Epic: Agent Client Protocol (ACP) integration

[bug-ops]

Overview

Integrate the Agent Client Protocol into Zeph, enabling it to function as a coding agent inside any ACP-compatible IDE (Zed, JetBrains, Neovim, etc.).

ACP standardizes JSON-RPC 2.0 communication between editors and coding agents over stdio. The editor provides file system and terminal access; the agent provides LLM-powered reasoning and tool execution.

Motivation

• JetBrains, Zed, Neovim already support ACP — massive reach for Zeph
• Protocol reuses MCP types — Zeph already has zeph-mcp
• A2A integration proves the JSON-RPC + LoopbackChannel pattern works
• Positions Zeph as an IDE-embeddable coding agent, not just a standalone CLI/TUI/Telegram bot

Architecture

New feature-gated crate zeph-acp following established patterns:

zeph-acp/
├── Cargo.toml
└── src/
    ├── lib.rs          — public API re-exports
    ├── error.rs        — AcpError (thiserror)
    ├── transport.rs    — stdio JSON-RPC framing (newline-delimited)
    ├── server.rs       — AcpServer: message dispatch, session lifecycle
    ├── session.rs      — session state, history, config options
    ├── types.rs        — ACP wire types (or re-export from agent-client-protocol crate)
    ├── tools.rs        — AcpToolExecutor: proxy tool calls through IDE
    ├── fs.rs           — IDE-proxied file operations (fs/read_text_file, fs/write_text_file)
    └── terminal.rs     — IDE-proxied terminal (terminal/create, terminal/output, etc.)

Integration via LoopbackChannel (same pattern as A2A), feature-gated acp flag, launched with zeph --acp.

Scope

See child issues for detailed breakdown.

References

• ACP Specification
• ACP Schema
• Rust SDK
• GitHub repo