From ab540347bec07a7488791320f6763ae1684fe366 Mon Sep 17 00:00:00 2001
From: eliotschu <eliotschu@gmail.com>
Date: Sat, 6 Dec 2025 15:00:21 -0600
Subject: [PATCH] fix: handle FormData body type correctly in RetryAgent
 retried requests

---
 lib/core/util.js   |  2 ++
 test/issue-4691.js | 71 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)
 create mode 100644 test/issue-4691.js

diff --git a/lib/core/util.js b/lib/core/util.js
index fd5b0dfaafb..abfa156f153 100644
--- a/lib/core/util.js
+++ b/lib/core/util.js
@@ -58,6 +58,8 @@ function wrapRequestBody (body) {
     // to determine whether or not it has been disturbed. This is just
     // a workaround.
     return new BodyAsyncIterable(body)
+  } else if (body && isFormDataLike(body)) {
+    return body
   } else if (
     body &&
     typeof body !== 'string' &&
diff --git a/test/issue-4691.js b/test/issue-4691.js
new file mode 100644
index 00000000000..3bd936f2312
--- /dev/null
+++ b/test/issue-4691.js
@@ -0,0 +1,71 @@
+'use strict'
+
+const { tspl } = require('@matteo.collina/tspl')
+const { test, after } = require('node:test')
+const { createServer } = require('node:http')
+const { once } = require('node:events')
+
+const { RetryAgent, Client, FormData } = require('..')
+// https://github.com/nodejs/undici/issues/4691
+test('Should retry status code with FormData body', async t => {
+  t = tspl(t, { plan: 2 })
+
+  let counter = 0
+  const server = createServer({ joinDuplicateHeaders: true })
+  const opts = {
+    maxRetries: 5,
+    timeout: 1,
+    timeoutFactor: 1
+  }
+
+  server.on('request', (req, res) => {
+    switch (counter++) {
+      case 0:
+        req.destroy()
+        return
+      case 1:
+        res.writeHead(500)
+        res.end('failed')
+        return
+      case 2:
+        res.writeHead(200)
+        res.end('hello world!')
+        return
+      default:
+        t.fail()
+    }
+  })
+
+  server.listen(0, () => {
+    const client = new Client(`http://localhost:${server.address().port}`)
+    const agent = new RetryAgent(client, opts)
+
+    after(async () => {
+      await agent.close()
+      server.close()
+
+      await once(server, 'close')
+    })
+
+    const formData = new FormData()
+    formData.append('field', 'test string')
+    agent.request({
+      method: 'GET',
+      path: '/',
+      headers: {
+        'content-type': 'application/json'
+      },
+      body: formData
+    }).then((res) => {
+      t.equal(res.statusCode, 200)
+      res.body.setEncoding('utf8')
+      let chunks = ''
+      res.body.on('data', chunk => { chunks += chunk })
+      res.body.on('end', () => {
+        t.equal(chunks, 'hello world!')
+      })
+    })
+  })
+
+  await t.completed
+})