diff --git a/gateway/memory_monitor.py b/gateway/memory_monitor.py
new file mode 100644
index 00000000000..bacbbba34ef
--- /dev/null
+++ b/gateway/memory_monitor.py
@@ -0,0 +1,230 @@
+"""Periodic process memory usage logging for the gateway.
+
+Ported from cline/cline#10343 (src/standalone/memory-monitor.ts).
+
+The gateway is a long-lived process that accumulates memory as it caches
+agent instances, session transcripts, tool schemas, memory providers, MCP
+connections, etc.  A slow leak in any of those subsystems is invisible
+in a single log line — you only see it by watching RSS climb over hours.
+
+This module emits a single structured ``[MEMORY] ...`` line every N
+minutes (default 5) so maintainers investigating a suspected leak can
+grep ``agent.log`` / ``gateway.log`` for a time series of RSS + Python
+GC stats.  The timer runs in a background thread and shuts down cleanly
+with the gateway.
+
+Design notes (parity with the Cline port):
+  * Grep-friendly single-line format beginning ``[MEMORY]``.
+  * Final snapshot logged on shutdown so "last RSS before exit" is
+    always in the log.
+  * Baseline snapshot logged immediately on start.
+  * Daemon thread — never blocks process exit.
+  * Uses ``resource`` (stdlib, Linux/macOS) first and falls back to
+    ``psutil`` when ``resource`` isn't available (Windows).  Both are
+    optional; when neither works we emit a single WARNING and disable
+    the monitor rather than crashing the gateway.
+
+Config: ``logging.memory_monitor`` in ``config.yaml`` — see
+``hermes_cli/config.py`` for the defaults block.
+"""
+
+from __future__ import annotations
+
+import gc
+import logging
+import os
+import sys
+import threading
+import time
+from typing import Optional
+
+logger = logging.getLogger(__name__)
+
+_BYTES_TO_MB = 1024 * 1024
+
+_monitor_thread: Optional[threading.Thread] = None
+_stop_event: Optional[threading.Event] = None
+_start_time: Optional[float] = None
+_interval_seconds: float = 300.0  # 5 minutes
+_lock = threading.Lock()
+
+
+def _get_rss_mb() -> Optional[int]:
+    """Return current process resident set size in MB, or None if unavailable.
+
+    Tries ``resource.getrusage`` first (Linux/macOS, no extra deps), then
+    falls back to ``psutil`` which is an optional hermes-agent dep.
+    """
+    # Linux / macOS — resource is stdlib.  On Linux ru_maxrss is in KB,
+    # on macOS it is in bytes (yes, really).  We use it as a cheap
+    # "current" RSS — ru_maxrss reports the high-water mark for the
+    # process, which is what you actually want for leak detection.
+    try:
+        import resource
+
+        maxrss = resource.getrusage(resource.RUSAGE_SELF).ru_maxrss
+        if sys.platform == "darwin":
+            return int(maxrss / _BYTES_TO_MB)
+        # Linux / other unices: KB
+        return int(maxrss / 1024)
+    except Exception:
+        pass
+
+    # Fallback: psutil (Windows, or unusual unix without resource).
+    try:
+        import psutil  # type: ignore
+
+        rss = psutil.Process(os.getpid()).memory_info().rss
+        return int(rss / _BYTES_TO_MB)
+    except Exception:
+        return None
+
+
+def log_memory_usage(prefix: str = "") -> None:
+    """Log current memory usage in a grep-friendly ``[MEMORY] ...`` line.
+
+    Safe to call on-demand from any thread at important lifecycle
+    moments (after shutdown, after context compression, etc.).
+
+    Parameters
+    ----------
+    prefix
+        Optional extra tag inserted after ``[MEMORY]`` — e.g.
+        ``"baseline"``, ``"shutdown"``.
+    """
+    rss = _get_rss_mb()
+    uptime = int(time.monotonic() - _start_time) if _start_time else 0
+    # gc.get_stats() returns per-generation collection counts; the sum
+    # is a cheap proxy for "how much garbage have we created".
+    try:
+        gc_counts = gc.get_count()  # (gen0, gen1, gen2)
+    except Exception:
+        gc_counts = (0, 0, 0)
+    # Thread count is a handy correlate when diagnosing thread leaks.
