diff --git a/examples/har_extractor.py b/examples/har_extractor.py
index 2a69b9afd..90412ec0f 100644
--- a/examples/har_extractor.py
+++ b/examples/har_extractor.py
@@ -2,7 +2,7 @@
     This inline script utilizes harparser.HAR from
     https://github.com/JustusW/harparser to generate a HAR log object.
 """
-import mitmproxy
+import mitmproxy.ctx
 import six
 import sys
 import pytz
@@ -221,9 +221,11 @@ def done():
     if context.dump_file == '-':
         mitmproxy.ctx.log(pprint.pformat(json.loads(json_dump)))
     elif context.dump_file.endswith('.zhar'):
-        file(context.dump_file, "w").write(compressed_json_dump)
+        with open(context.dump_file, "wb") as f:
+            f.write(compressed_json_dump)
     else:
-        file(context.dump_file, "w").write(json_dump)
+        with open(context.dump_file, "wb") as f:
+            f.write(json_dump)
     mitmproxy.ctx.log(
         "HAR log finished with %s bytes (%s bytes compressed)" % (
             len(json_dump), len(compressed_json_dump)
diff --git a/examples/stub.py b/examples/stub.py
index 10b342831..e5b4a39ab 100644
--- a/examples/stub.py
+++ b/examples/stub.py
@@ -6,11 +6,18 @@ import mitmproxy
 
 def start():
     """
-        Called once on script startup, before any other events.
+        Called once on script startup before any other events
     """
     mitmproxy.ctx.log("start")
 
 
+def configure(options):
+    """
+        Called once on script startup before any other events, and whenever options changes.
+    """
+    mitmproxy.ctx.log("configure")
+
+
 def clientconnect(root_layer):
     """
         Called when a client initiates a connection to the proxy. Note that a
diff --git a/mitmproxy/addons.py b/mitmproxy/addons.py
index 7ac65a09d..c779aaf8c 100644
--- a/mitmproxy/addons.py
+++ b/mitmproxy/addons.py
@@ -21,6 +21,7 @@ class Addons(object):
     def add(self, *addons):
         self.chain.extend(addons)
         for i in addons:
+            self.invoke_with_context(i, "start")
             self.invoke_with_context(i, "configure", self.master.options)
 
     def remove(self, addon):
diff --git a/mitmproxy/builtins/__init__.py b/mitmproxy/builtins/__init__.py
index 8021c20ff..6b357902a 100644
--- a/mitmproxy/builtins/__init__.py
+++ b/mitmproxy/builtins/__init__.py
@@ -4,6 +4,7 @@ from mitmproxy.builtins import anticache
 from mitmproxy.builtins import anticomp
 from mitmproxy.builtins import stickyauth
 from mitmproxy.builtins import stickycookie
+from mitmproxy.builtins import script
 from mitmproxy.builtins import stream
 
 
@@ -13,5 +14,6 @@ def default_addons():
         anticomp.AntiComp(),
         stickyauth.StickyAuth(),
         stickycookie.StickyCookie(),
+        script.ScriptLoader(),
         stream.Stream(),
     ]
diff --git a/mitmproxy/builtins/script.py b/mitmproxy/builtins/script.py
new file mode 100644
index 000000000..14f7dd5f2
--- /dev/null
+++ b/mitmproxy/builtins/script.py
@@ -0,0 +1,185 @@
+from __future__ import absolute_import, print_function, division
+
+import contextlib
+import os
+import shlex
+import sys
+import threading
+import traceback
+
+from mitmproxy import exceptions
+from mitmproxy import controller
+from mitmproxy import ctx
+
+
+import watchdog.events
+from watchdog.observers import polling
+
+
+def parse_command(command):
+    """
+        Returns a (path, args) tuple.
+    """
+    if not command or not command.strip():
+        raise exceptions.AddonError("Empty script command.")
+    # Windows: escape all backslashes in the path.
+    if os.name == "nt":  # pragma: no cover
+        backslashes = shlex.split(command, posix=False)[0].count("\\")
+        command = command.replace("\\", "\\\\", backslashes)
+    args = shlex.split(command)  # pragma: no cover
+    args[0] = os.path.expanduser(args[0])
+    if not os.path.exists(args[0]):
+        raise exceptions.AddonError(
+            ("Script file not found: %s.\r\n"
+             "If your script path contains spaces, "
+             "make sure to wrap it in additional quotes, e.g. -s \"'./foo bar/baz.py' --args\".") %
+            args[0])
+    elif os.path.isdir(args[0]):
+        raise exceptions.AddonError("Not a file: %s" % args[0])
+    return args[0], args[1:]
+
+
+@contextlib.contextmanager
+def scriptenv(path, args):
+    oldargs = sys.argv
+    sys.argv = [path] + args
+    script_dir = os.path.dirname(os.path.abspath(path))
+    sys.path.append(script_dir)
+    try:
+        yield
+    except Exception:
+        _, _, tb = sys.exc_info()
+        scriptdir = os.path.dirname(os.path.abspath(path))
+        for i, s in enumerate(reversed(traceback.extract_tb(tb))):
+            tb = tb.tb_next
+            if not os.path.abspath(s[0]).startswith(scriptdir):
+                break
+        ctx.log.error("Script error: %s" % "".join(traceback.format_tb(tb)))
+    finally:
+        sys.argv = oldargs
+        sys.path.pop()
+
+
+def load_script(path, args):
+    with open(path, "rb") as f:
+        try:
+            code = compile(f.read(), path, 'exec')
+        except SyntaxError as e:
+            ctx.log.error(
+                "Script error: %s line %s: %s" % (
+                    e.filename, e.lineno, e.msg
+                )
+            )
+            return
+    ns = {'__file__': os.path.abspath(path)}
+    with scriptenv(path, args):
+        exec(code, ns, ns)
+    return ns
+
+
+class ReloadHandler(watchdog.events.FileSystemEventHandler):
+    def __init__(self, callback):
+        self.callback = callback
+
+    def on_modified(self, event):
+        self.callback()
+
+    def on_created(self, event):
+        self.callback()
+
+
+class Script:
+    """
+        An addon that manages a single script.
+    """
+    def __init__(self, command):
+        self.name = command
+
+        self.command = command
+        self.path, self.args = parse_command(command)
+        self.ns = None
+        self.observer = None
+        self.dead = False
+
+        self.last_options = None
+        self.should_reload = threading.Event()
+
+        for i in controller.Events:
+            if not hasattr(self, i):
+                def mkprox():
+                    evt = i
+
+                    def prox(*args, **kwargs):
+                        self.run(evt, *args, **kwargs)
+                    return prox
+                setattr(self, i, mkprox())
+
+    def run(self, name, *args, **kwargs):
+        # It's possible for ns to be un-initialised if we failed during
+        # configure
+        if self.ns is not None and not self.dead:
+            func = self.ns.get(name)
+            if func:
+                with scriptenv(self.path, self.args):
+                    func(*args, **kwargs)
+
+    def reload(self):
+        self.should_reload.set()
+
+    def tick(self):
+        if self.should_reload.is_set():
+            self.should_reload.clear()
+            ctx.log.info("Reloading script: %s" % self.name)
+            self.ns = load_script(self.path, self.args)
+            self.configure(self.last_options)
+        else:
+            self.run("tick")
+
+    def start(self):
+        self.ns = load_script(self.path, self.args)
+        self.run("start")
+
+    def configure(self, options):
+        self.last_options = options
+        if not self.observer:
+            self.observer = polling.PollingObserver()
+            # Bind the handler to the real underlying master object
+            self.observer.schedule(
+                ReloadHandler(self.reload),
+                os.path.dirname(self.path) or "."
+            )
+            self.observer.start()
+        self.run("configure", options)
+
+    def done(self):
+        self.run("done")
+        self.dead = True
+
+
+class ScriptLoader():
+    """
+        An addon that manages loading scripts from options.
+    """
+    def configure(self, options):
+        for s in options.scripts:
+            if options.scripts.count(s) > 1:
+                raise exceptions.OptionsError("Duplicate script: %s" % s)
+
+        for a in ctx.master.addons.chain[:]:
+            if isinstance(a, Script) and a.name not in options.scripts:
+                    ctx.log.info("Un-loading script: %s" % a.name)
+                    ctx.master.addons.remove(a)
+
+        current = {}
+        for a in ctx.master.addons.chain[:]:
+            if isinstance(a, Script):
+                current[a.name] = a
+                ctx.master.addons.chain.remove(a)
+
+        for s in options.scripts:
+            if s in current:
+                ctx.master.addons.chain.append(current[s])
+            else:
+                ctx.log.info("Loading script: %s" % s)
+                sc = Script(s)
+                ctx.master.addons.add(sc)
diff --git a/mitmproxy/console/grideditor.py b/mitmproxy/console/grideditor.py
index 9fa51ccbe..f304de57a 100644
--- a/mitmproxy/console/grideditor.py
+++ b/mitmproxy/console/grideditor.py
@@ -6,11 +6,12 @@ import re
 
 import urwid
 
+from mitmproxy import exceptions
 from mitmproxy import filt
-from mitmproxy import script
-from mitmproxy import utils
+from mitmproxy.builtins import script
 from mitmproxy.console import common
 from mitmproxy.console import signals
+from netlib import strutils
 from netlib.http import cookies
 from netlib.http import user_agents
 
