Map auth type to telemetry auth enum

- Convert 'access-token' (or undefined) to 'pat'
- Convert 'databricks-oauth' to 'external-browser' (U2M) or 'oauth-m2m' (M2M)
- Distinguish M2M from U2M by checking for oauthClientSecret
- Keep 'custom' as 'custom'

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: samikshya-db

lib/DBSQLClient.ts

@@ -212,7 +212,7 @@ export default class DBSQLClient extends EventEmitter implements IDBSQLClient, I
       localeName: this.getLocaleName(),
       charSetEncoding: 'UTF-8',
       processName: this.getProcessName(),
-      authType: this.authType || 'access-token',
+      authType: this.authType || 'pat',
 
       // Feature flags
       cloudFetchEnabled: this.config.useCloudFetch ?? false,
@@ -227,6 +227,26 @@ export default class DBSQLClient extends EventEmitter implements IDBSQLClient, I
     };
   }
 
+  /**
+   * Map Node.js auth type to telemetry auth enum string.
+   * Distinguishes between U2M and M2M OAuth flows.
+   */
+  private mapAuthType(options: ConnectionOptions): string {
+    if (options.authType === 'databricks-oauth') {
+      // Check if M2M (has client secret) or U2M (no client secret)
+      return options.oauthClientSecret === undefined
+        ? 'external-browser' // U2M OAuth (User-to-Machine)
+        : 'oauth-m2m'; // M2M OAuth (Machine-to-Machine)
+    }
+
+    if (options.authType === 'custom') {
+      return 'custom'; // Custom auth provider
+    }
+
+    // 'access-token' or undefined
+    return 'pat'; // Personal Access Token
+  }
+
   /**
    * Get locale name in format language_country (e.g., en_US).
    * Matches JDBC format: user.language + '_' + user.country
@@ -380,9 +400,9 @@ export default class DBSQLClient extends EventEmitter implements IDBSQLClient, I
       }
     }
 
-    // Store host and auth type for telemetry
+    // Store host and auth type for telemetry (convert to telemetry auth enum)
     this.host = options.host;
-    this.authType = options.authType || 'access-token'; // Default to access-token
+    this.authType = this.mapAuthType(options);
 
     // Store enableMetricViewMetadata configuration
     if (options.enableMetricViewMetadata !== undefined) {

lib/telemetry/types.ts

@@ -210,7 +210,7 @@ export interface DriverConfiguration {
   /** Process name */
   processName: string;
 
-  /** Authentication type (access-token, databricks-oauth, custom) */
+  /** Authentication type (pat, external-browser, oauth-m2m, custom) */
   authType: string;
 
   // Feature flags