diff --git a/examples/advanced_faults/ipc_failure_during_stream.py b/examples/advanced_faults/ipc_failure_during_stream.py
index f3a709e0..c88e0dfe 100644
--- a/examples/advanced_faults/ipc_failure_during_stream.py
+++ b/examples/advanced_faults/ipc_failure_during_stream.py
@@ -16,6 +16,7 @@ from tractor import (
     ContextCancelled,
     MsgStream,
     _testing,
+    trionics,
 )
 import trio
 import pytest
@@ -62,9 +63,8 @@ async def recv_and_spawn_net_killers(
     await ctx.started()
     async with (
         ctx.open_stream() as stream,
-        trio.open_nursery(
-            strict_exception_groups=False,
-        ) as tn,
+        trionics.collapse_eg(),
+        trio.open_nursery() as tn,
     ):
         async for i in stream:
             print(f'child echoing {i}')
diff --git a/examples/quick_cluster.py b/examples/quick_cluster.py
index 2378a3cf..3fa4ca2a 100644
--- a/examples/quick_cluster.py
+++ b/examples/quick_cluster.py
@@ -23,9 +23,8 @@ async def main():
             modules=[__name__]
         ) as portal_map,
 
-        trio.open_nursery(
-            strict_exception_groups=False,
-        ) as tn,
+        tractor.trionics.collapse_eg(),
+        trio.open_nursery() as tn,
     ):
 
         for (name, portal) in portal_map.items():
diff --git a/tests/devx/test_debugger.py b/tests/devx/test_debugger.py
index 975fbc03..6179ef01 100644
--- a/tests/devx/test_debugger.py
+++ b/tests/devx/test_debugger.py
@@ -317,7 +317,6 @@ def test_subactor_breakpoint(
 
     assert in_prompt_msg(
         child, [
-        'MessagingError:',
         'RemoteActorError:',
          "('breakpoint_forever'",
          'bdb.BdbQuit',
diff --git a/tests/test_advanced_streaming.py b/tests/test_advanced_streaming.py
index 64f24167..907a2196 100644
--- a/tests/test_advanced_streaming.py
+++ b/tests/test_advanced_streaming.py
@@ -313,9 +313,8 @@ async def inf_streamer(
         # `trio.EndOfChannel` doesn't propagate directly to the above
         # .open_stream() parent, resulting in it also raising instead
         # of gracefully absorbing as normal.. so how to handle?
-        trio.open_nursery(
-            strict_exception_groups=False,
-        ) as tn,
+        tractor.trionics.collapse_eg(),
+        trio.open_nursery() as tn,
     ):
         async def close_stream_on_sentinel():
             async for msg in stream:
diff --git a/tests/test_cancellation.py b/tests/test_cancellation.py
index ca14ae4b..27fd59d7 100644
--- a/tests/test_cancellation.py
+++ b/tests/test_cancellation.py
@@ -236,7 +236,10 @@ async def stream_forever():
 async def test_cancel_infinite_streamer(start_method):
 
     # stream for at most 1 seconds
-    with trio.move_on_after(1) as cancel_scope:
+    with (
+        trio.fail_after(4),
+        trio.move_on_after(1) as cancel_scope
+    ):
         async with tractor.open_nursery() as n:
             portal = await n.start_actor(
                 'donny',
@@ -284,20 +287,32 @@ async def test_cancel_infinite_streamer(start_method):
     ],
 )
 @tractor_test
-async def test_some_cancels_all(num_actors_and_errs, start_method, loglevel):
-    """Verify a subset of failed subactors causes all others in
+async def test_some_cancels_all(
+    num_actors_and_errs: tuple,
+    start_method: str,
+    loglevel: str,
+):
+    '''
+    Verify a subset of failed subactors causes all others in
     the nursery to be cancelled just like the strategy in trio.
 
     This is the first and only supervisory strategy at the moment.
-    """
-    num_actors, first_err, err_type, ria_func, da_func = num_actors_and_errs
+
+    '''
+    (
+        num_actors,
+        first_err,
+        err_type,
+        ria_func,
+        da_func,
+    ) = num_actors_and_errs
     try:
-        async with tractor.open_nursery() as n:
+        async with tractor.open_nursery() as an:
 
             # spawn the same number of deamon actors which should be cancelled
             dactor_portals = []
             for i in range(num_actors):
-                dactor_portals.append(await n.start_actor(
+                dactor_portals.append(await an.start_actor(
                     f'deamon_{i}',
                     enable_modules=[__name__],
                 ))
@@ -307,7 +322,7 @@ async def test_some_cancels_all(num_actors_and_errs, start_method, loglevel):
             for i in range(num_actors):
                 # start actor(s) that will fail immediately
                 riactor_portals.append(
-                    await n.run_in_actor(
+                    await an.run_in_actor(
                         func,
                         name=f'actor_{i}',
                         **kwargs
@@ -337,7 +352,8 @@ async def test_some_cancels_all(num_actors_and_errs, start_method, loglevel):
 
         # should error here with a ``RemoteActorError`` or ``MultiError``
 
-    except first_err as err:
+    except first_err as _err:
+        err = _err
         if isinstance(err, BaseExceptionGroup):
             assert len(err.exceptions) == num_actors
             for exc in err.exceptions:
@@ -348,8 +364,8 @@ async def test_some_cancels_all(num_actors_and_errs, start_method, loglevel):
         elif isinstance(err, tractor.RemoteActorError):
             assert err.boxed_type == err_type
 
-        assert n.cancelled is True
-        assert not n._children
+        assert an.cancelled is True
+        assert not an._children
     else:
         pytest.fail("Should have gotten a remote assertion error?")
 
