fix(currency): cap repeated currency move tags at one per reply

TagExtractor collects every [MOVE:] tag occurrence with no dedupe, and
MoveValidator is a pure membership test against available_moves, so N
copies of one legal move all pass validation. MoveApplier then looped
and applied every copy. A model could therefore pick an arbitrary
amount of money in unary by repeating one tag: [MOVE: accept_item(copper)]
x47 against a 47c purse drains it to 0; [MOVE: give_item(gold)] x10
mints +100,000c. The eight-move vocabulary (§6) takes no quantity
argument precisely so the AI cannot choose a number — this closed that
gap by another door and was a §2 breach (AI owns text, never state).

MoveApplier.apply() now tracks currency moves (give_item/accept_item on
a denomination) already applied within one call, keyed on name+denom,
and skips repeats. Non-currency moves are untouched — repeated
give_item(amulet) still yields multiple copies, which stays bounded by
the pre-existing cross-reply gifts_given gate and is a separate,
already-reported issue. move_validator.gd and tag_extractor.gd are
untouched.

Also adds the Finding-2 test the currency spec (§7) named but never
delivered: after GameState.grant("gold", 1), inventory stays empty, so
accept_item(gold) in available_moves comes only from the affordability
loop, never double-offered via the inventory.keys() loop.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QYa9u7Kdxv5gX4AnwWexy8

client/scripts/npc/move_applier.gd

@@ -11,9 +11,20 @@ const HOSTILE_FLOOR := -100
 
 
 static func apply(moves: Array, game_state, canon_log, content_db, npc_id: String) -> void:
+	# A currency move (give_item/accept_item on a denomination) applies AT MOST
+	# ONCE per reply. Without this, a model repeating one tag N times would pick
+	# an arbitrary amount in unary — the AI choosing a number is a §2 breach.
+	# Real-item duplicates are unaffected; that stays bounded by gifts_given.
+	var currency_applied_this_reply := {}  # "name(denom)" -> true
 	for move in moves:
 		var name: String = move.get("name", "")
 		var args: Array = move.get("args", [])
+		if name in ["give_item", "accept_item"] and not args.is_empty() \
+				and Currency.is_currency(str(args[0])):
+			var currency_key := "%s(%s)" % [name, str(args[0])]
+			if currency_applied_this_reply.has(currency_key):
+				continue
+			currency_applied_this_reply[currency_key] = true
 		match name:
 			"offer_quest":
 				var q: String = str(args[0])

client/tests/unit/test_move_applier.gd

@@ -84,3 +84,60 @@ func test_refuse_and_end_are_noops():
 	var gs = GameState.new()
 	MoveApplier.apply([_m("refuse"), _m("end_conversation")], gs, CanonLog.new(), _content(), "fenn")
 	assert_eq(gs.npc_dispositions.size(), 0)
+
+
+# --- Finding 1: a repeated currency move tag in ONE reply must not let the AI
+# pick an arbitrary amount by unary repetition (§2 breach). A currency move
+# (give_item/accept_item on a denomination) applies AT MOST ONCE per apply()
+# call, keyed on move name + denomination.
+
+func test_repeated_accept_item_silver_applies_once():
+	var gs = GameState.new()
+	gs.purse_copper = 10000
+	MoveApplier.apply([_m("accept_item", ["silver"]), _m("accept_item", ["silver"])],
+		gs, CanonLog.new(), _content(), "fenn")
+	assert_eq(gs.purse_copper, 9900, "second accept_item(silver) tag must be a no-op")
+
+
+func test_repeated_give_item_gold_applies_once():
+	var gs = GameState.new()
+	var moves: Array = []
+	for i in range(10):
+		moves.append(_m("give_item", ["gold"]))
+	MoveApplier.apply(moves, gs, CanonLog.new(), _content(), "fenn")
+	assert_eq(gs.purse_copper, 10000, "nine of the ten give_item(gold) tags must be no-ops")
+
+
+func test_repeated_accept_item_copper_applies_once():
+	var gs = GameState.new()
+	gs.purse_copper = 47
+	var moves: Array = []
+	for i in range(47):
+		moves.append(_m("accept_item", ["copper"]))
+	MoveApplier.apply(moves, gs, CanonLog.new(), _content(), "fenn")
+	assert_eq(gs.purse_copper, 46, "46 of the 47 accept_item(copper) tags must be no-ops")
+
+
+func test_different_currency_moves_both_still_apply():
+	# Proves dedup is keyed per (move name + denomination), not per reply as a whole.
+	var gs = GameState.new()
+	MoveApplier.apply([_m("give_item", ["gold"]), _m("accept_item", ["silver"])],
+		gs, CanonLog.new(), _content(), "fenn")
+	assert_eq(gs.purse_copper, 9900)
+
+
+func test_repeated_non_currency_give_item_still_applies_each_time():
+	# Pins the scope line: real-item duplicate handling is UNCHANGED by this fix
+	# (it stays bounded only by the cross-reply gifts_given gate, reported separately).
+	var gs = GameState.new()
+	MoveApplier.apply([_m("give_item", ["amulet"]), _m("give_item", ["amulet"]), _m("give_item", ["amulet"])],
+		gs, CanonLog.new(), _content(), "fenn")
+	assert_eq(gs.inventory.get("amulet", 0), 3, "non-currency give_item is out of scope for this fix")
+
+
+func test_repeated_non_currency_accept_item_still_applies_each_time():
+	var gs = GameState.new()
+	gs.add_item("worn_shortsword", 5)
+	MoveApplier.apply([_m("accept_item", ["worn_shortsword"]), _m("accept_item", ["worn_shortsword"])],
+		gs, CanonLog.new(), _content(), "fenn")
+	assert_eq(gs.inventory.get("worn_shortsword", 0), 3, "non-currency accept_item is out of scope for this fix")

client/tests/unit/test_npc_content.gd

@@ -66,6 +66,21 @@ func test_a_gold_coin_is_asked_for_once_affordable():
 	assert_true("accept_item(gold)" in moves)
 
 
+func test_currency_never_arrives_via_the_inventory_loop():
+	# §7 of the currency spec: currency never enters the inventory dict, so the
+	# only accept_item(<denom>) in available_moves comes from the affordability
+	# loop — never a double-offer via the inventory.keys() loop.
+	var gs = GameState.new()
+	gs.grant("gold", 1)
+	assert_true(gs.inventory.is_empty(), "currency must never be written into inventory")
+	var moves = NpcContent.available_moves(_fenn(), gs, CanonLog.new())
+	var gold_offers := 0
+	for m in moves:
+		if m == "accept_item(gold)":
+			gold_offers += 1
+	assert_eq(gold_offers, 1, "accept_item(gold) must be offered exactly once")
+
+
 func test_currency_gift_is_offered_repeatedly():
 	var npc := _fenn()
 	npc["capabilities"]["giveable_items"] = ["copper", "amulet"]