Compose WireGuard bindspace lifecycles

Add `open_wg_bindspace()` to enter one declared bindspace and an
ordered WireGuard interface stack as one async lifetime.

Deats,
- snapshot caller layer ordering before the first checkpoint
- enter interfaces outermost-first through `AsyncExitStack`
- unwind interfaces before releasing the namespace capability
- yield the live `BindspaceHandle` for endpoint allocation
- test mutable input and cancellation ordering with lifecycle fakes

Prompt-IO: ai/prompt-io/opencode/20260826T022434Z_2245f094_prompt_io.md

(this patch was generated in some part by `opencode` using `gpt-5.6-sol` (`openai`))

ai/prompt-io/opencode/20260826T022434Z_2245f094_prompt_io.md

@@ -0,0 +1,47 @@
+---
+model: gpt-5.6-sol
+service: opencode
+session: tractor-addr-unpacking
+timestamp: 2026-08-26T02:24:34Z
+git_ref: 2245f094
+scope: code
+substantive: true
+raw_file: 20260826T022434Z_2245f094_prompt_io.raw.md
+---
+
+## Prompt
+
+After committing the owned WireGuard interface lifecycle, the human
+asked to continue with the next established incremental step.
+
+## Response summary
+
+Added a WG-specific composition context which owns one declared
+bindspace and an ordered interface stack. It snapshots caller-owned
+layer order before checkpointing, enters interfaces outermost-first,
+and guarantees inside-out interface teardown before bindspace release.
+Its inbound type shows the `(WGTunnelSpec, WGInterfaceConfig)` pairing
+directly, and its docstring depicts the stack and unwind order.
+
+## Files changed
+
+- `tractor/discovery/_tunnel.py` - bindspace/interface stack driver.
+- `tractor/discovery/__init__.py` - public layer and driver exports.
+- `tests/discovery/test_wg_iface_lifecycle.py` - mutable-input,
+  cancellation and nested teardown-order coverage.
+- `ai/tpt-backends/03_wg_tunnel_bindspace.md` - implemented composition
+  and ownership-order contract.
+
+## Human edits
+
+The human accepted and committed the preceding reviewed lifecycle
+boundary, then explicitly requested the next step. That selected the
+previously established bindspace/WireGuard composition boundary. In
+staged review, the human requested an explicit interface-stack analogy
+and a small ASCII diagram explaining entry and exit order. The human
+then identified `WGInterfaceLayer` as an unnecessary single-use alias
+which obscured the inbound tuple shape. The agent applied both
+human-directed edits. The human accepted the fake lifecycle test as a
+focused control-flow check which avoids pyroute2 overhead, while noting
+their general preference for end-to-end coverage. No direct manual
+source edits were observed.

ai/prompt-io/opencode/20260826T022434Z_2245f094_prompt_io.raw.md

@@ -0,0 +1,28 @@
+---
+model: gpt-5.6-sol
+service: opencode
+timestamp: 2026-08-26T02:24:34Z
+git_ref: 2245f094
+diff_cmd: git diff HEAD~1..HEAD
+---
+
+# Raw output - compose WireGuard bindspace lifecycles
+
+After committing the owned WireGuard interface lifecycle, the human
+requested the next incremental change.
+
+> `git diff HEAD~1..HEAD -- tractor/discovery/_tunnel.py tractor/discovery/__init__.py tests/discovery/test_wg_iface_lifecycle.py ai/tpt-backends/03_wg_tunnel_bindspace.md`
+
+Added `open_wg_bindspace()` to compose one declared bindspace with an
+ordered sequence of WireGuard interface layers. The context enters the
+bindspace first, enters interfaces outermost-first through
+`AsyncExitStack`, yields the live `BindspaceHandle`, and removes
+interfaces inside-out before releasing or removing the namespace.
+
+The caller's layer sequence is snapshotted before the first checkpoint,
+so concurrent mutation cannot alter resource entry or unwind order.
+Fake lifecycle tests clear a mutable input list during bindspace entry,
+cancel from the yielded scope, and prove the original stack unwinds in
+dependency-safe order.
+
+Ruff passed and focused bindspace/WireGuard coverage passed 39 tests.

ai/tpt-backends/03_wg_tunnel_bindspace.md

@@ -530,8 +530,8 @@ exit. Creation/removal run in shielded Trio worker calls. A listen
 bearer supplies the local listen port; a dial bearer supplies an
 omitted endpoint only for the selected maddr peer.
 
