Agent Context Protocol (ACP)

ACP is a standard JSON-RPC based protocol that enables seamless communication between code editors (clients) and AI coding agents (servers). It operates over standard input/output (stdio), allowing the agent to run as a subprocess of the editor.

Core Concepts

1. JSON-RPC Transport: Communication uses JSON-RPC 2.0 messages (requests, responses, notifications) delimited by newlines.
2. Sessions: Stateful conversation contexts.
3. Context: Rich context is passed to the agent, including:
   • User messages
   • File contents (resources)
   • Editor selections
   • Terminal output
4. Tools & Delegation: Agents can execute tools and delegate tasks to specialized sub-agents. The client handles tool execution requests and displays progress.

Implementation in PDFScribe

PDFScribe implements ACP to power its research capabilities using the local opencode binary.