diff --git a/.ci/ansible_tests.py b/.ci/ansible_tests.py
index 51eab874..4df2dc70 100755
--- a/.ci/ansible_tests.py
+++ b/.ci/ansible_tests.py
@@ -20,11 +20,17 @@ def pause_if_interactive():
             signal.pause()
 
 
+interesting = ci_lib.get_interesting_procs()
+
+
 with ci_lib.Fold('unit_tests'):
     os.environ['SKIP_MITOGEN'] = '1'
     ci_lib.run('./run_tests -v')
 
 
+ci_lib.check_stray_processes(interesting)
+
+
 with ci_lib.Fold('docker_setup'):
     containers = ci_lib.make_containers()
     ci_lib.start_containers(containers)
@@ -75,4 +81,7 @@ with ci_lib.Fold('ansible'):
         pause_if_interactive()
         raise
 
+
+ci_lib.check_stray_processes(interesting, containers)
+
 pause_if_interactive()
diff --git a/.ci/azure-pipelines.yml b/.ci/azure-pipelines.yml
index 6d0832da..920e82a1 100644
--- a/.ci/azure-pipelines.yml
+++ b/.ci/azure-pipelines.yml
@@ -3,11 +3,6 @@
 # Add steps that analyze code, save the dist with the build record, publish to a PyPI-compatible index, and more:
 # https://docs.microsoft.com/azure/devops/pipelines/languages/python
 
-trigger:
-  branches:
-    exclude:
-    - docs-master
-
 jobs:
 
 - job: Mac
diff --git a/.ci/ci_lib.py b/.ci/ci_lib.py
index 34a6faba..971ae5d8 100644
--- a/.ci/ci_lib.py
+++ b/.ci/ci_lib.py
@@ -215,6 +215,46 @@ def make_containers(name_prefix='', port_offset=0):
     return lst
 
 
+# ssh removed from here because 'linear' strategy relies on processes that hang
+# around after the Ansible run completes
+INTERESTING_COMMS = ('python', 'sudo', 'su', 'doas')
+
+
+def proc_is_docker(pid):
+    try:
+        fp = open('/proc/%s/cgroup' % (pid,), 'r')
+    except IOError:
+        return False
+
+    try:
+        return 'docker' in fp.read()
+    finally:
+        fp.close()
+
+
+def get_interesting_procs(container_name=None):
+    args = ['ps', '-a', '-x', '-oppid=', '-opid=', '-ocomm=', '-ocommand=']
+    if container_name is not None:
+        args = ['docker', 'exec', container_name] + args
+
+    out = []
+    for line in subprocess__check_output(args).decode().splitlines():
+        ppid, pid, comm, rest = line.split(None, 3)
+        if (
+            (
+                any(comm.startswith(s) for s in INTERESTING_COMMS) or
+                'mitogen:' in rest
+            ) and
+            (
+                container_name is not None or
+                (not proc_is_docker(pid))
+            )
+        ):
+            out.append((int(pid), line))
+
+    return sorted(out)
+
+
 def start_containers(containers):
     if os.environ.get('KEEP'):
         return
@@ -236,9 +276,44 @@ def start_containers(containers):
         ]
         for container in containers
     ])
+
+    for container in containers:
+        container['interesting'] = get_interesting_procs(container['name'])
+
     return containers
 
 
+def verify_procs(hostname, old, new):
+    oldpids = set(pid for pid, _ in old)
+    if any(pid not in oldpids for pid, _ in new):
+        print('%r had stray processes running:' % (hostname,))
+        for pid, line in new:
+            if pid not in oldpids:
+                print('New process:', line)
+
+        print()
+        return False
+
+    return True
+
+
+def check_stray_processes(old, containers=None):
+    ok = True
+
+    new = get_interesting_procs()
+    if old is not None:
+        ok &= verify_procs('test host machine', old, new)
+
+    for container in containers or ():
+        ok &= verify_procs(
+            container['name'],
+            container['interesting'],
+            get_interesting_procs(container['name'])
+        )
+
+    assert ok, 'stray processes were found'
+
+
 def dump_file(path):
     print()
     print('--- %s ---' % (path,))
diff --git a/.ci/debops_common_tests.py b/.ci/debops_common_tests.py
index 8b35de1e..e8f2907b 100755
--- a/.ci/debops_common_tests.py
+++ b/.ci/debops_common_tests.py
@@ -68,9 +68,15 @@ with ci_lib.Fold('job_setup'):
     os.environ['ANSIBLE_HOST_KEY_CHECKING'] = 'False'
 
