diff --git a/muxplex/settings.py b/muxplex/settings.py
index dc0b234..ee02a9b 100644
--- a/muxplex/settings.py
+++ b/muxplex/settings.py
@@ -8,6 +8,7 @@ import copy
 import json
 import os
 import socket
+import time
 from pathlib import Path
 
 SETTINGS_PATH = Path.home() / ".config" / "muxplex" / "settings.json"
@@ -151,10 +152,36 @@ def patch_settings(patch: dict) -> dict:
                 # restore by index so editing a URL doesn't erase the key.
                 remote["key"] = existing_remote_keys_by_index[i]
 
+    if any(key in SYNCABLE_KEYS for key in patch if key in DEFAULT_SETTINGS):
+        current["settings_updated_at"] = time.time()
+
     save_settings(current)
     return current
 
 
+def apply_synced_settings(incoming_settings: dict, incoming_timestamp: float) -> dict:
+    """Apply synced settings from a remote server.
+
+    Only applies keys that are in SYNCABLE_KEYS. Sets settings_updated_at
+    to the incoming timestamp (NOT time.time()) to prevent sync loops.
+    """
+    current = load_settings()
+    for key in SYNCABLE_KEYS:
+        if key in incoming_settings:
+            current[key] = incoming_settings[key]
+    current["settings_updated_at"] = incoming_timestamp
+    save_settings(current)
+    return current
+
+
+def get_syncable_settings() -> dict:
+    """Return only syncable settings + the settings_updated_at timestamp."""
+    settings = load_settings()
+    result = {key: settings[key] for key in SYNCABLE_KEYS if key in settings}
+    result["settings_updated_at"] = settings.get("settings_updated_at", 0.0)
+    return result
+
+
 def load_federation_key() -> str:
     """Load the federation key from disk or env-overridden path.
 
diff --git a/muxplex/tests/test_settings.py b/muxplex/tests/test_settings.py
index 089291c..856b001 100644
--- a/muxplex/tests/test_settings.py
+++ b/muxplex/tests/test_settings.py
@@ -12,6 +12,8 @@ import muxplex.settings as settings_mod
 from muxplex.settings import (
     DEFAULT_SETTINGS,
     SYNCABLE_KEYS,
+    apply_synced_settings,
+    get_syncable_settings,
     load_federation_key,
     load_settings,
     patch_settings,
@@ -918,3 +920,55 @@ def test_syncable_keys_subset_of_default_settings():
 def test_defaults_include_settings_updated_at():
     """DEFAULT_SETTINGS must include settings_updated_at with default 0.0."""
     assert DEFAULT_SETTINGS["settings_updated_at"] == 0.0
+
+
+# ============================================================
+# Sync-aware patch_settings + apply_synced_settings (task-6)
+# ============================================================
+
+
+def test_patch_settings_bumps_timestamp_for_syncable_key():
+    """patch_settings bumps settings_updated_at when a syncable key is patched."""
+    patch_settings({"fontSize": 20})
+    settings = load_settings()
+    assert settings["settings_updated_at"] > 0.0
+
+
+def test_patch_settings_does_not_bump_timestamp_for_nonsyncable_key():
+    """patch_settings does NOT bump settings_updated_at for non-syncable keys."""
+    patch_settings({"host": "0.0.0.0"})
+    settings = load_settings()
+    assert settings["settings_updated_at"] == 0.0
+
+
+def test_apply_synced_settings_uses_incoming_timestamp():
+    """apply_synced_settings sets settings_updated_at to the incoming timestamp."""
+    apply_synced_settings({"fontSize": 18}, 1712600000.0)
+    settings = load_settings()
+    assert settings["fontSize"] == 18
+    assert settings["settings_updated_at"] == 1712600000.0
+
+
+def test_apply_synced_settings_ignores_nonsyncable_keys():
+    """apply_synced_settings ignores keys not in SYNCABLE_KEYS."""
+    apply_synced_settings({"fontSize": 18, "host": "evil.com"}, 1712600000.0)
+    settings = load_settings()
+    assert settings["fontSize"] == 18
+    assert settings["host"] == "127.0.0.1"  # unchanged from default
+
+
+def test_get_syncable_settings_returns_only_syncable_keys():
+    """get_syncable_settings returns only SYNCABLE_KEYS + settings_updated_at."""
+    result = get_syncable_settings()
+    for key in result:
+        assert key in SYNCABLE_KEYS or key == "settings_updated_at"
+    assert "host" not in result
+    assert "settings_updated_at" in result
+
+
+def test_apply_synced_settings_does_not_use_time_now():
+    """apply_synced_settings must use the incoming timestamp, not time.time()."""
+    old_ts = 1000.0
+    apply_synced_settings({"fontSize": 16}, old_ts)
+    settings = load_settings()
+    assert settings["settings_updated_at"] == old_ts  # exact match, not "close to now"