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docs(arch): call-completion — ADR-028 peer-scoped filtering + client-and-adapters spec + tasks

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Resolves the four gap-analysis decisions (DC-1..4) blocking the alknet-call
client/adapter surface specced in ADR-017:

- ADR-028 (new): locks the one-way door for DC-1 — CallClient registry is
  default-deny (remote_safe: bool on HandlerRegistration, default false across
  all provenance); share-global is an explicit trusted-peer opt-in; filtering
  is a dispatch-time read over the single Layer-0 registry, not a copy.
- client-and-adapters.md (new spec): operationally fills the gap ADR-017 left
  to implementation — CallClient, from_call, from_jsonschema, OperationAdapter
  trait, adapter location map, no-env-vars invariant, exchange-of-operations
  pattern. Keeps call-protocol.md and operation-registry.md under the
  700-line split threshold.
- ADR-017 amended: records DC-2/3/4 v1 defaults (auto-on-reconnect,
  error-on-collision, Result error type) and points DC-1 at ADR-028.
- OQ-25..28 (new): two-way-door remainders (remote_safe shape, AdapterError
  variants, re-import trigger, namespace collision) with v1 defaults recorded.
- Index/cross-ref updates across READMEs and the two existing call specs.

Tasks: 6 task files under tasks/call/ decomposing the completion work along
the gap-analysis priority order — remote-safe-marking (one-way door, first)
→ call-client (phase-risk) → from-call → operation-adapter-trait →
from-jsonschema (parallel with call-client) → review-completion. Graph
validated with taskgraph; parallelism designed in (from-jsonschema runs
concurrent with call-client/from-call once the trait lands).
This commit is contained in:
glm-5.2
2026-06-26 12:25:13 +00:00
parent 6940d9858d
commit 2649e068e5
14 changed files with 1817 additions and 11 deletions
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16
docs/architecture/crates/call/README.md
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@@ -1,7 +1,7 @@
---
status: draft
last_updated: 2026-06-23
review: call/review-call passed 2026-06-23 — registry, protocol, ADR (005/012/014/015/016/017/022/023/024), security, and pattern-consistency checks all conformant; 159 unit/integration tests green; `cargo build`, `cargo clippy -- -D warnings`, `cargo fmt --check`, `cargo test` clean.
last_updated: 2026-06-26
review: call/review-call passed 2026-06-23 — registry, protocol, ADR (005/012/014/015/016/017/022/023/024), security, and pattern-consistency checks all conformant; 159 unit/integration tests green; `cargo build`, `cargo clippy -- -D warnings`, `cargo fmt --check`, `cargo test` clean. Call-completion gap (ADR-017 client/adapter surface) addressed 2026-06-26 — ADR-028 + client-and-adapters.md added; implementation pending.
---
# alknet-call
@@ -14,6 +14,7 @@ Structured RPC over QUIC: operations, request/response, streaming subscriptions,
|----------|--------|-------------|
| [call-protocol.md](call-protocol.md) | draft | CallAdapter, EventEnvelope framing, stream model, PendingRequestMap, bidirectional calls |
| [operation-registry.md](operation-registry.md) | draft | OperationSpec, Handler, OperationRegistry, AccessControl, service discovery, irpc integration |
| [client-and-adapters.md](client-and-adapters.md) | draft | CallClient (outbound connection opener), from_call / from_jsonschema, OperationAdapter trait, adapter location map, no-env-vars invariant, exchange-of-operations pattern |
## Applicable ADRs
@@ -37,6 +38,7 @@ Structured RPC over QUIC: operations, request/response, streaming subscriptions,
| [022](../../decisions/022-handler-registration-provenance-and-composition-authority.md) | Handler Registration, Provenance, and Composition Authority | Registration bundle carries provenance, composition authority, scoped env, capabilities |
| [023](../../decisions/023-operation-error-schemas.md) | Operation Error Schemas | Operations declare domain errors; `call.error` carries typed `details`; adapter fidelity |
| [024](../../decisions/024-operation-registry-layering.md) | Operation Registry Layering | Curated (static) + session/connection overlays (dynamic); `OperationEnv` as trait-object integration point; `OperationContext.env` split into `scoped_env` (data) and `env` (dispatch trait) |
| [028](../../decisions/028-callclient-peer-scoped-registry-filtering.md) | Peer-Scoped Registry Filtering for CallClient Inbound Dispatch | Default-deny peer-scoped registry view; `remote_safe` marking on `HandlerRegistration`; trusted-peer opt-in; locks the ADR-017 §1 security-dimension one-way door |
## Relevant Open Questions
@@ -47,6 +49,10 @@ Structured RPC over QUIC: operations, request/response, streaming subscriptions,
| OQ-14 | Batch operation semantics | resolved | Correlated `call.requested` events is the correct protocol design |
| OQ-16 | Safe vault operations for call protocol exposure | resolved (ADR-014) | None exposed for now |
| OQ-19 | Session-scoped operation registries | resolved | Agent-written operations overlaid on curated registry via `OperationEnv` trait layering. Protocol doesn't need changes; `OperationEnv` must remain a trait. Generalized by ADR-024 to cover connection-scoped overlays. |
| OQ-25 | Remote-safe marking shape for CallClient peer-scoped filtering | open (two-way) | Existence of default-deny filtering locked by ADR-028; shape (`remote_safe: bool` v1 vs per-peer allowlist) is the two-way-door remainder |
| OQ-26 | OperationAdapter error type (AdapterError variants) | open (two-way) | `import()` returns `Result<_, AdapterError>`; variants decided in implementation |
| OQ-27 | from_call re-import trigger | open (two-way) | v1 default: auto-on-reconnect; explicit `refresh()` is additive |
| OQ-28 | from_call namespace collision behavior | open (two-way) | v1 default: error on collision (no prefix by default) |
## Key Design Principles
@@ -59,4 +65,8 @@ Structured RPC over QUIC: operations, request/response, streaming subscriptions,
7. **No secret material on the wire**: The call protocol carries no private keys, API keys, mnemonics, or decrypted credentials. Handlers receive outbound credentials through `OperationContext.capabilities`, injected at the assembly layer. See ADR-014.
