# Changelog

All notable changes to this crate are documented here. The format is
based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and
this crate adheres to [Semantic Versioning](https://semver.org/).

## [0.2.0] - 2026-09-06

The alkcall 0.5.0 adoption (ADR-049 — review 006 E-01/N-1): the
channels-path establishment phase. Breaking on the channels path's
error surface; the wire format, the direct-ALPN path, and the
`TtyBackend` trait are unchanged.

### Added

- **Channels establishment phase (ADR-010; alkcall 0.5.0 ADR-049 /
  review 006 E-01).** `register_openable` now registers
  `channels/tty/sub` with an establisher
  (`ChannelCore::register_openable_with_establisher`): the semantic
  validation that used to be post-open in-band error frames — the
  full `NegotiateRequest` parse of schema-valid `input`, `carriage ==
  "raw"`, non-empty `cmd`, backend lookup, and the ADR-050 ownership
  check — runs before the open reply. Rejections resolve the open op
  with `channel:open_failed` carrying `details: { reason, message }`
  (`unknown_resource` for an unknown backend, `handler_error` for
  malformed-negotiation/ownership-denial, `timeout` on the
  establishment deadline) and no channel ever exists opener-side —
  the SSH contract. The phantom-channel workaround
  (allocate → succeed → in-band-fail) is retired.
- **`channel:open_failed` ErrorDefinition on `tty_open_spec()`
  (ADR-016).** The establishment-failure contract (the reachable
  `details.reason` enum) is disclosed via `services/schema`; the spec
  also gains a `description` (review 006 E-02) disclosed via
  `services/list`.
- New tests: the establisher unit gates (parse/carriage/cmd/backend/
  ownership mappings), the end-to-end `channel:open_failed` surfaces
  (the review-006 verification gate), and a pinned test guarding the
  one failure class that stays in-band (below).

### Changed

- **BREAKING — `TtySessionError::ChannelsOpen` carries alkcall's
  typed `ChannelOpenError` (`#[from]`) instead of a flattened
  `String`** (alkcall 0.5.0 ADR-049 §4 / review 006 N-1, applied at
  alktty's layer). Consumers branch on
  `ChannelOpenError::establishment_reason()` instead of parsing a
  debug string.
- **BREAKING — channels-path semantic failures change shape.** An
  unknown backend (and schema-valid-but-unparseable params,
  ownership denial) previously surfaced as
  `TtySessionError::NegotiationRejected` (an in-band `0x00`-prefixed
  error frame on a channel the open op had already reported as
  succeeding); they now fail the open op itself as
  `TtySessionError::ChannelsOpen(CallFailed{ channel:open_failed })`
  (ADR-010). The one failure class that still arrives in-band is
  `allocate_failed` (still `NegotiationRejected`): the establisher
  cannot carry the allocated `TtyHandle` across to the pump handler
  (`Establishment` is payloadless), and re-allocating would violate
  ADR-005's kill-on-`Drop` contract — revisit when alkcall gives
  `Establishment` a payload. The direct-ALPN path's failure surface
  is unchanged (two transports, two contracts).
- `alkcall = "0.5.0"`.

### Fixed

- **No more phantom channels on the channels path.** Ledger, policy
  count, and manager state balance on every establishment rejection
  (the wrapper's teardown runs before the reply), instead of
  allocating a channel that immediately EOFs with an error frame.

## [0.1.0] - 2026-09-05

Initial crates.io release: the `alk/tty` terminal-session protocol —
producer/consumer protocol crate on top of alkcall channels, ported and
consolidated from the `alknet-tty` + `alknet-tty-local` crates of the
alknet mono-repo.

