdk/server/index.js";
+import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
+import {
+  CallToolRequestSchema,
+  ElicitResultSchema,
+  ListResourcesRequestSchema,
+  ListToolsRequestSchema,
+  ReadResourceRequestSchema,
+  UrlElicitationRequiredError,
+} from "@modelcontextprotocol/sdk/types.js";
 
 const server = new Server(
   { name: "elicitation-integration-server", version: "1.0.0" },
@@ -15,7 +23,7 @@ function urlRequiredError() {
   }]);
 }
 
-server.setRequestHandler("tools/list", async () => ({
+server.setRequestHandler(ListToolsRequestSchema, async () => ({
   tools: [
     { name: "capabilities", inputSchema: { type: "object", properties: {} } },
     { name: "form", inputSchema: { type: "object", properties: {} } },
@@ -24,21 +32,21 @@ server.setRequestHandler("tools/list", async () => ({
   ],
 }));
 
-server.setRequestHandler("resources/list", async () => ({
+server.setRequestHandler(ListResourcesRequestSchema, async () => ({
   resources: [
     { name: "URL-required resource", uri: "test://url-required" },
     { name: "URL-required UI resource", uri: "ui://url-required" },
   ],
 }));
 
-server.setRequestHandler("resources/read", async request => {
+server.setRequestHandler(ReadResourceRequestSchema, async request => {
   if (request.params.uri === "test://url-required" || request.params.uri === "ui://url-required") {
     throw urlRequiredError();
   }
   return { contents: [] };
 });
 
-server.setRequestHandler("tools/call", async request => {
+server.setRequestHandler(CallToolRequestSchema, async request => {
   if (request.params.name === "capabilities") {
     return {
       content: [{ type: "text", text: JSON.stringify(server.getClientCapabilities()?.elicitation ?? null) }],
@@ -48,25 +56,31 @@ server.setRequestHandler("tools/call", async request => {
   if (request.params.name === "url-required") throw urlRequiredError();
 
   if (request.params.name === "form") {
-    const result = await server.elicitInput({
-      mode: "form",
-      message: "Provide a name",
-      requestedSchema: {
-        type: "object",
-        properties: { name: { type: "string", minLength: 1 } },
-        required: ["name"],
+    const result = await server.request({
+      method: "elicitation/create",
+      params: {
+        mode: "form",
+        message: "Provide a name",
+        requestedSchema: {
+          type: "object",
+          properties: { name: { type: "string", minLength: 1 } },
+          required: ["name"],
+        },
       },
-    });
+    }, ElicitResultSchema);
     return { content: [{ type: "text", text: JSON.stringify(result) }] };
   }
 
   if (request.params.name === "url") {
-    const result = await server.elicitInput({
-      mode: "url",
-      message: "Connect your account",
-      elicitationId: "requested-1",
-      url: "https://example.com/authorize",
-    });
+    const result = await server.request({
+      method: "elicitation/create",
+      params: {
+        mode: "url",
+        message: "Connect your account",
+        elicitationId: "requested-1",
+        url: "https://example.com/authorize",
+      },
+    }, ElicitResultSchema);
     if (result.action === "accept") {
       for (const elicitationId of ["unknown", "requested-1", "requested-1"]) {
         await server.notification({

__tests__/fixtures/legacy-no-discover-server.mjs

@@ -0,0 +1,44 @@
+import readline from "node:readline";
+
+const lines = readline.createInterface({ input: process.stdin });
+
+function respond(id, result) {
+  process.stdout.write(`${JSON.stringify({ jsonrpc: "2.0", id, result })}\n`);
+}
+
+function reject(id, message) {
+  process.stdout.write(`${JSON.stringify({
+    jsonrpc: "2.0",
+    id,
+    error: { code: -32601, message },
+  })}\n`);
+}
+
+lines.on("line", line => {
+  const request = JSON.parse(line);
+  if (request.method === "server/discover") {
+    reject(request.id, "server/discover is not supported");
+    return;
+  }
+  if (request.method === "initialize") {
+    respond(request.id, {
+      protocolVersion: "2024-11-05",
+      capabilities: { tools: {} },
+      serverInfo: { name: "legacy-no-discover", version: "1.0.0" },
+    });
+    return;
+  }
+  if (request.method === "tools/list") {
+    respond(request.id, {
+      tools: [{
+        name: "classic_initialize_reached",
+        description: "Classic initialize completed",
+        inputSchema: { type: "object", properties: {} },
+      }],
+    });
+    return;
+  }
+  if (request.id !== undefined) {
+    reject(request.id, "Method not found");
+  }
+});

__tests__/fixtures/output-schema-server.mjs

@@ -1,5 +1,6 @@
-import { Server } from "@modelcontextprotocol/server";
-import { StdioServerTransport } from "@modelcontextprotocol/server/stdio";
+import { Server } from "@modelcontextprotocol/sdk/server/index.js";
+import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
+import { CallToolRequestSchema, ListToolsRequestSchema } from "@modelcontextprotocol/sdk/types.js";
 
 const server = new Server(
   { name: "output-schema-integration-server", version: "1.0.0" },
@@ -36,7 +37,7 @@ const draft2020Tuple = {
 };
 const draft2020Schema = { $schema: "https://json-schema.org/draft/2020-12/schema", ...draft2020Tuple };
 
-server.setRequestHandler("tools/list", async () => ({
+server.setRequestHandler(ListToolsRequestSchema, async () => ({
   tools: [
     { name: "draft07-valid", inputSchema: { type: "object" }, outputSchema: draft07Schema },
     { name: "draft07-invalid", inputSchema: { type: "object" }, outputSchema: draft07InvalidSchema },
@@ -45,7 +46,7 @@ server.setRequestHandler("tools/list", async () => ({
   ],
 }));
 
