diff --git a/examples/threaditjs/app.js b/examples/threaditjs/app.js
index 05085fe6..48384c99 100644
--- a/examples/threaditjs/app.js
+++ b/examples/threaditjs/app.js
@@ -1,11 +1,15 @@
 T.time("Setup");
 
-var request = require("../../request/request")(window, Promise).ajax
+var Stream = require("../../util/stream")
+var requestService = require("../../request/request")(window, Stream)
+var request = requestService.xhr
 var m = require("../../render/hyperscript")
 var trust = require("../../render/trust")
 var renderer = require("../../render/render")(window)
 var router = require("../../router/router")(window)
 
+requestService.setCompletionCallback(run)
+
 //API calls
 var api = {
 	home : function() {
@@ -14,7 +18,7 @@ var api = {
 	}, 
 	thread : function(id) {
 		T.timeEnd("Setup")
-		return request({method: "GET", url: T.apiUrl + "/comments/" + id}).then(T.transformResponse)
+		return request({method: "GET", url: T.apiUrl + "/comments/" + id}).map(T.transformResponse)
 	},
 	newThread : function(text) {
 		return request({method: "POST", url: T.apiUrl + "/threads/create",data: {text: text}})
@@ -27,29 +31,27 @@ var api = {
 var threads = [], current = null, loaded = false, error = false, notFound = false
 function loadThreads() {
 	loaded = false
-	api.home().then(function(response) {
+	api.home().map(function(response) {
 		document.title = "ThreaditJS: Mithril | Home"
 		threads = response.data
 		loaded = true
-	}, function() {
+	}).catch(function() {
 		loaded = error = true
 	})
-	.then(run)
 }
 
 function loadThread(id) {
 	loaded = false
 	notFound = false
-	api.thread(id).then(function(response) {
+	api.thread(id).map(function(response) {
 		document.title = "ThreaditJS: Mithril | " + T.trimTitle(response.root.text);
 		loaded = true
 		current = response
-	}, function(response) {
+	}).catch(function(response) {
 		loaded = true
 		if (response.status === 404) notFound = true
 		else error = true
 	})
-	.then(run)
 }
 function unloadThread() {
 	current = null
@@ -57,11 +59,10 @@ function unloadThread() {
 
 function createThread() {
 	var threadText = document.getElementById("threadText")
-	api.newThread(threadText.value).then(function(response) {
+	api.newThread(threadText.value).map(function(response) {
 		threadText.value = "";
 		threads.push(response.data);
 	})
-	.then(run)
 	return false
 }
 
@@ -72,12 +73,11 @@ function showReplying(vnode) {
 }
 
 function submitComment(vnode) {
-	api.newComment(vnode.state.newComment, vnode.attrs.node.id).then(function(response) {
+	api.newComment(vnode.state.newComment, vnode.attrs.node.id).map(function(response) {
 		vnode.state.newComment = ""
 		vnode.state.replying = false
 		vnode.attrs.node.children.push(response.data)
 	})
-	.then(run)
 	return false
 }
 
diff --git a/examples/threaditjs/index.html b/examples/threaditjs/index.html
index b59ffea7..53249dfa 100644
--- a/examples/threaditjs/index.html
+++ b/examples/threaditjs/index.html
@@ -18,6 +18,7 @@
 		<script src="../../querystring/build.js"></script>
 		<script src="../../querystring/parse.js"></script>
 		<script src="../../router/router.js"></script>
+		<script src="../../util/stream.js"></script>
 		<script src="../../request/request.js"></script>
 		<script src="app.js"></script>
 	</body>
diff --git a/index.js b/index.js
index 432194ea..593f266f 100644
--- a/index.js
+++ b/index.js
@@ -1,21 +1,30 @@
 "use strict"
+
 ;(function () {
-	var Promise = require("./promise/promise")
-	var m = require("./render/hyperscript")
-	var renderService = require("./render/render")(window)
-	var redrawService = require("./api/pubsub")()
-	var requestService = require("./request/request")(window, Promise)
 
-	m.request = requestService.xhr
-	m.jsonp = requestService.jsonp
-	m.route = require("./api/router")(window, renderService, redrawService)
-	m.mount = require("./api/mount")(renderService, redrawService)
-	m.trust = require("./render/trust")
-	m.prop = require("./util/prop")
-	m.withAttr = require("./util/withAttr")
-	m.render = renderService.render
-	m.redraw = redrawService.publish
+var Stream = require("./util/stream")
+var m = require("./render/hyperscript")
+var renderService = require("./render/render")(window)
+var redrawService = require("./api/pubsub")()
+var requestService = require("./request/request")(window)
+
+requestService.setCompletionCallback(redrawService.publish)
+
+m.version = "bleeding-edge"
+m.request = requestService.xhr
+m.jsonp = requestService.jsonp
+m.route = require("./api/router")(window, renderService, redrawService)
+m.mount = require("./api/mount")(renderService, redrawService)
+m.trust = require("./render/trust")
+m.prop = Stream.stream
+m.prop.combine = Stream.combine
+m.prop.reject = Stream.reject
+m.prop.HALT = Stream.HALT
+m.withAttr = require("./util/withAttr")
+m.render = renderService.render
+m.redraw = redrawService.publish
+
+if (typeof module === "object") module.exports = m
+else window.m = m
 
-	if (typeof module === "object") module.exports = m
-	else window.m = m
 })()
\ No newline at end of file
diff --git a/request/request.js b/request/request.js
index 071600d6..7773f6dc 100644
--- a/request/request.js
+++ b/request/request.js
@@ -1,83 +1,94 @@
 "use strict"
 
 var buildQueryString = require("../querystring/build")
+var Stream = require("../util/stream")
 
-module.exports = function($window, Promise) {
+module.exports = function($window) {
 	var callbackCount = 0
 