### Added

- **Wire format (ADR-001).** Two-carriage protocol: a 4-byte
  big-endian length-prefixed JSON negotiation frame (`NegotiateRequest`
  — `carriage`/`backend`/`tty`/`cmd`/`cwd`/`env` plus opaque
  `serde(flatten)` backend params), then raw chunks
  (`[stream_type: u8][length: u32 be][payload]`) with five stream types
  (`STREAM_STDIN`=0, `STREAM_STDOUT`=1, `STREAM_STDERR`=2,
  `STREAM_CTRL_IN`=3, `STREAM_CTRL_OUT`=4). Zero-length data chunks are
  sentinels (zero-length stdin = client EOF; zero-length stdout =
  server drained); control chunks are never zero-length. Payloads are
  capped at 16 MiB (`MAX_CHUNK_LEN`) — this keeps the length prefix's
  high byte `0x00`, which is the disambiguation invariant between an
  error frame and a raw chunk (ADR-001 §5). The framing is
  self-contained (ADR-006): not reused from alkcall's `EventEnvelope`
  framing. The control channel is split into `STREAM_CTRL_IN`/`STREAM_CTRL_OUT`
  so it is genuinely bidirectional on the wire (the Phase 7 amendment
  inside ADR-001). TTY always uses its own 5-byte chunk format inside
  channels — the channels layer carries it transparently in the channel
  payload (ADR-008, reversing ADR-007). The machine-readable contract
  is the BAST document (`docs/architecture/tty-bast.md`); a unit test
  guards the BAST's `StreamType` enum against drift from the wire
  constants.
- **`TtyBackend` trait (ADR-002).** The inversion point between the
  wire-format adapter and backend crates. `allocate(&TtyParams) ->
  TtyHandle` (stdin `AsyncWrite`, stdout/stderr `Stream<Item = Bytes>`,
  `exit_code: BoxFuture`, `TtyControlHandle` for resize/signal);
  `resource_id(&TtyParams) -> Option<(kind, id)>` feeds the ADR-050
  ownership check. `TtyError` is `#[non_exhaustive]`. The trait shape
  is a one-way door once backends exist.
- **Local backend behind the `local` feature (ADR-003).** The
  `alknet-tty-local` crate folded in as a feature-gated module:
  PTY mode via `portable_pty` (real terminal semantics — resize,
  process-group signal forwarding, merged stdout/stderr) and pipe mode
  via `tokio::process::Command` (the runner case — separate
  stdout/stderr, no-op resize, pid-only signal), selected by
  `TtyParams::terminal`. The blocking→async bridge uses three dedicated
  std threads feeding tokio mpsc/oneshot channels. Non-wasm by design;
  the default crate (no features) stays `wasm32-unknown-unknown`-clean.
- **`TtyAdapter` producer (direct `alk/tty` ALPN).** A
  `ProtocolHandler` holding a `HashMap<String, Arc<dyn TtyBackend>>`
  keyed by the negotiation frame's `backend` string. Accepts a
  connection, loops `accept_bi`, and dispatches each bidi stream to a
  session. Per-stream flow (ADR-001/002/005): parse + validate the
  negotiation frame (`carriage == "raw"`, non-empty `cmd`), scope-gate
  via `tty:open`, optional `OwnershipProvider` resource check,
  `backend.allocate()`, then three concurrent pumps (stdin→backend,
  stdout/stderr→client, exit→exit chunk) with the **exit-chunk-is-last**
  invariant — `{"type":"exit","code":N}` (`-1` on wait failure, ADR-004;
  negative = signal-terminated) is enqueued only after both stream
  pumps complete and `exit_code` resolves. A concurrent drainer task
  owns the client write half, so a burst of >64 chunks from the backend
  cannot deadlock the session (the drainer starts before the pumps
  join; the single FIFO preserves exit-chunk-last). On session cancel
  the `TtyHandle` drops without driving `exit_code` to completion,
  which triggers the backend's kill-on-`Drop` guard — the adapter has
  no separate kill path (the session-cancel contract, ADR-005: dropping
  the future kills the session target).
- **`channels` integration (ADR-008, ADR-009).** `register_openable` +
  `tty_open_spec` register the `channels/tty/sub` open op on a
  per-connection `OperationRegistry` (per ADR-047's per-connection
  amendment): the registry's `AccessControl` carries the `tty:open`
