fix: acp/zed race condition between MCP initialisation and prompt (#20205)

Signed-off-by: Kartik Angiras <angiraskartik@gmail.com>

packages/core/src/config/config.ts

@@ -716,6 +716,7 @@ export class Config implements McpContext {
   private compressionTruncationCounter = 0;
   private initialized = false;
   private initPromise: Promise<void> | undefined;
+  private mcpInitializationPromise: Promise<void> | null = null;
   readonly storage: Storage;
   private readonly fileExclusions: FileExclusions;
   private readonly eventEmitter?: EventEmitter;
@@ -1124,7 +1125,7 @@ export class Config implements McpContext {
     );
     // We do not await this promise so that the CLI can start up even if
     // MCP servers are slow to connect.
-    const mcpInitialization = Promise.allSettled([
+    this.mcpInitializationPromise = Promise.allSettled([
       this.mcpClientManager.startConfiguredMcpServers(),
       this.getExtensionLoader().start(this),
     ]).then((results) => {
@@ -1136,7 +1137,7 @@ export class Config implements McpContext {
     });
 
     if (!this.interactive || this.experimentalZedIntegration) {
-      await mcpInitialization;
+      await this.mcpInitializationPromise;
     }
 
     if (this.skillsSupport) {
@@ -2234,6 +2235,12 @@ export class Config implements McpContext {
     return this.experimentalZedIntegration;
   }
 
+  async waitForMcpInit(): Promise<void> {
+    if (this.mcpInitializationPromise) {
+      await this.mcpInitializationPromise;
+    }
+  }
+
   getListExtensions(): boolean {
     return this.listExtensions;
   }