diff --git a/lua/kulala/cmd/init.lua b/lua/kulala/cmd/init.lua
index cc8b218..37d08e5 100644
--- a/lua/kulala/cmd/init.lua
+++ b/lua/kulala/cmd/init.lua
@@ -123,7 +123,12 @@ M.run_parser = function(req, callback)
           end
         end
         INT_PROCESSING.redirect_response_body_to_file(result.redirect_response_body_to_files)
-        PARSER.scripts.javascript.run("post_request", result.scripts.post_request)
+
+        local has_post_request_scripts = #result.scripts.post_request.inline > 0
+          or #result.scripts.pre_request.files > 0
+        if has_post_request_scripts then
+          PARSER.scripts.javascript.run("post_request", result.scripts.post_request)
+        end
         Api.trigger("after_request")
       end
       Fs.delete_request_scripts_files()
diff --git a/lua/kulala/globals/init.lua b/lua/kulala/globals/init.lua
index 377e9b0..528404d 100644
--- a/lua/kulala/globals/init.lua
+++ b/lua/kulala/globals/init.lua
@@ -4,7 +4,7 @@ local M = {}
 
 local plugin_tmp_dir = FS.get_plugin_tmp_dir()
 
-M.VERSION = "4.0.2"
+M.VERSION = "4.0.3"
 M.UI_ID = "kulala://ui"
 M.SCRATCHPAD_ID = "kulala://scratchpad"
 M.HEADERS_FILE = plugin_tmp_dir .. "/headers.txt"
diff --git a/lua/kulala/internal_processing/init.lua b/lua/kulala/internal_processing/init.lua
index d62bbe3..800b6de 100644
--- a/lua/kulala/internal_processing/init.lua
+++ b/lua/kulala/internal_processing/init.lua
@@ -18,18 +18,39 @@ local function get_nested_value(t, key)
   return value
 end
 
-local get_headers_as_table = function()
+---Function to get the last headers as a table
+---@description Reads the headers file and returns the headers as a table.
+---In some cases the headers file might contain multiple header sections,
+---e.g. if you have follow-redirections enabled.
+---This function will return the headers of the last response.
+---@return table
+local get_last_headers_as_table = function()
   local headers_file = FS.read_file(GLOBALS.HEADERS_FILE):gsub("\r\n", "\n")
   local lines = vim.split(headers_file, "\n")
   local headers_table = {}
+  -- INFO:
+  -- We only want the headers of the last response
+  -- so we reset the headers_table only each time the previous line was empty
+  -- and we also have new headers data
+  local previously_empty = false
   for _, header in ipairs(lines) do
-    if header:find(":") ~= nil then
-      local kv = vim.split(header, ":")
-      local key = kv[1]
-      -- the value should be everything after the first colon
-      -- but we can't use slice and join because the value might contain colons
-      local value = header:sub(#key + 2)
-      headers_table[key] = vim.trim(value)
+    local empty_line = header == ""
+    if empty_line then
+      previously_empty = true
+    else
+      if previously_empty then
+        headers_table = {}
+      end
+      previously_empty = false
+      if header:find(":") ~= nil then
+        local kv = vim.split(header, ":")
+        local key = kv[1]
+        -- INFO:
+        -- the value should be everything after the first colon
+        -- but we can't use slice and join because the value might contain colons
+        local value = header:sub(#key + 2)
+        headers_table[key] = vim.trim(value)
+      end
     end
   end
   return headers_table
@@ -78,7 +99,7 @@ local get_cookies_as_table = function()
 end
 
 local get_lower_headers_as_table = function()
-  local headers = get_headers_as_table()
+  local headers = get_last_headers_as_table()
   local headers_table = {}
   for key, value in pairs(headers) do
     headers_table[key:lower()] = value
@@ -101,7 +122,7 @@ end
 M.set_env_for_named_request = function(name, body)
   local named_request = {
     response = {
-      headers = get_headers_as_table(),
+      headers = get_last_headers_as_table(),
       body = body,
       cookies = get_cookies_as_table(),
     },
diff --git a/lua/kulala/parser/init.lua b/lua/kulala/parser/init.lua
index 08dfb37..c3b810f 100644
--- a/lua/kulala/parser/init.lua
+++ b/lua/kulala/parser/init.lua
@@ -11,7 +11,6 @@ local REQUEST_VARIABLES = require("kulala.parser.request_variables")
 local STRING_UTILS = require("kulala.utils.string")
 local PARSER_UTILS = require("kulala.parser.utils")
 local TS = require("kulala.parser.treesitter")
-local PLUGIN_TMP_DIR = FS.get_plugin_tmp_dir()
 local CURL_FORMAT_FILE = FS.get_plugin_path({ "parser", "curl-format.json" })
 local Logger = require("kulala.logger")
 