  scope gate, the op's input schema validates the shared
  `NegotiateRequest` fields (`carriage`/`backend`/`cmd` required;
  alkcall 0.4 enforces at dispatch), and the `OpenHandler` spawns the
  session driver pre-negotiated — **the open op's params ARE the
  negotiation** (ADR-009), no second frame on the channel stream.
  Access control is enforced by the registry before the handler runs;
  the handler validates the backend exists and drives the session.
- **`TtySession` consumer.** The typed client handle with two
  constructors — `connect_direct` (direct `alk/tty` connection:
  writes the negotiation frame, then typed methods) and
  `open_via_channels` (opens `channels/tty/sub` on a `ChannelClient`,
  adopts the channel, starts in raw-chunk mode). Typed methods:
  `send_stdin`/`close_stdin` (stdin chunks / EOF sentinel),
  `recv_stdout`/`recv_stderr` (`Stream<Item = Bytes>`), `resize`,
  `signal`, and `wait` (awaits the `Exit` control chunk; watch-based,
  no lost wakeup). `recv_stdout` ends ON the zero-length drained
  sentinel (it is not yielded as an item). Both constructors
  disambiguate the first response frame (`0x00` prefix = negotiation
  error frame → `NegotiationRejected` with the server's error code;
  raw chunk = session proceeds); a refused session open surfaces as
  `TtySessionError::Open` carrying the upstream error type.
  `TtySessionError` is `#[non_exhaustive]`. Dropping the session
  aborts the read pump and closes the write half.
- **Control messages.** `ControlMessage` (`Resize`/`Signal`/`Eof` on
  `ctrl_in`; `Exit` on `ctrl_out`) — JSON, tagged by `"type"`, unknown
  types ignored by policy. `signal_from_name` maps the common signal
  set (`HUP`/`INT`/`QUIT`/`TERM`/`KILL`/`USR1`/`USR2`/`TSTP`/`CONT`)
  to libc numbers (unix).
- **Crate-root re-exports.** The primary types (`TtyAdapter`,
  `TtySession`, `TtyBackend`, `TtyHandle`, `TtyParams`, `Chunk`,
  `NegotiateRequest`, `ControlMessage`, the wire constants, and
  `LocalTtyBackend` under `local`) are re-exported at the crate root;
  the module paths remain the full surface.
- **Wire write-path validation.** All `ChunkWriter` methods validate
  before touching the transport — a `stream_type` > 4 or a payload over
  `MAX_CHUNK_LEN` fails locally instead of writing a header the peer
  cannot frame (the length is validated before the `u32` cast, so an
  oversized payload cannot truncate past the check and corrupt the
  peer's framing). Empty-payload writes are one shape: `length == 0`
  with no payload bytes.
- **Peek-safe `ChunkReader`.** The reader tracks peeked state:
  `read_chunk()` after `peek_stream_type()` completes the peeked chunk
  instead of consuming a second header byte (which silently
  desynchronized framing), and a second peek returns the peeked byte
  without reading. `read_chunk_after_peek` remains the explicit form.
- **Backpressure regression test.** >64-chunk sessions are driven
  through the real adapter with a per-read timeout so a deadlock
  regression fails the test instead of hanging it, plus exact-boundary
  (`MAX_CHUNK_LEN`) round-trip and server-sends-client-direction-
  stream-types discard tests.
- **PTY bridge robustness (`local` feature).** The stdin sink's EOF
  (`poll_shutdown`) parks an in-flight send on a full channel so the
  waker is registered — a stdin blast followed by EOF always delivers
  the EOF to the child. Lock-poisoning no longer cascades (the five
  lock sites adopt `into_inner()`), and thread-spawn failure maps to
  `TtyError::AllocFailed` instead of panicking.
- **Producer hardening.** The `tty:open` scope gate runs before the
  backend lookup (an unscoped identity gets `forbidden` regardless of
  the request body — no backend-name enumeration differential), and
  the client→backend pump is aborted at session end instead of
  lingering until the client disconnects.

[0.1.0]: https://git.alk.dev/alkdev/alktty/releases/tag/v0.1.0