scaffold: AGENTS.md, Cargo.toml, licenses, agent conventions adapted for alktunnels

- AGENTS.md adapted from alkcall (via alktty's pattern) for the tunnel
  protocol crate: substrate-agnostic conventions, two-pump contract,
  no-forced-binding requirement, alkcall 0.4.0 dependency, wasm-clean
  default crate, ALPN naming
- .opencode/agents/implementation-specialist.md conventions section
  adapted from alkcall's call-protocol rules to tunnel-crate rules
  (mirroring alktty's adaptation)
- docs/sdd_process.md package reference fixed to alktunnels
- Cargo.toml scaffold: wasm-clean tokio subset, alkcall 0.4.0
- LICENSE-MIT / LICENSE-APACHE copied from alktty
- src/lib.rs protocol-only stub; docs/architecture/ lands in Phase 1

Verification: cargo test (0 tests, ok), cargo clippy --all-targets
-- -D warnings, cargo fmt --check, cargo clippy
--target wasm32-unknown-unknown -- -D warnings — all clean
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# AGENTS.md
Operating instructions for opencode agents working in this repo. opencode
auto-loads this file as instructions, overriding the built-in defaults for
this project. Custom agents in `.opencode/agents/` inherit these rules
unless their own prompts say otherwise.
## Git Workflow
**Commit and push when reasonable.** When a change is complete and
verified (build + lint + tests pass), commit and push to `origin/main`
without asking. This overrides the built-in default of "only commit when
explicitly asked."
The workflow:
1. Make the change
2. Verify: `cargo test`, `cargo clippy --all-targets -- -D warnings`,
`cargo fmt --check`, `cargo doc --no-deps` if docs changed
3. Inspect `git status` and `git diff` before staging — stage only the
intended files, never secrets
4. Write a concise commit message matching the repo style (see `git log
--oneline -10`). For multi-point changes, use a summary line plus a
body with bullet points and a verification block.
5. `git push origin main`
6. Report the commit hash and the verification summary
Exceptions — **do not** commit or push without asking:
- The change is exploratory / speculative (you're not sure the user wants
it kept)
- The user is actively reviewing the diff and may ask for changes
- The change touches the wire format or a trait shape that backends or
consumers implement (one-way doors — see "Wire formats are stable" and
"Backend trait shapes are one-way doors" below; once consumers exist,
those signatures are wire-stable contracts)
- You'd be force-pushing, amending a published commit, creating an empty
commit, or skipping hooks
Never commit secrets, keys, or credentials. If a commit fails or hooks
reject it, fix the issue and create a new commit — do not amend the
failed one.
Git identity is preconfigured (`glm-5.3-flash <glm-5.3-flash@alk.dev>`). Do
not change `git config`, skip hooks, or use `git commit -i`.
## Project Conventions (Rust / tunnel protocol crate)
This is the tunnels protocol crate — arbitrary bidirectional tunnels in
the `ssh -L` / `ssh -D` sense (TCP, UDP, unix sockets, and other stream
or datagram substrates), riding alkcall channels the same way alktty
does. It is the sibling of alktty (`alk/tty` — terminal sessions) and
alkcall (call + channels — the substrate both build on). Where alktty
multiplexes one service with a fixed five-stream channel structure, this
crate generalizes the tunnel handler shape: the producer side dials or
accepts on some local substrate and pumps bytes to/from a channels data
channel; the consumer side bridges its own substrate onto that channel.
The conventions below apply to all work in `src/` and `tests/`. They
mirror `.opencode/agents/implementation-specialist.md` §Project
Conventions and are repeated here so they apply to every session, not
just spawned implementation agents.
1. **No comments in code** unless the user explicitly asks. This is a
project-wide convention. Doc comments (`///`, `//!`) are fine and
expected on public API. Inline `//` comments only when the user asks
or when a non-obvious safety/correctness constraint would otherwise be
missed (e.g., "a two-pump tunnel must shut down the opposite sink on
pump completion — `try_join!` alone deadlocks; see alkcall's
channels-adapter spec / alknet ADR-078").
