diff --git a/agent/src/agent/jobs/heartbeat.py b/agent/src/agent/jobs/heartbeat.py
new file mode 100644
index 0000000..e8f3da5
--- /dev/null
+++ b/agent/src/agent/jobs/heartbeat.py
@@ -0,0 +1,34 @@
+"""Heartbeat: prove Firefly API + agentdb connectivity on a schedule."""
+
+from __future__ import annotations
+
+import logging
+from datetime import datetime, timezone
+
+from agent.config import AgentConfig
+from agent.db import connect
+from agent.firefly import FireflyClient
+
+logger = logging.getLogger(__name__)
+
+
+def run_heartbeat(cfg: AgentConfig, client: FireflyClient | None = None) -> str:
+    if client is None:
+        client = FireflyClient(cfg.firefly_url, cfg.firefly_token)
+
+    started_at = datetime.now(timezone.utc)
+    try:
+        info = client.about()
+        status, detail = "ok", f"firefly version {info.get('version', 'unknown')}"
+    except Exception as exc:  # any failure is a recorded outcome, not a crash
+        status, detail = "error", f"{type(exc).__name__}: {exc}"
+        logger.warning("heartbeat failed: %s", detail)
+
+    finished_at = datetime.now(timezone.utc)
+    with connect(cfg) as conn:
+        conn.execute(
+            "INSERT INTO sync_runs (connector, started_at, finished_at, status, detail)"
+            " VALUES (%s, %s, %s, %s, %s)",
+            ("heartbeat", started_at, finished_at, status, detail),
+        )
+    return status
diff --git a/agent/tests/test_heartbeat.py b/agent/tests/test_heartbeat.py
new file mode 100644
index 0000000..1775f21
--- /dev/null
+++ b/agent/tests/test_heartbeat.py
@@ -0,0 +1,48 @@
+from agent.db import connect, ensure_database, run_migrations
+from agent.firefly import FireflyError
+from agent.jobs.heartbeat import run_heartbeat
+
+
+class FakeFirefly:
+    def __init__(self, version: str | None = None, error: Exception | None = None):
+        self._version = version
+        self._error = error
+
+    def about(self) -> dict:
+        if self._error:
+            raise self._error
+        return {"version": self._version}
+
+
+def _last_run(cfg):
+    with connect(cfg) as conn:
+        return conn.execute(
+            "SELECT connector, status, detail, started_at, finished_at"
+            " FROM sync_runs ORDER BY id DESC LIMIT 1"
+        ).fetchone()
+
+
+def test_heartbeat_records_ok(cfg):
+    ensure_database(cfg)
+    run_migrations(cfg)
+
+    status = run_heartbeat(cfg, client=FakeFirefly(version="6.1.1"))
+
+    assert status == "ok"
+    connector, db_status, detail, started_at, finished_at = _last_run(cfg)
+    assert connector == "heartbeat"
+    assert db_status == "ok"
+    assert "6.1.1" in detail
+    assert finished_at >= started_at
+
+
+def test_heartbeat_records_error_and_does_not_raise(cfg):
+    ensure_database(cfg)
+    run_migrations(cfg)
+
+    status = run_heartbeat(cfg, client=FakeFirefly(error=FireflyError("GET /api/v1/about -> 401")))
+
+    assert status == "error"
+    connector, db_status, detail, *_ = _last_run(cfg)
+    assert db_status == "error"
+    assert "401" in detail