alknet/docs/architecture

status, last_updated

status	last_updated
draft	2026-07-08

Alknet Architecture

Current State

Pre-implementation of the storage/repo pattern. The project has completed a pivot from a three-layer model to an ALPN-as-service model. The greenfield workspace contains alknet-vault (stable — implementation complete and verified, local-only by construction per ADR-025, HD-derivation key model per ADR-026) and research/reference material. Foundational ADRs (001–035) are in place, with the call crate implemented and reviewed.

The storage and auth strategy research (docs/research/alknet-storage-strategy/findings.md) surfaced the repo/adapter pattern as the answer to cross-node state (peer identity, credentials). This has now landed as four ADRs:

• ADR-030 (PeerEntry and Identity.id decoupling): authorized_fingerprints: HashSet<String> → peers: Vec<PeerEntry>; Identity.id becomes the stable peer_id (not the fingerprint); key rotation changes the fingerprint, not the identity. Supersedes ADR-029's v1 UUID source (the one-way door — PeerId is logical, not crypto — is preserved; the source changes from UUID to Identity.id from PeerEntry). Resolves OQ-33 and the storage-boundary half of OQ-34.
• ADR-031 (CredentialStore repo trait): the second repo trait in core (alongside IdentityProvider), with InMemoryCredentialStore default adapter. Establishes the credential-persistence abstraction.
• ADR-032 (Forwarded-for identity): forwarded_for field on call.requested and OperationContext; metadata only — AccessControl::check never reads it; the from_call handler populates it. Wire-format one-way door, included with the ADR-029 migration window.
• ADR-033 (Storage boundary and repo/adapter pattern): core defines repo traits + in-memory defaults; persistence adapters are separate crates; the assembly layer wires the adapter. Resolves OQ-34's storage-boundary question. Concrete adapter shapes now committed by ADR-035 (was OQ-36).

The alknet-call crate is implemented and reviewed — both the server-side core and the client/adapter surface (207 lib + 2 integration tests passing). The alknet-core and alknet-call crate specs are in draft; the alknet-vault crate specs are stable.

alknet-http specs drafted and consistency-reviewed. The alknet-http crate (HTTP interface — h2/http/1.1 server + WebSocket browser path + from_openapi/to_openapi/from_mcp/to_mcp adapters) now has architecture specs: crates/http/ (overview, http-server, websocket, http-adapters, http-mcp, webtransport) and thirteen ADRs — ADR-036 (HTTP-to-call mapping; direct-call surface — routing superseded by ADR-047, non-routing clauses survive), ADR-037 (MCP stdio exclusion), ADR-038 (HTTP/3 + WebTransport as first-class — superseded by ADR-044; its correction of the two-way-door-as-deferral anti-pattern stands, its specific decision is reversed by the scope deferral), ADR-039 (HTTP server + client host colocated in one crate), ADR-040 (WebTransport ALPN-stream-proxy — parked per ADR-044; revives unchanged when WebTransport revives), ADR-041 (to_mcp tool-gateway pattern — 4 fixed gateway tools instead of one tool per operation, addressing LLM context tool-bloat), ADR-042 (to_openapi gateway pattern — 5 fixed gateway endpoints instead of one path per operation; per-caller AccessControl-filtered API surface; supersedes ADR-036's original to_openapi clause), ADR-043 (WebTransport as a bidirectional ALPN transport substrate — parked per ADR-044; §2/§3 transfer to WebSocket for v1), ADR-044 (defer h3/WebTransport; browsers use WebSocket for the bidirectional call-protocol path; a scope decision per ADR-009 §"What this framework is NOT"; reversal trigger = a concrete ALPN-stream-proxy use case; states the "browser is not a peer" rationale — addressability vs. bidirectionality — that amends ADR-034 §4), and ADR-045 (to_openapi published-spec versioning — info.version semver tracks the gateway endpoint contract, not the operation set; resolves OQ-39), and ADR-046 (assembly-layer custom HTTP routes on HttpAdapter — extra_routes: Option<Router> for deployment-specific endpoints like an OAI-compatible proxy; default surface unchanged, takes precedence on collision), and ADR-047 (remove the direct-call POST /{service}/{op} surface — the gateway /call is the sole invoke path; the simplified contract is the few-fixed-endpoints model, not a per-operation REST tree; ADR-036's non-routing clauses survive), and ADR-048 (WebSocket carries the native EventEnvelope call-protocol session, not the HTTP gateway shape — the gateway endpoints are HTTP-only; discovery via services/list/services/schema as call-protocol ops; clarifies the WS-path shape ADR-044 committed). ADR-003 Amendment 1 clarifies that alknet-call is a protocol-foundation crate (the alknet-http → alknet-call dependency edge). A consistency review pass corrected drift from the mid-spec pivot (the to_openapi gateway pattern landed in the prose but not in cross-references; the WebTransport specs inherited the OpenAPI/MCP direction assumption that doesn't hold for the call protocol) — ADR-036's to_openapi clause is now amended as superseded by ADR-042, ADR-034 §5's "deferral bucket" wording is corrected (the decision stands), and the http specs now name the one-directional HTTP projection vs. the bidirectional WebSocket (and, when revived, WebTransport) substrate. The WebSocket path is promoted to its own spec (websocket.md) with the native-session-vs-gateway distinction made explicit (ADR-048). The specs are in draft; implementation has not started. Two open questions carried: OQ-38 (WebTransport standalone relay service scope — distinct from the in-process ALPN-stream-proxy resolved by ADR-040) and OQ-40 (reqwest client config — since resolved by the ClientWithMiddleware + middleware stack design). OQ-39 (to_openapi published-spec versioning) is resolved by ADR-045.

