Diagnoses a conflation in the pre-ADR-024 spec: the OperationRegistry inherited immutability by analogy from ADR-010's HandlerRegistry (ALPN-level), but the TLS-config argument that justifies HandlerRegistry immutability does not apply to the operation registry, which lives behind a single ALPN (alknet/call). This made from_call (which discovers ops over a live connection at runtime) structurally incompatible with the blanket immutability claim. ADR-024 layers the operation registry by trust boundary: curated (Local) ops are static and immutable — the startup trust boundary is where their composition authority is granted; session (Session) and imported (FromCall etc.) ops are dynamic at their respective scopes (per-session, per-connection) — their trust boundaries are per-scope, not per-startup. The principle: immutability follows the trust boundary. Immutability is the security control for composing ops (can escalate privilege); provenance + composition authority are the controls for non-composing ops (can't escalate). The OperationEnv trait becomes the integration point (Arc<dyn OperationEnv>), following the IdentityProvider precedent (ADR-004): the CallAdapter composes the root OperationContext.env per incoming call from the active layers (curated base + connection overlay + session overlay). Children inherit the parent's composite env by Arc::clone — overlay composition happens once at the root and propagates through the composition tree. Resolves review #002 C6 (OperationContext.env type identity crisis): the field is split into scoped_env: ScopedOperationEnv (reachability data, from the registration bundle) and env: Arc<dyn OperationEnv + Send + Sync> (dispatch trait object). One field was being used as two different types (reachability set with .allows() and dispatch trait with .invoke()); Localizes W4 (hot-swap ↔ registry mutability coupling) to the connection scope: no global mutable registry to hot-swap; overlays replace naturally with connect/disconnect and session start/end. Schema-drift on reconnect is a per-connection overlay-rebuild concern, not a global hot-swap protocol. Partially addresses W3 (CallClient registry security): the registry-shape sub-question is resolved by the overlay model; the capability-exposure sub-question (what capabilities a remote peer can trigger) remains for ADR-017 — ADR-024 does not overclaim resolution there. Amends OQ-04 to scope its immutability claim to the HandlerRegistry and cross-reference ADR-024 for the operation registry. Generalizes OQ-19's session-overlay mechanism to also cover connection-scoped remote imports — both are per-scope dynamic overlays on the static curated base, using the same trait-layering mechanism.
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111 lines
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Markdown
---
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status: draft
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last_updated: 2026-06-22-20
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---
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# Alknet Architecture
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## Current State
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**Pre-implementation.** The project has completed a pivot from a three-layer model to an ALPN-as-service model. The greenfield workspace contains only `alknet-vault` (stable — implementation exists) and research/reference material. Foundational ADRs (001–024) are in place, including the BiStream type definition (ADR-007), vault integration (ADR-008), ALPN router/endpoint (ADR-010), AuthContext structure (ADR-011), call protocol stream model (ADR-012), Rust as canonical implementation language (ADR-013), secret material flow with capability injection (ADR-014), privilege model with authority context (ADR-015), abort cascade for nested calls (ADR-016), call protocol client and adapter contract (ADR-017), vault standalone crate (ADR-018), vault assembly-layer-only access (ADR-019), HD derivation for encryption keys (ADR-020), key rotation via version-indexed paths (ADR-021), handler registration, provenance, and composition authority (ADR-022), operation error schemas (ADR-023), and operation registry layering (ADR-024). ADR-024 resolves the registry mutability question that ADR-022/017 surfaced (`from_call` imports require a runtime-mutable home) and the `OperationContext.env` type identity crisis (review #002 C6), by layering the registry by trust boundary (curated static + session/connection dynamic overlays) and making `OperationEnv` a trait-object integration point. The alknet-core, alknet-call, and alknet-vault crate specs are in draft.
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**Next step**: Continue working through review #002's remaining Tier 4 findings (vault security decisions, guard clauses, ADR-writing exercises, smaller spec decisions). All open questions for the core and call crates are resolved; the vault crate has one deferred OQ (OQ-21, remote vault administration) that does not block implementation.