@@ -519,10 +535,15 @@ def test_cancel_via_SIGINT_other_task(
     async def main():
         # should never timeout since SIGINT should cancel the current program
         with trio.fail_after(timeout):
-            async with trio.open_nursery(
-                strict_exception_groups=False,
-            ) as n:
-                await n.start(spawn_and_sleep_forever)
+            async with (
+
+                # XXX ?TODO? why no work!?
+                # tractor.trionics.collapse_eg(),
+                trio.open_nursery(
+                    strict_exception_groups=False,
+                ) as tn,
+            ):
+                await tn.start(spawn_and_sleep_forever)
                 if 'mp' in spawn_backend:
                     time.sleep(0.1)
                 os.kill(pid, signal.SIGINT)
@@ -533,38 +554,123 @@ def test_cancel_via_SIGINT_other_task(
 
 async def spin_for(period=3):
     "Sync sleep."
+    print(f'sync sleeping in sub-sub for {period}\n')
     time.sleep(period)
 
 
-async def spawn():
-    async with tractor.open_nursery() as tn:
-        await tn.run_in_actor(
+async def spawn_sub_with_sync_blocking_task():
+    async with tractor.open_nursery() as an:
+        print('starting sync blocking subactor..\n')
+        await an.run_in_actor(
             spin_for,
             name='sleeper',
         )
+        print('exiting first subactor layer..\n')
 
 
+@pytest.mark.parametrize(
+    'man_cancel_outer',
+    [
+        False,  # passes if delay != 2
+
+        # always causes an unexpected eg-w-embedded-assert-err?
+        pytest.param(True,
+             marks=pytest.mark.xfail(
+                 reason=(
+                    'always causes an unexpected eg-w-embedded-assert-err?'
+                )
+            ),
+        ),
+    ],
+)
 @no_windows
 def test_cancel_while_childs_child_in_sync_sleep(
-    loglevel,
-    start_method,
-    spawn_backend,
+    loglevel: str,
+    start_method: str,
+    spawn_backend: str,
+    debug_mode: bool,
+    reg_addr: tuple,
+    man_cancel_outer: bool,
 ):
-    """Verify that a child cancelled while executing sync code is torn
+    '''
+    Verify that a child cancelled while executing sync code is torn
     down even when that cancellation is triggered by the parent
     2 nurseries "up".
-    """
+
+    Though the grandchild should stay blocking its actor runtime, its
+    parent should issue a "zombie reaper" to hard kill it after
+    sufficient timeout.
+
+    '''
     if start_method == 'forkserver':
         pytest.skip("Forksever sux hard at resuming from sync sleep...")
 
     async def main():
-        with trio.fail_after(2):
-            async with tractor.open_nursery() as tn:
-                await tn.run_in_actor(
-                    spawn,
-                    name='spawn',
+        #
+        # XXX BIG TODO NOTE XXX
+        #
+        # it seems there's a strange race that can happen
+        # where where the fail-after will trigger outer scope
+        # .cancel() which then causes the inner scope to raise,
+        #
+        # BaseExceptionGroup('Exceptions from Trio nursery', [
+        #   BaseExceptionGroup('Exceptions from Trio nursery',
+        #   [
+        #       Cancelled(),
+        #       Cancelled(),
+        #   ]
+        #   ),
+        #   AssertionError('assert 0')
+        # ])
+        #
+        # WHY THIS DOESN'T MAKE SENSE:
+        # ---------------------------
+        # - it should raise too-slow-error when too slow..
+        #  * verified that using simple-cs and manually cancelling
+        #    you get same outcome -> indicates that the fail-after
+        #    can have its TooSlowError overriden!
+        #  |_ to check this it's easy, simplly decrease the timeout
+        #     as per the var below.
+        #
+        # - when using the manual simple-cs the outcome is different
+        #   DESPITE the `assert 0` which means regardless of the
+        #   inner scope effectively failing in the same way, the
+        #   bubbling up **is NOT the same**.
+        #
+        # delays trigger diff outcomes..
+        # ---------------------------
+        # as seen by uncommenting various lines below there is from
+        # my POV an unexpected outcome due to the delay=2 case.
+        #
+        # delay = 1  # no AssertionError in eg, TooSlowError raised.
+        # delay = 2  # is AssertionError in eg AND no TooSlowError !?
+        delay = 4  # is AssertionError in eg AND no _cs cancellation.
+
+        with trio.fail_after(delay) as _cs:
+        # with trio.CancelScope() as cs:
+        # ^XXX^ can be used instead to see same outcome.
+
+            async with (
+                # tractor.trionics.collapse_eg(),  # doesn't help
+                tractor.open_nursery(
+                    hide_tb=False,
+                    debug_mode=debug_mode,
+                    registry_addrs=[reg_addr],
+                ) as an,
+            ):
+                await an.run_in_actor(
+                    spawn_sub_with_sync_blocking_task,
+                    name='sync_blocking_sub',
                 )
                 await trio.sleep(1)
+
+                if man_cancel_outer:
+                    print('Cancelling manually in root')
+                    _cs.cancel()
+
+                # trigger exc-srced taskc down
+                # the actor tree.
+                print('RAISING IN ROOT')
                 assert 0
 