@@ -55,7 +56,7 @@ class TextColumn:
             o = editor.walker.get_current_value()
             if o is not None:
                 n = editor.master.spawn_editor(o.encode("string-escape"))
-                n = utils.clean_hanging_newline(n)
+                n = strutils.clean_hanging_newline(n)
                 editor.walker.set_current_value(n, False)
                 editor.walker._modified()
         elif key in ["enter"]:
@@ -643,8 +644,8 @@ class ScriptEditor(GridEditor):
 
     def is_error(self, col, val):
         try:
-            script.Script.parse_command(val)
-        except script.ScriptException as e:
+            script.parse_command(val)
+        except exceptions.AddonError as e:
             return str(e)
 
 
diff --git a/mitmproxy/console/master.py b/mitmproxy/console/master.py
index bc373a2b0..64bd9f0af 100644
--- a/mitmproxy/console/master.py
+++ b/mitmproxy/console/master.py
@@ -248,23 +248,6 @@ class ConsoleMaster(flow.FlowMaster):
         if options.server_replay:
             self.server_playback_path(options.server_replay)
 
-        if options.scripts:
-            for i in options.scripts:
-                try:
-                    self.load_script(i)
-                except exceptions.ScriptException as e:
-                    print("Script load error: {}".format(e), file=sys.stderr)
-                    sys.exit(1)
-
-        if options.outfile:
-            err = self.start_stream_to_path(
-                options.outfile[0],
-                options.outfile[1]
-            )
-            if err:
-                print("Stream file error: {}".format(err), file=sys.stderr)
-                sys.exit(1)
-
         self.view_stack = []
 
         if options.app:
@@ -685,20 +668,7 @@ class ConsoleMaster(flow.FlowMaster):
         self.refresh_focus()
 
     def edit_scripts(self, scripts):
-        commands = [x[0] for x in scripts]  # remove outer array
-        if commands == [s.command for s in self.scripts]:
-            return
-
-        self.unload_scripts()
-        for command in commands:
-            try:
-                self.load_script(command)
-            except exceptions.ScriptException as e:
-                signals.status_message.send(
-                    message='Error loading "{}".'.format(command)
-                )
-                signals.add_event('Error loading "{}":\n{}'.format(command, e), "error")
-        signals.update_settings.send(self)
+        self.options.scripts = [x[0] for x in scripts]
 
     def stop_client_playback_prompt(self, a):
         if a != "n":
diff --git a/mitmproxy/console/options.py b/mitmproxy/console/options.py
index d363ba747..d8824b056 100644
--- a/mitmproxy/console/options.py
+++ b/mitmproxy/console/options.py
@@ -54,7 +54,7 @@ class Options(urwid.WidgetWrap):
                 select.Option(
                     "Scripts",
                     "S",
-                    lambda: master.scripts,
+                    lambda: master.options.scripts,
                     self.scripts
                 ),
 
@@ -160,12 +160,14 @@ class Options(urwid.WidgetWrap):
         self.master.replacehooks.clear()
         self.master.set_ignore_filter([])
         self.master.set_tcp_filter([])
-        self.master.scripts = []
 
-        self.master.options.anticache = False
-        self.master.options.anticomp = False
-        self.master.options.stickyauth = None
-        self.master.options.stickycookie = None
+        self.master.options.update(
+            scripts = [],
+            anticache = False,
+            anticomp = False,
+            stickyauth = None,
+            stickycookie = None
+        )
 
         self.master.state.default_body_view = contentviews.get("Auto")
 
@@ -234,7 +236,7 @@ class Options(urwid.WidgetWrap):
         self.master.view_grideditor(
             grideditor.ScriptEditor(
                 self.master,
-                [[i.command] for i in self.master.scripts],
+                [[i] for i in self.master.options.scripts],
                 self.master.edit_scripts
             )
         )
diff --git a/mitmproxy/console/statusbar.py b/mitmproxy/console/statusbar.py
index fc41869c3..e7a700a6e 100644
--- a/mitmproxy/console/statusbar.py
+++ b/mitmproxy/console/statusbar.py
@@ -218,14 +218,13 @@ class StatusBar(urwid.WidgetWrap):
                 dst.address.host,
                 dst.address.port
             ))
-        if self.master.scripts:
+        if self.master.options.scripts:
             r.append("[")
             r.append(("heading_key", "s"))
-            r.append("cripts:%s]" % len(self.master.scripts))
-        # r.append("[lt:%0.3f]"%self.master.looptime)
+            r.append("cripts:%s]" % len(self.master.options.scripts))
 
-        if self.master.stream:
-            r.append("[W:%s]" % self.master.stream_path)
+        if self.master.options.outfile:
+            r.append("[W:%s]" % self.master.outfile[0])
 
         return r
 
diff --git a/mitmproxy/controller.py b/mitmproxy/controller.py
index 2f0c8bf29..503cdcd3c 100644
--- a/mitmproxy/controller.py
+++ b/mitmproxy/controller.py
@@ -33,6 +33,11 @@ Events = frozenset([
     "error",
     "log",
 
+    "start",
+    "configure",
+    "done",
+    "tick",
+
     "script_change",
 ])
 
@@ -44,7 +49,17 @@ class Log(object):
     def __call__(self, text, level="info"):
         self.master.add_event(text, level)
 
-    # We may want to add .log(), .warn() etc. here at a later point in time
+    def debug(self, txt):
+        self(txt, "debug")
+
+    def info(self, txt):
+        self(txt, "info")
+
+    def warn(self, txt):
+        self(txt, "warn")
+
+    def error(self, txt):
+        self(txt, "error")
 
 
 class Master(object):
@@ -97,26 +112,25 @@ class Master(object):
             self.shutdown()
 
     def tick(self, timeout):
+        with self.handlecontext():
+            self.addons("tick")
         changed = False
         try:
-            # This endless loop runs until the 'Queue.Empty'
-            # exception is thrown.
-            while True:
-                mtype, obj = self.event_queue.get(timeout=timeout)
-                if mtype not in Events:
-                    raise exceptions.ControlException("Unknown event %s" % repr(mtype))
-                handle_func = getattr(self, mtype)
-                if not callable(handle_func):
-                    raise exceptions.ControlException("Handler %s not callable" % mtype)
-                if not handle_func.__dict__.get("__handler"):
-                    raise exceptions.ControlException(
-                        "Handler function %s is not decorated with controller.handler" % (
-                            handle_func
-                        )
+            mtype, obj = self.event_queue.get(timeout=timeout)
+            if mtype not in Events:
+                raise exceptions.ControlException("Unknown event %s" % repr(mtype))
+            handle_func = getattr(self, mtype)
+            if not callable(handle_func):
+                raise exceptions.ControlException("Handler %s not callable" % mtype)
+            if not handle_func.__dict__.get("__handler"):
+                raise exceptions.ControlException(
+                    "Handler function %s is not decorated with controller.handler" % (
+                        handle_func
                     )
-                handle_func(obj)
-                self.event_queue.task_done()
-                changed = True
+                )
+            handle_func(obj)
+            self.event_queue.task_done()
+            changed = True
         except queue.Empty:
             pass
         return changed
diff --git a/mitmproxy/dump.py b/mitmproxy/dump.py
index 274e01f35..999a709ae 100644
--- a/mitmproxy/dump.py
+++ b/mitmproxy/dump.py
@@ -93,13 +93,6 @@ class DumpMaster(flow.FlowMaster):
                 not options.keepserving
             )
 
