alkhttp/docs/architecture/decisions/017-call-protocol-client-and-adapter-contract.md

# ADR-017: Call Protocol Client and Adapter Contract

*Ported from alknet ADR-017 (Call Protocol Client and Adapter Contract); re-targeted to alkhttp.*

## Status

Accepted (amended 2026-06-26, 2026-07-13, and 2026-07-16 — see "Amendments" below; the 2026-07-16 amendment per alknet ADR-089 §5 removes `CallClient::connect`)

## Context

The call protocol spec (alknet ADR-012, now alkcall ADR-015) defined the
stream model as bidirectional — "both sides can initiate calls." But the spec
only described the accept side: `CallAdapter` implements `ProtocolHandler`,
accepts incoming connections, and dispatches to the operation registry. The
connect side — who opens the connection, how calls are sent, how remote
operations are discovered and imported — was left as alknet OQ-15.

The need for the connect side is concrete and immediate:

- **Head/worker dispatch**: a head node manages worker nodes (Vast.ai, RunPod,
  local Docker). The head needs to call operations on workers (exec, sync,
  status) and workers need to call back (report status, request work). The
  POC at `/workspace/@alkdev/dispatch` demonstrated this over SSH+axum; under
  the call protocol, it's cross-node composition.
- **NAPI/Python adapters**: Node.js and Python consumers need to call operations
  on an alk node. They speak the EventEnvelope wire format over a connection.
- **Agent tool dispatch**: an agent handler needs to call operations on remote
  nodes (tools, services) the same way it calls local operations — through
  `OperationEnv::invoke()`. The `from_call` adapter makes remote operations
  appear in the local registry.
- **Cross-protocol interop**: external systems (HTTP APIs, MCP servers) are
  imported via `from_openapi` and `from_mcp`. The reverse direction —
  exposing local operations to external systems — needs `to_openapi` and
  `to_mcp`.

The `@alkdev/operations` TypeScript package demonstrated the adapter patterns
(`from_openapi`, `from_mcp`) and the `buildEnv` composition mechanism. The Rust
implementation defines the canonical traits (alknet ADR-013, now alkcall
ADR-033).

alknet OQ-15 was constrained by
[ADR-014](014-secret-material-flow-and-capability-injection.md) (adapters take
credential sources, not static tokens) and
[ADR-015](015-privilege-model-and-authority-context.md) (adapter-registered
operations are `Internal` by default). This ADR locks the remaining one-way
door: the client/adapter contract architecture. The decision record now lives
in the alkcall crate (alkcall ADR-022); this port exists because alkhttp
implements the adapter contract — the `OperationAdapter` trait consumes this
crate's HTTP-backed adapter implementations, and the gateway `/search` and
`/schema` endpoints are the discovery surface `from_call` mirrors.

## Decision

### 1. `CallClient` opens connections and shares the dispatch loop

`CallClient` opens a connection to a remote node with ALPN `alk/call`. Once
connected, the connection is symmetric — both sides can send and receive
`call.requested`. The `CallClient` is not just a caller; it is also a callee.
It has its own operation registry to dispatch incoming calls from the remote
side.

```rust
pub struct CallClient {
    registry: Arc<OperationRegistry>,
    identity_provider: Arc<dyn IdentityProvider>,
}

impl CallClient {
    pub async fn connect(&self, addr: SocketAddr, credentials: CallCredentials) -> Result<CallConnection>;
}
```

The dispatch loop is shared between `CallAdapter` and `CallClient`. Once a
connection is established (whether accepted by the adapter or opened by the
client), the same logic applies: read `EventEnvelope` frames, dispatch to the
operation registry, write responses, and send outgoing `call.requested` events
for calls initiated on this side. The only difference is who opened the
connection.

`CallConnection` provides:
- `call(operation_id, input) -> ResponseEnvelope` — send `call.requested`,
  await `call.responded` (one result)
- `subscribe(operation_id, input) -> Stream<ResponseEnvelope>` — send
  `call.requested`, yield each `call.responded` until `call.completed` or
  `call.aborted`
- `abort(request_id)` — send `call.aborted`, cascade to descendants (alkcall ADR-020)
- `services_list() -> Vec<OperationSpec>` — call `services/list`
- `services_schema(name) -> OperationSpec` — call `services/schema`

### 2. Connection direction is independent of call direction

Who opens the connection (who has the public IP, who uses a relay, who
connects out reverse-runner style) is a connection-layer concern, not a
protocol-layer concern. Once connected, both sides can call each other.