     with pytest.raises(AssertionError):
diff --git a/tests/test_child_manages_service_nursery.py b/tests/test_child_manages_service_nursery.py
index 540e9b2e..6379afc6 100644
--- a/tests/test_child_manages_service_nursery.py
+++ b/tests/test_child_manages_service_nursery.py
@@ -117,9 +117,10 @@ async def open_actor_local_nursery(
     ctx: tractor.Context,
 ):
     global _nursery
-    async with trio.open_nursery(
-        strict_exception_groups=False,
-    ) as tn:
+    async with (
+        tractor.trionics.collapse_eg(),
+        trio.open_nursery() as tn
+    ):
         _nursery = tn
         await ctx.started()
         await trio.sleep(10)
diff --git a/tests/test_clustering.py b/tests/test_clustering.py
index 92362b58..603b2eb4 100644
--- a/tests/test_clustering.py
+++ b/tests/test_clustering.py
@@ -13,26 +13,24 @@ MESSAGE = 'tractoring at full speed'
 def test_empty_mngrs_input_raises() -> None:
 
     async def main():
-        with trio.fail_after(1):
+        with trio.fail_after(3):
             async with (
                 open_actor_cluster(
                     modules=[__name__],
 
                     # NOTE: ensure we can passthrough runtime opts
-                    loglevel='info',
-                    # debug_mode=True,
+                    loglevel='cancel',
+                    debug_mode=False,
 
                 ) as portals,
 
-                gather_contexts(
-                    # NOTE: it's the use of inline-generator syntax
-                    # here that causes the empty input.
-                    mngrs=(
-                        p.open_context(worker) for p in portals.values()
-                    ),
-                ),
+                gather_contexts(mngrs=()),
             ):
-                assert 0
+                # should fail before this?
+                assert portals
+
+                # test should fail if we mk it here!
+                assert 0, 'Should have raised val-err !?'
 
     with pytest.raises(ValueError):
         trio.run(main)
diff --git a/tests/test_discovery.py b/tests/test_discovery.py
index 65a76d08..453b1aa3 100644
--- a/tests/test_discovery.py
+++ b/tests/test_discovery.py
@@ -11,6 +11,7 @@ import psutil
 import pytest
 import subprocess
 import tractor
+from tractor.trionics import collapse_eg
 from tractor._testing import tractor_test
 import trio
 
@@ -193,10 +194,10 @@ async def spawn_and_check_registry(
 
             try:
                 async with tractor.open_nursery() as an:
-                    async with trio.open_nursery(
-                        strict_exception_groups=False,
-                    ) as trion:
-
+                    async with (
+                        collapse_eg(),
+                        trio.open_nursery() as trion,
+                    ):
                         portals = {}
                         for i in range(3):
                             name = f'a{i}'
@@ -338,11 +339,12 @@ async def close_chans_before_nursery(
                         async with portal2.open_stream_from(
                             stream_forever
                         ) as agen2:
-                            async with trio.open_nursery(
-                                strict_exception_groups=False,
-                            ) as n:
-                                n.start_soon(streamer, agen1)
-                                n.start_soon(cancel, use_signal, .5)
+                            async with (
+                                collapse_eg(),
+                                trio.open_nursery() as tn,
+                            ):
+                                tn.start_soon(streamer, agen1)
+                                tn.start_soon(cancel, use_signal, .5)
                                 try:
                                     await streamer(agen2)
                                 finally:
diff --git a/tests/test_infected_asyncio.py b/tests/test_infected_asyncio.py
index 195ed4cd..edd7ee47 100644
--- a/tests/test_infected_asyncio.py
+++ b/tests/test_infected_asyncio.py
@@ -234,10 +234,8 @@ async def trio_ctx(
     with trio.fail_after(1 + delay):
         try:
             async with (
-                trio.open_nursery(
-                    # TODO, for new `trio` / py3.13
-                    # strict_exception_groups=False,
-                ) as tn,
+                tractor.trionics.collapse_eg(),
+                trio.open_nursery() as tn,
                 tractor.to_asyncio.open_channel_from(
                     sleep_and_err,
                 ) as (first, chan),
diff --git a/tests/test_legacy_one_way_streaming.py b/tests/test_legacy_one_way_streaming.py
index 6092bca7..10cf3aed 100644
--- a/tests/test_legacy_one_way_streaming.py
+++ b/tests/test_legacy_one_way_streaming.py
@@ -235,10 +235,16 @@ async def cancel_after(wait, reg_addr):
 
