diff --git a/jsaddle-warp.cabal b/jsaddle-warp.cabal
--- a/jsaddle-warp.cabal
+++ b/jsaddle-warp.cabal
@@ -1,5 +1,5 @@
 name: jsaddle-warp
-version: 0.9.0.0
+version: 0.9.1.0
 cabal-version: >=1.10
 build-type: Simple
 license: MIT
@@ -26,6 +26,7 @@
             Language.Javascript.JSaddle.WebSockets
         build-depends:
             aeson >=0.8.0.2 && <1.3,
+            bytestring >=0.10.6.0 && <0.11,
             containers >=0.5.6.2 && <0.6,
             http-types >=0.8.6 && <0.10,
             jsaddle >=0.9.0.0 && <0.10,
@@ -33,6 +34,8 @@
             text >=1.2.1.3 && <1.3,
             time >=1.5.0.1 && <1.8,
             transformers >=0.4.2.0 && <0.6,
+            uuid >=1.3.13 && <1.4,
+            uuid-types >=1.0.3 && <1.1,
             wai >=3.0.3.0 && <3.3,
             wai-websockets >=3.0.0.6 && <3.1,
             warp >=3.1.2 && <3.3,
diff --git a/src/Language/Javascript/JSaddle/Warp.hs b/src/Language/Javascript/JSaddle/Warp.hs
--- a/src/Language/Javascript/JSaddle/Warp.hs
+++ b/src/Language/Javascript/JSaddle/Warp.hs
@@ -17,8 +17,7 @@
   -- * Running JSM over WebSockets
     run
 #ifndef ghcjs_HOST_OS
-  , jsaddleOr
-  , jsaddleApp
+  , module Language.Javascript.JSaddle.WebSockets
 #endif
 ) where
 
@@ -29,7 +28,7 @@
 
 import Language.Javascript.JSaddle.Types (JSM)
 import Language.Javascript.JSaddle.Run (syncPoint)
-import Language.Javascript.JSaddle.WebSockets (jsaddleOr, jsaddleApp)
+import Language.Javascript.JSaddle.WebSockets
 #endif
 
 -- | Run the given 'JSM' action as the main entry point.  Either directly
@@ -40,6 +39,6 @@
 #else
 run :: Int -> JSM () -> IO ()
 run port f =
-    runSettings (setPort port (setTimeout 3600 defaultSettings)) $
+    runSettings (setPort port (setTimeout 3600 defaultSettings)) =<<
         jsaddleOr defaultConnectionOptions (f >> syncPoint) jsaddleApp
 #endif
diff --git a/src/Language/Javascript/JSaddle/WebSockets.hs b/src/Language/Javascript/JSaddle/WebSockets.hs
--- a/src/Language/Javascript/JSaddle/WebSockets.hs
+++ b/src/Language/Javascript/JSaddle/WebSockets.hs
@@ -16,6 +16,8 @@
   -- * Running JSM over WebSockets
     jsaddleOr
   , jsaddleApp
+  , jsaddleWithAppOr
+  , jsaddleAppPartial
 ) where
 
 import Control.Monad (forever)
@@ -25,7 +27,8 @@
 import Data.Monoid ((<>))
 import Data.Aeson (encode, decode)
 
-import Network.Wai (Application)
+import Network.Wai
+       (lazyRequestBody, Application, Request, Response, ResponseReceived)
 import Network.WebSockets
        (ConnectionOptions(..), sendTextData, receiveDataMessage,
         acceptRequest, ServerApp, sendPing)
@@ -34,55 +37,130 @@
 
 import Language.Javascript.JSaddle.Types (JSM(..))
 import qualified Network.Wai as W
-       (responseLBS, requestMethod, Application, pathInfo)
-import Data.Text (Text)
+       (responseLBS, requestMethod, pathInfo)
 import qualified Data.Text as T (pack)
 import qualified Network.HTTP.Types as H
-       (status403, status200, status405)
+       (status403, status200)
 import Language.Javascript.JSaddle.Run (runJavaScript)
-import Language.Javascript.JSaddle.Run.Files (indexHtml, jsaddleJs)
+import Language.Javascript.JSaddle.Run.Files (indexHtml, runBatch, ghcjsHelpers, initState)
+import Data.Maybe (fromMaybe)
+import qualified Data.Map as M (empty, insert, lookup)
+import Data.IORef (readIORef, newIORef, atomicModifyIORef')
+import Data.ByteString.Lazy (fromStrict, ByteString)
+import Data.Text (Text)
+import Data.UUID.Types (toText)
+import Data.UUID.V4 (nextRandom)
 
