diff --git a/client/scripts/cooldown_state.gd b/client/scripts/cooldown_state.gd
index 9fc96f0..d52f93a 100644
--- a/client/scripts/cooldown_state.gd
+++ b/client/scripts/cooldown_state.gd
@@ -4,6 +4,8 @@ extends RefCounted
 ## Uses [code]serverTimeUtc[/code] + receive tick to approximate server "now" between polls.
 
 const SLOT_COUNT: int = 8
+## Reject bogus [method Time.get_unix_time_from_datetime_string] results (failed parse → 0).
+const MIN_VALID_UNIX_ANCHOR: float = 1_000_000_000.0
 
 var _slot_end_unix: PackedFloat64Array = PackedFloat64Array()
 var _server_unix_at_receive: float = 0.0
@@ -19,11 +21,19 @@ func _init() -> void:
 func apply_snapshot(snapshot: Dictionary) -> void:
 	for i in range(SLOT_COUNT):
 		_slot_end_unix[i] = 0.0
-	var st: Variant = snapshot.get("serverTimeUtc", "")
+	var st: Variant = snapshot.get("serverTimeUtc", null)
+	var anchor: float = 0.0
 	if st is String:
-		var su: String = st as String
+		var su: String = (st as String).strip_edges()
 		if not su.is_empty():
-			_server_unix_at_receive = Time.get_unix_time_from_datetime_string(su)
+			anchor = Time.get_unix_time_from_datetime_string(su)
+	elif st is float:
+		anchor = st as float
+	elif st is int:
+		anchor = float(st as int)
+	if anchor < MIN_VALID_UNIX_ANCHOR:
+		anchor = Time.get_unix_time_from_system()
+	_server_unix_at_receive = anchor
 	_ticks_msec_at_receive = Time.get_ticks_msec()
 	var slots: Variant = snapshot.get("slots", [])
 	if slots is Array:
@@ -36,8 +46,10 @@ func apply_snapshot(snapshot: Dictionary) -> void:
 				continue
 			var end_v: Variant = d.get("cooldownEndsAtUtc", null)
 			if end_v is String and not (end_v as String).is_empty():
-				var end_s: String = end_v as String
-				_slot_end_unix[idx] = Time.get_unix_time_from_datetime_string(end_s)
+				var end_s: String = (end_v as String).strip_edges()
+				var end_unix: float = Time.get_unix_time_from_datetime_string(end_s)
+				if end_unix >= MIN_VALID_UNIX_ANCHOR:
+					_slot_end_unix[idx] = end_unix
 
 
 func _effective_server_unix() -> float:
diff --git a/client/scripts/main.gd b/client/scripts/main.gd
index 26fc43e..08ac2e4 100644
--- a/client/scripts/main.gd
+++ b/client/scripts/main.gd
@@ -149,7 +149,7 @@ func _physics_process(_delta: float) -> void:
 	var p: Vector3 = _player.global_position
 	_player_pos_label.text = _build_player_position_text(p)
 	_render_target_lock_label(p)
-	if is_instance_valid(_cooldown_state) and _cooldown_state.has_method("any_slot_cooling"):
+	if _cooldown_state != null and _cooldown_state.has_method("any_slot_cooling"):
 		if bool(_cooldown_state.call("any_slot_cooling")):
 			_render_cooldown_slots_label()
 
@@ -317,7 +317,7 @@ func _on_cooldown_poll_timeout() -> void:
 
 
 func _on_cooldown_snapshot_received(snapshot: Dictionary) -> void:
-	if not is_instance_valid(_cooldown_state) or not _cooldown_state.has_method("apply_snapshot"):
+	if _cooldown_state == null or not _cooldown_state.has_method("apply_snapshot"):
 		return
 	_cooldown_state.call("apply_snapshot", snapshot)
 	_render_cooldown_slots_label()
@@ -334,7 +334,7 @@ func _on_cooldown_snapshot_received(snapshot: Dictionary) -> void:
 func _render_cooldown_slots_label() -> void:
 	if not is_instance_valid(_cooldown_slots_label):
 		return
-	if not is_instance_valid(_cooldown_state) or not _cooldown_state.has_method("build_hud_line"):
+	if _cooldown_state == null or not _cooldown_state.has_method("build_hud_line"):
 		return
 	var line: Variant = _cooldown_state.call("build_hud_line")
 	if line is String:
@@ -466,7 +466,7 @@ func _request_hotbar_cast_slot(slot_index: int) -> void:
 	var ability_id: String = outcome[HotbarCastSlotResolver.KEY_ABILITY_ID] as String
 	var resolved_slot: int = int(outcome.get(HotbarCastSlotResolver.KEY_SLOT_INDEX, slot_index))
 	var target_id: Variant = outcome.get(HotbarCastSlotResolver.KEY_TARGET_ID, null)
-	if is_instance_valid(_cooldown_state) and _cooldown_state.has_method("is_slot_cooling"):
+	if _cooldown_state != null and _cooldown_state.has_method("is_slot_cooling"):
 		if bool(_cooldown_state.call("is_slot_cooling", resolved_slot)):
 			if is_instance_valid(_cast_feedback_label):
 				_cast_feedback_label.text = "ability_cast_denied: %s (client guard)" % COOLDOWN_REASON_ON_CD
diff --git a/client/test/cooldown_state_test.gd b/client/test/cooldown_state_test.gd
index 75a901e..c23133b 100644
--- a/client/test/cooldown_state_test.gd
+++ b/client/test/cooldown_state_test.gd
@@ -34,3 +34,16 @@ func test_remaining_positive_when_end_after_server_time() -> void:
 	# Assert
 	assert_that(rem).is_greater(9.0)
 	assert_that(rem).is_less(11.0)
+
+
+func test_invalid_server_time_string_does_not_lock_slot_ready() -> void:
+	# Arrange: bogus ISO would parse as 0 in Godot; anchor must fall back so slot 0 is not stuck cooling.
+	var state: RefCounted = CooldownStateScript.new()
+	var snap := {"serverTimeUtc": "__not_iso__", "slots": [{"slotIndex": 0}]}
+
+	# Act
+	state.call("apply_snapshot", snap)
+	var cooling: bool = bool(state.call("is_slot_cooling", 0))
+
+	# Assert
+	assert_that(cooling).is_false()