---
model: claude-opus-5
service: claude
timestamp: 2026-08-13T00:11:02Z
git_ref: 27c34aebb615c30d4039fa399f4ce2766ed7ba2c
diff_cmd: git diff 3ad7e7e5dc28aa336499725a03744fc10c6c0026..27c34aebb615c30d4039fa399f4ce2766ed7ba2c
---

# Raw output — next-gen tpt-backend implementation plans

## Generated planning docs

> `git diff 3ad7e7e5dc28aa336499725a03744fc10c6c0026..27c34aebb615c30d4039fa399f4ce2766ed7ba2c -- ai/tpt-backends/`

Five markdown docs. `00_shared_backend_contract.md` is normative
and the other three are written against it so they can be worked
independently:

- **`00_shared_backend_contract.md`** — the backend duck-type
  (`<Proto>Address(msgspec.Struct, frozen=True)` + module-level
  `start_listener()`/`close_listener()` + a
  `Msgpack<Proto>Stream(MsgpackTransport)`), the
  `inspect.getmodule(self.addr)` reflection in
  `Endpoint.start_listener()` that forces the Address class and
  its listener fns to share a module, a 10-item registration
  checklist, the dep policy, the test-harness shape, and §1.1's
  proto-key conclusion (below).
- **`01_tipc_backend.md`** — service addressing via
  `TIPC_ADDR_NAMESEQ` (bind/publish) and `TIPC_ADDR_NAME`
  (connect/lookup), `TIPC_TOP_SRV` topology subscriptions as a
  push-based registry, the `get_random()` instance-collision
  hazard, and a step-0 capability-probe spike.
- **`02_quic_iroh_backend.md`** — `iroh` over
  `aioquic`/`quiche`/`trio-asyncio`, a `_uniffi_trio.py` bridge
  built on `TrioToken.run_sync_soon()`, `trio.abc.Listener`/
  `HalfCloseableStream` adapters, and an API-truth table to fill
  in during step 0.
- **`03_wg_tunnel_bindspace.md`** — `wg` as a *bindspace* rather
  than a `MsgTransport`, a `TunnelledAddress` wrapper delegating
  `.proto_key`/`.unwrap()` to `.inner`, `pyroute2` for layer B,
  and `@acm`-managed netns/iface for layer C.
- **`README.md`** — index.

## Generated example code

> `git diff 3ad7e7e5dc28aa336499725a03744fc10c6c0026..27c34aebb615c30d4039fa399f4ce2766ed7ba2c -- examples/multihost/wg_lan/`

- `wg_maddr.py` — `WGTunnelledAddr(msgspec.Struct, frozen=True)`
  carrying `bearer: tuple[str, int]`, `peer_pubkey: str`,
  `inner: tuple[str, int]`, `inner_proto: Literal['tcp']`, plus a
  `.maddr` property that re-renders the canonical form. Pure
  helpers `mb_pubkey()`, `wg8_pubkey()`, `parse_wg_maddr()`, and
  `_segments()` (with a marked stopgap for when the `wg` codec
  isn't installed). `verify_wg_peer()` is impure **by design** and
  kept out of the parse path.
- `host_a_srv.py` / `host_b_client.py` — the two-host runs; both
  pass only `addr.inner` to `open_nursery()`/`open_root_actor()`.
- `README.md` — grammar, owner table, `#108`-branch install line,
  tunnel setup, "what changed vs #482".

## Verified findings (non-code, verbatim)

### `trio` is address-family agnostic

Read against the installed `trio`. `SocketStream`/`SocketListener`
ctor checks are only "is a trio sock object" + `type ==
SOCK_STREAM`, plus an `OSError`-**suppressed** `SO_ACCEPTCONN`
probe. No `AF_*` check anywhere; `TCP_NODELAY`/`TCP_NOTSENT_LOWAT`
are set under `suppress(OSError)`. A TIPC `SOCK_STREAM` sock should
therefore drop straight into `trio.serve_listeners()` with the
existing `MsgpackTransport` framing, making TIPC mostly
table-registration boilerplate w/ zero new deps.