| Topology | Who advertises | Who opens connection | Who can call whom |
|----------|---------------|----------------------|-------------------|
| Public service | Producer (public IP/domain) | Consumer | Both directions |
| P2P (iroh relay) | Both (relay-assisted) | Either | Both directions |
| Reverse (runner pattern) | Head (public IP) | Worker connects out | Both directions |
| Reverse (dispatch pattern) | Worker (public SSH port) | Head connects out | Both directions |

The protocol does not distinguish producer and consumer after connection
establishment. The `CallAdapter` accepts connections; the `CallClient` opens
connections. Both dispatch incoming and outgoing calls through the same
mechanism.

### 3. `from_call` adapter imports remote operations

`from_call` does for call protocol endpoints what `from_openapi` does for HTTP
APIs: discovers operations and registers them in the local registry with
forwarding handlers.

```rust
pub async fn from_call(
    connection: &CallConnection,
    config: FromCallConfig,
) -> Vec<HandlerRegistration>
```

The adapter:
1. Calls `services/list` on the remote node → gets the list of `External`
   operations
2. Calls `services/schema` for each → gets the input/output JSON Schemas and
   declared error_schemas ([ADR-023](023-operation-error-schemas.md))
3. For each discovered operation, constructs a `HandlerRegistration` bundle:
   - The spec mirrors the remote operation's name, namespace, type, schemas
     (input, output, and error_schemas — ADR-023), and access control
   - The handler sends `call.requested` through the `CallConnection` and awaits
     `call.responded` (or streams for `Sub` operations)
   - `provenance: FromCall`, `composition_authority: None`, `scoped_env: None`
     (leaves — [ADR-022](022-handler-registration-provenance-and-composition-authority.md))
4. The caller registers these bundles in their local registry (into the
   connection's overlay — alkcall ADR-024/ADR-019)

`from_call`-registered operations are `Internal` by default
([ADR-015](015-privilege-model-and-authority-context.md)) — they
are composition material, not directly callable from the wire. The handler
that composes them is `External`.

The `FromCallConfig` includes:
- The credential source for the outbound connection
  ([ADR-014](014-secret-material-flow-and-capability-injection.md)) — TLS identity,
  auth token, or capability-provided credentials
- An optional namespace prefix (to avoid collisions when importing from
  multiple remote nodes)
- An optional operation filter (to import only specific operations)

### 4. `to_openapi` and `to_mcp` adapters export local operations

The reverse direction — exposing local operations to external systems:

- **`to_openapi`**: generates an OpenAPI spec from the local registry's
  `External` operations. External systems (HTTP clients, API gateways) can
  discover and call alk operations through a standard HTTP interface. This is
  the gateway pattern — the five fixed gateway endpoints
  (`/search`/`/schema`/`/call`/`/batch`/`/subscribe`), not one path per
  operation (ADR-042) — implemented in alkhttp.
- **`to_mcp`**: exposes local operations as MCP tools. MCP clients (editors,
  AI tools) can discover and call alk operations through the MCP protocol —
  the four fixed gateway tools (ADR-041), implemented in alkhttp.

These adapters are outbound bridges — they translate the call protocol's
operation model into external protocol formats. They do not modify the local
registry; they project it.

### 5. The adapter contract trait

The adapter patterns share a common shape: they produce
`HandlerRegistration` bundles that register in the local registry. The
trait:

```rust
#[async_trait]
pub trait OperationAdapter: Send + Sync {
    async fn import(&self) -> Vec<HandlerRegistration>;
}
```

The return type is `Vec<HandlerRegistration>` (not `(OperationSpec,
Handler)` pairs) — [ADR-022](022-handler-registration-provenance-and-composition-authority.md)
changed the registration API to the bundle
shape, and adapters must produce bundles. Adapter convenience methods
construct bundles with `composition_authority: None` and `scoped_env: None`
for the leaf ops they produce.

The trait is **async** because `from_call` requires async discovery
(`services/list` + `services/schema` over a connection). A synchronous
trait cannot accommodate `from_call` without a separate async pre-step that
populates a cache. The sync adapters (`from_openapi`, `from_mcp` reading a
static spec) trivially satisfy an async trait — their `import()` bodies
contain no `.await` points. The async/sync question is decided: the trait
is async.