Next step: The storage/repo-pattern ADRs (030–033) are accepted and amend the core and call specs. The next implementation phase is the ADR-029 migration (peer-keyed overlays, PeerRef routing, retire remote_safe/trusted_peer) with the ADR-030 PeerEntry change and the ADR-032 forwarded_for field folded in — the OperationContext, from_call handler, and AuthPolicy are all under edit, making this the cheapest window. After that: alknet-http implementation (specs drafted; h3/WebTransport deferred per ADR-044, browser bidirectional path uses WebSocket), which consumes the CredentialStore trait and the OperationAdapter contract. The alknet-ssh crate (the other post-core crate, specced in parallel) proceeds independently — it depends on alknet-core, not alknet-call.

alknet-tty specs drafted. The alknet-tty crate (terminal session protocol handler — ProtocolHandler on alknet/tty, two-carriage wire format with a raw chunk codec + JSON control channel, backend-agnostic via a TtyBackend trait) now has architecture specs: crates/tty/ (overview, tty-wire, tty-backend, tty-adapter, tty-local) and six ADRs — ADR-052 (wire format: alknet/tty ALPN, JSON negotiation frame then raw chunks, fixed channel set 0-3, control as JSON), ADR-053 (TtyBackend trait + TtyHandle; exit_code as a Future; backends need not be natively async — REQ-TTY-01 from the local-PTY POC; TtyControlHandle newtype for Clone-ability — Clone is not object-safe), ADR-054 (alknet-tty-local sibling crate behind a local feature re-export; PTY vs pipe per-session; the runner pattern preserved), ADR-055 (exit code on a stream_type 3 control chunk; "exit chunk is last" invariant; adapter owns the ordering), ADR-056 (backend cleanup contract: dropping the exit_code future on session cancel MUST kill the session target — closes the orphaned-process gap the local-PTY POC surfaced for the waiter thread), ADR-057 (alknet-tty does not depend on alknet-call — the negotiation framing is self-contained; the earlier "reuse FrameFramedReader" claim was unsound because the utility is welded to EventEnvelope deserialization). The specs are grounded in the alknet-docker POC (docs/research/alknet-docker/poc-summary.md) and the alknet-tty POC (/workspace/alknet-tty-poc/, built 2026-07-05), which validated the wire format, the control channel, the local-PTY bridge, and the signal-delivery contract (REQ-TTY-02). The docker and SSH backends are future crates that implement the TtyBackend trait — out of scope for this spec set, but the trait shape is committed so they can be built against it.