 
 @pytest.fixture(scope='module')
-def time_quad_ex(reg_addr, ci_env, spawn_backend):
+def time_quad_ex(
+    reg_addr: tuple,
+    ci_env: bool,
+    spawn_backend: str,
+):
     if spawn_backend == 'mp':
-        """no idea but the  mp *nix runs are flaking out here often...
-        """
+        '''
+        no idea but the  mp *nix runs are flaking out here often...
+
+        '''
         pytest.skip("Test is too flaky on mp in CI")
 
     timeout = 7 if platform.system() in ('Windows', 'Darwin') else 4
@@ -249,12 +255,24 @@ def time_quad_ex(reg_addr, ci_env, spawn_backend):
     return results, diff
 
 
-def test_a_quadruple_example(time_quad_ex, ci_env, spawn_backend):
-    """This also serves as a kind of "we'd like to be this fast test"."""
+def test_a_quadruple_example(
+    time_quad_ex: tuple,
+    ci_env: bool,
+    spawn_backend: str,
+):
+    '''
+    This also serves as a kind of "we'd like to be this fast test".
 
+    '''
     results, diff = time_quad_ex
     assert results
-    this_fast = 6 if platform.system() in ('Windows', 'Darwin') else 3
+    this_fast = (
+        6 if platform.system() in (
+            'Windows',
+            'Darwin',
+        )
+        else 3
+    )
     assert diff < this_fast
 
 
diff --git a/tests/test_root_infect_asyncio.py b/tests/test_root_infect_asyncio.py
index 93deba13..78f9b2b4 100644
--- a/tests/test_root_infect_asyncio.py
+++ b/tests/test_root_infect_asyncio.py
@@ -147,8 +147,7 @@ def test_trio_prestarted_task_bubbles(
         await trio.sleep_forever()
 
     async def _trio_main():
-        # with trio.fail_after(2):
-        with trio.fail_after(999):
+        with trio.fail_after(2 if not debug_mode else 999):
             first: str
             chan: to_asyncio.LinkedTaskChannel
             aio_ev = asyncio.Event()
@@ -217,32 +216,25 @@ def test_trio_prestarted_task_bubbles(
                         ):
                             aio_ev.set()
 
-    with pytest.raises(
-        expected_exception=ExceptionGroup,
-    ) as excinfo:
-        tractor.to_asyncio.run_as_asyncio_guest(
-            trio_main=_trio_main,
-        )
-
-    eg = excinfo.value
-    rte_eg, rest_eg = eg.split(RuntimeError)
-
     # ensure the trio-task's error bubbled despite the aio-side
     # having (maybe) errored first.
     if aio_err_trigger in (
         'after_trio_task_starts',
         'after_start_point',
     ):
-        assert len(errs := rest_eg.exceptions) == 1
-        typerr = errs[0]
-        assert (
-            type(typerr) is TypeError
-            and
-            'trio-side' in typerr.args
-        )
+        patt: str = 'trio-side'
+        expect_exc = TypeError
 
     # when aio errors BEFORE (last) trio task is scheduled, we should
     # never see anythinb but the aio-side.
     else:
-        assert len(rtes := rte_eg.exceptions) == 1
-        assert 'asyncio-side' in rtes[0].args[0]
+        patt: str = 'asyncio-side'
+        expect_exc = RuntimeError
+
+    with pytest.raises(expect_exc) as excinfo:
+        tractor.to_asyncio.run_as_asyncio_guest(
+            trio_main=_trio_main,
+        )
+
+    caught_exc = excinfo.value
+    assert patt in caught_exc.args
diff --git a/tests/test_trioisms.py b/tests/test_trioisms.py
index c68d75c1..ca1e6d55 100644
--- a/tests/test_trioisms.py
+++ b/tests/test_trioisms.py
@@ -8,6 +8,7 @@ from contextlib import (
 )
 
 import pytest
+from tractor.trionics import collapse_eg
 import trio
 from trio import TaskStatus
 
@@ -64,9 +65,8 @@ def test_stashed_child_nursery(use_start_soon):
     async def main():
 
         async with (
-            trio.open_nursery(
-                strict_exception_groups=False,
-            ) as pn,
+            collapse_eg(),
+            trio.open_nursery() as pn,
         ):
             cn = await pn.start(mk_child_nursery)
             assert cn
@@ -197,10 +197,8 @@ def test_gatherctxs_with_memchan_breaks_multicancelled(
         async with (
             # XXX should ensure ONLY the KBI
             # is relayed upward
-            trionics.collapse_eg(),
-            trio.open_nursery(
-                # strict_exception_groups=False,
-            ), # as tn,
+            collapse_eg(),
+            trio.open_nursery(), # as tn,
 
             trionics.gather_contexts([
                 open_memchan(),
diff --git a/tractor/_clustering.py b/tractor/_clustering.py
index 46224d6f..dbb50304 100644
--- a/tractor/_clustering.py
+++ b/tractor/_clustering.py
@@ -55,10 +55,17 @@ async def open_actor_cluster(
         raise ValueError(
             'Number of names is {len(names)} but count it {count}')
 
