diff --git a/packages/components/src/utils.test.ts b/packages/components/src/utils.test.ts
index ba8238ee049..32529f10fdc 100644
--- a/packages/components/src/utils.test.ts
+++ b/packages/components/src/utils.test.ts
@@ -1,4 +1,10 @@
-import { removeInvalidImageMarkdown, convertRequireToImport, COMMONJS_REQUIRE_REGEX, IMPORT_EXTRACTION_REGEX } from './utils'
+import {
+    removeInvalidImageMarkdown,
+    convertRequireToImport,
+    COMMONJS_REQUIRE_REGEX,
+    IMPORT_EXTRACTION_REGEX,
+    mapExtToInputField
+} from './utils'
 
 describe('removeInvalidImageMarkdown', () => {
     describe('strips non-http/https image markdown', () => {
@@ -229,3 +235,35 @@ describe('Import extraction regex (utils.ts line 1596 pattern)', () => {
         expect(extractModules('console.log("hello")')).toEqual([])
     })
 })
+
+describe('mapExtToInputField', () => {
+    it('maps known lowercase extensions to their input field', () => {
+        expect(mapExtToInputField('.pdf')).toBe('pdfFile')
+        expect(mapExtToInputField('.txt')).toBe('txtFile')
+        expect(mapExtToInputField('.json')).toBe('jsonFile')
+        expect(mapExtToInputField('.csv')).toBe('csvFile')
+        expect(mapExtToInputField('.docx')).toBe('docxFile')
+    })
+
+    it('maps uppercase extensions to the same input field (case-insensitive)', () => {
+        expect(mapExtToInputField('.PDF')).toBe('pdfFile')
+        expect(mapExtToInputField('.TXT')).toBe('txtFile')
+        expect(mapExtToInputField('.JSON')).toBe('jsonFile')
+        expect(mapExtToInputField('.DOCX')).toBe('docxFile')
+    })
+
+    it('maps mixed-case extensions to the same input field', () => {
+        expect(mapExtToInputField('.Pdf')).toBe('pdfFile')
+        expect(mapExtToInputField('.Csv')).toBe('csvFile')
+    })
+
+    it('falls back to txtFile for unknown extensions', () => {
+        expect(mapExtToInputField('.unknown')).toBe('txtFile')
+    })
+
+    it('falls back to txtFile for empty or nullish extensions', () => {
+        expect(mapExtToInputField('')).toBe('txtFile')
+        expect(mapExtToInputField(undefined)).toBe('txtFile')
+        expect(mapExtToInputField(null as unknown as string)).toBe('txtFile')
+    })
+})
diff --git a/packages/components/src/utils.ts b/packages/components/src/utils.ts
index c89210a59f5..da7a58f9da5 100644
--- a/packages/components/src/utils.ts
+++ b/packages/components/src/utils.ts
@@ -1068,11 +1068,11 @@ export const getVersion: () => Promise<{ version: string }> = async () => {
 
 /**
  * Map Ext to InputField
- * @param {string} ext
+ * @param {string} [ext] File extension (case-insensitive), e.g. ".pdf"
  * @returns {string}
  */
-export const mapExtToInputField = (ext: string) => {
-    switch (ext) {
+export const mapExtToInputField = (ext?: string) => {
+    switch (ext?.toLowerCase()) {
         case '.txt':
             return 'txtFile'
         case '.pdf':
diff --git a/packages/server/src/utils/createAttachment.ts b/packages/server/src/utils/createAttachment.ts
index 2daec1e2e1d..2cc759c2bf2 100644
--- a/packages/server/src/utils/createAttachment.ts
+++ b/packages/server/src/utils/createAttachment.ts
@@ -177,7 +177,7 @@ export const createFileAttachment = async (req: Request) => {
             if (fileInputFieldFromExt !== 'txtFile') {
                 fileInputField = fileInputFieldFromExt
             } else if (fileInputFieldFromMimeType !== 'txtFile') {
-                fileInputField = fileInputFieldFromExt
+                fileInputField = fileInputFieldFromMimeType
             }
 
             await removeSpecificFileFromUpload(file.path ?? file.key)