-and a driver that folds a list of specs into nested contexts
+The composition driver folds a list of specs into nested contexts with
-(`contextlib.AsyncExitStack` for the N-deep case). The
+`contextlib.AsyncExitStack` for the N-deep case. The
 `parse_endpoints()` API (`_multiaddr.py:153`) is the front door:
 it already returns
 `dict[name, list[Address|TunnelledAddress]]` and the
@@ -539,6 +539,14 @@ it already returns
 `dict[str, list[Address]]|dict[...]` return for tunnelled
 entries. Extend it to carry the tunnel stack, not to *enter* it.
 
+`open_wg_bindspace()` is the initial driver for one bindspace and an
+ordered sequence of `(WGTunnelSpec, WGInterfaceConfig)` layers. It
+opens the bindspace first, enters WG interfaces outermost-first through
+`AsyncExitStack`, and yields the live `BindspaceHandle` for endpoint
+allocation. Exit is inside-out, so every interface is removed while the
+namespace FD remains pinned; only then can an owned namespace be
+removed. Endpoint/channel lifetimes belong inside the yielded scope.
+
 The caller supplies `role` to tunnel-resource contexts such as
 `open_wg_iface()`; do not infer it from maddr shape. Bindspace
 lifecycle remains the independent explicit policy above. The same

tests/discovery/test_wg_iface_lifecycle.py

@@ -4,6 +4,8 @@ WireGuard interface policy and owned lifecycle contracts.
 '''
 from __future__ import annotations
 
+from collections.abc import AsyncIterator
+from contextlib import asynccontextmanager as acm
 import os
 from pathlib import Path
 from typing import BinaryIO
@@ -18,6 +20,7 @@ from tractor.discovery import (
     WGInterfaceConfig,
     WGPeerConfig,
     WGTunnelSpec,
+    open_wg_bindspace,
     open_wg_iface,
 )
 from tractor.discovery import _tunnel
@@ -237,3 +240,139 @@ def test_open_wg_iface_shields_cancelled_cleanup(
         trio.run(main)
 
     assert events == ['create', 'yield', 'remove']
+
+
+def test_open_wg_bindspace_nests_resource_lifetimes(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    '''
+    Nested WG interfaces must exit before their bindspace capability.
+
+    Fake two interface layers over one bindspace. Clear the caller's
+    mutable layer list at bindspace entry, then cancel from inside the
+    yielded application scope and checkpoint. The trace proves the
+    stack snapshots its declaration before entry, layers enter
+    outermost-first, cancellation exits them inside-out, and the live
+    bindspace remains available through every interface exit.
+
+    '''
+    events: list[str] = []
+    calls: list[
+        tuple[
+            WGTunnelSpec,
+            WGInterfaceConfig,
+            BindspaceHandle,
+            _tunnel.WGRole,
+        ]
+    ] = []
+    bindspace_spec: BindspaceSpec = BindspaceSpec(
+        kind='netns',
+    )
+    bindspace: BindspaceHandle = BindspaceHandle(
+        spec=bindspace_spec,
+        identity=BindspaceIdentity(
+            kind='netns',
+            key=None,
+            inode=1,
+        ),
+        namespace_fd=None,
+        ownership='borrowed',
+    )
+    outer_spec: WGTunnelSpec = WGTunnelSpec(
+        peer_pubkey=_PEER_KEY,
+        iface='wg-outer',
+    )
+    inner_spec: WGTunnelSpec = WGTunnelSpec(
+        peer_pubkey=_LOCAL_KEY,
+        iface='wg-inner',
+    )
+    outer_config: WGInterfaceConfig = WGInterfaceConfig(
+        private_key=_LOCAL_KEY,
+    )
+    inner_config: WGInterfaceConfig = WGInterfaceConfig(
+        private_key=_PEER_KEY,
+    )
+    layers: list[
+        tuple[WGTunnelSpec, WGInterfaceConfig]
+    ] = [
+        (outer_spec, outer_config),
+        (inner_spec, inner_config),
+    ]
+
+    @acm
+    async def fake_open_bindspace(
+        spec: BindspaceSpec,
+    ) -> AsyncIterator[BindspaceHandle]:
+        '''
+        Yield the stand-in bindspace and record its full lifetime.
+
+        '''
+        assert spec is bindspace_spec
+        events.append('bindspace-enter')
+        layers.clear()
+        try:
+            yield bindspace
+        finally:
+            events.append('bindspace-exit')
+
+    @acm
+    async def fake_open_wg_iface(
+        spec: WGTunnelSpec,
+        config: WGInterfaceConfig,
+        handle: BindspaceHandle,
+        role: _tunnel.WGRole,
+    ) -> AsyncIterator[WGTunnelSpec]:
+        '''
+        Record one interface's arguments and nested lifetime.
+
+        '''
+        calls.append((spec, config, handle, role))
+        events.append(f'{spec.iface}-enter')
+        try:
+            yield spec
+        finally:
+            assert handle is bindspace
+            events.append(f'{spec.iface}-exit')
+
+    monkeypatch.setattr(
+        _tunnel,
+        'open_bindspace',
+        fake_open_bindspace,
+    )
+    monkeypatch.setattr(
+        _tunnel,
+        'open_wg_iface',
+        fake_open_wg_iface,
+    )
+
+    async def main() -> None:
+        '''
+        Cancel while both interface layers are live.
+
+        '''
+        with trio.CancelScope() as scope:
+            async with open_wg_bindspace(
+                bindspace_spec,
+                layers,
+                'dial',
+            ) as handle:
+                assert handle is bindspace
+                events.append('yield')
+                scope.cancel()
+                await trio.sleep_forever()
+
+    trio.run(main)
+
+    assert calls == [
+        (outer_spec, outer_config, bindspace, 'dial'),
+        (inner_spec, inner_config, bindspace, 'dial'),
+    ]
+    assert events == [
+        'bindspace-enter',
+        'wg-outer-enter',
+        'wg-inner-enter',
+        'yield',
+        'wg-inner-exit',
+        'wg-outer-exit',
+        'bindspace-exit',
+    ]

