ARCP Java SDK

Java SDK for the Agent Runtime Control Protocol (ARCP). Targets JDK 21 LTS; tested on 21. Depends on Jackson and SLF4J only at the api level — no logging binding shipped.

Install

Gradle (Kotlin DSL)

dependencies {
    implementation("dev.arcp:arcp:1.0.0")            // umbrella
    // or, granular:
    implementation("dev.arcp:arcp-client:1.0.0")     // client only
    implementation("dev.arcp:arcp-runtime:1.0.0")    // runtime only
    implementation("dev.arcp:arcp-runtime-jetty:1.0.0") // WebSocket server
    implementation("dev.arcp:arcp-otel:1.0.0")       // OpenTelemetry tracing
}

Maven

<dependency>
  <groupId>dev.arcp</groupId>
  <artifactId>arcp</artifactId>
  <version>1.0.0</version>
</dependency>

Quickstart

import dev.arcp.client.ArcpClient;
import dev.arcp.client.JobHandle;
import dev.arcp.core.transport.MemoryTransport;
import dev.arcp.runtime.ArcpRuntime;
import dev.arcp.runtime.agent.JobOutcome;

import com.fasterxml.jackson.databind.node.JsonNodeFactory;

class Quickstart {
    public static void main(String[] args) throws Exception {
        MemoryTransport[] pair = MemoryTransport.pair();
        ArcpRuntime runtime = ArcpRuntime.builder()
            .agent("echo", "1.0.0",
                (input, ctx) -> JobOutcome.Success.inline(input.payload()))
            .build();
        runtime.accept(pair[0]);

        try (ArcpClient client = ArcpClient.builder(pair[1]).build()) {
            client.connect(java.time.Duration.ofSeconds(5));
            JobHandle handle = client.submit(ArcpClient.jobSubmit(
                "echo@1.0.0", JsonNodeFactory.instance.objectNode().put("hi", 1)));
            System.out.println(handle.result().get().result());
        }
        runtime.close();
    }
}

For a WebSocket-backed runtime, swap MemoryTransport for dev.arcp.runtime.jetty.ArcpJettyServer on the runtime side and dev.arcp.client.WebSocketTransport.connect(uri) on the client side. For a child-process agent, both peers wrap their stdin / stdout in dev.arcp.core.transport.StdioTransport (§4.2 newline-delimited JSON).

Packaging

Artifact	What's in it	Depends on
arcp-core	Wire types, errors, capability, ids, lease, transport SPI	none
arcp-client	ArcpClient, JobHandle, ResultStream, JDK WebSocket transport	arcp-core
arcp-runtime	ArcpRuntime, session FSM, job FSM, lease enforcement, budget counters	arcp-core
arcp	Umbrella; re-exports client + runtime	arcp-client, arcp-runtime
arcp-runtime-jetty	Embedded Jetty 12 WebSocket server transport	arcp-runtime
arcp-middleware-spring-boot	Spring Boot 3.x auto-config + WebSocket handler	arcp-runtime
arcp-middleware-jakarta	Plain Jakarta WebSocket adapter (ServerEndpointConfig)	arcp-runtime
arcp-middleware-vertx	Vert.x 5 WebSocket handler	arcp-runtime
arcp-otel	OpenTelemetry adapter (transport-wrapping Tracer)	arcp-core, opentelemetry-api
arcp-tck	Reusable JUnit 5 @TestFactory conformance suite	arcp-client, arcp-runtime

Layout

java-sdk/
├── settings.gradle.kts
├── build.gradle.kts
├── gradle/libs.versions.toml
├── arcp-core/
├── arcp-client/
├── arcp-runtime/
├── arcp/                      # umbrella
├── arcp-runtime-jetty/
├── arcp-otel/
├── arcp-middleware-jakarta/
├── arcp-middleware-spring-boot/
├── arcp-middleware-vertx/
├── arcp-tck/
├── docs/
│   ├── 00-overview.md
│   ├── 01-quickstart.md
│   ├── 02-concepts.md
│   ├── 03-features/           # heartbeats, ack, list-jobs, subscribe, progress,
│   │                          # result-chunk, lease-expires-at, cost-budget,
│   │                          # agent-versions
│   ├── 05-reference/          # api-overview, error-taxonomy, wire-format
│   └── diagrams/              # 6 Graphviz diagrams (light + dark SVGs)
└── examples/
    ├── submit-and-stream/
    ├── cancel/
    ├── heartbeat/
    ├── cost-budget/
    ├── result-chunk/
    ├── agent-versions/
    ├── list-jobs/
    ├── lease-expires-at/
    ├── idempotent-retry/
    └── custom-auth/

Build

export JAVA_HOME=$(/usr/libexec/java_home -v 21)
./gradlew build               # compile + test all modules
./gradlew :examples:submit-and-stream:run
./gradlew :arcp-runtime-jetty:test