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## Architecture Documents
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| Document | Status | Description |
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|----------|--------|-------------|
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| [overview.md](overview.md) | draft | Workspace-level overview, crate graph, shared types, design principles |
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| [open-questions.md](open-questions.md) | draft | Centralized OQ tracker with door-type classifications |
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| [crates/core/README.md](crates/core/README.md) | draft | alknet-core crate index |
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| [crates/core/core-types.md](crates/core/core-types.md) | draft | ProtocolHandler, HandlerError, Connection, BiStream, StreamError |
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| [crates/core/endpoint.md](crates/core/endpoint.md) | draft | ALPN router, HandlerRegistry, accept loop, shutdown |
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| [crates/core/auth.md](crates/core/auth.md) | draft | AuthContext, Identity, IdentityProvider, AuthToken, resolution flow |
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| [crates/core/config.md](crates/core/config.md) | draft | StaticConfig, DynamicConfig, ArcSwap, ConfigReloadHandle |
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| [crates/call/README.md](crates/call/README.md) | draft | alknet-call crate index |
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| [crates/call/call-protocol.md](crates/call/call-protocol.md) | draft | CallAdapter, EventEnvelope framing, stream model, PendingRequestMap, bidirectional calls, streaming subscribe example |
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| [crates/call/operation-registry.md](crates/call/operation-registry.md) | draft | OperationSpec, Handler, OperationRegistry, AccessControl, capability injection, service discovery, irpc integration |
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| [crates/vault/README.md](crates/vault/README.md) | draft | alknet-vault crate index |
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| [crates/vault/mnemonic-derivation.md](crates/vault/mnemonic-derivation.md) | draft | BIP39, SLIP-0010, BIP-0032, derivation paths, key types |
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| [crates/vault/encryption.md](crates/vault/encryption.md) | draft | AES-256-GCM, EncryptedData, key versioning, salt (Phase B reserved) |
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| [crates/vault/service.md](crates/vault/service.md) | draft | VaultServiceHandle lifecycle, actor dispatch, cache, error model |
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| [crates/vault/protocol.md](crates/vault/protocol.md) | draft | VaultProtocol irpc messages, DerivedKey redaction, serialization |
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## ADR Table
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| ADR | Title | Status |
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|-----|-------|--------|
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| [001](decisions/001-alpn-protocol-dispatch.md) | ALPN-Based Protocol Dispatch | Accepted |
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| [002](decisions/002-protocol-handler-trait.md) | ProtocolHandler Trait | Accepted |
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| [003](decisions/003-crate-decomposition.md) | Crate Decomposition | Accepted |
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| [004](decisions/004-auth-as-shared-core.md) | Auth as Shared Core (IdentityProvider) | Accepted |
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| [005](decisions/005-irpc-as-call-protocol-foundation.md) | irpc as Call Protocol Foundation | Accepted |
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| [006](decisions/006-alpn-convention-and-connection-model.md) | ALPN String Convention and Connection Model | Accepted |
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| [007](decisions/007-bistream-type-definition.md) | BiStream Type Definition | Accepted |
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| [008](decisions/008-secret-service-integration.md) | Vault Integration Point | Accepted |
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| [009](decisions/009-one-way-door-decision-framework.md) | One-Way Door Decision Framework | Accepted |
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| [010](decisions/010-alpn-router-and-endpoint.md) | ALPN Router and Endpoint | Accepted |
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| [011](decisions/011-authcontext-structure.md) | AuthContext Structure and Resolution Flow | Accepted |
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| [012](decisions/012-call-protocol-stream-model.md) | Call Protocol Stream Model | Accepted |
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| [013](decisions/013-rust-canonical-implementation.md) | Rust as Canonical Implementation Language | Accepted |
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| [014](decisions/014-secret-material-flow-and-capability-injection.md) | Secret Material Flow and Capability Injection | Accepted |
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| [015](decisions/015-privilege-model-and-authority-context.md) | Privilege Model and Authority Context | Accepted |
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| [016](decisions/016-abort-cascade-for-nested-calls.md) | Abort Cascade for Nested Calls | Accepted |
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| [017](decisions/017-call-protocol-client-and-adapter-contract.md) | Call Protocol Client and Adapter Contract | Accepted |
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| [018](decisions/018-vault-standalone-crate.md) | Vault as Standalone Crate | Accepted |
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| [019](decisions/019-vault-assembly-layer-only.md) | Vault Assembly-Layer-Only Access | Accepted |
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| [020](decisions/020-hd-derivation-for-encryption-keys.md) | HD Derivation for Encryption Keys | Accepted |
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| [021](decisions/021-key-rotation-via-version-indexed-paths.md) | Key Rotation via Version-Indexed Paths | Accepted |
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| [022](decisions/022-handler-registration-provenance-and-composition-authority.md) | Handler Registration, Provenance, and Composition Authority | Accepted |
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| [023](decisions/023-operation-error-schemas.md) | Operation Error Schemas | Accepted |
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| [024](decisions/024-operation-registry-layering.md) | Operation Registry Layering | Accepted |
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## Open Questions
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See [open-questions.md](open-questions.md) for the full tracker.
