alknet/tasks/integration/phase2/stream-interface-message-interface-split.md

id, name, status, depends_on, scope, risk, impact, level

id	name	status	depends_on	scope	risk	impact	level
stream-interface-message-interface-split	Rename Interface → StreamInterface, add MessageInterface trait, remove TransportKind::Dns, restructure ListenerConfig	pending		moderate	medium	phase	implementation

Description

Rename the current Interface trait to StreamInterface, add a MessageInterface trait for request/response interfaces (HTTP, DNS), remove TransportKind::Dns from the transport enum (DNS is a MessageInterface, not a transport), restructure ListenerConfig from a flat struct to the ADR-035 enum form, and align TransportKind::WebTransport with the spec. This is the most impactful structural change in Phase 2 because all subsequent tasks reference the new trait names and config types.

Per ADR-035 and research/phase2/interface-model.md:

• Interface → StreamInterface (the current trait becomes the stream-specific variant; persistent byte streams)
• InterfaceSession stays as-is (it's already stream-specific)
• Add MessageInterface trait: handle_request(&self, request: InterfaceRequest) -> Result<InterfaceResponse> (stateless request/response)
• Add InterfaceRequest and InterfaceResponse types that normalize calls across message interfaces
• Add HttpInterface stub (struct definition, no route implementations yet)
• Add DnsInterface stub (struct definition only)
• Restructure InterfaceConfig into StreamInterfaceConfig and MessageInterfaceConfig
• Restructure ListenerConfig from its current flat struct form to the ADR-035 enum with Stream, Http, and Dns variants
• Remove TransportKind::Dns — DNS is a MessageInterface, not a transport. This is a residual from Phase 1 that needs cleanup. All code referencing it must be removed: the ListenerConfig::dns() constructor, pairs.rs valid pairs table, TransportKindBase::Dns, and all related tests.
• Update TransportKind::WebTransport field from { host: String } to { server_name: Option<String> } per ADR-035 (tag-only variant, server_name is optional)

Why this must go first: Every other Phase 2 task imports and references these types. The rename and new traits must land before SshSession bridge, RawFraming implementation, or HTTP scaffold work begins. The integration plan section 2.3 explicitly states: "This task should be done early in Phase 2 because all subsequent tasks reference the new trait names."

Current state of the code (IMPORTANT — these differ from what the research docs assumed):

• Interface trait in crates/alknet-core/src/interface/mod.rs with accept() → Self::Session
• InterfaceSession trait in crates/alknet-core/src/interface/session.rs with recv() / send()
• InterfaceConfig enum with Ssh(SshInterfaceConfig) and RawFraming(RawFramingConfig) variants
• InterfaceKind enum with Ssh and RawFraming variants
• TransportKind has Tcp, Tls { server_name: Option<String> }, Iroh { endpoint_id: String }, Dns { domain: String }, and WebTransport { host: String }
• TransportKind::Dns exists in the current code — it must be removed. References exist in pairs.rs (TransportKindBase::Dns), serve.rs (ListenerConfig::dns() constructor, Display impl, validate logic), transport/mod.rs (Display impl, tests), and lib.rs re-exports.
• TransportKind::WebTransport exists but has { host: String } — must be changed to { server_name: Option<String> } per ADR-035.
• ListenerConfig is currently a flat struct (fields: transport_kind, interface_kind, listen_addr, tls_cert, tls_key, acme_domain, stealth, iroh_relay) with builder-pattern constructors (tcp(), tls(), iroh(), dns(), webtransport()) — NOT an enum. Must be restructured to the ADR-035 enum form.
• SshInterface implements Interface, SshSession implements InterfaceSession
• RawFramingInterface/RawFramingSession are stubs (Phase 1 left them)

