diff --git a/devlib/utils/asyn.py b/devlib/utils/asyn.py
index b3fe889..fd518d9 100644
--- a/devlib/utils/asyn.py
+++ b/devlib/utils/asyn.py
@@ -20,23 +20,20 @@ Async-related utilities
 
 import abc
 import asyncio
+import contextvars
 import functools
 import itertools
 import contextlib
 import pathlib
+import queue
 import os.path
 import inspect
+import sys
+import threading
+from concurrent.futures import ThreadPoolExecutor
+from weakref import WeakSet, WeakKeyDictionary
 
-# Allow nesting asyncio loops, which is necessary for:
-# * Being able to call the blocking variant of a function from an async
-#   function for backward compat
-# * Critically, run the blocking variant of a function in a Jupyter notebook
-#   environment, since it also uses asyncio.
-#
-# Maybe there is still hope for future versions of Python though:
-# https://bugs.python.org/issue22239
-import nest_asyncio
-nest_asyncio.apply()
+from greenlet import greenlet
 
 
 def create_task(awaitable, name=None):
@@ -50,6 +47,20 @@ def create_task(awaitable, name=None):
     return task
 
 
+def _close_loop(loop):
+    if loop is not None:
+        try:
+            loop.run_until_complete(loop.shutdown_asyncgens())
+            try:
+                shutdown_default_executor = loop.shutdown_default_executor
+            except AttributeError:
+                pass
+            else:
+                loop.run_until_complete(shutdown_default_executor())
+        finally:
+            loop.close()
+
+
 class AsyncManager:
     def __init__(self):
         self.task_tree = dict()
@@ -292,12 +303,459 @@ class memoized_method:
         self._name = name
 
