a2a-bridge

 

<h3 align="center"><b>The bridge between AI agents.</b></h3> Claude Code, Codex, OpenClaw, Hermes Agent, Gemini CLI, Zed, and VS Code agents can finally talk to each other — one daemon, star topology, every protocol translated. Install once, pick your agents, and they collaborate across A2A and ACP without copy-paste, context loss, or model switching.

<table> <tr><td><b>Any agent calls Claude Code</b></td><td>OpenClaw, Gemini CLI, Zed, VS Code, and Hermes Agent send prompts to a live Claude Code session through the bridge. Real reasoning, not echo — verified end-to-end across the public internet.</td></tr> <tr><td><b>Claude Code calls other agents</b></td><td>Delegate tasks to Codex today. OpenClaw and Hermes outbound adapters ship in v0.2 — the star topology goes fully bidirectional.</td></tr> <tr><td><b>Multi-protocol hub</b></td><td>A2A (HTTP + SSE), ACP (stdio JSON-RPC), MCP Channels — one adapter per agent, the daemon translates. Adding a new agent means writing one adapter; nothing else changes.</td></tr> <tr><td><b>Multi-session isolation</b></td><td>RoomRouter + SQLite TaskLog. Concurrent sessions don't cross-talk; task state survives restarts.</td></tr> <tr><td><b>First-run in 60 seconds</b></td><td><code>npm i -g a2a-bridge && a2a-bridge init && a2a-bridge claude</code> — bearer token minted, plugin installed, Claude Code listening.</td></tr> <tr><td><b>Cross-host ready</b></td><td>Set <code>A2A_BRIDGE_CONTROL_HOST=0.0.0.0</code> and your ACP clients connect from anywhere. Daemon on a server, agents on laptops.</td></tr> </table>

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Quick Start — Claude Code + OpenClaw in 5 minutes

Both sides install the same package. The difference is what you run after install.

Step 1 — On the Claude Code machine (the server that answers prompts):

curl -fsSL https://raw.githubusercontent.com/firstintent/a2a-bridge/main/scripts/install.sh | bash

The script checks prerequisites (bun, npm, claude), installs a2a-bridge globally, and runs a2a-bridge init. Then start:

a2a-bridge claude                   # launch Claude Code with bridge

Claude Code is now listening. Note your machine's IP — the client in Step 2 needs it to connect (localhost if both on the same box).

Step 2 — On the OpenClaw / Hermes Agent machine (the client that sends prompts):

Recommended — tell the agent:

Read https://raw.githubusercontent.com/firstintent/a2a-bridge/main/docs/join.md and follow it.
The Claude Code server is at <server-ip>:4512.

Replace <server-ip> with the IP from Step 1 (or skip that line if both sides are on the same machine). The agent installs a2a-bridge, sets A2A_BRIDGE_CONTROL_URL, registers itself, and smoke-tests the connection. Full text: docs/join.md

<details> <summary><b>Manual setup</b></summary>

npm i -g a2a-bridge                 # same package, same install

Add to acpx.config.agents (OpenClaw) or your agent's config:

{ "agents": { "a2a-bridge": { "command": "a2a-bridge", "args": ["acp"] } } }

</details>

Send a prompt through the agent — it reaches Claude Code through the bridge, Claude Code reasons about it, and the reply streams back.

Same machine? Both sides run on one box, no extra config.

Different machines? Two env vars:

# on the server (Claude Code side)
export A2A_BRIDGE_CONTROL_HOST=0.0.0.0

# on the client (OpenClaw / Hermes side)
export A2A_BRIDGE_CONTROL_URL=ws://<server-ip>:4512/ws

<details> <summary><b>Install from source</b></summary>

git clone https://github.com/firstintent/a2a-bridge.git
cd a2a-bridge
bun install && bun run build:plugin
npm pack && npm i -g ./a2a-bridge-*.tgz

</details>

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Connect other agents

The same bridge works for every A2A / ACP agent — just swap the client config:

| Agent | Protocol | Config | |-------|----------|--------| | OpenClaw | ACP | openclaw.json → add "a2a-bridge" to acp.allowedAgents + register plugins.entries.acpx.config.agents["a2a-bridge"].command = "a2a-bridge acp", then /acp spawn a2a-bridge | | OpenClaw (remote) | ACP | same + "command": "a2a-bridge acp --url ws://<ip>:4512/ws" | | OpenClaw (multi-CC) | ACP | one agents entry per target: "bridge-proj-a": { "command": "a2a-bridge acp --target claude:proj-a" } (see multi-target routing) | | Hermes Agent | ACP | Same pattern as OpenClaw | | Zed | ACP | settings.json → { "agent_servers": { "a2a-bridge": { "command": "a2a-bridge", "args": ["acp"] } } } | | VS Code | ACP | { "acp.agents": [{ "name": "a2a-bridge", "command": "a2a-bridge", "args": ["acp"] }] } | | Gemini CLI | A2A | ~/.gemini/settings.json → { "remoteAgents": [{ "agentCardUrl": "http://localhost:4520/...", "auth": { "token": "<TOKEN>" } }] } | | Codex | peer | a2a-bridge codex — Claude Code ↔ Codex bidirectional |