-        scripts = options.scripts or []
-        for command in scripts:
-            try:
-                self.load_script(command, use_reloader=True)
-            except exceptions.ScriptException as e:
-                raise DumpError(str(e))
-
         if options.rfile:
             try:
                 self.load_flows_file(options.rfile)
@@ -335,6 +328,5 @@ class DumpMaster(flow.FlowMaster):
 
     def run(self):  # pragma: no cover
         if self.options.rfile and not self.options.keepserving:
-            self.unload_scripts()  # make sure to trigger script unload events.
             return
         super(DumpMaster, self).run()
diff --git a/mitmproxy/exceptions.py b/mitmproxy/exceptions.py
index 282784b6d..3b41fe1ca 100644
--- a/mitmproxy/exceptions.py
+++ b/mitmproxy/exceptions.py
@@ -99,3 +99,7 @@ class ControlException(ProxyException):
 
 class OptionsError(Exception):
     pass
+
+
+class AddonError(Exception):
+    pass
diff --git a/mitmproxy/flow/master.py b/mitmproxy/flow/master.py
index 27ceee87b..aa09e1097 100644
--- a/mitmproxy/flow/master.py
+++ b/mitmproxy/flow/master.py
@@ -9,7 +9,6 @@ import netlib.exceptions
 from mitmproxy import controller
 from mitmproxy import exceptions
 from mitmproxy import models
-from mitmproxy import script
 from mitmproxy.flow import io
 from mitmproxy.flow import modules
 from mitmproxy.onboarding import app
@@ -35,8 +34,6 @@ class FlowMaster(controller.Master):
         self.server_playback = None  # type: Optional[modules.ServerPlaybackState]
         self.client_playback = None  # type: Optional[modules.ClientPlaybackState]
         self.kill_nonreplay = False
-        self.scripts = []  # type: List[script.Script]
-        self.pause_scripts = False
 
         self.stream_large_bodies = None  # type: Optional[modules.StreamLargeBodies]
         self.refresh_server_playback = False
@@ -60,44 +57,6 @@ class FlowMaster(controller.Master):
             level: debug, info, error
         """
 
-    def unload_scripts(self):
-        for s in self.scripts[:]:
-            self.unload_script(s)
-
-    def unload_script(self, script_obj):
-        try:
-            script_obj.unload()
-        except script.ScriptException as e:
-            self.add_event("Script error:\n" + str(e), "error")
-        script.reloader.unwatch(script_obj)
-        self.scripts.remove(script_obj)
-
-    def load_script(self, command, use_reloader=False):
-        """
-            Loads a script.
-
-            Raises:
-                ScriptException
-        """
-        s = script.Script(command)
-        s.load()
-        if use_reloader:
-            s.reply = controller.DummyReply()
-            script.reloader.watch(s, lambda: self.event_queue.put(("script_change", s)))
-        self.scripts.append(s)
-
-    def _run_single_script_hook(self, script_obj, name, *args, **kwargs):
-        if script_obj and not self.pause_scripts:
-            try:
-                script_obj.run(name, *args, **kwargs)
-            except script.ScriptException as e:
-                self.add_event("Script error:\n{}".format(e), "error")
-
-    def run_scripts(self, name, msg):
-        for script_obj in self.scripts:
-            if not msg.reply.acked:
-                self._run_single_script_hook(script_obj, name, msg)
-
     def get_ignore_filter(self):
         return self.server.config.check_ignore.patterns
 
@@ -298,11 +257,11 @@ class FlowMaster(controller.Master):
             if not pb and self.kill_nonreplay:
                 f.kill(self)
 
-    def replay_request(self, f, block=False, run_scripthooks=True):
+    def replay_request(self, f, block=False):
         """
             Returns None if successful, or error message if not.
         """
-        if f.live and run_scripthooks:
+        if f.live:
             return "Can't replay live request."
         if f.intercepted:
             return "Can't replay while intercepting..."
@@ -319,7 +278,7 @@ class FlowMaster(controller.Master):
             rt = http_replay.RequestReplayThread(
                 self.server.config,
                 f,
-                self.event_queue if run_scripthooks else False,
+                self.event_queue,
                 self.should_exit
             )
             rt.start()  # pragma: no cover
@@ -332,28 +291,27 @@ class FlowMaster(controller.Master):
 
     @controller.handler
     def clientconnect(self, root_layer):
-        self.run_scripts("clientconnect", root_layer)
+        pass
 
     @controller.handler
     def clientdisconnect(self, root_layer):
-        self.run_scripts("clientdisconnect", root_layer)
+        pass
 
     @controller.handler
     def serverconnect(self, server_conn):
-        self.run_scripts("serverconnect", server_conn)
+        pass
 
     @controller.handler
     def serverdisconnect(self, server_conn):
-        self.run_scripts("serverdisconnect", server_conn)
+        pass
 
     @controller.handler
     def next_layer(self, top_layer):
-        self.run_scripts("next_layer", top_layer)
+        pass
 
     @controller.handler
     def error(self, f):
         self.state.update_flow(f)
-        self.run_scripts("error", f)
         if self.client_playback:
             self.client_playback.clear(f)
         return f
@@ -381,8 +339,6 @@ class FlowMaster(controller.Master):
             self.setheaders.run(f)
         if not f.reply.acked:
             self.process_new_request(f)
-        if not f.reply.acked:
-            self.run_scripts("request", f)
         return f
 
     @controller.handler
@@ -393,7 +349,6 @@ class FlowMaster(controller.Master):
         except netlib.exceptions.HttpException:
             f.reply.kill()
             return
-        self.run_scripts("responseheaders", f)
         return f
 
     @controller.handler
@@ -404,7 +359,6 @@ class FlowMaster(controller.Master):
             self.replacehooks.run(f)
         if not f.reply.acked:
             self.setheaders.run(f)
-        self.run_scripts("response", f)
         if not f.reply.acked:
             if self.client_playback:
                 self.client_playback.clear(f)
@@ -416,46 +370,15 @@ class FlowMaster(controller.Master):
     def handle_accept_intercept(self, f):
         self.state.update_flow(f)
 
-    @controller.handler
-    def script_change(self, s):
-        """
-        Handle a script whose contents have been changed on the file system.
-
-        Args:
-            s (script.Script): the changed script
-
-        Returns:
-            True, if reloading was successful.
-            False, otherwise.
-        """
-        ok = True
-        # We deliberately do not want to fail here.
-        # In the worst case, we have an "empty" script object.
-        try:
-            s.unload()
-        except script.ScriptException as e:
-            ok = False
-            self.add_event('Error reloading "{}":\n{}'.format(s.path, e), 'error')
-        try:
-            s.load()
-        except script.ScriptException as e:
-            ok = False
-            self.add_event('Error reloading "{}":\n{}'.format(s.path, e), 'error')
-        else:
-            self.add_event('"{}" reloaded.'.format(s.path), 'info')
-        return ok
-
     @controller.handler
     def tcp_open(self, flow):
         # TODO: This would break mitmproxy currently.
         # self.state.add_flow(flow)
         self.active_flows.add(flow)
-        self.run_scripts("tcp_open", flow)
 
     @controller.handler
     def tcp_message(self, flow):
-        # type: (TCPFlow) -> None
-        self.run_scripts("tcp_message", flow)
+        pass
 
     @controller.handler
     def tcp_error(self, flow):
@@ -463,13 +386,7 @@ class FlowMaster(controller.Master):
             repr(flow.server_conn.address),
             flow.error
         ), "info")
-        self.run_scripts("tcp_error", flow)
 
     @controller.handler
     def tcp_close(self, flow):
         self.active_flows.discard(flow)
-        self.run_scripts("tcp_close", flow)
-
-    def shutdown(self):
-        super(FlowMaster, self).shutdown()
-        self.unload_scripts()
diff --git a/mitmproxy/script/__init__.py b/mitmproxy/script/__init__.py
index 9a3985ab8..e75f282ae 100644
--- a/mitmproxy/script/__init__.py
+++ b/mitmproxy/script/__init__.py
@@ -1,11 +1,5 @@
-from . import reloader
 from .concurrent import concurrent
-from .script import Script
-from ..exceptions import ScriptException
 
