# alknet-crate-extraction — Migration from the welded core to the extracted crates

**Status:** Findings in progress — mapping the existing code to the
target shape, phase by phase, so the migration can be ordered to keep
the tree compilable at each step.
**Date:** 2026-07-18
**Scope:** The three new crates (`alknet-tls`, `alknet-endpoint`,
`alknet-client`) + the prune of `alknet-core` and `alknet-call` + the
core stream unification (`BiStream` as the handler leaf) + the TTY
control-channel fix + the channels spec cleanup + the `alknet-http`
residual fix. The specs are confirmed tight (reviewed + amended); this
doc is the *how* — what code moves where, in what order, with what
intermediate states.

---

## TL;DR

The migration is **additive-then-subtractive**: build all three new
crates first (no breakage), then prune the old code from core and call
(breakage confined to a single phase), then fix the core stream model
(`BiStream` as the handler leaf), then fix the TTY control-channel
bidirectionality, then clean up the channels spec, then fix the http
residual. Ten phases (0-9), each leaving the workspace compilable. The
heaviest single file (`endpoint.rs`, 1606 lines) is not a monolith —
it's three concerns welded together, each going to a different
destination.

---

## What exists now (the source map)

### `crates/alknet-core/src/endpoint.rs` — 1606 lines, three concerns

The file is not 1600 lines of one thing. It's three concerns that the
extraction separates:

| Lines | Concern | Destination | LOC |
|-------|---------|-------------|-----|
| 1-492 | `AlknetEndpoint` struct, `HandlerRegistry`, `dispatch_quinn`/`dispatch_iroh`, accept loops, `build_auth_context`, `has_iroh_identity` | `alknet-endpoint` | ~492 |
| 493-934 | `TlsSetup`, `build_rustls_server_config`, `build_quinn_server_config_from_rustls`, `RawKeyCertResolver`, `Ed25519SigningKey`, `AcceptAnyCertVerifier`, `SelfSignedCert`, `generate_self_signed_cert`, `load_cert_chain`, `load_private_key`, `build_iroh_endpoint` | `alknet-tls` (TLS setup) / assembly layer (iroh builder) | ~442 |
| 935-1606 | 42 test functions | split by subject | ~671 |

The endpoint struct + dispatch + accept loops (the part that goes to
`alknet-endpoint`) is ~492 lines of implementation — not 1600. The TLS
setup code (~442 lines) goes to `alknet-tls`. The tests (~671 lines)
split by what they test. The file *feels* monolithic because the
`#[cfg(feature = "quinn")]` gates weave the three concerns together,
but the extraction unwinds that.

### `crates/alknet-call/src/client/call_client.rs` — 930 lines

| Lines | Concern | Destination | LOC |
|-------|---------|-------------|-----|
| 40-88 | `RemoteIdentity`, `CallCredentials` (struct + builder) | split: `RemoteIdentity` + new `ConnectionCredentials` → `alknet-core` (`credentials.rs`); `CallCredentials` **removed** (its `auth_token` field had no reader — see Phase 5) | ~48 |
| 90-100 | `ClientError` enum | **removed** (only produced by `connect`) | ~10 |
| 102-187 | `CallClient` struct + `new` + `spawn_dispatch` | **stays** (the pure protocol take-over) | ~85 |
| 189-320 | `build_quinn_client_config`, `build_client_auth`, `select_server_verifier`, `load_platform_root_cert_store`, `load_cert_chain`, `load_private_key`, `Ed25519SigningKey`, `RawKeyClientCertResolver`, `NoClientCertResolver`, `FingerprintPinVerifier` | `alknet-tls` | ~130 |
| 321-640 | `CallConnection`, `Dispatcher` wiring, wire-protocol helpers | **stays** (protocol) | ~320 |
| 640-930 | Tests (16 total — see Phase 5 audit) | split: 10 TLS/verifier tests → `alknet-tls` (Phase 1); 4 protocol-level tests stay in `alknet-call` unchanged; 2 `CallCredentials`-field tests → `alknet-core` (testing `ConnectionCredentials`); 0 lib tests call `connect()` | ~290 |

The call crate's prune is ~140 lines of implementation + `CallCredentials`
removal + `from_call`'s `credentials_auth_token` dead-path removal. The
test work: 10 tests move to `alknet-tls` (Phase 1), 2 `CallCredentials`
tests move to `alknet-core` (testing `ConnectionCredentials`), 4
protocol-level tests stay unchanged. The integration test
(`two_node_call.rs`, 2 tests) splits: the dial+takeover composition test
moves to `alknet-client/tests/` (Phase 3, rewritten with a minimal echo
`ProtocolHandler`); the `from_call` test stays in `alknet-call` (Phase 5,
rewritten to use `spawn_dispatch` + loopback `Connection`). What remains
is the pure protocol: `CallClient` + `CallConnection` + `Dispatcher` +
the wire protocol.

### `crates/alknet-http/src/server/adapter.rs` — the residual

The `HttpAdapter::handle` method does `connection.accept_bi()` → wraps
the send/recv pair in a hand-rolled `QuicStream` (lines 271-300, an
`AsyncRead+AsyncWrite` adapter) → feeds it to `serve_io()`. But
`serve_io` already accepts *any* `AsyncRead+AsyncWrite` (line 244). The
`QuicStream` wrapper is a hand-rolled version of what
`Connection::from_bidi`/`from_stream` (ADR-065, already landed) provides
natively.

The residual: `handle` assumes a quinn-style multi-stream connection
(`accept_bi` returns a fresh bidi stream). For a `from_bidi` connection
(TCP+TLS), `accept_bi` yields the single bidi stream once (ADR-070's
yield-once contract). The `QuicStream` wrapper works but is unnecessary
— the streams from `accept_bi` are already `AsyncRead+AsyncWrite`. The
fix is to drop `QuicStream` and use the streams directly (or via
`TokioIo::new`). This is a small change (~30 lines removed) but needs
verification against ADR-070's `accept_bi` semantics for `from_bidi`.