Acceptance Criteria

• Interface trait renamed to StreamInterface throughout alknet-core (mod.rs, ssh.rs, raw_framing.rs, and all import sites including lib.rs)
• MessageInterface trait defined in crates/alknet-core/src/interface/mod.rs with handle_request(&self, request: InterfaceRequest) -> Result<InterfaceResponse>
• InterfaceRequest struct defined with operation_path, input, auth_token, metadata fields per interface-model.md
• InterfaceResponse struct defined with result, status, headers fields per interface-model.md
• HttpInterface stub struct defined (identity_provider, registry, env fields) — no route implementations
• DnsInterface stub struct defined (domain, identity_provider, registry, env fields) — no implementation
• InterfaceConfig restructured: StreamInterfaceConfig::Ssh and StreamInterfaceConfig::RawFraming replace current variants; MessageInterfaceConfig enum added with Http and Dns variants
• ListenerConfig restructured from flat struct to enum with Stream { transport: TransportKind, interface: StreamInterfaceKind }, Http { config: HttpListenerConfig }, and Dns { config: DnsListenerConfig } variants per ADR-035
• StreamInterfaceKind enum defined (corresponding to StreamInterface implementors: Ssh, RawFraming)
• MessageInterfaceKind enum defined (corresponding to MessageInterface implementors: Http, Dns)
• TransportKind::Dns removed from the enum and all references cleaned up: TransportKindBase::Dns in pairs.rs, ListenerConfig::dns() constructor, Display impls, validate logic, and all related tests
• TransportKind::WebTransport field changed from { host: String } to { server_name: Option<String> } and all references updated
• is_valid_pair() / TransportKindBase validation updated for StreamInterface pairs only (no DNS pairs)
• All existing tests pass after the changes (SshInterface and RawFramingInterface still compile and pass)
• New StreamInterface implementors still use InterfaceSession for type Session
• MessageInterface has at least one compilation test (e.g., a mock struct implements it)
• HttpInterface and DnsInterface stubs compile and exist in the type system
• lib.rs re-exports all new types (StreamInterface, MessageInterface, InterfaceRequest, InterfaceResponse, HttpInterface, DnsInterface, StreamInterfaceConfig, MessageInterfaceConfig, StreamInterfaceKind, MessageInterfaceKind, HttpListenerConfig, DnsListenerConfig)
• HttpListenerConfig struct defined with bind_addr: SocketAddr, tls: bool, stealth: bool
• DnsListenerConfig struct defined with bind_addr: SocketAddr, tls: bool
• Display implementations added for all new enums/structs
• #[non_exhaustive] on ListenerConfig, StreamInterfaceKind, MessageInterfaceKind, MessageInterfaceConfig
• Serde Serialize/Deserialize on all new config types
• Updated tests cover the new ListenerConfig enum form, the removed Dns transport, and the WebTransport field rename

References

• docs/architecture/decisions/035-streaminterface-messageinterface-split.md — ADR-035
• docs/research/phase2/interface-model.md — Full design rationale
• docs/research/integration-plan.md — Phase 2.3
• crates/alknet-core/src/interface/mod.rs — Current Interface trait
• crates/alknet-core/src/interface/session.rs — InterfaceSession, InterfaceEvent
• crates/alknet-core/src/interface/config.rs — Current InterfaceConfig
• crates/alknet-core/src/interface/pairs.rs — Valid transport-interface pairs (has TransportKindBase::Dns to remove)
• crates/alknet-core/src/transport/mod.rs — TransportKind enum (has Dns and WebTransport { host } to fix)
• crates/alknet-core/src/server/serve.rs — ListenerConfig flat struct (to restructure to enum)
• crates/alknet-core/src/lib.rs — Re-exports

Notes

This is the most mechanically invasive change in Phase 2 due to the rename and the ListenerConfig restructuring, but it's low-risk behaviorally. The Interface → StreamInterface rename is a find-and-replace operation. The new MessageInterface trait and stubs are purely additive. The ListenerConfig restructuring is the biggest change — it's currently a flat struct with builder-pattern constructors, and needs to become an enum with Stream, Http, and Dns variants per ADR-035. The Server::new() code and StaticConfig::from_serve_options() code that currently uses the struct form will need to be updated.

The TransportKind::Dns removal is cleanup from Phase 1 — it was incorrectly added as a transport variant when DNS is actually a MessageInterface. All references must be removed: the TransportKindBase::Dns in pairs.rs, the ListenerConfig::dns() constructor in serve.rs, the VALID_TRANSPORT_INTERFACE_PAIRS table entry, and the Display/test code. The DNS functionality will be represented by ListenerConfig::Dns { config: DnsListenerConfig } instead.

The TransportKind::WebTransport field change from { host: String } to { server_name: Option<String> } aligns with ADR-035. Since no code currently depends on the host field specifically (there's no WebTransport acceptor), this is a safe rename.

The integration plan section 2.3 notes: "Existing SshInterface and RawFramingInterface become StreamInterface implementations. No behavior change for stream-based interfaces."

Consider using #[non_exhaustive] on the new enums (MessageInterfaceConfig, ListenerConfig, StreamInterfaceKind, MessageInterfaceKind) so future variants (WebSocket, etc.) don't break downstream.

When restructuring ListenerConfig from struct to enum, the Server::new(), StaticConfig::from_serve_options(), and serve.rs accept loop code will need updates. The ServeOptions.listeners field type changes. The ListenerConfig::tcp(), tls(), iroh() constructors should become associated functions that produce the ListenerConfig::Stream variant. New constructors for Http and Dns variants will be added.

Summary

To be filled on completion