+	var oncompletion
+	function setCompletionCallback(callback) {oncompletion = callback}
+	
 	function xhr(args) {
-		return new Promise(function(resolve, reject) {
-			var useBody = typeof args.useBody === "boolean" ? args.useBody : args.method !== "GET" && args.method !== "TRACE"
-			
-			if (typeof args.serialize !== "function") args.serialize = JSON.stringify
-			if (typeof args.deserialize !== "function") args.deserialize = deserialize
-			if (typeof args.extract !== "function") args.extract = extract
-			
-			args.url = interpolate(args.url, args.data)
-			if (useBody) args.data = args.serialize(args.data)
-			else args.url = assemble(args.url, args.data)
-			
-			var xhr = new $window.XMLHttpRequest()
-			xhr.open(args.method, args.url, typeof args.async === "boolean" ? args.async : true, typeof args.user === "string" ? args.user : undefined, typeof args.password === "string" ? args.password : undefined)
-			
-			if (args.serialize === JSON.stringify && useBody) {
-				xhr.setRequestHeader("Content-Type", "application/json; charset=utf-8")
-			}
-			if (args.deserialize === deserialize) {
-				xhr.setRequestHeader("Accept", "application/json, text/*")
-			}
-			
-			if (typeof args.config === "function") xhr = args.config(xhr, args) || xhr
-			
-			xhr.onreadystatechange = function() {
-				if (xhr.readyState === 4) {
-					try {
-						var response = args.deserialize(args.extract(xhr, args))
-						if (xhr.status >= 200 && xhr.status < 300) {
-							if (typeof args.type === "function") {
-								if (response instanceof Array) {
-									for (var i = 0; i < response.length; i++) {
-										response[i] = new args.type(response[i])
-									}
+		var stream = Stream.stream()
+		
+		var useBody = typeof args.useBody === "boolean" ? args.useBody : args.method !== "GET" && args.method !== "TRACE"
+		
+		if (typeof args.serialize !== "function") args.serialize = JSON.stringify
+		if (typeof args.deserialize !== "function") args.deserialize = deserialize
+		if (typeof args.extract !== "function") args.extract = extract
+		
+		args.url = interpolate(args.url, args.data)
+		if (useBody) args.data = args.serialize(args.data)
+		else args.url = assemble(args.url, args.data)
+		
+		var xhr = new $window.XMLHttpRequest()
+		xhr.open(args.method, args.url, typeof args.async === "boolean" ? args.async : true, typeof args.user === "string" ? args.user : undefined, typeof args.password === "string" ? args.password : undefined)
+		
+		if (args.serialize === JSON.stringify && useBody) {
+			xhr.setRequestHeader("Content-Type", "application/json; charset=utf-8")
+		}
+		if (args.deserialize === deserialize) {
+			xhr.setRequestHeader("Accept", "application/json, text/*")
+		}
+		
+		if (typeof args.config === "function") xhr = args.config(xhr, args) || xhr
+		
+		xhr.onreadystatechange = function() {
+			if (xhr.readyState === 4) {
+				try {
+					var response = args.deserialize(args.extract(xhr, args))
+					if (xhr.status >= 200 && xhr.status < 300) {
+						if (typeof args.type === "function") {
+							if (response instanceof Array) {
+								for (var i = 0; i < response.length; i++) {
+									response[i] = new args.type(response[i])
 								}
-								else response = new args.type(response)
 							}
-							
-							resolve(response)
+							else response = new args.type(response)
 						}
-						else reject(new Error(xhr.responseText))
-					}
-					catch (e) {
-						reject(e)
+						
+						stream(response)
 					}
+					else stream.error(new Error(xhr.responseText))
 				}
+				catch (e) {
+					stream.error(e)
+				}
+				if (typeof oncompletion === "function") oncompletion()
 			}
-			
-			if (useBody) xhr.send(args.data)
-			else xhr.send()
-		})
+		}
+		
+		if (useBody) xhr.send(args.data)
+		else xhr.send()
+		
+		return stream
 	}
 
 	function jsonp(args) {
-		return new Promise(function(resolve, reject) {
-			var callbackName = args.callbackName || "_mithril_" + Math.round(Math.random() * 1e16) + "_" + callbackCount++
-			var script = $window.document.createElement("script")
-			$window[callbackName] = function(data) {
-				script.parentNode.removeChild(script)
-				resolve(data)
-				delete $window[callbackName]
-			}
-			script.onerror = function() {
-				script.parentNode.removeChild(script)
-				reject(new Error("JSONP request failed"))
-				delete $window[callbackName]
-			}
-			if (args.data == null) args.data = {}
-			args.url = interpolate(args.url, args.data)
-			args.data[args.callbackKey || "callback"] = callbackName
-			script.src = assemble(args.url, args.data)
-			$window.document.documentElement.appendChild(script)
-		})
+		var stream = Stream.stream()
+		
+		var callbackName = args.callbackName || "_mithril_" + Math.round(Math.random() * 1e16) + "_" + callbackCount++
+		var script = $window.document.createElement("script")
+		$window[callbackName] = function(data) {
+			script.parentNode.removeChild(script)
+			stream(data)
+			if (typeof oncompletion === "function") oncompletion()
+			delete $window[callbackName]
+		}
+		script.onerror = function() {
+			script.parentNode.removeChild(script)
+			stream.error(new Error("JSONP request failed"))
+			if (typeof oncompletion === "function") oncompletion()
+			delete $window[callbackName]
+		}
+		if (args.data == null) args.data = {}
+		args.url = interpolate(args.url, args.data)
+		args.data[args.callbackKey || "callback"] = callbackName
+		script.src = assemble(args.url, args.data)
+		$window.document.documentElement.appendChild(script)
+		
+		return stream
 	}
 
 	function interpolate(url, data) {
@@ -110,5 +121,5 @@ module.exports = function($window, Promise) {
 
 	function extract(xhr) {return xhr.responseText}
 	
-	return {xhr: xhr, jsonp: jsonp}
+	return {xhr: xhr, jsonp: jsonp, setCompletionCallback: setCompletionCallback}
 }
diff --git a/request/tests/index.html b/request/tests/index.html
index 2d5f3120..e9bf02e0 100644
--- a/request/tests/index.html
+++ b/request/tests/index.html
@@ -9,9 +9,10 @@
 		<script src="../../querystring/parse.js"></script>
 		<script src="../../test-utils/parseURL.js"></script>
 		<script src="../../test-utils/callAsync.js"></script>
-		<script src="../../test-utils/ajaxMock.js"></script>
+		<script src="../../test-utils/xhrMock.js"></script>
 
 		<script src="../../querystring/build.js"></script>
+		<script src="../../util/stream.js"></script>
 		<script src="../../request/request.js"></script>
 		<script src="test-xhr.js"></script>
 		<script src="test-jsonp.js"></script>
diff --git a/request/tests/test-jsonp.js b/request/tests/test-jsonp.js
index 0335bbe3..fcb7f2c1 100644
--- a/request/tests/test-jsonp.js
+++ b/request/tests/test-jsonp.js
@@ -9,7 +9,7 @@ o.spec("jsonp", function() {
 	var mock, jsonp
 	o.beforeEach(function() {
 		mock = xhrMock()
-		jsonp = new Request(mock, Promise).jsonp
+		jsonp = new Request(mock).jsonp
 	})
 	
