examples

ARCP Rust examples

Thirteen single-purpose codebases, each named for the protocol primitive it demonstrates. Mirrors the Python tree at python-sdk/examples/.

Illustrative, not runnable. Each example imports the in-repo arcp crate as if it were a published arcp = "2". Setup boilerplate (transport URL, identity, auth) is elided with let client: Client = todo!();. LLM and framework calls live in tiny stub modules (agents.rs, steps.rs, synth.rs, ...) so the protocol code in main.rs is what you read.

The thirteen

Example	Demonstrates	Spec
subscriptions/	Three Observer clients on one session, three filters, three sinks.	§5, §13
leases/	Lease-gated shell agent. Read leases coarse, write leases scoped.	§15.4–§15.5
lease_revocation/	Per-table leases with lease.revoked / lease.extended mid-flight.	§15.5
permission_challenge/	Two-party challenge — generator asks, reviewer holds veto.	§15.4, §6.4
delegation/	agent.delegate fan-out + a JobMux over tokio::sync::mpsc to demux events by job_id.	§14, §6.4
handoff/	agent.handoff with transcript packed as an artifact, runtime fingerprint pinned.	§14, §16, §8.3
heartbeats/	Worker federation; heartbeat-loss reroute via idempotency_key.	§10.3, §6.4
capability_negotiation.rs	Capability-driven peer routing; standard cost.usd rollups.	§7, §17.3.1, §18.3
resumability/	Real crash and resume. std::process::exit(137) mid-flight; second invocation picks up at the next step.	§10, §19, §6.4
reasoning_streams/	kind: thought stream + a peer runtime that subscribes and delegates critiques back.	§11.4, §13, §14
extensions.rs	Custom arcpx.sdr.*.v1 extension namespace + unknown-message handling.	§21
cancellation.rs	Cooperative cancel (terminate) vs interrupt (pause and ask).	§10.4–§10.5
mcp/	ARCP runtime fronting an MCP server: tool.invoke → MCP call_tool.	§20

Conventions

• Rust 2021, formatted with cargo fmt, clippy-clean under cargo clippy --examples -- -D warnings.
• Each example is one main.rs (the protocol code) + 0–2 stub modules named for what they elide (agents.rs, steps.rs, cheap.rs, synth.rs, work.rs, channels.rs, sql.rs, upstream.rs).
• Single-file examples sit at examples/<name>.rs and run with cargo run --example <name>. Multi-file examples live at examples/<name>/main.rs with stub siblings; declared as [[example]] in the workspace Cargo.toml.
• let client: Client = todo!(); literally — transport, identity, auth blocks are setup noise, not the point. Each example's allow header permits the lints (clippy::todo, unused_variables, ...) that illustration-grade code would otherwise trip.
• Envelopes match RFC-0001 v2 exactly. Custom message types follow §21.1 arcpx.<domain>.<name>.v<n> naming.

What's where in the SDK

• arcp::ARCPClient<T: Transport> — handshake driver.
• arcp::Envelope, arcp::ErrorCode, arcp::error::ARCPError — wire primitives.
• arcp::messages::Capabilities — negotiated capability bag.
• arcp::transport::{paired, MemoryTransport, WebSocketTransport, StdioTransport} — connection-time scaffolding.
• arcp::store::eventlog — SQLite schema reused by subscriptions.

Reading order

For a brisk tour: subscriptions, leases, delegation, resumability (this one actually crashes and recovers), cancellation, extensions, mcp. These seven exercise the bulk of the protocol.

Runnable end-to-end paths

The examples above are illustrative. For runnable end-to-end coverage of the protocol against the in-process runtime + in-memory transport, see crates/arcp/tests/.