ARCP.FSharp 0.1.0

ARCP F# SDK

F# reference implementation of the Agent Runtime Control Protocol (ARCP) v1.0. A typed, single-binary control plane for agent runtimes that owns the session, job, stream, subscription, lease, and human-in-the-loop machinery so applications stay out of message-routing.

Status

v0.1.0 — reference implementation. Covers the core protocol surface (RFC §1–§19) end-to-end on the in-memory, stdio, and WebSocket transports. See CONFORMANCE.md for the per-section status table; v0.2 work (mTLS, OAuth2, multi-agent handoff, scheduled jobs, checkpoint resume, HTTP/2 + QUIC) is itemised there.

Architecture

graph LR
  C[Client]
  T[Transport<br/>memory · stdio · ws]
  R[Runtime]
  EL[EventLog<br/>SQLite]
  J[JobManager]
  S[StreamManager]
  L[LeaseManager]
  SUB[SubscriptionManager]
  A[ArtifactStore]

  C <-->|envelopes| T
  T <-->|envelopes| R
  R --> EL
  R --> J
  R --> S
  R --> L
  R --> SUB
  R --> A
  SUB --> EL

Every envelope flows through the runtime's send chokepoint: append to the event log, hand to the transport, fan out to matching observer subscriptions. The same fanout is what makes resume (RFC §19) and observer-mode (§13) work — they read from the same log.

Run a sample in 60 seconds

dotnet run --project samples/01.MinimalSession            # session handshake (RFC §9)
dotnet run --project samples/02.ToolInvokeWithProgress    # job + progress (§10)
dotnet run --project samples/03.HumanInputRequest         # human-in-the-loop (§14)
dotnet run --project samples/04.PermissionChallenge       # permissions + leases (§15)
dotnet run --project samples/05.ObserverSubscription      # subscriptions (§13)
dotnet run --project samples/06.RelayHumanInTheLoop       # multi-channel human relay (§12.3)

Each sample wires a Runtime and a Client over Memory.createPair () — no external services required.

Install the CLI

The arcp command is published as a .NET global tool:

dotnet pack -c Release --output ./artifacts
dotnet tool install --global --add-source ./artifacts ARCP.FSharp.Cli

Then:

arcp --version                                                              # SDK + protocol version
arcp serve --stdio                                                          # NDJSON stdio runtime
arcp serve --ws --port 7878                                                 # WebSocket runtime on /ws
arcp send --url ws://127.0.0.1:7878/ws --token any --tool echo --args '"hi"'
arcp tail --url ws://127.0.0.1:7878/ws --token any                          # tail every envelope
arcp replay --session 01K... --db /path/to/events.db                        # replay the event log

When --token is omitted, serve accepts any non-empty bearer token (developer mode); set ARCP_TOKEN=… to lock it down without putting the secret in argv.

RFC section → module map

F#-specific notes

• File order is architecture. The .fsproj <Compile Include="…" /> order is the dependency-first order of the SDK. A file may only reference types declared earlier; this catches layering mistakes at build time.
• task { … } over async { … }. All public async APIs return Task or Task<T> so consumers in C# or VB.NET get idiomatic types. The runtime/job/stream pumps are all task builders.
• Single-case DUs for ids. SessionId, JobId, LeaseId, etc. are newtypes — mixing them is a compile error. FSharp.SystemTextJson serialises them as their bare inner string.
• Result<_, ARCPError> is the return type for any code path that can produce a wire-level error. The runtime converts Error e from a tool handler into a job.failed envelope with the correct code; no exception escape required.

Next steps

• See PLAN.md for the full build plan and phase log.
• See CONFORMANCE.md for the RFC section coverage table.
• See CHANGELOG.md for release notes.