From 4d6c8edd7484f72e058a882b7bf26c75ec9cfdbd Mon Sep 17 00:00:00 2001
From: Robin Waslander <r.waslander@gmail.com>
Date: Sat, 28 Mar 2026 22:27:56 +0100
Subject: [PATCH] fix(telegram): skip empty text replies instead of crashing
 with GrammyError 400 (#56620)

Filter whitespace-only text chunks at the bot delivery fan-in before
they reach sendTelegramText(). Covers normal text replies, follow-up
text, and voice fallback text paths.

Media-only replies are unaffected. message_sent hook still fires with
success: false for suppressed empty replies.

Fixes #37278
---
 extensions/telegram/src/bot/delivery.replies.ts | 14 +++++++++++---
 extensions/telegram/src/bot/delivery.test.ts    |  8 ++++----
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/extensions/telegram/src/bot/delivery.replies.ts b/extensions/telegram/src/bot/delivery.replies.ts
index 928af45607d..60fb1dbc720 100644
--- a/extensions/telegram/src/bot/delivery.replies.ts
+++ b/extensions/telegram/src/bot/delivery.replies.ts
@@ -92,6 +92,12 @@ function markDelivered(progress: DeliveryProgress): void {
   progress.deliveredCount += 1;
 }
 
+function filterEmptyTelegramTextChunks<T extends { text: string }>(chunks: readonly T[]): T[] {
+  // Telegram rejects whitespace-only text payloads; drop them before sendMessage so
+  // hook-mutated or model-emitted empty replies become a no-op instead of a 400.
+  return chunks.filter((chunk) => chunk.text.trim().length > 0);
+}
+
 async function deliverTextReply(params: {
   bot: Bot;
   chatId: string;
@@ -108,8 +114,9 @@ async function deliverTextReply(params: {
   progress: DeliveryProgress;
 }): Promise<number | undefined> {
   let firstDeliveredMessageId: number | undefined;
+  const chunks = filterEmptyTelegramTextChunks(params.chunkText(params.replyText));
   await sendChunkedTelegramReplyText({
-    chunks: params.chunkText(params.replyText),
+    chunks,
     progress: params.progress,
     replyToId: params.replyToId,
     replyToMode: params.replyToMode,
@@ -155,8 +162,9 @@ async function sendPendingFollowUpText(params: {
   replyToMode: ReplyToMode;
   progress: DeliveryProgress;
 }): Promise<void> {
+  const chunks = filterEmptyTelegramTextChunks(params.chunkText(params.text));
   await sendChunkedTelegramReplyText({
-    chunks: params.chunkText(params.text),
+    chunks,
     progress: params.progress,
     replyToId: params.replyToId,
     replyToMode: params.replyToMode,
@@ -204,7 +212,7 @@ async function sendTelegramVoiceFallbackText(opts: {
   replyQuoteText?: string;
 }): Promise<number | undefined> {
   let firstDeliveredMessageId: number | undefined;
-  const chunks = opts.chunkText(opts.text);
+  const chunks = filterEmptyTelegramTextChunks(opts.chunkText(opts.text));
   let appliedReplyTo = false;
   for (let i = 0; i < chunks.length; i += 1) {
     const chunk = chunks[i];
diff --git a/extensions/telegram/src/bot/delivery.test.ts b/extensions/telegram/src/bot/delivery.test.ts
index f583992e599..c9347aa2dbb 100644
--- a/extensions/telegram/src/bot/delivery.test.ts
+++ b/extensions/telegram/src/bot/delivery.test.ts
@@ -170,7 +170,7 @@ describe("deliverReplies", () => {
     messageHookRunner.hasHooks.mockImplementation(
       (name: string) => name === "message_sending" || name === "message_sent",
     );
-    messageHookRunner.runMessageSending.mockResolvedValue({ content: "" });
+    messageHookRunner.runMessageSending.mockResolvedValue({ content: "   " });
 
     const runtime = createRuntime(false);
     const sendMessage = vi.fn();
@@ -184,7 +184,7 @@ describe("deliverReplies", () => {
 
     expect(sendMessage).not.toHaveBeenCalled();
     expect(messageHookRunner.runMessageSent).toHaveBeenCalledWith(
-      expect.objectContaining({ success: false, content: "" }),
+      expect.objectContaining({ success: false, content: "   " }),
       expect.objectContaining({ channelId: "telegram", conversationId: "123" }),
     );
   });
@@ -600,7 +600,7 @@ describe("deliverReplies", () => {
     );
   });
 
-  it("throws when formatted and plain fallback text are both empty", async () => {
+  it("skips whitespace-only text replies without calling Telegram", async () => {
     const runtime = createRuntime();
     const sendMessage = vi.fn();
     const bot = { api: { sendMessage } } as unknown as Bot;
@@ -615,7 +615,7 @@ describe("deliverReplies", () => {
         replyToMode: "off",
         textLimit: 4000,
       }),
-    ).rejects.toThrow("empty formatted text and empty plain fallback");
+    ).resolves.toEqual({ delivered: false });
     expect(sendMessage).not.toHaveBeenCalled();
   });