diff --git a/artifacts/api-server/src/routes/costs.ts b/artifacts/api-server/src/routes/costs.ts
index 56f1617..e054f26 100644
--- a/artifacts/api-server/src/routes/costs.ts
+++ b/artifacts/api-server/src/routes/costs.ts
@@ -91,6 +91,11 @@ router.patch("/costs/:id", requireAuth, requireFeature("costs"), async (req, res
   if (currency !== undefined) updateData.currency = currency;
   if (notes !== undefined) updateData.notes = notes;
 
+  if (Object.keys(updateData).length === 0) {
+    res.json(existing);
+    return;
+  }
+
   const [updated] = await db.update(toolCostsTable).set(updateData).where(eq(toolCostsTable.id, id)).returning();
   await writeAuditLog(req, "tool_cost", id, "update", { toolId: existing.toolId, ...updateData });
   res.json(updated);