diff --git a/java-client/src/main/java/co/elastic/clients/transport/ElasticsearchTransportBase.java b/java-client/src/main/java/co/elastic/clients/transport/ElasticsearchTransportBase.java
index 51e4d8ef50..98a51facec 100644
--- a/java-client/src/main/java/co/elastic/clients/transport/ElasticsearchTransportBase.java
+++ b/java-client/src/main/java/co/elastic/clients/transport/ElasticsearchTransportBase.java
@@ -62,6 +62,7 @@
 import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
 
 public abstract class ElasticsearchTransportBase implements ElasticsearchTransport {
 
@@ -150,7 +151,21 @@ public final <RequestT, ResponseT, ErrorT> ResponseT performRequest(
                 TransportHttpClient.Request req = prepareTransportRequest(request, endpoint);
                 ctx.beforeSendingHttpRequest(req, options);
 
-                TransportHttpClient.Response resp = httpClient.performRequest(endpoint.id(), null, req, opts);
+                CompletableFuture<TransportHttpClient.Response> future =
+                    httpClient.performRequestAsync(endpoint.id(), null, req, opts);
+                TransportHttpClient.Response resp;
+                try {
+                    resp = future.get();
+                } catch (InterruptedException e) {
+                    future.cancel(true);
+                    Thread.currentThread().interrupt();
+                    throw new IOException("request was interrupted", e);
+                } catch (ExecutionException e) {
+                    Throwable cause = e.getCause();
+                    if (cause instanceof IOException ioe) throw ioe;
+                    if (cause instanceof RuntimeException re) throw re;
+                    throw new IOException(cause);
+                }
                 ctx.afterReceivingHttpResponse(resp);
 
                 ResponseT apiResponse = getApiResponse(resp, endpoint);
diff --git a/java-client/src/test/java/co/elastic/clients/transport/InterruptSyncRequestTest.java b/java-client/src/test/java/co/elastic/clients/transport/InterruptSyncRequestTest.java
new file mode 100644
index 0000000000..e9185fc616
--- /dev/null
+++ b/java-client/src/test/java/co/elastic/clients/transport/InterruptSyncRequestTest.java
@@ -0,0 +1,133 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package co.elastic.clients.transport;
+
+import co.elastic.clients.elasticsearch.ElasticsearchAsyncClient;
+import co.elastic.clients.elasticsearch.ElasticsearchClient;
+import co.elastic.clients.elasticsearch.ElasticsearchTestClient;
+import com.sun.net.httpserver.HttpServer;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.Timeout;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.util.Collections;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.LockSupport;
+
+/**
+ * Verifies that cancelling an in-flight ES client request closes the underlying HTTP connection.
+ */
+public class InterruptSyncRequestTest extends Assertions {
+
+    /**
+     * Creates an HttpServer whose {@code /_count} handler streams bytes until
+     * the client disconnects (causing a write failure) or 30 seconds elapse.
+     * If the client disconnects, the resulting {@code IOException} is delivered
+     * via {@code serverException}.
+     */
+    private static HttpServer createSlowServer(
+        CountDownLatch requestArrived, CompletableFuture<Exception> serverException
+    ) throws Exception {
+        HttpServer httpServer = HttpServer.create(new InetSocketAddress(InetAddress.getLoopbackAddress(), 0), 0);
+
+        httpServer.createContext("/_count", exchange -> {
+            try (exchange; OutputStream out = exchange.getResponseBody()) {
+                exchange.getResponseHeaders().put("X-Elastic-Product", Collections.singletonList("Elasticsearch"));
+                exchange.getResponseHeaders().put("Content-Type", Collections.singletonList("application/json"));
+                exchange.sendResponseHeaders(200, 0);
+
+                requestArrived.countDown();
+
+                // Stream data slowly for 30 seconds. Throws IOException on client disconnect.
+                for (int i = 0; i < 30_000; i++) {
+                    out.write(' ');
+                    out.flush();
+                    LockSupport.parkNanos(1_000_000L);
+                }
+            } catch (Exception e) {
+                serverException.complete(e);
+            } finally {
+                serverException.complete(null);
+            }
+        });
+
+        return httpServer;
+    }
+
+    @Test
+    @Timeout(10)
+    public void syncRequestShouldStopWhenCallingThreadIsInterrupted() throws Exception {
+        CountDownLatch requestArrived = new CountDownLatch(1);
+        CompletableFuture<Exception> serverException = new CompletableFuture<>();
+
+        HttpServer httpServer = createSlowServer(requestArrived, serverException);
+        httpServer.start();
+        try {
+            ElasticsearchClient client = ElasticsearchTestClient.createClient(httpServer, null);
+
+            Thread clientThread = new Thread(() -> {
+                try { client.count(); } catch (Exception e) { }
+            });
+            clientThread.start();
+
+            assertTrue(requestArrived.await(5, TimeUnit.SECONDS));
+            clientThread.interrupt();
+
+            // The server should get an IOException from writing to the closed connection.
+            // If the connection leaked, the future completes with null after the handler finishes.
+            assertInstanceOf(IOException.class, serverException.join(),
+                "HTTP connection should have been closed after thread interruption");
+        } finally {
+            httpServer.stop(0);
+        }
+    }
+
+    @Test
+    @Timeout(10)
+    public void asyncRequestShouldStopWhenFutureIsCancelled() throws Exception {
+        CountDownLatch requestArrived = new CountDownLatch(1);
+        CompletableFuture<Exception> serverException = new CompletableFuture<>();
+
+        HttpServer httpServer = createSlowServer(requestArrived, serverException);
+        httpServer.start();
+        try {
+            ElasticsearchClient syncClient = ElasticsearchTestClient.createClient(httpServer, null);
+            ElasticsearchAsyncClient client = new ElasticsearchAsyncClient(syncClient._transport());
+
+            CompletableFuture<?> future = client.count();
+
+            assertTrue(requestArrived.await(5, TimeUnit.SECONDS));
+            future.cancel(true);
+
+            // The server should get an IOException from writing to the closed connection.
+            // If the connection leaked, the future completes with null after the handler finishes.
+            assertInstanceOf(IOException.class, serverException.join(),
+                "HTTP connection should have been closed after future cancellation");
+        } finally {
+            httpServer.stop(0);
+        }
+    }
+}