@@ -342,8 +341,8 @@ M.get_document = function()
         -- dynamic variables are defined as `{{$variable_name}}`
         local key, value = line:match("^([^:]+):%s*(.*)$")
         if key and value then
-          request.headers[key:lower()] = value
-          request.headers_raw[key:lower()] = value
+          request.headers[key] = value
+          request.headers_raw[key] = value
         end
       elseif is_request_line == true then
         -- Request line (e.g., GET http://example.com HTTP/1.1)
@@ -455,13 +454,9 @@ end
 ---@field file string -- The file path to write the response body to
 ---@field overwrite boolean -- Whether to overwrite the file if it already exists
 
----@class ScriptsItems
----@field inline table -- Inline post-request handler scripts - each element is a line of the script
----@field files table -- File post-request handler scripts - each element is a file path
----
 ---@class Scripts
----@field pre_request ScriptsItems -- Pre-request handler scripts
----@field post_request ScriptsItems -- Post-request handler scripts
+---@field pre_request ScriptData -- Pre-request handler scripts
+---@field post_request ScriptData -- Post-request handler scripts
 
 ---@class Request
 ---@field metadata table[] -- Metadata of the request
@@ -575,12 +570,12 @@ M.parse = function(start_request_linenr)
   res.url, res.headers, res.body =
     replace_variables_in_url_headers_body(res, document_variables, env, has_pre_request_scripts)
 
-  -- Merge headers from the $shared environment if it exists
+  -- Merge headers from the $shared environment if it does not exist in the request
+  -- this ensures that you can always override the headers in the request
   if DB.find_unique("http_client_env_shared") then
     local default_headers = DB.find_unique("http_client_env_shared")["$default_headers"]
     if default_headers then
       for key, value in pairs(default_headers) do
-        key = key:lower()
         if res.headers[key] == nil then
           res.headers[key] = value
         end
@@ -617,13 +612,15 @@ M.parse = function(start_request_linenr)
   table.insert(res.cmd, res.method)
 
   local is_graphql = PARSER_UTILS.contains_meta_tag(res, "graphql")
-    or PARSER_UTILS.contains_header(res.headers, "x-request-type", "GraphQL")
+    or PARSER_UTILS.contains_header(res.headers, "x-request-type", "graphql")
   if CONFIG.get().treesitter then
     -- treesitter parser handles graphql requests before this point
     is_graphql = false
   end
 
-  if res.headers["content-type"] ~= nil and res.body ~= nil then
+  local content_type_header_name, content_type_header_value = PARSER_UTILS.get_header(res.headers, "content-type")
+
+  if content_type_header_name and content_type_header_value and res.body ~= nil then
     -- check if we are a graphql query
     -- we need this here, because the user could have defined the content-type
     -- as application/json, but the body is a graphql query
@@ -633,9 +630,9 @@ M.parse = function(start_request_linenr)
       if gql_json then
         table.insert(res.cmd, "--data")
         table.insert(res.cmd, gql_json)
-        res.headers["content-type"] = "application/json"
+        res.headers[content_type_header_name] = "application/json"
       end
-    elseif res.headers["content-type"]:find("^multipart/form%-data") then
+    elseif content_type_header_value:find("^multipart/form%-data") then
       local tmp_file = FS.get_binary_temp_file(res.body)
       if tmp_file ~= nil then
         table.insert(res.cmd, "--data-binary")
@@ -654,31 +651,32 @@ M.parse = function(start_request_linenr)
       if gql_json then
         table.insert(res.cmd, "--data")
         table.insert(res.cmd, gql_json)
-        res.headers["content-type"] = "application/json"
+        res.headers[content_type_header_name] = "application/json"
       end
     end
   end
 
-  if res.headers["authorization"] then
-    local auth_header = res.headers["authorization"]
-    local authtype = auth_header:match("^(%w+)%s+.*")
+  local auth_header_name, auth_header_value = PARSER_UTILS.get_header(res.headers, "authorization")
+
+  if auth_header_name and auth_header_value then
+    local authtype = auth_header_value:match("^(%w+)%s+.*")
     if authtype == nil then
-      authtype = auth_header:match("^(%w+)%s*$")
+      authtype = auth_header_value:match("^(%w+)%s*$")
     end
 
     if authtype ~= nil then
       authtype = authtype:lower()
 
