diff --git a/.server-changes/transcript-download-media-type-case.md b/.server-changes/transcript-download-media-type-case.md
new file mode 100644
index 00000000000..98ededeb7fd
--- /dev/null
+++ b/.server-changes/transcript-download-media-type-case.md
@@ -0,0 +1,6 @@
+---
+area: webapp
+type: fix
+---
+
+Chat transcript downloads keep the .jsonl filename when the stored media type differs only in letter case.
diff --git a/apps/webapp/app/services/realtime/transcriptDownload.server.test.ts b/apps/webapp/app/services/realtime/transcriptDownload.server.test.ts
index 6768b6eb0f1..c4f60960aab 100644
--- a/apps/webapp/app/services/realtime/transcriptDownload.server.test.ts
+++ b/apps/webapp/app/services/realtime/transcriptDownload.server.test.ts
@@ -103,6 +103,22 @@ minioTest(
   }
 );
 
+test("uses a .jsonl filename for transcript media types regardless of case", () => {
+  for (const contentType of [
+    TRANSCRIPT_BLOB_CONTENT_TYPE.toUpperCase(),
+    "Application/Vnd.Trigger.Transcript+Ndjson; charset=utf-8",
+  ]) {
+    const object = new Response('{"version":2}\n', {
+      headers: { "Content-Type": contentType },
+    });
+    const response = downloadTranscript(object, "packets/download/snapshot.json");
+    expect(response.headers.get("Content-Disposition")).toBe(
+      'attachment; filename="snapshot.jsonl"'
+    );
+    expect(response.headers.get("Content-Type")).toBe(contentType);
+  }
+});
+
 test("does not treat permission or service failures as an absent transcript", () => {
   expect(isTranscriptNotFound(new Error("Failed to download from object store: Forbidden"))).toBe(
     false
diff --git a/apps/webapp/app/services/realtime/transcriptDownload.server.ts b/apps/webapp/app/services/realtime/transcriptDownload.server.ts
index da477a9ca5a..cee932b690b 100644
--- a/apps/webapp/app/services/realtime/transcriptDownload.server.ts
+++ b/apps/webapp/app/services/realtime/transcriptDownload.server.ts
@@ -9,8 +9,9 @@ export function downloadTranscript(
 ): Response {
   const storedFilename = basename(storagePath).replace(/[^a-zA-Z0-9._-]/g, "_") || "transcript";
   const contentType = object.headers.get("Content-Type") ?? "application/octet-stream";
+  // Media type and subtype are case-insensitive (RFC 9110). Parameters after ";" are ignored.
   const filename =
-    contentType.split(";")[0]?.trim() === TRANSCRIPT_BLOB_CONTENT_TYPE
+    contentType.split(";")[0]?.trim().toLowerCase() === TRANSCRIPT_BLOB_CONTENT_TYPE
       ? `${basename(storedFilename, extname(storedFilename))}.jsonl`
       : storedFilename;
   // Errors after the route returns must still be logged and reach the HTTP adapter,