8. **Abort cascades to descendants**: `call.aborted` for a parent request cascades to all non-terminal descendants. Default `abort-dependents`; `continue-running` opt-in. See ADR-016.
9. **Internal calls switch authority context, not skip ACL**: The `internal` flag marks composition-originated calls. ACL runs against the handler's composition authority, not the caller's and not as a blanket skip. Operations have External/Internal visibility. Scoped composition env bounds reachability. See ADR-015, ADR-022.
10. **Provenance determines composition capability**: Only `Local` and `Session` ops can compose. Leaves (`FromOpenAPI`, `FromMCP`, `FromCall`) are forwarding stubs — they don't get composition authority or a scoped env. The assembly layer is the sole grantor of composition authority. See ADR-022.
10. **Provenance determines composition capability**: Only `Local` and `Session` ops can compose. Leaves (`FromOpenAPI`, `FromMCP`, `FromCall`) are forwarding stubs — they don't get composition authority or a scoped env. The assembly layer is the sole grantor of composition authority. See ADR-022.
11. **Connection direction is independent of call direction**: Who opens the QUIC connection is a connection-layer concern, not a protocol-layer concern. Both sides can call each other once connected. The `CallAdapter` accepts connections; the `CallClient` opens them; both produce the same `CallConnection` and dispatch through the same loop. See ADR-017, [client-and-adapters.md](client-and-adapters.md).
12. **CallClient registry is default-deny**: A `CallClient` exposes no operations to the remote peer unless explicitly marked remote-safe. Sharing the global registry is an explicit trusted-peer opt-in, never the default. This prevents a remote peer's call from triggering dispatch that populates `OperationContext.capabilities` from the local node's registration bundle. See ADR-028.
13. **Adapter trait lives with the types; implementations live with their transport**: `OperationAdapter` is in `alknet-call`; `from_call`/`from_jsonschema` are in `alknet-call` (QUIC / pure parse); `from_openapi`/`from_mcp`/`to_openapi`/`to_mcp` are in `alknet-http` (reqwest / axum). `alknet-call` stays lean — no HTTP client, no HTTP server. See [client-and-adapters.md](client-and-adapters.md).
14. **No handler reads outbound credentials from any source other than `OperationContext.capabilities`** (no-env-vars invariant): the credential injection path is vault → assembly layer → `Capabilities` → `HandlerRegistration.capabilities` → `OperationContext.capabilities` → handler. Downstream consumers' `std::env::var` reads are unreachable because the assembly layer never calls `Default::default()`. See ADR-014, [client-and-adapters.md](client-and-adapters.md).

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@@ -524,8 +524,9 @@ Handlers clean up resources when their call is cancelled (in Rust, the future is
| Secret material flow | [ADR-014](../../decisions/014-secret-material-flow-and-capability-injection.md) | Call protocol carries no secret material; capabilities injected at assembly layer |
| Privilege model and authority context | [ADR-015](../../decisions/015-privilege-model-and-authority-context.md) | `internal` = authority switch not ACL skip; External/Internal visibility; handler identity + scoped env |
| Abort cascade for nested calls | [ADR-016](../../decisions/016-abort-cascade-for-nested-calls.md) | `call.aborted` cascades to descendants; default `abort-dependents`, `continue-running` opt-in |
| Call protocol client and adapter contract | [ADR-017](../../decisions/017-call-protocol-client-and-adapter-contract.md) | `CallClient` opens connections; `from_call` imports remote ops; connection direction independent of call direction |
| Call protocol client and adapter contract | [ADR-017](../../decisions/017-call-protocol-client-and-adapter-contract.md) | `CallClient` opens connections; `from_call` imports remote ops; connection direction independent of call direction. Client/adapter surface specced in [client-and-adapters.md](client-and-adapters.md) |
| Handler registration, provenance, and composition authority | [ADR-022](../../decisions/022-handler-registration-provenance-and-composition-authority.md) | Registration bundle carries provenance, composition authority, scoped env, capabilities; dispatch path reads from bundle |
| Peer-scoped registry filtering for CallClient | [ADR-028](../../decisions/028-callclient-peer-scoped-registry-filtering.md) | Default-deny `CallClient` registry view; `remote_safe` marking; trusted-peer opt-in |
| Operation error schemas | [ADR-023](../../decisions/023-operation-error-schemas.md) | Operations declare domain errors; `call.error` carries typed `details` |
## Open Questions
@@ -536,6 +537,7 @@ See [open-questions.md](../../open-questions.md) for full details.
- **OQ-14** (resolved): Batch is a client-side pattern of correlated `call.requested` events, not a protocol primitive.
- **OQ-16** (resolved by ADR-014): No vault operations are exposed over the call protocol for now.
- **OQ-19** (resolved): Session-scoped operation registries — agent-written operations overlaid on global registry via `OperationEnv` trait layering. Protocol doesn't need changes; `OperationEnv` must remain a trait.