Headless server (tmux)

Run the bridge CC in background while your primary Claude Code session works on something else:

a2a-bridge daemon start
tmux new-session -d -s cc-bridge "a2a-bridge claude"
tmux send-keys -t cc-bridge Enter

Multi-workspace routing (v0.2)

One daemon can front multiple Claude Code sessions at once. Each session attaches under a kind:id TargetId (e.g. claude:proj-a,

claude:proj-b), and ACP / A2A callers pick which session they want:

# Terminal 1 — two Claude Code sessions, one daemon
A2A_BRIDGE_STATE_DIR=~/.config/a2a-bridge/proj-a a2a-bridge claude
A2A_BRIDGE_STATE_DIR=~/.config/a2a-bridge/proj-b a2a-bridge claude
# → attach as claude:proj-a and claude:proj-b respectively

# Terminal 3 — inspect
a2a-bridge daemon targets
# TARGET            ATTACHED  CLIENT  UPTIME
# claude:proj-a     yes       3       2m
# claude:proj-b     yes       5       1m

ACP callers route with --target:

a2a-bridge acp --target claude:proj-a -p "review this branch"

OpenClaw registers one acpx agent entry per target:

{ "plugins": { "entries": { "acpx": { "config": { "agents": {
  "bridge-proj-a": { "command": "a2a-bridge acp --target claude:proj-a" },
  "bridge-proj-b": { "command": "a2a-bridge acp --target claude:proj-b" }
}}}}}}

A2A HTTP callers route via contextId → TargetId config (A2A_BRIDGE_CONTEXT_ROUTES env var, see below).

A second CC attaching to an already-claimed TargetId is rejected with a descriptive error. Rerun with a2a-bridge claude --force to kick the old attach and take over — the previous session gets a CC-visible notification that it was replaced.

Full design + deployment shapes: docs/design/multi-target-routing.md. v0.2 ships with the multi-claude axis; codex multi-instance lands in v0.3.

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Architecture

Star topology — the daemon is the hub; every agent connects to it.

          Gemini CLI        OpenClaw        Zed        VS Code       Hermes Agent
              │                │             │            │               │
              │ A2A            │ ACP         │ ACP       │ ACP          │ ACP
              ▼                ▼             ▼            ▼               ▼
        ┌─────────────────────────────────────────────────────────────────────┐
        │                        a2a-bridge daemon                           │
        │                         (RoomRouter)                               │
        └──────────────┬──────────────────┬──────────────────┬───────────────┘
                       │                  │                  │
                       ▼                  ▼                  ▼
                  Claude Code          Codex           Hermes [v0.2]
                  (CC plugin)       (WS JSON-RPC)     (ACP adapter)
                    server             peer               peer

| Agent | Role | Status | |-------|------|--------| | Claude Code | server — receives prompts | v0.1 | | Codex | peer — CC delegates to it | v0.1 | | OpenClaw, Zed, VS Code, Hermes, Gemini CLI | client — calls CC | v0.1 | | OpenClaw, Hermes | peer — CC delegates to them | v0.2 |

Full protocol matrix + deployment shapes: docs/design/architecture.md

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Docs

| | | |---|---| | Architecture | Protocol matrix, adapter contract, deployment shapes | | Positioning | When multi-agent helps vs. hurts | | Roadmap | Phased plan, v0.2 backlog | | Cookbook | Verification, context-protection, parallel patterns with examples | | Rooms | Session isolation, RoomId, restart semantics | | Join Skill | Self-install skill — hand it to any AI | | Release Runbook | npm publish, marketplace, ACP registry |

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Troubleshooting

a2a-bridge doctor             # preflight checklist
a2a-bridge daemon logs        # recent daemon activity

Common fixes: see the env var reference below.

Environment Variables

| Variable | Default | Purpose | |----------|---------|---------| | A2A_BRIDGE_BEARER_TOKEN | from init | A2A HTTP auth | | A2A_BRIDGE_A2A_PORT | 4520 | A2A listener | | A2A_BRIDGE_CONTROL_PORT | 4512 | Daemon control plane | | A2A_BRIDGE_CONTROL_HOST | 127.0.0.1 | Control plane bind (0.0.0.0 for remote) | | A2A_BRIDGE_CONTROL_URL | auto | Full WS URL for ACP subprocess | | A2A_BRIDGE_ACP_ENSURE_DAEMON | unset | Opt-in: auto-start daemon in acp (off by default) | | A2A_BRIDGE_STATE_DIR | ~/.local/state/a2a-bridge | Config, logs, task DB (basename also seeds the CC TargetId) | | A2A_BRIDGE_WORKSPACE_ID | (derived) | Explicit override for this CC's id (wins over STATE_DIR basename) | | A2A_BRIDGE_FORCE_ATTACH | unset | When 1, a2a-bridge claude kicks an attached CC on the same TargetId (equivalent to --force) | | A2A_BRIDGE_CONTEXT_ROUTES | unset | JSON map {"ctx-id": "claude:workspace"} for A2A contextId → TargetId routing; unmapped contexts fall back to claude:default |

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License

MIT. See LICENSE and NOTICE.