 
+class _Genlet(greenlet):
+    """
+    Generator-like object based on ``greenlets``. It allows nested :class:`_Genlet`
+    to make their parent yield on their behalf, as if callees could decide to
+    be annotated ``yield from`` without modifying the caller.
+    """
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+        # Forward the context variables to the greenlet, which will not happen
+        # by default:
+        # https://greenlet.readthedocs.io/en/latest/contextvars.html
+        self.gr_context = contextvars.copy_context()
+
+    @classmethod
+    def from_coro(cls, coro):
+        """
+        Create a :class:`_Genlet` from a given coroutine, treating it as a
+        generator.
+        """
+        f = lambda value: self.consume_coro(coro, value)
+        self = cls(f)
+        return self
+
+    def consume_coro(self, coro, value):
+        """
+        Send ``value`` to ``coro`` then consume the coroutine, passing all its
+        yielded actions to the enclosing :class:`_Genlet`. This allows crossing
+        blocking calls layers as if they were async calls with `await`.
+        """
+        excep = None
+        while True:
+            try:
+                if excep is None:
+                    future = coro.send(value)
+                else:
+                    future = coro.throw(excep)
+
+            except StopIteration as e:
+                return e.value
+            else:
+                parent = self.parent
+                # Switch back to the consumer that returns the values via
+                # send()
+                try:
+                    value = parent.switch(future)
+                except BaseException as e:
+                    excep = e
+                    value = None
+                else:
+                    excep = None
+
+    @classmethod
+    def get_enclosing(cls):
+        """
+        Get the immediately enclosing :class:`_Genlet` in the callstack or
+        ``None``.
+        """
+        g = greenlet.getcurrent()
+        while not (isinstance(g, cls) or g is None):
+            g = g.parent
+        return g
+
+    def _send_throw(self, value, excep):
+        self.parent = greenlet.getcurrent()
+
+        # Switch back to the function yielding values
+        if excep is None:
+            result = self.switch(value)
+        else:
+            result = self.throw(excep)
+
+        if self:
+            return result
+        else:
+            raise StopIteration(result)
+
+    def gen_send(self, x):
+        """
+        Similar to generators' ``send`` method.
+        """
+        return self._send_throw(x, None)
+
+    def gen_throw(self, x):
+        """
+        Similar to generators' ``throw`` method.
+        """
+        return self._send_throw(None, x)
+
+
+class _AwaitableGenlet:
+    """
+    Wrap a coroutine with a :class:`_Genlet` and wrap that to be awaitable.
+    """
+
+    @classmethod
+    def wrap_coro(cls, coro):
+        async def coro_f():
+            # Make sure every new task will be instrumented since a task cannot
+            # yield futures on behalf of another task. If that were to happen,
+            # the task B trying to do a nested yield would switch back to task
+            # A, asking to yield on its behalf. Since the event loop would be
+            # currently handling task B, nothing would handle task A trying to
+            # yield on behalf of B, leading to a deadlock.
+            loop = asyncio.get_running_loop()
+            _install_task_factory(loop)
+
+            # Create a top-level _AwaitableGenlet that all nested runs will use
+            # to yield their futures
+            _coro = cls(coro)
+
+            return await _coro
+
+        return coro_f()
+
+    def __init__(self, coro):
+        self._coro = coro
+
+    def __await__(self):
+        coro = self._coro
+        is_started = inspect.iscoroutine(coro) and coro.cr_running
+
+        def genf():
+            gen = _Genlet.from_coro(coro)
+            value = None
+            excep = None
+
+            # The coroutine is already started, so we need to dispatch the
+            # value from the upcoming send() to the gen without running
+            # gen first.
+            if is_started:
+                try:
+                    value = yield
+                except BaseException as e:
+                    excep = e
+
+            while True:
+                try:
+                    if excep is None:
+                        future = gen.gen_send(value)
+                    else:
+                        future = gen.gen_throw(excep)
+                except StopIteration as e:
+                    return e.value
+                finally:
+                    _set_current_context(gen.gr_context)
+
+                try:
+                    value = yield future
+                except BaseException as e:
+                    excep = e
+                    value = None
+                else:
+                    excep = None
+
+        gen = genf()
+        if is_started:
+            # Start the generator so it waits at the first yield point
+            gen.gen_send(None)
+
+        return gen
+
+
+def _allow_nested_run(coro):
+    if _Genlet.get_enclosing() is None:
+        return _AwaitableGenlet.wrap_coro(coro)
+    else:
+        return coro
+
+
+def allow_nested_run(coro):
+    """
+    Wrap the coroutine ``coro`` such that nested calls to :func:`run` will be
+    allowed.
+
+    .. warning:: The coroutine needs to be consumed in the same OS thread it
+        was created in.
+    """
+    return _allow_nested_run(coro)
+
+
+# This thread runs coroutines that cannot be ran on the event loop in the
+# current thread. Instead, they are scheduled in a separate thread where
+# another event loop has been setup, so we can wrap coroutines before
+# dispatching them there.
+_CORO_THREAD_EXECUTOR = ThreadPoolExecutor(
+    # Allow for a ridiculously large number so that we will never end up
+    # queuing one job after another. This is critical as we could otherwise end
+    # up in deadlock, if a job triggers another job and waits for it.
+    max_workers=2**64,
+)
+
+
+def _check_executor_alive(executor):
+    try:
+        executor.submit(lambda: None)
+    except RuntimeError:
+        return False
+    else:
+        return True
+
+
+_PATCHED_LOOP_LOCK = threading.Lock()
+_PATCHED_LOOP = WeakSet()
+def _install_task_factory(loop):
+    """
+    Install a task factory on the given event ``loop`` so that top-level
+    coroutines are wrapped using :func:`allow_nested_run`. This ensures that
+    the nested :func:`run` infrastructure will be available.
+    """
+    def install(loop):
+        if sys.version_info >= (3, 11):
+            def default_factory(loop, coro, context=None):
+                return asyncio.Task(coro, loop=loop, context=context)
+        else:
+            def default_factory(loop, coro, context=None):
+                return asyncio.Task(coro, loop=loop)
+
+        make_task = loop.get_task_factory() or default_factory
+        def factory(loop, coro, context=None):
+            # Make sure each Task will be able to yield on behalf of its nested
+            # await beneath blocking layers