- **OQ-25..28** (open, two-way): Call-completion remainders — `CallClient` remote-safe marking shape, `OperationAdapter` error type, `from_call` re-import trigger, `from_call` namespace collision. The `CallClient`/adapter surface itself is specced in [client-and-adapters.md](client-and-adapters.md); the one-way door among these (existence of default-deny filtering) is resolved by ADR-028.
## References

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@@ -0,0 +1,537 @@
---
status: draft
last_updated: 2026-06-26
---
# alknet-call — Client and Adapters
The outbound half of the call protocol: opening connections, importing remote
operations, and the adapter contract that ties import-style adapters together.
This document covers what ADR-017 specced but the server-side implementation
(`call-protocol.md`, `operation-registry.md`) did not include — the `CallClient`
that *opens* a connection, the `from_call`/`from_jsonschema` adapters, and the
`OperationAdapter` trait. The server-side `CallAdapter` and `CallConnection`
dispatch loop are covered in `call-protocol.md`; this document covers the
client-side connection-establishment half and the adapter surface.
## What
This document specifies four components, all in `alknet-call`:
1. **`CallClient`** — opens an outbound `alknet/call` QUIC connection and
produces a `CallConnection`. The dispatch loop is shared with the
server-side `CallAdapter` (ADR-017 §1); `CallClient` is the
connection-establishment + credential-handling half, not a parallel
protocol implementation.
2. **`from_call`** — discovers operations on a remote call-protocol endpoint
via `services/list` + `services/schema` (already implemented in
`registry/discovery.rs`) and registers them in the connection's Layer 2
overlay as `FromCall`-provenance leaves with forwarding handlers.
3. **`from_jsonschema`** — schema-only registration: produces
`HandlerRegistration` bundles with no handler, for validation, discovery,
and composition-graph construction without a runtime.
4. **`OperationAdapter` trait** — the async trait that `from_call`,
`from_openapi`, `from_mcp`, and `from_jsonschema` all implement.
It also records two cross-cutting architectural mechanisms that the adapter
surface rests on:
- The **adapter location map** — which adapters live in `alknet-call` vs
`alknet-http`, and why.
- The **no-env-vars invariant** — the architectural mechanism by which
downstream consumers' `std::env::var` credential reads are made unreachable.
And one downstream pattern this completion unblocks:
- The **exchange-of-operations pattern** (runner / container service) — the
canonical bilateral composition this client surface enables.
## Why
The server-side `CallAdapter` (accept path) and `CallConnection` (dispatch
loop) are implemented and tested. The client side is the #1 gap blocking every
downstream consumer: the runner pattern (a process that connects outward to a
hub and exposes local ops), the container-service rewrite, the bilateral
exchange, the NAPI projection, and the agent's cross-node tool dispatch all
require a `CallClient`. `from_call` is the #2 gap; the `OperationAdapter`
trait is the enabling gap for `alknet-http`'s `from_openapi`/`from_mcp`.
ADR-017 specced this surface. This document is the spec that operationally
fills the gap ADR-017 left to implementation: the `CallClient` API, the
`from_call`/`from_jsonschema` flows, the trait signature, the adapter
location, the credential invariant, and the bilateral pattern. The gap
analysis (`docs/research/alknet-call-completion/gap-analysis.md`) identified
four decisions (DC-1..4) needed before implementation; DC-1 is resolved by
ADR-028, and DC-2/3/4 are two-way-door defaults recorded here and tracked as
OQs (DC-2→OQ-27, DC-3→OQ-28, DC-4→OQ-26).
## Architecture
### CallClient
`CallClient` opens a QUIC connection to a remote node on ALPN `alknet/call`,
performs credential setup, and produces a `CallConnection`. The
`CallConnection` type is already implemented (`call-protocol.md` §"CallConnection")
— it wraps an established `Connection` and holds the Layer 2 imported-ops
overlay. `CallClient` is the producer on the outbound side; `CallAdapter`'s
accept path is the producer on the inbound side. Both produce the same
`CallConnection` and hand it to the same shared dispatch loop.
```rust
pub struct CallClient {
/// The operation registry. The peer-scoped view is a dispatch-time read
/// over this registry, not a copy (ADR-028 §5).
registry: Arc<OperationRegistry>,
identity_provider: Arc<dyn IdentityProvider>,
/// Trusted-peer mode (ADR-028 §3): when true, the dispatch path exposes
/// all External ops to the remote peer and `services/list` lists all
/// External ops, ignoring the `remote_safe` marking. When false
/// (default), only registrations with `remote_safe: true` dispatch, and
/// `services/list` hides non-remote-safe ops (ADR-028 Assumption 2).
trusted_peer: bool,
}
impl CallClient {
/// Open a QUIC connection to `addr` on ALPN `alknet/call`, perform
/// credential handshake, and return a CallConnection running the shared
/// dispatch loop. Credentials come from capabilities (ADR-014), not env
/// vars — see "No-Env-Vars Invariant" below.
pub async fn connect(
&self,
addr: SocketAddr,
credentials: CallCredentials,
) -> Result<CallConnection>;
/// Trusted-peer mode: construct a CallClient that exposes all External
/// ops from `registry` to the remote peer, ignoring the remote-safe
/// marking. Explicit opt-in per ADR-028 §3.
pub fn trusted_peer(
registry: Arc<OperationRegistry>,
identity_provider: Arc<dyn IdentityProvider>,
) -> Self;
}
```
The v1 mechanism is the `trusted_peer: bool` flag plus the `remote_safe: bool`
field on each `HandlerRegistration` (default `false` across all provenance,
ADR-028 §4). A richer per-peer filtering mechanism (per-peer allowlist,
capability-class tag) is the two-way-door remainder tracked as OQ-25; v1's
boolean limits exposure control to "remote-safe for any peer" vs "not," which
is acceptable for the runner/dispatch pattern (one remote peer per
`CallClient`).
