feat(mcp): add SSE support with fallback mechanism for MCP connections

- Add McpSseClient implementation for classic HTTP+SSE MCP protocol
- Implement connectBailianMcpWithFallback with Streamable HTTP to SSE fallback
- Add isStreamableHttpUnsupported helper to detect 405 streamableHttp errors
- Update activate-hint logic to handle WebSearch 405 streamableHttp cases
- Replace direct MCP client usage with connection manager in call/tools commands
- Add proper client cleanup with close() calls in finally blocks
- Export new MCP connection utilities and types from core client module
- Add comprehensive tests for SSE client and fallback behavior

Author: hopelynd

packages/commands/src/commands/mcp/activate-hint.ts

@@ -1,4 +1,4 @@
-import { BailianError } from "bailian-cli-core";
+import { BailianError, isStreamableHttpUnsupported } from "bailian-cli-core";
 import { mcpMarketplaceDetailPage } from "bailian-cli-runtime";
 
 /** Detect MCP-not-activated / invalid 404 errors (CLI-wrapped server message). */
@@ -26,14 +26,28 @@ export function mcpActivateHint(serverCode: string): string {
 /**
  * For not-activated errors, keep the original message / exitCode and append a hint only.
  * Do not replace the server error message.
+ * WebSearch + 405 streamableHttp: do not fall back; attach a re-activate / upgrade hint.
  */
 export function rethrowWithMcpActivateHint(error: unknown, serverCode: string): never {
-  if (isMcpNotActivated(error) && error instanceof BailianError && !error.hint) {
+  if (!(error instanceof BailianError) || error.hint) {
+    throw error;
+  }
+
+  if (isMcpNotActivated(error)) {
+    throw new BailianError(error.message, error.exitCode, mcpActivateHint(serverCode), {
+      cause: error,
+      api: error.api,
+      rawResponse: error.rawResponse,
+    });
+  }
+
+  if (serverCode === "WebSearch" && isStreamableHttpUnsupported(error)) {
     throw new BailianError(error.message, error.exitCode, mcpActivateHint(serverCode), {
       cause: error,
       api: error.api,
       rawResponse: error.rawResponse,
     });
   }
+
   throw error;
 }

packages/commands/src/commands/mcp/call.ts

@@ -114,14 +114,14 @@ export default defineCommand({
     const { serverCode, toolName } = parseTarget(flags.target);
     const toolArgs = buildToolArgs(flags);
 
-    const url = flags.url || ctx.client.url(bailianMcpPath(serverCode));
+    const previewUrl = flags.url || ctx.client.url(bailianMcpPath(serverCode));
     const format = detectOutputFormat(settings.output);
 
     if (settings.dryRun) {
       emitResult(
         {
           server: serverCode,
-          url,
+          url: previewUrl,
           tool: toolName,
           arguments: toolArgs,
         },
@@ -130,13 +130,14 @@ export default defineCommand({
       return;
     }
 
-    const client = ctx.client.mcp(url);
+    let client: { close?(): void } | undefined;
     try {
-      await client.initialize();
-      const result = await client.callTool(toolName, toolArgs);
+      const connected = await ctx.client.connectBailianMcp(serverCode, flags.url);
+      client = connected.client;
+      const result = await connected.client.callTool(toolName, toolArgs);
 
       if (result.isError) {
-        const errText = result.content.map((c) => c.text || "").join("\n");
+        const errText = result.content.map((contentItem) => contentItem.text || "").join("\n");
         throw new BailianError(`Tool error: ${errText}`);
       }
 
@@ -146,6 +147,8 @@ export default defineCommand({
         rethrowWithMcpActivateHint(error, serverCode);
       }
       throw error;
+    } finally {
+      client?.close?.();
     }
   },
 });

packages/commands/src/commands/mcp/tools.ts

@@ -28,24 +28,27 @@ export default defineCommand({
     const { settings, flags } = ctx;
     const code = flags.server;
 
-    const url = flags.url || ctx.client.url(bailianMcpPath(code));
+    const previewUrl = flags.url || ctx.client.url(bailianMcpPath(code));
     const format = detectOutputFormat(settings.output);
 
     if (settings.dryRun) {
-      emitResult({ server: code, url, action: "tools/list" }, format);
+      emitResult({ server: code, url: previewUrl, action: "tools/list" }, format);
       return;
     }
 
