OACP — Open Agent Coordination Protocol

Try the quickstart → — send your first message to an AI agent in 5 minutes.

Coordinate agents without the chaos.

A file-based protocol for multi-agent engineering workflows. OACP defines the message formats, review processes, and safety rules that let AI agents on different runtimes collaborate through a shared filesystem. Not a framework or SDK — just conventions, YAML schemas, and scripts that any runtime can implement.

Quick Start

pip install oacp-cli
oacp init my-project --agents alice,bob
oacp send my-project --from alice --to bob --type task_request \
  --subject "Implement feature X" --body "Details here..."

When running inside a configured agent runtime, --from can be omitted — OACP infers the sender from OACP_AGENT, AGENT_NAME, or the agent card. See QUICKSTART.md for a full walkthrough.

What you get

• Inbox/outbox messaging — async YAML messages with threading, broadcast, and expiry
• Structured review loop — severity-graded findings, quality gates, multi-round review
• Inbox CLI — oacp inbox lists pending messages across agents with table or --json output
• Watch CLI — oacp watch emits inbox delta events for Claude Monitor or shell loops
• Durable shared memory — project facts, decisions, and known debt with active/archive split
• Agent safety defaults — baseline rules for git, credentials, and scope discipline
• Runtime-agnostic — works with any runtime that reads/writes files

Try It Now

After installing, run oacp doctor to verify your environment is wired up:

oacp doctor

Why OACP?

When multiple AI agents work on the same codebase, they need a way to:

• Communicate — send task requests, review feedback, and handoffs without shared memory
• Review each other's work — structured review loops with quality gates and severity-based findings
• Stay in sync — durable memory files that persist decisions across sessions and runtimes
• Stay safe — baseline safety rules for git operations, credential scoping, and scope discipline

OACP solves this with a filesystem-based protocol that requires no server, no database, and no vendor lock-in. Agents read and write YAML files in a shared directory — that's it.

Where OACP Fits

Four protocols are shaping multi-agent development. They solve different problems at different layers:

┌─────────────────────────────────────────────┐
│  A2A — Agent discovery & remote messaging   │  internet-scale
├─────────────────────────────────────────────┤
│  OACP — Async workflow messaging            │  local filesystem
├─────────────────────────────────────────────┤
│  ACP — Client ↔ agent sessions              │  IDE / editor
├─────────────────────────────────────────────┤
│  MCP — Agent-to-tool integration            │  tool access
└─────────────────────────────────────────────┘

MCP gives agents access to tools and data sources — databases, APIs, file systems. It defines how an agent calls a tool.

ACP (Agent Client Protocol, by Zed Industries) connects clients to coding agents. JSON-RPC, primarily over stdio today. Adopted by Zed, JetBrains, Neovim, and 28+ agents in its registry.

A2A lets agents discover and communicate with each other across the internet. HTTP-based, enterprise-grade, backed by 150+ organizations under the Linux Foundation.

OACP is the async messaging layer for multi-agent workflows — typed workflow messages (task dispatch, code review, handoff, brainstorm) over persistent transport that survives crashes. Zero infrastructure required.

How they compare

	MCP	ACP	A2A	OACP
Solves	Tool access	Client ↔ agent sessions	Agent discovery + networking	Async workflow coordination
Transport	JSON-RPC (stdio/HTTP)	JSON-RPC (stdio; HTTP draft)	HTTP/HTTPS	Filesystem (YAML)
Best for	Connecting agents to APIs, DBs, files	IDE ↔ coding agent interaction	Cross-org, internet-routable agents	Local teams, dev machines, CI
Infrastructure	MCP server per tool	ACP-capable client + agent	TLS, auth, HTTP endpoints	A shared directory
Offline support	N/A (synchronous)	N/A (session-based)	Agent must be reachable	Native — messages wait in inbox
Setup	Install MCP server	Use ACP-capable client + agent	Deploy servers + networking	oacp init my-project

These protocols are complementary, not competing. An agent can use MCP to access tools, speak ACP for IDE integration, and check OACP inboxes for multi-agent coordination — different layers, no conflict.

A2A connects agents across the internet. OACP coordinates agents on your machine. A gateway between OACP inboxes and A2A endpoints is a natural bridge — and A2A's own community is exploring inbox patterns that validate this design.

Install

uv tool install oacp-cli

pipx install oacp-cli

uvx --from oacp-cli oacp doctor

From source

git clone https://github.com/kiloloop/oacp.git
cd oacp
uv tool install .