+    try:
+        thread_count = threading.active_count()
+    except Exception:
+        thread_count = 0
+
+    tag = f"{prefix} " if prefix else ""
+    if rss is None:
+        logger.info(
+            "[MEMORY] %srss=unavailable gc=%s threads=%d uptime=%ds",
+            tag,
+            gc_counts,
+            thread_count,
+            uptime,
+        )
+    else:
+        logger.info(
+            "[MEMORY] %srss=%dMB gc=%s threads=%d uptime=%ds",
+            tag,
+            rss,
+            gc_counts,
+            thread_count,
+            uptime,
+        )
+
+
+def _monitor_loop(stop_event: threading.Event, interval: float) -> None:
+    """Background thread body — log every ``interval`` seconds until stopped."""
+    while not stop_event.wait(interval):
+        try:
+            log_memory_usage()
+        except Exception as e:
+            # Never let the monitor crash the gateway; just log and carry on.
+            logger.debug("Memory monitor iteration failed: %s", e)
+
+
+def start_memory_monitoring(interval_seconds: float = 300.0) -> bool:
+    """Start periodic memory usage logging in a daemon thread.
+
+    Logs immediately to capture a baseline, then every ``interval_seconds``.
+    Safe to call multiple times — subsequent calls are no-ops while the
+    first monitor is still running.
+
+    Parameters
+    ----------
+    interval_seconds
+        How often to log.  Default 300s (5 minutes), matching the
+        upstream cline/cline implementation.
+
+    Returns
+    -------
+    bool
+        True if a fresh monitor thread was started, False if one was
+        already running or if memory introspection isn't available.
+    """
+    global _monitor_thread, _stop_event, _start_time, _interval_seconds
+
+    with _lock:
+        if _monitor_thread is not None and _monitor_thread.is_alive():
+            return False
+
+        # Sanity-check that we can read RSS at all.  If neither resource
+        # nor psutil works, no point spinning a thread that can only log
+        # "rss=unavailable" forever — warn once and bail.
+        if _get_rss_mb() is None:
+            logger.warning(
+                "[MEMORY] Memory monitoring unavailable: neither resource.getrusage "
+                "nor psutil could read process RSS — skipping periodic logging.",
+            )
+            return False
+
+        _start_time = time.monotonic()
+        _interval_seconds = float(interval_seconds)
+        _stop_event = threading.Event()
+
+        # Baseline snapshot before the loop starts.
+        log_memory_usage(prefix="baseline")
+
+        _monitor_thread = threading.Thread(
+            target=_monitor_loop,
+            args=(_stop_event, _interval_seconds),
+            name="gateway-memory-monitor",
+            daemon=True,
+        )
+        _monitor_thread.start()
+
+        logger.info(
+            "[MEMORY] Periodic memory monitoring started (interval: %ds)",
+            int(_interval_seconds),
+        )
+        return True
+
+
+def stop_memory_monitoring(timeout: float = 2.0) -> None:
+    """Stop the monitor thread and log a final snapshot.
+
+    Safe to call even if ``start_memory_monitoring()`` was never called.
+    """
+    global _monitor_thread, _stop_event
+
+    with _lock:
+        if _stop_event is None or _monitor_thread is None:
+            return
+
+        # Final snapshot before teardown so "last RSS" is always in the log.
+        try:
+            log_memory_usage(prefix="shutdown")
+        except Exception:
+            pass
+
+        _stop_event.set()
+        thread = _monitor_thread
+        _monitor_thread = None
+        _stop_event = None
+
+    # Join outside the lock so a stuck log call can't deadlock shutdown.
+    try:
+        thread.join(timeout=timeout)
+    except Exception:
+        pass
+
+    logger.info("[MEMORY] Periodic memory monitoring stopped")
+
+
+def is_running() -> bool:
+    """True if the background monitor thread is alive."""
+    with _lock:
+        return _monitor_thread is not None and _monitor_thread.is_alive()
diff --git a/gateway/run.py b/gateway/run.py
index f9a282a413f..a5eaafcb063 100644
--- a/gateway/run.py
+++ b/gateway/run.py
@@ -16800,6 +16800,33 @@ async def start_gateway(config: Optional[GatewayConfig] = None, replace: bool =
     from hermes_logging import setup_logging
     setup_logging(hermes_home=_hermes_home, mode="gateway")
 
+    # Periodic process memory usage logging (gateway only) — emits a
+    # grep-friendly "[MEMORY] rss=...MB ..." line every N minutes so
+    # slow leaks in the long-lived gateway process show up as a time
+    # series in agent.log / gateway.log.  Ported from cline/cline#10343.