 	o("works", function(done) {
@@ -19,9 +19,9 @@ o.spec("jsonp", function() {
 				return {status: 200, responseText: queryData["callback"] + "(" + JSON.stringify({a: 1}) + ")"}
 			}
 		})
-		jsonp({url: "/item"}).then(function(data) {
+		jsonp({url: "/item"}).map(function(data) {
 			o(data).deepEquals({a: 1})
-		}).then(done)
+		}).map(done)
 	})
 	o("works w/ other querystring params", function(done) {
 		mock.$defineRoutes({
@@ -30,10 +30,10 @@ o.spec("jsonp", function() {
 				return {status: 200, responseText: queryData["callback"] + "(" + JSON.stringify(queryData) + ")"}
 			}
 		})
-		jsonp({url: "/item", data: {a: "b", c: "d"}}).then(function(data) {
+		jsonp({url: "/item", data: {a: "b", c: "d"}}).map(function(data) {
 			delete data["callback"]
 			o(data).deepEquals({a: "b", c: "d"})
-		}).then(done)
+		}).map(done)
 	})
 	o("works w/ custom callbackKey", function(done) {
 		mock.$defineRoutes({
@@ -42,9 +42,9 @@ o.spec("jsonp", function() {
 				return {status: 200, responseText: queryData["cb"] + "(" + JSON.stringify({a: 2}) + ")"}
 			}
 		})
-		jsonp({url: "/item", callbackKey: "cb"}).then(function(data) {
+		jsonp({url: "/item", callbackKey: "cb"}).map(function(data) {
 			o(data).deepEquals({a: 2})
-		}).then(done)
+		}).map(done)
 	})
 	o("handles error", function(done) {
 		jsonp({url: "/item", callbackKey: "cb"}).catch(function(e) {
diff --git a/request/tests/test-xhr.js b/request/tests/test-xhr.js
index 7be6e14e..88057603 100644
--- a/request/tests/test-xhr.js
+++ b/request/tests/test-xhr.js
@@ -8,7 +8,7 @@ o.spec("xhr", function() {
 	var mock, xhr
 	o.beforeEach(function() {
 		mock = xhrMock()
-		xhr = new Request(mock, Promise).xhr
+		xhr = new Request(mock).xhr
 	})
 	
 	o.spec("success", function() {
@@ -19,9 +19,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({a: 1})}
 				}
 			})
-			xhr({method: "GET", url: "/item"}).then(function(data) {
+			xhr({method: "GET", url: "/item"}).map(function(data) {
 				o(data).deepEquals({a: 1})
-			}).then(function() {
+			}).map(function() {
 				done()
 			})
 		})
@@ -31,9 +31,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({a: 1})}
 				}
 			})
-			xhr({method: "GET", url: "/item"}).then(function(data) {
+			xhr({method: "GET", url: "/item"}).map(function(data) {
 				o(data).deepEquals({a: 1})
-			}).then(done)
+			}).map(done)
 		})
 		o("works w/ parameterized data via GET", function(done) {
 			mock.$defineRoutes({
@@ -41,9 +41,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({a: request.query})}
 				}
 			})
-			xhr({method: "GET", url: "/item", data: {x: "y"}}).then(function(data) {
+			xhr({method: "GET", url: "/item", data: {x: "y"}}).map(function(data) {
 				o(data).deepEquals({a: "?x=y"})
-			}).then(done)
+			}).map(done)
 		})
 		o("works w/ parameterized data via POST", function(done) {
 			mock.$defineRoutes({
@@ -51,9 +51,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({a: JSON.parse(request.body)})}
 				}
 			})
-			xhr({method: "POST", url: "/item", data: {x: "y"}}).then(function(data) {
+			xhr({method: "POST", url: "/item", data: {x: "y"}}).map(function(data) {
 				o(data).deepEquals({a: {x: "y"}})
-			}).then(done)
+			}).map(done)
 		})
 		o("works w/ parameterized data containing colon via GET", function(done) {
 			mock.$defineRoutes({
@@ -61,9 +61,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({a: request.query})}
 				}
 			})
-			xhr({method: "GET", url: "/item", data: {x: ":y"}}).then(function(data) {
+			xhr({method: "GET", url: "/item", data: {x: ":y"}}).map(function(data) {
 				o(data).deepEquals({a: "?x=%3Ay"})
-			}).then(done)
+			}).map(done)
 		})
 		o("works w/ parameterized data containing colon via POST", function(done) {
 			mock.$defineRoutes({
@@ -71,9 +71,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({a: JSON.parse(request.body)})}
 				}
 			})
-			xhr({method: "POST", url: "/item", data: {x: ":y"}}).then(function(data) {
+			xhr({method: "POST", url: "/item", data: {x: ":y"}}).map(function(data) {
 				o(data).deepEquals({a: {x: ":y"}})
-			}).then(done)
+			}).map(done)
 		})
 		o("works w/ parameterized url via GET", function(done) {
 			mock.$defineRoutes({
@@ -81,9 +81,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({a: request.url, b: request.query})}
 				}
 			})
-			xhr({method: "GET", url: "/item/:x", data: {x: "y"}}).then(function(data) {
+			xhr({method: "GET", url: "/item/:x", data: {x: "y"}}).map(function(data) {
 				o(data).deepEquals({a: "/item/y", b: {}})
-			}).then(done)
+			}).map(done)
 		})
 		o("works w/ parameterized url via POST", function(done) {
 			mock.$defineRoutes({
@@ -91,9 +91,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({a: request.url, b: JSON.parse(request.body)})}
 				}
 			})
-			xhr({method: "POST", url: "/item/:x", data: {x: "y"}}).then(function(data) {
