diff --git a/tractor/_addr.py b/tractor/_addr.py
index f59ad542..f6bb5e2a 100644
--- a/tractor/_addr.py
+++ b/tractor/_addr.py
@@ -14,20 +14,31 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 from __future__ import annotations
+from pathlib import Path
 import os
-import tempfile
+# import tempfile
 from uuid import uuid4
 from typing import (
     Protocol,
     ClassVar,
     TypeVar,
     Union,
-    Type
+    Type,
+    TYPE_CHECKING,
 )
 
+from bidict import bidict
 import trio
 from trio import socket
 
+from ._state import (
+    get_rt_dir,
+    current_actor,
+)
+
+if TYPE_CHECKING:
+    from ._runtime import Actor
+
 
 NamespaceType = TypeVar('NamespaceType')
 AddressType = TypeVar('AddressType')
@@ -58,12 +69,24 @@ class Address(Protocol[
         ...
 
     def unwrap(self) -> AddressType:
+        '''
+        Deliver the underying minimum field set in
+        a primitive python data type-structure.
+        '''
         ...
 
     @classmethod
     def get_random(cls, namespace: NamespaceType | None = None) -> Address:
         ...
 
+    # TODO, this should be something like a `.get_def_registar_addr()`
+    # or similar since,
+    # - it should be a **host singleton** (not root/tree singleton)
+    # - we **only need this value** when one isn't provided to the
+    #   runtime at boot and we want to implicitly provide a host-wide
+    #   registrar.
+    # - each rooted-actor-tree should likely have its own
+    #   micro-registry (likely the root being it), also see
     @classmethod
     def get_root(cls) -> Address:
         ...
@@ -74,8 +97,13 @@ class Address(Protocol[
     def __eq__(self, other) -> bool:
         ...
 
-    async def open_stream(self, **kwargs) -> StreamType:
-        ...
+    # async def open_stream(self, **kwargs) -> StreamType:
+    #     '''
+    #     Open a connection *TO* this address and deliver back a
+    #     `trio.SocketStream` wrapping the underlying transport.
+
+    #     '''
+    #     ...
 
     async def open_listener(self, **kwargs) -> ListenerType:
         ...
@@ -104,9 +132,12 @@ class TCPAddress(Address[
             or
             not isinstance(port, int)
         ):
-            raise TypeError(f'Expected host {host} to be str and port {port} to be int')
-        self._host = host
-        self._port = port
+            raise TypeError(
+                f'Expected host {host!r} to be str and port {port!r} to be int'
+            )
+
+        self._host: str = host
+        self._port: int = port
 
     @property
     def is_valid(self) -> bool:
@@ -117,14 +148,23 @@ class TCPAddress(Address[
         return self._host
 
     @classmethod
-    def from_addr(cls, addr: tuple[str, int]) -> TCPAddress:
+    def from_addr(
+        cls,
+        addr: tuple[str, int]
+    ) -> TCPAddress:
         return TCPAddress(addr[0], addr[1])
 
     def unwrap(self) -> tuple[str, int]:
-        return self._host, self._port
+        return (
+            self._host,
+            self._port,
+        )
 
     @classmethod
-    def get_random(cls, namespace: str = '127.0.0.1') -> TCPAddress:
+    def get_random(
+        cls,
+        namespace: str = '127.0.0.1',
+    ) -> TCPAddress:
         return TCPAddress(namespace, 0)
 
     @classmethod
@@ -132,7 +172,9 @@ class TCPAddress(Address[
         return TCPAddress('127.0.0.1', 1616)
 
     def __repr__(self) -> str:
-        return f'{type(self)} @ {self.unwrap()}'
+        return (
+            f'{type(self).__name__}[{self.unwrap()}]'
+        )
 
     def __eq__(self, other) -> bool:
         if not isinstance(other, TCPAddress):
@@ -146,14 +188,14 @@ class TCPAddress(Address[
             self._port == other._port
         )
 
-    async def open_stream(self, **kwargs) -> trio.SocketStream:
-        stream = await trio.open_tcp_stream(
-            self._host,
-            self._port,
-            **kwargs
-        )
-        self._host, self._port = stream.socket.getsockname()[:2]
-        return stream
+    # async def open_stream(self, **kwargs) -> trio.SocketStream:
+    #     stream = await trio.open_tcp_stream(
+    #         self._host,
+    #         self._port,
+    #         **kwargs
+    #     )
+    #     self._host, self._port = stream.socket.getsockname()[:2]
+    #     return stream
 
     async def open_listener(self, **kwargs) -> trio.SocketListener:
         listeners = await trio.open_tcp_listeners(
@@ -177,14 +219,23 @@ class UDSAddress(Address[
     trio.SocketListener
 ]):
 