 
+interesting = ci_lib.get_interesting_procs()
+
 with ci_lib.Fold('first_run'):
     ci_lib.run('debops common %s', ' '.join(sys.argv[1:]))
 
+ci_lib.check_stray_processes(interesting, containers)
+
 
 with ci_lib.Fold('second_run'):
     ci_lib.run('debops common %s', ' '.join(sys.argv[1:]))
+
+ci_lib.check_stray_processes(interesting, containers)
diff --git a/.ci/mitogen_install.py b/.ci/mitogen_install.py
index 72bc75e3..b8862f89 100755
--- a/.ci/mitogen_install.py
+++ b/.ci/mitogen_install.py
@@ -14,4 +14,5 @@ if ci_lib.have_docker():
         'docker pull %s' % (ci_lib.image_for_distro(ci_lib.DISTRO),),
     ])
 
+
 ci_lib.run_batches(batches)
diff --git a/.ci/mitogen_tests.py b/.ci/mitogen_tests.py
index 36928ac9..4de94b4c 100755
--- a/.ci/mitogen_tests.py
+++ b/.ci/mitogen_tests.py
@@ -14,4 +14,6 @@ os.environ.update({
 if not ci_lib.have_docker():
     os.environ['SKIP_DOCKER_TESTS'] = '1'
 
+interesting = ci_lib.get_interesting_procs()
 ci_lib.run('./run_tests -v')
+ci_lib.check_stray_processes(interesting)
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 707099a8..26b2c316 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -164,9 +164,16 @@ Core Library
   `closed` flag, preventing historical bugs where a double close could destroy
   descriptors belonging to unrelated streams.
 
+* `#586 <https://github.com/dw/mitogen/issues/586>`_: fix import of
+  :mod:`__main__` on later versions of Python 3 when running from the
+  interactive console.
+
 * `#606 <https://github.com/dw/mitogen/issues/606>`_: fix example code on the
   documentation front page.
 
+* `#612 <https://github.com/dw/mitogen/issues/612>`_: fix various errors
+  introduced by stream refactoring.
+
 * `a5536c35 <https://github.com/dw/mitogen/commit/a5536c35>`_: avoid quadratic
   buffer management when logging lines received from a child's redirected
   standard IO.
@@ -183,6 +190,14 @@ Core Library
   buffered items, causing future :meth:`get` calls to block or fail even though
   data existed that could be returned.
 
+* `5924af15 <https://github.com/dw/mitogen/commit/5924af15>`_: *[security]* the
+  unidirectional routing mode, in which contexts may only communicate with
+  parents and never siblings (so a program cannot accidentally bridge
+  air-gapped networks) was not inherited when a child context was initiated
+  directly from an existing child. This did not effect the Ansible extension,
+  since the controller initiates any new context used for routing, only forked
+  tasks are initiated by children.
+
 