Implementations:
- `FromOpenAPI` — imports from an OpenAPI spec (HTTP-backed handlers;
  implemented in alkhttp)
- `FromMCP` — imports from an MCP server (MCP-backed handlers; implemented in
  alkhttp)
- `FromCall` — imports from a remote call protocol endpoint
  (call-protocol-backed handlers; implemented in alkcall)
- ~~`FromJsonSchema` — imports from a JSON Schema definition (schema-only, no
  handler — used for validation or client generation)~~ — **superseded by
  [ADR-066](066-from-jsonschema-as-http-adapter.md)**: `from_jsonschema` is
  now an HTTP-backed single-endpoint adapter in alkhttp (reqwest
  forwarding handler, not a schema-only placeholder); `FromJsonSchema`
  provenance stays in alkcall as a handler-bearing leaf.

The `to_*` adapters are outbound projections, not `OperationAdapter`
implementations — they consume the registry, they don't produce entries for it.

The specific trait signatures (error types, configuration parameters) are
two-way doors for implementation. The one-way doors are the architectural
commitments: adapters produce `HandlerRegistration` bundles
([ADR-022](022-handler-registration-provenance-and-composition-authority.md)), the
trait is async (required by `from_call`), and the adapter *trait* lives in
alkcall while adapter *implementations* live with their transport
(HTTP-backed adapters in alkhttp per ADR-066; connection-backed `from_call`
in alkcall). See alkcall's `client-and-adapters.md` §"Adapter Location Map."

### 6. Cross-node call tree and abort cascade

When a `from_call` handler sends `call.requested` to a remote node, the call
participates in the local call tree via `parent_request_id`. If the parent is
aborted, the cascade (alkcall ADR-020) reaches the `from_call` handler, which sends
`call.aborted` to the remote node. The remote node cascades to its own
descendants. The abort crosses the node boundary transparently.

```
Head node                                    Worker node
  r1: /dispatch/run_training
    r1-a: worker/exec (from_call handler)
      → call.requested { id: r1-a } ────────→ receives, dispatches to exec
                                                r1-a-1: exec spawns child
  user aborts r1
    cascade to r1-a
      from_call handler sends:
        call.aborted { id: r1-a } ───────────→ receives, cascades to r1-a-1
                                                  aborts exec and children
```

### 7. Credential sources for connections

The `CallClient` needs credentials to authenticate to the remote node. These
come from capabilities
([ADR-014](014-secret-material-flow-and-capability-injection.md)), not environment
variables. The credential types:

- **TLS identity**: the local node's Ed25519 key (RFC 7250 raw key) or X.509
  cert, derived from the vault at startup
- **Auth token**: an opaque token for call-protocol-level authentication,
  decrypted from the vault or derived from a shared secret
- **Remote identity verification**: the expected fingerprint or cert of the
  remote node, stored as a capability (not an env var or config file)

The `from_call` adapter receives these credentials at registration time,
same as `from_openapi` receives HTTP credentials.

## Consequences

**Positive:**
- Cross-node composition works the same as local composition. A handler calls
  `env.invoke("worker", "exec", ...)` and doesn't know (or care) whether
  `worker/exec` is a local operation or a `from_call`-imported remote
  operation. The composition is transparent.
- The head/worker pattern (dispatch, runners) is a connection topology, not a
  protocol feature. Workers can connect to heads (runner pattern) or heads can
  connect to workers (dispatch pattern) — the protocol handles both.
- `from_call` is the same pattern as `from_openapi` and `from_mcp`: discover,
  register, forward. The adapter contract is unified.
- `to_openapi` and `to_mcp` enable interop with non-alk systems without
  those systems needing to speak EventEnvelope.
- The abort cascade (alkcall ADR-020) crosses node boundaries transparently. No
  consumer needs to implement cross-node abort propagation.
- The NAPI and Python adapters can use `CallClient` directly to call remote
  operations — they don't need a separate client implementation.

