v1.39.0

May 13, 2026

🌟 New features

Proto Transcoding for HTTP/JSON-to-gRPC Proxy: DelegatingHttpJsonTranscodingService can now forward transcoded requests using protobuf binary encoding via DelegatingHttpJsonTranscodingServiceBuilder.protoSerialization(). This enables interoperability with upstream gRPC services that only accept application/grpc+proto. #6670
```
DelegatingHttpJsonTranscodingService.builder(delegate)
    .serviceDescriptors(MyServiceGrpc.getServiceDescriptor())
    .protoSerialization(true) // 👈👈👈
    .build();
```

Multipart Body Part Deserialization via @Part: You can now deserialize structured data (e.g., JSON) from multipart body parts using the new @Part annotation. #6763

@Post("/upload")
@Consumes(MediaTypeNames.MULTIPART_FORM_DATA)
public HttpResponse upload(@Part MyBean metadata, // 👈👈👈
                           @Part MultipartFile file) { ... }

Custom Default ClientFactory via FlagsProvider: You can now customize the built-in default client factories through FlagsProvider.defaultClientFactoryConfigurator(). #6425 #6671

public class MyFlagsProvider implements FlagsProvider {
    @Override
    public ClientFactoryConfigurator defaultClientFactoryConfigurator() {
        return builder -> builder.maxNumEventLoopsPerEndpoint(8); // 👈👈👈
    }
}

xDS File-Based Config Source: You can now use path_config_source in your xDS bootstrap to load xDS resources from local YAML or JSON files, with automatic file watching for updates. #6747
xDS Custom Config Source SPI: You can implement SotwConfigSourceSubscriptionFactory to plug in custom non-gRPC config sources (e.g., etcd, Consul, ZooKeeper) via the ServiceLoader SPI. #6747
xDS Resource Reader: XdsResourceReader is now available as a public utility for parsing Envoy protobuf types from YAML/JSON. #6747
Delta xDS Protocol Support: Armeria's xDS client now supports the incremental (delta) xDS protocol (DELTA_GRPC / AGGREGATED_DELTA_GRPC), enabling compatibility with control planes like Istiod that prefer the delta protocol. #6709
xDS Pipe Address Support: xDS endpoints using pipe (Unix domain socket) addresses are now resolved correctly, converted to DomainSocketAddress. #6708

📈 Improvements

The useHttp2Preface flag now controls the order of HTTP/2 strategies rather than being an exclusive choice. Both preface and upgrade are tried before falling back to HTTP/1.1. #6731 #6738
FileService now includes the requested file path in 404 response bodies, making it easier to debug which mapped path failed to resolve. #4797 #6744
You can now set alpnProtocols and endpointIdentificationAlgorithm to ClientTlsSpec for fine-grained TLS control needed by xDS-based mTLS. #6730
Armeria's xDS client now validates unsupported xDS fields using proto field annotations. #6722 #6736

🛠️ Bug fixes

TCP_USER_TIMEOUT no longer overflows when idleTimeoutMillis is near Long.MAX_VALUE. Previously, adding the buffer to Long.MAX_VALUE caused a wrap to Integer.MIN_VALUE, which Linux rejected. It now saturates to Integer.MAX_VALUE. #6711

📃 Documentation

You can now search the site content from the global navigation bar via a search pop-up and a dedicated search page. #6737
Added documentation for GracefulShutdown covering quiet period and timeout phases, custom shutdown responses, and Spring Boot integration. #6345 #6713