RFC: Cord

RFC: Cord

Status:     Draft
Author:     June Kim
Created:    2026-02-18
Version:    0.4.0

Abstract

This document specifies Cord, a coordination protocol for agent trees. Agents — implemented as Claude Code CLI processes — execute tasks, create subtasks, and return typed results. A SQLite database is the shared coordination state. Agents interact with it through MCP tools.

The protocol introduces four primitives (`goal`, `task`, `serial`, `ask`) and a single context-flow mechanism: `needs`. When creating a child task, the parent lists which completed nodes' results should be injected into the child's prompt. This replaces the earlier `spawn`/`fork` distinction with explicit context selection.

1. Motivation

Existing agent orchestration systems fall into two categories:

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No existing system provides:

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Cord addresses these gaps with a minimal set of primitives designed for coordinating LLM-based agents on a single machine.

2. Overview

2.1 System Architecture

┌─────────────────────────────────────────────┐
│              SQLite Database                 │
│     (coordination state, WAL mode)           │
└──────────────────┬──────────────────────────┘
                   │ read/write
                   ▼
┌─────────────────────────────────────────────┐
│                 Engine                       │
│  (scheduler, process manager, TUI)           │
└──────────────────┬──────────────────────────┘
                   │ launches
          ┌────────┴────────┐
          │  Claude Code    │
          │  CLI processes  │
          │  (one per node) │
          └────────┬────────┘
                   │ MCP (stdio)
          ┌────────┴────────┐
          │  MCP Servers    │
          │  (one per agent,│
          │   stdio transport│
          │   → SQLite)     │
          └─────────────────┘

2.2 Design Constraints

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