feat(typescript): expose protocols field on WebSocket ConnectArgs (#13588)

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: Swimburger

generators/typescript/sdk/client-class-generator/src/websocket/GeneratedDefaultWebsocketImplementation.ts

@@ -42,6 +42,7 @@ export class GeneratedDefaultWebsocketImplementation implements GeneratedWebsock
     private static readonly HEADERS_PROPERTY_NAME = "headers";
     private static readonly HEADERS_VARIABLE_NAME = "_headers";
 
+    private static readonly PROTOCOLS_PROPERTY_NAME = "protocols";
     private static readonly RECONNECT_ATTEMPTS_PROPERTY_NAME = "reconnectAttempts";
     private static readonly CONNECTION_TIMEOUT_PROPERTY_NAME = "connectionTimeoutInSeconds";
     private static readonly ABORT_SIGNAL_PROPERTY_NAME = "abortSignal";
@@ -188,6 +189,19 @@ export class GeneratedDefaultWebsocketImplementation implements GeneratedWebsock
                         hasQuestionToken: context.type.isOptional(header.valueType)
                     };
                 }),
+                {
+                    name: GeneratedDefaultWebsocketImplementation.PROTOCOLS_PROPERTY_NAME,
+                    type: getTextOfTsNode(
+                        ts.factory.createUnionTypeNode([
+                            ts.factory.createKeywordTypeNode(ts.SyntaxKind.StringKeyword),
+                            ts.factory.createArrayTypeNode(
+                                ts.factory.createKeywordTypeNode(ts.SyntaxKind.StringKeyword)
+                            )
+                        ])
+                    ),
+                    hasQuestionToken: true,
+                    docs: ["WebSocket subprotocols to use for the connection."]
+                },
                 {
                     name: GeneratedDefaultWebsocketImplementation.ADDITIONAL_QUERY_PARAMETERS_PROPERTY_NAME,
                     type: getTextOfTsNode(
@@ -302,6 +316,15 @@ export class GeneratedDefaultWebsocketImplementation implements GeneratedWebsock
             );
         }
 
+        // Add protocols binding
+        bindingElements.push(
+            ts.factory.createBindingElement(
+                undefined,
+                undefined,
+                ts.factory.createIdentifier(GeneratedDefaultWebsocketImplementation.PROTOCOLS_PROPERTY_NAME)
+            )
+        );
+
         // Add additional query parameters binding
         bindingElements.push(
             ts.factory.createBindingElement(
@@ -534,7 +557,11 @@ export class GeneratedDefaultWebsocketImplementation implements GeneratedWebsock
 
         return context.coreUtilities.websocket.ReconnectingWebSocket._connect({
             url: context.coreUtilities.urlUtils.join._invoke([baseUrl, url]),
-            protocols: ts.factory.createArrayLiteralExpression([]),
+            protocols: ts.factory.createBinaryExpression(
+                ts.factory.createIdentifier(GeneratedDefaultWebsocketImplementation.PROTOCOLS_PROPERTY_NAME),
+                ts.factory.createToken(ts.SyntaxKind.QuestionQuestionToken),
+                ts.factory.createArrayLiteralExpression([])
+            ),
             options: ts.factory.createObjectLiteralExpression([
                 ts.factory.createPropertyAssignment(
                     "debug",

generators/typescript/sdk/versions.yml

@@ -1,4 +1,16 @@
 # yaml-language-server: $schema=../../../fern-versions-yml.schema.json
+- version: 3.57.0
+  changelogEntry:
+    - summary: |
+        Expose an optional `protocols` field on `RealtimeClient.ConnectArgs` for WebSocket
+        subprotocol negotiation. The `ReconnectingWebSocket` constructor already accepted a
+        `protocols` parameter but it was hardcoded to an empty array. Browser callers can now
+        authenticate via subprotocols (e.g. `xai-client-secret.<token>`) where custom headers
+        are forbidden by the browser security model.
+      type: feat
+  createdAt: "2026-03-16"
+  irVersion: 65
+
 - version: 3.56.4
   changelogEntry:
     - summary: |