+            coro = _AwaitableGenlet.wrap_coro(coro)
+            return make_task(loop, coro, context=context)
+
+        loop.set_task_factory(factory)
+
+    with _PATCHED_LOOP_LOCK:
+        if loop in _PATCHED_LOOP:
+            return
+        else:
+            install(loop)
+            _PATCHED_LOOP.add(loop)
+
+
+def _set_current_context(ctx):
+    """
+    Get all the variable from the passed ``ctx`` and set them in the current
+    context.
+    """
+    for var, val in ctx.items():
+        var.set(val)
+
+
+class _CoroRunner(abc.ABC):
+    """
+    ABC for an object that can execute multiple coroutines in a given
+    environment.
+
+    This allows running coroutines for which it might be an assumption, such as
+    the awaitables yielded by an async generator that are all attached to a
+    single event loop.
+    """
+    @abc.abstractmethod
+    def _run(self, coro):
+        pass
+
+    def run(self, coro):
+        # Ensure we have a fresh coroutine. inspect.getcoroutinestate() does not
+        # work on all objects that asyncio creates on some version of Python, such
+        # as iterable_coroutine
+        assert not (inspect.iscoroutine(coro) and coro.cr_running)
+        return self._run(coro)
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_value, tb):
+        pass
+
+
+class _ThreadCoroRunner(_CoroRunner):
+    """
+    Run the coroutines on a thread picked from a
+    :class:`concurrent.futures.ThreadPoolExecutor`.
+
+    Critically, this allows running multiple coroutines out of the same thread,
+    which will be reserved until the runner ``__exit__`` method is called.
+    """
+    def __init__(self, future, jobq, resq):
+        self._future = future
+        self._jobq = jobq
+        self._resq = resq
+
+    @staticmethod
+    def _thread_f(jobq, resq):
+        def handle_jobs(runner):
+            while True:
+                job = jobq.get()
+                if job is None:
+                    return
+                else:
+                    ctx, coro = job
+                    try:
+                        value = ctx.run(runner.run, coro)
+                    except BaseException as e:
+                        value = None
+                        excep = e
+                    else:
+                        excep = None
+
+                    resq.put((ctx, excep, value))
+
+        with _LoopCoroRunner(None) as runner:
+            handle_jobs(runner)
+
+    @classmethod
+    def from_executor(cls, executor):
+        jobq = queue.SimpleQueue()
+        resq = queue.SimpleQueue()
+
+        try:
+            future = executor.submit(cls._thread_f, jobq, resq)
+        except RuntimeError as e:
+            if _check_executor_alive(executor):
+                raise e
+            else:
+                raise RuntimeError('Devlib relies on nested asyncio implementation requiring threads. These threads are not available while shutting down the interpreter.')
+
+        return cls(
+            jobq=jobq,
+            resq=resq,
+            future=future,
+        )
+
+    def _run(self, coro):
+        ctx = contextvars.copy_context()
+        self._jobq.put((ctx, coro))
+        ctx, excep, value = self._resq.get()
+
+        _set_current_context(ctx)
+
+        if excep is None:
+            return value
+        else:
+            raise excep
+
+    def __exit__(self, *args, **kwargs):
+        self._jobq.put(None)
+        self._future.result()
+
+
+class _LoopCoroRunner(_CoroRunner):
+    """
+    Run a coroutine on the given event loop.
+
+    The passed event loop is assumed to not be running. If ``None`` is passed,
+    a new event loop will be created in ``__enter__`` and closed in
+    ``__exit__``.
+    """
+    def __init__(self, loop):
+        self.loop = loop
+        self._owned = False
+
+    def _run(self, coro):
+        loop = self.loop
+
+        # Back-propagate the contextvars that could have been modified by the
+        # coroutine. This could be handled by asyncio.Runner().run(...,
+        # context=...) or loop.create_task(..., context=...) but these APIs are
+        # only available since Python 3.11
+        ctx = None
+        async def capture_ctx():
+            nonlocal ctx
+            try:
+                return await _allow_nested_run(coro)
+            finally:
+                ctx = contextvars.copy_context()
+
+        try:
+            return loop.run_until_complete(capture_ctx())
+        finally:
+            _set_current_context(ctx)
+
+    def __enter__(self):
+        loop = self.loop
+        if loop is None:
+            owned = True
+            loop = asyncio.new_event_loop()
+        else:
+            owned = False
+
+        asyncio.set_event_loop(loop)
+
+        self.loop = loop
+        self._owned = owned
+        return self
+
+    def __exit__(self, *args, **kwargs):
+        if self._owned:
+            asyncio.set_event_loop(None)
+            _close_loop(self.loop)
+
+
+class _GenletCoroRunner(_CoroRunner):
+    """
+    Run a coroutine assuming one of the parent coroutines was wrapped with
+    :func:`allow_nested_run`.
+    """
+    def __init__(self, g):
+        self._g = g
+
+    def _run(self, coro):
+        return self._g.consume_coro(coro, None)
+
+
+def _get_runner():
+    executor = _CORO_THREAD_EXECUTOR
+    g = _Genlet.get_enclosing()
+    try:
+        loop = asyncio.get_running_loop()
+    except RuntimeError:
+        loop = None
+
+    # We have an coroutine wrapped with allow_nested_run() higher in the
+    # callstack, that we will be able to use as a conduit to yield the
+    # futures.
+    if g is not None:
+        return _GenletCoroRunner(g)
+    # No event loop setup, so we can just make our own
+    elif loop is None:
+        return _LoopCoroRunner(None)
+    # There is an event loop setup, but it is not currently running so we
+    # can just re-use it.
+    #
+    # TODO: for now, this path is dead since asyncio.get_running_loop() will
+    # always raise a RuntimeError if the loop is not running, even if
+    # asyncio.set_event_loop() was used.
+    elif not loop.is_running():
+        return _LoopCoroRunner(loop)
+    # There is an event loop currently running in our thread, so we cannot
+    # just create another event loop and install it since asyncio forbids
+    # that. The only choice is doing this in a separate thread that we
+    # fully control.
+    else:
+        return _ThreadCoroRunner.from_executor(executor)
+
+
 def run(coro):
     """
     Similar to :func:`asyncio.run` but can be called while an event loop is
-    running.
+    running if a coroutine higher in the callstack has been wrapped using
+    :func:`allow_nested_run`.
+
+    Note that context variables from :mod:`contextvars` will be available in
+    the coroutine, and unlike with :func:`asyncio.run`, any update to them will
+    be reflected in the context of the caller. This allows context variable
+    updates to cross an arbitrary number of run layers, as if all those layers
+    were just part of the same coroutine.
     """
-    return asyncio.run(coro)
+    runner = _get_runner()
+    with runner as runner:
+        return runner.run(coro)
 