+    # Controlled by the logging.memory_monitor section in config.yaml.
+    try:
+        from gateway import memory_monitor as _memory_monitor
+
+        _mm_cfg = {}
+        try:
+            # config is loaded a few lines up; re-read the logging section
+            # here so we pick up user overrides without coupling to local
+            # variable names inside the start_gateway body.
+            from hermes_cli.config import load_config as _load_cli_config
+
+            _mm_cfg = (_load_cli_config() or {}).get("logging", {}).get("memory_monitor", {}) or {}
+        except Exception:
+            _mm_cfg = {}
+        if _mm_cfg.get("enabled", True):
+            try:
+                _mm_interval = float(_mm_cfg.get("interval_seconds", 300))
+            except (TypeError, ValueError):
+                _mm_interval = 300.0
+            _memory_monitor.start_memory_monitoring(interval_seconds=_mm_interval)
+    except Exception as _mm_exc:
+        logger.debug("Failed to start memory monitor: %s", _mm_exc)
+
     # Optional stderr handler — level driven by -v/-q flags on the CLI.
     # verbosity=None (-q/--quiet): no stderr output
     # verbosity=0    (default):    WARNING and above
@@ -17016,6 +17043,16 @@ async def start_gateway(config: Optional[GatewayConfig] = None, replace: bool =
     except Exception:
         pass
 
+    # Stop the periodic memory monitor (if it was started above).
+    # This also emits one final "[MEMORY] shutdown rss=..." line so the
+    # last RSS reading before gateway exit is always in the log.
+    try:
+        from gateway import memory_monitor as _memory_monitor
+
+        _memory_monitor.stop_memory_monitoring(timeout=2.0)
+    except Exception:
+        pass
+
     if runner.exit_code is not None:
         raise SystemExit(runner.exit_code)
 
diff --git a/hermes_cli/config.py b/hermes_cli/config.py
index 574f2397d91..81706d1edb4 100644
--- a/hermes_cli/config.py
+++ b/hermes_cli/config.py
@@ -1477,6 +1477,15 @@ DEFAULT_CONFIG = {
         "level": "INFO",       # Minimum level for agent.log: DEBUG, INFO, WARNING
         "max_size_mb": 5,      # Max size per log file before rotation
         "backup_count": 3,     # Number of rotated backup files to keep
+        # Periodic process memory usage logging (gateway only). Emits a
+        # grep-friendly "[MEMORY] rss=...MB ..." line at the configured
+        # interval so slow leaks in the long-lived gateway are visible
+        # in agent.log / gateway.log as a time series. Ported from
+        # cline/cline#10343.
+        "memory_monitor": {
+            "enabled": True,         # Flip to false to silence the periodic line
+            "interval_seconds": 300, # Default: every 5 minutes
+        },
     },
 
     # Remotely-hosted model catalog manifest.  When enabled, the CLI fetches
diff --git a/tests/gateway/test_memory_monitor.py b/tests/gateway/test_memory_monitor.py
new file mode 100644
index 00000000000..64903dc81f8
--- /dev/null
+++ b/tests/gateway/test_memory_monitor.py
@@ -0,0 +1,122 @@
+"""Tests for gateway.memory_monitor — periodic process memory logging.
+
+Ported from cline/cline#10343.  The module logs a structured
+``[MEMORY] rss=...MB ...`` line periodically so long-running gateway
+leaks show up as a time series in agent.log / gateway.log.
+"""
+
+from __future__ import annotations
+
+import logging
+import time
+
+import pytest
+
+from gateway import memory_monitor as mm
+
+
+@pytest.fixture(autouse=True)
+def _ensure_monitor_stopped():
+    """Every test starts from a clean state and leaves one behind."""
