feat: Auto-compact workflow builder conversation history (no-changelog) (#18083)

packages/@n8n/ai-workflow-builder.ee/src/utils/token-usage.ts

@@ -0,0 +1,34 @@
+import { AIMessage } from '@langchain/core/messages';
+
+type AIMessageWithUsageMetadata = AIMessage & {
+	response_metadata: {
+		usage: {
+			input_tokens: number;
+			output_tokens: number;
+		};
+	};
+};
+
+export interface TokenUsage {
+	input_tokens: number;
+	output_tokens: number;
+}
+
+/**
+ * Extracts token usage information from the last AI assistant message
+ */
+export function extractLastTokenUsage(messages: unknown[]): TokenUsage | undefined {
+	const lastAiAssistantMessage = messages.findLast(
+		(m): m is AIMessageWithUsageMetadata =>
+			m instanceof AIMessage &&
+			m.response_metadata?.usage !== undefined &&
+			'input_tokens' in m.response_metadata.usage &&
+			'output_tokens' in m.response_metadata.usage,
+	);
+
+	if (!lastAiAssistantMessage) {
+		return undefined;
+	}
+
+	return lastAiAssistantMessage.response_metadata.usage;
+}