+    # TODO, maybe we should use 'unix' instead?
+    # -[ ] need to check what other mult-transport frameworks do
+    #     like zmq, nng, uri-spec et al!
     name_key: str = 'uds'
-    address_type: type = str
+    address_type: type = tuple[str, int]
 
     def __init__(
         self,
-        filepath: str
+        filepath: str|Path,
+        maybe_pid: int,
+        # ^XXX, in the sense you can also pass
+        # a "non-real-world-process-id" such as is handy to represent
+        # our host-local default "port-like" key for the very first
+        # root actor to create a registry address.
     ):
-        self._filepath = filepath
+        self._filepath: Path = Path(filepath).absolute()
+        self._pid: int = maybe_pid
 
     @property
     def is_valid(self) -> bool:
@@ -195,22 +246,65 @@ class UDSAddress(Address[
         return
 
     @classmethod
-    def from_addr(cls, filepath: str) -> UDSAddress:
-        return UDSAddress(filepath)
+    def from_addr(
+        cls,
+        addr: tuple[Path, int]
+    ) -> UDSAddress:
+        return UDSAddress(
+            filepath=addr[0],
+            maybe_pid=addr[1],
+        )
 
-    def unwrap(self) -> str:
-        return self._filepath
+    def unwrap(self) -> tuple[Path, int]:
+        return (
+            str(self._filepath),
+            # XXX NOTE, since this gets passed DIRECTLY to
+            # `trio.open_unix_
+            self._pid,
+        )
 
     @classmethod
-    def get_random(cls, namespace: None = None) -> UDSAddress:
-        return UDSAddress(f'{tempfile.gettempdir()}/{uuid4()}.sock')
+    def get_random(
+        cls,
+        namespace: None = None,  # unused
+    ) -> UDSAddress:
+
+        rt_dir: Path = get_rt_dir()
+        pid: int = os.getpid()
+        actor: Actor|None = current_actor(
+            err_on_no_runtime=False,
+        )
+        if actor:
+            sockname: str = '::'.join(actor.uid) + f'@{pid}'
+        else:
+            sockname: str = f'@{pid}'
+
+        sockpath: Path = Path(f'{rt_dir}/{sockname}.sock')
+        return UDSAddress(
+            # filename=f'{tempfile.gettempdir()}/{uuid4()}.sock'
+            filepath=sockpath,
+            maybe_pid=pid,
+        )
 
     @classmethod
     def get_root(cls) -> Address:
-        return UDSAddress('tractor.sock')
+        def_uds_filepath: Path = (
+            get_rt_dir()
+            /
+            'registry@1616.sock'
+        )
+        return UDSAddress(
+            filepath=def_uds_filepath,
+            maybe_pid=1616
+        )
 
     def __repr__(self) -> str:
-        return f'{type(self)} @ {self._filepath}'
+        return (
+            f'{type(self).__name__}'
+            f'['
+            f'({self._filepath}, {self._pid})'
+            f']'
+        )
 
     def __eq__(self, other) -> bool:
         if not isinstance(other, UDSAddress):
@@ -220,15 +314,23 @@ class UDSAddress(Address[
 
         return self._filepath == other._filepath
 
-    async def open_stream(self, **kwargs) -> trio.SocketStream:
-        stream = await trio.open_unix_socket(
-            self._filepath,
-            **kwargs
-        )
-        return stream
+    # TODO? remove right, it's never used?
+    #
+    # async def open_stream(
+    #     self,
+    #     **kwargs,
+    # ) -> trio.SocketStream:
+    #     stream: trio.SocketStream = await trio.open_unix_socket(
+    #         self._filepath,
+    #         **kwargs
+    #     )
+    #     return stream
 
     async def open_listener(self, **kwargs) -> trio.SocketListener:
-        self._sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+        self._sock = socket.socket(
+            socket.AF_UNIX,
+            socket.SOCK_STREAM
+        )
         await self._sock.bind(self._filepath)
         self._sock.listen(1)
         return trio.SocketListener(self._sock)
@@ -238,72 +340,120 @@ class UDSAddress(Address[
         os.unlink(self._filepath)
 
 
-preferred_transport = 'uds'
+preferred_transport: str = 'uds'
 
 
-_address_types = (
-    TCPAddress,
-    UDSAddress
-)
-
-
-_default_addrs: dict[str, Type[Address]] = {
-    cls.name_key: cls
-    for cls in _address_types
+_address_types: bidict[str, Type[Address]] = {
+    'tcp': TCPAddress,
+    'uds': UDSAddress
 }
 