+			xhr({method: "POST", url: "/item/:x", data: {x: "y"}}).map(function(data) {
 				o(data).deepEquals({a: "/item/y", b: {}})
-			}).then(done)
+			}).map(done)
 		})
 		o("ignores unresolved parameter via GET", function(done) {
 			mock.$defineRoutes({
@@ -101,9 +101,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({a: request.url})}
 				}
 			})
-			xhr({method: "GET", url: "/item/:x"}).then(function(data) {
+			xhr({method: "GET", url: "/item/:x"}).map(function(data) {
 				o(data).deepEquals({a: "/item/:x"})
-			}).then(done)
+			}).map(done)
 		})
 		o("ignores unresolved parameter via POST", function(done) {
 			mock.$defineRoutes({
@@ -111,9 +111,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({a: request.url})}
 				}
 			})
-			xhr({method: "GET", url: "/item/:x"}).then(function(data) {
+			xhr({method: "GET", url: "/item/:x"}).map(function(data) {
 				o(data).deepEquals({a: "/item/:x"})
-			}).then(done)
+			}).map(done)
 		})
 		o("type parameter works for Array responses", function(done) {
 			var Entity = function(args) {
@@ -125,9 +125,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify([{id: 1}, {id: 2}, {id: 3}])}
 				}
 			})
-			xhr({method: "GET", url: "/item", type: Entity}).then(function(data) {
+			xhr({method: "GET", url: "/item", type: Entity}).map(function(data) {
 				o(data).deepEquals([{_id: 1}, {_id: 2}, {_id: 3}])
-			}).then(done)
+			}).map(done)
 		})
 		o("type parameter works for Object responses", function(done) {
 			var Entity = function(args) {
@@ -139,9 +139,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({id: 1})}
 				}
 			})
-			xhr({method: "GET", url: "/item", type: Entity}).then(function(data) {
+			xhr({method: "GET", url: "/item", type: Entity}).map(function(data) {
 				o(data).deepEquals({_id: 1})
-			}).then(done)
+			}).map(done)
 		})
 		o("serialize parameter works in GET", function(done) {
 			var serialize = function(data) {
@@ -153,9 +153,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({body: request.query})}
 				}
 			})
-			xhr({method: "GET", url: "/item", serialize: serialize, data: {id: 1}}).then(function(data) {
+			xhr({method: "GET", url: "/item", serialize: serialize, data: {id: 1}}).map(function(data) {
 				o(data.body).equals("?id=1")
-			}).then(done)
+			}).map(done)
 		})
 		o("serialize parameter works in POST", function(done) {
 			var serialize = function(data) {
@@ -167,9 +167,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({body: request.body})}
 				}
 			})
-			xhr({method: "POST", url: "/item", serialize: serialize, data: {id: 1}}).then(function(data) {
+			xhr({method: "POST", url: "/item", serialize: serialize, data: {id: 1}}).map(function(data) {
 				o(data.body).equals("id=1")
-			}).then(done)
+			}).map(done)
 		})
 		o("deserialize parameter works in GET", function(done) {
 			var deserialize = function(data) {
@@ -181,9 +181,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({test: 123})}
 				}
 			})
-			xhr({method: "GET", url: "/item", deserialize: deserialize}).then(function(data) {
+			xhr({method: "GET", url: "/item", deserialize: deserialize}).map(function(data) {
 				o(data).equals("{\"test\":123}")
-			}).then(done)
+			}).map(done)
 		})
 		o("deserialize parameter works in POST", function(done) {
 			var deserialize = function(data) {
@@ -195,9 +195,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: JSON.stringify({test: 123})}
 				}
 			})
-			xhr({method: "POST", url: "/item", deserialize: deserialize}).then(function(data) {
+			xhr({method: "POST", url: "/item", deserialize: deserialize}).map(function(data) {
 				o(data).equals("{\"test\":123}")
-			}).then(done)
+			}).map(done)
 		})
 		o("extract parameter works in GET", function(done) {
 			var extract = function(data) {
@@ -209,9 +209,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: ""}
 				}
 			})
-			xhr({method: "GET", url: "/item", extract: extract}).then(function(data) {
+			xhr({method: "GET", url: "/item", extract: extract}).map(function(data) {
 				o(data).deepEquals({test: 123})
-			}).then(done)
+			}).map(done)
 		})
 		o("extract parameter works in POST", function(done) {
 			var extract = function(data) {
@@ -223,9 +223,9 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: ""}
 				}
 			})
-			xhr({method: "POST", url: "/item", extract: extract}).then(function(data) {
+			xhr({method: "POST", url: "/item", extract: extract}).map(function(data) {
 				o(data).deepEquals({test: 123})
-			}).then(done)
+			}).map(done)
 		})
 		o("config parameter works", function(done) {
 			mock.$defineRoutes({
@@ -233,7 +233,7 @@ o.spec("xhr", function() {
 					return {status: 200, responseText: ""}
 				}
 			})
-			xhr({method: "POST", url: "/item", config: config}).then(done)
+			xhr({method: "POST", url: "/item", config: config}).map(done)
 			
