Bridge

A bridge library and application between Agent Client Protocol (ACP) agents and clients.

aptove-bridge can be used in two ways:

• Standalone binary — run bridge as a separate process that spawns your ACP agent over stdio and exposes it over WebSocket to mobile or desktop clients.
• Embedded library — add aptove-bridge as a Rust dependency and run the bridge server in-process alongside your agent, with no subprocess or stdio pipe required.

The Aptove project is the reference implementation of the embedded library usage — aptove run starts both the ACP agent and bridge server in a single process.

Transport Modes

| Mode | Use Case | Documentation | |------|----------|---------------| | Local | Same Wi-Fi network, secure pairing with QR code | docs/transport/local.md | | Cloudflare | Remote access via Cloudflare Zero Trust (internet-accessible) | docs/transport/cloudflare.md | | Tailscale Serve | Private overlay network via MagicDNS + HTTPS | docs/transport/tailscale.md | | Tailscale IP | Direct Tailscale IP with self-signed TLS | docs/transport/tailscale.md |

One transport is active at a time. When multiple are enabled in common.toml, the bridge prompts you to select one at startup.

Features

• 📱 QR Code Pairing: Secure one-time code pairing via QR scan
• 🔒 TLS + Certificate Pinning: Self-signed certificates with fingerprint validation
• ⚡ WebSocket Streaming: Real-time bidirectional communication
• 🌐 Multi-Transport: Local, Cloudflare, Tailscale — configure and switch between them
• 🔑 Stable Agent Identity: agent_id UUID persisted in common.toml for multi-transport dedup on mobile
• 🦀 Embeddable: Use as a library with BridgeServer for in-process deployment

Using as a Library

Add to your Cargo.toml:

[dependencies]
aptove-bridge = "0.1"

Minimal Example

use aptove_bridge::{BridgeServer, BridgeServeConfig};

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    // Build from defaults — reads transport selection from common.toml
    // in ~/Library/Application Support/Aptove (macOS) or ~/.config/Aptove (Linux).
    // Prompts the user to select a transport if multiple are enabled.
    let mut server = BridgeServer::build(&BridgeServeConfig::default())?;

    // Display a pairing QR code so a client can connect
    server.show_qr()?;

    // Take the in-process transport — wire it to your agent message loop
    let mut transport = server.take_transport();

    // Run your agent loop and bridge listener concurrently
    tokio::select! {
        _ = my_agent_loop(&mut transport) => {}
        res = server.start() => { res?; }
    }

    Ok(())
}

take_transport() returns an InProcessTransport that implements the same Transport trait as StdioTransport — your agent message loop works identically whether running standalone or embedded.

BridgeServeConfig

| Field | Default | Description | |-------|---------|-------------| | port | 8080 | WebSocket listen port (overridden by common.toml per-transport config) | | bind_addr | "0.0.0.0" | Bind address | | tls | true | Enable TLS (self-signed cert auto-generated) | | auth_token | None | Bearer token required for connections (auto-loaded from common.toml) | | keep_alive | false | Enable keep-alive agent pool | | config_dir | platform default | Directory for common.toml, TLS certs, and credentials |

Load from disk (reads bridge.toml and common.toml, generates agent_id if absent):

let config = BridgeServeConfig::load()?;

Reference Implementation: Aptove

The Aptove project (aptove run) is the full reference implementation. Key patterns it uses:

• BridgeServer::build_with_trigger_store() — wires in a TriggerStore for webhook support
• server.show_qr() — uses the pairing handshake so clients deduplicate agents by agentId
• server.take_transport() + run_message_loop() — connects the in-process transport to the ACP dispatch loop
• tokio::select! on agent_loop and server.start() — clean shutdown when either side exits

Standalone Binary

Quick Start

# Build
cargo build --release

# Start with local transport (default — no config needed)
./target/release/bridge run \
  --agent-command "gemini --experimental-acp" \
  --qr

Scan the QR code with the Aptove mobile app to connect.

Configuration — common.toml

All transport settings live in common.toml. The file is created automatically with local transport enabled on first run.

Default location:

| Runtime | macOS | Linux | |---------|-------|-------| | aptove run (embedded) | ~/Library/Application Support/Aptove/common.toml | ~/.config/Aptove/common.toml | | bridge (standalone) | ~/Library/Application Support/com.aptove.bridge/common.toml | ~/.config/bridge/common.toml |

When using aptove run, this config is shared across all workspaces.

Override with --config-dir:

bridge --config-dir ./my-config run --agent-command "gemini --experimental-acp"

Example common.toml

agent_id   = "550e8400-e29b-41d4-a716-446655440000"  # auto-generated UUID
auth_token = "base64urltoken"                         # auto-generated

[transports.local]
enabled = true
port    = 8765
tls     = true

[transports.cloudflare]
enabled       = true
hostname      = "https://agent.example.com"
tunnel_id     = "abc123"
tunnel_secret = "..."
account_id    = "..."
client_id     = "client.access"
client_secret = "xxxxx"

[transports.tailscale-serve]
enabled = true

[transports.tailscale-ip]
enabled = true
port    = 8765
tls     = true

Enable only the transports you need. agent_id and auth_token are generated automatically on first run and stay stable across restarts.