The `QuicStreamDuplex` test helper (lines 456-471) is the test-side
equivalent — it can be replaced with `Connection::from_stream` test
helpers (the `MockConnection`/`ConnectionKind::Mock` variants were
already removed per ADR-065; tests use `from_stream` with
`tokio::io::sink`/`empty`).

---

## The seven phases

### Phase 0: Move `ConnectionCredentials`/`RemoteIdentity` to `alknet-core` (additive, no breakage)

**What:** Add `ConnectionCredentials` + `RemoteIdentity` to a new
`crates/alknet-core/src/credentials.rs` (~40 lines).
`ConnectionCredentials` is the transport-level credential bundle
(ADR-091) — it carries `local_identity` + `remote_identity` (the two
dimensions the dial consumes). `CallCredentials` is **removed** (its
`auth_token` field had no reader — `connect()` read only
`tls_identity` + `remote_identity`; `spawn_dispatch` takes no
credentials; the `from_call` forwarding path's `auth_token` source was
a different, always-`None` field never connected to `CallCredentials`).
`auth_token` is a per-request payload field, not a call-protocol
credential. Update `alknet-core/src/lib.rs` to `pub mod credentials` +
re-export. Update `alknet-call` to import `ConnectionCredentials` +
`RemoteIdentity` from core and re-export them; remove `CallCredentials`
and its builder methods. No other changes.

**Why first:** It's independent of the three new crates, purely
additive (core gains types, nothing breaks), and means `alknet-client`
(Phase 3) never has a temporary dep on `alknet-call`. The dep graph is
clean from the start. `ConnectionCredentials` (not `CallCredentials`)
is what moves — the dial consumes transport-level dimensions, not
call-protocol dimensions (ADR-091).

**Compilable state:** `cargo test` passes across the workspace.
`alknet-call` imports the types from core; its own code + tests
continue to work via the re-export.

**Done when:** `cargo test` passes, `ConnectionCredentials` +
`RemoteIdentity` are defined in `alknet-core`, `alknet-call` imports
them from core, `CallCredentials` is removed from `alknet-call`.

### Phase 1: Create `alknet-tls` (greenfield, additive)

**What:** New crate `crates/alknet-tls/`. Extract the TLS setup code
from `alknet-core/endpoint.rs` (lines 493-934) + the client-side TLS
helpers from `alknet-call/client/call_client.rs` (lines 189-320).

**Types:** `TlsServerConfig`, `TlsClientConfig`, `TlsError`,
`FingerprintPinVerifier`, `RawKeyCertResolver`,
`RawKeyClientCertResolver`, `NoClientCertResolver`, `Ed25519SigningKey`
(consolidated — one copy, used by both server + client),
`AcceptAnyCertVerifier`, `SelfSignedCert`, `generate_self_signed_cert`,
`load_cert_chain`, `load_private_key`, `load_platform_root_cert_store`
(+ the `webpki-roots` fallback — new, not extracted).

**Deps:** `alknet-core` (TlsIdentity, Ed25519SecretKey, fingerprint),
`rustls`, `rustls-pemfile`, `rustls-native-certs`, `webpki-roots`,
`rcgen`, `tokio`, optional `quinn`/`tokio-rustls`/`rustls-acme`.
`rustls-native-certs` and `webpki-roots` are **always-present (not
feature-gated)** — the unknown-X.509-remote CA-verification path in
`TlsClientConfig::new` is transport-agnostic; the `webpki-roots`
fallback merges built-in roots when the platform store is empty so
`NoRootAnchors` is unreachable in practice (ADR-088 §5). Do not gate
them under `quinn`/`tcp`.

**Compilable state:** `alknet-tls` builds and tests standalone. Core and
call are unchanged — the old code still exists (duplicated). No
breakage. The new crate's tests are the moved tests from
`endpoint.rs` (the TLS-setup tests) + the moved tests from
`call_client.rs` (the verifier/client-config tests).

**Tests that move here (from `endpoint.rs`):**
- `raw_key_cert_resolver_only_raw_public_keys`
- `self_signed_cert_generation_produces_cert_and_key`
- `acme_directory_production_url` / `staging_url` / `custom_url`
- `tls_setup_x509_returns_no_acme_state`
- `build_rustls_server_config_raw_key_succeeds`
- `build_rustls_server_config_self_signed_succeeds`
- `build_quinn_server_config_from_rustls_succeeds`
- `load_private_key_returns_error_when_no_key_present` / `_file_missing`
- `load_cert_chain_returns_error_when_file_missing`
- `accept_any_cert_verifier_*` (4 tests)
- `ed25519_signing_key_*` (6 tests)
- `raw_key_cert_resolver_debug_is_implemented`

**Tests that move here (from `call_client.rs`):** the
`FingerprintPinVerifier` + `build_quinn_client_config` tests (need
adaptation — they currently test via `connect`, should test via
`TlsClientConfig::new` directly).

**Done when:** `cargo test -p alknet-tls` passes, the crate is
self-contained, no other crate changed.

### Phase 2: Create `alknet-endpoint` (greenfield, additive)

**What:** New crate `crates/alknet-endpoint/`. Extract the endpoint
struct + dispatch + accept loops from `alknet-core/endpoint.rs` (lines
1-492), built fresh against the ADR-083 shape (`new(handlers, dynamic,
identity_provider, drain_timeout)` + `with_quinn`/`with_iroh`/`with_tcp_tls`
+ public `dispatch` + `run`/`shutdown`). No `EndpointError` (removed per
the spec review). `shutdown()` is infallible.

**Types:** `AlknetEndpoint`, `HandlerRegistry`, `TcpTlsListener`,
private `dispatch_quinn`/`dispatch_iroh`/`dispatch_tcp_tls`,
`build_auth_context`, the `extract_*` helpers.

**Deps:** `alknet-core` (Connection, ProtocolHandler, AuthContext,
IdentityProvider, DynamicConfig), optional `quinn`/`iroh`/`tokio-rustls`,
`tokio`, `arc-swap`, `tracing`.