alknet-docker specs drafted. The alknet-docker crate (docker operations on the shared alknet/call ALPN + DockerTtyBackend behind a tty feature) now has architecture specs: crates/docker/ (overview, docker-operations, docker-tty-backend) and six ADRs — ADR-058 (docker ops register on alknet/call, not a separate alknet/docker ALPN; the raw-carriage handoff the POC struggled with is dissolved by the alknet-tty extraction — interactive attach moved to alknet/tty via DockerTtyBackend, no carriage field on call.requested), ADR-059 (bollard 0.21, verified current on crates.io; features http+pipe+time, no ssl/ssh/websocket/buildkit — single-host by construction, fleet is a call-protocol concern), ADR-060 (ADR-050 application to bollard: alknet.managed/alknet.owner labels; list owned_only flag; hosted-services operator role via the static-resource fallback; handler-driven revoke on remove with autonomous-death tolerance), ADR-061 (DockerTtyBackend in alknet-docker behind a tty feature, not a sibling crate; attach vs exec mode; the POC's drive_attach_raw as the reference), ADR-062 (the Docker client + OwnershipStore are closure-captured at registration time, not read from OperationContext and not smuggled through Capabilities — Capabilities is for secret material only per ADR-014; matches the from_openapi pattern), ADR-063 (non-interactive exec puts { "exitCode": N, "terminal": true } on a final call.responded before call.completed — call.completed stays empty, ADR-012 unchanged). The specs are grounded in the alknet-docker POC (docs/research/alknet-docker/poc-summary.md, /workspace/alknet-docker-poc/), which validated the hard parts (interactive attach, logs subscription, exec with exit code); the remaining lifecycle operations are mechanical bollard wrapping. The two use cases — disposable dev containers (coordinator-spawned, ownership-recorded) and long-running hosted services (operator-managed, static-resource fallback, per /workspace/system/dev1/docker.md) — both work through one AccessControl model (ADR-050/060). The DockerTtyBackend fills the TtyBackend row the alknet-tty spec left open. Four OQs (048–051) track deferred scope: network/volume ops, buildkit, system events subscription, and the full CreateContainerOptions surface (deferred to v1 implementation).

