}

      val isUpgradeResponse =
        isUpgradeCode &&
          "upgrade".equals(response.header("Connection"), ignoreCase = true)

      response =
        when {
          // This is an HTTP/1 upgrade. (This case includes web socket upgrades.)
          isUpgradeRequest && isUpgradeResponse -> {
            response
              .newBuilder()
              .body(

  }

  @Test
  fun upgradeHttps() {
    enableTls(Protocol.HTTP_1_1)
    upgrade()
  }

  @Test
  fun upgradeRefusedByServer() {
    server.enqueue(MockResponse(body = "normal request"))
    val requestWithUpgrade =
      Request
        .Builder()
        .url(server.url("/"))
        .header("Connection", "upgrade")
        .build()
    client.newCall(requestWithUpgrade).execute().use { response ->

    - [Node Binaries](#node-binaries)
    - [Container Images](#container-images)
  - [Changelog since v1.33.0](#changelog-since-v1330)
  - [Urgent Upgrade Notes](#urgent-upgrade-notes)
    - [(No, really, you MUST read this before you upgrade)](#no-really-you-must-read-this-before-you-upgrade)
  - [Changes by Kind](#changes-by-kind)
    - [Deprecation](#deprecation)
    - [API Change](#api-change)
    - [Feature](#feature)

## Changelog since v1.28.0

## Urgent Upgrade Notes 

### (No, really, you MUST read this before you upgrade)

- kubeadm: `kubeadm upgrade node` now supports `addon` and `post-upgrade` phases. Users can use `kubeadm upgrade node phase addon` to execute the addon upgrade, or use `kubeadm upgrade node --skip-phases addon` to skip the addon upgrade. If you were previously skipping an addon subphase on `kubeadm init` you should now skip the same addon when calling `kubeadm upgrade apply` and `kubeadm upgrade node`. Currently, the `post-upgrade` phase is no-op, and it is mainly used to handle some release-specific...

- In kubeadm, in the new output API 'output.kubeadm.k8s.io/v1alpha3', the UpgradePlan structure that is used when calling 'kubeadm upgrade plan ... -o yaml|json' was modified to include a list of multiple available upgrades.
   ([#123461](https://github.com/kubernetes/kubernetes/pull/123461), [@carlory](https://github.com/carlory))
- Made decoding etcd's response respect the timeout context.

      }

    /**
     * Attempts to perform a web socket upgrade on the connection.
     * This will overwrite any previously set status, body, or streamHandler.
     */
    public fun webSocketUpgrade(listener: WebSocketListener): Builder =
      apply {
        status = "HTTP/1.1 101 Switching Protocols"
        setHeader("Connection", "Upgrade")
        setHeader("Upgrade", "websocket")
        webSocketListener = listener
      }

      ProtocolException::class.java,
      "Expected 'Upgrade' header value 'websocket' but was 'null'",
    )
    webSocket.cancel()
  }

  @Test
  @Throws(IOException::class)
  fun wrongUpgradeHeader() {
    webServer.enqueue(
      MockResponse
        .Builder()
        .code(101)
        .setHeader("Connection", "Upgrade")
        .setHeader("Upgrade", "Pepsi")

    `StrictMode` to detect if your `OkHttpClient` is being initialized on the main thread.

 *  Upgrade: [Okio 3.12.0][okio_3_12_0].

 *  Upgrade: [Kotlin 2.1.21][kotlin_2_1_21].

 *  Upgrade: [kotlinx.coroutines 1.10.2][coroutines_1_10_2]. This is used by the optional
    `okhttp-coroutines` artifact.

 *  Upgrade: [AndroidX Startup 1.2.0][startup_1_2_0]. The Android variant of the `okhttp` artifact

    private const val UPGRADE = "upgrade"

    /** See http://tools.ietf.org/html/draft-ietf-httpbis-http2-09#section-8.1.3. */
    private val HTTP_2_SKIPPED_REQUEST_HEADERS =
      immutableListOf(
        CONNECTION,
        HOST,
        KEEP_ALIVE,
        PROXY_CONNECTION,
        TE,
        TRANSFER_ENCODING,
        ENCODING,
        UPGRADE,
        TARGET_METHOD_UTF8,