eclipse-vertx/vert.x · error · IllegalArgumentException

Default HTTP client version ${protocolVersion} does not belo

Error message

Default HTTP client version ${protocolVersion} does not belong to the ALPN protocol version list ${versions}

What it means

Consistency check while converting HttpClientOptions into HttpClientConfig: the configured default protocol version is not present in the ALPN application protocol list derived from the enabled SSL/ALPN versions. The message reports both the default version and the ALPN list; the mismatched configuration input is options.protocolVersion versus the ALPN-enabled versions.

Source

Thrown at vertx-core/src/main/java/io/vertx/core/http/HttpClientConfig.java:155

    redirectConfig.setMaxBufferedSize(options.getMaxRedirectBufferedSize());
    if (options.getCrossOriginRedirectBlockedHeaders() != null) {
      redirectConfig.setCrossOriginBlockedHeaders(options.getCrossOriginRedirectBlockedHeaders());
    }
    if (options.getSameOriginRedirectBlockedHeaders() != null) {
      redirectConfig.setSameOriginBlockedHeaders(options.getSameOriginRedirectBlockedHeaders());
    }

    List<HttpVersion> versions;
    ClientSSLOptions sslOptions = options.getSslOptions();
    if (sslOptions == null || !sslOptions.isUseAlpn() || sslOptions.getApplicationLayerProtocols().isEmpty()) {
      versions = new ArrayList<>(toSupportedVersion(options.getProtocolVersion()));
    } else {
      versions = sslOptions.getApplicationLayerProtocols()
        .stream()
        .map(HttpVersion::fromAlpnName)
        .collect(Collectors.toList());
      if (!versions.contains(options.getProtocolVersion())) {
        throw new IllegalArgumentException("Default HTTP client version " + options.getProtocolVersion() +
          " does not belong to the ALPN protocol version list " + versions);
      }
    }

    this.tcpConfig = new TcpClientConfig(options);
    this.quicConfig = defaultQuicConfig();
    this.ssl = options.isSsl();
    this.versions = versions;
    this.http1Config = options.getHttp1Config();
    this.http2Config = options.getHttp2Config();
    this.http3Config = new Http3ClientConfig();
    this.verifyHost = options.isVerifyHost();
    this.decompressionEnabled = options.isDecompressionSupported();
    this.defaultHost = options.getDefaultHost();
    this.defaultPort = options.getDefaultPort();
    this.redirectConfig = redirectConfig;
    this.observabilityConfig = observabilityConfig;
    this.shared = options.isShared();

View on GitHub (pinned to fb308bd8c3)

Solutions

1. Enable ALPN versions that include the configured default protocol version
2. Or set a default protocolVersion consistent with the ALPN list
3. Disable ALPN if it is not needed

When it happens

Trigger: Thrown at vertx-core/src/main/java/io/vertx/core/http/HttpClientConfig.java:155 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of eclipse-vertx/vert.x@fb308bd8c3 (2026-09-06). Data as JSON: /api/errors/0f682b629e2be54f. Report an issue: GitHub.