Files
alknet/tasks/server/control-channel.md
glm-5.1 5c820a41e9 tasks: decompose Phase 0a ADR foundation and mark prior tasks completed
Add 10 new tasks under tasks/architecture/ for Phase 0a (ADR writing):
- 9 ADR tasks (026-034) with dependency-ordered structure
- 1 review checkpoint task before Phase 0b spec writing

ADR dependency graph (3 generations):
  Gen 1 (parallel): 026, 029, 030, 031, 032, 034
  Gen 2 (depends on 029): 027, 028
  Gen 3 (depends on 027+028): 033
  Gen 4: review checkpoint

Also mark all 34 prior implementation tasks as completed — they
were finished but still showing as pending in the taskgraph.
2026-06-07 08:55:33 +00:00

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2.3 KiB
Markdown

---
id: server/control-channel
name: Implement alknet-control reserved channel for pubsub event bus bridging (ADR-018)
status: completed
depends_on:
- server/handler
- auth/error-types
scope: narrow
risk: medium
impact: component
level: implementation
---
## Description
Implement the control channel routing per ADR-018. When the server receives a `channel_open_direct_tcpip` request for `alknet-control:0`:
1. The handler detects the reserved `alknet-` prefix destination
2. Instead of making a TCP connection, it bridges the SSH channel to an internal event bus handle
3. `EventEnvelope` JSON flows bidirectionally over the SSH channel
The entire `alknet-` prefix is reserved — no TCP connections should be attempted for `alknet-*` destinations. The control channel is optional; servers without pubsub configured should accept the channel and provide a configurable behavior (reject or provide a loopback pipe).
At this stage, implement the routing logic and a `ControlChannel` trait that consumers can implement. The actual pubsub bridge implementation would be in a separate crate or behind a feature flag.
## Acceptance Criteria
- [ ] `crates/alknet-core/src/server/control_channel.rs` exports `ControlChannelHandler` trait and routing logic
- [ ] `ALKNET_CONTROL_DESTINATION` constant defined as `"alknet-control"` (ADR-018)
- [ ] `ALKNET_PREFIX` constant defined as `"alknet-"` for namespace reservation
- [ ] `ControlChannelHandler` trait: `async fn handle_channel(stream: Box<dyn AsyncRead + AsyncWrite + Unpin + Send>)`
- [ ] Server handler detects `alknet-*` prefix and routes to `ControlChannelHandler` instead of TCP proxy
- [ ] If no `ControlChannelHandler` configured, reject the channel open request (SSH channel open failure)
- [ ] Non-reserved destinations continue through normal TCP proxy path
- [ ] Server constraint enforced: no TCP connections to `alknet-*` destinations
- [ ] Unit tests: reserved destination detected, non-reserved passes through, prefix matching works
## References
- docs/architecture/server.md — Channel Handling section (reserved destinations), Constraints section
- docs/architecture/decisions/018-control-channel-for-pubsub.md — control channel rationale
- docs/architecture/napi-and-pubsub.md — server-side control channel behavior
## Notes
> To be filled by implementation agent
## Summary
> To be filled on completion