The connection is symmetric after establishment (ADR-017 §2): both sides can
send and receive `call.requested`. Connection direction (who opened it) is
independent of call direction (who calls whom). The `CallClient` is therefore
both a caller and a callee — it dispatches incoming calls from the remote
peer against its peer-scoped registry view, and it initiates outgoing calls
through the `CallConnection::call()` / `subscribe()` / `abort()` API.
### Credential sources for connections
`CallClient::connect()` takes a `CallCredentials` bundle. Credentials come
from `Capabilities` (ADR-014), never from environment variables. The three
credential dimensions (ADR-017 §7):
```rust
pub struct CallCredentials {
pub tls_identity: Option<TlsIdentity>, // RFC 7250 raw key or X.509
pub auth_token: Option<AuthToken>, // call-protocol-level token
pub remote_identity: Option<RemoteIdentity>, // expected fingerprint/cert
}
```
- **TLS identity** — the local node's Ed25519 raw key (RFC 7250) or X.509 cert,
derived from the vault at startup (ADR-020, ADR-026, ADR-027).
- **Auth token** — an opaque call-protocol-level token, decrypted from the
vault or derived from a shared secret.
- **Remote identity verification** — the expected fingerprint/cert of the
remote node, stored as a capability.
These are populated by the assembly layer at `CallClient` construction time
from vault-derived `Capabilities`. The credential path is the no-env-vars
invariant (below). The concrete shapes of `TlsIdentity`, `AuthToken`, and
`RemoteIdentity` are implementation-detail two-way doors; the one-way
constraints are that they come from `Capabilities`, not env vars (ADR-014).
### from_call
`from_call` discovers the remote peer's `External` operations and registers
them in the connection's Layer 2 overlay as `FromCall`-provenance leaves with
forwarding handlers. The discovery mechanism (`services/list` +
`services/schema`) is already implemented in `registry/discovery.rs`;
`from_call` is the client-side consumer of that API.
```rust
pub struct FromCallConfig {
/// Namespace prefix applied to imported operation names. Optional —
/// default no prefix. Collision on import is an error (DC-3, OQ-28),
/// not last-wins.
pub namespace_prefix: Option<String>,
/// Optional filter — import only operations whose names match. None
/// imports all External ops discovered via services/list.
pub operation_filter: Option<HashSet<String>>,
}
/// Discover the remote peer's External ops and construct HandlerRegistration
/// bundles with FromCall provenance and forwarding handlers. The caller
/// registers the bundles in the connection's overlay via
/// CallConnection::register_imported_all().
pub async fn from_call(
connection: &CallConnection,
config: FromCallConfig,
) -> Result<Vec<HandlerRegistration>, AdapterError>;
```
The flow (ADR-017 §3):
1. Call `services/list` on the remote → list of `External` operations.
2. Call `services/schema` for each → input/output JSON Schemas and declared
`error_schemas` (ADR-023).
3. For each discovered op, construct a `HandlerRegistration`:
- `spec` mirrors the remote op's name (with optional prefix), namespace,
type, schemas, access control.
- `handler` is a forwarding handler: sends `call.requested` through the
`CallConnection`, awaits `call.responded` (or streams for subscriptions).
- `provenance: FromCall`, `composition_authority: None`, `scoped_env: None`
(leaf — ADR-022).
4. The caller registers the bundles via
`CallConnection::register_imported_all()`.
**Re-import on reconnection** (DC-2, OQ-27): `from_call` runs automatically on
connection establishment. The overlay is per-connection (Layer 2, ADR-024), so
a stale overlay dies with the connection; re-import on reconnect is naturally
scoped to the new connection. This is the v1 default; explicit re-import via a
future `CallConnection::refresh()` is additive.
**Namespace collision** (DC-3, OQ-28): optional prefix, default no prefix,
collision = error. A node importing from two remotes that both expose
`/container/exec` without prefixes should fail loudly. The operator adds
prefixes when they know they're importing from multiple sources.
**Trust is transitive** (recorded in `operation-registry.md`): a
`from_call`-imported operation executes the remote node's code, not yours.
The scoped env (ADR-015) bounds *which* operations are reachable, not *what*
they do. `from_call` means "I trust the remote node as much as my own
handlers." The abort cascade (ADR-016) crosses the node boundary transparently
through the forwarding handler's `parent_request_id`.
### from_jsonschema
Schema-only registration: produces `HandlerRegistration` bundles with no
handler (`FromJsonSchema` provenance). Used for validation, discovery, and
composition-graph construction without a runtime — type-checking a composition
plan without executing it, building a UI of available operations without
standing up the transports, etc.
```rust
pub fn from_jsonschema(
spec: OperationSpec,
schema: serde_json::Value,
) -> HandlerRegistration;
```
Distinct from `from_call` (gap analysis DC-5, confirmed not a decision):
| | `from_jsonschema` | `from_call` |
|---|---|---|
| Schema source | Provided directly (caller fetches, passes in) | Discovered over wire (`services/list` + `services/schema`) |
| Handler at call time | None (schema-only, `FromJsonSchema` provenance) | Forwards over QUIC (`FromCall` provenance, leaf) |
| Use case | Type validation, discovery, composition graph construction | Actually invoking remote operations |
Keeping them separate preserves the "schema-only, no execution" use case
(type checking, safe composition planning without runtime).
