Split the last open substrate-placement question:
- Unix: ships with the local feature v1 (dial_unix — same halves
shape as TCP; the wire enum already carried unix per ADR-001;
the params task's schema list includes all three values)
- Stdio: OUT of scope — a spawned process's stdin/stdout/stderr IS
alktty's pipe mode (LocalTtyBackend + tokio::process + Stdio::piped,
alktty tty-local.md): three multiplexed logical streams + the
exit-code control chunk (alktty ADR-004) + signal forwarding
(REQ-TTY-02). A stdio bridge here would be alktty's runner mode
with the terminal stripped out — a strictly worse duplicate that
also drops the semantics that matter (a byte tunnel has neither
exit codes nor signals). Remote command execution composes via
alktty on the same channels substrate.
Updated: open-questions.md OQ-TN-14 (resolved), overview.md feature
gate + deps + OQ summary, producer.md OQ ref, OQ-TN-10 promotion
(#3 split), phase-0-findings + both POC summaries' resolution notes,
params task (schema enum includes unix), local-socket-halves task
(unix ships, stdio does NOT — with the composition rationale),
oq-tn-14-tracker task repurposed (boundary-maintenance: re-opens only
if a consumer needs stdio-without-process-semantics — which would
need its own ADR, or if the alktty/alktunnels boundary needs
sharpening).
Verified: taskgraph valid (12 tasks, no cycles)
POC at /workspace/alktunnels-reverse-poc (14 tests, clippy/fmt clean,
repeat-run stable) over alkcall 0.6.0:
- The review 007 non-finding trace confirmed by execution: the hub
(accept side) opens tunnel channels toward a connect-side worker
serving its own open op (from_connection_with_serving +
ChannelOperations::register_on + post-hoc openable registration)
- ADR-047 §5 exercised in the Pub-like orientation: the worker
(connect side) allocates odd IDs; the hub adopts
- R-01 plan flow under concurrency: two same-resource opens, distinct
channels, distinct dialed handles — the forward POC's handoff race
is structurally gone
- OQ-TN-03's last open thread closed: no advertisement op needed —
the listener is the initiator's own local resource; a far-side
listener is a producer-side listen establisher over the same open op
- W4 EOF sentinel propagation validated (half-close semantics);
W3 adopter self-reaping pinned as a TunnelSession spec requirement;
W2 post-hoc registration viable
Findings:
- F-1: ChannelPlan's Send+Sync bound constrains plan payloads
(socket halves carry + Sync; spec should pin the constraint)
- F-2: empty UDP datagrams collide with the EOF sentinel in raw
pass-through (pinned by an executable test) — the length-framed
codec is mandatory for UDP; raw pass-through stays
stream-substrate-only. Second validation of the codec decision;
OQ-TN-02 mandate strengthened
W1 (connect-side serving path resolves caller identity only via
payload auth_token) filed upstream as alkcall consumer-findings
ledger CF-005 (alkcall 0d287a9).
Verification: cargo test 14/14, clippy --all-targets -D warnings,
fmt --check — all clean, repeat-run stable
17 tests pass (7 codec + 10 integration). The producer/consumer
shape, ADR-049 establishment integration, codec decision, and typed
establishment errors all validated over alkcall 0.5.0 channels.
Key findings folded into the ledger:
- OQ-TN-05 resolved for stream substrates: no backend trait —
pump_halves generic over boxed halves (TCP into_split, UDP
UdpHalf adapter); remaining thread is only the hub re-produce
composition question
- OQ-TN-06 convergence test satisfied: producer pump and consumer
pump are the same shape modulo channel side; extraction decidable
in Phase 1
- New finding for the alkcall ledger: OpenHandler JoinHandle
semantics are load-bearing and undocumented — a handler that
returns before the data plane starts tears the channel down at
birth (the POC found this by hanging; the pump must be awaited
inline). Plus: Establishment should carry the channel plan
(the reserved extension point) to kill the establisher handoff
side-channel
- UdpHalf truncation semantics flagged for the Phase 1 ADR
(recommend fail-loud over silent truncation)
POC crate: /workspace/alktunnels-udp-poc (db224cc).
glm-5.3-flash