paseo/docs/architecture.md

Architecture

Paseo is a client-server system for monitoring and controlling local AI coding agents. The daemon runs on your machine, manages agent processes, and streams their output in real time over WebSocket. Clients (mobile app, CLI, desktop app) connect to the daemon to observe and interact with agents.

Your code never leaves your machine. Paseo is local-first.

System overview

┌─────────────┐    ┌─────────────┐    ┌─────────────┐
│  Mobile App  │    │     CLI     │    │ Desktop App │
│   (Expo)     │    │ (Commander) │    │ (Electron)  │
└──────┬───────┘    └──────┬──────┘    └──────┬──────┘
       │                   │                  │
       │    WebSocket      │    WebSocket     │    Managed subprocess
       │    (direct or     │    (direct)      │    + WebSocket
       │     via relay)    │                  │
       └───────────┬───────┴──────────────────┘
                   │
            ┌──────▼──────┐
            │   Daemon    │
            │  (Node.js)  │
            └──────┬──────┘
                   │
      ┌────────────┼────────────┬────────────┬────────────┐
      │            │            │            │            │
┌─────▼─────┐ ┌───▼────┐ ┌──────▼─────┐ ┌────▼─────┐ ┌────▼────┐
│  Claude   │ │ Codex  │ │  Copilot   │ │ OpenCode │ │   Pi    │
│  Agent    │ │ Agent  │ │   Agent    │ │  Agent   │ │ Agent   │
│  SDK      │ │ Server │ │    ACP     │ │          │ │         │
└───────────┘ └────────┘ └────────────┘ └──────────┘ └─────────┘

Components at a glance

• Daemon: Local server that spawns and manages agent processes and exposes the WebSocket API.
• App: Cross-platform Expo client for iOS, Android, web, and the shared UI used by desktop.
• CLI: Terminal interface for agent workflows that can also start and manage the daemon.
• Desktop app: Electron wrapper around the web app that bundles and auto-manages its own daemon.
• Relay: Optional encrypted bridge for remote access without opening ports directly.

Packages

packages/server — The daemon

The heart of Paseo. A Node.js process that:

• Listens for WebSocket connections from clients
• Manages agent lifecycle (create, run, stop, resume, archive)
• Streams agent output in real time via a timeline model
• Exposes an MCP server for agent-to-agent control
• Optionally connects outbound to a relay for remote access

All paths are under packages/server/src/.

Key modules:

Module	Responsibility
server/bootstrap.ts	Daemon initialization: HTTP server, WS server, agent manager, storage, relay
server/websocket-server.ts	WebSocket connection management, hello handshake, binary frame routing
server/session.ts	Per-client session state, timeline subscriptions, terminal operations
server/agent/agent-manager.ts	Agent lifecycle state machine, timeline tracking, subscriber management
server/agent/agent-storage.ts	File-backed JSON persistence at $PASEO_HOME/agents/
server/agent/mcp-server.ts	MCP server for sub-agent creation, permissions, timeouts
server/agent/providers/	Provider adapters (see "Agent providers" below)
server/relay-transport.ts	Outbound relay connection with E2E encryption
server/schedule/	Cron-based scheduled agents
server/loop-service.ts	Looping agent runs that retry until an exit condition
server/chat/	Chat rooms for agent-to-agent and human-to-agent messaging

packages/protocol — Wire schemas and shared protocol types

The source of truth for WebSocket messages, binary frame codecs, endpoint parsing, agent timeline types, provider config schemas, and other values shared by daemon and clients. Server, app, CLI, and @getpaseo/client all depend on this package; it does not depend on the server.

packages/client — Daemon client library and SDK facade

Owns the low-level daemon WebSocket driver plus the higher-level PaseoClient facade. App and CLI may import the low-level driver from @getpaseo/client/internal/daemon-client during migration, while new SDK-shaped code imports from @getpaseo/client.

packages/app — Mobile + web client (Expo)

Cross-platform React Native app that connects to one or more daemons.

• Expo Router navigation (/h/[serverId]/workspace/[workspaceId], /h/[serverId]/agent/[agentId], etc.)
• HostRuntimeController manages saved host connections, reconnection, and per-host runtime state
• SessionContext wraps the daemon client for the active session
• Composer UI and submit/draft behavior live in packages/app/src/composer/; screens and panels should integrate it from there instead of dropping composer internals into components/, hooks/, or screens/workspace/
• Timeline reducers in timeline/session-stream-reducers.ts handle compaction, gap detection, sequence-based deduplication
• Timeline sync correctness is documented in docs/timeline-sync.md: live streams are for immediacy, fetch_agent_timeline_request is authoritative, and catch-up is paged but complete.
• Voice features: dictation (STT) and voice agent (realtime)

packages/cli — Command-line client

Commander.js CLI with Docker-style commands. Common agent operations are also exposed at the top level (e.g. paseo ls, paseo run).