### OperationAdapter trait
The shared shape across import-style adapters. The trait lives in
`alknet-call` (where the types live); the implementations live where their
transport dependencies live (see "Adapter Location Map" below).
```rust
#[async_trait]
pub trait OperationAdapter: Send + Sync {
async fn import(&self) -> Result<Vec<HandlerRegistration>, AdapterError>;
}
```
The trait is **async** because `from_call` requires async discovery
(`services/list` + `services/schema` over a QUIC connection). Sync adapters
(`from_openapi`, `from_mcp` reading a static spec) trivially satisfy an async
trait — their `import()` bodies contain no `.await` points. This is locked by
ADR-017 §5.
The **error type** (DC-4, OQ-26) is `Result<Vec<HandlerRegistration>,
AdapterError>` where `AdapterError` is a crate-level enum covering the
failure modes real implementations hit: discovery transport failure
(`from_call` remote unreachable), schema parse failure (`from_openapi`,
`from_jsonschema`), unauthorized (HTTP 401 for `from_openapi`,
`from_mcp`). The exact `AdapterError` variants are the two-way-door
remainder; the *presence* of an error type is filled in here. ADR-017 §5
showed `async fn import(&self) -> Vec<HandlerRegistration>` with no error
type; the spec omitted the error type as an implementation-detail two-way
door, recorded here.
Implementations:
- `FromCall` — QUIC-backed (in `alknet-call`).
- `FromJsonSchema` — pure parse, no transport (in `alknet-call`).
- `FromOpenAPI` — HTTP-backed (in `alknet-http`).
- `FromMCP` — MCP streamable-HTTP-backed (in `alknet-http`, feature-gated).
The `to_*` adapters (`to_openapi`, `to_mcp`) are outbound projections, not
`OperationAdapter` implementations — they consume the registry, they don't
produce entries for it (ADR-017 §5).
### Adapter Location Map
The decomposition principle: **the adapter trait lives where the types live
(`alknet-call`); the adapter implementations live where their transport
dependencies live.**
```
alknet-call (lean — no HTTP client, no HTTP server)
├── OperationAdapter trait (the contract — async, per ADR-017 §5)
├── from_call (QUIC — discovers remote ops via call protocol)
├── from_jsonschema (pure parse — caller fetches the doc, passes it in)
└── CallClient (outbound connection opener — the #1 gap)
alknet-http (owns HTTP server + HTTP client — separate crate, separate Phase 0)
├── ProtocolHandler for h2/http1.1/h3 (axum server — inbound HTTP)
├── from_openapi (parse OpenAPI doc + reqwest forwarding handler)
├── to_openapi (generate OpenAPI doc from local registry)
├── from_mcp (feature-gated) (import remote MCP tools over streamable HTTP — reqwest)
└── to_mcp (feature-gated) (expose local ops as MCP tools over streamable HTTP — axum)
Not built: MCP stdio transport
— stdio = spawn arbitrary executable = built-in RCE ("download untrusted MCP servers")
— streamable HTTP is the only supported MCP transport in alknet
— recorded as an explicit security position, not a feature gap
```
`alknet-call` never sees the HTTP client. The `from_openapi`/`from_mcp`
forwarding handlers are opaque `Arc<dyn Handler>` from the registry's
perspective — constructed by `alknet_http::from_openapi()` at registration
time, stored in `HandlerRegistration`, dispatched by the `CallAdapter` which
doesn't know reqwest is involved. `alknet-call` stays lean (no reqwest, no
axum); `alknet-http` owns both HTTP directions.
**ADR-003 dependency note**: `alknet-http` implementing `from_openapi`/
`from_mcp` means `alknet-http` depends on `alknet-call` (for `OperationSpec`,
`Handler`, `HandlerRegistration`, `OperationAdapter`). ADR-003's rule is "no
handler crate depends on another handler crate" — but `alknet-call` is both
a handler *and* the protocol foundation that `alknet-agent` and `alknet-napi`
already consume. `alknet-http` depending on `alknet-call` is "HTTP uses the
call protocol types," not "HTTP depends on SSH." This is within the spirit of
ADR-003 (`alknet-call` is protocol-foundation, not a peer handler). The
`alknet-http` spec should note this explicitly; a one-line amendment to
ADR-003 clarifying that `alknet-call` is a protocol-foundation crate is
deferred to the `alknet-http` Phase 0.
### No-Env-Vars Invariant
The architectural mechanism for the env-var problem in downstream consumers
(the Rust port of Vercel's AI SDK at `/workspace/aisdk/`, whose providers all
read `std::env::var("OPENAI_API_KEY")` in their `Default` impls). The fix is
**not** to modify those consumers — it's that the env-var path is never taken
because the assembly layer never calls `Default::default()`.
The credential injection path:
```
vault (seed)
→ assembly layer (derive + decrypt at startup, per ADR-014/019/025)
→ Capabilities (non-serializable, zeroized, immutable — ADR-014)
→ HandlerRegistration.capabilities (ADR-022, the registration bundle)
→ OperationContext.capabilities (per-request, populated by dispatch
path from the bundle — ADR-022 §6)
→ from_openapi handler reads context.capabilities.get("openai")
→ injects into HTTP Authorization header
→ reqwest request goes out with vault-derived credential
```
The `from_openapi`/`from_mcp` forwarding handlers (in `alknet-http`) are the
credential injection point. They read from `context.capabilities`, not from
`std::env::var`. The downstream consumers' `Default` impls reading env vars
are simply never called — the assembly layer constructs providers with
vault-derived credentials through the builder API, or the provider's HTTP
calls are routed through `from_openapi` operations that carry the credential
in `Capabilities`.
