diff --git a/src/controllers/api/valenceSwapController.ts b/src/controllers/api/valenceSwapController.ts
new file mode 100644
index 00000000..6196c9f1
--- /dev/null
+++ b/src/controllers/api/valenceSwapController.ts
@@ -0,0 +1,37 @@
+import { getInventory } from "@/src/services/inventoryService";
+import { getAccountIdForRequest } from "@/src/services/loginService";
+import { IOid } from "@/src/types/commonTypes";
+import { TEquipmentKey } from "@/src/types/inventoryTypes/inventoryTypes";
+import { RequestHandler } from "express";
+
+export const valenceSwapController: RequestHandler = async (req, res) => {
+    const accountId = await getAccountIdForRequest(req);
+    const body = JSON.parse(String(req.body)) as IValenceSwapRequest;
+    const inventory = await getInventory(accountId, body.WeaponCategory);
+    const weapon = inventory[body.WeaponCategory].id(body.WeaponId.$oid)!;
+
+    const upgradeFingerprint = JSON.parse(weapon.UpgradeFingerprint!) as IInnateDamageFingerprint;
+    upgradeFingerprint.buffs[0].Tag = body.NewValenceUpgradeTag;
+    weapon.UpgradeFingerprint = JSON.stringify(upgradeFingerprint);
+
+    await inventory.save();
+    res.json({
+        InventoryChanges: {
+            [body.WeaponCategory]: [weapon.toJSON()]
+        }
+    });
+};
+
+interface IValenceSwapRequest {
+    WeaponId: IOid;
+    WeaponCategory: TEquipmentKey;
+    NewValenceUpgradeTag: string;
+}
+
+interface IInnateDamageFingerprint {
+    compat: string;
+    buffs: {
+        Tag: string;
+        Value: number;
+    }[];
+}
diff --git a/src/routes/api.ts b/src/routes/api.ts
index b2ef011d..15a6d32e 100644
--- a/src/routes/api.ts
+++ b/src/routes/api.ts
@@ -113,6 +113,7 @@ import { updateSessionGetController, updateSessionPostController } from "@/src/c
 import { updateSongChallengeController } from "@/src/controllers/api/updateSongChallengeController";
 import { updateThemeController } from "@/src/controllers/api/updateThemeController";
 import { upgradesController } from "@/src/controllers/api/upgradesController";
+import { valenceSwapController } from "@/src/controllers/api/valenceSwapController";
 
 const apiRouter = express.Router();
 
@@ -241,5 +242,6 @@ apiRouter.post("/updateSession.php", updateSessionPostController);
 apiRouter.post("/updateSongChallenge.php", updateSongChallengeController);
 apiRouter.post("/updateTheme.php", updateThemeController);
 apiRouter.post("/upgrades.php", upgradesController);
+apiRouter.post("/valenceSwap.php", valenceSwapController);
 
 export { apiRouter };