Architecture Documents

Document	Status	Description
overview.md	draft	Workspace-level overview, crate graph, shared types, design principles
open-questions.md	draft	OQ index — theme-grouped tables + Deferred/Blocked section; per-OQ files in questions/
crates/core/README.md	draft	alknet-core crate index
crates/core/core-types.md	draft	ProtocolHandler, HandlerError, Connection, BiStream, StreamError
crates/core/endpoint.md	draft	ALPN router, HandlerRegistry, accept loop, shutdown
crates/core/auth.md	draft	AuthContext, Identity, IdentityProvider, AuthToken, resolution flow
crates/core/config.md	draft	StaticConfig, DynamicConfig, ArcSwap, ConfigReloadHandle
crates/call/README.md	draft	alknet-call crate index
crates/call/call-protocol.md	draft	CallAdapter, EventEnvelope framing, stream model, PendingRequestMap, bidirectional calls, streaming subscribe example
crates/call/operation-registry.md	draft	OperationSpec, Handler, OperationRegistry, AccessControl, capability injection, service discovery, irpc integration
crates/call/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
crates/http/README.md	draft	alknet-http crate index
crates/http/overview.md	draft	Crate purpose, two roles (server + client host), dependencies, adapter location map
crates/http/http-server.md	draft	HttpAdapter for h2/http1.1 + WebSocket upgrade route, axum over QUIC, Bearer auth, stealth, /healthz
crates/http/websocket.md	draft	WebSocket browser bidirectional path — native EventEnvelope call-protocol session (not the gateway shape); framing, dispatch, bidirectionality, connection-local overlay, browsers-are-not-peers, deferred from_wss
crates/http/http-adapters.md	draft	from_openapi (reqwest; JSON + YAML input per ADR-051) and to_openapi (projection); no-env-vars injection point
crates/http/http-mcp.md	draft	from_mcp / to_mcp (feature-gated), streamable-HTTP-only, stdio exclusion
crates/http/webtransport.md	deferred	h3/WebTransport handler — deferred per ADR-044; browser bidirectional path uses WebSocket (see http-server.md). Spec kept intact for revival.
crates/tty/README.md	draft	alknet-tty crate index
crates/tty/overview.md	draft	Crate purpose, two-carriage model, dependencies, ALPN, backend location map, feature gates
crates/tty/tty-wire.md	draft	Wire format: negotiation frame (JSON carriage), raw chunk codec ([stream_type: u8][length: u32 be][payload]), control channel (stream_type 3, JSON control messages), sentinels
crates/tty/tty-backend.md	draft	TtyBackend trait, TtyParams, TtyHandle, TtyControl — the backend inversion point. Carries REQ-TTY-01 (backends need not be natively async)
crates/tty/tty-adapter.md	draft	TtyAdapter (ProtocolHandler on alknet/tty): session lifecycle, three-pump bidirectional driver, negotiation errors, exit-chunk ordering (ADR-055), access control
crates/tty/tty-local.md	draft	alknet-tty-local sibling crate: LocalTtyBackend via portable_pty (PTY) and std::process::Command (pipe/runner). Carries REQ-TTY-02 (signal forwarding to the process group)
crates/docker/README.md	draft	alknet-docker crate index
crates/docker/overview.md	draft	Crate purpose, two-role design (call ops + DockerTtyBackend), dependencies, ALPN, label namespace, feature gates, assembly-layer wiring
crates/docker/docker-operations.md	draft	Operation surface: lifecycle (Query/Mutation), logs/exec/pull (Subscription via StreamingHandler), access control (ADR-050/060), label namespace, teardown coupling
crates/docker/docker-tty-backend.md	draft	DockerTtyBackend (impl TtyBackend): attach vs exec mode, TtyHandle field mapping, TtyControl → bollard resize/signal, exit_code Drop-kill (ADR-056)
crates/vault/README.md	stable	alknet-vault crate index
crates/vault/mnemonic-derivation.md	stable	BIP39, SLIP-0010, BIP-0032, derivation paths, key types
crates/vault/encryption.md	stable	AES-256-GCM, EncryptedData, key versioning, salt (Phase B reserved)
crates/vault/service.md	stable	VaultServiceHandle lifecycle, direct dispatch, cache, error model
crates/vault/protocol.md	stable	DerivedKey redaction, KeyType, serialization behavior