**This is a spec-level invariant in `alknet-call`, not a runtime convention.**
The dispatch path (`build_root_context` and `OperationEnv::invoke()` per
ADR-022 §6) populates `OperationContext.capabilities` from the registration
bundle. The invariant is: *no handler reads outbound credentials from any
source other than `OperationContext.capabilities`.* This is already the
architectural intent of ADR-014; this document records it as an explicit
invariant that the `from_openapi`/`from_mcp` handler implementations (in
`alknet-http`) are verified against.
### Exchange-of-Operations Pattern (Runner / Container Service)
The canonical downstream pattern this completion unblocks, recorded here so
Phase 1 specs can reference it. Concrete example: the container service at
`/workspace/@alkdev/dispatch` (axum + russh SSH client for "reverse git
runner" over Docker/vast.ai) gets rewritten as a call-protocol service.
**Bilateral exchange**:
```
Container service (runs on a vast.ai/docker instance):
Defines Local ops: /container/exec, /container/list, /container/logs...
(real handlers — calls bollard or vast.ai API)
Connects to hub as a CallClient (outbound connection — runner pattern)
Hub (central server):
Runs CallAdapter (server) on alknet/call (already implemented)
When the container service connects:
hub runs from_call → discovers /container/* via services/list + services/schema
registers them as FromCall provenance (leaf, forwarding handlers) in the
connection's Layer 2 overlay (ADR-024)
Now the hub (or anything connected to the hub) can call /container/exec
The from_call handler forwards over the connection back to the container service
Bilateral: the container service ALSO runs from_call against the hub,
discovers the hub's External ops, and can call them.
Connection direction (container → hub) is independent of call direction
(both can call each other) per ADR-017 §2.
```
**What this requires**:
1. `CallClient` — the container service uses it to open the outbound
connection to the hub. The #1 gap.
2. `from_call` — both sides run it to populate their Layer 2 overlays with
the other side's `External` ops. The #2 gap.
3. `OperationAdapter` trait — `from_call` implements it. The #3 gap (enabling,
not blocking — `from_call` can be built as a free function before the trait
exists, but the trait is needed for `alknet-http`'s adapters).
**Why the container service doesn't need alknet-ssh**: under the call
protocol, the container service is a `CallClient` that dials the hub's
`alknet/call` ALPN directly over QUIC — no SSH in the loop. SSH port
forwarding becomes the *transitional* mechanism for targets that can't run a
call-protocol client (the `alknet-ssh` phase-0 findings document this
transition). Once the container service runs a `CallClient`, SSH is out of
the path entirely.
This is the "dev runner" pattern: a call-protocol client that connects back
to a hub and exposes core dev tools (bash, fs, etc.) as operations. The agent
service (`alknet-agent`, downstream) is the consumer that orchestrates these
via `env.invoke()`.
## Implementation Priority Order
Based on the gap analysis and the downstream unblock chain:
1. **`CallClient`** (critical) — outbound connection opener. Without it, no
runner, no container service, no bilateral exchange. Reuses the existing
`CallConnection` for the dispatch loop; adds only the
connection-establishment + credential-handling half. The single
highest-value piece of work in the entire `alknet-call` completion.
2. **`from_call`** (critical, depends on `CallClient`) — consumes the
already-implemented `services/list` + `services/schema` discovery API.
3. **`OperationAdapter` trait** (enabling) — the async trait. Small,
standalone, unblocks `alknet-http` Phase 1.
4. **`from_jsonschema`** (medium, standalone) — schema-only registration, no
handler. Small.
5. **DC-1 resolution** (peer-scoped registry filtering, ADR-028) — the
security dimension of `CallClient`'s registry. Addressed in parallel with
#1 — it's a filtering layer on the registry the `CallClient` exposes, not
a blocker for the connection-establishment work.
## What This Completion Unblocks
| Downstream crate | What it needs from alknet-call | Status without completion |
|-------------------|-------------------------------|--------------------------|
| alknet-http | `OperationAdapter` trait (to implement `from_openapi`/`from_mcp`) | Blocked — can't define HTTP-backed adapters without the trait |
| alknet-ssh | Stable alknet-call types (no adapter dependency) | Not blocked — ssh depends on alknet-core, not alknet-call's adapters. Proceeds in parallel. |
| alknet-agent | `CallClient` (tool dispatch), `from_call` (remote tool import), `OperationAdapter` (provider adapters) | Blocked on `CallClient` + `from_call` |
| Container service (dispatch rewrite) | `CallClient` + `from_call` | Blocked — this is the primary consumer |
| Runner pattern (dev runner, opencode runner) | `CallClient` + `from_call` | Blocked — the runner IS a `CallClient` |
| alknet-napi | `CallClient` (Node.js calls remote ops) | Blocked — NAPI projects `CallClient` to JS |
## Constraints
- **No HTTP in alknet-call.** `from_openapi`/`from_mcp`/`to_openapi`/`to_mcp`
live in `alknet-http`. The `OperationAdapter` trait and the QUIC-backed
adapters (`from_call`, `from_jsonschema`) live in `alknet-call`. See
Adapter Location Map.