**Negative:**
- `CallClient` has its own operation registry (for dispatching incoming calls
  from the remote side). This is a second registry instance, not the global
  one — it needs to be populated with the operations this node wants to expose
  to that specific remote peer. The specific mechanism (sharing the global
  registry, a peer-scoped subset, or a separate registry) is a two-way door.
- `from_call`-registered operations have a latency cost: each invocation sends
  a `call.requested` and awaits a `call.responded`. This is
  inherent to remote calls and not specific to the adapter pattern. Caching
  or batching strategies are consumer concerns.
- The `to_*` adapters need to translate the call protocol's operation model
  (JSON Schema, EventEnvelope, subscribe/stream) into external formats
  (OpenAPI paths, MCP tools). Some semantics don't map cleanly (e.g.,
  `Sub` streaming in OpenAPI, bidirectional calls in MCP). The adapters handle
  these with best-effort mappings and document the gaps.
- **Published `to_*` specs are compatibility contracts.** The "best-effort"
  mapping label is internal framing. Once a generated spec is published and
  external clients build against it, the mapping semantics (e.g.,
  `Sub` streaming → SSE long-poll) become a de facto contract. Changing the
  mapping later breaks every client. `to_*` mapping choices are two-way
  *before* first publication but one-way *after*. Version the generated
  specs (e.g., OpenAPI spec version tied to the registry's External
  operation set version) and emit a spec version marker so consumers can
  detect mapping changes. This is the "published artifact is a contract"
  blind spot in alknet ADR-009's framework: it classifies doors by reversal cost
  in the codebase, not by compatibility cost for external consumers. (The
  versioning was subsequently specced — alknet ADR-045, ported here as
  [ADR-045](045-to-openapi-gateway-spec-versioning.md).)
- **Sharing the global registry with a `CallClient` exposes local
  capabilities to the remote peer.** Each `HandlerRegistration` carries
  `Capabilities` with secret material. If the `CallClient` shares the
  global registry, a remote peer calling an External operation triggers
  dispatch that populates `OperationContext.capabilities` from the local
  registration bundle — meaning the local node's API keys and signing keys
  are used for the remote peer's call. A peer-scoped subset must filter by
  capability remote-safety (is this operation's capability safe to expose
  to this peer?), not just operation name. The registry-mechanism choice
  (share global vs subset vs separate) is two-way mechanically but has a
  security dimension post-[ADR-022](022-handler-registration-provenance-and-composition-authority.md): the
  "share global" option is a
  capability-exposure decision, not just a dispatch decision.
- The `CallConnection` abstraction adds a layer between the handler and the
  raw transport stream. This is necessary for the `from_call` handler to be
  transparent — it shouldn't know about the underlying transport streams, only
  about call/request semantics.

## Assumptions

1. **The connection is symmetric after establishment.** Both sides can send
   and receive `call.requested`. If a future use case requires one-directional
   connections (e.g., a fire-and-forget notification where the receiver can't
   call back), the model needs extension. The assumption is that bidirectional
   is the correct default.

2. **`services/list` and `services/schema` are the discovery mechanism for
   `from_call`.** The remote node exposes its `External` operations through
   these built-in operations. If a remote node doesn't support service
   discovery (e.g., a minimal worker that only accepts specific calls),
   `from_call` needs an alternative discovery mechanism (static config, manual
   spec). The assumption is that nodes participating in cross-node composition
   support service discovery.

3. **The `from_call` handler is transparent to composition.** A handler that
   calls `env.invoke("worker", "exec", ...)` doesn't know it's a remote call.
   If the remote node is unreachable or the connection drops, the handler gets
   a `call.error` (same as a local handler error). The assumption is that
   remote call failures are handled the same as local handler failures.

4. **`from_call`-registered operations mirror the remote spec.** The imported
   `OperationSpec` has the same name, namespace, type, schemas (input, output,
   and error_schemas per [ADR-023](023-operation-error-schemas.md)), and access
   control as the remote operation. If the remote operation changes (new
   schema, renamed), the imported spec is stale until re-import. The
   assumption is that re-import happens on reconnection or is triggered
   explicitly. Hot-swapping imported specs is a two-way door.

5. **The `to_*` adapters are projections, not live bridges.** `to_openapi`
   generates a spec; it doesn't proxy HTTP requests. An external HTTP client
   calling the generated OpenAPI endpoints needs an HTTP host (alkhttp) that
   translates HTTP requests into call protocol operations — the gateway
   dispatch. The assumption is that `to_*` generates specs/tools, and a
   separate HTTP/MCP handler bridges the actual traffic.