 __all__ = [
-    "Script",
     "concurrent",
-    "ScriptException",
-    "reloader"
 ]
diff --git a/mitmproxy/script/concurrent.py b/mitmproxy/script/concurrent.py
index 010a5fa09..0cc0514e7 100644
--- a/mitmproxy/script/concurrent.py
+++ b/mitmproxy/script/concurrent.py
@@ -13,7 +13,7 @@ class ScriptThread(basethread.BaseThread):
 
 
 def concurrent(fn):
-    if fn.__name__ not in controller.Events:
+    if fn.__name__ not in controller.Events - set(["start", "configure", "tick"]):
         raise NotImplementedError(
             "Concurrent decorator not supported for '%s' method." % fn.__name__
         )
diff --git a/mitmproxy/script/reloader.py b/mitmproxy/script/reloader.py
deleted file mode 100644
index 857d76cd5..000000000
--- a/mitmproxy/script/reloader.py
+++ /dev/null
@@ -1,47 +0,0 @@
-from __future__ import absolute_import, print_function, division
-
-import os
-
-from watchdog.events import RegexMatchingEventHandler
-
-from watchdog.observers.polling import PollingObserver as Observer
-# We occasionally have watchdog errors on Windows, Linux and Mac when using the native observers.
-# After reading through the watchdog source code and issue tracker,
-# we may want to replace this with a very simple implementation of our own.
-
-_observers = {}
-
-
-def watch(script, callback):
-    if script in _observers:
-        raise RuntimeError("Script already observed")
-    script_dir = os.path.dirname(os.path.abspath(script.path))
-    script_name = os.path.basename(script.path)
-    event_handler = _ScriptModificationHandler(callback, filename=script_name)
-    observer = Observer()
-    observer.schedule(event_handler, script_dir)
-    observer.start()
-    _observers[script] = observer
-
-
-def unwatch(script):
-    observer = _observers.pop(script, None)
-    if observer:
-        observer.stop()
-        observer.join()
-
-
-class _ScriptModificationHandler(RegexMatchingEventHandler):
-
-    def __init__(self, callback, filename='.*'):
-
-        super(_ScriptModificationHandler, self).__init__(
-            ignore_directories=True,
-            regexes=['.*' + filename]
-        )
-        self.callback = callback
-
-    def on_modified(self, event):
-        self.callback()
-
-__all__ = ["watch", "unwatch"]
diff --git a/mitmproxy/script/script.py b/mitmproxy/script/script.py
deleted file mode 100644
index db4909cab..000000000
--- a/mitmproxy/script/script.py
+++ /dev/null
@@ -1,136 +0,0 @@
-"""
-The script object representing mitmproxy inline scripts.
-Script objects know nothing about mitmproxy or mitmproxy's API - this knowledge is provided
-by the mitmproxy-specific ScriptContext.
-"""
-# Do not import __future__ here, this would apply transitively to the inline scripts.
-from __future__ import absolute_import, print_function, division
-
-import os
-import shlex
-import sys
-import contextlib
-
-import six
-from typing import List  # noqa
-
-from mitmproxy import exceptions
-
-
-@contextlib.contextmanager
-def scriptenv(path, args):
-    # type: (str, List[str]) -> None
-    oldargs = sys.argv
-    script_dir = os.path.dirname(os.path.abspath(path))
-
-    sys.argv = [path] + args
-    sys.path.append(script_dir)
-    try:
-        yield
-    finally:
-        sys.argv = oldargs
-        sys.path.pop()
-
-
-class Script(object):
-    """
-    Script object representing an inline script.
-    """
-
-    def __init__(self, command):
-        self.command = command
-        self.path, self.args = self.parse_command(command)
-        self.ns = None
-
-    def __enter__(self):
-        self.load()
-        return self
-
-    def __exit__(self, exc_type, exc_val, exc_tb):
-        if exc_val:
-            return False  # re-raise the exception
-        self.unload()
-
-    @staticmethod
-    def parse_command(command):
-        # type: (str) -> Tuple[str,List[str]]
-        """
-            Returns a (path, args) tuple.
-        """
-        if not command or not command.strip():
-            raise exceptions.ScriptException("Empty script command.")
-        # Windows: escape all backslashes in the path.
-        if os.name == "nt":  # pragma: no cover
-            backslashes = shlex.split(command, posix=False)[0].count("\\")
-            command = command.replace("\\", "\\\\", backslashes)
-        args = shlex.split(command)  # pragma: no cover
-        args[0] = os.path.expanduser(args[0])
-        if not os.path.exists(args[0]):
-            raise exceptions.ScriptException(
-                ("Script file not found: %s.\r\n"
-                 "If your script path contains spaces, "
-                 "make sure to wrap it in additional quotes, e.g. -s \"'./foo bar/baz.py' --args\".") %
-                args[0])
-        elif os.path.isdir(args[0]):
-            raise exceptions.ScriptException("Not a file: %s" % args[0])
-        return args[0], args[1:]
-
-    def load(self):
-        """
-            Loads an inline script.
-
-            Returns:
-                The return value of self.run("start", ...)
-
-            Raises:
-                ScriptException on failure
-        """
-        if self.ns is not None:
-            raise exceptions.ScriptException("Script is already loaded")
-        self.ns = {'__file__': os.path.abspath(self.path)}
-
-        with scriptenv(self.path, self.args):
-            try:
-                with open(self.path) as f:
-                    code = compile(f.read(), self.path, 'exec')
-                    exec(code, self.ns, self.ns)
-            except Exception:
-                six.reraise(
-                    exceptions.ScriptException,
-                    exceptions.ScriptException.from_exception_context(),
-                    sys.exc_info()[2]
-                )
-        return self.run("start")
-
-    def unload(self):
-        try:
-            return self.run("done")
-        finally:
-            self.ns = None
-
-    def run(self, name, *args, **kwargs):
-        """
-            Runs an inline script hook.
-
-            Returns:
-                The return value of the method.
-                None, if the script does not provide the method.
-
-            Raises:
-                ScriptException if there was an exception.
-        """
-        if self.ns is None:
-            raise exceptions.ScriptException("Script not loaded.")
-        f = self.ns.get(name)
-        if f:
-            try:
-                with scriptenv(self.path, self.args):
-                    return f(*args, **kwargs)
-            except Exception:
-                six.reraise(
-                    exceptions.ScriptException,
-                    exceptions.ScriptException.from_exception_context(),
-                    sys.exc_info()[2]
-                )
-        else:
-            return None
diff --git a/netlib/utils.py b/netlib/utils.py
index 23c16dc36..9eebf22cb 100644
--- a/netlib/utils.py
+++ b/netlib/utils.py
@@ -56,6 +56,13 @@ class Data(object):
         dirname = os.path.dirname(inspect.getsourcefile(m))
         self.dirname = os.path.abspath(dirname)
 