Features

• §5.1 envelope with arcp: "1" and FAIL_ON_UNKNOWN_PROPERTIES=false
• §6.1 bearer auth via BearerVerifier SPI; acceptAny and staticToken helpers
• §6.2 capability intersection with rich agents shape (name + versions + default)
• §6.3 resume buffer (in-memory ring) and rotating resume_token
• §6.4 heartbeats: scheduler-driven ping; client and runtime treat two missed intervals as HEARTBEAT_LOST
• §6.5 session.ack with auto-emit rate limit on the client side
• §6.6 session.list_jobs scoped to the session's principal
• §7.1 job.submit with lease_request, lease_constraints, idempotency_key
• §7.2 idempotency: identical (principal, key, payload) reuses the prior job_id; conflicting payload yields DUPLICATE_KEY
• §7.4 cooperative cancellation via JobContext.cancelled() + Thread.interrupt
• §7.5 agent versioning: name@version grammar; bare names resolve to advertised default; unknown versions surface AGENT_VERSION_NOT_AVAILABLE
• §7.6 subscribe / unsubscribe with optional history replay; subscribers do not carry cancel authority
• §8.2 ten event kinds via sealed EventBody, including progress (current ≥ 0)
• §8.4 result_chunk reassembly via ResultStream (in-memory or OutputStream sink)
• §9 lease grammar + subset check (Lease.contains); LeaseGuard enforces glob patterns with * and ** semantics
• §9.5 lease expiration: strict UTC-Z parsing; scheduled watchdog terminates jobs whose lease expires while running
• §9.6 cost.budget via per-currency AtomicReference<BigDecimal> counters with USE_BIG_DECIMAL_FOR_FLOATS on the wire mapper
• §11 OpenTelemetry trace propagation via ArcpOtel.withTracing(transport, tracer); arcp.session_id / arcp.job_id / arcp.trace_id attributes on every span
• §12 fifteen-code error taxonomy with sealed ArcpException / RetryableArcpException / NonRetryableArcpException split

Concurrency

Virtual threads (JEP 444, stable in JDK 21) drive every per-job worker and every transport publisher. StructuredTaskScope is intentionally not used in published bytecode: it's preview in JDK 21 and finalized in JDK 25 with a different shape, and the SDK targets --release 21.

A single ScheduledExecutorService per runtime drives heartbeat ticks and lease expiry watchdogs; client-side, a similar scheduler emits session.ack and watches the inbound idle timer.

Conformance

See CONFORMANCE.md for the spec §-keyed table with file:line references. Tests at a glance:

• arcp-core:test — envelope round-trip, unknown-field tolerance, capability intersection, feature decode
• arcp-runtime:test — agent version resolution, budget counters, lease guard, expiry, subset checks
• arcp-client:test — smoke round-trip, idempotency reuse + conflict, subscribe with history replay, result-chunk reassembly
• arcp-otel:test — outbound + inbound spans through InMemorySpanExporter
• arcp-runtime-jetty:test — end-to-end client + runtime over loopback WebSocket
• arcp-middleware-spring-boot:test — Spring Boot 3.x autoconfig + WebSocket handler driven from a @SpringBootTest with an embedded Tomcat
• arcp-middleware-jakarta:test — Jakarta WebSocket ServerEndpointConfig registered against an embedded Jetty container
• arcp-middleware-vertx:test — Vert.x 5 HttpServer.webSocketHandler driven from a Vertx.vertx() test fixture
• arcp-tck:test — seven dynamic conformance tests via JUnit @TestFactory, reusable by downstream JVM implementations

Diagrams under docs/diagrams/: module graph, session lifecycle, job lifecycle, capability negotiation, heartbeat + ack, result-chunk reassembly. Light + dark variants render via make -C docs/diagrams.

Publishing

Maven Central credentials and PGP signing are wired in the root build.gradle.kts. Set the following Gradle properties (in ~/.gradle/gradle.properties or as ORG_GRADLE_PROJECT_* env vars):

ossrhUsername=...
ossrhPassword=...
signingKey=...        # PGP private key, in-memory format
signingPassword=...

Snapshot vs release routing is automatic from the version qualifier; signing is required only when the PGP credentials are present (local builds skip it silently). Publish a SNAPSHOT to local Maven with:

./gradlew :arcp-core:publishToMavenLocal

Mutation testing

PIT is wired on arcp-core and arcp-runtime as an opt-in Gradle task:

./gradlew :arcp-core:pitest
./gradlew :arcp-runtime:pitest

Reports land under each module's build/reports/pitest/. The mutation threshold is set to 0 so the run never fails the build; treat the HTML report as a code-review signal, not a gate.

License

Apache-2.0.