diff --git a/lib/core/util.js b/lib/core/util.js
index dfefac6d15c..65150910993 100644
--- a/lib/core/util.js
+++ b/lib/core/util.js
@@ -436,6 +436,46 @@ function parseHeaders (headers, obj) {
   return obj
 }
 
+function normalizeHeaders (headers) {
+  const ret = {}
+  if (headers == null) {
+    // Do nothing...
+  } else if (Array.isArray(headers)) {
+    for (let i = 0; i < headers.length; i += 2) {
+      if (Array.isArray(headers[i]) && headers[i].length === 2) {
+        const key = headerNameToString(headers[i][0])
+        const val = ret[key]
+        if (val == null) {
+          ret[key] = String(headers[i][1])
+        } else if (typeof val === 'string') {
+          ret[key] = [val, String(headers[i][1])]
+        } else {
+          val.push(String(headers[i][1]))
+        }
+      } else {
+        const key = headerNameToString(headers[i])
+        const val = ret[key]
+        if (val == null) {
+          ret[key] = String(headers[i][1])
+        } else if (typeof val === 'string') {
+          ret[key] = [val, String(headers[i + 1])]
+        } else {
+          val.push(String(headers[i + 1]))
+        }
+      }
+    }
+  } else if (typeof headers[Symbol.iterator] === 'function') {
+    for (const [key, val] of headers) {
+      ret[headerNameToString(key)] = String(val)
+    }
+  } else {
+    for (const [key, val] of Object.entries(headers)) {
+      ret[headerNameToString(key)] = String(val)
+    }
+  }
+  return ret
+}
+
 /**
  * @param {Buffer[]} headers
  * @returns {string[]}
@@ -903,5 +943,6 @@ module.exports = {
   nodeMajor,
   nodeMinor,
   safeHTTPMethods: Object.freeze(['GET', 'HEAD', 'OPTIONS', 'TRACE']),
-  wrapRequestBody
+  wrapRequestBody,
+  normalizeHeaders
 }
diff --git a/lib/handler/cache-handler.js b/lib/handler/cache-handler.js
index 7c3a7da0bb6..de918ef51ac 100644
--- a/lib/handler/cache-handler.js
+++ b/lib/handler/cache-handler.js
@@ -38,9 +38,7 @@ class CacheHandler {
    * @param {import('../../types/cache-interceptor.d.ts').default.CacheKey} cacheKey
    * @param {import('../../types/dispatcher.d.ts').default.DispatchHandler} handler
    */
-  constructor (opts, cacheKey, handler) {
-    const { store } = opts
-
+  constructor ({ store }, cacheKey, handler) {
     this.#store = store
     this.#cacheKey = cacheKey
     this.#handler = handler
diff --git a/lib/handler/decorator-handler.js b/lib/handler/decorator-handler.js
index b0966c2eca9..8a0d6c588a7 100644
--- a/lib/handler/decorator-handler.js
+++ b/lib/handler/decorator-handler.js
@@ -2,6 +2,9 @@
 
 const assert = require('node:assert')
 
+/**
+ * @deprecated
+ */
 module.exports = class DecoratorHandler {
   #handler
   #onCompleteCalled = false
diff --git a/lib/handler/redirect-handler.js b/lib/handler/redirect-handler.js
index df2baee19d5..c8c9d60663c 100644
--- a/lib/handler/redirect-handler.js
+++ b/lib/handler/redirect-handler.js
@@ -42,7 +42,6 @@ class RedirectHandler {
 
     this.dispatch = dispatch
     this.location = null
-    this.abort = null
     this.opts = { ...opts, maxRedirections: 0 } // opts must be a copy
     this.maxRedirections = maxRedirections
     this.handler = handler
@@ -83,20 +82,16 @@ class RedirectHandler {
     }
   }
 
-  onConnect (abort) {
-    this.abort = abort
-    this.handler.onConnect(abort, { history: this.history })
-  }
-
-  onUpgrade (statusCode, headers, socket) {
-    this.handler.onUpgrade(statusCode, headers, socket)
+  onRequestStart (controller, context) {
+    this.location = null
+    this.handler.onRequestStart?.(controller, { ...context, history: this.history })
   }
 
-  onError (error) {
-    this.handler.onError(error)
+  onRequestUpgrade (controller, statusCode, headers, socket) {
+    this.handler.onRequestUpgrade?.(controller, statusCode, headers, socket)
   }
 
-  onHeaders (statusCode, rawHeaders, resume, statusText) {
+  onResponseStart (controller, statusCode, statusMessage, headers) {
     if (this.opts.throwOnMaxRedirect && this.history.length >= this.maxRedirections) {
       throw new Error('max redirects')
     }
@@ -122,16 +117,17 @@ class RedirectHandler {
       this.opts.body = null
     }
 
