fix(ai): make OpenAI Responses session_id header optional closes #3579

packages/ai/src/providers/openai-responses.ts

@@ -180,7 +180,9 @@ function createClient(
 	}
 
 	if (sessionId) {
-		headers.session_id = sessionId;
+		if (model.compat?.sendSessionIdHeader !== false) {
+			headers.session_id = sessionId;
+		}
 		headers["x-client-request-id"] = sessionId;
 	}
 

packages/ai/src/types.ts

@@ -300,7 +300,8 @@ export interface OpenAICompletionsCompat {
 
 /** Compatibility settings for OpenAI Responses APIs. */
 export interface OpenAIResponsesCompat {
-	// Reserved for future use
+	/** Whether to send the OpenAI `session_id` cache-affinity header from `options.sessionId` when caching is enabled. Default: true. */
+	sendSessionIdHeader?: boolean;
 }
 
 /**