-jsaddleOr :: ConnectionOptions -> JSM () -> Application -> Application
-jsaddleOr opts entryPoint = websocketsOr opts wsApp
-  where
-    wsApp :: ServerApp
-    wsApp pending_conn = do
-        conn <- acceptRequest pending_conn
-        (processResult, _, start) <- runJavaScript (sendTextData conn . encode) entryPoint
-        _ <- forkIO . forever $
-            receiveDataMessage conn >>= \case
-                (WS.Text t) ->
-                    case decode t of
-                        Nothing -> error $ "jsaddle Results decode failed : " <> show t
-                        Just r  -> processResult r
-                _ -> error "jsaddle WebSocket unexpected binary data"
-        start
-        waitTillClosed conn
+jsaddleOr :: ConnectionOptions -> JSM () -> Application -> IO Application
+jsaddleOr opts entryPoint otherApp = do
+    syncHandlers <- newIORef M.empty
+    let wsApp :: ServerApp
+        wsApp pending_conn = do
+            conn <- acceptRequest pending_conn
+            (processResult, processSyncResult, start) <- runJavaScript (sendTextData conn . encode) entryPoint
+            _ <- forkIO . forever $
+                receiveDataMessage conn >>= \case
+                    (WS.Text t) ->
+                        case decode t of
+                            Nothing -> error $ "jsaddle Results decode failed : " <> show t
+                            Just r  -> processResult r
+                    _ -> error "jsaddle WebSocket unexpected binary data"
+            syncKey <- toText <$> nextRandom
+            atomicModifyIORef' syncHandlers (\m -> (M.insert syncKey processSyncResult m, ()))
+            sendTextData conn (encode syncKey)
+            start
+            waitTillClosed conn
 
-    -- Based on Network.WebSocket.forkPingThread
-    waitTillClosed conn = ignore `handle` go 1
-      where
-        go :: Int -> IO ()
-        go i = do
-            threadDelay (1 * 1000 * 1000)
-            sendPing conn (T.pack $ show i)
-            go (i + 1)
+        -- Based on Network.WebSocket.forkPingThread
+        waitTillClosed conn = ignore `handle` go 1
+          where
+            go :: Int -> IO ()
+            go i = do
+                threadDelay (1 * 1000 * 1000)
+                sendPing conn (T.pack $ show i)
+                go (i + 1)
 
-    ignore e = case fromException e of
-        Just async -> throwIO (async :: AsyncException)
-        Nothing    -> return ()
+        ignore e = case fromException e of
+            Just async -> throwIO (async :: AsyncException)
+            Nothing    -> return ()
 
+        syncHandler :: Application
+        syncHandler req sendResponse = case (W.requestMethod req, W.pathInfo req) of
+            ("POST", ["sync", syncKey]) -> do
+                body <- lazyRequestBody req
+                case decode body of
+                    Nothing -> error $ "jsaddle sync message decode failed : " <> show body
+                    Just result ->
+                        M.lookup syncKey <$> readIORef syncHandlers >>= \case
+                            Nothing -> error "jsaddle missing sync message handler"
+                            Just handler -> do
+                                next <- encode <$> handler result
+                                sendResponse $ W.responseLBS H.status200 [("Content-Type", "application/json")] next
+            _ -> otherApp req sendResponse
+    return $ websocketsOr opts wsApp syncHandler
+
+
 jsaddleApp :: Application
-jsaddleApp req = jsaddleAppPieces (W.pathInfo req) req
+jsaddleApp req sendResponse =
+    fromMaybe
+        (sendResponse $  W.responseLBS H.status403 [("Content-Type", "text/plain")] "Forbidden")
+        (jsaddleAppPartial req sendResponse)
 