 Thanks!
 ~~~~~~~
@@ -193,8 +208,10 @@ bug reports, testing, features and fixes in this release contributed by
 `Anton Markelov <https://github.com/strangeman>`_,
 `Dan <https://github.com/dsgnr>`_,
 `Dave Cottlehuber <https://github.com/dch>`_,
+`Denis Krienbühl <https://github.com/href>`_,
 `El Mehdi CHAOUKI <https://github.com/elmchaouki>`_,
 `James Hogarth <https://github.com/hogarthj>`_,
+`Marc Hartmayer <https://github.com/marc1006>`_,
 `Nigel Metheringham <https://github.com/nigelm>`_,
 `Orion Poplawski <https://github.com/opoplawski>`_,
 `Pieter Voet <https://github.com/pietervoet/>`_,
diff --git a/mitogen/compat/pkgutil.py b/mitogen/compat/pkgutil.py
index df3983a2..15eb2afa 100644
--- a/mitogen/compat/pkgutil.py
+++ b/mitogen/compat/pkgutil.py
@@ -542,7 +542,8 @@ def extend_path(path, name):
         if os.path.isfile(pkgfile):
             try:
                 f = open(pkgfile)
-            except IOError as msg:
+            except IOError:
+                msg = sys.exc_info()[1]
                 sys.stderr.write("Can't open %s: %s\n" %
                                  (pkgfile, msg))
             else:
diff --git a/mitogen/core.py b/mitogen/core.py
index 8428a479..a14286f9 100644
--- a/mitogen/core.py
+++ b/mitogen/core.py
@@ -1937,18 +1937,28 @@ class MitogenProtocol(Protocol):
     :class:`Protocol` implementing mitogen's :ref:`stream protocol
     <stream-protocol>`.
     """
-    #: If not :data:`None`, :class:`Router` stamps this into
-    #: :attr:`Message.auth_id` of every message received on this stream.
-    auth_id = None
-
     #: If not :data:`False`, indicates the stream has :attr:`auth_id` set and
     #: its value is the same as :data:`mitogen.context_id` or appears in
     #: :data:`mitogen.parent_ids`.
     is_privileged = False
 
-    def __init__(self, router, remote_id):
+    def __init__(self, router, remote_id, auth_id=None,
+                 local_id=None, parent_ids=None):
         self._router = router
         self.remote_id = remote_id
+        #: If not :data:`None`, :class:`Router` stamps this into
+        #: :attr:`Message.auth_id` of every message received on this stream.
+        self.auth_id = auth_id
+
+        if parent_ids is None:
+            parent_ids = mitogen.parent_ids
+        if local_id is None:
+            local_id = mitogen.context_id
+
+        self.is_privileged = (
+            (remote_id in parent_ids) or
+            auth_id in ([local_id] + parent_ids)
+        )
         self.sent_modules = set(['mitogen', 'mitogen.core'])
         self._input_buf = collections.deque()
         self._input_buf_len = 0
@@ -2800,8 +2810,8 @@ class Router(object):
     broker_exit_msg = 'Broker has exitted'
     no_route_msg = 'no route to %r, my ID is %r'
     unidirectional_msg = (
-        'routing mode prevents forward of message from context %d via '
-        'context %d'
+        'routing mode prevents forward of message from context %d to '
+        'context %d via context %d'
     )
 
     def __init__(self, broker):
@@ -3152,7 +3162,9 @@ class Router(object):
                 (in_stream.protocol.is_privileged or
                  out_stream.protocol.is_privileged):
             self._maybe_send_dead(msg, self.unidirectional_msg,
-                in_stream.protocol.remote_id, out_stream.protocol.remote_id)
+                in_stream.protocol.remote_id,
+                out_stream.protocol.remote_id,
+                mitogen.context_id)
             return
 
         out_stream.protocol._send(msg)
@@ -3623,7 +3635,7 @@ class ExternalContext(object):
         self.broker = Broker(activate_compat=False)
         self.router = Router(self.broker)
         self.router.debug = self.config.get('debug', False)
-        self.router.undirectional = self.config['unidirectional']
+        self.router.unidirectional = self.config['unidirectional']
         self.router.add_handler(
             fn=self._on_shutdown_msg,
             handle=SHUTDOWN,
@@ -3641,7 +3653,12 @@ class ExternalContext(object):
         os.close(in_fd)
 
         out_fp = os.fdopen(os.dup(self.config.get('out_fd', 1)), 'wb', 0)
-        self.stream = MitogenProtocol.build_stream(self.router, parent_id)
+        self.stream = MitogenProtocol.build_stream(
+            self.router,
+            parent_id,
+            local_id=self.config['context_id'],
+            parent_ids=self.config['parent_ids']
+        )
         self.stream.accept(in_fp, out_fp)
         self.stream.name = 'parent'
         self.stream.receive_side.keep_alive = False
diff --git a/mitogen/select.py b/mitogen/select.py
index f880fcc3..3875042b 100644
--- a/mitogen/select.py
+++ b/mitogen/select.py
@@ -122,9 +122,10 @@ class Select(object):
     @classmethod
     def all(cls, receivers):
         """
-        Take an iterable of receivers and retrieve a :class:`Message` from
-        each, returning the result of calling `msg.unpickle()` on each in turn.
-        Results are returned in the order they arrived.
+        Take an iterable of receivers and retrieve a :class:`Message
