v1.40.0

June 18, 2026

🌟 New features

Outlier-Detecting Endpoint Group: You can now wrap any EndpointGroup with OutlierDetectingEndpointGroup to automatically eject failing endpoints from rotation using per-endpoint circuit breakers. #6224 #6757

EndpointGroup delegate = ...;
OutlierDetectingEndpointGroup group =
    OutlierDetectingEndpointGroup.builder(delegate)
                                 .failureRateThreshold(0.3)
                                 .circuitOpenWindow(Duration.ofSeconds(20))
                                 ...
                                 .build();
WebClient client =
    WebClient.builder(SessionProtocol.HTTPS, group)
             .decorator(group.asDecorator()) // 👈👈👈
             .build();

Async gRPC Exception Handler: GrpcExceptionHandlerFunction now supports asynchronous error handling via GrpcExceptionHandlerFunction.applyAsync(). Override applyAsync() to perform non-blocking work during gRPC error response handling. #6697 #6717

GrpcService.builder()
           .addService(myService)
           .exceptionHandler(new GrpcExceptionHandlerFunction() {
               ...
               @Override
               public CompletableFuture<Status> applyAsync( // 👈👈👈
                       RequestContext ctx, Status status,
                       Throwable cause, Metadata metadata) {
                   return myAsyncStatusMapping.check(status, cause);
               }
           })
           .build();

Thrift 0.23.0 Support: Armeria now supports Apache Thrift 0.23.0 via the new thrift0.23 module. A new ThriftProtocolDecorator API lets you customize the TProtocol used for serialization and deserialization. For example, you can use Thrift 0.23's TLegacyUuidProtocolDecorator for legacy UUID wire format compatibility. #6762

ThriftProtocolDecorator decorator =
    ThriftProtocolDecorator.ofTProtocolDecorator(
        TLegacyUuidProtocolDecorator::new); // 👈👈👈
THttpService service =
    THttpService.builder()
                .addService(myHandler)
                .protocolDecorator(decorator)
                .build();
ThriftClients.builder(uri)
             .protocolDecorator(decorator)
             .build(MyService.Iface.class);

Connection Acceptor: You can now accept or reject connections at the transport level before any request processing begins using ConnectionAcceptor. The new ConnectionContext exposes TLS ClientHello metadata (SNI hostname, ALPN protocols) and per-connection attributes, enabling connection-level policies such as blocking by SNI or remote address. #6788
```
Server.builder()
      .connectionAcceptor(ConnectionAcceptor.of(ctx -> { // 👈👈👈
          return !"blocked.example.com".equals(ctx.sniHostname());
      }))
      .build();
```
xDS Credential Injector Filter: xDS extension factories can now build reactive filter pipelines that depend on external resources like SDS secrets. The new CredentialInjectorFilterFactory injects credentials from SDS-backed generic secrets into outgoing HTTP requests, supporting the envoy.filters.http.credential_injector filter type. #6785
Endpoints created by KubernetesEndpointGroup now carry their originating Pod and Node as endpoint attributes. This can be retrieved via KubernetesResourceAccess. #6814

📈 Improvements

Fetching Athenz policies has been optimized by using ETags. When policies haven't changed, the server returns 304 Not Modified, avoiding redundant policy verification. #6780

🛠️ Bug fixes

StaticEndpointGroup.selectNow() no longer returns null when whenReady() is complete and endpoints are available. #6786
Binary fields in TTextProtocol now correctly respect ByteBuffer position and limit instead of serializing the entire backing array. #5768 #6773
GrantedOAuth2AccessToken.toString() no longer leaks OAuth2 access and refresh tokens in log output. #6787
xDS retry now correctly re-selects endpoints on each retry attempt. Previously, retries always reused the same endpoint because the retry decorator was placed after endpoint selection. #6798

☢️ Breaking changes

Apache Thrift 0.23.0 changes the UUID wire format, breaking compatibility with older Thrift peers. Use TLegacyUuidProtocolDecorator via ThriftProtocolDecorator to restore the legacy behavior. #6762