 			function config(xhr) {
 				o(typeof xhr.setRequestHeader).equals("function")
@@ -251,7 +251,7 @@ o.spec("xhr", function() {
 			})
 			xhr({method: "GET", url: "/item"}).catch(function(e) {
 				o(e.message).equals(JSON.stringify({error: "error"}))
-			}).then(done)
+			}).map(done)
 		})
 		o("rejects on non-JSON server error", function(done) {
 			mock.$defineRoutes({
@@ -261,7 +261,7 @@ o.spec("xhr", function() {
 			})
 			xhr({method: "GET", url: "/item"}).catch(function(e) {
 				o(e.message).equals("error")
-			}).then(done)
+			}).map(done)
 		})
 	})
 })
\ No newline at end of file
diff --git a/util/prop.js b/util/prop.js
deleted file mode 100644
index d5174796..00000000
--- a/util/prop.js
+++ /dev/null
@@ -1,8 +0,0 @@
-"use strict"
-
-module.exports = function(store) {
-	return function() {
-		if (arguments.length > 0) store = arguments[0]
-		return store
-	}
-}
\ No newline at end of file
diff --git a/util/stream.js b/util/stream.js
new file mode 100644
index 00000000..222ec078
--- /dev/null
+++ b/util/stream.js
@@ -0,0 +1,159 @@
+"use strict"
+
+var guid = 0, noop = function() {}, HALT = {}
+function createStream() {
+	function stream() {
+		if (arguments.length > 0) updateStream(stream, arguments[0], undefined)
+		return stream._state.value
+	}
+	initStream(stream, arguments)
+	
+	if (arguments.length > 0) updateStream(stream, arguments[0], undefined)
+	
+	return stream
+}
+function initStream(stream, args) {
+	stream.constructor = createStream
+	stream._state = {id: guid++, value: undefined, error: undefined, state: 0, derive: undefined, recover: undefined, deps: {}, parents: [], errorStream: undefined, endStream: undefined}
+	stream.map = map, stream.ap = ap, stream.of = createStream
+	stream.valueOf = valueOf
+	stream.catch = doCatch
+	
+	Object.defineProperties(stream, {
+		error: {get: function() {
+			if (!stream._state.errorStream) {
+				var errorStream = function() {
+					if (arguments.length > 0) updateStream(stream, undefined, arguments[0])
+					return stream._state.error
+				}
+				initStream(errorStream, [])
+				initDependency(errorStream, [stream], noop, noop)
+				stream._state.errorStream = errorStream
+			}
+			return stream._state.errorStream
+		}},
+		end: {get: function() {
+			if (!stream._state.endStream) {
+				var endStream = createStream()
+				endStream.map(function(value) {
+					if (value === true) unregisterStream(stream), unregisterStream(endStream)
+					return value
+				})
+				stream._state.endStream = endStream
+			}
+			return stream._state.endStream
+		}}
+	})
+}
+function updateStream(stream, value, error) {
+	if (!absorbStream(stream, value, false) && !absorbStream(stream, error, true)) {
+		updateState(stream, value, error)
+		for (var id in stream._state.deps) updateDependency(stream._state.deps[id], false)
+		finalize(stream)
+	}
+}
+function updateState(stream, value, error) {
+	if (error !== undefined && typeof stream._state.recover === "function") {
+		try {updateValues(stream, stream._state.recover(), undefined)}
+		catch (e) {updateValues(stream, undefined, e)}
+	}
+	else updateValues(stream, value, error)
+	stream._state.changed = true
+	if (stream._state.state !== 2) stream._state.state = 1
+}
+function updateValues(stream, value, error) {
+	stream._state.value = value
+	stream._state.error = error
+}
+function updateDependency(stream, mustSync) {
+	var state = stream._state, parents = state.parents
+	if (parents.length > 0 && parents.filter(active).length === parents.length && (mustSync || parents.filter(changed).length > 0)) {
+		var failed = parents.filter(errored)
+		if (failed.length > 0) updateState(stream, undefined, failed[0]._state.error)
+		else {
+			try {
+				var value = state.derive()
+				if (!absorbStream(stream, value)) updateState(stream, value, undefined)
+			}
+			catch (e) {
+				updateState(stream, undefined, e)
+			}
+		}
+	}
+}
+function absorbStream(stream, value, isError) {
+	if (value != null && value.constructor === createStream) {
+		if (value._state.state === 2) {
+			stream.end(true)
+			stream(value())
+		}
+		else if (value._state.error) stream.error(value.error())
+		else if (value._state.state === 0) return true
+		else if (!isError) stream(value())
+		else stream.error(value())
+		return true
+	}
+	return false
+}
+function finalize(stream) {
+	stream._state.changed = false
+	for (var id in stream._state.deps) stream._state.deps[id]._state.changed = false
+}
+
+function doCatch(fn) {
+	var stream = this
+	var derive = function() {return stream._state.value}
+	var recover = function() {return fn(stream._state.error)}
+	return initDependency(createStream(), [stream], derive, recover)
+}
+function combine(fn, streams) {
+	return initDependency(createStream(), streams, function() {
+		var failed = streams.filter(errored)
+		if (failed.length > 0) throw failed[0]._state.error
+		return fn.apply(this, streams.concat([streams.filter(changed)]))
+	}, undefined)
+}
+
+function initDependency(dep, streams, derive, recover) {
+	var state = dep._state
+	state.derive = derive
+	state.recover = recover
+	state.parents = streams.filter(notEnded)
+	
+	registerDependency(dep, state.parents)
+	updateDependency(dep, true)
+	
+	return dep
+}
+function registerDependency(stream, parents) {
+	for (var i = 0; i < parents.length; i++) {
+		parents[i]._state.deps[stream._state.id] = stream
+		registerDependency(stream, parents[i]._state.parents)
+	}
+}
+function unregisterStream(stream) {
+	for (var id in stream._state.deps) {
+		var dependent = stream._state.deps[id]
+		var index = dependent._state.parents.indexOf(stream)
+		if (index > -1) dependent._state.parents.splice(index, 1)
+	}
+	stream._state.state = 2 //ended
+	stream._state.deps = {}
+}
+
+function map(fn) {return combine(function(stream) {return fn(stream())}, [this])}
+function ap(stream) {return combine(function(s1, s2) {return s1()(s2())}, [this, stream])}
+function valueOf() {return this._state.value}
+
+function active(stream) {return stream._state.state === 1}
+function changed(stream) {return stream._state.changed}
+function notEnded(stream) {return stream._state.state !== 2}
+function errored(stream) {return stream._state.error}
+
+function reject(e) {
+	var stream = createStream()
+	stream.error(e)
+	return stream
+}
+
+module.exports = {stream: createStream, combine: combine, reject: reject}
diff --git a/util/tests/index.html b/util/tests/index.html
index e156fad4..26954980 100644
--- a/util/tests/index.html
+++ b/util/tests/index.html
@@ -6,11 +6,12 @@
 	<body>
 		<script src="../../module/module.js"></script>
 		<script src="../../ospec/ospec.js"></script>
+		<script src="../../test-utils/callAsync.js"></script>
 