ADR Table

ADR	Title	Status
001	ALPN-Based Protocol Dispatch	Accepted
002	ProtocolHandler Trait	Accepted
003	Crate Decomposition	Accepted
004	Auth as Shared Core (IdentityProvider)	Accepted
005	irpc as Call Protocol Foundation	Accepted
006	ALPN String Convention and Connection Model	Accepted
007	BiStream Type Definition	Accepted
008	Vault Integration Point	Accepted
009	One-Way Door Decision Framework	Accepted
010	ALPN Router and Endpoint	Accepted
011	AuthContext Structure and Resolution Flow	Accepted
012	Call Protocol Stream Model	Accepted
013	Rust as Canonical Implementation Language	Accepted
014	Secret Material Flow and Capability Injection	Accepted
015	Privilege Model and Authority Context	Accepted
016	Abort Cascade for Nested Calls	Accepted
017	Call Protocol Client and Adapter Contract	Accepted
018	Vault as Standalone Crate	Accepted
019	Vault Assembly-Layer-Only Access	Accepted
020	HD Derivation for Encryption Keys	Accepted
021	Key Rotation via Version-Indexed Paths	Accepted
022	Handler Registration, Provenance, and Composition Authority	Accepted
023	Operation Error Schemas	Accepted
024	Operation Registry Layering	Accepted
025	Vault Local-Only Dispatch	Accepted
026	Vault Key Model — HD Derivation	Accepted
027	TLS Identity Redesign — ACME + RawKey Decoupling	Accepted
028	Peer-Scoped Registry Filtering for CallClient Inbound Dispatch	Accepted → Superseded by ADR-029
029	Peer-Graph Routing Model for alknet-call Composition	Accepted (Assumption 1's PeerId source superseded by ADR-030)
030	PeerEntry and Identity.id Decoupling	Accepted (supersedes ADR-029 Assumption 1's UUID source)
031	CredentialStore Repo Trait	Accepted
032	Forwarded-For Identity (Metadata, Not Authority)	Accepted
033	Storage Boundary and Repo/Adapter Pattern	Accepted
034	Outgoing-Only X.509 and the Three Peer Roles	Accepted
035	Concrete Persistence Adapter Shapes — Read/Write Split, honker+SQLite	Accepted
036	HTTP-to-Call Operation Mapping	Proposed — routing decision superseded by ADR-047 (non-routing clauses survive: SSE, auth, /healthz, stealth, error mapping)
037	MCP Stdio Transport Exclusion	Proposed
038	HTTP/3 and WebTransport as First-Class HTTP Transports	Proposed → Superseded by ADR-044
039	HTTP Server and Client Host Colocated in alknet-http	Proposed
040	WebTransport ALPN-Stream-Proxy	Proposed — parked (implementation deferred per ADR-044)
041	MCP Tool-Gateway Pattern for to_mcp	Proposed
042	OpenAPI Gateway Pattern for to_openapi	Proposed
043	WebTransport as a Bidirectional ALPN Transport Substrate	Proposed — parked (implementation deferred per ADR-044; §2/§3 transfer to WebSocket)
044	Defer h3/WebTransport; Browsers Use WebSocket	Accepted
045	to_openapi Gateway-Spec Versioning	Proposed
046	Assembly-Layer Custom HTTP Routes on HttpAdapter	Proposed
047	Remove the Direct-Call HTTP Surface; Gateway Is the Sole Invoke Path	Proposed
048	WebSocket Carries the Native Call-Protocol Session, Not the Gateway Shape	Accepted
049	Streaming Handler for Subscription Operations	Accepted
050	Dynamic Resource Ownership for Runtime-Spawned Resources	Accepted
051	YAML Input Format for from_openapi	Accepted
052	alknet-tty Wire Format and Two-Carriage Model	Accepted
053	TtyBackend Trait and TtyHandle — the Backend Inversion Point	Accepted
054	Local TTY Backend as a Sibling Crate (alknet-tty-local)	Accepted
055	Exit Code on a Control Chunk (the Last Chunk Before Stream Close)	Accepted
056	Backend Cleanup on Session Cancel (Drop of exit_code Kills)	Accepted
057	alknet-tty Does Not Depend on alknet-call (Self-Contained Negotiation Framing)	Accepted
058	alknet-docker Registers on alknet/call (No Separate ALPN)	Accepted
059	bollard 0.21 Dependency and Feature Selection	Accepted
060	Container Resource Model and Label Namespace	Accepted
061	DockerTtyBackend in alknet-docker	Accepted
062	Docker Client and OwnershipStore Injection via Closure Capture	Accepted
063	Exit Code on a Terminal call.responded for Non-Interactive Exec	Accepted

Open Questions

Open questions are tracked in open-questions.md — an index of theme-grouped tables (51 OQs across 16 themes) with a cross-theme Deferred / Blocked section surfacing the safe-exit deferrals. Each OQ lives in its own file under questions/ (NNN-slug.md, mirroring the ADR convention).

Document Lifecycle

Status	Meaning	Transitions
draft	Under active development. May change significantly.	→ reviewed when open questions are resolved
reviewed	Architecture is final. Implementation may begin. Changes require review.	→ stable when implementation is complete and verified
stable	Locked. Changes require review and may warrant an ADR.	→ deprecated when superseded
deprecated	Superseded. Kept for reference.	Removed when no longer referenced

References

• Pivot proposal: docs/research/pivot/alpn-service-architecture.md
• Cleanup plan: docs/research/pivot/cleanup-plan.md
• SDD process: docs/sdd_process.md
• Reference implementation: /workspace/@alkdev/alknet-main/