**Module breakdown (the 492 lines split):**
- `registry.rs` — `HandlerRegistry` (~40 lines + tests)
- `endpoint.rs` — `AlknetEndpoint` struct, `new`, builder methods,
  `run`, `shutdown` (~120 lines)
- `dispatch.rs` — `dispatch` (public), `build_auth_context`, the
  `acme-tls/1` guard (~80 lines)
- `accept/quinn.rs` — `dispatch_quinn`, `run_quinn_accept_loop`,
  `extract_quinn_alpn`, `extract_quinn_client_fingerprint` (~80 lines)
- `accept/iroh.rs` — `dispatch_iroh`, `run_iroh_accept_loop`,
  `extract_iroh_client_fingerprint` (~50 lines)
- `accept/tcp_tls.rs` — `dispatch_tcp_tls`, `run_tcp_tls_accept_loop`,
  `extract_tcp_tls_alpn`, `extract_tcp_tls_client_fingerprint` (new,
  ~60 lines — not in the current code; written fresh per ADR-083)

This is a fresh build, not a move — the old `endpoint.rs` stays in core
until Phase 4. The new crate is written against the target shape, not
the old shape.

**Compilable state:** `alknet-endpoint` builds and tests standalone.
Core's `endpoint.rs` still exists (duplicate). No breakage.

**Tests that move here (from `endpoint.rs`):**
- `handler_registry_*` (5 tests)
- `build_auth_context_*` (3 tests)
- `dispatch_decision_logic_lookup_and_auth`
- `has_iroh_identity_*` (3 tests)
- `endpoint_constructs_with_iroh_raw_key_identity`
- `iroh_endpoint_runs_accept_loop_and_shutdown`
- `debug_for_alknet_endpoint_is_implemented_without_panicking`

**Done when:** `cargo test -p alknet-endpoint` passes, the crate is
self-contained, no other crate changed.

### Phase 3: Create `alknet-client` (greenfield, additive)

**What:** New crate `crates/alknet-client/`. The `AlknetClient` dial
seam — three dial methods (`dial_quic`/`dial_tcp_tls`/`dial_iroh`),
all unified on `&ConnectionCredentials` (ADR-091), consuming
`TlsClientConfig` from `alknet-tls` + `ConnectionCredentials` from
`alknet-core`. The SOCKS5 proxy path (ADR-090) is feature-gated.

**Types:** `AlknetClient`, `ClientDialError`, `Socks5ProxyConfig`,
`Socks5Credentials` (behind `socks5` feature).

**Deps:** `alknet-core` (Connection, ConnectionCredentials,
RemoteIdentity, Ed25519SecretKey), `alknet-tls` (TlsClientConfig),
optional `quinn`/`tokio-rustls`/`iroh`/`fast-socks5`.

**Feature gates:** `quinn = ["dep:quinn", "alknet-tls/quinn",
"alknet-core/quinn"]`, `tcp = ["dep:tokio-rustls", "alknet-tls/tcp"]`,
`iroh = ["dep:iroh", "alknet-core/iroh"]`, `socks5 = ["dep:fast-socks5"]`.

**Compilable state:** `alknet-client` builds and tests standalone. No
breakage — the old `CallClient::connect` still exists in
`alknet-call` (duplicate dial). The new crate's tests use
`AlknetClient::dial_*` + `spawn_dispatch`/`from_connection` or test
the dial in isolation with mock transports.

**Done when:** `cargo test -p alknet-client` passes, the crate is
self-contained, no other crate changed.

### Phase 4: Prune `alknet-core` (subtractive, breakage confined)

**What:** Delete `endpoint.rs` from core. Remove `pub mod endpoint`
from `lib.rs`. Remove the heavy deps (`quinn`, `iroh`, `rcgen`,
`rustls-pemfile`, `rustls-acme`) from `Cargo.toml` — but keep the
`quinn`/`iroh` *features* (they gate `Connection::from_quinn`/
`from_iroh` in `types.rs`). Add `ConnectionCredentials` +
`RemoteIdentity` to core (from `alknet-call` — done in Phase 0;
`CallCredentials` stays in `alknet-call` per ADR-091).

**The `lib.rs` change:**
```rust
// Before:
pub mod endpoint;  // ← removed
pub mod auth;
pub mod config;
// ... rest unchanged

// After:
pub mod auth;
pub mod config;
pub mod credentials;  // ← new (ConnectionCredentials, RemoteIdentity)
// ... rest unchanged
```

**The `Cargo.toml` change:** `quinn`/`iroh`/`rcgen`/`rustls-pemfile`/
`rustls-acme` leave `[dependencies]`. The `quinn`/`iroh` features stay
(gating `types.rs` constructors). The `acme` feature is removed
(vestigial — the ACME state machine is on `TlsServerConfig` in
`alknet-tls` now).

**The `fingerprint.rs` doc comment** (line 13) references
`alknet_core::endpoint` — update to reference `alknet-endpoint` /
`alknet-tls`.

**Breakage:** anything that imported `alknet_core::endpoint` breaks.
But per the source map, *nothing does* — no handler crate or call
imports the endpoint module. The only consumer is the future assembly
layer (hub/worker), which doesn't exist yet. So the prune is clean:
delete the file, update `lib.rs`, update `Cargo.toml`, fix the
`fingerprint.rs` comment. Core's own tests for `endpoint.rs` are gone
(moved to `alknet-tls` in Phase 1 and `alknet-endpoint` in Phase 2).

**Compilable state:** `cargo test -p alknet-core` passes (minus the
endpoint tests, which moved). The `quinn`/`iroh` features still work
(`Connection::from_quinn`/`from_iroh` in `types.rs`).

