platforms/eCurrency-api/src/database/entities/Currency.ts (1)

39-40: TypeORM decimal columns return strings at runtime.

TypeORM's decimal type returns values as strings, not JavaScript numbers. The TypeScript type number | null is misleading and may cause subtle bugs when performing arithmetic or comparisons without explicit conversion.

Consider adjusting the type or using a transformer:

-    @Column("decimal", { precision: 18, scale: 2, nullable: true })
-    maxNegativeBalance!: number | null;
+    @Column("decimal", { precision: 18, scale: 2, nullable: true, transformer: {
+        to: (value: number | null) => value,
+        from: (value: string | null) => value === null ? null : parseFloat(value)
+    }})
+    maxNegativeBalance!: number | null;

Alternatively, update the type to string | null and convert explicitly at usage sites.

platforms/eCurrency-api/src/controllers/CurrencyController.ts (1)

162-166: Consider adding semantic validation for maxNegativeBalance.

The current validation only checks that the value is a valid number (or null). Given the semantic meaning (a floor for how negative a balance can go), consider validating that non-null values are <= 0:

             // Allow null to clear; otherwise must be a number
             const parsedValue = value === null || value === undefined ? null : Number(value);
             if (parsedValue !== null && Number.isNaN(parsedValue)) {
                 return res.status(400).json({ error: "Invalid value for maxNegativeBalance" });
             }
+            if (parsedValue !== null && parsedValue > 0) {
+                return res.status(400).json({ error: "maxNegativeBalance must be zero or negative" });
+            }

platforms/eCurrency-api/src/services/CurrencyService.ts (1)

20-47: Align createCurrency maxNegativeBalance invariants with update path

createCurrency now accepts and persists maxNegativeBalance but does not enforce the same constraints you added in updateMaxNegativeBalance (must only be set when allowNegative is true, must be null or <= 0, not NaN). That means callers can create a currency in a state that the update path would later reject (e.g. allowNegative = false with a non‑null cap, or a positive cap).

To keep invariants consistent and avoid surprising states, consider normalizing and validating here as well, e.g.:

     // Generate eName (UUID with @ prefix)
     const ename = `@${uuidv4()}`;
 
+    const normalizedMaxNegativeBalance =
+        allowNegative && maxNegativeBalance !== null ? maxNegativeBalance : null;
+
+    if (normalizedMaxNegativeBalance !== null) {
+        if (Number.isNaN(normalizedMaxNegativeBalance)) {
+            throw new Error("Invalid max negative balance value");
+        }
+        if (normalizedMaxNegativeBalance > 0) {
+            throw new Error("Max negative balance must be zero or negative");
+        }
+    }
+
     const currency = this.currencyRepository.create({
         name,
         description,
         ename,
         groupId,
         createdBy,
         allowNegative,
-        maxNegativeBalance,
+        maxNegativeBalance: normalizedMaxNegativeBalance,
     });

platforms/eCurrency/client/src/pages/currency-detail.tsx (1)

292-301: Optional: Format maxNegativeBalance consistently with other monetary values

Here you display maxNegativeBalance with a bare toLocaleString(), while balance and total supply are formatted with two decimal places. For consistency and readability (especially since the DB column is decimal with scale), consider aligning the formatting:

-                  {currency.allowNegative
-                    ? (currency.maxNegativeBalance !== null && currency.maxNegativeBalance !== undefined
-                      ? Number(currency.maxNegativeBalance).toLocaleString()
-                      : "No cap")
-                    : "Not applicable"}
+                  {currency.allowNegative
+                    ? (currency.maxNegativeBalance !== null && currency.maxNegativeBalance !== undefined
+                      ? Number(currency.maxNegativeBalance).toLocaleString(undefined, {
+                          minimumFractionDigits: 2,
+                          maximumFractionDigits: 2,
+                        })
+                      : "No cap")
+                    : "Not applicable"}

Not required for correctness, but it keeps the UI consistent with the way balances and total supply are shown.

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