+    def push(self, subpath):
+        """
+            Change the data object to a path relative to the module.
+        """
+        self.dirname = os.path.join(self.dirname, subpath)
+        return self
+
     def path(self, path):
         """
             Returns a path to the package data housed at 'path' under this
diff --git a/test/mitmproxy/builtins/test_script.py b/test/mitmproxy/builtins/test_script.py
new file mode 100644
index 000000000..da60b64cd
--- /dev/null
+++ b/test/mitmproxy/builtins/test_script.py
@@ -0,0 +1,187 @@
+import time
+
+from mitmproxy.builtins import script
+from mitmproxy import exceptions
+from mitmproxy.flow import master
+from mitmproxy.flow import state
+from mitmproxy.flow import options
+
+from .. import tutils, mastertest
+
+
+class TestParseCommand:
+    def test_empty_command(self):
+        with tutils.raises(exceptions.AddonError):
+            script.parse_command("")
+
+        with tutils.raises(exceptions.AddonError):
+            script.parse_command("  ")
+
+    def test_no_script_file(self):
+        with tutils.raises("not found"):
+            script.parse_command("notfound")
+
+        with tutils.tmpdir() as dir:
+            with tutils.raises("not a file"):
+                script.parse_command(dir)
+
+    def test_parse_args(self):
+        with tutils.chdir(tutils.test_data.dirname):
+            assert script.parse_command("data/scripts/a.py") == ("data/scripts/a.py", [])
+            assert script.parse_command("data/scripts/a.py foo bar") == ("data/scripts/a.py", ["foo", "bar"])
+            assert script.parse_command("data/scripts/a.py 'foo bar'") == ("data/scripts/a.py", ["foo bar"])
+
+    @tutils.skip_not_windows
+    def test_parse_windows(self):
+        with tutils.chdir(tutils.test_data.dirname):
+            assert script.parse_command("data\\scripts\\a.py") == ("data\\scripts\\a.py", [])
+            assert script.parse_command("data\\scripts\\a.py 'foo \\ bar'") == ("data\\scripts\\a.py", ['foo \\ bar'])
+
+
+def test_load_script():
+    ns = script.load_script(
+        tutils.test_data.path(
+            "data/addonscripts/recorder.py"
+        ), []
+    )
+    assert ns["configure"]
+
+
+class TestScript(mastertest.MasterTest):
+    def test_simple(self):
+        s = state.State()
+        m = master.FlowMaster(options.Options(), None, s)
+        sc = script.Script(
+            tutils.test_data.path(
+                "data/addonscripts/recorder.py"
+            )
+        )
+        m.addons.add(sc)
+        assert sc.ns["call_log"] == [
+            ("solo", "start", (), {}),
+            ("solo", "configure", (options.Options(),), {})
+        ]
+
+        sc.ns["call_log"] = []
+        f = tutils.tflow(resp=True)
+        self.invoke(m, "request", f)
+
+        recf = sc.ns["call_log"][0]
+        assert recf[1] == "request"
+
+    def test_reload(self):
+        s = state.State()
+        m = mastertest.RecordingMaster(options.Options(), None, s)
+        with tutils.tmpdir():
+            with open("foo.py", "w"):
+                pass
+            sc = script.Script("foo.py")
+            m.addons.add(sc)
+
+            for _ in range(100):
+                with open("foo.py", "a") as f:
+                    f.write(".")
+                m.addons.invoke_with_context(sc, "tick")
+                time.sleep(0.1)
+                if m.event_log:
+                    return
+            raise AssertionError("Change event not detected.")
+
+    def test_exception(self):
+        s = state.State()
+        m = mastertest.RecordingMaster(options.Options(), None, s)
+        sc = script.Script(
+            tutils.test_data.path("data/addonscripts/error.py")
+        )
+        m.addons.add(sc)
+        f = tutils.tflow(resp=True)
+        self.invoke(m, "request", f)
+        assert m.event_log[0][0] == "error"
+
+    def test_duplicate_flow(self):
+        s = state.State()
+        fm = master.FlowMaster(None, None, s)
+        fm.addons.add(
+            script.Script(
+                tutils.test_data.path("data/addonscripts/duplicate_flow.py")
+            )
+        )
+        f = tutils.tflow()
+        fm.request(f)
+        assert fm.state.flow_count() == 2
+        assert not fm.state.view[0].request.is_replay
+        assert fm.state.view[1].request.is_replay
+
+
+class TestScriptLoader(mastertest.MasterTest):
+    def test_simple(self):
+        s = state.State()
+        o = options.Options(scripts=[])
+        m = master.FlowMaster(o, None, s)
+        sc = script.ScriptLoader()
+        m.addons.add(sc)
+        assert len(m.addons) == 1
+        o.update(
+            scripts = [
+                tutils.test_data.path("data/addonscripts/recorder.py")
+            ]
+        )
+        assert len(m.addons) == 2
+        o.update(scripts = [])
+        assert len(m.addons) == 1
+
+    def test_dupes(self):
+        s = state.State()
+        o = options.Options(scripts=["one", "one"])
+        m = master.FlowMaster(o, None, s)
+        sc = script.ScriptLoader()
+        tutils.raises(exceptions.OptionsError, m.addons.add, sc)
+
+    def test_order(self):
+        rec = tutils.test_data.path("data/addonscripts/recorder.py")
+
+        s = state.State()
+        o = options.Options(
+            scripts = [
+                "%s %s" % (rec, "a"),
+                "%s %s" % (rec, "b"),
+                "%s %s" % (rec, "c"),
+            ]
+        )
+        m = mastertest.RecordingMaster(o, None, s)
+        sc = script.ScriptLoader()
+        m.addons.add(sc)
+
+        debug = [(i[0], i[1]) for i in m.event_log if i[0] == "debug"]
+        assert debug == [
+            ('debug', 'a start'), ('debug', 'a configure'),
+            ('debug', 'b start'), ('debug', 'b configure'),
+            ('debug', 'c start'), ('debug', 'c configure')
+        ]
+        m.event_log[:] = []
+
+        o.scripts = [
+            "%s %s" % (rec, "c"),
+            "%s %s" % (rec, "a"),
+            "%s %s" % (rec, "b"),
+        ]
+        debug = [(i[0], i[1]) for i in m.event_log if i[0] == "debug"]
+        assert debug == [
+            ('debug', 'c configure'),
+            ('debug', 'a configure'),
+            ('debug', 'b configure'),
+        ]
+        m.event_log[:] = []
+
+        o.scripts = [
+            "%s %s" % (rec, "x"),
+            "%s %s" % (rec, "a"),
+        ]
+        debug = [(i[0], i[1]) for i in m.event_log if i[0] == "debug"]
+        assert debug == [
+            ('debug', 'c done'),
+            ('debug', 'b done'),
+            ('debug', 'x start'),
+            ('debug', 'x configure'),
+            ('debug', 'a configure'),
+        ]
diff --git a/test/mitmproxy/data/scripts/concurrent_decorator.py b/test/mitmproxy/data/addonscripts/concurrent_decorator.py
similarity index 99%
rename from test/mitmproxy/data/scripts/concurrent_decorator.py
rename to test/mitmproxy/data/addonscripts/concurrent_decorator.py
index 162c00f4b..a56c2af1c 100644
--- a/test/mitmproxy/data/scripts/concurrent_decorator.py
+++ b/test/mitmproxy/data/addonscripts/concurrent_decorator.py
@@ -1,7 +1,6 @@
 import time
 from mitmproxy.script import concurrent
 
-
 @concurrent
 def request(flow):
     time.sleep(0.1)
diff --git a/test/mitmproxy/data/scripts/concurrent_decorator_err.py b/test/mitmproxy/data/addonscripts/concurrent_decorator_err.py
similarity index 100%
rename from test/mitmproxy/data/scripts/concurrent_decorator_err.py
rename to test/mitmproxy/data/addonscripts/concurrent_decorator_err.py
diff --git a/test/mitmproxy/data/addonscripts/duplicate_flow.py b/test/mitmproxy/data/addonscripts/duplicate_flow.py
new file mode 100644
index 000000000..b466423cd
--- /dev/null
+++ b/test/mitmproxy/data/addonscripts/duplicate_flow.py
@@ -0,0 +1,6 @@
+from mitmproxy import ctx
+
+
+def request(flow):
+    f = ctx.master.duplicate_flow(flow)
+    ctx.master.replay_request(f, block=True)
diff --git a/test/mitmproxy/data/addonscripts/error.py b/test/mitmproxy/data/addonscripts/error.py
new file mode 100644
index 000000000..8ece9fcea
--- /dev/null
+++ b/test/mitmproxy/data/addonscripts/error.py
@@ -0,0 +1,7 @@
+
+def mkerr():
+    raise ValueError("Error!")
+
+
+def request(flow):
+    mkerr()
diff --git a/test/mitmproxy/data/addonscripts/recorder.py b/test/mitmproxy/data/addonscripts/recorder.py
new file mode 100644
index 000000000..b6ac8d89d
--- /dev/null
+++ b/test/mitmproxy/data/addonscripts/recorder.py
@@ -0,0 +1,25 @@
+from mitmproxy import controller
+from mitmproxy import ctx
+import sys
+
+call_log = []
+
+if len(sys.argv) > 1:
+    name = sys.argv[1]
+else:
+    name = "solo"
+
+# Keep a log of all possible event calls
+evts = list(controller.Events) + ["configure"]
+for i in evts:
+    def mkprox():
+        evt = i
+
+        def prox(*args, **kwargs):
+            lg = (name, evt, args, kwargs)
+            if evt != "log":
+                ctx.log.info(str(lg))
+            call_log.append(lg)
+            ctx.log.debug("%s %s" % (name, evt))
+        return prox
+    globals()[i] = mkprox()
diff --git a/test/mitmproxy/data/addonscripts/stream_modify.py b/test/mitmproxy/data/addonscripts/stream_modify.py
new file mode 100644
index 000000000..bc6163421
--- /dev/null
+++ b/test/mitmproxy/data/addonscripts/stream_modify.py
@@ -0,0 +1,8 @@
+
+def modify(chunks):
+    for chunk in chunks:
+        yield chunk.replace(b"foo", b"bar")
+
+
+def responseheaders(flow):
+    flow.response.stream = modify
diff --git a/test/mitmproxy/data/addonscripts/tcp_stream_modify.py b/test/mitmproxy/data/addonscripts/tcp_stream_modify.py
new file mode 100644
index 000000000..af4ccf7e1
--- /dev/null
+++ b/test/mitmproxy/data/addonscripts/tcp_stream_modify.py
@@ -0,0 +1,5 @@
+
+def tcp_message(flow):
+    message = flow.messages[-1]
+    if not message.from_client:
+        message.content = message.content.replace(b"foo", b"bar")
diff --git a/test/mitmproxy/mastertest.py b/test/mitmproxy/mastertest.py
index 9754d3a99..240f6a730 100644
--- a/test/mitmproxy/mastertest.py
+++ b/test/mitmproxy/mastertest.py
@@ -3,6 +3,7 @@ import mock
 from . import tutils
 import netlib.tutils
 
