fix: preserve Telegram local Bot API MIME types (#54603) (thanks @jzakirov)

* fix(telegram): preserve content type for local Bot API media files

* fix: preserve Telegram local Bot API MIME types (#54603) (thanks @jzakirov)

---------

Co-authored-by: Ayaan Zaidi <hi@obviy.us>

CHANGELOG.md

@@ -9,6 +9,10 @@ Docs: https://docs.openclaw.ai
 - Agents/compaction: resolve `agents.defaults.compaction.model` consistently for manual `/compact` and other context-engine compaction paths, so engine-owned compaction uses the configured override model across runtime entrypoints. (#56710) Thanks @oliviareid-svg
 - Channels/session routing: move provider-specific session conversation grammar into plugin-owned session-key surfaces, preserving Telegram topic routing and Feishu scoped inheritance across bootstrap, model override, restart, and tool-policy paths.
 
+### Fixes
+
+- Telegram/local Bot API: preserve media MIME types for absolute-path downloads so local audio files still trigger transcription and other MIME-based handling. (#54603) Thanks @jzakirov
+
 ## 2026.3.31
 
 ### Breaking

extensions/telegram/src/bot/delivery.resolve-media-retry.test.ts

@@ -40,7 +40,7 @@ const BOT_TOKEN = "tok123";
 function makeCtx(
   mediaField: "voice" | "audio" | "photo" | "video" | "document" | "animation" | "sticker",
   getFile: TelegramContext["getFile"],
-  opts?: { file_name?: string },
+  opts?: { file_name?: string; mime_type?: string },
 ): TelegramContext {
   const msg: Record<string, unknown> = {
     message_id: 1,
@@ -48,7 +48,12 @@ function makeCtx(
     chat: { id: 1, type: "private" },
   };
   if (mediaField === "voice") {
-    msg.voice = { file_id: "v1", duration: 5, file_unique_id: "u1" };
+    msg.voice = {
+      file_id: "v1",
+      duration: 5,
+      file_unique_id: "u1",
+      ...(opts?.mime_type && { mime_type: opts.mime_type }),
+    };
   }
   if (mediaField === "audio") {
     msg.audio = {
@@ -56,6 +61,7 @@ function makeCtx(
       duration: 5,
       file_unique_id: "u2",
       ...(opts?.file_name && { file_name: opts.file_name }),
+      ...(opts?.mime_type && { mime_type: opts.mime_type }),
     };
   }
   if (mediaField === "photo") {
@@ -74,6 +80,7 @@ function makeCtx(
       file_id: "d1",
       file_unique_id: "u4",
       ...(opts?.file_name && { file_name: opts.file_name }),
+      ...(opts?.mime_type && { mime_type: opts.mime_type }),
     };
   }
   if (mediaField === "animation") {
@@ -359,13 +366,18 @@ describe("resolveMedia getFile retry", () => {
   it("uses local absolute file paths directly for media downloads", async () => {
     const getFile = vi.fn().mockResolvedValue({ file_path: "/var/lib/telegram-bot-api/file.pdf" });
 
-    const result = await resolveMedia(makeCtx("document", getFile), MAX_MEDIA_BYTES, BOT_TOKEN);
+    const result = await resolveMedia(
+      makeCtx("document", getFile, { mime_type: "application/pdf" }),
+      MAX_MEDIA_BYTES,
+      BOT_TOKEN,
+    );
 
     expect(fetchRemoteMedia).not.toHaveBeenCalled();
     expect(saveMediaBuffer).not.toHaveBeenCalled();
     expect(result).toEqual(
       expect.objectContaining({
         path: "/var/lib/telegram-bot-api/file.pdf",
+        contentType: "application/pdf",
         placeholder: "<media:document>",
       }),
     );

extensions/telegram/src/bot/delivery.resolve-media.ts

@@ -90,6 +90,17 @@ function resolveTelegramFileName(msg: TelegramContext["message"]): string | unde
   );
 }
 
+function resolveTelegramMimeType(msg: TelegramContext["message"]): string | undefined {
+  return (
+    msg.audio?.mime_type ??
+    msg.voice?.mime_type ??
+    msg.video?.mime_type ??
+    msg.document?.mime_type ??
+    msg.animation?.mime_type ??
+    undefined
+  );
+}
+
 async function resolveTelegramFileWithRetry(
   ctx: TelegramContext,
 ): Promise<{ file_path?: string } | null> {
@@ -152,10 +163,11 @@ async function downloadAndSaveTelegramFile(params: {
   transport: TelegramTransport;
   maxBytes: number;
   telegramFileName?: string;
+  mimeType?: string;
   apiRoot?: string;
 }) {
   if (path.isAbsolute(params.filePath)) {
-    return { path: params.filePath, contentType: undefined };
+    return { path: params.filePath, contentType: params.mimeType };
   }
   const apiBase = resolveTelegramApiBase(params.apiRoot);
   const url = `${apiBase}/file/bot${params.token}/${params.filePath}`;
@@ -320,6 +332,7 @@ export async function resolveMedia(
     transport: resolveRequiredTelegramTransport(transport),
     maxBytes,
     telegramFileName: resolveTelegramFileName(msg),
+    mimeType: resolveTelegramMimeType(msg),
     apiRoot,
   });
   const placeholder = resolveTelegramMediaPlaceholder(msg) ?? "<media:document>";