**Done when:** `cargo test -p alknet-core` passes, the crate is
lightweight (~3200 LOC, no heavy transport deps).

### Phase 5: Prune `alknet-call` (subtractive, breakage confined)

**What:** Delete `connect()` + all TLS helpers + `ClientError` +
`CallCredentials` from `call_client.rs`. The transport dimensions
(`ConnectionCredentials`/`RemoteIdentity`) already moved to core in
Phase 0; here we remove the old definitions from `call_client.rs` and
update imports. `CallCredentials` is **removed** (its `auth_token`
field had no reader — `connect()` read only `tls_identity` +
`remote_identity`; `spawn_dispatch` takes no credentials; the
`from_call` forwarding path's `auth_token` source was
`OpSummary.credentials_auth_token: Option<String>`, always `None`,
never connected to `CallCredentials.auth_token`). `auth_token` is a
per-request payload field, not a call-protocol credential. Update
`Cargo.toml` to drop `quinn`/`rustls`/`rustls-native-certs`/
`rustls-pemfile`. Also remove `from_call`'s `credentials_auth_token`
dead path: the `credentials_auth_token` field on `OpSummary`, the
`credentials_auth_token` parameters on `make_forwarding_handler` /
`make_streaming_forwarding_handler`, and the `auth_token` parameter on
`build_forwarded_payload` are all removed (always `None`, different
type than `CallCredentials.auth_token`, never connected). The two
`from_call` tests asserting the `Some` path
(`build_forwarded_payload_sets_auth_token_when_provided`,
`streaming_forwarding_handler_sets_auth_token_when_provided`) are
removed — they test a code path never exercised in production.

**The `call_client.rs` after prune:**
- `CallClient` struct + `new` + `registry` + `identity_provider` +
  `spawn_dispatch` (~85 lines — unchanged)
- `CallConnection` + `Dispatcher` wiring (stays — protocol)
- `RemoteIdentity` — removed from `call_client.rs` (moved to
  `alknet-core` in Phase 0; re-imported from there)
- `CallCredentials` — **removed** (its `auth_token` field had no
  reader; `connect()` was its only consumer and is removed in this
  phase; `auth_token` is a per-request payload field, not a credential
  — ADR-091, amended 2026-07-17)
- `ClientError` — removed
- `connect` + all `build_*`/`select_*`/`load_*`/`Ed25519SigningKey`/
  `RawKeyClientCertResolver`/`NoClientCertResolver`/
  `FingerprintPinVerifier` — removed (now in `alknet-tls`)

**The `Cargo.toml` after prune:** `quinn`, `rustls`,
`rustls-native-certs`, `rustls-pemfile` all leave. The `quinn` feature
is **removed** (it only gated `connect` + the TLS helpers, both
removed — keeping it as a no-op would mislead a user enabling
`quinn` on `alknet-call` expecting QUIC support; removing it surfaces
any stray `#[cfg(feature = "quinn")]` the prune missed). `alknet-call`
becomes a pure protocol crate.

**Test impact (per the test audit below):** the lib tests in
`call_client.rs` (16 tests) split into 4 that stay unchanged
(protocol-level, use `spawn_dispatch(stub_connection())`), 10 that
move to `alknet-tls` in Phase 1 (TLS/verifier tests), and 2 that move
to `alknet-core` (testing `ConnectionCredentials` — the
`call_credentials_builder_methods` and
`remote_identity_none_is_load_bearing_not_defaulted` tests, which
access `remote_identity`/`tls_identity` fields that moved to
`ConnectionCredentials`). The `from_call.rs` tests: 25 stay unchanged
(protocol-level, use `CallConnection` directly), 2 are removed (the
`credentials_auth_token` `Some`-path tests — see above). The
integration test file (`tests/two_node_call.rs`, 2 tests) splits:
`two_node_call_round_trip` (dial + take-over composition) moves to
`alknet-client/tests/` (Phase 3, rewritten with a minimal echo
`ProtocolHandler` on a test ALPN — no `alknet-call` dependency);
`from_call_discovers_and_forwards_over_quic_loopback` (call-protocol-
specific, uses `from_call`) stays in `alknet-call` (Phase 5, rewritten
to use `spawn_dispatch` + loopback `Connection` — **not**
`AlknetClient::dial_quic`, which would re-create the dep the prune
removes).

The implementation prune: delete `ClientError`, delete `connect`,
delete `CallCredentials` and its builder methods, delete the TLS
helpers (~140 lines), delete `from_call`'s `credentials_auth_token`
dead path (~30 lines). The test work: 10 TLS tests already moved in
Phase 1, 2 `CallCredentials` tests move to `alknet-core`, 4 protocol
tests stay, 2 `from_call` dead-path tests removed, the integration
test splits as above.

**Compilable state:** `cargo test -p alknet-call` passes with the
rewritten tests. The crate has no TLS/transport deps, no
`CallCredentials`, no `from_call` dead path.

**Done when:** `cargo test -p alknet-call` passes, the crate is a pure
protocol crate.

### Phase 6: Core stream unification — `BiStream` as the handler leaf

**Status:** **Done** (commit `b60a584`, 2026-07-18). All "Done when"
criteria met: `BiStream` is the only type returned by `accept_bi` /
`open_bi`; `Connection::from_stream` is removed; `from_bidi` is the
only public stream constructor; `cargo test` passes workspace-wide
(one pre-existing `alknet-http` failure remains — see Phase 9's
"Pre-existing test failure to fix in a follow-up" note; unrelated to
Phase 6, verified by stashing). The `QuicStream` wrapper and
`QuicStreamDuplex` test helper removals that Phase 9 called for were
done as part of this phase's call-site updates (Phase 9 is now marked
done — subsumed).

**What was planned:** Implement ADR-092 (drafted, pushed) and the
stream-unification resolution from
`docs/research/stream-unification/findings.md`. The changes to
`alknet-core`:

- `accept_bi()` returns `BiStream` (a concrete `AsyncRead + AsyncWrite`
  newtype wrapping the inner transport), not a split `(SendStream,
  RecvStream)` pair.
- `Connection::from_stream` is removed. `from_bidi` is the only public
  stream constructor.
- `SendStream`/`RecvStream` collapse to thin newtypes used only
  internally by `BiStream` (they never cross a crate boundary as part
  of a constructor).
- `BiStream` implements `AsyncRead + AsyncWrite` directly — no
  hand-rolled adapter needed at call sites.