tractor/discovery/__init__.py

@@ -50,6 +50,7 @@ from ._tunnel import (
     WGRole as WGRole,
     mb_pubkey as mb_pubkey,
     mk_wg_maddr as mk_wg_maddr,
+    open_wg_bindspace as open_wg_bindspace,
     open_wg_iface as open_wg_iface,
     parse_wg_maddr as parse_wg_maddr,
     read_wg_peers as read_wg_peers,

tractor/discovery/_tunnel.py

@@ -67,9 +67,16 @@ Unwrap at the parse or bindspace boundary; see `.overlay` and
 
 '''
 from __future__ import annotations
-from collections.abc import AsyncIterator
+
+from collections.abc import (
+    AsyncIterator,
+    Sequence,
+)
 import base64
-from contextlib import asynccontextmanager as acm
+from contextlib import (
+    AsyncExitStack,
+    asynccontextmanager as acm,
+)
 import ipaddress
 import sys
 from typing import (
@@ -85,6 +92,11 @@ import multibase
 import trio
 
 from ..msg._local import ProcessLocal
+from ._bindspace import (
+    BindspaceHandle,
+    BindspaceSpec,
+    open_bindspace,
+)
 
 if TYPE_CHECKING:
     from multiaddr import Multiaddr
@@ -93,10 +105,8 @@ if TYPE_CHECKING:
         Address,
         UnwrappedAddress,
     )
-    from ._bindspace import BindspaceHandle
 else:
     Address = Any
-    BindspaceHandle = Any
     Multiaddr = Any
     UnwrappedAddress = Any
 
@@ -622,6 +632,59 @@ async def open_wg_iface(
                 )
 
 
+@acm
+async def open_wg_bindspace(
+    bindspace_spec: BindspaceSpec,
+    layers: Sequence[tuple[WGTunnelSpec, WGInterfaceConfig]],
+    role: WGRole,
+) -> AsyncIterator[BindspaceHandle]:
+    '''
+    Open one bindspace and its ordered WireGuard interface stack.
+
+    `layers` is an interface stack declared outermost first:
+
+        application scope
+               |
+        layers[-1]         <- last entered, first exited
+               |
+              ...
+               |
+        layers[0]          <- first entered, last exited
+               |
+        bindspace
+
+    `AsyncExitStack` builds it bottom-up in declaration order and
+    unwinds it top-down before the bindspace closes.
+
+    '''
+    layer_stack: tuple[
+        tuple[WGTunnelSpec, WGInterfaceConfig],
+        ...,
+    ] = tuple(layers)
+    async with AsyncExitStack() as stack:
+        bindspace: BindspaceHandle = await (
+            stack.enter_async_context(
+                open_bindspace(bindspace_spec)
+            )
+        )
+
+        layer: tuple[WGTunnelSpec, WGInterfaceConfig]
+        for layer in layer_stack:
+            tunnel_spec: WGTunnelSpec
+            config: WGInterfaceConfig
+            tunnel_spec, config = layer
+            await stack.enter_async_context(
+                open_wg_iface(
+                    tunnel_spec,
+                    config,
+                    bindspace,
+                    role,
+                )
+            )
+
+        yield bindspace
+
+
 def _sync_read_wg_keys(
     iface: str,
     netns: str|None,