 
-AddressTypes = Union[
-    tuple([
-        cls.address_type
-        for cls in _address_types
-    ])
+# TODO, can't we just use a type alias
+# for this? namely just some `tuple[str, int, str, str]`?
+#
+# -[ ] would also just be simpler to keep this as SockAddr[tuple]
+#     or something, implying it's just a simple pair of values which can
+#     presumably be mapped to all transports?
+# -[ ] `pydoc socket.socket.getsockname()` delivers a 4-tuple for
+#     ipv6 `(hostaddr, port, flowinfo, scope_id)`.. so how should we
+#     handle that?
+# -[ ] as a further alternative to this wrap()/unwrap() approach we
+#     could just implement `enc/dec_hook()`s for the `Address`-types
+#     and just deal with our internal objs directly and always and
+#     leave it to the codec layer to figure out marshalling?
+#    |_ would mean only one spot to do the `.unwrap()` (which we may
+#       end up needing to call from the hook()s anyway?)
+# -[x] rename to `UnwrappedAddress[Descriptor]` ??
+#    seems like the right name as per,
+#    https://www.geeksforgeeks.org/introduction-to-address-descriptor/
+#
+UnwrappedAddress = Union[
+    tuple[
+        str,  # (net/cgroup-)namespace/host-domain
+        int,  # (p)id/port
+    ]  # tcp/udp/uds
+
+    # ?TODO? should we also include another 2 fields from
+    # our `Aid` msg such that we include the runtime `Actor.uid`
+    # of `.name` and `.uuid`?
+    # - would ensure uniqueness across entire net?
+    # - allows for easier runtime-level filtering of "actors by
+    #   service name"
 ]
 
 
+# TODO! really these are discovery sys default addrs ONLY useful for
+# when none is provided to a root actor on first boot.
 _default_lo_addrs: dict[
     str,
-    AddressTypes
+    UnwrappedAddress
 ] = {
-    cls.name_key: cls.get_root().unwrap()
-    for cls in _address_types
+    'tcp': TCPAddress(
+        host='127.0.0.1',
+        port=1616,
+    ).unwrap(),
+    'uds': UDSAddress.get_root().unwrap(),
 }
 
 
 def get_address_cls(name: str) -> Type[Address]:
-    return _default_addrs[name]
+    return _address_types[name]
 
 
 def is_wrapped_addr(addr: any) -> bool:
-    return type(addr) in _address_types
+    return type(addr) in _address_types.values()
 
 
-def wrap_address(addr: AddressTypes) -> Address:
+def mk_uuid() -> str:
+    '''
+    Encapsulate creation of a uuid4 as `str` as used
+    for creating `Actor.uid: tuple[str, str]` and/or
+    `.msg.types.Aid`.
+
+    '''
+    return str(uuid4())
+
+
+def wrap_address(
+    addr: UnwrappedAddress
+) -> Address:
 
     if is_wrapped_addr(addr):
         return addr
 
-    cls = None
+    cls: Type|None = None
     match addr:
-        case str():
+        case (
+            str()|Path(),
+            int(),
+        ):
             cls = UDSAddress
 
         case tuple() | list():
             cls = TCPAddress
 
         case None:
-            cls = get_address_cls(preferred_transport)
-            addr = cls.get_root().unwrap()
+            cls: Type[Address] = get_address_cls(preferred_transport)
+            addr: AddressType = cls.get_root().unwrap()
 
         case _:
             raise TypeError(
-                f'Can not wrap addr {addr} of type {type(addr)}'
+                f'Can not wrap address {type(addr)}\n'
+                f'{addr!r}\n'
             )
 
     return cls.from_addr(addr)
 
 
-def default_lo_addrs(transports: list[str]) -> list[AddressTypes]:
+def default_lo_addrs(
+    transports: list[str],
+) -> list[Type[Address]]:
+    '''
+    Return the default, host-singleton, registry address
+    for an input transport key set.
+
+    '''
     return [
         _default_lo_addrs[transport]
         for transport in transports
diff --git a/tractor/_state.py b/tractor/_state.py
index 79c8bdea..4cb7e784 100644
--- a/tractor/_state.py
+++ b/tractor/_state.py
@@ -14,14 +14,16 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-"""
-Per process state
+'''
+Per actor-process runtime state mgmt APIs.
 
-"""
+'''
 from __future__ import annotations
 from contextvars import (
     ContextVar,
 )
+import os
+from pathlib import Path
 from typing import (
     Any,
     TYPE_CHECKING,
@@ -143,3 +145,22 @@ def current_ipc_ctx(
             f'|_{current_task()}\n'
         )
     return ctx
+
+
+# std ODE (mutable) app state location
+_rtdir: Path = Path(os.environ['XDG_RUNTIME_DIR'])
+
+
+def get_rt_dir(
+    subdir: str = 'tractor'
+) -> Path:
+    '''
+    Return the user "runtime dir" where most userspace apps stick
+    their IPC and cache related system util-files; we take hold
+    of a `'XDG_RUNTIME_DIR'/tractor/` subdir by default.
+
+    '''
+    rtdir: Path = _rtdir / subdir
+    if not rtdir.is_dir():
+        rtdir.mkdir()
+    return rtdir