• paseo agent ls/run/import/attach/logs/stop/delete/send/inspect/wait/archive/reload/update/mode
• paseo daemon start/stop/restart/status/pair/set-password
• paseo chat ls/create/inspect/post/read/wait/delete
• paseo terminal ls/create/capture/send-keys/kill
• paseo loop run/ls/inspect/logs/stop
• paseo schedule create/ls/inspect/update/pause/resume/run-once/logs/delete
• paseo permit allow/deny/ls
• paseo provider ls/models
• paseo worktree create/ls/archive
• paseo speech …

Communicates with the daemon via the same WebSocket protocol as the app.

packages/relay — E2E encrypted relay

Enables remote access when the daemon is behind a firewall.

• Curve25519 ECDH key exchange + XSalsa20-Poly1305 (NaCl box) encryption
• Relay server is zero-knowledge — it routes encrypted bytes, cannot read content
• Client and daemon channels with identical API (createClientChannel, createDaemonChannel)
• Pairing via QR code transfers the daemon's public key to the client
• Self-hosted relays opt into TLS with daemon.relay.useTls or PASEO_RELAY_USE_TLS=true; the public (client-facing) TLS setting can be overridden independently via daemon.relay.publicUseTls or PASEO_RELAY_PUBLIC_USE_TLS

See SECURITY.md for the full threat model.

packages/desktop — Desktop app (Electron)

Electron wrapper for macOS, Linux, and Windows.

• Can spawn the daemon as a managed subprocess
• Native file access for workspace integration
• Same WebSocket client as mobile app

Multi-window (hybrid land-on model). createWindow() in main.ts is reusable: ⌘⇧N/File→New Window, relaunching the app (second-instance), and the sidebar "Open in new window" action each open a fresh BrowserWindow. Every window shows the full sidebar — there is no per-window project ownership or filtering. "Land on a project" is delivered by a per-webContents PendingOpenProjectStore: each window pulls its own pending project path on mount (paseo:get-pending-open-project) and runs the normal open-project flow, identical to a CLI paseo <path> launch.

Window-state v1 limitation: only the first window of a session restores and persists saved geometry (size/position/maximized). Windows opened via ⌘⇧N / second-instance / "Open in new window" open at the default size, OS-cascaded, and do not persist — this avoids every window stacking on the same restored bounds and fighting over the single window-state store. Lifting this needs per-window state keys.

In-app browser panes are not yet per-window. The active-browser id (features/browser-webviews.ts) and the webview registration queue (pendingBrowserWebviewIds in main.ts) are process-global. With browser panes open in two windows, a menu Reload can target the other window's webview, and near-simultaneous webview attach across windows can register under the wrong browser id. Multi-window v1 ships windows; making the browser-webview subsystem window-scoped is a follow-up.

packages/website — Marketing site

TanStack Router + Cloudflare Workers. Serves paseo.sh.

WebSocket protocol

All clients speak the same WebSocket protocol over a single connection that mixes JSON text frames and a small binary framing for terminal streams. Schemas live in packages/protocol/src/messages.ts.

Handshake:

Client → Server:  WSHelloMessage {
                    type: "hello",
                    clientId,
                    clientType: "mobile" | "browser" | "cli" | "mcp",
                    protocolVersion,
                    appVersion?,
                    capabilities?: { voice?, pushNotifications?, ... },
                  }
Server → Client:  status message with payload { status: "server_info",
                    serverId, hostname, version, capabilities?, features }

There is no dedicated welcome message; the server emits a status session message after accepting the hello, then begins streaming. The session stores client capabilities from the hello and rehydrates them on reconnect, so the wire boundary can ask one question: session.supports(...).

Top-level WS envelopes are hello, recording_state, ping/pong, and session (which wraps the rich union of session messages).

Client liveness checks use the top-level JSON ping/pong envelope, not a session RPC and not RFC6455 protocol ping. The app runs through browser and React Native WebSocket APIs, which do not expose protocol ping, so this envelope is the portable way to test the direct or relay data path. Session RPC timeouts are operation failures and must not be treated as proof that the socket is dead.

New session RPCs use dotted names with .request and .response suffixes, such as checkout.github.set_auto_merge.request and checkout.github.set_auto_merge.response. See rpc-namespacing.md for the convention and migration rules for older flat RPC names.

Notable session message types:

• agent_update — Agent state changed (status, title, labels)
• agent_stream — New timeline event from a running agent
• workspace_update, script_status_update, workspace_setup_progress — Workspace state
• agent_permission_request / agent_permission_resolved — Tool-call permission flow
• agent_deleted, agent_archived, agent_status, agent_list
• checkout_status_update, checkout_diff_update, and the full checkout_* request/response set for git operations
• Terminal subscribe/input/capture commands
• Voice/dictation streaming events (dictation_stream_*, assistant_chunk, audio_output, transcription_result)
• Request/response pairs for fetch, list, create, etc., correlated by requestId; failures use rpc_error

Binary frames (terminal stream protocol):

Terminal I/O is sent as binary WebSocket frames decoded by decodeTerminalStreamFrame in shared/binary-frames/terminal.ts. The layout is:

• 1-byte opcode: Output (0x01), Input (0x02), Resize (0x03), Snapshot (0x04)
• 1-byte slot: terminal slot id
• variable payload: bytes for output/input, JSON-encoded { rows, cols } for resize, terminal snapshot for snapshot

Terminal PTY size is last-interacting-client-wins. A client claims the PTY size only when its terminal viewport genuinely changes size or the user focuses/taps the terminal. Passive rendering work — attaching, restoring visibility, font settling, renderer refits, or just looking at a visible terminal — must not send a resize frame. The server does not broadcast resize ownership; the resized PTY redraws through normal output, and every attached client renders that output in its own local viewport.