+from mitmproxy.flow import master
 from mitmproxy import flow, proxy, models, controller
 
 
@@ -39,3 +40,12 @@ class MasterTest:
         t = tutils.tflow(resp=True)
         fw.add(t)
         f.close()
+
+
+class RecordingMaster(master.FlowMaster):
+    def __init__(self, *args, **kwargs):
+        master.FlowMaster.__init__(self, *args, **kwargs)
+        self.event_log = []
+
+    def add_event(self, e, level):
+        self.event_log.append((level, e))
diff --git a/test/mitmproxy/script/test_concurrent.py b/test/mitmproxy/script/test_concurrent.py
index 57eeca191..080746e89 100644
--- a/test/mitmproxy/script/test_concurrent.py
+++ b/test/mitmproxy/script/test_concurrent.py
@@ -1,28 +1,46 @@
-from mitmproxy.script import Script
-from test.mitmproxy import tutils
+from test.mitmproxy import tutils, mastertest
 from mitmproxy import controller
+from mitmproxy.builtins import script
+from mitmproxy import options
+from mitmproxy.flow import master
+from mitmproxy.flow import state
 import time
 
 
 class Thing:
     def __init__(self):
         self.reply = controller.DummyReply()
+        self.live = True
 
 
-@tutils.skip_appveyor
-def test_concurrent():
-    with Script(tutils.test_data.path("data/scripts/concurrent_decorator.py")) as s:
-        f1, f2 = Thing(), Thing()
-        s.run("request", f1)
-        s.run("request", f2)
+class TestConcurrent(mastertest.MasterTest):
+    @tutils.skip_appveyor
+    def test_concurrent(self):
+        s = state.State()
+        m = master.FlowMaster(options.Options(), None, s)
+        sc = script.Script(
+            tutils.test_data.path(
+                "data/addonscripts/concurrent_decorator.py"
+            )
+        )
+        m.addons.add(sc)
+        f1, f2 = tutils.tflow(), tutils.tflow()
+        self.invoke(m, "request", f1)
+        self.invoke(m, "request", f2)
         start = time.time()
         while time.time() - start < 5:
             if f1.reply.acked and f2.reply.acked:
                 return
         raise ValueError("Script never acked")
 
-
-def test_concurrent_err():
-    s = Script(tutils.test_data.path("data/scripts/concurrent_decorator_err.py"))
-    with tutils.raises("Concurrent decorator not supported for 'start' method"):
-        s.load()
+    def test_concurrent_err(self):
+        s = state.State()
+        m = mastertest.RecordingMaster(options.Options(), None, s)
+        sc = script.Script(
+            tutils.test_data.path(
+                "data/addonscripts/concurrent_decorator_err.py"
+            )
+        )
+        with m.handlecontext():
+            sc.start()
+        assert "decorator not supported" in m.event_log[0][1]
diff --git a/test/mitmproxy/script/test_reloader.py b/test/mitmproxy/script/test_reloader.py
deleted file mode 100644
index e33903b95..000000000
--- a/test/mitmproxy/script/test_reloader.py
+++ /dev/null
@@ -1,34 +0,0 @@
-import mock
-from mitmproxy.script.reloader import watch, unwatch
-from test.mitmproxy import tutils
-from threading import Event
-
-
-def test_simple():
-    with tutils.tmpdir():
-        with open("foo.py", "w"):
-            pass
-
-        script = mock.Mock()
-        script.path = "foo.py"
-
-        e = Event()
-
-        def _onchange():
-            e.set()
-
-        watch(script, _onchange)
-        with tutils.raises("already observed"):
-            watch(script, _onchange)
-
-        # Some reloaders don't register a change directly after watching, because they first need to initialize.
-        # To test if watching works at all, we do repeated writes every 100ms.
-        for _ in range(100):
-            with open("foo.py", "a") as f:
-                f.write(".")
-            if e.wait(0.1):
-                break
-        else:
-            raise AssertionError("No change detected.")
-
-        unwatch(script)
diff --git a/test/mitmproxy/script/test_script.py b/test/mitmproxy/script/test_script.py
deleted file mode 100644
index 48fe65c95..000000000
--- a/test/mitmproxy/script/test_script.py
+++ /dev/null
@@ -1,83 +0,0 @@
-from mitmproxy.script import Script
-from mitmproxy.exceptions import ScriptException
-from test.mitmproxy import tutils
-
-
-class TestParseCommand:
-    def test_empty_command(self):
-        with tutils.raises(ScriptException):
-            Script.parse_command("")
-
-        with tutils.raises(ScriptException):
-            Script.parse_command("  ")
-
-    def test_no_script_file(self):
-        with tutils.raises("not found"):
-            Script.parse_command("notfound")
-
-        with tutils.tmpdir() as dir:
-            with tutils.raises("not a file"):
-                Script.parse_command(dir)
-
-    def test_parse_args(self):
-        with tutils.chdir(tutils.test_data.dirname):
-            assert Script.parse_command("data/scripts/a.py") == ("data/scripts/a.py", [])
-            assert Script.parse_command("data/scripts/a.py foo bar") == ("data/scripts/a.py", ["foo", "bar"])
-            assert Script.parse_command("data/scripts/a.py 'foo bar'") == ("data/scripts/a.py", ["foo bar"])
-
-    @tutils.skip_not_windows
-    def test_parse_windows(self):
-        with tutils.chdir(tutils.test_data.dirname):
-            assert Script.parse_command("data\\scripts\\a.py") == ("data\\scripts\\a.py", [])
-            assert Script.parse_command("data\\scripts\\a.py 'foo \\ bar'") == ("data\\scripts\\a.py", ['foo \\ bar'])
-
-
-def test_simple():
-    with tutils.chdir(tutils.test_data.path("data/scripts")):
-        s = Script("a.py --var 42")
-        assert s.path == "a.py"
-        assert s.ns is None
-
-        s.load()
-        assert s.ns["var"] == 42
-
-        s.run("here")
-        assert s.ns["var"] == 43
-
-        s.unload()
-        assert s.ns is None
-
-        with tutils.raises(ScriptException):
-            s.run("here")
-
-        with Script("a.py --var 42") as s:
-            s.run("here")
-
-
-def test_script_exception():
-    with tutils.chdir(tutils.test_data.path("data/scripts")):
-        s = Script("syntaxerr.py")
-        with tutils.raises(ScriptException):
-            s.load()
-
-        s = Script("starterr.py")
-        with tutils.raises(ScriptException):
-            s.load()
-
-        s = Script("a.py")
-        s.load()
-        with tutils.raises(ScriptException):
-            s.load()
-
-        s = Script("a.py")
-        with tutils.raises(ScriptException):
-            s.run("here")
-
-        with tutils.raises(ScriptException):
-            with Script("reqerr.py") as s:
-                s.run("request", None)
-
-        s = Script("unloaderr.py")
-        s.load()
-        with tutils.raises(ScriptException):
-            s.unload()
diff --git a/test/mitmproxy/test_dump.py b/test/mitmproxy/test_dump.py
index 9686be84d..201386e3e 100644
--- a/test/mitmproxy/test_dump.py
+++ b/test/mitmproxy/test_dump.py
@@ -245,12 +245,12 @@ class TestDumpMaster(mastertest.MasterTest):
         assert "XRESPONSE" in ret
         assert "XCLIENTDISCONNECT" in ret
         tutils.raises(
-            dump.DumpError,
+            exceptions.AddonError,
             self.mkmaster,
             None, scripts=["nonexistent"]
         )
         tutils.raises(
-            dump.DumpError,
+            exceptions.AddonError,
             self.mkmaster,
             None, scripts=["starterr.py"]
         )
diff --git a/test/mitmproxy/test_examples.py b/test/mitmproxy/test_examples.py
index bdadcd110..f86463361 100644
--- a/test/mitmproxy/test_examples.py
+++ b/test/mitmproxy/test_examples.py
@@ -1,151 +1,126 @@
-import glob
 import json
-import mock
-import os
-import sys
-from contextlib import contextmanager
 