       if authtype == "ntlm" or authtype == "negotiate" or authtype == "digest" or authtype == "basic" then
-        local match, authuser, authpw = auth_header:match("^(%w+)%s+([^%s:]+)%s*[:%s]%s*([^%s]+)%s*$")
+        local match, authuser, authpw = auth_header_value:match("^(%w+)%s+([^%s:]+)%s*[:%s]%s*([^%s]+)%s*$")
         if match ~= nil or (authtype == "ntlm" or authtype == "negotiate") then
           table.insert(res.cmd, "--" .. authtype)
           table.insert(res.cmd, "-u")
           table.insert(res.cmd, (authuser or "") .. ":" .. (authpw or ""))
-          res.headers["authorization"] = nil
+          res.headers[auth_header_name] = nil
         end
       elseif authtype == "aws" then
-        local key, secret, optional = auth_header:match("^%w+%s([^%s]+)%s*([^%s]+)[%s$]+(.*)$")
+        local key, secret, optional = auth_header_value:match("^%w+%s([^%s]+)%s*([^%s]+)[%s$]+(.*)$")
         local token = optional:match("token:([^%s]+)")
         local region = optional:match("region:([^%s]+)")
         local service = optional:match("service:([^%s]+)")
@@ -697,7 +695,7 @@ M.parse = function(start_request_linenr)
           table.insert(res.cmd, "-H")
           table.insert(res.cmd, "x-amz-security-token:" .. token)
         end
-        res.headers["authorization"] = nil
+        res.headers[auth_header_name] = nil
       end
     end
   end
diff --git a/lua/kulala/parser/utils.lua b/lua/kulala/parser/utils.lua
index 374ab31..b974f70 100644
--- a/lua/kulala/parser/utils.lua
+++ b/lua/kulala/parser/utils.lua
@@ -1,21 +1,117 @@
 local M = {}
 
+-- PERF: we do a lot of if else blocks with repeating loops
+-- we could "optimize" this by using a single loop and if else blocks
+-- that would make the code more readable and easier to maintain
+-- but it would also make it slower
+
+---Check if a request has a specific meta tag
+---@param request table The request to check
+---@param tag string The meta tag to check for
 M.contains_meta_tag = function(request, tag)
+  tag = tag:lower()
   for _, meta in ipairs(request.metadata) do
-    if meta.name == tag then
+    if meta.name:lower() == tag then
       return true
     end
   end
   return false
 end
 
+---Check if a header is present in the request
+---@param headers table The headers to check
+---@param header string The header name to check
+---@param value string|nil The value to check for or nil if only the header name should be checked
+---@return boolean
 M.contains_header = function(headers, header, value)
-  for k, v in pairs(headers) do
-    if k == header and v == value then
-      return true
+  header = header:lower()
+  value = value and value:lower() or nil
+  vim.print("header: " .. header .. " value: " .. value)
+  if value == nil then
+    for k, _ in pairs(headers) do
+      if k:lower() == header then
+        return true
+      end
+    end
+  else
+    for k, v in pairs(headers) do
+      if k:lower() == header and v:lower() == value then
+        return true
+      end
     end
   end
   return false
 end
 
+---Get the value of a header from the request
+---@param headers table The headers to check
+---@param header string The header name to check
+---@param dont_ignore_case boolean|nil If true, the header name will be case sensitive
+---@return string|nil
+M.get_header_value = function(headers, header, dont_ignore_case)
+  header = dont_ignore_case and header or header:lower()
+  for k, v in pairs(headers) do
+    if k == header then
+      return v
+    end
+  end
+  return nil
+end
+
+---Get the name of a header from the request
+---@param headers table The headers to check
+---@param header string The header name to check
+---@param dont_ignore_case boolean|nil If true, the header name will be case sensitive
+---@return string|nil
+M.get_header_name = function(headers, header, dont_ignore_case)
+  header = dont_ignore_case and header or header:lower()
+  for k, _ in pairs(headers) do
+    if k:lower() == header then
+      return k
+    end
+  end
+  return nil
+end
+
+---Get a header from the request
+---@param headers table The headers to check
+---@param header string The header name to check
+---@param value string|nil The value to check for or nil if only the header name should be checked
+---@param dont_ignore_case boolean|nil If true, the header name will be case sensitive
+---@return (string|nil), (string|nil) The header name and value or nil if not found
+M.get_header = function(headers, header, value, dont_ignore_case)
+  header = dont_ignore_case and header or header:lower()
+  value = value and (dont_ignore_case and value or value:lower()) or nil
+  if dont_ignore_case then
+    if value == nil then
+      for k, _ in pairs(headers) do
+        if k == header then
+          return k, headers[k]
+        end
+      end
+    else
+      for k, v in pairs(headers) do
+        if k == header and v == value then
+          return k, v
+        end
+      end
+    end
+  else
+    if value == nil then
+      for k, _ in pairs(headers) do
+        if k:lower() == header then
+          return k, headers[k]
+        end
+      end
+    else
+      for k, v in pairs(headers) do
+        if k:lower() == header and v:lower() == value then
+          return k, v
+        end
+      end
+    end
+  end
+  return nil, nil
+end
+
 return M