diff --git a/Nemesis b/Nemesis
--- a/Nemesis
+++ b/Nemesis
@@ -28,3 +28,8 @@
   desc "run hello2"
   task "hello2" - do
     sh "src/Hello2"
+  
+  
+  desc "bench"
+  task "bench" - do
+    sh "ab -n 10000 -c 100 http://0.0.0.0:3001/"
diff --git a/chu2.cabal b/chu2.cabal
--- a/chu2.cabal
+++ b/chu2.cabal
@@ -1,5 +1,5 @@
 Name:                 chu2
-Version:              2012.11.18.2
+Version:              2012.11.19
 Build-type:           Simple
 Synopsis:             FFI for Chu2 Agda Web Server Interface
 Description:
@@ -32,6 +32,7 @@
     , hack2
     , hack2-handler-snap-server
     , data-default
+    , utf8-string
     
   hs-source-dirs: src/
   exposed-modules:  
diff --git a/readme.md b/readme.md
--- a/readme.md
+++ b/readme.md
@@ -6,19 +6,18 @@
 ```agda
 module Hello where
 
-open import IO.Primitive    using (return)
+open import IO              using (run; return)
 open import Data.List       using ([])
-open import Chu2.ByteString using (pack)
-open import Function        using (_$_; const)
+open import Function        using (const)
 open import Chu2            using (response; OK; Application) 
 
-hello-world-response = response OK [] (pack "Hello Agda!")
+hello-world-response = response OK [] ("Hello Agda!")
 
 hello-world-app : Application
-hello-world-app = const $ return hello-world-response
+hello-world-app = const (return hello-world-response)
 
 open import Chu2.Handler.SnapServer using (on-port_run)
-main = on-port 3000 run hello-world-app
+main = run (on-port 3000 run hello-world-app)
 ```
 
 ## Using Middleware
@@ -29,7 +28,7 @@
 -- simple-logger middleware
 open import Chu2.Middleware.SimpleLogger using (simple-logger)
 
-open import IO.Primitive    using (return)
+open import IO              using (run; return)
 open import Function        using (const)
 open import Chu2            using (Application; defaultResponse; RawMiddleware)
 