2. **Error handling** — `thiserror` for library error types
(`TunnelError`; `HandlerError`/`StreamError` come from
`alkcall::core`). No panics in library code. No `unwrap()` or
`expect()` outside tests. If you reach for `unwrap`, the error path
wasn't specified — stop and decide what should actually happen. For
poisoned `RwLock`/`Mutex`, use `unwrap_or_else(|e| e.into_inner())`
so a panic in one operation does not cascade to other operations.
3. **`tokio` is the async runtime** — all I/O is async. The tunnel
pumps, the channels integration, and the consumer session type are
all async. Use `tokio::sync` primitives (`oneshot`, `mpsc`) for
lifecycle correlation and per-direction data flow. Any non-wasm
backend module (local TCP/UDP sockets, process-spawned listeners)
lives behind a feature flag like alktty's `local`.
4. **WASM target is load-bearing (by default)** — the default crate
(protocol-only) should compile to `wasm32-unknown-unknown`, following
alktty's precedent. This is what keeps the downstream TS/Python
adapter story viable (a wasm-compiled alktunnels is the protocol
layer for a sandboxed adapter). Use the wasm-clean tokio subset
(`rt`, `sync`, `io-util`, `macros`, `time`) — **do NOT use `features
= ["full"]`** — and keep socket/platform I/O feature-gated. If a
design decision ever forces the default crate off wasm (e.g. the
wire format embeds a substrate-specific type), that is an ADR-worthy
decision, not an accident.
5. **Wire format is stable** — the tunnel wire format is a one-way door
once consumers exist. Follow the alknet ADR-093/alktty ADR-008
precedent: the tunnel payload rides inside channels data channels as
raw bytes (channels strips its 8-byte header transparently; the
tunnel protocol owns whatever framing it puts inside the
`BiStream`). If a negotiation/setup frame is needed (like alktty's
`NegotiateRequest`), make it self-contained per alktty ADR-006 —
length-prefixed JSON, not alkcall's `EventEnvelope` framing. Any
wire-format ADR must be written before the first consumer exists;
after that, changes are additive-only.
6. **Producer/consumer, not server/client** — both sides of a channels
connection can initiate. A producer exposes tunnels (registers
openable channels via `ChannelCore::register_openable`); a consumer
opens tunnel channels (`ChannelClient`). Both sides can be both
simultaneously — connection direction (who opened it) is independent
of tunnel direction (who dials the target, who serves it). Avoid
"server" and "client" framing in docs and API names; use "producer"
and "consumer," or "accept side" / "connect side" for the
connection-establishment half specifically. See alkcall ADR-022,
ADR-037.
7. **Substrate-agnostic by construction** — the protocol layer must not
know whether the bytes come from TCP, UDP, a Unix socket, or a
stdio pipe. The handler sees a `Connection`/`BiStream` from alkcall
core and pumps bytes; the substrate-specific types (`TcpStream`,
`UdpSocket`, etc.) are confined to backend modules behind feature
flags, injected at the assembly layer — the same inversion-point
pattern as alktty's `TtyBackend`. "Arbitrary tunnels" means the
bookkeeping (target addressing, direction, lifecycle) must not
hardcode a substrate. See alknet ADR-078 §Where the pattern lives
and the channels-adapter spec.
8. **Two-pump shutdown-on-completion is a contract** — a tunnel is the
canonical two-pump handler (one pump per direction). Each pump MUST
shut down the opposite sink when it completes; `tokio::try_join!`
alone deadlocks. This was POC-validated in the alknet-channels POC
(Target 3) and pinned as alknet ADR-078. The channels layer drops
all per-channel senders on transport EOF — rely on that for
teardown, and emit EOF sentinels (zero-length chunks) on clean
sink shutdown.