-    const client = ctx.client.mcp(url);
+    let client: { close?(): void } | undefined;
     try {
-      await client.initialize();
-      const tools = await client.listTools();
-      emitResult({ server: code, url, tools }, format);
+      const connected = await ctx.client.connectBailianMcp(code, flags.url);
+      client = connected.client;
+      const tools = await connected.client.listTools();
+      emitResult({ server: code, url: connected.url, tools }, format);
     } catch (error) {
       if (!flags.url) {
         rethrowWithMcpActivateHint(error, code);
       }
       throw error;
+    } finally {
+      client?.close?.();
     }
   },
 });

packages/commands/tests/mcp-activate-hint.test.ts

@@ -38,6 +38,36 @@ describe("mcp-activate-hint", () => {
     expect(mcpActivateHint("WebSearch")).toMatch(/SSE|Streamable HTTP/i);
   });
 
+  test("WebSearch + 405 streamableHttp 补重开通 hint", () => {
+    const original = new BailianError(
+      "MCP request failed: 405 Method Not Allowed - current mcp not support streamableHttp",
+      ExitCode.GENERAL,
+    );
+    try {
+      rethrowWithMcpActivateHint(original, "WebSearch");
+      expect.unreachable("should throw");
+    } catch (error) {
+      expect(error).toBeInstanceOf(BailianError);
+      const wrapped = error as BailianError;
+      expect(wrapped.message).toBe(original.message);
+      expect(wrapped.hint).toMatch(/SSE|Streamable HTTP|Activate|re-activate/i);
+      expect(wrapped.hint).toContain(mcpMarketplaceDetailPage("WebSearch"));
+    }
+  });
+
+  test("非 WebSearch 的 405 streamableHttp 不补 hint（由 fallback 处理）", () => {
+    const original = new BailianError(
+      "MCP request failed: 405 Method Not Allowed - current mcp not support streamableHttp",
+      ExitCode.GENERAL,
+    );
+    try {
+      rethrowWithMcpActivateHint(original, "WebParser");
+      expect.unreachable("should throw");
+    } catch (error) {
+      expect(error).toBe(original);
+    }
+  });
+
   test("rethrow 保留原 message，补 hint", () => {
     const serverCode = "market-cmapi00073529";
     const original = new BailianError(

packages/core/src/client/client.ts

@@ -5,7 +5,13 @@ import { ExitCode } from "../errors/codes.ts";
 import { request, requestJson, type HttpDeps, type RequestOpts } from "./http.ts";
 import { buildAcsCanonicalQuery, signAcsRequest, type AcsQueryParams } from "./acs.ts";
 import { imageFileToDataUri, isLocalFile, resolveFileUrl } from "../files/upload.ts";
-import { McpClient } from "./mcp.ts";
+import {
+  bailianMcpPath,
+  bailianMcpSsePath,
+  connectBailianMcpWithFallback,
+  McpClient,
+  type McpConnectedClient,
+} from "./mcp.ts";
 import { callConsoleGateway } from "../console/gateway.ts";
 import { refreshAccessToken } from "../auth/refresh-token.ts";
 import { maskToken } from "../utils/token.ts";
@@ -164,6 +170,25 @@ export class Client {
     return new McpClient(this.http, url, this.deps.apiCred?.token);
   }
 
+  /**
+   * Connect to a Bailian MCP: try Streamable HTTP, then SSE on 405+streamableHttp (except WebSearch).
+   * `urlOverride` maps to `--url` and uses Streamable only (no fallback).
+   */
+  connectBailianMcp(
+    serverCode: string,
+    urlOverride?: string,
+  ): Promise<{ client: McpConnectedClient; url: string }> {
+    this.requireApi();
+    return connectBailianMcpWithFallback({
+      deps: this.http,
+      authToken: this.deps.apiCred?.token,
+      httpUrl: this.url(bailianMcpPath(serverCode)),
+      sseUrl: this.url(bailianMcpSsePath(serverCode)),
+      serverCode,
+      urlOverride,
+    });
+  }
+
   async console<T>(api: string, data: Record<string, unknown>): Promise<T> {
     if (!this.deps.consoleCred) {
       throw new BailianError("This command needs a console access token.", ExitCode.AUTH);

packages/core/src/client/index.ts

@@ -57,7 +57,18 @@ export {
   type AcsQueryParams,
   type AcsSignConfig,
 } from "./acs.ts";
-export type { McpTool, McpToolResult } from "./mcp.ts";
-export { McpClient, bailianMcpPath } from "./mcp.ts";
+export type {
+  McpTool,
+  McpToolResult,
+  McpConnectedClient,
+  ConnectBailianMcpOptions,
+} from "./mcp.ts";
+export {
+  McpClient,
+  bailianMcpPath,
+  bailianMcpSsePath,
+  isStreamableHttpUnsupported,
+  connectBailianMcpWithFallback,
+} from "./mcp.ts";
 export type { ServerSentEvent } from "./stream.ts";
 export { parseSSE } from "./stream.ts";