fix: app user agent for api-client reqs using tauri http plugin (#6045)

fix: app user agent

packages/api-client/src/core/abstract-client.ts

@@ -125,13 +125,15 @@ export abstract class AbstractModrinthClient extends AbstractUploadClient {
 
 		const url = this.buildUrl(path, baseUrl, options.version)
 
+		const defaultHeaders = await this.buildDefaultHeaders()
+
 		// Merge options with defaults
 		const mergedOptions: RequestOptions = {
 			method: 'GET',
 			timeout: this.config.timeout,
 			...options,
 			headers: {
-				...this.buildDefaultHeaders(),
+				...defaultHeaders,
 				...options.headers,
 			},
 		}
@@ -306,19 +308,25 @@ export abstract class AbstractModrinthClient extends AbstractUploadClient {
 	 * Subclasses can override this to add platform-specific headers
 	 * (e.g., Nuxt rate limit key)
 	 */
-	protected buildDefaultHeaders(): Record<string, string> {
+	protected async buildDefaultHeaders(): Promise<Record<string, string>> {
 		const headers: Record<string, string> = {
 			'Content-Type': 'application/json',
 			...this.config.headers,
 		}
 
-		if (this.config.userAgent) {
-			headers['User-Agent'] = this.config.userAgent
+		const userAgent = await this.resolveUserAgent()
+		if (userAgent) {
+			headers['User-Agent'] = userAgent
 		}
 
 		return headers
 	}
 
+	private async resolveUserAgent(): Promise<string | undefined> {
+		const userAgent = this.config.userAgent
+		return typeof userAgent === 'function' ? await userAgent() : userAgent
+	}
+
 	protected attachArchonSentryCaptureHeader(options: RequestOptions): void {
 		if (options.api !== 'archon' || !options.headers || !this.shouldCaptureArchonRequests()) {
 			return
@@ -404,7 +412,7 @@ export abstract class AbstractModrinthClient extends AbstractUploadClient {
 	 * @example
 	 * ```typescript
 	 * const client = new GenericModrinthClient()
-	 * client.addFeature(new AuthFeature({ token: 'mrp_...' }))
+	 * client.addFeature(new AuthFeature({ token: async () => getOAuthToken() }))
 	 * client.addFeature(new RetryFeature({ maxAttempts: 3 }))
 	 * ```
 	 */