-    async with tractor.open_nursery(
-        **runtime_kwargs,
-    ) as an:
-        async with trio.open_nursery() as n:
+    async with (
+        # tractor.trionics.collapse_eg(),
+        tractor.open_nursery(
+            **runtime_kwargs,
+        ) as an
+    ):
+        async with (
+            # tractor.trionics.collapse_eg(),
+            trio.open_nursery() as tn,
+            tractor.trionics.maybe_raise_from_masking_exc()
+        ):
             uid = tractor.current_actor().uid
 
             async def _start(name: str) -> None:
@@ -69,9 +76,8 @@ async def open_actor_cluster(
                 )
 
             for name in names:
-                n.start_soon(_start, name)
+                tn.start_soon(_start, name)
 
         assert len(portals) == count
         yield portals
-
         await an.cancel(hard_kill=hard_kill)
diff --git a/tractor/_context.py b/tractor/_context.py
index 61994f98..7a2bf5c6 100644
--- a/tractor/_context.py
+++ b/tractor/_context.py
@@ -101,6 +101,9 @@ from ._state import (
     debug_mode,
     _ctxvar_Context,
 )
+from .trionics import (
+    collapse_eg,
+)
 # ------ - ------
 if TYPE_CHECKING:
     from ._portal import Portal
@@ -942,7 +945,7 @@ class Context:
         self.cancel_called = True
 
         header: str = (
-            f'Cancelling ctx from {side.upper()}-side\n'
+            f'Cancelling ctx from {side!r}-side\n'
         )
         reminfo: str = (
             # ' =>\n'
@@ -950,7 +953,7 @@ class Context:
             f'\n'
             f'c)=> {self.chan.uid}\n'
             f'   |_[{self.dst_maddr}\n'
-            f'     >>{self.repr_rpc}\n'
+            f'     >> {self.repr_rpc}\n'
             # f'    >> {self._nsf}() -> {codec}[dict]:\n\n'
             # TODO: pull msg-type from spec re #320
         )
@@ -2025,10 +2028,8 @@ async def open_context_from_portal(
     ctxc_from_callee: ContextCancelled|None = None
     try:
         async with (
-            trio.open_nursery(
-                strict_exception_groups=False,
-            ) as tn,
-
+            collapse_eg(),
+            trio.open_nursery() as tn,
             msgops.maybe_limit_plds(
                 ctx=ctx,
                 spec=ctx_meta.get('pld_spec'),
diff --git a/tractor/_discovery.py b/tractor/_discovery.py
index f6b3b585..a332ab73 100644
--- a/tractor/_discovery.py
+++ b/tractor/_discovery.py
@@ -28,7 +28,10 @@ from typing import (
 from contextlib import asynccontextmanager as acm
 
 from tractor.log import get_logger
-from .trionics import gather_contexts
+from .trionics import (
+    gather_contexts,
+    collapse_eg,
+)
 from .ipc import _connect_chan, Channel
 from ._addr import (
     UnwrappedAddress,
@@ -87,7 +90,6 @@ async def get_registry(
             yield regstr_ptl
 
 
-
 @acm
 async def get_root(
     **kwargs,
@@ -253,9 +255,12 @@ async def find_actor(
         for addr in registry_addrs
     )
     portals: list[Portal]
-    async with gather_contexts(
-        mngrs=maybe_portals,
-    ) as portals:
+    async with (
+        collapse_eg(),
+        gather_contexts(
+            mngrs=maybe_portals,
+        ) as portals,
+    ):
         # log.runtime(
         #     'Gathered portals:\n'
         #     f'{portals}'
diff --git a/tractor/_portal.py b/tractor/_portal.py
index 659ddf6d..5729edd4 100644
--- a/tractor/_portal.py
+++ b/tractor/_portal.py
@@ -39,7 +39,10 @@ import warnings
 
 import trio
 
-from .trionics import maybe_open_nursery
+from .trionics import (
+    maybe_open_nursery,
+    collapse_eg,
+)
 from ._state import (
     current_actor,
 )
@@ -583,14 +586,13 @@ async def open_portal(
     assert actor
     was_connected: bool = False
 