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**Resolved one-way doors:**
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- **OQ-01**: BiStream type — trait with Connection parameter (ADR-007)
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- **OQ-02**: AuthContext timing — hybrid model (ADR-004)
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- **OQ-03**: ALPN naming — `alknet/` prefix, no version (ADR-006)
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- **OQ-05**: Multi-connectivity endpoint — quinn + iroh, both feature-gated (ADR-010)
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- **OQ-06**: ALPN per connection, not per stream (ADR-006)
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- **OQ-08**: Vault integration — CLI-embedded, assembly-layer only (ADR-008, ADR-014)
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- **OQ-16**: Safe vault operations for call protocol exposure — none for now (ADR-014)
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- **OQ-18**: Privilege model — `internal` = authority switch, External/Internal visibility, handler identity + scoped env (ADR-015)
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- **OQ-17**: Abort cascade — `call.aborted` cascades to descendants; default `abort-dependents`, `continue-running` opt-in (ADR-016)
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- **OQ-15**: Call protocol client and adapter contract — `CallClient` opens connections; `from_call` imports remote ops; connection direction independent of call direction (ADR-017)
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**Resolved two-way doors:**
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- **OQ-04**: Dynamic handler registration — static at startup (ADR-010); scoped to the `HandlerRegistry` (ALPN-level) by ADR-024, which governs `OperationRegistry` mutability separately
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- **OQ-07**: Call protocol scope — bidirectional streams, EventEnvelope, ID-based correlation (ADR-012)
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- **OQ-11**: Handler-level auth resolution observability — handlers store resolved identity on Connection (Option B); two identity scopes: connection-level (observability) and per-request (ACL)
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- **OQ-12**: TLS identity provisioning — two use cases: RFC 7250 raw keys (default, P2P) and X.509 certs (domain-hosted, browsers). ACME is a proven pattern.
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- **OQ-13**: Operation path format — `/{service}/{op}` is the correct design for alknet-call, not a simplification
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- **OQ-14**: Batch operation semantics — multiple correlated `call.requested` events is the correct protocol design, not a simplification
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- **OQ-19**: Session-scoped registries — agent-written operations via `OperationEnv` trait layering; protocol doesn't need changes; `OperationEnv` must remain a trait. Generalized by ADR-024 to cover connection-scoped overlays as well.
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- **OQ-20**: Encryption key derivation — HD derivation from BIP39 seed, not PBKDF2; salt field unused in v2 (wire-format compat) (ADR-020)
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- **OQ-22**: Key rotation — version-indexed derivation paths; `rotate` method re-encrypts (ADR-021)
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- **OQ-23**: Handler identity registration path — registration bundle with provenance, composition authority, scoped env, capabilities (ADR-022)
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- **OQ-24**: Operation error schemas — declared domain errors with typed `details` payload; adapter fidelity for `from_openapi`/`to_openapi` (ADR-023)
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**Deferred (not active):**
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- **OQ-09**: WASM target boundaries — design constraint, not deliverable
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- **OQ-10**: Git adapter scope — start with smart protocol, add ERC721 later
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- **OQ-21**: Remote vault access — protocol is remote-capable by construction (irpc `RemoteService`); enabling is a server-setup change with an auth-wrapping handler in the assembly layer; `Unlock`/`Lock` are local-only
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## Document Lifecycle
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| Status | Meaning | Transitions |
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|--------|---------|-------------|
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| `draft` | Under active development. May change significantly. | → `reviewed` when open questions are resolved |
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| `reviewed` | Architecture is final. Implementation may begin. Changes require review. | → `stable` when implementation is complete and verified |
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| `stable` | Locked. Changes require review and may warrant an ADR. | → `deprecated` when superseded |
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| `deprecated` | Superseded. Kept for reference. | Removed when no longer referenced |
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## References
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- Pivot proposal: `docs/research/pivot/alpn-service-architecture.md`
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- Cleanup plan: `docs/research/pivot/cleanup-plan.md`
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- SDD process: `docs/sdd_process.md`
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- Reference implementation: `/workspace/@alkdev/alknet-main/` |