fix: request URL is incorrectly rewritten when baseUrl is configured as a proxy address

src/main/java/com/google/genai/ApiClient.java

@@ -534,13 +534,24 @@ protected Request buildRequest(
       try {
         URI originalUri = new URI(url);
         URI baseUri = new URI(mergedHttpOptions.baseUrl().get());
+
+        String baseUriPath = baseUri.getRawPath() != null ? baseUri.getRawPath() : "";
+        String originalUriPath = originalUri.getRawPath() != null ? originalUri.getRawPath() : "";
+
+        String combinedPath;
+        if (baseUriPath.endsWith("/") && originalUriPath.startsWith("/")) {
+          combinedPath = baseUriPath + originalUriPath.substring(1);
+        } else {
+          combinedPath = baseUriPath + originalUriPath;
+        }
+
         finalUrl =
             new URI(
                     baseUri.getScheme(),
-                    baseUri.getAuthority(),
-                    originalUri.getPath(),
-                    originalUri.getQuery(),
-                    originalUri.getFragment())
+                    baseUri.getRawAuthority(),
+                    combinedPath,
+                    originalUri.getRawQuery(),
+                    originalUri.getRawFragment())
                 .toString();
       } catch (URISyntaxException e) {
         logger.warning("Failed to rewrite upload URL with base URL: " + e.getMessage());

src/test/java/com/google/genai/ClientTest.java

@@ -20,19 +20,15 @@
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.when;
-import org.mockito.MockedStatic;
-import org.mockito.Mockito;
 
 import com.google.auth.oauth2.GoogleCredentials;
 import com.google.common.collect.ImmutableMap;
 import com.google.genai.types.HttpOptions;
-import java.lang.reflect.Field;
 import java.util.Optional;
-import okhttp3.OkHttpClient;
+import java.util.concurrent.CompletableFuture;
 import org.junit.jupiter.api.Test;
-
+import org.mockito.MockedStatic;
+import org.mockito.Mockito;
 
 public class ClientTest {
   private static final String API_KEY = "api-key";
@@ -365,4 +361,55 @@ void defaultIsFalse_whenNoFlagsOrEnvsAreSet() {
       assertFalse(client.vertexAI());
     }
   }
+
+  static class TestApiClient extends ApiClient {
+    TestApiClient(HttpOptions httpOptions) {
+      super(Optional.of("dummy-api-key"), Optional.of(httpOptions), Optional.empty());
+    }
+
+    @Override
+    public ApiResponse request(
+        String httpMethod, String path, String requestJson, Optional<HttpOptions> httpOptions) {
+      return null;
+    }
+
+    @Override
+    public ApiResponse request(
+        String httpMethod, String path, byte[] requestBytes, Optional<HttpOptions> httpOptions) {
+      return null;
+    }
+
+    @Override
+    public CompletableFuture<ApiResponse> asyncRequest(
+        String httpMethod, String path, String requestJson, Optional<HttpOptions> httpOptions) {
+      return null;
+    }
+
+    @Override
+    public CompletableFuture<ApiResponse> asyncRequest(
+        String httpMethod, String path, byte[] requestBytes, Optional<HttpOptions> httpOptions) {
+      return null;
+    }
+
+    @Override
+    public void close() {}
+  }
+
+  @Test
+  void testBuildRequest_preservesBaseUrlPath() throws Exception {
+    HttpOptions httpOptions =
+        HttpOptions.builder().baseUrl("http://my-proxy.company.com/api/Gemini/Proxy").build();
+    TestApiClient client = new TestApiClient(httpOptions);
+
+    okhttp3.Request request =
+        client.buildRequest(
+            "POST",
+            "https://generativelanguage.googleapis.com/upload/v1beta/files?upload_id=xxx",
+            new byte[0],
+            Optional.empty());
+
+    assertEquals(
+        "http://my-proxy.company.com/api/Gemini/Proxy/upload/v1beta/files?upload_id=xxx",
+        request.url().toString());
+  }
 }