- **No secret material on the wire.** `CallCredentials` carries vault-derived
material for the *outbound* connection (TLS identity, auth token); the
call protocol's wire format carries no private keys, API keys, or decrypted
credentials (ADR-014). The no-env-vars invariant (above) is the dispatch-side
corollary.
- **Peer-scoped registry is default-deny.** A `CallClient` exposes no
operations to the remote peer unless marked remote-safe. Trusted-peer
opt-in is explicit (ADR-028).
- **`from_call` re-import is auto-on-reconnect.** v1 default; the overlay is
per-connection so re-import is naturally scoped (DC-2, OQ-27).
- **`from_call` namespace collision is an error.** Default no prefix; the
operator adds prefixes when importing from multiple sources (DC-3, OQ-28).
- **`OperationAdapter::import()` returns `Result`.** Failures surface as
`AdapterError` (DC-4, OQ-26).
- **MCP stdio transport is not built.** Streamable HTTP is the only supported
MCP transport in alknet. stdio = spawn arbitrary executable = built-in RCE.
Recorded as an explicit security position, not a feature gap.
## Design Decisions
| Decision | ADR | Summary |
|----------|-----|---------|
| Call protocol client and adapter contract | [ADR-017](../../decisions/017-call-protocol-client-and-adapter-contract.md) | `CallClient` opens connections; `from_call` imports remote ops; connection direction independent of call direction; trait is async; adapters produce `HandlerRegistration` bundles |
| Peer-scoped registry filtering (DC-1) | [ADR-028](../../decisions/028-callclient-peer-scoped-registry-filtering.md) | Default-deny; `remote_safe: bool` on `HandlerRegistration`; trusted-peer opt-in; one-way door on the security dimension |
| Secret material flow and capability injection | [ADR-014](../../decisions/014-secret-material-flow-and-capability-injection.md) | The no-env-vars invariant's foundation; capabilities injected at assembly layer |
| Handler registration, provenance, and composition authority | [ADR-022](../../decisions/022-handler-registration-provenance-and-composition-authority.md) | The registration bundle adapters produce; `composition_authority: None` for leaves |
| Operation registry layering | [ADR-024](../../decisions/024-operation-registry-layering.md) | Layer 2 per-connection overlay where `from_call` imports land |
| Privilege model and authority context | [ADR-015](../../decisions/015-privilege-model-and-authority-context.md) | Adapter-registered ops are `Internal` by default; default-deny posture |
| Abort cascade for nested calls | [ADR-016](../../decisions/016-abort-cascade-for-nested-calls.md) | Cross-node abort through `from_call` forwarding handler's `parent_request_id` |
| Operation error schemas | [ADR-023](../../decisions/023-operation-error-schemas.md) | `error_schemas` mirrored by `from_call` from remote op's spec |
| TLS identity redesign | [ADR-027](../../decisions/027-tls-identity-redesign-acme-rawkey-decoupling.md) | RFC 7250 raw key / X.509 cert dimensions of `CallCredentials` |
| HD derivation for encryption keys | [ADR-020](../../decisions/020-hd-derivation-for-encryption-keys.md) | Vault-derived TLS identity material |
| Vault key model | [ADR-026](../../decisions/026-vault-key-model-hd-derivation.md) | Vault-derived TLS identity material |
| Vault local-only dispatch | [ADR-025](../../decisions/025-vault-local-only-dispatch.md) | Vault access at assembly layer only; the credential injection path's first hop |
| Crate decomposition | [ADR-003](../../decisions/003-crate-decomposition.md) | `alknet-http` depends on `alknet-call` (protocol-foundation exception, noted in Adapter Location Map) |
| One-way door decision framework | [ADR-009](../../decisions/009-one-way-door-decision-framework.md) | Door-type classification for DC-1..4 |
## Open Questions
See [open-questions.md](../../open-questions.md) for full details.
- **OQ-25** (open, two-way): Remote-safe marking shape — `remote_safe: bool`
v1 vs per-peer allowlist vs capability-class tag. The *existence* of
filtering is locked by ADR-028; the shape is the two-way-door remainder.
- **OQ-26** (open, two-way): `AdapterError` enum variants (DC-4). The
*presence* of an error type is recorded here; the variants are
implementation-detail.
- **OQ-27** (open, two-way): `from_call` re-import trigger — auto-on-reconnect
(v1 default, recorded here) vs explicit `CallConnection::refresh()`. v1 is
auto-on-reconnect; the explicit path is additive.
- **OQ-28** (open, two-way): `from_call` namespace collision behavior — error
on collision (v1 default, recorded here) vs last-wins.
