diff --git a/src/debugpy/adapter/__main__.py b/src/debugpy/adapter/__main__.py
index a6705c069..204622a85 100644
--- a/src/debugpy/adapter/__main__.py
+++ b/src/debugpy/adapter/__main__.py
@@ -12,6 +12,7 @@
 # WARNING: debugpy and submodules must not be imported on top level in this module,
 # and should be imported locally inside main() instead.
 
+_CAN_DAEMONIZE = os.name == "posix" and hasattr(os, "fork")
 
 def main():
     args = _parse_argv(sys.argv)
@@ -31,12 +32,13 @@ def main():
         if os.name == "posix":
             # On POSIX, we need to leave the process group and its session, and then
             # daemonize properly by double-forking (first fork already happened when
-            # this process was spawned).
+            # this process was spawned). Some POSIX runtimes, such as GraalPy, do not
+            # implement fork(), so in that case we settle for a single detached child.
             # NOTE: if process is already the session leader, then
             # setsid would fail with `operation not permitted`
             if os.getsid(os.getpid()) != os.getpid():
                 os.setsid()
-            if os.fork() != 0:
+            if _CAN_DAEMONIZE and os.fork() != 0:
                 sys.exit(0)
 
         for stdio in sys.stdin, sys.stdout, sys.stderr:
diff --git a/src/debugpy/launcher/debuggee.py b/src/debugpy/launcher/debuggee.py
index ec0c9eff1..464cac1af 100644
--- a/src/debugpy/launcher/debuggee.py
+++ b/src/debugpy/launcher/debuggee.py
@@ -58,9 +58,12 @@ def spawn(process_name, cmdline, env, redirect_output):
         else:
             kwargs = {}
 
-        if sys.platform != "win32" and sys.implementation.name != 'graalpy':
-            # GraalPy does not support running code between fork and exec
+        # GraalPy does not support running code between fork and exec, but supports the
+        # process_group argument for Popen
+        if sys.platform != "win32" and sys.implementation.name == "graalpy":
+            kwargs.update(process_group=0)
 
+        if sys.platform != "win32" and sys.implementation.name != 'graalpy':
             def preexec_fn():
                 try:
                     # Start the debuggee in a new process group, so that the launcher can
diff --git a/src/debugpy/server/api.py b/src/debugpy/server/api.py
index 81356783b..28795fa37 100644
--- a/src/debugpy/server/api.py
+++ b/src/debugpy/server/api.py
@@ -17,6 +17,7 @@
 from debugpy.common.util import hide_debugpy_internals
 
 _tls = threading.local()
+_CAN_DAEMONIZE = os.name == "posix" and hasattr(os, "fork")
 
 # TODO: "gevent", if possible.
 _config = {
@@ -218,9 +219,11 @@ def listen(address, settrace_kwargs, in_process_debug_adapter=False):
                 creationflags=creationflags,
                 env=python_env,
             )
-            if os.name == "posix":
+            if _CAN_DAEMONIZE:
                 # It's going to fork again to daemonize, so we need to wait on it to
-                # clean it up properly.
+                # clean it up properly. If we did not fork, we cannot take this path
+                # because it cannot perform that extra fork; waiting there would just
+                # preserve the broken assumption that a daemonized grandchild exists.
                 _adapter_process.wait()
             else:
                 # Suppress misleading warning about child process still being alive when