**Impact on call sites:** Every handler that currently calls
`accept_bi()` and gets a `(SendStream, RecvStream)` pair gets a
`BiStream` instead. The `QuicStream` wrapper in `alknet-http`
(`server/adapter.rs:271-314`) becomes unnecessary — `BiStream` is
already `AsyncRead + AsyncWrite`. The `QuicStreamDuplex` test helper
(`adapter.rs:456-493`) is similarly replaceable.

**What was done (cross-crate, +408/-399 lines net -57):**
- **alknet-core** (`types.rs`): added concrete `BiStream` struct boxing
  `Box<dyn AsyncReadWrite + Unpin>` with `from_joined` (pub — downstream
  crates that produce split halves naturally, e.g. the future channels
  reassembly path and tests, call this) and `from_bidi` (pub(crate))
  constructors; changed `BidiStreamSource::accept_bi`/`open_bi` return
  types to `BiStream`; the join happens once in the
  `QuinnBidiStreamSource` / `IrohBidiStreamSource` /
  `StreamBidiStreamSource` impls via `tokio::io::join`; collapsed
  `SendStream`/`RecvStream` to thin newtypes over
  `Box<dyn Async* + Send + Unpin>` (removed `SendStreamKind` /
  `RecvStreamKind` enums and the quinn/iroh per-call dispatch — the
  join is in the `BidiStreamSource` impl now); removed
  `Connection::from_stream`; promoted `Connection::from_bidi` to the
  only public stream constructor; updated tests (`from_source_tests`,
  `tests`) to use `from_bidi` + `BiStream`, added a `SinkEmpty` test
  helper for `Connection`-level-only test connections.
- **alknet-http** (`server/adapter.rs`): dropped the 44-line `QuicStream`
  wrapper and the 38-line `QuicStreamDuplex` test helper; tests use a
  single `tokio::io::duplex` whose ends are each `AsyncRead + AsyncWrite`
  natively.
- **alknet-tty** (`adapter.rs`): `TtyAdapter::handle` splits the
  `BiStream` from `accept_bi` via `tokio::io::split` for
  `drive_session`'s separate `AsyncWrite`/`AsyncRead` args (the stdlib
  idiom for `TcpStream`-style duplex streams).
- **alknet-call** (`protocol/*`, `client/*`): `Dispatcher::handle_stream`
  takes `BiStream` and splits internally; `CallConnection::call_with_payload`/
  `subscribe_with_payload`/`write_envelope` split the `open_bi` result
  via `tokio::io::split` at the call site; `write_request` /
  `read_stream_until_closed` are now generic over `AsyncWrite` /
  `AsyncRead` (were: concrete `SendStream`/`RecvStream`); added
  `protocol/test_support.rs` with a shared `sink_empty_connection()`
  helper replacing the 5 duplicated `stub_connection()` fns; updated all
  test `handle_stream` call sites to build
  `BiStream::from_joined(recv, send)` from the existing
  `BufReader<Cursor>` + duplex pair.

**Compilable state:** `cargo test -p alknet-core` passes. Handler
crates (`alknet-tty`, `alknet-call`, `alknet-http`) may need import
updates but no logic changes — they already treat the result of
`accept_bi()` as an `AsyncRead + AsyncWrite` pair.

**Done when:** `cargo test` passes workspace-wide, `BiStream` is the
only type returned by `accept_bi()`, `from_stream` is removed,
`from_bidi` is the only public constructor.

### Phase 7: TTY control-channel bidirectionality fix

**What:** Fix the "control isn't actually bidirectional" flaw in
`alknet-tty`. The current `STREAM_CONTROL = 3` is documented as
"bidirectional" but the adapter ignores `Exit` from the client
(`adapter.rs:462-463`). The fix:

- Split `STREAM_CONTROL = 3` into `STREAM_CTRL_IN = 3` (client→server,
  write half) and `STREAM_CTRL_OUT = 4` (server→client, read half).
- Update `InvalidStreamType` bound from `> 3` to `> 4`.
- Update `ChunkReader`/`ChunkWriter` to handle the new stream types.
- Update the adapter to properly route control messages on both halves.
- Update `control.rs` to reflect the split (resize/signal/eof on
  ctrl_in, exit on ctrl_out).

This is a TTY-layer fix — the channels layer has no `stream_type`
concept and is unaffected.

**Compilable state:** `cargo test -p alknet-tty` passes. The control
channel is properly bidirectional.

**Done when:** `cargo test -p alknet-tty` passes, `STREAM_CONTROL` is
replaced with `STREAM_CTRL_IN`/`STREAM_CTRL_OUT`, the adapter handles
both directions correctly.

### Phase 8: Channels spec cleanup — 8-byte wire format, no `stream_type`

**What:** Update the channels crate specs (`docs/architecture/crates/
channels/`) and ADRs to reflect the stream-unification resolution:

- Wire format is **8 bytes**: `[channel_id:u32 BE][length:u32 BE]`
  followed by an opaque payload. The channels layer owns `channel_id`
  and `length`; the payload is the handler's framing, carried
  transparently.
- The channels layer has no `stream_type` concept — not in its header,
  not in its code, not in its mental model.
- `into_sub_streams()` is removed. `accept_bi` is the only accessor;
  it yields one `BiStream` per channel.
- Every channel is a `BiStream`. Handlers sub-multiplex their
  `BiStream` however they want (TTY's 5-byte format, call's
  length-prefixed JSON, tunnel's raw bytes, SSH's channel protocol).
- The add/strip utility: `add_channel_id(channel_id, payload_bytes) ->
  chunk` on write; `strip_channel_id(chunk) -> (channel_id,
  payload_bytes)` on read.

**ADRs amended:**
- ADR-071: wire format is 8 bytes, not 9; no `stream_type` in the
  channels header.
- ADR-074: `into_sub_streams` removed; `accept_bi` is the only
  accessor.
- ADR-077: reversed — TTY always uses its 5-byte format; the channels
  layer carries it transparently in the payload.

**This is a spec/docs phase** — the channels crate doesn't exist yet
(per ADR-081, it's planned as `alknet-channels-core` +
`alknet-channels-call`). The POC at `/workspace/alknet-channels-poc/`
validated the 9-byte format; the spec update changes it to 8 bytes
before implementation begins.