+        <mitogen.core.Message>` from each, returning the result of calling
+        :meth:`Message.unpickle() <mitogen.core.Message.unpickle>` on each in
+        turn. Results are returned in the order they arrived.
 
         This is sugar for handling batch :meth:`Context.call_async
         <mitogen.parent.Context.call_async>` invocations:
diff --git a/mitogen/unix.py b/mitogen/unix.py
index 645b061d..1af1c0ec 100644
--- a/mitogen/unix.py
+++ b/mitogen/unix.py
@@ -162,10 +162,9 @@ class Listener(mitogen.core.Protocol):
         stream = mitogen.core.MitogenProtocol.build_stream(
             router=self._router,
             remote_id=context_id,
+            auth_id=mitogen.context_id,
         )
         stream.name = u'unix_client.%d' % (pid,)
-        stream.protocol.auth_id = mitogen.context_id
-        stream.protocol.is_privileged = True
         stream.accept(sock, sock)
         LOG.debug('listener: accepted connection from PID %d: %s',
                   pid, stream.name)
diff --git a/tests/router_test.py b/tests/router_test.py
index 1bd6c26a..dba56c9b 100644
--- a/tests/router_test.py
+++ b/tests/router_test.py
@@ -1,9 +1,11 @@
+import sys
 import time
 import zlib
 
 import unittest2
 
 import testlib
+import mitogen.core
 import mitogen.master
 import mitogen.parent
 import mitogen.utils
@@ -260,6 +262,13 @@ class MessageSizeTest(testlib.BrokerMixin, testlib.TestCase):
         size = remote.call(return_router_max_message_size)
         self.assertEquals(size, 64*1024)
 
+    def test_remote_of_remote_configured(self):
+        router = self.klass(broker=self.broker, max_message_size=64*1024)
+        remote = router.local()
+        remote2 = router.local(via=remote)
+        size = remote2.call(return_router_max_message_size)
+        self.assertEquals(size, 64*1024)
+
     def test_remote_exceeded(self):
         # Ensure new contexts receive a router with the same value.
         router = self.klass(broker=self.broker, max_message_size=64*1024)
@@ -341,22 +350,43 @@ class NoRouteTest(testlib.RouterMixin, testlib.TestCase):
         ))
 
 
+def test_siblings_cant_talk(router):
+    l1 = router.local()
+    l2 = router.local()
+    logs = testlib.LogCapturer()
+    logs.start()
+
+    try:
+        l2.call(ping_context, l1)
+    except mitogen.core.CallError:
+        e = sys.exc_info()[1]
+
+    msg = mitogen.core.Router.unidirectional_msg % (
+        l2.context_id,
+        l1.context_id,
+        mitogen.context_id,
+    )
+    assert msg in str(e)
+    assert 'routing mode prevents forward of ' in logs.stop()
+
+
+@mitogen.core.takes_econtext
+def test_siblings_cant_talk_remote(econtext):
+    mitogen.parent.upgrade_router(econtext)
+    test_siblings_cant_talk(econtext.router)
+
+
 class UnidirectionalTest(testlib.RouterMixin, testlib.TestCase):
-    def test_siblings_cant_talk(self):
+    def test_siblings_cant_talk_master(self):
         self.router.unidirectional = True
-        l1 = self.router.local()
-        l2 = self.router.local()
-        logs = testlib.LogCapturer()
-        logs.start()
-        e = self.assertRaises(mitogen.core.CallError,
-                              lambda: l2.call(ping_context, l1))
+        test_siblings_cant_talk(self.router)
 
-        msg = self.router.unidirectional_msg % (
-            l2.context_id,
-            l1.context_id,
-        )
-        self.assertTrue(msg in str(e))
-        self.assertTrue('routing mode prevents forward of ' in logs.stop())
+    def test_siblings_cant_talk_parent(self):
+        # ensure 'unidirectional' attribute is respected for contexts started
+        # by children.
+        self.router.unidirectional = True
+        parent = self.router.local()
+        parent.call(test_siblings_cant_talk_remote)
 
     def test_auth_id_can_talk(self):
         self.router.unidirectional = True
diff --git a/tests/testlib.py b/tests/testlib.py
index 3d641892..255fba88 100644
--- a/tests/testlib.py
+++ b/tests/testlib.py
@@ -454,6 +454,22 @@ class DockerizedSshDaemon(object):
     def wait_for_sshd(self):
         wait_for_port(self.get_host(), self.port, pattern='OpenSSH')
 
+    def check_processes(self):
+        args = ['docker', 'exec', self.container_name, 'ps', '-o', 'comm=']
+        counts = {}
+        for comm in subprocess__check_output(args).decode().splitlines():
+            comm = comm.strip()
+            counts[comm] = counts.get(comm, 0) + 1
+
+        if counts != {'ps': 1, 'sshd': 1}:
+            assert 0, (
+                'Docker container %r contained extra running processes '
+                'after test completed: %r' % (
+                    self.container_name,
+                    counts
+                )
+            )
+
     def close(self):
         args = ['docker', 'rm', '-f', self.container_name]
         subprocess__check_output(args)
@@ -501,6 +517,7 @@ class DockerMixin(RouterMixin):
 
     @classmethod
     def tearDownClass(cls):
+        cls.dockerized_ssh.check_processes()
         cls.dockerized_ssh.close()
         super(DockerMixin, cls).tearDownClass()