@@ -40,7 +39,7 @@
 hello-world-app = const - return defaultResponse
 
 open import Chu2.Handler.SnapServer using (on-port_run)
-main = on-port 3001 run - simple-logger hello-world-app
+main = run - on-port 3001 run - simple-logger hello-world-app
 ```
 
 ## Note
diff --git a/src/Chu2.agda b/src/Chu2.agda
--- a/src/Chu2.agda
+++ b/src/Chu2.agda
@@ -2,18 +2,20 @@
 
 open import Data.List using (List; [_])
 open import Foreign.Haskell using (Unit)
-open import IO.Primitive using (IO)
+open import IO using (IO; run; lift; _>>=_; return; _>>_)
+open import Data.Unit using (⊤)
+import IO.Primitive as Prim
 open import Data.String using (String)
+open import Coinduction using (♯_)
 
 data Tuple (A : Set)(B : Set) : Set where
     _,_ : A → B → Tuple A B
 
-
 {-# IMPORT Chu2.FFI #-}
 {-# COMPILED_DATA Tuple (,) (,) #-}
 
-Header = Tuple String String
-
+Field = String
+Header = Tuple Field Field
 Headers = List Header
 
 data RequestMethod : Set where
@@ -46,14 +48,13 @@
     Chu2.FFI.HTTPS
 #-}
 
-ScriptName    =  String
-PathInfo      =  String
-QueryString   =  String
-ServerName    =  String
-ServerPort    =  String
+ScriptName    =  Field
+PathInfo      =  Field
+QueryField    =  Field
+ServerName    =  Field
+ServerPort    =  Field
 HttpHeaders   =  Headers
-Chu2Input     =  String
-Chu2Errors    =  String → IO Unit
+Chu2Input     =  Field
 Chu2Headers   =  Headers
 
 private
@@ -62,13 +63,12 @@
         RequestMethod  
       → ScriptName     
       → PathInfo       
-      → QueryString    
+      → QueryField    
       → ServerName     
       → ServerPort     
       → HttpHeaders    
       → Chu2UrlScheme  
       → Chu2Input      
-      → Chu2Errors     
       → Chu2Headers   
       → EnvData
 
@@ -80,13 +80,12 @@
     requestMethod  : RequestMethod  
     scriptName     : ScriptName     
     pathInfo       : PathInfo       
-    queryString    : QueryString    
+    queryField     : QueryField    
     serverName     : ServerName     
     serverPort     : ServerPort     
     httpHeaders    : HttpHeaders    
     chu2UrlScheme  : Chu2UrlScheme  
     chu2Input      : Chu2Input      
-    chu2Errors     : Chu2Errors     
     chu2Headers    : Chu2Headers   
     
 
@@ -97,13 +96,12 @@
         requestMethod  
         scriptName     
         pathInfo       
-        queryString    
+        queryField    
         serverName     
         serverPort     
         httpHeaders    
         chu2UrlScheme  
         chu2Input      
-        chu2Errors     
         chu2Headers    
     ) =
   
@@ -111,43 +109,39 @@
       requestMethod  
       scriptName     
       pathInfo       
-      queryString    
+      queryField    
       serverName     
       serverPort     
       httpHeaders    
       chu2UrlScheme  
       chu2Input      
-      chu2Errors     
       chu2Headers    
 
-
+  
   envToEnvData : Env → EnvData
   envToEnvData
     ( env
         requestMethod  
         scriptName     
         pathInfo       
-        queryString    
+        queryField    
         serverName     
         serverPort     
         httpHeaders    
         chu2UrlScheme  
         chu2Input      
-        chu2Errors     
         chu2Headers    
     ) =
-  
     envData
       requestMethod  
       scriptName     
       pathInfo       
-      queryString    
+      queryField    
       serverName     
       serverPort     
       httpHeaders    
       chu2UrlScheme  
       chu2Input      
-      chu2Errors     
       chu2Headers  
 
 data Status : Set where
@@ -201,7 +195,7 @@
   Chu2.FFI.ServiceUnavailable
 #-}
 
-Body = String
+Body = Field
 
 private
   data ResponseData : Set where
@@ -254,7 +248,7 @@
   record
     {
       status = OK
-    ; headers = [("Content-Type", "text/plain")]
+    ; headers = [("Content-Type", "text/plain; charset=utf-8")]
     ; body = "Chu2!"
     }
 
@@ -262,29 +256,36 @@
 Middleware = Application → Application
 
 private
-  RawApplication = EnvData → IO ResponseData
+  RawApplication = EnvData → Prim.IO ResponseData
 
 RawMiddleware = RawApplication → RawApplication
 
 private
-  open IO.Primitive using (_>>=_; return)
+  open import Function using (_$_)
+ 
   applicationToRawApplication : Application → RawApplication
   applicationToRawApplication app = 
-    λ aEnvData → app (envDataToEnv aEnvData) >>= λ aResponse → return (responseToResponseData aResponse)
