diff --git a/packages/bruno-cli/src/runner/interpolate-vars.js b/packages/bruno-cli/src/runner/interpolate-vars.js
index 0b19e0a79..7f76aab14 100644
--- a/packages/bruno-cli/src/runner/interpolate-vars.js
+++ b/packages/bruno-cli/src/runner/interpolate-vars.js
@@ -2,6 +2,8 @@ const { interpolate } = require('@usebruno/common');
 const { each, forOwn, cloneDeep, find } = require('lodash');
 const { isFormData } = require('@usebruno/common').utils;
 
+const isBinaryRequestBody = (data) => Buffer.isBuffer(data) || typeof data?.pipe === 'function';
+
 const getContentType = (headers = {}) => {
   let contentType = '';
   forOwn(headers, (value, key) => {
@@ -80,7 +82,7 @@ const interpolateVars = (request, envVariables = {}, runtimeVariables = {}, proc
 
   // Skip body interpolation for GraphQL requests.
   if (!isGraphqlRequest) {
-    if (contentType.includes('json') && !Buffer.isBuffer(request.data)) {
+    if (contentType.includes('json') && !isBinaryRequestBody(request.data)) {
       if (typeof request.data === 'string') {
         if (request?.data?.length) {
           request.data = _interpolate(request.data, { escapeJSONStrings: true });
diff --git a/packages/bruno-cli/tests/runner/interpolate-vars.spec.js b/packages/bruno-cli/tests/runner/interpolate-vars.spec.js
index 7349b5bdd..0ffa29eb7 100644
--- a/packages/bruno-cli/tests/runner/interpolate-vars.spec.js
+++ b/packages/bruno-cli/tests/runner/interpolate-vars.spec.js
@@ -1,6 +1,25 @@
 const { describe, it, expect } = require('@jest/globals');
 const interpolateVars = require('../../src/runner/interpolate-vars');
 
+describe('interpolate-vars: interpolateVars', () => {
+  it('keeps stream-backed JSON request bodies intact', () => {
+    const streamPayload = {
+      pipe: jest.fn(),
+      path: '/tmp/allocations.json'
+    };
+    const request = {
+      method: 'POST',
+      mode: 'file',
+      url: 'http://api.example/upload',
+      headers: { 'content-type': 'application/json' },
+      data: streamPayload
+    };
+
+    const result = interpolateVars(request, { shouldNotApply: 'value' }, null, null);
+    expect(result.data).toBe(streamPayload);
+   });
+});
+
 describe('interpolate-vars: api key header name sidecar', () => {
   it('interpolates apiKeyHeaderName in lockstep with interpolated header keys', () => {
     const request = {
diff --git a/packages/bruno-electron/src/ipc/network/interpolate-vars.js b/packages/bruno-electron/src/ipc/network/interpolate-vars.js
index a90cc74a5..81e170e5d 100644
--- a/packages/bruno-electron/src/ipc/network/interpolate-vars.js
+++ b/packages/bruno-electron/src/ipc/network/interpolate-vars.js
@@ -2,6 +2,8 @@ const { interpolate } = require('@usebruno/common');
 const { each, forOwn, cloneDeep } = require('lodash');
 const { isFormData } = require('@usebruno/common').utils;
 
+const isBinaryRequestBody = (data) => Buffer.isBuffer(data) || typeof data?.pipe === 'function';
+
 const getContentType = (headers = {}) => {
   let contentType = '';
   forOwn(headers, (value, key) => {
@@ -110,10 +112,11 @@ const interpolateVars = (request, envVariables = {}, runtimeVariables = {}, proc
 
   if (typeof contentType === 'string' && !isGraphqlRequest) {
     /*
-      We explicitly avoid interpolating buffer values because the file content is read as a buffer object in raw body mode.
-      Even if the selected file's content type is JSON, this prevents the buffer object from being interpolated.
+      We explicitly avoid interpolating binary payloads because raw file bodies can be represented as
+      buffers or streams depending on size. Even if the selected file's content type is JSON, the
+      transport object itself must not be interpolated.
     */
-    if (contentType.includes('json') && !Buffer.isBuffer(request.data)) {
+    if (contentType.includes('json') && !isBinaryRequestBody(request.data)) {
       if (typeof request.data === 'string') {
         if (request.data.length) {
           request.data = _interpolate(request.data, {
diff --git a/packages/bruno-electron/tests/network/interpolate-vars.spec.js b/packages/bruno-electron/tests/network/interpolate-vars.spec.js
index 2eea40a93..48e1a9f9d 100644
--- a/packages/bruno-electron/tests/network/interpolate-vars.spec.js
+++ b/packages/bruno-electron/tests/network/interpolate-vars.spec.js
@@ -426,4 +426,24 @@ describe('interpolate-vars: interpolateVars', () => {
       expect(result.data).toContain('--TestBoundary123--');
     });
   });
+
+  describe('File body streaming', () => {
+    it('keeps stream-backed JSON request bodies intact', () => {
+      const streamPayload = {
+        pipe: jest.fn(),
+        path: '/tmp/allocations.json'
+      };
+      const request = {
+        method: 'POST',
+        mode: 'file',
+        url: 'http://api.example/upload',
+        headers: { 'content-type': 'application/json' },
+        data: streamPayload
+      };
+
+      const result = interpolateVars(request, { shouldNotApply: 'value' }, null, null);
+
+      expect(result.data).toBe(streamPayload);
+    });
+  });
 });