**Compilable state:** No code changes — spec/docs only. `cargo test`
passes workspace-wide (unchanged).

**Done when:** ADRs 071/074/077 are amended, channels spec docs are
updated, the POC's wire format notes are updated.

### Phase 9: Fix `alknet-http` — drop `QuicStream` wrapper

**Status:** **Done — subsumed by Phase 6** (commit `b60a584`,
2026-07-18). The `QuicStream` wrapper (44 lines) and the
`QuicStreamDuplex` test helper (38 lines) were removed as part of
Phase 6's call-site updates (per ADR-092 migration step 2 — the wrapper
removal is the `alknet-http` call-site update). `grep -r QuicStream
crates/` returns no matches; `HttpAdapter::handle` is 4 lines; the
test helpers use a single `tokio::io::duplex` whose ends are each
`AsyncRead + AsyncWrite` natively.

**What was planned:** Remove the `QuicStream` wrapper from
`server/adapter.rs` (lines 271-314) and the `QuicStreamDuplex` test
helper (lines 456-493). After Phase 6, `accept_bi()` returns `BiStream`
which is already `AsyncRead + AsyncWrite` — the hand-rolled adapter is
unnecessary.

**The change:** `HttpAdapter::handle` calls `connection.accept_bi()`,
gets a `BiStream`, and passes it directly to `serve_io()` (or via
`TokioIo::new` if the `hyper` adapter needs it). The 44-line
`QuicStream` wrapper is deleted. The test helper is replaced with
`BiStream`-based test utilities.

**Why this was a light pruning:** The original Phase 6 was deferred
because `SendStream` is `AsyncWrite`-only and `RecvStream` is
`AsyncRead`-only — the `QuicStream` wrapper was necessary to combine
them. After Phase 6, `BiStream` bundles both halves natively. The
wrapper becomes dead code.

**Pre-existing test failure to fix in a follow-up:** Phase 9's "Done
when" criterion was "`cargo test -p alknet-http` passes." One
`alknet-http` test fails on the `develop` baseline (before, during,
and after Phase 6 — verified by stashing Phase 6 and re-running):
`adapters::to_mcp::tests::search_returns_access_control_filtered_ops_excluding_subscriptions`
panics with `"handler kind mismatch: Subscription requires
HandlerKind::Stream (got HandlerKind::Once)"`. The bug is in the test
helper `full_registry_with_ops` (`to_mcp.rs:501-516`), which always
registers with `HandlerKind::Once(make_echo_handler())` regardless of
`op_type` — when the test passes `OperationType::Subscription` for
`"events/stream"`, the registry's kind validation (tightened in commit
`9c81129 feat(call): introduce StreamingHandler, HandlerKind,
ResponseStream + INVALID_OPERATION_TYPE (ADR-049)`) rejects it. The
fix is in the test helper: branch on `op_type` and use
`HandlerKind::Stream(make_streaming_handler(...))` for `Subscription`
ops (mirror the pattern in `dispatch.rs`'s
`registry_with_subscription`). This is unrelated to Phase 6/9 — it's a
test-helper bug that predates the stream-unification work — but it
blocks Phase 9's "Done when" criterion and should be fixed in a small
follow-up commit before Phase 9 is considered fully closed.

---

## Intermediate states (compilable after each phase)

| After phase | State |
|-------------|-------|
| 0 (credentials) | `ConnectionCredentials`/`RemoteIdentity` in core; call imports from core; `CallCredentials` removed; no breakage |
| 1 (tls) | `alknet-tls` builds standalone; core/call/http unchanged (old code duplicated) |
| 2 (endpoint) | `alknet-endpoint` builds standalone; core still has old `endpoint.rs` (duplicate) |
| 3 (client) | `alknet-client` builds standalone; call still has old `connect` (duplicate) |
| 4 (core prune) | core is lightweight; `endpoint.rs` gone; `ConnectionCredentials` in core |
| 5 (call prune) | call is pure protocol; `connect` + TLS helpers + `CallCredentials` + `from_call` dead path gone; Category B tests already moved; 2 `CallCredentials` tests moved to core |
| 6 (stream unification) | **Done** (`b60a584`). `BiStream` is the handler leaf; `accept_bi` returns `BiStream`; `from_stream` removed; `from_bidi` is the only public constructor; `SendStream`/`RecvStream` are thin internal newtypes. Subsumed Phase 9's `QuicStream`/`QuicStreamDuplex` removal. |
| 7 (TTY control fix) | TTY control channel is properly bidirectional (`STREAM_CTRL_IN = 3`, `STREAM_CTRL_OUT = 4`); `InvalidStreamType` bound updated. **Unchanged by Phase 6** — Phase 7's work is in `wire.rs` and `control.rs`, neither of which Phase 6 touched. |
| 8 (channels spec) | Channels spec updated to 8-byte wire format; no `stream_type` concept; `into_sub_streams` removed; ADRs 071/074/077 amended. **Unchanged by Phase 6** — docs-only, no code. |
| 9 (http fix) | **Done — subsumed by Phase 6** (`b60a584`). `QuicStream` wrapper removed from `alknet-http`; `BiStream` used directly; `QuicStreamDuplex` test helper removed. One pre-existing `alknet-http` test failure remains (test-helper bug in `to_mcp.rs::full_registry_with_ops`, unrelated to Phase 6/9) — see Phase 9's "Pre-existing test failure to fix in a follow-up" note. |

Phases 0-3 are purely additive — no existing code breaks, no tests
break. Phases 4-5 are subtractive — the pruned code's callers don't
exist yet (no assembly layer), so the breakage is confined to the
crate's own tests (and per the test audit, the call prune removes
`CallCredentials` and the `from_call` dead path; the TLS tests moved in
Phase 1, the `CallCredentials` tests moved to core, the protocol tests
use `spawn_dispatch` directly). Phase 6 (stream unification) is a core
refactor that touches all handler crates but is mechanical — handlers
already treat `accept_bi()` results as `AsyncRead + AsyncWrite`. Phase
7 (TTY control fix) is scoped to `alknet-tty`. Phase 8 (channels spec)
is docs-only. Phase 9 (http fix) is a light pruning enabled by Phase 6.

