diff --git a/messages/en.json b/messages/en.json
index fb617a16..d518349e 100644
--- a/messages/en.json
+++ b/messages/en.json
@@ -24,5 +24,44 @@
 
 	"context_view_details": "View Details",
 	"context_replace": "Replace",
-	"context_remove": "Remove"
+	"context_remove": "Remove",
+
+	"conflict_title": "Conflict Detected",
+	"conflict_character_message": "Only one version of a character can be included in each party. Do you want to replace them?",
+	"conflict_weapon_series": "Only one weapon from the {series} Series can be included in each party. Do you want to replace it?",
+	"conflict_weapon_opus_draconic": "Only one Dark Opus or Draconic Weapon can be included in each party. Do you want to replace it?",
+	"conflict_confirm": "Replace",
+	"conflict_cancel": "Cancel",
+
+	"series_seraphic": "Seraphic",
+	"series_grand": "Grand",
+	"series_opus": "Dark Opus",
+	"series_draconic": "Draconic",
+	"series_revenant": "Revenant",
+	"series_primal": "Primal",
+	"series_beast": "Beast",
+	"series_regalia": "Regalia",
+	"series_omega": "Omega",
+	"series_olden_primal": "Olden Primal",
+	"series_militis": "Militis",
+	"series_hollowsky": "Hollowsky",
+	"series_xeno": "Xeno",
+	"series_astral": "Astral",
+	"series_rose": "Rose",
+	"series_bahamut": "Bahamut",
+	"series_ultima": "Ultima",
+	"series_epic": "Epic",
+	"series_ennead": "Ennead",
+	"series_cosmic": "Cosmic",
+	"series_ancestral": "Ancestral",
+	"series_superlative": "Superlative",
+	"series_vintage": "Vintage",
+	"series_class_champion": "Class Champion",
+	"series_proving": "Proving Grounds",
+	"series_sephira": "Sephira",
+	"series_new_world": "New World",
+	"series_disaster": "Disaster",
+	"series_illustrious": "Illustrious",
+	"series_world": "World",
+	"series_draconic_providence": "Draconic Providence"
 }
diff --git a/messages/ja.json b/messages/ja.json
index 352a912a..a7a2fe59 100644
--- a/messages/ja.json
+++ b/messages/ja.json
@@ -24,5 +24,44 @@
 
 	"context_view_details": "詳細を見る",
 	"context_replace": "交換",
-	"context_remove": "削除"
+	"context_remove": "削除",
+
+	"conflict_title": "コンフリクト検出",
+	"conflict_character_message": "同じ名前のキャラクターがパーティに編成されています。以下のキャラクターを入れ替えますか？",
+	"conflict_weapon_series": "{series}シリーズの武器は１本しか装備できません。以下の武器を入れ替えますか？",
+	"conflict_weapon_opus_draconic": "終末の神器シリーズとドラコニックシリーズから１本しか装備できません。以下の武器を入れ替えますか？",
+	"conflict_confirm": "入れ替える",
+	"conflict_cancel": "キャンセル",
+
+	"series_seraphic": "セラフィック",
+	"series_grand": "リミテッド",
+	"series_opus": "終末の神器",
+	"series_draconic": "ドラゴニック",
+	"series_revenant": "天星器",
+	"series_primal": "マグナ",
+	"series_beast": "四象",
+	"series_regalia": "レガリア",
+	"series_omega": "オメガ",
+	"series_olden_primal": "オールド・プライマル",
+	"series_militis": "ミリティス",
+	"series_hollowsky": "虚空",
+	"series_xeno": "ゼノ",
+	"series_astral": "アストラル",
+	"series_rose": "ローズ",
+	"series_bahamut": "バハムート",
+	"series_ultima": "アルティメット",
+	"series_epic": "エピック",
+	"series_ennead": "エニアド",
+	"series_cosmic": "コスミック",
+	"series_ancestral": "六道",
+	"series_superlative": "スペリオル",
+	"series_vintage": "ヴィンテージ",
+	"series_class_champion": "クラス・チャンピオン",
+	"series_proving": "プロヴィングラウンド",
+	"series_sephira": "セフィラ",
+	"series_new_world": "ニューワールド",
+	"series_disaster": "ディザスター",
+	"series_illustrious": "イラストリアス",
+	"series_world": "ワールド",
+	"series_draconic_providence": "ドラコニック・プロヴィデンス"
 }
diff --git a/src/lib/utils/weaponSeries.ts b/src/lib/utils/weaponSeries.ts
new file mode 100644
index 00000000..cb9efb2f
--- /dev/null
+++ b/src/lib/utils/weaponSeries.ts
@@ -0,0 +1,76 @@
+/**
+ * Weapon Series Utilities
+ *
+ * Provides helpers for weapon series identification and conflict messaging.
+ *
+ * @module utils/weaponSeries
+ */
+
+export interface WeaponSeries {
+	id: number
+	slug: string
+}
+
+/**
+ * All weapon series with their IDs and slugs.
+ * The slug is used for i18n message keys.
+ */
+export const weaponSeries: WeaponSeries[] = [
+	{ id: 0, slug: 'seraphic' },
+	{ id: 1, slug: 'grand' },
+	{ id: 2, slug: 'opus' },
+	{ id: 3, slug: 'draconic' },
+	{ id: 4, slug: 'revenant' },
+	{ id: 6, slug: 'primal' },
+	{ id: 7, slug: 'beast' },
+	{ id: 8, slug: 'regalia' },
+	{ id: 9, slug: 'omega' },
+	{ id: 10, slug: 'olden_primal' },
+	{ id: 11, slug: 'militis' },
+	{ id: 12, slug: 'hollowsky' },
+	{ id: 13, slug: 'xeno' },
+	{ id: 14, slug: 'astral' },
+	{ id: 15, slug: 'rose' },
+	{ id: 16, slug: 'bahamut' },
+	{ id: 17, slug: 'ultima' },
+	{ id: 18, slug: 'epic' },
+	{ id: 19, slug: 'ennead' },
+	{ id: 20, slug: 'cosmic' },
+	{ id: 21, slug: 'ancestral' },
+	{ id: 22, slug: 'superlative' },
+	{ id: 23, slug: 'vintage' },
+	{ id: 24, slug: 'class_champion' },
+	{ id: 25, slug: 'proving' },
+	{ id: 28, slug: 'sephira' },
+	{ id: 29, slug: 'new_world' },
+	{ id: 30, slug: 'disaster' },
+	{ id: 31, slug: 'illustrious' },
+	{ id: 32, slug: 'world' },
+	{ id: 34, slug: 'draconic_providence' }
+]
+
+/**
+ * Series IDs that share the Opus/Draconic conflict rule.
+ * Only one weapon from these series can be in a party at a time.
+ */
+export const OPUS_DRACONIC_SERIES = [2, 3, 34]
+
+/**
+ * Get the slug for a weapon series by ID.
+ *
+ * @param id - The series ID
+ * @returns The series slug or undefined if not found
+ */
+export function getWeaponSeriesSlug(id: number): string | undefined {
+	return weaponSeries.find((s) => s.id === id)?.slug
+}
+
+/**
+ * Check if a series ID belongs to the Opus/Draconic conflict group.
+ *
+ * @param seriesId - The series ID to check
+ * @returns True if the series is Opus, Draconic, or Draconic Providence
+ */
+export function isOpusDraconicSeries(seriesId: number): boolean {
+	return OPUS_DRACONIC_SERIES.includes(seriesId)
+}