Commands

Command	Description
oacp init	Create a project workspace under $OACP_HOME/projects/
oacp add-agent	Add an agent to an existing project workspace
oacp setup	Generate runtime-specific config files (Claude, Codex, etc.)
oacp send	Send a protocol-compliant inbox message (--from auto-inferred)
oacp inbox	List pending messages across agents (table or --json)
oacp watch	Emit inbox delta events for one agent across selected projects
oacp memory	Archive or restore project memory files
oacp agent	Manage global agent profiles (init, show, list)
oacp org-memory	Initialize org-level memory at $OACP_HOME/org-memory/
oacp write-event	Write an event to org-memory/events/
oacp doctor	Check environment and workspace health
oacp validate	Validate an inbox/outbox YAML message
oacp --version	Print the installed version

Key flags

oacp send: --in-reply-to, --expires, --body-file, --channel, --dry-run, --json, --quiet

oacp watch: --agent, repeatable --project, --all-projects, --json

oacp doctor: --fix (auto-fix safe issues), --json, -o/--output

oacp memory: oacp memory archive <project> <file>, oacp memory restore <project> <file>

If OACP_HOME is unset, workspace commands default to ~/oacp.

Key Concepts

Concept	Description
Inbox/Outbox	Async messaging between agents via YAML files in agents/<name>/inbox/
Review Loop	Structured code review: review_request → review_feedback → review_addressed → review_lgtm
Quality Gate	Merge-readiness criteria: no unresolved P0/P1 findings, deferred nits tracked
Durable Memory	Shared memory/ directory with an active working set plus memory/archive/ for historical memory
Dispatch States	Task lifecycle: received → accepted → working → pr_opened → in_review → done
Safety Defaults	Baseline rules all agents follow: no force push, no secrets in commits, stage hygiene

Project Structure

oacp/
├── docs/
│   ├── protocol/       # Canonical protocol specifications
│   └── guides/         # Setup, adoption, versioning
├── scripts/            # Kernel scripts (Python + shell)
├── templates/          # Packet, role, and guardrail templates
├── tests/              # Test suite
├── Makefile            # Task runner (make help for all targets)
└── SPEC.md             # Full protocol specification

Related

• agent-estimate — Estimate how long agent tasks take. Pairs with OACP dispatch for task sizing.

Prerequisites

• Python 3.9+
• Bash 3.2+ (macOS default is fine)
• gh CLI (optional, for GitHub operations)

Protocol Specification

The full protocol is documented in SPEC.md, covering:

1. Inbox/Outbox Messaging — message format, types, lifecycle, threading, broadcast
2. Dispatch State Machine — task lifecycle from delivery to completion
3. Review Loop — packet-based and inbox-based review with quality gates
4. Cross-Runtime Sync — durable memory, handoff context, session init
5. Safety Defaults — git safety, staging hygiene, credential scoping

Individual protocol specs live in docs/protocol/.

Workspace Layout

oacp init creates a project workspace with this structure:

$OACP_HOME/projects/<project>/
├── agents/
│   ├── <agent-a>/
│   │   ├── inbox/           # Other agents write here
│   │   ├── outbox/          # Sent messages (copies)
│   │   └── dead_letter/     # Undeliverable messages
│   └── <agent-b>/
│       └── ...
├── memory/                  # Shared durable memory
│   ├── project_facts.md
│   ├── decision_log.md
│   ├── open_threads.md
│   ├── known_debt.md
│   └── archive/
├── artifacts/               # Build/research artifacts
├── checkpoints/             # Progress checkpoints
├── logs/                    # Agent session logs
├── merges/                  # Merge decision records
├── packets/                 # Review/findings artifacts
└── workspace.json           # Project metadata

Optionally, oacp org-memory init creates org-level shared memory:

$OACP_HOME/org-memory/
├── recent.md                # Always-loaded rolling summary
├── decisions.md             # Org-wide decisions
├── rules.md                 # Standing conventions
└── events/                  # Timestamped event entries

Development

make test
make preflight

Documentation

• SPEC.md — Full protocol specification
• examples/quickstart/ — Hands-on tutorial: send a message to an AI agent
• QUICKSTART.md — CLI reference walkthrough
• docs/guides/doctor.md — Doctor guide: checks, sample output, common fixes
• docs/guides/setup.md — Detailed setup guide
• docs/guides/adoption.md — Adoption guide (minimum → full)
• docs/protocol/ — Individual protocol specs
• CONTRIBUTING.md — How to contribute

Contributing

We welcome contributions! See CONTRIBUTING.md for guidelines.

License

Apache 2.0 — see LICENSE for details.