Platform capabilities

A Harness contribution can add resources to the Agent runtime without importing Kernel managers. Register contributions before harness.start(); the Harness starts their effects in order and disposes them in reverse order.

import {
  Contribution,
  NextclawHarness,
  createTypedKey,
  eventKeys,
} from '@nextclaw/harness';

const customerLookupIngress = createTypedKey<{ id: string }>(
  'acme.customer.lookup',
);

class BusinessContribution extends Contribution {
  constructor() {
    super({ id: 'acme.business', version: '1.0.0' });
  }

  protected setup = (): void => {
    this.effect(() =>
      this.kernel.eventBus.on(eventKeys.ncpEvent, (event) => {
        observeAgentEvent(event);
      }),
    );

    this.effect(() =>
      this.kernel.ingress.addHandler(customerLookupIngress, ({ payload }) =>
        loadCustomer(String(payload?.id)),
      ),
    );

    this.effect(() =>
      this.kernel.tools.register({
        name: 'lookup_customer',
        parameters: { type: 'object', properties: { id: { type: 'string' } } },
        execute: async ({ id }) => loadCustomer(String(id)),
      }),
    );

    this.effect(() =>
      this.kernel.context.register({
        provide: async (request) => [await loadBusinessContext(request.agentId)],
      }),
    );
  };
}

const harness = new NextclawHarness();
harness.contributions.register(new BusinessContribution());
await harness.start();

Available namespaces

Namespace	What the host can do
kernel.eventBus	Observe or emit public Kernel events with eventKeys
kernel.ingress	Invoke standard ingressKeys or register an extension entry with a typed key
kernel.tools	Register an NcpTool for Agent runs
kernel.context	Add request-scoped context blocks
kernel.models	Register provider catalog plugins, list providers, and call chat or streaming chat
kernel.runtimes	Register an NCP runtime provider and the runtime entries Agents can select
kernel.mcp	Register a lifecycle-scoped MCP server, list servers and tools, and call a tool

kernel.eventBus and kernel.ingress are the actual instances owned by this Harness's Kernel, not a copied SDK event bridge or routing table. EventBus.on() and Ingress.addHandler() both return disposers, so this.effect() releases them with the contribution.

Model provider registration changes only this Harness-owned Kernel. MCP server registration is an in-memory overlay: it uses the normal MCP connection lifecycle but does not write the server into the user's config file.

Every registration returns a disposer. Return that disposer from this.effect(); async setup is supported, including kernel.mcp.registerServer(). Contributions do not override start() or dispose() and do not receive a context parameter.

skills, storage, sandboxes, channels, and apps are not public Harness namespaces yet.