-server.setRequestHandler("tools/call", async request => {
+server.setRequestHandler(CallToolRequestSchema, async request => {
   const name = request.params.name;
   if (name === "draft07-valid" || name === "draft2020-valid") {
     return { structuredContent: { values: ["ok", 1] }, content: [{ type: "text", text: name }] };

__tests__/fixtures/prompts-server.mjs

@@ -1,5 +1,12 @@
-import { Server } from "@modelcontextprotocol/server";
-import { StdioServerTransport } from "@modelcontextprotocol/server/stdio";
+import { Server } from "@modelcontextprotocol/sdk/server/index.js";
+import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
+import {
+  CallToolRequestSchema,
+  GetPromptRequestSchema,
+  ListPromptsRequestSchema,
+  ListResourcesRequestSchema,
+  ListToolsRequestSchema,
+} from "@modelcontextprotocol/sdk/types.js";
 
 // A minimal MCP server that advertises the `prompts` capability and returns
 // deterministic content, used by prompts-sdk-integration.test.ts to exercise
@@ -9,17 +16,17 @@ const server = new Server(
   { capabilities: { tools: {}, resources: {}, prompts: { listChanged: false } } },
 );
 
-server.setRequestHandler("tools/list", async () => ({
+server.setRequestHandler(ListToolsRequestSchema, async () => ({
   tools: [{ name: "noop", inputSchema: { type: "object", properties: {} } }],
 }));
 
-server.setRequestHandler("resources/list", async () => ({ resources: [] }));
+server.setRequestHandler(ListResourcesRequestSchema, async () => ({ resources: [] }));
 
-server.setRequestHandler("tools/call", async () => ({
+server.setRequestHandler(CallToolRequestSchema, async () => ({
   content: [{ type: "text", text: "ok" }],
 }));
 
-server.setRequestHandler("prompts/list", async () => ({
+server.setRequestHandler(ListPromptsRequestSchema, async () => ({
   prompts: [
     {
       name: "brief",
@@ -37,7 +44,7 @@ server.setRequestHandler("prompts/list", async () => ({
   ],
 }));
 
-server.setRequestHandler("prompts/get", async (request) => {
+server.setRequestHandler(GetPromptRequestSchema, async (request) => {
   const { name, arguments: args = {} } = request.params;
   if (name === "brief") {
     const topic = typeof args.topic === "string" ? args.topic : "(missing)";

__tests__/fixtures/tools-only-server.mjs

@@ -1,5 +1,6 @@
-import { Server } from "@modelcontextprotocol/server";
-import { StdioServerTransport } from "@modelcontextprotocol/server/stdio";
+import { Server } from "@modelcontextprotocol/sdk/server/index.js";
+import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
+import { CallToolRequestSchema, ListToolsRequestSchema } from "@modelcontextprotocol/sdk/types.js";
 
 // A minimal MCP server that advertises tools only — no `resources`, no
 // `prompts`. Used by resources-capability.test.ts to check that the adapter
@@ -9,11 +10,11 @@ const server = new Server(
   { capabilities: { tools: {} } },
 );
 
-server.setRequestHandler("tools/list", async () => ({
+server.setRequestHandler(ListToolsRequestSchema, async () => ({
   tools: [{ name: "noop", inputSchema: { type: "object", properties: {} } }],
 }));
 
-server.setRequestHandler("tools/call", async () => ({
+server.setRequestHandler(CallToolRequestSchema, async () => ({
   content: [{ type: "text", text: "ok" }],
 }));
 

__tests__/json-schema-validator.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from "vitest";
-import type { JsonSchemaType } from "@modelcontextprotocol/client";
+import type { JsonSchemaType } from "@modelcontextprotocol/sdk/validation/types.js";
 import { createJsonSchemaValidator } from "../json-schema-validator.ts";
 
 const draft07 = "http://json-schema.org/draft-07/schema#";
@@ -64,16 +64,32 @@ describe("createJsonSchemaValidator", () => {
       required: ["values"],
     };
 
-    expect(validate(schema, { values: ["ok", 1] }).valid).toBe(true);
-    expect(validate(schema, { values: ["ok", 1, true] }).valid).toBe(false);
-    expect(validate({ $schema: "https://json-schema.org/draft/2020-12/schema", ...schema }, { values: ["ok", 1] }).valid).toBe(true);
+    for (const candidate of [schema, { $schema: "https://json-schema.org/draft/2020-12/schema", ...schema }]) {
+      expect(validate(candidate, { values: ["ok", 1] }).valid).toBe(true);
+      expect(validate(candidate, { values: ["ok", 1, true] }).valid).toBe(false);
+    }
+  });
+
+  it("accepts unstamped schemas that use draft-07-compatible keywords", () => {
+    const schema = {
+      type: "object",
+      properties: {
+        name: { type: "string", minLength: 1 },
+      },
+      required: ["name"],
+      additionalProperties: false,
+    };
+
+    expect(validate(schema, { name: "ok" }).valid).toBe(true);
+    expect(validate(schema, { name: "" }).valid).toBe(false);
+    expect(validate(schema, { name: "ok", extra: true }).valid).toBe(false);
   });
 
   it("does not downgrade an unsupported explicit dialect", () => {
     expect(() => validate({
       $schema: "https://example.com/custom-schema",
       type: "object",
-    }, {})).toThrow(/unsupported dialect|2020-12/i);
+    }, {})).toThrow(/unsupported.*dialect|2020-12/i);
   });
 
   it("creates isolated validator providers", () => {