-from mitmproxy import script
+import six
+import sys
+import os.path
+from mitmproxy.flow import master
+from mitmproxy.flow import state
+from mitmproxy import options
+from mitmproxy import contentviews
+from mitmproxy.builtins import script
 import netlib.utils
 from netlib import tutils as netutils
 from netlib.http import Headers
-from . import tutils
+from . import tutils, mastertest
 
-example_dir = netlib.utils.Data(__name__).path("../../examples")
+example_dir = netlib.utils.Data(__name__).push("../../examples")
 
 
-@contextmanager
-def example(command):
-    command = os.path.join(example_dir, command)
-    with script.Script(command) as s:
-        yield s
+class ScriptError(Exception):
+    pass
 
 
-@mock.patch("mitmproxy.ctx.master")
-@mock.patch("mitmproxy.ctx.log")
-def test_load_scripts(log, master):
-    scripts = glob.glob("%s/*.py" % example_dir)
-
-    for f in scripts:
-        if "har_extractor" in f:
-            continue
-        if "flowwriter" in f:
-            f += " -"
-        if "iframe_injector" in f:
-            f += " foo"  # one argument required
-        if "filt" in f:
-            f += " ~a"
-        if "modify_response_body" in f:
-            f += " foo bar"  # two arguments required
-
-        s = script.Script(f)
-        try:
-            s.load()
-        except Exception as v:
-            if "ImportError" not in str(v):
-                raise
-        else:
-            s.unload()
+class RaiseMaster(master.FlowMaster):
+    def add_event(self, e, level):
+        if level in ("warn", "error"):
+            raise ScriptError(e)
 
 
-def test_add_header():
-    flow = tutils.tflow(resp=netutils.tresp())
-    with example("add_header.py") as ex:
-        ex.run("response", flow)
-        assert flow.response.headers["newheader"] == "foo"
+def tscript(cmd, args=""):
+    cmd = example_dir.path(cmd) + " " + args
+    m = RaiseMaster(options.Options(), None, state.State())
+    sc = script.Script(cmd)
+    m.addons.add(sc)
+    return m, sc
 
 
-@mock.patch("mitmproxy.contentviews.remove")
-@mock.patch("mitmproxy.contentviews.add")
-def test_custom_contentviews(add, remove):
-    with example("custom_contentviews.py"):
-        assert add.called
-        pig = add.call_args[0][0]
+class TestScripts(mastertest.MasterTest):
+    def test_add_header(self):
+        m, _ = tscript("add_header.py")
+        f = tutils.tflow(resp=netutils.tresp())
+        self.invoke(m, "response", f)
+        assert f.response.headers["newheader"] == "foo"
+
+    def test_custom_contentviews(self):
+        m, sc = tscript("custom_contentviews.py")
+        pig = contentviews.get("pig_latin_HTML")
         _, fmt = pig(b"<html>test!</html>")
         assert any(b'esttay!' in val[0][1] for val in fmt)
         assert not pig(b"gobbledygook")
-    assert remove.called
 
+    def test_iframe_injector(self):
+        with tutils.raises(ScriptError):
+            tscript("iframe_injector.py")
 
-def test_iframe_injector():
-    with tutils.raises(script.ScriptException):
-        with example("iframe_injector.py"):
-            pass
-
-    flow = tutils.tflow(resp=netutils.tresp(content=b"<html>mitmproxy</html>"))
-    with example("iframe_injector.py http://example.org/evil_iframe") as ex:
-        ex.run("response", flow)
+        m, sc = tscript("iframe_injector.py", "http://example.org/evil_iframe")
+        flow = tutils.tflow(resp=netutils.tresp(content=b"<html>mitmproxy</html>"))
+        self.invoke(m, "response", flow)
         content = flow.response.content
         assert b'iframe' in content and b'evil_iframe' in content
 
+    def test_modify_form(self):
+        m, sc = tscript("modify_form.py")
 
-def test_modify_form():
-    form_header = Headers(content_type="application/x-www-form-urlencoded")
-    flow = tutils.tflow(req=netutils.treq(headers=form_header))
-    with example("modify_form.py") as ex:
-        ex.run("request", flow)
-        assert flow.request.urlencoded_form[b"mitmproxy"] == b"rocks"
+        form_header = Headers(content_type="application/x-www-form-urlencoded")
+        f = tutils.tflow(req=netutils.treq(headers=form_header))
+        self.invoke(m, "request", f)
 
-        flow.request.headers["content-type"] = ""
-        ex.run("request", flow)
-        assert list(flow.request.urlencoded_form.items()) == [(b"foo", b"bar")]
+        assert f.request.urlencoded_form[b"mitmproxy"] == b"rocks"
 
+        f.request.headers["content-type"] = ""
+        self.invoke(m, "request", f)
+        assert list(f.request.urlencoded_form.items()) == [(b"foo", b"bar")]
 
-def test_modify_querystring():
-    flow = tutils.tflow(req=netutils.treq(path=b"/search?q=term"))
-    with example("modify_querystring.py") as ex:
-        ex.run("request", flow)
-        assert flow.request.query["mitmproxy"] == "rocks"
+    def test_modify_querystring(self):
+        m, sc = tscript("modify_querystring.py")
+        f = tutils.tflow(req=netutils.treq(path="/search?q=term"))
 
-        flow.request.path = "/"
-        ex.run("request", flow)
-        assert flow.request.query["mitmproxy"] == "rocks"
+        self.invoke(m, "request", f)
+        assert f.request.query["mitmproxy"] == "rocks"
 
+        f.request.path = "/"
+        self.invoke(m, "request", f)
+        assert f.request.query["mitmproxy"] == "rocks"
 
-def test_modify_response_body():
-    with tutils.raises(script.ScriptException):
-        with example("modify_response_body.py"):
-            assert True
+    def test_modify_response_body(self):
+        with tutils.raises(ScriptError):
+            tscript("modify_response_body.py")
 
-    flow = tutils.tflow(resp=netutils.tresp(content=b"I <3 mitmproxy"))
-    with example("modify_response_body.py mitmproxy rocks") as ex:
-        assert ex.ns["state"]["old"] == b"mitmproxy" and ex.ns["state"]["new"] == b"rocks"
-        ex.run("response", flow)
-        assert flow.response.content == b"I <3 rocks"
+        m, sc = tscript("modify_response_body.py", "mitmproxy rocks")
+        f = tutils.tflow(resp=netutils.tresp(content=b"I <3 mitmproxy"))
+        self.invoke(m, "response", f)
+        assert f.response.content == b"I <3 rocks"
 
+    def test_redirect_requests(self):
+        m, sc = tscript("redirect_requests.py")
+        f = tutils.tflow(req=netutils.treq(host="example.org"))
+        self.invoke(m, "request", f)
+        assert f.request.host == "mitmproxy.org"
 
-def test_redirect_requests():
-    flow = tutils.tflow(req=netutils.treq(host=b"example.org"))
-    with example("redirect_requests.py") as ex:
-        ex.run("request", flow)
-        assert flow.request.host == "mitmproxy.org"
+    def test_har_extractor(self):
+        if sys.version_info >= (3, 0):
+            with tutils.raises("does not work on Python 3"):
+                tscript("har_extractor.py")
+            return
 
