From a52708769da675e2ade6cb6fe28e1cd9741c562d Mon Sep 17 00:00:00 2001
From: "Carlos R. L. Rodrigues"
 <37986729+carlos-r-l-rodrigues@users.noreply.github.com>
Date: Wed, 6 Aug 2025 15:49:10 -0300
Subject: [PATCH] chore(util): avoid promotion value precision limit (#13145)

---
 .changeset/clever-deers-shout.md               |  5 +++++
 packages/core/utils/src/totals/math.ts         |  4 ++++
 .../core/utils/src/totals/promotion/index.ts   | 18 ++++++------------
 3 files changed, 15 insertions(+), 12 deletions(-)
 create mode 100644 .changeset/clever-deers-shout.md

diff --git a/.changeset/clever-deers-shout.md b/.changeset/clever-deers-shout.md
new file mode 100644
index 0000000000..a984f66a2e
--- /dev/null
+++ b/.changeset/clever-deers-shout.md
@@ -0,0 +1,5 @@
+---
+"@medusajs/utils": patch
+---
+
+chore(utils): avoid limit precision for promotion value
diff --git a/packages/core/utils/src/totals/math.ts b/packages/core/utils/src/totals/math.ts
index 458ea39102..626ed2db06 100644
--- a/packages/core/utils/src/totals/math.ts
+++ b/packages/core/utils/src/totals/math.ts
@@ -3,6 +3,10 @@ import { BigNumber as BigNumberJS } from "bignumber.js"
 import { isDefined } from "../common"
 import { BigNumber } from "./big-number"
 
+export const MEDUSA_EPSILON = new BigNumber(
+  process.env.MEDUSA_EPSILON || "0.0001"
+)
+
 type BNInput = BigNumberInput | BigNumber
 export class MathBN {
   static convert(num: BNInput, decimalPlaces?: number): BigNumberJS {
diff --git a/packages/core/utils/src/totals/promotion/index.ts b/packages/core/utils/src/totals/promotion/index.ts
index 15d9c5bdff..eabfe0ee6c 100644
--- a/packages/core/utils/src/totals/promotion/index.ts
+++ b/packages/core/utils/src/totals/promotion/index.ts
@@ -3,13 +3,10 @@ import {
   ApplicationMethodAllocation,
   ApplicationMethodType,
 } from "../../promotion"
-import { MathBN } from "../math"
+import { MathBN, MEDUSA_EPSILON } from "../math"
 
 function getPromotionValueForPercentage(promotion, lineItemAmount) {
-  return MathBN.convert(
-    MathBN.mult(MathBN.div(promotion.value, 100), lineItemAmount),
-    2
-  )
+  return MathBN.mult(MathBN.div(promotion.value, 100), lineItemAmount)
 }
 
 function getPromotionValueForFixed(promotion, lineItemAmount, lineItemsAmount) {
@@ -28,10 +25,7 @@ function getPromotionValueForFixed(promotion, lineItemAmount, lineItemsAmount) {
       promotionValueForItem
     )
 
-    return MathBN.convert(
-      MathBN.mult(promotionValueForItem, MathBN.div(percentage, 100)),
-      2
-    )
+    return MathBN.mult(promotionValueForItem, MathBN.div(percentage, 100))
   }
   return promotion.value
 }
@@ -104,8 +98,8 @@ export function calculateAdjustmentAmountFromPromotion(
     )
     const applicableAmount = MathBN.sub(lineItemAmount, promotion.applied_value)
 
-    if (MathBN.lte(applicableAmount, 0)) {
-      return applicableAmount
+    if (MathBN.lte(applicableAmount, MEDUSA_EPSILON)) {
+      return MathBN.convert(0)
     }
 
     const promotionValue = getPromotionValue(
@@ -153,7 +147,7 @@ export function calculateAdjustmentAmountFromPromotion(
     maximumPromotionAmount
   )
 
-  if (MathBN.lte(applicableAmount, 0)) {
+  if (MathBN.lte(applicableAmount, MEDUSA_EPSILON)) {
     return MathBN.convert(0)
   }