Commands

run — Start the bridge

bridge run --agent-command "<your-agent-command>"

| Flag | Description | Default | |------|-------------|---------| | --agent-command <CMD> | Command to spawn the ACP agent | Required | | --bind <ADDR> | Address to bind the listener | 0.0.0.0 | | --qr | Display QR code for pairing at startup | Off | | --verbose | Enable info-level logging | Off (warn only) |

Transport selection, port, TLS, and auth token are all read from common.toml.

show-qr — Show QR code for a second device

bridge show-qr

Displays the connection QR code for the currently active transport. The bridge must already be running. Use this to pair an additional device without restarting.

To show the QR at initial startup, pass --qr to bridge run instead:

bridge run --agent-command "aptove stdio" --qr

setup — Provision Cloudflare infrastructure

bridge setup \
  --api-token  "your-api-token" \
  --account-id "your-account-id" \
  --domain     "example.com" \
  --subdomain  "agent"

Creates the Cloudflare tunnel, DNS record, Access Application, and Service Token. Saves credentials to common.toml under [transports.cloudflare]. Only needed once.

| Flag | Description | Default | |------|-------------|---------| | --api-token <TOKEN> | Cloudflare API token | Required | | --account-id <ID> | Cloudflare account ID | Required | | --domain <DOMAIN> | Domain managed by Cloudflare | Required | | --subdomain <SUB> | Subdomain for the bridge endpoint | agent | | --tunnel-name <NAME> | Name for the Cloudflare tunnel | aptove-tunnel |

status — Check configuration

bridge status

Prints the active common.toml path, agent_id, enabled transports, and Tailscale availability.

Architecture

Standalone

┌─────────────┐                    ┌───────────────────────┐        ┌──────────────┐
│  Client App │◄──────────────────►│  bridge binary        │◄──────►│  ACP Agent   │
│ (iOS/Android│  WebSocket (TLS)   │  (transport listener) │  stdio │  (your cmd)  │
└─────────────┘                    └───────────────────────┘        └──────────────┘

Embedded (library)

┌─────────────┐                    ┌──────────────────────────────────────────────┐
│  Client App │◄──────────────────►│  Your process                                │
│ (iOS/Android│  WebSocket (TLS)   │  ┌─────────────────┐  ┌────────────────────┐ │
└─────────────┘                    │  │  BridgeServer   │◄►│  Agent message loop│ │
                                   │  │  (transport)    │  │ (InProcessTransport│ │
                                   │  └─────────────────┘  └────────────────────┘ │
                                   └──────────────────────────────────────────────┘

No subprocess is spawned. Agent and bridge communicate via in-process channels.

Troubleshooting

| Symptom | Cause | Fix | |---------|-------|-----| | QR code not scanning | Phone camera can't read terminal QR | Increase terminal font size, or copy the pairing URL and open manually | | "Unauthorized" on connect | Wrong or missing auth token | Re-scan QR code | | TLS handshake failure | Certificate mismatch | Delete the config dir and restart to regenerate certs; re-pair the device | | App cannot reach bridge | Firewall blocking the port | Check OS firewall; ensure the port in common.toml is open | | Transport fails to start | common.toml has no enabled = true transport | Run bridge status to see configured transports |

Debugging

# Enable verbose logging
bridge run --agent-command "gemini --experimental-acp" --verbose

# Check which transports are configured
bridge status

# Test agent command independently
echo '{"jsonrpc":"2.0","method":"initialize","id":1}' | gemini --experimental-acp

Security

• Auth token: auto-generated 32-byte random value, stored in common.toml (0600). Transmitted to mobile during QR pairing and stored in the device Keychain.
• TLS: self-signed certificate generated on first run. Certificate fingerprint is included in the QR pairing payload and pinned by the mobile app to prevent MITM attacks.
• Pairing codes: 6-digit, single-use, expire after 60 seconds. Rate-limited to 5 attempts per code.
• common.toml: contains all secrets. Permissions are set to 0600 automatically. Keep it secure.

To rotate credentials (invalidates all paired devices):

# Using aptove run (embedded bridge):
rm ~/Library/Application\ Support/Aptove/common.toml   # macOS
rm ~/.config/Aptove/common.toml                        # Linux
aptove run --qr

# Using standalone bridge binary:
rm ~/Library/Application\ Support/com.aptove.bridge/common.toml   # macOS
rm ~/.config/bridge/common.toml                                    # Linux
bridge run --agent-command "aptove stdio" --qr

Development

cargo build --release    # Build
cargo test               # Run tests

License

Apache 2.0 — see LICENSE