-    async with maybe_open_nursery(
-        tn,
-        shield=shield,
-        strict_exception_groups=False,
-        # ^XXX^ TODO? soo roll our own then ??
-        # -> since we kinda want the "if only one `.exception` then
-        # just raise that" interface?
-    ) as tn:
+    async with (
+        collapse_eg(),
+        maybe_open_nursery(
+            tn,
+            shield=shield,
+        ) as tn,
+    ):
 
         if not channel.connected():
             await channel.connect()
diff --git a/tractor/_root.py b/tractor/_root.py
index 16d70b98..370798dd 100644
--- a/tractor/_root.py
+++ b/tractor/_root.py
@@ -37,13 +37,7 @@ import warnings
 
 import trio
 
-from ._runtime import (
-    Actor,
-    Arbiter,
-    # TODO: rename and make a non-actor subtype?
-    # Arbiter as Registry,
-    async_main,
-)
+from . import _runtime
 from .devx import (
     debug,
     _frame_stack,
@@ -64,6 +58,7 @@ from ._addr import (
 )
 from .trionics import (
     is_multi_cancelled,
+    collapse_eg,
 )
 from ._exceptions import (
     RuntimeFailure,
@@ -102,7 +97,7 @@ async def maybe_block_bp(
     ):
         logger.info(
             f'Found `greenback` installed @ {maybe_mod}\n'
-            'Enabling `tractor.pause_from_sync()` support!\n'
+            f'Enabling `tractor.pause_from_sync()` support!\n'
         )
         os.environ['PYTHONBREAKPOINT'] = (
             'tractor.devx.debug._sync_pause_from_builtin'
@@ -197,9 +192,13 @@ async def open_root_actor(
     # read-only state to sublayers?
     # extra_rt_vars: dict|None = None,
 
-) -> Actor:
+) -> _runtime.Actor:
     '''
-    Runtime init entry point for ``tractor``.
+    Initialize the `tractor` runtime by starting a "root actor" in
+    a parent-most Python process.
+
+    All (disjoint) actor-process-trees-as-programs are created via
+    this entrypoint.
 
     '''
     # XXX NEVER allow nested actor-trees!
@@ -397,7 +396,7 @@ async def open_root_actor(
                 f'Registry(s) seem(s) to exist @ {ponged_addrs}'
             )
 
-            actor = Actor(
+            actor = _runtime.Actor(
                 name=name or 'anonymous',
                 uuid=mk_uuid(),
                 registry_addrs=ponged_addrs,
@@ -436,7 +435,8 @@ async def open_root_actor(
             # https://github.com/goodboy/tractor/pull/348
             # https://github.com/goodboy/tractor/issues/296
 
-            actor = Arbiter(
+            # TODO: rename as `RootActor` or is that even necessary?
+            actor = _runtime.Arbiter(
                 name=name or 'registrar',
                 uuid=mk_uuid(),
                 registry_addrs=registry_addrs,
@@ -471,18 +471,21 @@ async def open_root_actor(
                     '-> Opening new registry @ '
                     +
                     '\n'.join(
-                        f'@{addr}' for addr in reg_addrs
+                        f'{addr}' for addr in reg_addrs
                     )
                 )
             logger.info(f'{report}\n')
 
-            # start the actor runtime in a new task
-            async with trio.open_nursery(
-                strict_exception_groups=False,
-                # ^XXX^ TODO? instead unpack any RAE as per "loose" style?
-            ) as nursery:
+            # start runtime in a bg sub-task, yield to caller.
+            async with (
+                collapse_eg(),
+                trio.open_nursery() as root_tn,
 
-                # ``_runtime.async_main()`` creates an internal nursery
+                # XXX, finally-footgun below?
+                # -> see note on why shielding.
+                # maybe_raise_from_masking_exc(),
+            ):
+                # `_runtime.async_main()` creates an internal nursery
                 # and blocks here until any underlying actor(-process)
                 # tree has terminated thereby conducting so called
                 # "end-to-end" structured concurrency throughout an
@@ -490,9 +493,9 @@ async def open_root_actor(
                 # "actor runtime" primitives are SC-compat and thus all
                 # transitively spawned actors/processes must be as
                 # well.
-                await nursery.start(
+                await root_tn.start(
                     partial(
-                        async_main,
+                        _runtime.async_main,
                         actor,
                         accept_addrs=trans_bind_addrs,
                         parent_addr=None
@@ -540,7 +543,7 @@ async def open_root_actor(
                     raise
 
                 finally:
-                    # NOTE: not sure if we'll ever need this but it's
+                    # NOTE/TODO?, not sure if we'll ever need this but it's
                     # possibly better for even more determinism?
                     # logger.cancel(
                     #     f'Waiting on {len(nurseries)} nurseries in root..')
diff --git a/tractor/_rpc.py b/tractor/_rpc.py
index 2bd4d6e3..eb1df2cc 100644
--- a/tractor/_rpc.py
+++ b/tractor/_rpc.py
@@ -765,7 +765,6 @@ async def _invoke(
             BaseExceptionGroup,
             BaseException,
             trio.Cancelled,
-
         ) as _scope_err:
             scope_err = _scope_err
             if (
diff --git a/tractor/_runtime.py b/tractor/_runtime.py
index bc915b85..ef7a3018 100644
--- a/tractor/_runtime.py
+++ b/tractor/_runtime.py
@@ -74,6 +74,9 @@ from tractor.msg import (
     pretty_struct,
     types as msgtypes,
 )
+from .trionics import (
+    collapse_eg,
+)
 from .ipc import (
     Channel,
     # IPCServer,  # causes cycles atm..
@@ -359,7 +362,7 @@ class Actor:
 