-jsaddleAppPieces :: [Text] -> W.Application
-jsaddleAppPieces _ req sendResponse
-    | W.requestMethod req `notElem` ["GET", "HEAD"] = sendResponse $ W.responseLBS
-        H.status405
-        [("Content-Type", "text/plain")]
-        "Only GET or HEAD is supported"
-jsaddleAppPieces [] _req sendResponse = sendResponse $ W.responseLBS H.status200 [("Content-Type", "text/html")] indexHtml
-jsaddleAppPieces ["jsaddle.js"] _req sendResponse = sendResponse $ W.responseLBS H.status200 [("Content-Type", "application/javascript")] jsaddleJs
-jsaddleAppPieces _rawPieces _req sendResponse = sendResponse $ W.responseLBS H.status403
-            [ ("Content-Type", "text/plain")
-            ] "Forbidden"
+jsaddleWithAppOr :: ConnectionOptions -> JSM () -> Application -> IO Application
+jsaddleWithAppOr opts entryPoint otherApp = jsaddleOr opts entryPoint $ \req sendResponse ->
+  (fromMaybe (otherApp req sendResponse)
+     (jsaddleAppPartial req sendResponse))
+
+jsaddleAppPartial :: Request -> (Response -> IO ResponseReceived) -> Maybe (IO ResponseReceived)
+jsaddleAppPartial req sendResponse = case (W.requestMethod req, W.pathInfo req) of
+    ("GET", []) -> Just $ sendResponse $ W.responseLBS H.status200 [("Content-Type", "text/html")] indexHtml
+    ("GET", ["jsaddle.js"]) -> Just $ sendResponse $ W.responseLBS H.status200 [("Content-Type", "application/javascript")] jsaddleJs
+    _ -> Nothing
+
+-- Use this to generate this string for embedding
+-- sed -e 's|\\|\\\\|g' -e 's|^|    \\|' -e 's|$|\\n\\|' -e 's|"|\\"|g' data/jsaddle.js | pbcopy
+jsaddleJs :: ByteString
+jsaddleJs = "\
+    \if(typeof global !== \"undefined\") {\n\
+    \    global.window = global;\n\
+    \    global.WebSocket = require('ws');\n\
+    \}\n\
+    \\n\
+    \var connect = function() {\n\
+    \    var wsaddress = window.location.protocol.replace('http', 'ws')+\"//\"+window.location.hostname+(window.location.port?(\":\"+window.location.port):\"\");\n\
+    \\n\
+    \    var ws = new WebSocket(wsaddress);\n\
+    \    var syncKey = \"\";\n\
+    \\n\
+    \    ws.onopen = function(e) {\n\
+    \ " <> initState <> "\n\
+    \        var inXhrSend = false;\n\
+    \\n\
+    \        ws.onmessage = function(e) {\n\
+    \            if(inXhrSend) return;\n\
+    \            var batch = JSON.parse(e.data);\n\
+    \            if(typeof batch === \"string\") {\n\
+    \                syncKey = batch;\n\
+    \                return;\n\
+    \            }\n\
+    \\n\
+    \ " <> runBatch (\a -> "ws.send(JSON.stringify(" <> a <> "));")
+              (Just (\a -> "(function(){\n\
+                  \                       inXhrSend = true;\n\
+                  \                       var xhr = new XMLHttpRequest();\n\
+                  \                       xhr.open('POST', '/sync/'+syncKey, false);\n\
+                  \                       xhr.setRequestHeader(\"Content-type\", \"application/json\");\n\
+                  \                       xhr.send(JSON.stringify(" <> a <> "));\n\
+                  \                       inXhrSend = false;\n\
+                  \                       return JSON.parse(xhr.response);})()")) <> "\
+    \        };\n\
+    \    };\n\
+    \    ws.onerror = function() {\n\
+    \        setTimeout(connect, 1000);\n\
+    \    };\n\
+    \}\n\
+    \\n\
+    \ " <> ghcjsHelpers <> "\
+    \connect();\n\
+    \"
+