Services define schema-backed abilities.
The control plane issues short-lived capability tokens.
Cap'n Web carries RPC method calls over HTTP-batch, WebSocket, or Cloudflare bindings.
Schemas validate inputs and outputs, using the validation library you already use.
Published abilities can become OpenAPI or MCP tools from the control plane.
Request ids and structured JSON logs correlate plane and service calls out of the box.

Service authors define abilities. Hono stays the HTTP shell for middleware, discovery, and adapter routes.

The library is written against web-standard globals only (crypto.subtle, fetch/Request, TextEncoder, timers) and runs on Node 20+, Cloudflare Workers, Deno, and Bun. That claim is exercised in CI on every push: the full test suite runs on Node 20/22/24 and inside real workerd isolates (via @cloudflare/vitest-pool-workers), and a bundled smoke — HTTP-batch end to end, streaming over a session transport, token verification accepting and rejecting — runs on Deno and Bun.

Install

npm install service-plane hono @hono/capnweb capnweb

Ability schemas come from a validation library you choose; service-plane does not bundle or require any particular one. Add whichever you already use — anything implementing Standard Schema and its Standard JSON Schema companion:

npm install arktype     # or zod, or @vinejs/vine, or valibot + @valibot/to-json-schema

See Choosing A Validation Library for versions and the one wrapper Valibot needs. Code samples in this README and the docs use Zod so they stay concrete — that is an arbitrary choice, not a default.

Minimal Service

import { RpcTarget } from 'capnweb';
import * as z from 'zod';
import {
  ServicePlaneService,
  abilityMethod,
  defineAbility,
  defineCapabilities,
  jwksFromServiceBinding,
} from 'service-plane/service';

type Env = {
  ASANA_CONNECTIONS: DurableObjectNamespace;
  CONTROL_PLANE: Fetcher;
};

const capabilities = defineCapabilities({
  serviceId: 'asana',
  scopes: [{ id: 'asana.tasks.write', title: 'Create Asana tasks' }],
});

const asanaTasks = defineAbility({
  id: 'asana.tasks',
  title: 'Asana Tasks',
  exposure: 'published',
  access: 'plane',
  scopes: ['asana.tasks.write'],
  methods: {
    createTask: abilityMethod({
      input: z.object({
        connectionId: z.string(),
        name: z.string().min(1),
        projectId: z.string(),
      }),
      output: z.object({
        id: z.string(),
        url: z.string().url(),
      }),
      scopes: ['asana.tasks.write'],
      rest: { method: 'post', path: '/asana/tasks', summary: 'Create an Asana task' },
      mcp: { name: 'asana_create_task', description: 'Create a task in Asana' },
    }),
  },
  handler: ({ context, identity }) => new AsanaTasksHandler(context.env, identity),
});

class AsanaTasksHandler extends RpcTarget {
  constructor(
    private readonly env: Env,
    private readonly identity: { serviceId: string },
  ) {
    super();
  }

  async createTask(input: { connectionId: string; name: string; projectId: string }) {
    const id = this.env.ASANA_CONNECTIONS.idFromName(`${this.identity.serviceId}:${input.connectionId}`);
    const connection = this.env.ASANA_CONNECTIONS.get(id);
    return connection.createTask(input);
  }
}

export default new ServicePlaneService<{ Bindings: Env }>({
  id: 'asana',
  title: 'Asana Service',
  version: '0.2.0',
  auth: {
    issuer: 'control-plane',
    jwks: (c) => jwksFromServiceBinding(c.env.CONTROL_PLANE),
  },
  capabilities,
  abilities: [asanaTasks],
});

This service mounts:

GET /.well-known/service-plane/service.json
ALL /rpc/asana.tasks

Minimal Control Plane

import {
  ServicePlaneControlPlane,
  cloudflareServiceBinding,
  hmacServiceClientAuth,
} from 'service-plane/control-plane';

export default new ServicePlaneControlPlane({
  signingKeys: (env) => [{ kid: '2026-07', secret: env.STS_SIGNING_SECRET }],
  authenticateCaller: (c) =>
    hmacServiceClientAuth({
      clients: [{ clientId: 'workflow-runner', secret: c.env.WORKFLOW_RUNNER_SECRET }],
    })(c),
  services: (c) => [
    cloudflareServiceBinding({
      id: 'asana',
      binding: c.env.ASANA,
      grants: [{ caller: 'workflow-runner', scopes: ['asana.tasks.write'] }],
    }),
  ],
});

The control plane mounts:

POST /.well-known/service-plane/capability-token
GET  /.well-known/service-plane/jwks.json
GET  /openapi.json
POST /rpc/mcp                                    (MCP streamable HTTP)

The plane serves the OpenAPI document; to render it, mount a Hono UI extension (e.g. @hono/swagger-ui or @scalar/hono-api-reference) on plane.app pointed at /openapi.json.

For this compact local-development walkthrough, the service above leaves ingress disabled so the caller below can connect directly. Do not use this direct topology as the production boundary. Production services should enable ingress: {} and route ability calls through the control-plane broker; direct non-brokered tokens are then rejected with 403 before handler creation. See Service-Plane Ingress.

Minimal Local Caller

import {
  abilitySession,
  cloudflareServiceBindingRpc,
  controlPlaneHmacTokenRequester,
  type AbilityRpc,
} from 'service-plane/service';

declare const env: {
  ASANA: Fetcher;
  CONTROL_PLANE: Fetcher;
  WORKFLOW_RUNNER_SECRET: string;
};

const asana = await abilitySession<AbilityRpc<typeof asanaTasks>>({
  abilityId: 'asana.tasks',
  callerServiceId: 'workflow-runner',
  targetServiceId: 'asana',
  scopes: ['asana.tasks.write'],
  requestToken: controlPlaneHmacTokenRequester({
    clientId: 'workflow-runner',
    clientSecret: env.WORKFLOW_RUNNER_SECRET,
    controlPlaneUrl: 'https://control-plane.internal',
    fetch: env.CONTROL_PLANE,
  }),
  transport: cloudflareServiceBindingRpc(env.ASANA),
});

await asana.createTask({
  connectionId: 'conn_123',
  name: 'Follow up',
  projectId: 'proj_456',
});

Agent Skill

The repo ships an APM package with a service-plane skill that teaches coding agents the ability model, the security boundaries, and where to find deeper reference material. It is distributed through this Git repo by the APM CLI, independently of npm.

Install the APM CLI once (instructions), then install the skill into a consumer project:

apm install JUVOJustin/service-plane

Or pin it as a dependency so every teammate gets the same version. Minimal apm.yml in the consumer repo:

name: my-project
version: 1.0.0
dependencies:
  apm:
    - JUVOJustin/service-plane

apm install

Either way the skill deploys to your agent's native location (.claude/skills/ for Claude Code, .agents/skills/ for Copilot, Cursor, and others; commit apm.lock.yaml to keep installs reproducible). From there the agent activates it automatically whenever a task touches service-plane code — no prompting needed. The skill source lives in .apm/skills/service-plane/; its references are synced copies of docs/.