+    λ aEnvData → run $
+      ♯ app (envDataToEnv aEnvData) >>= λ aResponse →
+      ♯ return (responseToResponseData aResponse)
 
   rawApplicationToApplication : RawApplication → Application
   rawApplicationToApplication rawApp = 
-    λ aEnv → rawApp (envToEnvData aEnv) >>= λ aRawResponse → return (responseDataToResponse aRawResponse)
+    λ aEnv → ♯ lift (rawApp (envToEnvData aEnv)) >>= λ aRawResponse → 
+             ♯ return (responseDataToResponse aRawResponse)
 
 
-Handler = Application → IO Unit
-RawHandler = RawApplication → IO Unit
+Handler = Application → IO ⊤
+RawHandler = RawApplication → Prim.IO Unit
 
 open import Function using (_∘_; _$_; id)
 
 
 rawHandlerToHandler : RawHandler → Handler
-rawHandlerToHandler h = h ∘ applicationToRawApplication
+rawHandlerToHandler rawHandler app = 
+  ♯ lift (rawHandler (applicationToRawApplication app)) >> 
+  ♯ return _
+    
 
 
 
diff --git a/src/Chu2/FFI.hs b/src/Chu2/FFI.hs
--- a/src/Chu2/FFI.hs
+++ b/src/Chu2/FFI.hs
@@ -63,7 +63,6 @@
   ,  httpHeaders    :: Headers
   ,  chu2UrlScheme  :: Chu2UrlScheme
   ,  chu2Input      :: Field
-  ,  chu2Errors     :: Chu2Errors
   ,  chu2Headers    :: Headers
   }
 
diff --git a/src/Chu2/Interface/Hack2.hs b/src/Chu2/Interface/Hack2.hs
--- a/src/Chu2/Interface/Hack2.hs
+++ b/src/Chu2/Interface/Hack2.hs
@@ -37,13 +37,7 @@
 chu2UrlSchemeToHack2UrlScheme HTTP  = Hack2.HTTP
 chu2UrlSchemeToHack2UrlScheme HTTPS = Hack2.HTTPS
 
-hack2ErrorsToChu2Errors :: Hack2.HackErrors -> Chu2Errors
-hack2ErrorsToChu2Errors io x = Hack2.unHackErrors io (f2b_Utf8Encoding x)
 
-chu2ErrorsToHack2Errors :: Chu2Errors -> Hack2.HackErrors
-chu2ErrorsToHack2Errors io = Hack2.HackErrors (\x -> io (b2f_Utf8Encoding x))
-
-
 f2b :: Field -> ByteString
 f2b = pack
   
@@ -65,7 +59,6 @@
     {
       requestMethod   = hack2RequestMethodToChu2RequestMethod   $ Hack2.requestMethod  e
     , chu2UrlScheme   = hack2UrlSchemeToChu2UrlScheme           $ Hack2.hackUrlScheme  e
-    , chu2Errors      = hack2ErrorsToChu2Errors                 $ Hack2.hackErrors     e
     , serverPort      = show                                    $ Hack2.serverPort     e
     , scriptName      = b2f                                     $ Hack2.scriptName     e
     , pathInfo        = b2f                                     $ Hack2.pathInfo       e
@@ -82,7 +75,6 @@
     {
       Hack2.requestMethod   = chu2RequestMethodToHack2RequestMethod   $  requestMethod  e
     , Hack2.hackUrlScheme   = chu2UrlSchemeToHack2UrlScheme           $  chu2UrlScheme  e
-    , Hack2.hackErrors      = chu2ErrorsToHack2Errors                 $  chu2Errors     e
     , Hack2.serverPort      = read                                    $  serverPort     e
     , Hack2.scriptName      = f2b                                     $  scriptName     e
     , Hack2.pathInfo        = f2b                                     $  pathInfo       e
diff --git a/src/Hello.agda b/src/Hello.agda
--- a/src/Hello.agda
+++ b/src/Hello.agda
@@ -1,14 +1,14 @@
 module Hello where
 
-open import IO.Primitive    using (return)
+open import IO              using (run; return)
 open import Data.List       using ([])
-open import Function        using (_$_; const)
+open import Function        using (const)
 open import Chu2            using (response; OK; Application) 
 
 hello-world-response = response OK [] ("Hello Agda!")
 
 hello-world-app : Application
-hello-world-app = const $ return hello-world-response
+hello-world-app = const (return hello-world-response)
 
 open import Chu2.Handler.SnapServer using (on-port_run)
-main = on-port 3000 run hello-world-app
+main = run (on-port 3000 run hello-world-app)
diff --git a/src/Hello2.agda b/src/Hello2.agda
--- a/src/Hello2.agda
+++ b/src/Hello2.agda
@@ -3,7 +3,7 @@
 -- simple-logger middleware
 open import Chu2.Middleware.SimpleLogger using (simple-logger)
 
-open import IO.Primitive    using (return)
+open import IO              using (run; return)
 open import Function        using (const)
 open import Chu2            using (Application; defaultResponse; RawMiddleware)
 
@@ -14,4 +14,4 @@
 hello-world-app = const - return defaultResponse
 
 open import Chu2.Handler.SnapServer using (on-port_run)
-main = on-port 3001 run - simple-logger hello-world-app
+main = run - on-port 3001 run - simple-logger hello-world-app