## References

- alknet ADR-005: irpc as call protocol foundation (superseded — see alkcall
  ADR-014, irpc was never integrated; framing is hand-rolled)
- alkcall ADR-015: Call Protocol Stream Model (alknet ADR-012; bidirectional
  streams)
- alkcall ADR-033: Rust as canonical implementation language (alknet ADR-013;
  adapter traits in Rust)
- [ADR-014](014-secret-material-flow-and-capability-injection.md): Secret
  material flow (credential sources, not static tokens)
- [ADR-015](015-privilege-model-and-authority-context.md): Privilege model
  (adapter ops are Internal by default)
- alkcall ADR-020: Abort cascade for nested calls (alknet ADR-016; cross-node
  abort propagation)
- alkcall ADR-023: Peer-Scoped Registry Filtering for CallClient Inbound
  Dispatch (alknet ADR-028; resolves the §1 Consequences security dimension
  flagged as a two-way door)
- alkcall ADR-024: Peer-Graph Routing Model (alknet ADR-029; supersedes
  alkcall ADR-023's `remote_safe`/`trusted_peer` gate)
- alknet OQ-15: Call protocol client and adapter contract (resolved by this
  ADR — the decision record is alkcall ADR-022)
- alknet OQ-25..28: Two-way-door remainders from the call-completion gap
  analysis (DC-1 shape, DC-4 error type, DC-2 re-import trigger, DC-3
  namespace collision — see alknet mono-repo `open-questions.md`; the OQ
  numbers are alknet-record citations)
- The alkcall crate's `call-protocol.md` — the wire protocol spec (alknet
  mono-repo: `crates/call/call-protocol.md`)
- The alkcall crate's `operation-registry.md` — the registry spec (alknet
  mono-repo: `crates/call/operation-registry.md`)
- The alkcall crate's `client-and-adapters.md` — the spec that operationally
  fills the gap this ADR left to implementation (alknet mono-repo:
  `crates/call/client-and-adapters.md`)
- alknet mono-repo `docs/research/alknet-call-completion/gap-analysis.md` —
  DC-1..4, the decisions that needed resolution before implementation
- TypeScript `@alkdev/operations` — `from_openapi`, `from_mcp`, `buildEnv`
  prior art
- POC at `/workspace/@alkdev/dispatch` — head/worker dispatch over SSH+axum

## Amendments (2026-06-26)

This ADR left four decisions as two-way doors (§1 Consequences flagged DC-1's
security dimension; §5 noted trait signatures are two-way doors; Assumption 4
noted re-import hot-swap is a two-way door; §3 mentioned the namespace prefix).
The call-completion gap analysis (alknet mono-repo
`docs/research/alknet-call-completion/gap-analysis.md`
DC-1..4) resolved them. The resolutions:

### DC-1 — CallClient registry scope: resolved by alkcall ADR-023, superseded by alkcall ADR-024

The §1 Consequences security dimension was originally resolved by alknet
ADR-028 (default-deny `remote_safe: bool` + `trusted_peer` opt-in; now
alkcall ADR-023). **alknet ADR-028 is now superseded by alknet ADR-029**
(2026-06-27; now alkcall ADR-024): the flat-namespace single-peer model
alknet ADR-028 built on cannot express the head→N-workers pattern, and the
`remote_safe`/`trusted_peer` gate duplicates the existing
`AccessControl`/`Identity` machinery while reintroducing the blanket-bypass
anti-pattern [ADR-015](015-privilege-model-and-authority-context.md) killed.
alkcall ADR-024 replaces the flat overlay with peer-keyed overlays +
`PeerRef` routing, and retires `remote_safe`/
`trusted_peer` in favor of `AccessControl::check(peer_identity)` — the
existing authorization path that was already in the dispatch path. The peer-
scoping question this section flagged is now answered structurally (peer-keyed
overlays), not by a parallel boolean gate.

### DC-4 — OperationAdapter trait error type: resolved

§5 showed `async fn import(&self) -> Vec<HandlerRegistration>` with no error
type. The trait returns `Result<Vec<HandlerRegistration>, AdapterError>`
where `AdapterError` is a crate-level enum. The *presence* of the error type
is recorded in the alkcall crate's `client-and-adapters.md`;
the exact variants are the two-way-door remainder, tracked as alknet OQ-26.

### DC-2 — from_call re-import on reconnection: manual free function

Assumption 4 noted re-import "happens on reconnection or is triggered
explicitly." The decision is **manual**: `from_call` is a free function; the
assembly layer calls it after establishing the connection. The overlay is
per-connection (Layer 2, alkcall ADR-024/ADR-019), so re-import on reconnect is
naturally scoped; a stale overlay dies with the connection. A
`CallConnection::refresh()` method for mid-connection re-discovery is a
genuine feature addition — non-breaking, additive — if a deployment needs
manual re-discovery without drop-and-reconnect. Two-way door; recorded in
the alkcall crate's `client-and-adapters.md`; tracked as alknet OQ-27. See
alknet ADR-069 (from_call is a manual free function; alkcall ADR-028) for the
full rationale.

