Building a personal assistant with OpenCrabs

August 10, 2026 · View on GitHub

OpenCrabs is a WhatsApp + Telegram + Discord + iMessage gateway for Pi agents. Plugins add Mattermost. This guide is the "personal assistant" setup: one dedicated WhatsApp number that behaves like your always-on agent.

⚠️ Safety first

You’re putting an agent in a position to:

  • run commands on your machine (depending on your Pi tool setup)
  • read/write files in your workspace
  • send messages back out via WhatsApp/Telegram/Discord/Mattermost (plugin)

Start conservative:

  • Always set channels.whatsapp.allowFrom (never run open-to-the-world on your personal Mac).
  • Use a dedicated WhatsApp number for the assistant.
  • Heartbeats now default to every 30 minutes. Disable until you trust the setup by setting agents.defaults.heartbeat.every: "0m".

Prerequisites

  • OpenCrabs installed and onboarded — see Getting Started if you haven't done this yet
  • A second phone number (SIM/eSIM/prepaid) for the assistant

You want this:

flowchart TB
    A["<b>Your Phone (personal)<br></b><br>Your WhatsApp<br>+1-555-YOU"] -- message --> B["<b>Second Phone (assistant)<br></b><br>Assistant WA<br>+1-555-ASSIST"]
    B -- linked via QR --> C["<b>Your Mac (OpenCrabs)<br></b><br>Pi agent"]

If you link your personal WhatsApp to OpenCrabs, every message to you becomes “agent input”. That’s rarely what you want.

5-minute quick start

  1. Pair WhatsApp Web (shows QR; scan with the assistant phone):
opencrabs channels login
  1. Start the Gateway (leave it running):
opencrabs gateway --port 18789
  1. Put a minimal config in ~/.opencrabs/config.toml:
{
  channels: { whatsapp: { allowFrom: ["+15555550123"] } },
}

Now message the assistant number from your allowlisted phone.

When onboarding finishes, we auto-open the dashboard and print a clean (non-tokenized) link. If it prompts for auth, paste the token from gateway.auth.token into Control UI settings. To reopen later: opencrabs dashboard.

Give the agent a workspace (AGENTS)

OpenCrabs reads operating instructions and “memory” from its workspace directory.

By default, OpenCrabs uses ~/.opencrabs/ as the agent workspace, and will create it (plus starter SOUL.md, USER.md, AGENTS.md, TOOLS.md, MEMORY.md, CODE.md, SECURITY.md, BOOT.md, HEARTBEAT.md) automatically on setup/first agent run. Seeding never overwrites: a file you have already edited is left exactly as it is. MEMORY.md is loaded for normal sessions only, not for shared ones. Subagent sessions only inject AGENTS.md and TOOLS.md.

Tip: treat this folder like OpenCrabs’s “memory” and make it a git repo (ideally private) so your AGENTS.md + memory files are backed up. If git is installed, brand-new workspaces are auto-initialized.

opencrabs setup

Full workspace layout + backup guide: Agent workspace Memory workflow: Memory

Optional: choose a different workspace with agents.defaults.workspace (supports ~).

{
  agent: {
    workspace: "~/.opencrabs/",
  },
}

If you already ship your own workspace files from a repo, you can disable bootstrap file creation entirely:

{
  agent: {
    skipBootstrap: true,
  },
}

The config that turns it into “an assistant”

OpenCrabs defaults to a good assistant setup, but you’ll usually want to tune:

  • persona/instructions in SOUL.md
  • thinking defaults (if desired)
  • heartbeats (once you trust it)

Example:

{
  logging: { level: "info" },
  agent: {
    model: "anthropic/claude-opus-4-6",
    workspace: "~/.opencrabs/",
    thinkingDefault: "high",
    timeoutSeconds: 1800,
    // Start with 0; enable later.
    heartbeat: { every: "0m" },
  },
  channels: {
    whatsapp: {
      allowFrom: ["+15555550123"],
      groups: {
        "*": { requireMention: true },
      },
    },
  },
  routing: {
    groupChat: {
      mentionPatterns: ["@OpenCrabs", "OpenCrabs"],
    },
  },
  session: {
    scope: "per-sender",
    resetTriggers: ["/new", "/reset"],
    reset: {
      mode: "daily",
      atHour: 4,
      idleMinutes: 10080,
    },
  },
}

Sessions and memory

  • Session files: ~/.opencrabs/agents/<agentId>/sessions/{{SessionId}}.jsonl
  • Session metadata (token usage, last route, etc): ~/.opencrabs/agents/<agentId>/sessions/sessions.json (legacy: ~/.opencrabs/sessions/sessions.json)
  • /new or /reset starts a fresh session for that chat (configurable via resetTriggers). If sent alone, the agent replies with a short hello to confirm the reset.
  • /compact [instructions] compacts the session context and reports the remaining context budget.

Heartbeats (proactive mode)

By default, OpenCrabs runs a heartbeat every 30 minutes with the prompt: Read HEARTBEAT.md if it exists (workspace context). Follow it strictly. Do not infer or repeat old tasks from prior chats. If nothing needs attention, reply HEARTBEAT_OK. Set agents.defaults.heartbeat.every: "0m" to disable.

  • If HEARTBEAT.md exists but is effectively empty (only blank lines and markdown headers like # Heading), OpenCrabs skips the heartbeat run to save API calls.
  • If the file is missing, the heartbeat still runs and the model decides what to do.
  • If the agent replies with HEARTBEAT_OK (optionally with short padding; see agents.defaults.heartbeat.ackMaxChars), OpenCrabs suppresses outbound delivery for that heartbeat.
  • Heartbeats run full agent turns — shorter intervals burn more tokens.
{
  agent: {
    heartbeat: { every: "30m" },
  },
}

Media in and out

Inbound attachments (images/audio/docs) can be surfaced to your command via templates:

  • {{MediaPath}} (local temp file path)
  • {{MediaUrl}} (pseudo-URL)
  • {{Transcript}} (if audio transcription is enabled)

Outbound attachments from the agent: include MEDIA:<path-or-url> on its own line (no spaces). Example:

Here’s the screenshot.
MEDIA:https://example.com/screenshot.png

OpenCrabs extracts these and sends them as media alongside the text.

Operations checklist

opencrabs status          # local status (creds, sessions, queued events)
opencrabs status --all    # full diagnosis (read-only, pasteable)
opencrabs status --deep   # adds gateway health probes (Telegram + Discord)
opencrabs health --json   # gateway health snapshot (WS)

Logs live under /tmp/opencrabs/ (default: opencrabs-YYYY-MM-DD.log).

Next steps