9. **No forced local binding** — a tunnel must not require the producer
(or consumer) to bind a local port. The POC's TCP-tunnel shape
dialed a target from the handler; SSH `-R` style flows need the
reverse (the remote side asks the local side to dial or listen).
The API surface must support both directions and unbound/listen-
optional flows; the binding decision belongs to the caller
(assembly layer), not the protocol crate. This is a spec-level
requirement for the architecture docs, not just an implementation
preference.
10. **Backpressure and limits are inherited, not redefined** — bounded
per-channel buffers, the 256-channel per-connection cap, monotonic
channel IDs, and the zero-length-sentinel EOF convention are
alkcall channels invariants (see alkcall ADR-040/041/034). The
tunnel crate consumes them via `ChannelCore`/`ChannelClient`; do
not build a second demux/mux or re-derive limits. Datagram
substrates (UDP) map onto the chunk stream with the same
backpressure; datagram-boundary preservation, if required, is a
wire-format decision for an ADR, not an accident.
11. **Vendored core types come from alkcall** — `Connection`,
`ProtocolHandler`, `BiStream`, `BidiStreamSource`, `AuthContext`,
`Identity`, `IdentityProvider`, `AccessControl`,
`OwnershipProvider`, `HandlerError`, `StreamError` come from
`alkcall::core`. Do not vendor copies into this crate. alkcall is
v0.4.x — breaking changes are expected at this major-zero stage;
this is an early consumer, so we find and fix issues upstream
rather than working around them. Pin `alkcall = "0.4.0"` (lockfile
resolves 0.4.1) and bump deliberately.
12. **BAST document for the wire format** — when the tunnel wire format
gains binary framing (if any beyond pass-through), it carries a
BAST (Binary Abstract Syntax Tree) document as its machine-readable
spec under `docs/architecture/`, conforming to the BAST meta-schema
at `https://alk.dev/bast/v1/schema`. BAST is plain JSON — no
dependency required to author or consume it. alktunnels does not
depend on alktype; hand-rolled codecs are fine for trivial formats,
with the BAST doc as the contract. Do not roll your own offset map
or validator for complex formats — use alktype (as an optional dep)
when that surfaces.
13. **Access control** — the producer's openable channels get
authorization for free via `ChannelCore::register_openable`, which
wires `AccessControl` into the operation spec (the registry runs
the ACL before the open handler). Scope-gate tunnel opens (e.g.
`TUNNEL_OPEN_SCOPE`, shape following alktty's `TTY_OPEN_SCOPE`) and
optionally consult `OwnershipProvider` for resource ownership
(`provider.owns(id_ref, kind, &id, "tunnel")` — the 4-arg shape;
`OwnershipStore::record` is the 3-arg shape). Tunnels reach local
networks — treat the open gate as the security boundary. See
alkcall ADR-024, ADR-050.
14. **Feature flags** — substrate backends may be feature-gated if the
need arises. The base crate should compile lean (no socket/platform
deps unless the feature is on). Verify both `cargo test` (default)
and `cargo test --all-features` pass if features are added.
15. **Naming** — Rust standard: `snake_case` for functions/variables/
modules, `PascalCase` for types/traits, `SCREAMING_SNAKE_CASE` for
constants.
16. **Module structure** — one module per file under `src/`, re-exported
from `src/lib.rs`. Public API surface is `lib.rs` re-exports. The
expected shape (to be finalized in the architecture docs): a
producer half (adapter / open-handler for `alk/tunnel`-family
ALPNs), a consumer half (a typed session/client that opens tunnel
channels), and shared wire/target-addressing modules. Backend
modules are feature-gated and never imported from the
shared/producer/consumer modules.
17. **ALPN naming** — this crate owns the `alk/tunnel`-family ALPN(s).
One ALPN per protocol per alkcall ADR-004; keep the `alk/` prefix
convention. If multiple tunnel flavors need distinct ALPNs (e.g.
stream vs datagram), decide via ADR before the first consumer —
ALPN strings are wire-stable once published.
