diff --git a/muse/heartbeat.md b/muse/heartbeat.md
new file mode 100644
index 000000000..a0e43342f
--- /dev/null
+++ b/muse/heartbeat.md
@@ -0,0 +1,21 @@
+{
+  "type": "cogitate",
+
+  "title": "Heartbeat",
+  "description": "Periodic self-check — verifies system health, journal quality, and tends agency.md",
+  "instructions": {"system": "journal", "facets": true, "now": true}
+
+}
+
+## Constraints
+- Do NOT produce user-facing output
+- Do NOT execute destructive changes (entity merges, facet changes) — add them as suggestions to `sol/agency.md`
+- All findings and recommendations go to `sol/agency.md`
+
+## Steps
+1. **System health**: Run `sol call health status` to check service health. Review recent health logs for anomalies.
+2. **Journal quality**: Run `sol call health journal-layout` and `sol call health agent-runs` to verify journal structure and recent agent execution over the last 3 days.
+3. **Tend agency.md**: Read `sol/agency.md`. Mark resolved items, prune stale suggestions, and add any new findings from the health and journal-quality checks.
+4. **Curation**: Run `sol call speakers suggest` for speaker suggestions. Run `sol call entities list` and `sol call entities detect` to check for merge candidates or stale entities, but record recommendations in `sol/agency.md` rather than making destructive changes.
+5. **Review self.md**: Read `sol/self.md`. Only update it if genuine new patterns are observed. Do not change it just to change it.
+6. **Git commit + push**: If any files were modified (`agency.md`, `self.md`), commit and push those changes.
diff --git a/sol.py b/sol.py
index 87a266af4..6fd0e7973 100644
--- a/sol.py
+++ b/sol.py
@@ -69,6 +69,7 @@ COMMANDS: dict[str, str] = {
     "call": "think.call",
     "help": "think.help_cli",
     "chat": "think.chat_cli",
+    "heartbeat": "think.heartbeat",
     # convey package - web UI
     "convey": "convey.cli",
     "restart-convey": "convey.restart",
@@ -103,6 +104,7 @@ GROUPS: dict[str, list[str]] = {
         "health",
         "callosum",
         "notify",
+        "heartbeat",
     ],
     "Observe (capture)": [
         "transcribe",
diff --git a/think/heartbeat.py b/think/heartbeat.py
new file mode 100644
index 000000000..81122c2c0
--- /dev/null
+++ b/think/heartbeat.py
@@ -0,0 +1,101 @@
+# SPDX-License-Identifier: AGPL-3.0-only
+# Copyright (c) 2026 sol pbc
+
+"""CLI command for periodic self-check agent."""
+
+from __future__ import annotations
+
+import argparse
+import logging
+import os
+import sys
+import time
+from datetime import datetime
+from pathlib import Path
+
+from think.cortex_client import cortex_request, wait_for_agents
+from think.utils import get_journal, setup_cli
+
+logger = logging.getLogger(__name__)
+
+
+def main() -> None:
+    """Entry point for ``sol heartbeat``."""
+    parser = argparse.ArgumentParser(
+        prog="sol heartbeat",
+        description="Run periodic self-check agent",
+    )
+    args = setup_cli(parser)
+
+    journal = Path(get_journal())
+    health_dir = journal / "health"
+    health_dir.mkdir(parents=True, exist_ok=True)
+    pid_file = health_dir / "heartbeat.pid"
+
+    try:
+        # PID file guard
+        if pid_file.exists():
+            try:
+                existing_pid = int(pid_file.read_text().strip())
+                os.kill(existing_pid, 0)
+                # Process is alive - exit cleanly
+                logger.info("Heartbeat already running (PID %d)", existing_pid)
+                sys.exit(0)
+            except ProcessLookupError:
+                # Dead process - stale PID file, remove and continue
+                logger.info("Removing stale PID file (PID %d)", existing_pid)
+                pid_file.unlink(missing_ok=True)
+            except PermissionError:
+                # Process alive but different user
+                logger.info(
+                    "Heartbeat already running (PID %d, different user)", existing_pid
+                )
+                sys.exit(0)
+            except ValueError:
+                # Corrupt PID file
+                logger.warning("Corrupt PID file, removing")
+                pid_file.unlink(missing_ok=True)
+
+        # Write our PID
+        pid_file.write_text(str(os.getpid()))
+        start_time = time.monotonic()
+
+        # Spawn heartbeat agent
+        agent_id = cortex_request(prompt="Run heartbeat check", name="heartbeat")
+        if agent_id is None:
+            logger.error("Failed to send heartbeat request to cortex")
+            _log_run(health_dir, start_time, "error")
+            sys.exit(1)
+
+        logger.info("Heartbeat agent started (ID: %s)", agent_id)
+
+        # Wait for completion
+        completed, timed_out = wait_for_agents([agent_id], timeout=300)
+
+        # Determine outcome
+        if agent_id in timed_out:
+            logger.error("Heartbeat agent timed out")
+            _log_run(health_dir, start_time, "timeout")
+            sys.exit(2)
+
+        end_state = completed.get(agent_id, "unknown")
+        if end_state == "finish":
+            logger.info("Heartbeat completed successfully")
+            _log_run(health_dir, start_time, "success")
+            sys.exit(0)
+        else:
+            logger.error("Heartbeat agent failed: %s", end_state)
+            _log_run(health_dir, start_time, "error")
+            sys.exit(1)
+
+    finally:
+        pid_file.unlink(missing_ok=True)
+
+
+def _log_run(health_dir: Path, start_time: float, outcome: str) -> None:
+    """Append one line to heartbeat.log."""
+    duration = int(time.monotonic() - start_time)
+    timestamp = datetime.now().isoformat(timespec="seconds")
+    log_file = health_dir / "heartbeat.log"
+    with open(log_file, "a") as f:
+        f.write(f"{timestamp} duration={duration}s outcome={outcome}\n")