fix(multipart): keep abort wired after resolve so a mid-upload disconnect tears down the stream

readMultipart resolves on the file-part header and hands the caller an un-drained
stream, but settle() ran cleanup() and detached the abort listener on that path
too. A client disconnect mid-upload then destroyed nothing — busboy never saw EOF,
the file stream stalled, and the route's `for await` held a request slot until
maxDuration (300s). Re-arm an abort handler scoped to the file stream on resolve,
detached when the stream closes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: TheodoreSpeaks

apps/sim/lib/core/utils/multipart.test.ts

@@ -164,4 +164,40 @@ describe('readMultipart', () => {
       readMultipart(request, { maxFileBytes: 1024, signal: controller.signal })
     ).rejects.toBeTruthy()
   })
+
+  it('destroys the file stream when the signal aborts mid-upload (after resolve)', async () => {
+    const controller = new AbortController()
+    // A body that delivers the file-part header but never closes, so the file stream stays open
+    // after readMultipart resolves — mimicking a client still uploading.
+    let enqueue!: (b: Buffer) => void
+    const body = new ReadableStream<Uint8Array>({
+      start(c) {
+        enqueue = (b) => c.enqueue(new Uint8Array(b))
+      },
+    })
+    const head = Buffer.concat([
+      Buffer.from(
+        `--${BOUNDARY}\r\nContent-Disposition: form-data; name="workspaceId"\r\n\r\nws-1\r\n`
+      ),
+      Buffer.from(
+        `--${BOUNDARY}\r\nContent-Disposition: form-data; name="file"; filename="data.csv"\r\nContent-Type: text/csv\r\n\r\n`
+      ),
+      Buffer.from('name,age\n'),
+    ])
+    const request = {
+      headers: new Headers({ 'content-type': `multipart/form-data; boundary=${BOUNDARY}` }),
+      body,
+    }
+    enqueue(head)
+
+    const parsed = await readMultipart(request, {
+      maxFileBytes: 1024,
+      requiredFieldsBeforeFile: ['workspaceId'],
+      signal: controller.signal,
+    })
+    expect(parsed.file).toBeTruthy()
+
+    controller.abort()
+    await expect(readStream(parsed.file!.stream)).rejects.toBeTruthy()
+  })
 })

apps/sim/lib/core/utils/multipart.ts

@@ -203,12 +203,28 @@ export function readMultipart(
         )
       })
 
-      settle(() =>
+      settle(() => {
+        // settle() detached the pre-file abort handler. Re-arm one scoped to the file stream so a
+        // client disconnect mid-upload tears it down — otherwise the caller's consume loop hangs
+        // until maxDuration. Detach when the stream closes so it can't fire afterward.
+        if (signal) {
+          const onStreamAbort = () => {
+            const reason = signal.reason instanceof Error ? signal.reason : new Error('Aborted')
+            stream.destroy(reason)
+            nodeStream.destroy(reason)
+            bb.destroy()
+          }
+          if (signal.aborted) onStreamAbort()
+          else {
+            signal.addEventListener('abort', onStreamAbort, { once: true })
+            stream.once('close', () => signal.removeEventListener('abort', onStreamAbort))
+          }
+        }
         resolve({
           fields,
           file: { fieldName: name, filename: info.filename, mimeType: info.mimeType, stream },
         })
-      )
+      })
     })
 
     bb.on('error', (err) => {