### DC-3 — from_call namespace collision: default set

§3's `FromCallConfig` namespace prefix is **optional, default no prefix,
collision = error**. A node importing from two remotes that both expose the
same unprefixed op name should fail loudly. The operator adds prefixes when
importing from multiple sources. Two-way door; recorded in the alkcall
crate's `client-and-adapters.md`; tracked as alknet OQ-28.

### Operational spec

The gap this ADR left to implementation — the `CallClient` API, the
`from_call` flow, the trait signature, the adapter location map, the
no-env-vars invariant, and the exchange-of-operations pattern — is
specified in the alkcall crate's `client-and-adapters.md` (alknet mono-repo:
`crates/call/client-and-adapters.md`). That document
is the operational complement to this ADR; this ADR remains the architectural
authority.

## Amendments (2026-07-09)

### `from_jsonschema` clause superseded by ADR-066

The §5 `FromJsonSchema` implementation listing ("schema-only, no handler")
is **superseded by [ADR-066](066-from-jsonschema-as-http-adapter.md)**.
`from_jsonschema` is now an HTTP-backed single-endpoint adapter in
alkhttp (reqwest forwarding handler, same shape as `from_openapi`),
not a schema-only placeholder in alkcall. The `FromJsonSchema`
provenance variant stays in alkcall (`OperationProvenance`) but is
now a handler-bearing leaf, not a "no handler" entry. The "schema-only,
no handler" concept is removed — schema validation without a handler is
served by consuming `OperationSpec` directly. The §5 "adapters live in
alkcall" one-way-door statement is corrected above to "the adapter
trait lives in alkcall; implementations live with their transport."
See [ADR-066](066-from-jsonschema-as-http-adapter.md) and the alkcall
crate's `client-and-adapters.md` §"from_jsonschema".

## Amendments (2026-07-13)

### `CallClient` transport-agnostic API (mirrors alknet ADR-080's amendment)

The §1 Decision framed `CallClient::connect(addr: SocketAddr,
credentials)` as the primary constructor and described it as "opens a
QUIC connection." The operational spec
(the alkcall crate's `client-and-adapters.md`)
framed `spawn_dispatch(connection)` as the "lower-level API" that
`connect()` uses after the dial. That framing welded the
client-side one-way-door API to QUIC — the same welding alknet ADR-065
unwound on the accept side (alkcall ADR-007) and alknet ADR-080 corrected for
`ChannelClient` (alkcall ADR-043).

The call protocol is transport-agnostic (alkcall ADR-015 EventEnvelope
framing; alknet ADR-065 `Connection::from_stream`/`from_bidi` — alkcall
ADR-007 — accept any `AsyncRead + AsyncWrite`). The connect side is half of
that protocol and must not be coupled to a transport. This amendment reframes
the existing code (which already has the right structure —
`spawn_dispatch` is not feature-gated, `connect` is
`#[cfg(feature = "quinn")]`):

- **`CallClient::spawn_dispatch(connection: Connection)`** — the
  transport-agnostic primary constructor and the one-way-door API.
  Takes a pre-established `Connection` (any transport), spawns the
  shared dispatch loop, returns a live `CallConnection`. Mirrors the
  accept-side `CallAdapter::handle(Connection)` and
  `ChannelClient::from_connection` (alkcall ADR-043).
- **`CallClient::connect(addr, credentials)`** — ~~a QUIC convenience
  constructor~~ **REMOVED per alknet ADR-089 §5 (2026-07-16; alkcall
  ADR-045)**. The dial is centralized in `AlknetClient` (the native client
  dial seam, alkcall ADR-045); `connect` is
  deleted, not retained as a two-way-door convenience, to avoid
  alkcall depending on the client-dial crate and to let alkcall
  shed its TLS/transport deps. Callers compose
  `AlknetClient::dial_quic(...).await?` +
  `CallClient::new(...).spawn_dispatch(conn)`.

The door-type classification is updated: `spawn_dispatch` is one-way
(the handler-facing surface); ~~`connect` is two-way (additive
convenience)~~ `connect` is **removed** (alknet ADR-089 §5). The
`AlknetClient` extraction (alknet OQ-55) is **resolved** by alknet ADR-089 —
the shared dial seam is the client-dial crate; `spawn_dispatch` is the
protocol-crate take-over that consumes the dial's `Connection`.

See the alkcall crate's `client-and-adapters.md`
§"CallClient" for the reframed operational spec.