+    mm.stop_memory_monitoring(timeout=1.0)
+    yield
+    mm.stop_memory_monitoring(timeout=1.0)
+
+
+def test_log_memory_usage_emits_memory_line(caplog):
+    caplog.set_level(logging.INFO, logger="gateway.memory_monitor")
+    mm.log_memory_usage()
+    memory_lines = [r for r in caplog.records if "[MEMORY]" in r.getMessage()]
+    assert memory_lines, "expected at least one [MEMORY] log record"
+
+
+def test_log_memory_usage_has_grep_friendly_format(caplog):
+    caplog.set_level(logging.INFO, logger="gateway.memory_monitor")
+    mm.log_memory_usage()
+    msg = caplog.records[-1].getMessage()
+    # Grep-friendly contract: line starts with [MEMORY] and carries RSS
+    # (or 'unavailable'), GC counts, thread count, uptime.
+    assert msg.startswith("[MEMORY]"), msg
+    assert "rss=" in msg
+    assert "gc=" in msg
+    assert "threads=" in msg
+    assert "uptime=" in msg
+
+
+def test_log_memory_usage_with_prefix(caplog):
+    caplog.set_level(logging.INFO, logger="gateway.memory_monitor")
+    mm.log_memory_usage(prefix="baseline")
+    msg = caplog.records[-1].getMessage()
+    assert "[MEMORY] baseline " in msg
+
+
+def test_start_logs_baseline_and_returns_true(caplog):
+    caplog.set_level(logging.INFO, logger="gateway.memory_monitor")
+    # Large interval so the background timer never fires during the test —
+    # we're only checking the synchronous baseline behavior here.
+    started = mm.start_memory_monitoring(interval_seconds=3600.0)
+    assert started is True
+    assert mm.is_running() is True
+
+    messages = [r.getMessage() for r in caplog.records]
+    assert any("[MEMORY] baseline " in m for m in messages), messages
+    assert any("Periodic memory monitoring started" in m for m in messages), messages
+
+
+def test_double_start_is_noop():
+    assert mm.start_memory_monitoring(interval_seconds=3600.0) is True
+    assert mm.start_memory_monitoring(interval_seconds=3600.0) is False
+    assert mm.is_running() is True
+
+
+def test_stop_logs_shutdown_snapshot(caplog):
+    mm.start_memory_monitoring(interval_seconds=3600.0)
+    caplog.clear()
+    caplog.set_level(logging.INFO, logger="gateway.memory_monitor")
+    mm.stop_memory_monitoring(timeout=1.0)
+    assert mm.is_running() is False
+
+    messages = [r.getMessage() for r in caplog.records]
+    assert any("[MEMORY] shutdown " in m for m in messages), messages
+    assert any("Periodic memory monitoring stopped" in m for m in messages), messages
+
+
+def test_stop_without_start_is_noop():
+    # Must not raise, must not log shutdown snapshot.
+    mm.stop_memory_monitoring(timeout=0.5)
+    assert mm.is_running() is False
+
+
+def test_periodic_timer_fires(caplog):
+    caplog.set_level(logging.INFO, logger="gateway.memory_monitor")
+    # Short interval so we can observe multiple ticks inside the test budget.
+    mm.start_memory_monitoring(interval_seconds=0.1)
+    time.sleep(0.45)
+    mm.stop_memory_monitoring(timeout=1.0)
+
+    periodic = [
+        r for r in caplog.records
+        if r.getMessage().startswith("[MEMORY] rss=") or r.getMessage().startswith("[MEMORY] rss=unavailable")
+    ]
+    # baseline + at least 2 periodic + shutdown — but shutdown has the
+    # "shutdown " prefix so it won't match the strict "[MEMORY] rss=" start.
+    # We expect >= 3 bare "[MEMORY] rss=..." lines.
+    assert len(periodic) >= 3, [r.getMessage() for r in caplog.records]
+
+
+def test_thread_is_daemon():
+    mm.start_memory_monitoring(interval_seconds=3600.0)
+    assert mm._monitor_thread is not None
+    assert mm._monitor_thread.daemon is True, (
+        "memory monitor thread must be daemon so it can never block process exit"
+    )
+
+
+def test_unavailable_rss_warns_and_does_not_start(caplog, monkeypatch):
+    # Force both backends to claim unavailable; start should bail.
+    monkeypatch.setattr(mm, "_get_rss_mb", lambda: None)
+    caplog.set_level(logging.WARNING, logger="gateway.memory_monitor")
+    started = mm.start_memory_monitoring(interval_seconds=3600.0)
+    assert started is False
+    assert mm.is_running() is False
+    assert any("Memory monitoring unavailable" in r.getMessage() for r in caplog.records)