 
 def asyncf(f):
@@ -351,13 +809,65 @@ def asyncf(f):
     )
 
 
+class _AsyncPolymorphicCMState:
+    def __init__(self):
+        self.nesting = 0
+        self.runner = None
+
+    def _update_nesting(self, n):
+        x = self.nesting
+        assert x >= 0
+        x = x + n
+        self.nesting = x
+        return bool(x)
+
+    def _get_runner(self):
+        runner = self.runner
+        if runner is None:
+            assert not self.nesting
+            runner = _get_runner()
+            runner.__enter__()
+        self.runner = runner
+        return runner
+
+    def _cleanup_runner(self, force=False):
+        def cleanup():
+            self.runner = None
+            if runner is not None:
+                runner.__exit__(None, None, None)
+
+        runner = self.runner
+        if force:
+            cleanup()
+        else:
+            assert runner is not None
+            if not self._update_nesting(0):
+                cleanup()
+
+
 class _AsyncPolymorphicCM:
     """
     Wrap an async context manager such that it exposes a synchronous API as
     well for backward compatibility.
     """
+
     def __init__(self, async_cm):
         self.cm = async_cm
+        self._state = threading.local()
+
+    def _get_state(self):
+        try:
+            return self._state.x
+        except AttributeError:
+            state = _AsyncPolymorphicCMState()
+            self._state.x = state
+            return state
+
+    def _delete_state(self):
+        try:
+            del self._state.x
+        except AttributeError:
+            pass
 
     def __aenter__(self, *args, **kwargs):
         return self.cm.__aenter__(*args, **kwargs)
@@ -365,11 +875,39 @@ class _AsyncPolymorphicCM:
     def __aexit__(self, *args, **kwargs):
         return self.cm.__aexit__(*args, **kwargs)
 
+    @staticmethod
+    def _exit(state):
+        state._update_nesting(-1)
+        state._cleanup_runner()
+
     def __enter__(self, *args, **kwargs):
-        return run(self.cm.__aenter__(*args, **kwargs))
+        state = self._get_state()
+        runner = state._get_runner()
+
+        # Increase the nesting count _before_ we start running the
+        # coroutine, in case it is a recursive context manager
+        state._update_nesting(1)
+
+        try:
+            coro = self.cm.__aenter__(*args, **kwargs)
+            return runner.run(coro)
+        except BaseException:
+            self._exit(state)
+            raise
 
     def __exit__(self, *args, **kwargs):
-        return run(self.cm.__aexit__(*args, **kwargs))
+        coro = self.cm.__aexit__(*args, **kwargs)
+
+        state = self._get_state()
+        runner = state._get_runner()
+
+        try:
+            return runner.run(coro)
+        finally:
+            self._exit(state)
+
+    def __del__(self):
+        self._get_state()._cleanup_runner(force=True)
 
 
 def asynccontextmanager(f):
diff --git a/setup.py b/setup.py
index 7447af3..cba25a2 100644
--- a/setup.py
+++ b/setup.py
@@ -105,6 +105,7 @@ params = dict(
         'pytest',
         'lxml', # More robust xml parsing
         'nest_asyncio', # Allows running nested asyncio loops
+        'greenlet', # Allows running nested asyncio loops
         'future', # for the "past" Python package
         'ruamel.yaml >= 0.15.72', # YAML formatted config parsing
     ],
diff --git a/tests/test_asyn.py b/tests/test_asyn.py
index 7dddce2..8fe9a22 100644
--- a/tests/test_asyn.py
+++ b/tests/test_asyn.py
@@ -17,6 +17,7 @@
 import sys
 import asyncio
 from functools import partial
+import contextvars
 from concurrent.futures import ThreadPoolExecutor
 from contextlib import contextmanager