ask-acp

A Ruby implementation of the Agent Client Protocol (ACP): JSON-RPC 2.0 over stdio, following the v0.11.3 protocol schema. It provides a client that drives an ACP-compliant coding agent as a subprocess, a server base class for making a Ruby agent speak ACP, and a replay client for deterministic testing.

gem "ask-acp"

require "ask-acp"

client = Ask::ACP::Client.new(command: ["codex", "acp"])
client.start
client.initialize!(client_name: "my-app", client_version: "0.1.0")

session = client.session_new(cwd: "/tmp")

# Stream prompt events as they arrive
client.session_prompt(session[:id], "Hello!") do |event|
  puts "#{event[:method]}: #{event[:params]}"
end

client.stop

class MyAgent < Ask::ACP::Server
  def handle_session_new(params)
    { session: { id: SecureRandom.uuid, status: "running" } }
  end
end

MyAgent.new.run

• Ask::ACP::Client - spawns an agent CLI subprocess with Open3 and speaks ACP over stdio. Methods: initialize!, authenticate, session_new, session_load, session_list, session_fork, session_resume, session_close, session_prompt (streams events via a block), session_cancel, session_set_config_option, session_set_mode, session_set_model, start, stop.
• Ask::ACP::Server - base class to subclass; implement handle_* methods and run with .run.
• Ask::ACP::ReplayClient - replays pre-recorded JSONL interactions from a fixture file. No subprocess; instant, deterministic responses.
• Ask::ACP::Protocol - message builders and constants: AGENT_METHODS, CLIENT_METHODS, PROMPT_EVENTS, STATUSES, PROTOCOL_VERSION.
• Ask::ACP::Error and Ask::ACP::TimeoutError - errors raised by the client.

The full ask-rb documentation lives at https://ask-rb.github.io/ask-docs. The guide — ACP Client & Server — is the narrative walkthrough: driving real agents, hosting your own, the session lifecycle, streamed events, and testing. The Gem Index covers ask-acp in depth.

record_acp (installed with the gem) spawns a real agent and records a session flow to a JSONL fixture for later replay:

record_acp opencode fixtures/opencode_session.jsonl

client = Ask::ACP::ReplayClient.new(fixture_path: "fixtures/opencode_session.jsonl")
client.start
client.initialize!(client_name: "my-app", client_version: "0.1.0")

bundle install
bundle exec ruby -Itest test/acp_test.rb

MIT