-		<script src="../../util/prop.js"></script>
 		<script src="../../util/withAttr.js"></script>
-		<script src="test-prop.js"></script>
+		<script src="../../util/stream.js"></script>
 		<script src="test-withAttr.js"></script>
+		<script src="test-stream.js"></script>
 		
 		<script>require("../../ospec/ospec").run()</script>
 	</body>
diff --git a/util/tests/test-prop.js b/util/tests/test-prop.js
deleted file mode 100644
index 124c5d5a..00000000
--- a/util/tests/test-prop.js
+++ /dev/null
@@ -1,16 +0,0 @@
-"use strict"
-
-var o = require("../../ospec/ospec")
-var prop = require("../../util/prop")
-
-o.spec("prop", function() {
-	o("works", function() {
-		var store = prop(1)
-		var initialValue = store()
-		store(2)
-		var newValue = store()
-		
-		o(initialValue).equals(1)
-		o(newValue).equals(2)
-	})
-})
\ No newline at end of file
diff --git a/util/tests/test-stream.js b/util/tests/test-stream.js
new file mode 100644
index 00000000..099ee4b6
--- /dev/null
+++ b/util/tests/test-stream.js
@@ -0,0 +1,779 @@
+"use strict"
+
+var o = require("../../ospec/ospec")
+var callAsync = require("../../test-utils/callAsync")
+var Stream = require("../../util/stream")
+
+o.spec("stream", function() {
+	o.spec("stream", function() {
+		o("works as getter/setter", function() {
+			var stream = Stream.stream(1)
+			var initialValue = stream()
+			stream(2)
+			var newValue = stream()
+			
+			o(initialValue).equals(1)
+			o(newValue).equals(2)
+		})
+		o("has undefined value by default", function() {
+			var stream = Stream.stream()
+			
+			o(stream()).equals(undefined)
+		})
+		o("can update to undefined", function() {
+			var stream = Stream.stream(1)
+			stream(undefined)
+			
+			o(stream()).equals(undefined)
+		})
+	})
+	o.spec("combine", function() {
+		o("transforms value", function() {
+			var stream = Stream.stream()
+			var doubled = Stream.combine(function(s) {return s() * 2}, [stream])
+			
+			stream(2)
+			
+			o(doubled()).equals(4)
+		})
+		o("transforms default value", function() {
+			var stream = Stream.stream(2)
+			var doubled = Stream.combine(function(s) {return s() * 2}, [stream])
+			
+			o(doubled()).equals(4)
+		})
+		o("transforms multiple values", function() {
+			var s1 = Stream.stream()
+			var s2 = Stream.stream()
+			var added = Stream.combine(function(s1, s2) {return s1() + s2()}, [s1, s2])
+			
+			s1(2)
+			s2(3)
+			
+			o(added()).equals(5)
+		})
+		o("transforms multiple default values", function() {
+			var s1 = Stream.stream(2)
+			var s2 = Stream.stream(3)
+			var added = Stream.combine(function(s1, s2) {return s1() + s2()}, [s1, s2])
+			
+			o(added()).equals(5)
+		})
+		o("transforms mixed default and late-bound values", function() {
+			var s1 = Stream.stream(2)
+			var s2 = Stream.stream()
+			var added = Stream.combine(function(s1, s2) {return s1() + s2()}, [s1, s2])
+			
+			s2(3)
+			
+			o(added()).equals(5)
+		})
+		o("combines atomically", function() {
+			var count = 0
+			var a = Stream.stream()
+			var b = Stream.combine(function(a) {return a() * 2}, [a])
+			var c = Stream.combine(function(a) {return a() * a()}, [a])
+			var d = Stream.combine(function(b, c) {
+				count++
+				return b() + c()
+			}, [b, c])
+			
+			a(3)
+			
+			o(d()).equals(15)
+			o(count).equals(1)
+		})
+		o("combines default value atomically", function() {
+			var count = 0
+			var a = Stream.stream(3)
+			var b = Stream.combine(function(a) {return a() * 2}, [a])
+			var c = Stream.combine(function(a) {return a() * a()}, [a])
+			var d = Stream.combine(function(b, c) {
+				count++
+				return b() + c()
+			}, [b, c])
+			
+			o(d()).equals(15)
+			o(count).equals(1)
+		})
+		o("combine lists only changed upstreams in last arg", function() {
+			var streams = []
+			var a = Stream.stream()
+			var b = Stream.stream()
+			var c = Stream.combine(function(a, b, changed) {
+				streams = changed
+			}, [a, b])
+			
+			a(3)
+			b(5)
+			
+			o(streams.length).equals(1)
+			o(streams[0]).equals(b)
+		})
+		o("combine lists only changed upstreams in last arg with default value", function() {
+			var streams = []
+			var a = Stream.stream(3)
+			var b = Stream.stream(5)
+			var c = Stream.combine(function(a, b, changed) {
+				streams = changed
+			}, [a, b])
+			
+			a(7)
+			
+			o(streams.length).equals(1)
+			o(streams[0]).equals(a)
+		})
+		o("combine can return undefined", function() {
+			var a = Stream.stream(1)
+			var b = Stream.combine(function(a) {
+				return undefined
+			}, [a])
+			
+			o(b()).equals(undefined)
+		})
+		o("combine absorbs streams", function() {
+			var a = Stream.stream(1)
+			var b = Stream.combine(function(a) {
+				return Stream.stream(2)
+			}, [a])
+			
+			o(b()).equals(2)
+		})
+		o("combine absorbs errored streams", function() {
+			var a = Stream.stream(1)
+			var b = Stream.combine(function(a) {
+				return Stream.reject(new Error("error"))
+			}, [a])
+			
+			o(b()).equals(undefined)
+			o(b.error().message).equals("error")
+		})
+		o("combine absorbs ready streams", function() {
+			var count = 0
+			var a = Stream.stream(1)
+			var b = Stream.combine(function(a) {
+				return Stream.stream()
+			}, [a])
+			var c = Stream.combine(function(b) {
+				count++
+				return 2
+			}, [b])
+			
+			o(c()).equals(undefined)
+			o(count).equals(0)
+		})
+	})
+	o.spec("end", function() {
+		o("end stream works", function() {
+			var stream = Stream.stream()
+			var doubled = Stream.combine(function(stream) {return stream() * 2}, [stream])
+			
+			stream.end(true)
+			
+			stream(3)
+			
+			o(doubled()).equals(undefined)
+		})
+		o("end stream works with default value", function() {
+			var stream = Stream.stream(2)
+			var doubled = Stream.combine(function(stream) {return stream() * 2}, [stream])
+			
+			stream.end(true)
+			
+			stream(3)
+			
+			o(doubled()).equals(4)
+		})
+		o("cannot add downstream to ended stream", function() {
+			var stream = Stream.stream(2)
+			stream.end(true)
+			
+			var doubled = Stream.combine(function(stream) {return stream() * 2}, [stream])
+			stream(3)
+			
+			o(doubled()).equals(undefined)
+		})
+	})
+	o.spec("error", function() {
+		o("error() works", function() {
+			var stream = Stream.stream()
+			var errored = Stream.combine(function(stream) {throw new Error("error")}, [stream])
+			
+			stream(3)
+			
+			o(errored()).equals(undefined)
+			o(errored.error().message).equals("error")
+		})
+		o("error() works with default value", function() {
+			var stream = Stream.stream(3)
+			var errored = Stream.combine(function(stream) {throw new Error("error")}, [stream])
+			
+			o(errored()).equals(undefined)
+			o(errored.error().message).equals("error")
+		})
+		o("error() removes error on valid value", function() {
+			var stream = Stream.stream("a")
+			var doubled = Stream.combine(function(stream) {
+				if (typeof stream() !== "number") throw new Error("error")
+				else return stream() * 2
+			}, [stream])
+			
+			stream(3)
+			
+			o(doubled()).equals(6)
+			o(doubled.error()).equals(undefined)
+		})
+		o("error() triggers catch", function() {
+			var count = 0
+			var stream = Stream.stream(1)
+			var handled = stream.catch(function() {
+				count++
+				return 2
+			})
+			
+			stream.error(new Error("error"))
+			
+			o(handled()).equals(2)
+			o(handled.error()).equals(undefined)
+			o(count).equals(1)
+		})
+		o("thrown error propagates downstream", function() {
+			var count = 0
