JDK-8283544 addressed the issue where HttpClient was adding a Content-Length: 0 request header for a GET request. The test/jdk/java/net/httpclient/ContentLengthHeaderTest.java, which was added as part of that fix, continues to reproduce the original issue if it is changed to issue the GET request as follows:

diff --git a/test/jdk/java/net/httpclient/ContentLengthHeaderTest.java b/test/jdk/java/net/httpclient/ContentLengthHeaderTest.java
index 0ff21c23a8f..16b117b8a66 100644
--- a/test/jdk/java/net/httpclient/ContentLengthHeaderTest.java
+++ b/test/jdk/java/net/httpclient/ContentLengthHeaderTest.java
@@ -142,7 +142,7 @@ public void getWithNoBody(Version version, URI uri) throws IOException, Interrup
         testLog.println(version + " Checking GET with no request body");
         HttpRequest req = HttpRequest.newBuilder()
                 .version(version)
- .GET()
+ .method("GET", HttpRequest.BodyPublishers.noBody())
                 .uri(uri)
                 .build();
         HttpResponse<String> resp = hc.send(req, HttpResponse.BodyHandlers.ofString(UTF_8));

This ends up generating a request which has the following request headers:

INFO: HEADERS: REQUEST HEADERS:
  GET /no_body HTTP/1.1
    Content-Length: 0
    Host: 127.0.0.1:12345
    User-Agent: Java-http-client/26-internal