## References
- ADR-017: Call Protocol Client and Adapter Contract (the spec this document
operationally fills)
- ADR-028: Peer-Scoped Registry Filtering for CallClient Inbound Dispatch
(resolves DC-1)
- `call-protocol.md` — `CallAdapter`, `CallConnection`, dispatch loop, stream
model (the server-side complement to this document)
- `operation-registry.md` — `HandlerRegistration`, provenance, capability
injection, service discovery (the discovery API `from_call` consumes)
- `docs/research/alknet-call-completion/gap-analysis.md` — DC-1..4, the
implementation-state audit, the downstream unblock chain
- `/workspace/@alkdev/operations/` — TypeScript prior art (`from_openapi.ts`,
`from_mcp.ts`, `from_schema.ts`, `scanner.ts`)
- `/workspace/@alkdev/dispatch/` — concrete downstream consumer (container
service / "reverse git runner") this completion unblocks
- `/workspace/aisdk/` — downstream consumer (Rust port of Vercel AI SDK); the
no-env-vars invariant makes its `std::env::var` reads unreachable
- `/workspace/rust-sdk/` — MCP Rust SDK (rmcp); streamable HTTP transport for
`alknet-http`'s `from_mcp`/`to_mcp` (separate crate, separate Phase 0)
- `docs/research/alknet-ssh/phase-0-findings.md` — alknet-ssh Phase 0;
confirms ssh depends on alknet-core not alknet-call's adapters, so it
proceeds in parallel with this completion

8
docs/architecture/crates/call/operation-registry.md
View File

@@ -232,6 +232,8 @@ pub struct HandlerRegistration {
pub composition_authority: Option<CompositionAuthority>, // None for leaves
pub scoped_env: Option<ScopedOperationEnv>, // None for leaves
pub capabilities: Capabilities,
pub remote_safe: bool, // default false; ADR-028 — exposes this op to
// CallClient peers (trusted-peer mode bypasses)
}
```
@@ -632,6 +634,8 @@ The `Capabilities` type holds non-serializable, zeroized secret material. It doe
**Scoped composition env.** The `OperationEnv` given to a handler is scoped — it can only invoke a declared set of operations, set at registration on the `HandlerRegistration` bundle by the assembly layer (ADR-022). This bounds the parameterized-dispatch attack surface: a handler (or an LLM picking tools, or a quickjs sandbox) can only reach declared operations, not the entire registry. The scoped env is the reachability control; the composition authority is the authority control. Both are needed for least privilege. See ADR-015 and ADR-022.
**No-env-vars invariant.** No handler reads outbound credentials from any source other than `OperationContext.capabilities`. This is the dispatch-side corollary of the capability-injection flow above: because the dispatch path populates `OperationContext.capabilities` from the registration bundle (ADR-022 §6), and because the assembly layer constructs handlers with vault-derived credentials rather than calling `Default::default()`, downstream consumers' `std::env::var` credential reads are unreachable by construction. The full invariant, the credential injection path, and the downstream-consumer framing are recorded in [client-and-adapters.md](client-and-adapters.md); this section documents the dispatch-path mechanism that makes it enforceable.
## Constraints
- The registry is **layered by trust boundary** (ADR-024). The curated layer (`Local` provenance) is immutable after construction — adding a `Local` op requires restarting the process, which re-enters the startup trust boundary. Session (`Session`) and imported (`FromCall` etc.) ops are dynamic at their respective scopes (per-session, per-connection). The pre-ADR-024 blanket immutability claim was inherited by analogy from ADR-010's `HandlerRegistry` (ALPN-level) and did not apply to the operation registry — the TLS-config argument that justifies `HandlerRegistry` immutability does not touch the operation registry, which lives behind the single ALPN `alknet/call`.
@@ -659,6 +663,8 @@ The `Capabilities` type holds non-serializable, zeroized secret material. It doe
| Handler registration, provenance, and composition authority | [ADR-022](../../decisions/022-handler-registration-provenance-and-composition-authority.md) | Registration bundle carries provenance, composition authority, scoped env, capabilities; dispatch path reads from bundle |
| Operation registry layering | [ADR-024](../../decisions/024-operation-registry-layering.md) | Curated (static, immutable) + session and connection overlays (dynamic); `OperationEnv` as trait-object integration point; `OperationContext.env` split into `scoped_env` (data) and `env` (dispatch trait) |
| Operation error schemas | [ADR-023](../../decisions/023-operation-error-schemas.md) | Operations declare domain errors; `call.error` carries typed `details`; adapter fidelity for `from_openapi`/`to_openapi` |
| Call protocol client and adapter contract | [ADR-017](../../decisions/017-call-protocol-client-and-adapter-contract.md) | `from_call`/`from_jsonschema`/`OperationAdapter` produce `HandlerRegistration` bundles; adapter-registered ops are `Internal` leaves. Surface specced in [client-and-adapters.md](client-and-adapters.md) |
| Peer-scoped registry filtering for CallClient | [ADR-028](../../decisions/028-callclient-peer-scoped-registry-filtering.md) | Default-deny `CallClient` registry view; adds `remote_safe` marking to `HandlerRegistration` (the bundle this doc defines) |
## Open Questions
@@ -668,6 +674,8 @@ See [open-questions.md](../../open-questions.md) for full details.
- **OQ-14** (resolved): Batch is a client-side pattern of correlated `call.requested` events, not a protocol primitive.
- **OQ-16** (resolved by ADR-014): No vault operations are exposed over the call protocol for now.
- **OQ-19** (resolved): Session-scoped operation registries — agent-written operations overlaid on the curated registry via `OperationEnv` trait layering. Protocol doesn't need changes; `OperationEnv` must remain a trait. Session ops are `Session` provenance (ADR-022) — always `Internal`, compose under restricted authority scoped down at sandbox creation. Generalized by ADR-024 to cover connection-scoped overlays as well.
- **OQ-25** (open, two-way): Remote-safe marking shape — existence of default-deny `CallClient` filtering locked by ADR-028; the shape (the `remote_safe: bool` field this doc's `HandlerRegistration` gains vs a richer per-peer mechanism) is the two-way-door remainder. See [client-and-adapters.md](client-and-adapters.md).
- **OQ-26..28** (open, two-way): `OperationAdapter` error type, `from_call` re-import trigger, `from_call` namespace collision. v1 defaults recorded in [client-and-adapters.md](client-and-adapters.md).
## References