Why am I getting heartbeat messages every 30 minutes

Heartbeats run every 30m by default. Tune or disable them:
{
agents: {
defaults: {
heartbeat: {
every: "2h", // or "0m" to disable
},
},
},
}
If HEARTBEAT.md exists but is effectively empty (only blank lines and markdown headers like # Heading), OpenClaw skips the heartbeat run to save API calls. If the file is missing, the heartbeat still runs and the model decides what to do.
Per-agent overrides use agents.list[].heartbeat. Docs: Heartbeat.