## Verification Commands
Run these before committing. All must pass.
```bash
cargo test # full suite
cargo clippy --all-targets -- -D warnings
cargo fmt --check
cargo doc --no-deps # if docs changed
cargo test --all-features # if features are added
cargo check --target wasm32-unknown-unknown # default crate stays wasm-clean
cargo clippy --target wasm32-unknown-unknown -- -D warnings
cargo publish --dry-run --allow-dirty # before a release
```
The wasm check is the structural guard for the "default crate is
wasm-clean" invariant (same as alktty) — run it whenever a
non-backend module changes.
## Architecture Context
- `docs/architecture/` — will hold the authoritative spec (Phase 1 of
the SDD process). It does not exist yet; Phase 0 research lives in
`docs/research/`. Read it before non-trivial changes once it exists.
- The prior art for this crate:
- **alknet-channels POC** —
`/workspace/@alkdev/alknet/docs/research/alknet-channels/poc-summary.md`
(§POC Target 3: tunnel handler). Validates the demux→Connection→
handler→mux path and the two-pump tunnel shape over a stand-in
transport. POC code at `/workspace/alknet-channels-poc/`.
- **alkcall** — `/workspace/@alkdev/alkcall` (v0.4.x, crates.io).
The substrate: call protocol + channels multiplexing. The tunnel
crate consumes `alkcall::core` types and the channels
`ChannelCore`/`ChannelClient`/`register_openable` surface.
- **alktty** — `/workspace/@alkdev/alktty` (v0.1, crates.io). The
sibling pattern to follow: a producer/consumer protocol crate on
alkcall channels, with the backend inversion point, wasm-clean
default crate, and feature-gated local backend.
- Key upstream ADRs that inform this crate's design (alknet numbers;
alkcall's ports live in `/workspace/@alkdev/alkcall/docs/architecture/
decisions/`):
- alknet ADR-093 / alkcall ADR-035 — channels pure channel
multiplexing (8-byte header, no `stream_type`); the tunnel payload
is raw bytes inside the `BiStream`
- alknet ADR-078 — two-pump shutdown-on-completion (the tunnel
handler pattern; a helper extraction was deferred until a second
two-pump consumer exists — this crate is that second consumer)
- alknet ADR-074 / alkcall ADR-038 — `ChannelConnection` as a
`BidiStreamSource`; every handler (TTY, tunnel, call) receives a
`Connection`
- alknet ADR-075 / alkcall ADR-039 — `ChannelsAdapter` /
`ChannelManager` (substrate-agnostic demux; `params` is
ALPN-specific — for tunnels, the target resource)
- alknet ADR-071 / alkcall ADR-034 — channels wire format (one-way
door)
- alkcall ADR-037 — channel lifecycle operations (`channel/open` on
channel 0; `params` carries the tunnel target)
- alkcall ADR-042 — hub relay (byte-for-byte data-channel forwarding
with ID rewrite — tunnels traverse relays transparently)
- alknet ADR-085 — workspace scope: `alknet/tunnel` was flagged
"POC-validated, minimal spec needed, not yet specced"; this crate
is that spec
- What the POC does NOT settle (open work for Phase 0/1):
- UDP and Unix-socket substrates (the POC only exercised TCP) — the
pump pattern is expected to generalize, but datagram boundary
preservation and addressing bookkeeping are unspecced
- The "no forced local binding" requirement (SSH `-R`/dynamic flows)
is not covered by the POC at all
- Target addressing format (what a tunnel `params` looks like) —
alknet ADR-071 §ALPN table noted `alknet/tunnel` as `[0, 1]` data
in/out only, but the addressing scheme was never decided
- If a TODO references a design direction that an ADR has since decided
against, the TODO is stale — remove it and align with the ADR. Do not
implement the rejected design.