## Ordering rationale

The ordering is **deps before dependents, additive before subtractive**:

- **Phase 0** (`ConnectionCredentials` to core) first because it's
  independent, additive, and makes `alknet-client` (Phase 3) never
  depend on `alknet-call`. ~40 lines moved, zero breakage.
- `alknet-tls` (Phase 1) because both `alknet-endpoint` (indirectly —
  the assembly layer builds `TlsServerConfig`) and `alknet-client`
  (directly — `TlsClientConfig`) depend on it. It has no dep on the
  other new crates.
- `alknet-endpoint` (Phase 2) depends only on `alknet-core` (already
  exists) — it doesn't need `alknet-tls` (the endpoint takes
  pre-built transports). It could go before `alknet-tls`, but putting
  tls first means the assembly layer's transport-building code has a
  home from the start.
- `alknet-client` (Phase 3) depends on `alknet-tls`
  (`TlsClientConfig`) + `alknet-core` (`ConnectionCredentials` — moved
  in Phase 0, so the dep is clean from the start).
- Phases 4-5 (the prunes) go after the new crates because they're
  subtractive. The new crates (0-3) must exist first so the pruned
  code's functionality has a home.
- Phase 6 (stream unification) goes after the prunes because it
  touches all handler crates — the prunes reduce the surface area
  first, making the `BiStream` refactor simpler.
- Phase 7 (TTY control fix) goes after stream unification because
  TTY's `wire.rs` already needs updating for the `BiStream` change
  (the `ChunkReader` reads from an `AsyncRead`; after Phase 6 it
  reads from a `BiStream` which is the same trait). The control
  channel split is a small additional change on top.
- Phase 8 (channels spec) is docs-only and can happen anytime after
  the stream-unification research settles. Placed after Phase 7
  because the TTY fix validates the "handler owns its sub-streams"
  model before the channels spec is finalized.
- Phase 9 (http fix) goes last because it depends on Phase 6
  (`BiStream` makes the `QuicStream` wrapper unnecessary).

## Resolved decisions

### `ConnectionCredentials`/`RemoteIdentity` move — Phase 0 (before Phase 1)

**Decision:** Move `ConnectionCredentials`/`RemoteIdentity` to
`alknet-core` as a standalone additive step *before any new crate is
created* (ADR-091). It's independent of everything else, purely
additive (core gains two small types, nothing breaks), and
`alknet-call` imports them from core so its own code + tests don't
change yet. This means `alknet-client` (Phase 3) never depends on
`alknet-call` — the dep graph is clean from the start, no temporary dep
to clean up later.

`ConnectionCredentials` (not `CallCredentials`) is what moves — it is
the transport-level credential bundle (`local_identity` +
`remote_identity`), carrying only the dimensions the dial consumes.
`CallCredentials` is **removed** (its `auth_token` field had no reader
— `connect()` read only `tls_identity` + `remote_identity`;
`spawn_dispatch` takes no credentials; the `from_call` forwarding
path's `auth_token` source was `OpSummary.credentials_auth_token:
Option<String>`, always `None`, never connected to
`CallCredentials.auth_token`). `auth_token` is a per-request payload
field, not a call-protocol credential. See ADR-091 (amended
2026-07-17) for the full rationale and trace.

The move is ~40 lines (struct definitions + builder impls) into a new
`crates/alknet-core/src/credentials.rs`. `alknet-call`'s
`client/mod.rs` imports `ConnectionCredentials` + `RemoteIdentity`
from core and re-exports them; `CallCredentials` is removed from
`alknet-call`. Test changes: the two `CallCredentials`-field tests
(`call_credentials_builder_methods`,
`remote_identity_none_is_load_bearing_not_defaulted`) move to
`alknet-core` testing `ConnectionCredentials`; `call_client_is_send_sync`
drops the `CallCredentials`/`RemoteIdentity` assertions (or they move
with the types).

### Phase 5 test audit — `call_client.rs` (16 tests)

The 16 tests in `call_client.rs` split into three categories:

**Category A — protocol-level, stay in `alknet-call`, no rewrite
needed (4 tests):**

These tests use `spawn_dispatch(stub_connection())` and don't touch
`connect`, `CallCredentials` fields, or any TLS helper.
`stub_connection()` (line 582) uses
`Connection::from_stream(tokio::io::channel(...))` — already
transport-agnostic. These survive the prune unchanged.

| Test | Line | What it tests |
|------|------|---------------|
| `external_op_dispatches_and_populates_capabilities` | 665 | dispatch + capabilities |
| `unknown_op_returns_not_found` | 679 | dispatch error path |
| `spawn_dispatch_returns_live_call_connection` | 691 | `spawn_dispatch` + ALPN |
| `call_client_is_send_sync` | 705 | trait bounds (import update: `RemoteIdentity` moved to core) |

**Category A2 — `CallCredentials`-field tests, move to `alknet-core`
(2 tests):**

These test `CallCredentials` fields (`remote_identity`, `tls_identity`)
that moved to `ConnectionCredentials` in `alknet-core` (ADR-091). They
move to `alknet-core` testing `ConnectionCredentials::new()` +
`with_remote_identity()`.

| Test | Line | What it tests | Move target |
|------|------|---------------|-------------|
| `call_credentials_builder_methods` | 652 | `CallCredentials` builder (now `ConnectionCredentials`) | `alknet-core` |
| `remote_identity_none_is_load_bearing_not_defaulted` | 921 | `CallCredentials::new()` (now `ConnectionCredentials`) | `alknet-core` |

**Category B — TLS/verifier tests, move to `alknet-tls` (10 tests):**

These test `FingerprintPinVerifier`, `build_client_auth`,
`select_server_verifier`, and `build_quinn_client_config` directly.
They're `#[cfg(feature = "quinn")]`-gated and test the TLS helpers,
not the call protocol. They move to `alknet-tls` in Phase 1 (adapted
to test `TlsClientConfig::new` instead of the free functions). The
two `build_quinn_client_config` tests test the full config build
(verifier + client-auth + provider wired together) and are adapted
to test `TlsClientConfig::new` + `for_quinn()` instead of the free
function.