-    this.location = this.history.length >= this.maxRedirections || util.isDisturbed(this.opts.body)
+    this.location = this.history.length >= this.maxRedirections || util.isDisturbed(this.opts.body) || redirectableStatusCodes.indexOf(statusCode) === -1
       ? null
-      : parseLocation(statusCode, rawHeaders)
+      : headers.location
 
     if (this.opts.origin) {
       this.history.push(new URL(this.opts.path, this.opts.origin))
     }
 
     if (!this.location) {
-      return this.handler.onHeaders(statusCode, rawHeaders, resume, statusText)
+      this.handler.onResponseStart?.(controller, statusCode, statusMessage, headers)
+      return
     }
 
     const { origin, pathname, search } = util.parseURL(new URL(this.location, this.opts.origin && new URL(this.opts.path, this.opts.origin)))
@@ -140,14 +136,16 @@ class RedirectHandler {
     // Remove headers referring to the original URL.
     // By default it is Host only, unless it's a 303 (see below), which removes also all Content-* headers.
     // https://tools.ietf.org/html/rfc7231#section-6.4
-    this.opts.headers = cleanRequestHeaders(this.opts.headers, statusCode === 303, this.opts.origin !== origin)
+    this.opts.headers = this.opts.headers
+      ? cleanRequestHeaders(this.opts.headers, statusCode === 303, this.opts.origin !== origin)
+      : this.opts.headers
     this.opts.path = path
     this.opts.origin = origin
     this.opts.maxRedirections = 0
     this.opts.query = null
   }
 
-  onData (chunk) {
+  onResponseData (controller, chunk) {
     if (this.location) {
       /*
         https://tools.ietf.org/html/rfc7231#section-6.4
@@ -167,11 +165,11 @@ class RedirectHandler {
         servers and browsers implementors, we ignore the body as there is no specified way to eventually parse it.
       */
     } else {
-      return this.handler.onData(chunk)
+      this.handler.onResponseData?.(controller, chunk)
     }
   }
 
-  onComplete (trailers) {
+  onResponseEnd (controller, trailers) {
     if (this.location) {
       /*
         https://tools.ietf.org/html/rfc7231#section-6.4
@@ -181,45 +179,26 @@ class RedirectHandler {
 
         See comment on onData method above for more detailed information.
       */
-
-      this.location = null
-      this.abort = null
-
       this.dispatch(this.opts, this)
     } else {
-      this.handler.onComplete(trailers)
+      this.handler.onResponseEnd(controller, trailers)
     }
   }
 
-  onBodySent (chunk) {
-    if (this.handler.onBodySent) {
-      this.handler.onBodySent(chunk)
-    }
-  }
-}
-
-function parseLocation (statusCode, rawHeaders) {
-  if (redirectableStatusCodes.indexOf(statusCode) === -1) {
-    return null
-  }
-
-  for (let i = 0; i < rawHeaders.length; i += 2) {
-    if (rawHeaders[i].length === 8 && util.headerNameToString(rawHeaders[i]) === 'location') {
-      return rawHeaders[i + 1]
-    }
+  onResponseError (controller, error) {
+    this.handler.onResponseError?.(controller, error)
   }
 }
 
 // https://tools.ietf.org/html/rfc7231#section-6.4.4
-function shouldRemoveHeader (header, removeContent, unknownOrigin) {
-  if (header.length === 4) {
-    return util.headerNameToString(header) === 'host'
+function shouldRemoveHeader (name, removeContent, unknownOrigin) {
+  if (name.length === 4) {
+    return name === 'host'
   }
-  if (removeContent && util.headerNameToString(header).startsWith('content-')) {
+  if (removeContent && name.startsWith('content-')) {
     return true
   }
-  if (unknownOrigin && (header.length === 13 || header.length === 6 || header.length === 19)) {
-    const name = util.headerNameToString(header)
+  if (unknownOrigin && (name.length === 13 || name.length === 6 || name.length === 19)) {
     return name === 'authorization' || name === 'cookie' || name === 'proxy-authorization'
   }
   return false
@@ -227,22 +206,11 @@ function shouldRemoveHeader (header, removeContent, unknownOrigin) {
 
 // https://tools.ietf.org/html/rfc7231#section-6.4
 function cleanRequestHeaders (headers, removeContent, unknownOrigin) {
-  const ret = []
-  if (Array.isArray(headers)) {
-    for (let i = 0; i < headers.length; i += 2) {
-      if (!shouldRemoveHeader(headers[i], removeContent, unknownOrigin)) {
-        ret.push(headers[i], headers[i + 1])
-      }
-    }
-  } else if (headers && typeof headers === 'object') {
-    const entries = typeof headers[Symbol.iterator] === 'function' ? headers : Object.entries(headers)
-    for (const [key, value] of entries) {
-      if (!shouldRemoveHeader(key, removeContent, unknownOrigin)) {
-        ret.push(key, value)
-      }
+  const ret = util.normalizeHeaders(headers)
+  for (const name of Object.keys(ret)) {
+    if (shouldRemoveHeader(name, removeContent, unknownOrigin)) {
+      delete ret[name]
     }
-  } else {
-    assert(headers == null, 'headers must be an object or an array')
   }
   return ret
 }
diff --git a/lib/handler/unwrap-handler.js b/lib/handler/unwrap-handler.js
index 3b38ac264d0..a6b44d99876 100644
--- a/lib/handler/unwrap-handler.js
+++ b/lib/handler/unwrap-handler.js
@@ -87,7 +87,7 @@ module.exports = class UnwrapHandler {
   }
 
   onError (err) {
-    if (!this.#handler.onError) {
+    if (!this.#handler.onResponseError) {
       throw new InvalidArgumentError('invalid onError method')
     }