### the `wg` maddr grammar — `/wg/` is infix, not suffix

Installed `baudco/py-multiaddr@wg_support` (PR
multiformats/py-multiaddr#108) into a throwaway venv and
round-tripped every candidate form:

| maddr | `[p.name for p in m.protocols()]` |
| --- | --- |
| `/ip4/1.2.3.4/udp/51820/wg/u<k>` | `['ip4','udp','wg']` |
| `/ip4/../udp/../wg/u<k>/ip4/../tcp/..` | `['ip4','udp','wg','ip4','tcp']` |
| `/ip4/10.0.11.1/tcp/1616/wg/u<k>` | `['ip4','tcp','wg']` |

```
/ip4/192.168.1.50/udp/51820/wg/u<A_pub>/ip4/10.0.11.1/tcp/1616
\_______ bearer __________/\__ key __/\______ overlay ______/
```

Segments *before* `/wg/` are the bearer — the underlay
`(ip, udp-port)` that `wg(8)` itself listens on (`ListenPort`).
Segments *after* are the overlay endpoint, the only part tractor
binds. The third row above is #482's original suffix form: it
parses, but is semantically inverted.

Three parts, three owners — and only one is an `Endpoint`:

| part | bound by | in the runtime? |
| --- | --- | --- |
| bearer | kernel, via `wg-quick`/`pyroute2` | no |
| `/wg/u<key>` | nothing — an identity | no, verified out-of-band |
| overlay | `tractor`'s `IPCServer` | yes, as `.inner` |

### proto-key-tagged `UnwrappedAddress`

Shape-matching in `wrap_address()` does not survive four backends.
TIPC's natural unwrapped form is a `(str, int)`, indistinguishable
from `TCPAddress`; iroh's is a `(str, str)`, already swallowed by
the existing UDS case (`case (_, filename) if type(filename) is
str`). Ordering hacks and prefix-tagging only paper over it.

Recommended prerequisite for all three backends: carry an explicit
proto-key spelled with the `multiaddr` protocol name —
`('tcp', host, port)`, `('unix', path)`,
`('tipc', stype, inst, scope)` — so `wrap_address()` collapses to
`_address_types[addr[0]]` and the collision class stops existing.
This also makes the on-wire form agree with
`mk_maddr()`/`parse_maddr()` instead of being an independent
invention. It is a wire-format change (`SpawnSpec`,
`_root_mailbox`, `_registry_addrs`) plus every fixture and
downstream config, so it wants its own migration commit landed
before any new backend — and it is the moment to stop handing raw
tuples to users at all, making `Address` the public currency and
`UnwrappedAddress` an internal serialization detail (the
discipline `ipaddress` uses).

### netns is a runtime-level config API

`setns(2)` affects the calling thread only and does not move
already-created sockets. So a netns is a spawn/boot-time input
alongside `enable_transports`/`tpt_bind_addrs`, and there is
deliberately no `await actor.enter_netns(...)` — a mid-life API
would silently leave the IPC server bound in the old namespace.
Corollary for layer B: pass `netns=` down to `pyroute2` rather
than assuming a `trio.to_thread` worker inherits it.

### `examples/` collection would have failed CI

`tests/test_docs_examples.py` walks `examples/` recursively and
subproc-runs every collected file asserting `rc == 0`. Its filter
never checks the extension, so all four `wg_lan` files were
collected — including `README.md`, which would have been run as
`python README.md`. `'multihost' not in p[0]` was already in the
exclusion list with no directory using it. Moving the set under
`examples/multihost/wg_lan/` drops collection 24 → 20 with zero
test changes; confirmed via `pytest --collect-only`.

## Corrections applied during the session

The human corrected two claims that had been asserted without
verification, both since retracted in-place in the docs and in the
posted issue comments:

1. that `wg` has "nothing to bind at the tunnel layer, exactly one
   bind" — wrong; a wg stack is genuinely composed, and the real
   axis is *who owns* each layer's endpoint.
2. that `/ip4/../udp/443/quic-v1` was "also composed" — wrong;
   that is one endpoint with a protocol qualifier, not a tunnel.

A self-review before publication also downgraded two
overconfident claims to explicitly-flagged assumptions: the
`uniffi`-uses-asyncio-only-as-executor thesis (contradicted that
plan's own "do not guess from memory" step 0) and TIPC's
duplicate-binder round-robin behaviour (unverified).
