diff --git a/mcp/tools/write-tools.ts b/mcp/tools/write-tools.ts
index c0aa0b8b..8c9ccb14 100644
--- a/mcp/tools/write-tools.ts
+++ b/mcp/tools/write-tools.ts
@@ -16,6 +16,7 @@ import {
   canActorSendShippingUpdate,
   canActorUpdateMcpOrderStatus,
 } from "./order-status-auth";
+import type { BinaryLike } from "node:crypto";
 import {
   buildDiscountCodeCreateProof,
   buildDiscountCodeDeleteProof,
@@ -2421,9 +2422,10 @@ export function registerWriteTools(server: McpServer, apiKey: ApiKeyRecord) {
 
       try {
         const fileBuffer = Buffer.from(params.fileBase64, "base64");
-        const { createHash: cryptoCreateHash } = await import("crypto");
+        const binaryData: BinaryLike = new Uint8Array(fileBuffer.buffer, fileBuffer.byteOffset, fileBuffer.byteLength);
+        const { createHash: cryptoCreateHash } = await import("node:crypto");
         const hash = cryptoCreateHash("sha256")
-          .update(fileBuffer)
+          .update(binaryData)
           .digest("hex");
 
         const authEvent: EventTemplate = {
@@ -2433,7 +2435,7 @@ export function registerWriteTools(server: McpServer, apiKey: ApiKeyRecord) {
           tags: [
             ["t", "upload"],
             ["x", hash],
-            ["size", fileBuffer.length.toString()],
+            ["size", binaryData.length.toString()],
             [
               "expiration",
               Math.floor((Date.now() + 24 * 60 * 60 * 1000) / 1000).toString(),
@@ -2476,7 +2478,7 @@ export function registerWriteTools(server: McpServer, apiKey: ApiKeyRecord) {
           {
             url: result.url,
             sha256: result.sha256 || hash,
-            size: result.size || fileBuffer.length,
+            size: result.size || binaryData.length,
             serverUrl,
           },
           startTime