diff --git a/tractor/_debug.py b/tractor/_debug.py
index 5d3626be4..e5da9a53c 100644
--- a/tractor/_debug.py
+++ b/tractor/_debug.py
@@ -3,7 +3,7 @@
 """
 import sys
 from functools import partial
-from typing import Awaitable, Tuple
+from typing import Awaitable, Tuple, Optional, Callable
 
 from async_generator import aclosing
 import tractor
@@ -27,18 +27,25 @@
 __all__ = ['breakpoint', 'post_mortem']
 
 
-# TODO: is there some way to determine this programatically?
-_pdb_exit_patterns = tuple(
-    str.encode(patt + "\n") for patt in ('c', 'cont', 'continue', 'q', 'quit')
-)
+# placeholder for function to set a ``trio.Event``
+_pdb_release_hook: Optional[Callable] = None
 
 
-_pdb_release_hook = None
+class TractorConfig(pdbpp.DefaultConfig):
+    """Custom ``pdbpp`` goodness.
+    """
+    sticky_by_default = True
+
+    def teardown(self, _pdb):
+        _pdb_release_hook(_pdb)
 
 
 class PdbwTeardown(pdbpp.Pdb):
     """Add teardown hooks to the regular ``pdbpp.Pdb``.
     """
+    # override the pdbpp config with our coolio one
+    DefaultConfig = TractorConfig
+
     # TODO: figure out how to dissallow recursive .set_trace() entry
     # since that'll cause deadlock for us.
     def set_continue(self):
@@ -50,22 +57,15 @@ def set_quit(self):
         self.config.teardown(self)
 
 
-class TractorConfig(pdbpp.DefaultConfig):
-    """Custom ``pdbpp`` goodness.
-    """
-    sticky_by_default = True
-
-    def teardown(self, _pdb):
-        _pdb_release_hook(_pdb)
-
-
-# override the pdbpp config with our coolio one
-pdbpp.Pdb.DefaultConfig = TractorConfig
-
-
 # TODO: will be needed whenever we get to true remote debugging.
 # XXX see https://github.com/goodboy/tractor/issues/130
 
+# # TODO: is there some way to determine this programatically?
+# _pdb_exit_patterns = tuple(
+#     str.encode(patt + "\n") for patt in (
+#         'c', 'cont', 'continue', 'q', 'quit')
+# )
+
 # def subactoruid2proc(
 #     actor: 'Actor',  # noqa
 #     uid: Tuple[str, str]
@@ -170,17 +170,16 @@ def unlock(_pdb):
     _pdb_release_hook = unlock
 
     async def _bp():
-        # this must be awaited by caller
-        await actor._root_nursery.start(
-            wait_for_parent_stdin_hijack
-        )
+        # this **must** be awaited by the caller and is done using the
+        # root nursery so that the debugger can continue to run without
+        # being restricted by the scope of a new task nursery.
+        await actor._root_nursery.start(wait_for_parent_stdin_hijack)
 
-        # block here one frame up where ``breakpoint()``
-        # was awaited and begin handling stdin
+        # block here one (at the appropriate frame *up* where
+        # ``breakpoint()`` was awaited and begin handling stdio
         debug_func(actor)
 
-    # return wait_for_parent_stdin_hijack()
-    return _bp()
+    return _bp()  # user code **must** await this!
 
 
 def _set_trace(actor):