ACP adapter for Codex, Claude Code, and Pi

acp-adapter is a Go ACP (Agent Client Protocol) adapter that lets ACP clients drive multiple downstream agent backends over the ACP protocol:

Backend	Downstream official channel	Standalone flag	Library package	Notes
Codex	codex app-server over stdio JSON-RPC	--adapter codex	pkg/codexacp	Most complete backend, including MCP routing.
Claude Code	claude -p ... --output-format stream-json	--adapter claude	pkg/claudeacp	Machine-readable Claude CLI bridge.
Pi	pi --mode rpc over official RPC JSON lines	--adapter pi	pkg/piacp	Official Pi RPC bridge with session load/list and ACP permission gate.

Usage Modes

This component supports two integration models:

Mode	Use Case	Entry Point
Standalone (process)	Configure a binary in Zed or other ACP clients	cmd/acp
Library (embedded)	Host ACP runtime inside your Go service	pkg/codexacp, pkg/claudeacp, pkg/piacp

Standalone Usage

Installation

curl -sSL https://raw.githubusercontent.com/beyond5959/acp-adapter/master/install.sh | sh

Quick Start

# Codex backend (default)
acp-adapter --adapter codex

# Claude backend
acp-adapter --adapter claude

# Pi backend
acp-adapter --adapter pi --pi-provider openai-codex --pi-model gpt-5.4-mini

Pi mode expects a working pi CLI on PATH or --pi-bin. Useful Pi-specific flags:

• --pi-provider / PI_PROVIDER
• --pi-model / PI_MODEL
• --pi-session-dir / PI_SESSION_DIR
• --pi-disable-gate / PI_DISABLE_GATE

ACP Client Config

{
  "agent_servers": {
    "acp-adapter": {
      "command": "/usr/local/bin/acp-adapter",
      "args": ["--adapter", "pi", "--pi-provider", "openai-codex", "--pi-model", "gpt-5.4-mini"]
    }
  }
}

Swap pi for codex or claude if you want a different backend.

Library Usage

The three runtime packages expose aligned entry points: DefaultRuntimeConfig, RunStdio, and NewEmbeddedRuntime.

import "github.com/beyond5959/acp-adapter/pkg/piacp"

// Stdio mode
cfg := piacp.DefaultRuntimeConfig()
cfg.DefaultProvider = "openai-codex"
cfg.DefaultModel = "gpt-5.4-mini"
err := piacp.RunStdio(ctx, cfg, os.Stdin, os.Stdout, os.Stderr)

// Embedded mode
rt := piacp.NewEmbeddedRuntime(cfg)
rt.Start(ctx)
defer rt.Close()
resp, err := rt.ClientRequest(ctx, msg)

Use pkg/codexacp for Codex and pkg/claudeacp for Claude; the runtime shape is the same, while config fields stay backend-specific.

Codex ACP Support

This section is intentionally based on the current code in internal/acp/server.go and internal/acp/types.go.