There is also a separate file-transfer binary frame format in the same directory, used for download/upload streams.

Compatibility rules

• WebSocket schemas are append-only. Add fields, do not remove fields, and never make optional fields required.
• New wire enum values must be gated at serialization with session.supports(CLIENT_CAPS.someCapability).
• Session stores client capabilities from the hello handshake and rehydrates them on reconnect, so the wire boundary can ask one question: session.supports(...).

Example: adding a new enum value

// 1. Add CLIENT_CAPS.newThing = "new_thing"
// 2. Let new clients advertise it in WS hello
// 3. Keep the shared producer schema strict
// 4. Gate the new emitted value: session.supports(CLIENT_CAPS.newThing) ? "new_value" : "old_value"

Agent lifecycle

The lifecycle states are defined in shared/agent-lifecycle.ts:

initializing → idle ⇄ running
        ↓       ↓        ↓
              error
                ↓
              closed

• initializing — provider session is being created
• idle — has a live session, awaiting the next prompt
• running — provider is currently producing a turn
• error — last attempt failed; session is still attached
• closed — terminal state, no live session

ManagedAgent is a discriminated union over those lifecycle tags. Notes:

• AgentManager is the source of truth for agent state and broadcasts updates to all subscribers
• Timeline is append-only with epochs (each run starts a new epoch). Storage uses sequence numbers for client-side dedup; the default fetch page is 200 items
• Timeline row timestamp values are canonical daemon-owned timestamps. Providers may supply original replay timestamps, but clients must not guess timestamp trust or hide time UI based on local clock heuristics.
• Events stream to connected clients in real time; correctness is backed by authoritative timeline fetches and paged-to-completion catch-up.
• Agent state persists to $PASEO_HOME/agents/{cwd-with-dashes}/{agent-id}.json (timeline rows live alongside the record)

Agent providers

Each provider implements the AgentClient interface in agent/agent-sdk-types.ts. Provider implementations live in agent/providers/.

The built-in, user-facing providers are Claude Code, Codex, Copilot, OpenCode, and Pi. Additional adapters exist in the same directory for ACP-compatible agents and internal use:

Provider	Wraps	Session format
Claude (claude/)	Anthropic Agent SDK	~/.claude/projects/{cwd}/{session-id}.jsonl
Codex	Codex AppServer (codex-app-server)	~/.codex/sessions/{date}/rollout-{ts}-{id}.jsonl
Copilot	GitHub Copilot via ACP	Provider-managed
OpenCode	OpenCode server / CLI	Provider-managed
Cursor	ACP wrapper (acp-agent)	Provider-managed
Generic ACP	ACP wrapper	Provider-managed
Pi	Local Pi RPC process	Provider-managed
Mock load test	In-process fake	In-memory

All providers:

• Handle their own authentication (Paseo does not manage API keys)
• Support session resume via persistence handles
• Map tool calls to a normalized ToolCallDetail type
• Expose provider-specific modes (plan, default, full-access)

Data flow: running an agent

1. Client sends CreateAgentRequestMessage with config (prompt, cwd, provider, model, mode)
2. Session routes to AgentManager.create()
3. AgentManager creates a ManagedAgent, initializes provider session
4. Provider runs the agent → emits AgentStreamEvent items
5. Events append to the agent timeline, broadcast to all subscribed clients
6. Tool calls are normalized to ToolCallDetail (shell, read, edit, write, search, etc.)
7. Permission requests flow: agent → server → client → user decision → server → agent

Storage

$PASEO_HOME defaults to ~/.paseo. The most important files:

$PASEO_HOME/
├── agents/{cwd-with-dashes}/{agent-id}.json   # Agent record + persisted timeline rows
├── projects/projects.json                      # Project registry
├── projects/workspaces.json                    # Workspace registry
├── chat/                                       # Chat rooms
├── schedules/                                  # Scheduled-agent definitions and runs
├── loops/                                      # Loop runs and logs
├── config.json                                 # Daemon config (mutable)
├── daemon-keypair.json                         # Daemon identity for relay/E2EE
├── push-tokens.json                            # Mobile push tokens
├── paseo.sock / paseo.pid                      # Local IPC socket and pidfile
└── daemon.log                                  # Daemon trace logs (rotated)

Deployment models

1. Local daemon (default): paseo daemon start on 127.0.0.1:6767
2. Managed desktop: Electron app spawns daemon as subprocess
3. Remote + relay: Daemon behind firewall, relay bridges with E2E encryption