| Test | Line | What it tests | Move target |
|------|------|---------------|-------------|
| `fingerprint_pin_verifier_matches_correct_ed25519_fingerprint` | 750 | verifier accept | `alknet-tls` |
| `fingerprint_pin_verifier_rejects_wrong_ed25519_fingerprint` | 769 | verifier reject | `alknet-tls` |
| `fingerprint_pin_verifier_matches_correct_sha256_fingerprint` | 789 | verifier X.509 accept | `alknet-tls` |
| `fingerprint_pin_verifier_rejects_wrong_sha256_fingerprint` | 806 | verifier X.509 reject | `alknet-tls` |
| `select_server_verifier_returns_ca_verifier_for_none` | 822 | CA path | `alknet-tls` |
| `select_server_verifier_returns_fingerprint_pin_for_some` | 839 | pin path | `alknet-tls` |
| `build_client_auth_presents_ed25519_raw_key_without_error` | 857 | client cert resolver | `alknet-tls` |
| `build_client_auth_none_resolves_to_no_client_cert` | 879 | no-cert resolver | `alknet-tls` |
| `build_quinn_client_config_with_raw_key_identity_builds_without_error` | 893 | full config build | `alknet-tls` |
| `build_quinn_client_config_with_no_remote_identity_builds_without_error` | 909 | CA-verify config | `alknet-tls` |

**Category C — `connect` integration test, remove (0 tests):**

No test in `call_client.rs` actually calls `connect()`. The tests that
exercise the full QUIC dial path are in `from_call.rs` (which has 27
tests) and in the integration tests. `call_client.rs`'s tests are all
either protocol-level (Category A) or TLS-helper-level (Category B).
This means the `connect` removal doesn't break any test in
`call_client.rs` itself — the tests that need a real connection already
use `spawn_dispatch(stub_connection())`.

**The `from_call.rs` tests (27 tests):** these use `CallConnection`
directly (constructed from `stub_connection()` or a mock), not
`connect`. 25 are protocol-level and stay in `alknet-call` unchanged.
2 are removed: `build_forwarded_payload_sets_auth_token_when_provided`
and `streaming_forwarding_handler_sets_auth_token_when_provided` —
they test the `credentials_auth_token` `Some` path, which is removed
(the field was always `None`, never connected to `CallCredentials`).
The one reference to `connect()` is in a doc comment (line 76:
"the assembly layer calls `from_call` immediately after `connect()`")
— update the comment to say "after `AlknetClient::dial_*` +
`spawn_dispatch`".

**Net Phase 5 test impact:** 4 tests stay unchanged (Category A), 2
tests move to `alknet-core` (Category A2), 10 tests move to
`alknet-tls` in Phase 1 (Category B), 2 `from_call` dead-path tests
removed. The `from_call.rs` tests: 25 stay unchanged, 2 removed. The
prune of `call_client.rs` is mechanical: delete `ClientError`,
`connect`, `CallCredentials` and its builder methods, and all the TLS
helpers (`build_*`, `select_*`, `load_*`, `Ed25519SigningKey`,
`RawKeyClientCertResolver`, `NoClientCertResolver`,
`FingerprintPinVerifier`); keep `CallClient` + `new` +
`spawn_dispatch` unchanged; update imports. Also remove `from_call`'s
`credentials_auth_token` dead path: the field on `OpSummary`, the
parameters on `make_forwarding_handler` /
`make_streaming_forwarding_handler`, and the `auth_token` parameter on
`build_forwarded_payload`. The test suite keeps the Category A tests,
removes the Category A2 tests (moved to core), removes the Category B
tests (moved in Phase 1), removes the 2 `from_call` dead-path tests,
and updates the one doc comment.

This is a larger prune than the initial estimate of "~140 lines of
implementation + ~290 lines of test restructuring." The actual work:
delete `connect` + TLS helpers (~140 lines), delete `CallCredentials`
+ builder methods (~50 lines), delete `from_call`'s
`credentials_auth_token` dead path (~30 lines), move 10 tests to
`alknet-tls` (Phase 1), move 2 tests to `alknet-core`, keep 4 tests
unchanged, remove 2 `from_call` dead-path tests. The `connect` removal
breaks zero lib tests because no lib test calls `connect`.

## Resolved questions

- **Phase 9 `accept_bi` semantics:** **Resolved 2026-07-18.** After
  Phase 6 (stream unification), `accept_bi()` returns `BiStream` which
  is already `AsyncRead + AsyncWrite`. The `QuicStream` wrapper (44
  lines) becomes unnecessary — `BiStream` bundles both halves
  natively. Phase 9 is a light pruning: delete the wrapper, pass
  `BiStream` directly to `serve_io()`. The original deferral
  (2026-07-17) was correct at the time (`SendStream` was
  `AsyncWrite`-only, `RecvStream` was `AsyncRead`-only) but is
  obsoleted by the `BiStream` refactor.
- **Phase 6-8 ordering:** **Resolved 2026-07-18.** Stream unification
  (Phase 6) goes before TTY control fix (Phase 7) because TTY's
  `wire.rs` already needs updating for `BiStream`. Channels spec
  cleanup (Phase 8) is docs-only and goes after the TTY fix validates
  the "handler owns its sub-streams" model. HTTP fix (Phase 9) depends
  on Phase 6.
- **Integration test home:** **Resolved.** The dial + take-over
  composition test moves to `alknet-client/tests/` with a minimal echo
  `ProtocolHandler` on a test ALPN — no `alknet-call` dependency, no
  circular path. The call-protocol-specific tests stay in
  `alknet-call` (rewritten to use `spawn_dispatch` + loopback
  `Connection`). See Phase 5 / open questions above.
- **Workspace `Cargo.toml`:** the three new crates need to be added to
  the workspace member list. Trivial but worth noting.