Prismix
Vercel — AI · · 1 min read

Use ACP-compatible harnesses with the AI SDK harness layer

#model-release #agents #developer-tool

Mirrored from Vercel — AI for archival readability. Support the source by reading on the original site.

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The AI SDK harness layer now supports any Agent Client Protocol (ACP)-compatible harness with HarnessAgent through the new @ai-sdk/harness-acp package.

Previously, every harness adapter wrapped one specific runtime (Claude Code, Codex, Pi, Deep Agents, OpenCode). @ai-sdk/harness-acp wraps the protocol instead. It is a meta adapter: rather than adapting a single harness, it lets you build an adapter for any harness that ships an ACP-compatible package.

Implement a harness by passing that package to createACP and configure basic harness mapping.

import { createACP } from '@ai-sdk/harness-acp';


export function createCodexACP() {
  return createACP({
    harnessId: 'codex-acp',
    source: {
      type: 'npm-simple',
      packageName: '@agentclientprotocol/codex-acp',
executable: 'codex-acp',
forwardEnv: ['CODEX_API_KEY', 'OPENAI_API_KEY'],
permissionModeMapping: {
'allow-reads': null,
'allow-edits': null,
'allow-all': { type: 'session-mode', modeId: 'agent-full-access' },
authentication: {
methodId: 'api-key',

Basic ACP harness example implementation for Codex on top of the ACP meta harness

Then pass it to HarnessAgent like any other harness:

import { HarnessAgent } from '@ai-sdk/harness/agent';
import { createCodexACP } from './codex-acp-harness';


const agent = new HarnessAgent({
  harness: createCodexACP(),

Basic example for using the above Codex ACP harness with HarnessAgent

ACP is an abstraction over coding harnesses, but the AI SDK harness layer stays deliberately decoupled from it. Not every harness supports ACP, and for some, ACP limits or changes how well they expose their internal behaviors, so a direct adapter can produce a tighter integration.

For Claude Code and Codex, prefer the direct @ai-sdk/harness-claude-code and @ai-sdk/harness-codex adapters over an ACP-based implementation; reach for @ai-sdk/harness-acp when a harness has no direct adapter but ships an ACP-compatible package.

Read the ACP harness documentation to get started.

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