     def pformat(
         self,
-        ds: str = ':',
+        ds: str = ': ',
         indent: int = 0,
         privates: bool = False,
     ) -> str:
@@ -1471,17 +1474,18 @@ async def async_main(
         # parent is kept alive as a resilient service until
         # cancellation steps have (mostly) occurred in
         # a deterministic way.
-        async with trio.open_nursery(
-            strict_exception_groups=False,
-        ) as root_nursery:
-            actor._root_n = root_nursery
+        root_tn: trio.Nursery
+        async with (
+            collapse_eg(),
+            trio.open_nursery() as root_tn,
+        ):
+            actor._root_n = root_tn
             assert actor._root_n
 
             ipc_server: _server.IPCServer
             async with (
-                trio.open_nursery(
-                    strict_exception_groups=False,
-                ) as service_nursery,
+                collapse_eg(),
+                trio.open_nursery() as service_nursery,
                 _server.open_ipc_server(
                     parent_tn=service_nursery,
                     stream_handler_tn=service_nursery,
@@ -1605,7 +1609,7 @@ async def async_main(
                 # start processing parent requests until our channel
                 # server is 100% up and running.
                 if actor._parent_chan:
-                    await root_nursery.start(
+                    await root_tn.start(
                         partial(
                             _rpc.process_messages,
                             chan=actor._parent_chan,
@@ -1756,9 +1760,7 @@ async def async_main(
                 f'   {pformat(ipc_server._peers)}'
             )
             log.runtime(teardown_report)
-            await ipc_server.wait_for_no_more_peers(
-                shield=True,
-            )
+            await ipc_server.wait_for_no_more_peers()
 
         teardown_report += (
             '-]> all peer channels are complete.\n'
diff --git a/tractor/_supervise.py b/tractor/_supervise.py
index 9fdad8ce..ec2b1864 100644
--- a/tractor/_supervise.py
+++ b/tractor/_supervise.py
@@ -44,6 +44,7 @@ from ._runtime import Actor
 from ._portal import Portal
 from .trionics import (
     is_multi_cancelled,
+    collapse_eg,
 )
 from ._exceptions import (
     ContextCancelled,
@@ -326,9 +327,10 @@ class ActorNursery:
         server: IPCServer = self._actor.ipc_server
 
         with trio.move_on_after(3) as cs:
-            async with trio.open_nursery(
-                strict_exception_groups=False,
-            ) as tn:
+            async with (
+                collapse_eg(),
+                trio.open_nursery() as tn,
+            ):
 
                 subactor: Actor
                 proc: trio.Process
@@ -421,10 +423,10 @@ async def _open_and_supervise_one_cancels_all_nursery(
     # `ActorNursery.start_actor()`).
 
     # errors from this daemon actor nursery bubble up to caller
-    async with trio.open_nursery(
-        strict_exception_groups=False,
-        # ^XXX^ TODO? instead unpack any RAE as per "loose" style?
-    ) as da_nursery:
+    async with (
+        collapse_eg(),
+        trio.open_nursery() as da_nursery,
+    ):
         try:
             # This is the inner level "run in actor" nursery. It is
             # awaited first since actors spawned in this way (using
@@ -434,11 +436,10 @@ async def _open_and_supervise_one_cancels_all_nursery(
             # immediately raised for handling by a supervisor strategy.
             # As such if the strategy propagates any error(s) upwards
             # the above "daemon actor" nursery will be notified.
-            async with trio.open_nursery(
-                strict_exception_groups=False,
-                # ^XXX^ TODO? instead unpack any RAE as per "loose" style?
-            ) as ria_nursery:
-
+            async with (
+                collapse_eg(),
+                trio.open_nursery() as ria_nursery,
+            ):
                 an = ActorNursery(
                     actor,
                     ria_nursery,
diff --git a/tractor/ipc/_server.py b/tractor/ipc/_server.py
index e857db19..46fde2fc 100644
--- a/tractor/ipc/_server.py
+++ b/tractor/ipc/_server.py
@@ -814,10 +814,14 @@ class Server(Struct):
 
     async def wait_for_no_more_peers(
         self,
-        shield: bool = False,
+        # XXX, should this even be allowed?
+        # -> i've seen it cause hangs on teardown
+        #    in `test_resource_cache.py`
+        # _shield: bool = False,
     ) -> None:
-        with trio.CancelScope(shield=shield):
-            await self._no_more_peers.wait()
+        await self._no_more_peers.wait()
+        # with trio.CancelScope(shield=_shield):
+        #     await self._no_more_peers.wait()
 
     async def wait_for_peer(
         self,
diff --git a/tractor/trionics/__init__.py b/tractor/trionics/__init__.py
index afd1f434..2e91aa30 100644
--- a/tractor/trionics/__init__.py
+++ b/tractor/trionics/__init__.py
@@ -31,7 +31,7 @@ from ._broadcast import (
 )
 from ._beg import (
     collapse_eg as collapse_eg,
-    maybe_collapse_eg as maybe_collapse_eg,
+    get_collapsed_eg as get_collapsed_eg,
     is_multi_cancelled as is_multi_cancelled,
 )
 from ._taskc import (
diff --git a/tractor/trionics/_beg.py b/tractor/trionics/_beg.py
index ad10f3bf..f466ab3c 100644
--- a/tractor/trionics/_beg.py
+++ b/tractor/trionics/_beg.py
@@ -15,8 +15,9 @@
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 '''
-`BaseExceptionGroup` related utils and helpers pertaining to
-first-class-`trio` from a historical perspective B)
+`BaseExceptionGroup` utils and helpers pertaining to
+first-class-`trio` from a "historical" perspective, like "loose
+exception group" task-nurseries.
 
