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import type { McpServerSseConfig } from './config-schema';
import { Client } from '@modelcontextprotocol/sdk/client/index.js';
import type { OAuthClientProvider } from '@modelcontextprotocol/sdk/client/auth.js';
import { SSEClientTransport, SseError } from '@modelcontextprotocol/sdk/client/sse.js';
import {
buildRequestOptions,
KIMI_MCP_CLIENT_NAME,
KIMI_MCP_CLIENT_VERSION,
MCP_LIVENESS_PROBE_TIMEOUT_MS,
toMcpToolDefinition,
toMcpToolResult,
type UnexpectedCloseListener,
type UnexpectedCloseReason,
} from './client-shared';
import { buildMcpRemoteHeaders } from './client-remote';
import { createMcpOAuthFetch } from './oauth/provider';
import type { MCPClient, MCPToolDefinition, MCPToolResult } from './types';
export interface SseMcpClientOptions {
readonly clientName?: string;
readonly clientVersion?: string;
readonly startupTimeoutMs?: number;
readonly toolCallTimeoutMs?: number;
readonly envLookup?: (name: string) => string | undefined;
readonly fetch?: typeof fetch;
readonly oauthProvider?: OAuthClientProvider;
}
export class SseMcpClient implements MCPClient {
private readonly client: Client;
private readonly transport: SSEClientTransport;
private readonly startupTimeoutMs?: number;
private readonly toolCallTimeoutMs?: number;
private started = false;
private closed = false;
private ready = false;
private hooksInstalled = false;
private unexpectedCloseListener: UnexpectedCloseListener | undefined;
private lastTransportError: Error | undefined;
private pendingUnexpectedClose: UnexpectedCloseReason | undefined;
private unexpectedCloseFired = false;
constructor(config: McpServerSseConfig, options: SseMcpClientOptions = {}) {
const envLookup = options.envLookup ?? ((name) => process.env[name]);
const headers = buildMcpRemoteHeaders(config, envLookup);
this.transport = new SSEClientTransport(new URL(config.url), {
requestInit: headers !== undefined ? { headers } : undefined,
fetch: createMcpOAuthFetch(options.oauthProvider, options.fetch),
authProvider: options.oauthProvider,
});
this.client = new Client({
name: options.clientName ?? KIMI_MCP_CLIENT_NAME,
version: options.clientVersion ?? KIMI_MCP_CLIENT_VERSION,
});
this.startupTimeoutMs = options.startupTimeoutMs;
this.toolCallTimeoutMs = options.toolCallTimeoutMs;
}
async connect(): Promise<void> {
if (this.closed) {
throw new Error2(ErrorCodes.MCP_STARTUP_FAILED, 'MCP SSE client is closed');
}
if (this.started) return;
this.started = true;
this.installTransportHooks();
try {
await this.client.connect(
this.transport,
buildRequestOptions(this.startupTimeoutMs, undefined),
);
} catch (error) {
await this.closeStartedClient();
throw error;
}
if (this.closed) {
await this.closeStartedClient();
throw new Error2(ErrorCodes.MCP_STARTUP_FAILED, 'MCP SSE client was closed during startup');
}
this.ready = true;
}
async close(): Promise<void> {
if (this.closed) return;
this.closed = true;
await this.closeStartedClient();
}
onUnexpectedClose(listener: UnexpectedCloseListener): void {
this.unexpectedCloseListener = listener;
const pending = this.pendingUnexpectedClose;
if (pending !== undefined) {
this.pendingUnexpectedClose = undefined;
listener(pending);
}
}
async listTools(): Promise<MCPToolDefinition[]> {
const result = await this.client.listTools(
undefined,
buildRequestOptions(this.startupTimeoutMs, undefined),
);
return result.tools.map(toMcpToolDefinition);
}
async callTool(
name: string,
args: Record<string, unknown>,
signal?: AbortSignal,
): Promise<MCPToolResult> {
const requestOptions = buildRequestOptions(this.toolCallTimeoutMs, signal);
const result = await this.client.callTool({ name, arguments: args }, undefined, requestOptions);
return toMcpToolResult(result);
}
async ping(signal?: AbortSignal): Promise<void> {
await this.client.ping(buildRequestOptions(MCP_LIVENESS_PROBE_TIMEOUT_MS, signal));
}
private async closeStartedClient(): Promise<void> {
if (!this.started) return;
this.started = false;
await this.client.close();
}
private installTransportHooks(): void {
if (this.hooksInstalled) return;
this.hooksInstalled = true;
this.client.onclose = () => {
if (this.closed) return;
if (!this.ready) return;
this.fireUnexpectedClose({ error: this.lastTransportError });
};
this.client.onerror = (error) => {
this.lastTransportError = error;
if (this.closed) return;
if (!this.ready) return;
if (isTerminalSseTransportError(error)) {
this.fireUnexpectedClose({ error });
}
};
}
private fireUnexpectedClose(reason: UnexpectedCloseReason): void {
if (this.unexpectedCloseFired) return;
this.unexpectedCloseFired = true;
const listener = this.unexpectedCloseListener;
if (listener !== undefined) {
listener(reason);
} else {
this.pendingUnexpectedClose = reason;
}
}
}
export function isTerminalSseTransportError(error: Error): boolean {
if (error.name === 'UnauthorizedError') return true;
return error instanceof SseError && error.code !== undefined;
}
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