+			var stream = Stream.stream(1)
+				.map(function() {throw new Error("error")})
+				.map(function(value) {
+					count++
+					return value * 2
+				})
+				.map(function(value) {
+					count++
+					return value * 3
+				})
+			
+			o(stream()).equals(undefined)
+			o(stream.error().message).equals("error")
+			o(count).equals(0)
+		})
+		o("set error propagates downstream", function() {
+			var count = 0
+			var stream = Stream.stream()
+			var mapped = stream.map(function(value) {
+				count++
+				return value * 2
+			})
+			.map(function(value) {
+				count++
+				return value * 3
+			})
+			stream.error(new Error("error"))
+			
+			o(mapped()).equals(undefined)
+			o(mapped.error().message).equals("error")
+			o(count).equals(0)
+		})
+		o("error.map works", function() {
+			var stream = Stream.stream(1)
+			var mappedFromError = stream.error.map(function(value) {
+				return "from" + value.message
+			})
+			
+			o(mappedFromError()).equals(undefined)
+			
+			stream.error(new Error("error"))
+			
+			o(mappedFromError()).equals("fromerror")
+		})
+		o("error from error.map propagates", function() {
+			var stream = Stream.stream(1)
+			var mappedFromError = stream.error.map(function(value) {
+				return "from" + value.message
+			}).map(function(value) {
+				return "a" + value
+			})
+			
+			o(mappedFromError()).equals(undefined)
+			
+			stream.error(new Error("error"))
+			
+			o(mappedFromError()).equals("afromerror")
+		})
+		o("error thrown from error.map propagates downstream", function() {
+			var count = 0
+			var stream = Stream.stream(1)
+			var mappedFromError = stream.error.map(function(value) {
+				throw new Error("b")
+			})
+			
+			var downstream = mappedFromError.map(function() {
+				count++
+			})
+			
+			o(mappedFromError()).equals(undefined)
+			
+			stream.error(new Error("a"))
+			
+			o(mappedFromError()).equals(undefined)
+			o(mappedFromError.error().message).equals("b")
+			o(downstream()).equals(undefined)
+			o(downstream.error().message).equals("b")
+			o(count).equals(0)
+		})
+		o("error.map absorbs streams", function() {
+			var stream = Stream.reject(new Error("error"))
+			var error = stream.error.map(function(value) {
+				return Stream.stream(1)
+			})
+			
+			o(error()).equals(1)
+		})
+	})
+	o.spec("reject", function() {
+		o("reject works", function() {
+			var stream = Stream.reject(new Error("error"))
+			
+			o(stream()).equals(undefined)
+			o(stream.error().message).equals("error")
+		})
+		o("rejected propagates downstream", function() {
+			var count = 0
+			var stream = Stream.reject(new Error("error"))
+				.map(function(value) {
+					count++
+					return value * 2
+				})
+				.map(function(value) {
+					count++
+					return value * 3
+				})
+			
+			o(stream()).equals(undefined)
+			o(stream.error().message).equals("error")
+		})
+		o("rejected removes error on value", function() {
+			var stream = Stream.reject(new Error("error"))
+			var doubled = stream.map(function(value) {
+				return value * 2
+			})
+			
+			stream(1)
+			
+			o(doubled()).equals(2)
+			o(stream.error()).equals(undefined)
+		})
+		o("combined rejected yields first error", function() {
+			var count = 0
+			var a = Stream.reject(new Error("a"))
+			var b = Stream.reject(new Error("b"))
+			var combined = Stream.combine(function(a, b) {
+				count++
+				return a() + b()
+			}, [a, b])
+			
+			o(combined()).equals(undefined)
+			o(combined.error().message).equals("a")
+			o(count).equals(0)
+		})
+	})
+	o.spec("catch", function() {
+		o("catch works from reject", function() {
+			var count = 0
+			var stream = Stream.reject(new Error("error")).catch(function(e) {
+				count++
+				return "no" + e.message
+			}).map(function(value) {
+				return value + "mapped"
+			})
+			
+			o(count).equals(1)
+			o(stream()).equals("noerrormapped")
+			o(stream.error()).equals(undefined)
+		})
+		o("catch works from combine", function() {
+			var count = 0
+			var stream = Stream.combine(function() {throw new Error("error")}, [Stream.stream(1)]).catch(function(e) {
+				count++
+				return "no" + e.message
+			}).map(function(value) {
+				return value + "mapped"
+			})
+			
+			o(count).equals(1)
+			o(stream()).equals("noerrormapped")
+			o(stream.error()).equals(undefined)
+		})
+		o("catch is not called if no error", function() {
+			var count = 0
+			var stream = Stream.stream()
+			var handled = stream.map(function(value) {return value + value}).catch(function(e) {
+				count++
+				return "no" + e.message
+			}).map(function(value) {
+				return value + "mapped"
+			})
+			
+			stream("a")
+			
+			o(count).equals(0)
+			o(handled()).equals("aamapped")
+			o(handled.error()).equals(undefined)
+		})
+		o("catch is not called if no error with default value", function() {
+			var count = 0
+			var stream = Stream.stream("a").map(function(value) {return value + value}).catch(function(e) {
+				count++
+				return "no" + e.message
+			}).map(function(value) {
+				return value + "mapped"
+			})
+			
+			o(count).equals(0)
+			o(stream()).equals("aamapped")
+			o(stream.error()).equals(undefined)
+		})
+		o("throwing from catch rejects", function() {
+			var stream = Stream.reject(new Error("a")).catch(function(e) {
+				throw new Error("b")
+			})
+			var mapped = stream.map(function(value) {return value + "ok"})
+			
+			o(stream()).equals(undefined)
+			o(stream.error().message).equals("b")
+			o(mapped()).equals(undefined)
+			o(mapped.error().message).equals("b")
+		})
+		o("catch can return undefined", function() {
+			var stream = Stream.reject(new Error("b")).catch(function(e) {}).map(function(value) {return String(value)})
+			
+			o(stream()).equals("undefined")
+			o(stream.error()).equals(undefined)
+		})
+		o("catch does not prevent sibling error propagation", function() {
+			var a = Stream.reject(new Error("a"))
+			var b = a.map(function(value) {return value + "b"}).catch(function(e) {})
+			var c = a.map(function(value) {return value + "c"})
+			var d = Stream.combine(function(b, c) {return b() + c()}, [b, c])
+			
+			o(d()).equals(undefined)
+			o(d.error().message).equals("a")
+		})
+		o("catches absorbed rejected stream", function() {
+			var caught
+			var stream = Stream.stream(1).map(function() {
+				return Stream.reject(new Error("error"))
+			}).catch(function(value) {
+				caught = value
+				return "no" + value.message
+			}).map(function(value) {
+				return value + "mapped"
+			})
+			
+			o(stream()).equals("noerrormapped")
+		})
+	})
+	o.spec("map", function() {
+		o("works", function() {
+			var stream = Stream.stream()
+			var doubled = stream.map(function(value) {return value * 2})
+			
+			stream(3)
+			
+			o(doubled()).equals(6)
+		})
+		o("works with default value", function() {
+			var stream = Stream.stream(3)
+			var doubled = stream.map(function(value) {return value * 2})
+			
+			o(doubled()).equals(6)
+		})
+		o("works with undefined value", function() {
+			var stream = Stream.stream()
+			var mapped = stream.map(function(value) {return String(value)})
+			
+			stream(undefined)
+			
+			o(mapped()).equals("undefined")
+		})
+		o("works with default undefined value", function() {
+			var stream = Stream.stream(undefined)
+			var mapped = stream.map(function(value) {return String(value)})
+			
+			o(mapped()).equals("undefined")
+		})
+	})
+	o.spec("ap", function() {
+		o("works", function() {