 '''
 from contextlib import (
@@ -24,27 +25,84 @@ from contextlib import (
 )
 from typing import (
     Literal,
+    Type,
 )
 
 import trio
+# from trio._core._concat_tb import (
+#     concat_tb,
+# )
 
 
-def maybe_collapse_eg(
-    beg: BaseExceptionGroup,
+# XXX NOTE
+# taken verbatim from `trio._core._run` except,
+# - remove the NONSTRICT_EXCEPTIONGROUP_NOTE deprecation-note
+#   guard-check; we know we want an explicit collapse.
+# - mask out tb rewriting in collapse case, i don't think it really
+#   matters?
+#
+def collapse_exception_group(
+    excgroup: BaseExceptionGroup[BaseException],
 ) -> BaseException:
+    """Recursively collapse any single-exception groups into that single contained
+    exception.
+
+    """
+    exceptions = list(excgroup.exceptions)
+    modified = False
+    for i, exc in enumerate(exceptions):
+        if isinstance(exc, BaseExceptionGroup):
+            new_exc = collapse_exception_group(exc)
+            if new_exc is not exc:
+                modified = True
+                exceptions[i] = new_exc
+
+    if (
+        len(exceptions) == 1
+        and isinstance(excgroup, BaseExceptionGroup)
+
+        # XXX trio's loose-setting condition..
+        # and NONSTRICT_EXCEPTIONGROUP_NOTE in getattr(excgroup, "__notes__", ())
+    ):
+        # exceptions[0].__traceback__ = concat_tb(
+        #     excgroup.__traceback__,
+        #     exceptions[0].__traceback__,
+        # )
+        return exceptions[0]
+    elif modified:
+        return excgroup.derive(exceptions)
+    else:
+        return excgroup
+
+
+def get_collapsed_eg(
+    beg: BaseExceptionGroup,
+
+) -> BaseException|None:
     '''
-    If the input beg can collapse to a single non-eg sub-exception,
-    return it instead.
+    If the input beg can collapse to a single sub-exception which is
+    itself **not** an eg, return it.
 
     '''
-    if len(excs := beg.exceptions) == 1:
-        return excs[0]
+    maybe_exc = collapse_exception_group(beg)
+    if maybe_exc is beg:
+        return None
 
-    return beg
+    return maybe_exc
 
 
 @acm
-async def collapse_eg():
+async def collapse_eg(
+    hide_tb: bool = True,
+
+    # XXX, for ex. will always show begs containing single taskc
+    ignore: set[Type[BaseException]] = {
+        # trio.Cancelled,
+    },
+    add_notes: bool = True,
+
+    bp: bool = False,
+):
     '''
     If `BaseExceptionGroup` raised in the body scope is
     "collapse-able" (in the same way that
@@ -52,15 +110,58 @@ async def collapse_eg():
     only raise the lone emedded non-eg in in place.
 
     '''
+    __tracebackhide__: bool = hide_tb
     try:
         yield
-    except* BaseException as beg:
-        if (
-            exc := maybe_collapse_eg(beg)
-        ) is not beg:
-            raise exc
+    except BaseExceptionGroup as _beg:
+        beg = _beg
 
-        raise beg
+        if (
+            bp
+            and
+            len(beg.exceptions) > 1
+        ):
+            import tractor
+            if tractor.current_actor(
+                err_on_no_runtime=False,
+            ):
+                await tractor.pause(shield=True)
+            else:
+                breakpoint()
+
+        if (
+            (exc := get_collapsed_eg(beg))
+            and
+            type(exc) not in ignore
+        ):
+
+            # TODO? report number of nested groups it was collapsed
+            # *from*?
+            if add_notes:
+                from_group_note: str = (
+                    '( ^^^ this exc was collapsed from a group ^^^ )\n'
+                )
+                if (
+                    from_group_note
+                    not in
+                    getattr(exc, "__notes__", ())
+                ):
+                    exc.add_note(from_group_note)
+
+            # raise exc
+            # ^^ this will leave the orig beg tb above with the
+            # "during the handling of <beg> the following.."
+            # So, instead do..
+            #
+            if cause := exc.__cause__:
+                raise exc from cause
+            else:
+                # suppress "during handling of <the beg>"
+                # output in tb/console.
+                raise exc from None
+
+        # keep original
+        raise # beg
 
 
 def is_multi_cancelled(