+        with tutils.raises(ScriptError):
+            tscript("har_extractor.py")
 
-@mock.patch("mitmproxy.ctx.log")
-def test_har_extractor(log):
-    if sys.version_info >= (3, 0):
-        with tutils.raises("does not work on Python 3"):
-            with example("har_extractor.py -"):
-                pass
-        return
+        with tutils.tmpdir() as tdir:
+            times = dict(
+                timestamp_start=746203272,
+                timestamp_end=746203272,
+            )
 
-    with tutils.raises(script.ScriptException):
-        with example("har_extractor.py"):
-            pass
+            path = os.path.join(tdir, "file")
+            m, sc = tscript("har_extractor.py", six.moves.shlex_quote(path))
+            f = tutils.tflow(
+                req=netutils.treq(**times),
+                resp=netutils.tresp(**times)
+            )
+            self.invoke(m, "response", f)
+            m.addons.remove(sc)
 
-    times = dict(
-        timestamp_start=746203272,
-        timestamp_end=746203272,
-    )
-
-    flow = tutils.tflow(
-        req=netutils.treq(**times),
-        resp=netutils.tresp(**times)
-    )
-
-    with example("har_extractor.py -") as ex:
-        ex.run("response", flow)
-
-        with open(tutils.test_data.path("data/har_extractor.har")) as fp:
-            test_data = json.load(fp)
-            assert json.loads(ex.ns["context"].HARLog.json()) == test_data["test_response"]
+            with open(path, "rb") as f:
+                test_data = json.load(f)
+            assert len(test_data["log"]["pages"]) == 1
diff --git a/test/mitmproxy/test_flow.py b/test/mitmproxy/test_flow.py
index 1a07f74d3..c58a97038 100644
--- a/test/mitmproxy/test_flow.py
+++ b/test/mitmproxy/test_flow.py
@@ -5,7 +5,7 @@ import netlib.utils
 from netlib.http import Headers
 from mitmproxy import filt, controller, flow
 from mitmproxy.contrib import tnetstring
-from mitmproxy.exceptions import FlowReadException, ScriptException
+from mitmproxy.exceptions import FlowReadException
 from mitmproxy.models import Error
 from mitmproxy.models import Flow
 from mitmproxy.models import HTTPFlow
@@ -674,21 +674,6 @@ class TestSerialize:
 
 class TestFlowMaster:
 
-    def test_load_script(self):
-        s = flow.State()
-        fm = flow.FlowMaster(None, None, s)
-
-        fm.load_script(tutils.test_data.path("data/scripts/a.py"))
-        fm.load_script(tutils.test_data.path("data/scripts/a.py"))
-        fm.unload_scripts()
-        with tutils.raises(ScriptException):
-            fm.load_script("nonexistent")
-        try:
-            fm.load_script(tutils.test_data.path("data/scripts/starterr.py"))
-        except ScriptException as e:
-            assert "ValueError" in str(e)
-        assert len(fm.scripts) == 0
-
     def test_getset_ignore(self):
         p = mock.Mock()
         p.config.check_ignore = HostMatcher()
@@ -708,51 +693,7 @@ class TestFlowMaster:
         assert "intercepting" in fm.replay_request(f)
 
         f.live = True
-        assert "live" in fm.replay_request(f, run_scripthooks=True)
-
-    def test_script_reqerr(self):
-        s = flow.State()
-        fm = flow.FlowMaster(None, None, s)
-        fm.load_script(tutils.test_data.path("data/scripts/reqerr.py"))
-        f = tutils.tflow()
-        fm.clientconnect(f.client_conn)
-        assert fm.request(f)
-
-    def test_script(self):
-        s = flow.State()
-        fm = flow.FlowMaster(None, None, s)
-        fm.load_script(tutils.test_data.path("data/scripts/all.py"))
-        f = tutils.tflow(resp=True)
-
-        f.client_conn.acked = False
-        fm.clientconnect(f.client_conn)
-        assert fm.scripts[0].ns["log"][-1] == "clientconnect"
-        f.server_conn.acked = False
-        fm.serverconnect(f.server_conn)
-        assert fm.scripts[0].ns["log"][-1] == "serverconnect"
-        f.reply.acked = False
-        fm.request(f)
-        assert fm.scripts[0].ns["log"][-1] == "request"
-        f.reply.acked = False
-        fm.response(f)
-        assert fm.scripts[0].ns["log"][-1] == "response"
-        # load second script
-        fm.load_script(tutils.test_data.path("data/scripts/all.py"))
-        assert len(fm.scripts) == 2
-        f.server_conn.reply.acked = False
-        fm.clientdisconnect(f.server_conn)
-        assert fm.scripts[0].ns["log"][-1] == "clientdisconnect"
-        assert fm.scripts[1].ns["log"][-1] == "clientdisconnect"
-
-        # unload first script
-        fm.unload_scripts()
-        assert len(fm.scripts) == 0
-        fm.load_script(tutils.test_data.path("data/scripts/all.py"))
-
-        f.error = tutils.terr()
-        f.reply.acked = False
-        fm.error(f)
-        assert fm.scripts[0].ns["log"][-1] == "error"
+        assert "live" in fm.replay_request(f)
 
     def test_duplicate_flow(self):
         s = flow.State()
@@ -789,7 +730,6 @@ class TestFlowMaster:
         f.error.reply = controller.DummyReply()
         fm.error(f)
 
-        fm.load_script(tutils.test_data.path("data/scripts/a.py"))
         fm.shutdown()
 
     def test_client_playback(self):
diff --git a/test/mitmproxy/test_script.py b/test/mitmproxy/test_script.py
deleted file mode 100644
index 1e8220f10..000000000
--- a/test/mitmproxy/test_script.py
+++ /dev/null
@@ -1,13 +0,0 @@
-from mitmproxy import flow
-from . import tutils
-
-
-def test_duplicate_flow():
-    s = flow.State()
-    fm = flow.FlowMaster(None, None, s)
-    fm.load_script(tutils.test_data.path("data/scripts/duplicate_flow.py"))
-    f = tutils.tflow()
-    fm.request(f)
-    assert fm.state.flow_count() == 2
-    assert not fm.state.view[0].request.is_replay
-    assert fm.state.view[1].request.is_replay
diff --git a/test/mitmproxy/test_server.py b/test/mitmproxy/test_server.py
index 9dd8b79c2..a5196daec 100644
--- a/test/mitmproxy/test_server.py
+++ b/test/mitmproxy/test_server.py
@@ -13,6 +13,7 @@ from netlib.http import authentication, http1
 from netlib.tutils import raises
 from pathod import pathoc, pathod
 
+from mitmproxy.builtins import script
 from mitmproxy import controller
 from mitmproxy.proxy.config import HostMatcher
 from mitmproxy.models import Error, HTTPResponse, HTTPFlow
@@ -287,10 +288,13 @@ class TestHTTP(tservers.HTTPProxyTest, CommonMixin, AppMixin):
         self.master.set_stream_large_bodies(None)
 
     def test_stream_modify(self):
-        self.master.load_script(tutils.test_data.path("data/scripts/stream_modify.py"))
+        s = script.Script(
+            tutils.test_data.path("data/addonscripts/stream_modify.py")
+        )
+        self.master.addons.add(s)
         d = self.pathod('200:b"foo"')
         assert d.content == b"bar"
-        self.master.unload_scripts()
+        self.master.addons.remove(s)
 
 
 class TestHTTPAuth(tservers.HTTPProxyTest):
@@ -512,15 +516,15 @@ class TestTransparent(tservers.TransparentProxyTest, CommonMixin, TcpMixin):
     ssl = False
 
     def test_tcp_stream_modify(self):
-        self.master.load_script(tutils.test_data.path("data/scripts/tcp_stream_modify.py"))
-
+        s = script.Script(
+            tutils.test_data.path("data/addonscripts/tcp_stream_modify.py")
+        )
+        self.master.addons.add(s)
         self._tcpproxy_on()
         d = self.pathod('200:b"foo"')
         self._tcpproxy_off()
-
         assert d.content == b"bar"
-
-        self.master.unload_scripts()
+        self.master.addons.remove(s)
 
 
 class TestTransparentSSL(tservers.TransparentProxyTest, CommonMixin, TcpMixin):