+			var apply = Stream.stream(function(value) {return value * 2})
+			var stream = Stream.stream(3)
+			var applied = apply.ap(stream)
+			
+			o(applied()).equals(6)
+			
+			apply(function(value) {return value / 3})
+			
+			o(applied()).equals(1)
+			
+			stream(9)
+			
+			o(applied()).equals(3)
+		})
+		o("works with undefined value", function() {
+			var apply = Stream.stream(function(value) {return String(value)})
+			var stream = Stream.stream(undefined)
+			var applied = apply.ap(stream)
+			
+			o(applied()).equals("undefined")
+			
+			apply(function(value) {return String(value) + "a"})
+			
+			o(applied()).equals("undefineda")
+		})
+	})
+	o.spec("absorbing semantics", function() {
+		o("absorbs stream", function() {
+			var stream = Stream.stream(Stream.stream(1))
+			var doubled = stream.map(function(value) {return value * 2})
+			
+			o(stream()).equals(1)
+			o(doubled()).equals(2)
+		})
+		o("absorbs stream on update", function() {
+			var stream = Stream.stream()
+			var doubled = stream.map(function(value) {return value * 2})
+			
+			stream(Stream.stream(1))
+			
+			o(stream()).equals(1)
+			o(doubled()).equals(2)
+		})
+		o("absorbs errored stream", function() {
+			var stream = Stream.stream(Stream.reject(1))
+			var doubled = stream.error.map(function(value) {return value * 2})
+			
+			o(stream()).equals(undefined)
+			o(stream.error()).equals(1)
+			o(doubled()).equals(2)
+		})
+		o("absorbs pending stream", function() {
+			var count = 0
+			var stream = Stream.stream(Stream.stream())
+			var mapped = stream.map(function() {
+				count++
+			})
+			
+			o(stream()).equals(undefined)
+			o(count).equals(0)
+		})
+		o("absorbs ended stream", function() {
+			var count = 0
+			var ended = Stream.stream()
+			ended.end(true)
+			
+			var stream = Stream.stream(ended)
+			var mapped = stream.map(function() {
+				count++
+			})
+			
+			stream(1)
+			
+			o(count).equals(0)
+		})
+		o("combine absorbs stream", function() {
+			var stream = Stream.stream(1)
+			var combined = Stream.combine(function(stream) {
+				return Stream.stream(2)
+			}, [stream])
+			var doubled = combined.map(function(value) {return value * 2})
+			
+			o(combined()).equals(2)
+			o(doubled()).equals(4)
+		})
+		o("combine absorbs errored stream", function() {
+			var stream = Stream.stream(1)
+			var combined = Stream.combine(function(stream) {
+				return Stream.reject(2)
+			}, [stream])
+			var doubled = combined.error.map(function(value) {return value * 2})
+			
+			o(combined()).equals(undefined)
+			o(combined.error()).equals(2)
+			o(doubled()).equals(4)
+		})
+		o("combine absorbs pending stream", function() {
+			var count = 0
+			var stream = Stream.stream(1)
+			var combined = Stream.combine(function(stream) {
+				return Stream.stream()
+			}, [stream])
+			var mapped = combined.map(function() {
+				count++
+			})
+			
+			o(combined()).equals(undefined)
+			o(count).equals(0)
+		})
+		o("combine absorbs ended stream", function() {
+			var count = 0
+			var stream = Stream.stream(1)
+			var combined = Stream.combine(function(stream) {
+				var ended = Stream.stream(2)
+				ended.end(true)
+				return ended
+			}, [stream])
+			var mapped = combined.map(function() {
+				count++
+			})
+			
+			o(combined()).equals(2)
+			o(count).equals(0)
+		})
+		o("reject absorbs stream", function() {
+			var stream = Stream.reject(Stream.stream(1))
+			var doubled = stream.error.map(function(value) {return value * 2})
+			
+			o(stream.error()).equals(1)
+			o(doubled()).equals(2)
+		})
+		o("reject absorbs errored stream", function() {
+			var count = 0
+			var stream = Stream.reject(Stream.reject(new Error("error")))
+			var mapped = stream.error.map(function() {
+				count++
+			})
+			
+			o(stream.error().message).equals("error")
+			o(count).equals(1)
+		})
+		o("reject absorbs pending stream", function() {
+			var count = 0
+			var stream = Stream.reject(Stream.stream())
+			var mapped = stream.error.map(function() {
+				count++
+			})
+			
+			o(stream.error()).equals(undefined)
+			o(count).equals(0)
+		})
+		o("reject absorbs ended stream", function() {
+			var count = 0
+			var ended = Stream.stream(1)
+			ended.end(true)
+			
+			var stream = Stream.reject(ended)
+			var mapped = stream.error.map(function() {
+				count++
+			})
+			
+			o(count).equals(0)
+		})
+		o("ended stream absorbs stream", function() {
+			var stream = Stream.stream()
+			stream.end(true)
+			
+			var doubled = stream.map(function(value) {return value * 2})
+			stream(Stream.stream(1))
+			
+			o(stream()).equals(1)
+			o(doubled()).equals(undefined)
+		})
+		o("ended stream absorbs pending stream", function() {
+			var stream = Stream.stream()
+			stream.end(true)
+			
+			var doubled = stream.map(function(value) {return value * 2})
+			stream(Stream.stream())
+			
+			o(stream()).equals(undefined)
+			o(doubled()).equals(undefined)
+		})
+		o("ended stream absorbs errored stream", function() {
+			var stream = Stream.stream()
+			stream.end(true)
+			
+			var doubled = stream.map(function(value) {return value * 2})
+			stream(Stream.reject(new Error("error")))
+			
+			o(stream.error().message).equals("error")
+			o(doubled()).equals(undefined)
+		})
+		o("ended stream absorbs ended stream", function() {
+			var stream = Stream.stream(1)
+			stream.end(true)
+			
+			var ended = Stream.stream(2)
+			ended.end(true)
+			
+			var doubled = stream.map(function(value) {return value * 2})
+			stream(ended)
+			
+			o(stream()).equals(2)
+			o(doubled()).equals(undefined)
+		})
+	})
+	o.spec("fantasy-land", function() {
+		o.spec("functor", function() {
+			o("identity", function() {
+				var stream = Stream.stream(3)
+				var mapped = stream.map(function(value) {return value})
+				
+				o(stream()).equals(mapped())
+			})
+			o("composition", function() {
+				function f(x) {return x * 2}
+				function g(x) {return x * x}
+				
+				var stream = Stream.stream(3)
+				
+				var mapped = stream.map(function(value) {return f(g(value))})
+				var composed = stream.map(g).map(f)
+				
+				o(mapped()).equals(18)
+				o(mapped()).equals(composed())
+			})
+		})
+		o.spec("apply", function() {
+			o("composition", function() {
+				var a = Stream.stream(function(value) {return value * 2})
+				var u = Stream.stream(function(value) {return value * 3})
+				var v = Stream.stream(5)
+				
+				var mapped = a.map(function(f) {
+					return function(g) {
+						return function(x) {
+							return f(g(x))
+						}
+					}
+				}).ap(u).ap(v)
+				
+				var composed = a.ap(u.ap(v))
+				
+				o(mapped()).equals(30)
+				o(mapped()).equals(composed())
+			})
+		})
+		o.spec("applicative", function() {
+			o("identity", function() {
+				var a = Stream.stream().of(function(value) {return value})
+				var v = Stream.stream(5)
+				
+				o(a.ap(v)()).equals(5)
+				o(a.ap(v)()).equals(v())
+			})
+			o("homomorphism", function() {
+				var a = Stream.stream(0)
+				var f = function(value) {return value * 2}
+				var x = 3
+				
+				o(a.of(f).ap(a.of(x))()).equals(6)
+				o(a.of(f).ap(a.of(x))()).equals(a.of(f(x))())
+			})
+			o("interchange", function() {
+				var u = Stream.stream(function(value) {return value * 2})
+				var a = Stream.stream()
+				var y = 3
+				
+				o(u.ap(a.of(y))()).equals(6)
+				o(u.ap(a.of(y))()).equals(a.of(function(f) {return f(y)}).ap(u)())
+			})
+		})
+	})
+})
\ No newline at end of file