From 5b87ddf3932831e1911f5f50523aae046e7df321 Mon Sep 17 00:00:00 2001
From: Ayaan Zaidi <zaidi@uplause.io>
Date: Tue, 10 Mar 2026 21:00:17 +0530
Subject: [PATCH] fix: avoid dropping telegram fallback chunks

---
 src/telegram/send.test.ts | 24 ++++++++++++++++++++++++
 src/telegram/send.ts      | 16 ++++++++++------
 2 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/src/telegram/send.test.ts b/src/telegram/send.test.ts
index cc6fd80f649..25752fc337e 100644
--- a/src/telegram/send.test.ts
+++ b/src/telegram/send.test.ts
@@ -1347,6 +1347,30 @@ describe("sendMessageTelegram", () => {
     expect(plainFallbackCalls.every((call) => String(call?.[1] ?? "").length > 0)).toBe(true);
     expect(res.messageId).toBe("93");
   });
+
+  it("cuts over to plain text when fallback text needs more chunks than html", async () => {
+    const chatId = "123";
+    const htmlText = `<b>${"A".repeat(5000)}</b>`;
+    const plainText = "P".repeat(9000);
+    const sendMessage = vi
+      .fn()
+      .mockResolvedValueOnce({ message_id: 94, chat: { id: chatId } })
+      .mockResolvedValueOnce({ message_id: 95, chat: { id: chatId } })
+      .mockResolvedValueOnce({ message_id: 96, chat: { id: chatId } });
+    const api = { sendMessage } as unknown as { sendMessage: typeof sendMessage };
+
+    const res = await sendMessageTelegram(chatId, htmlText, {
+      token: "tok",
+      api,
+      textMode: "html",
+      plainText,
+    });
+
+    expect(sendMessage).toHaveBeenCalledTimes(3);
+    expect(sendMessage.mock.calls.every((call) => call[2]?.parse_mode === undefined)).toBe(true);
+    expect(sendMessage.mock.calls.map((call) => String(call[1] ?? "")).join("")).toBe(plainText);
+    expect(res.messageId).toBe("96");
+  });
 });
 
 describe("reactMessageTelegram", () => {
diff --git a/src/telegram/send.ts b/src/telegram/send.ts
index 55499c9c308..4d52d84c80a 100644
--- a/src/telegram/send.ts
+++ b/src/telegram/send.ts
@@ -735,6 +735,7 @@ export async function sendMessageTelegram(
     rawText: string,
     context: string,
   ): Promise<{ messageId: string; chatId: string }> => {
+    const fallbackText = opts.plainText ?? rawText;
     let htmlChunks: string[];
     try {
       htmlChunks = splitTelegramHtmlChunks(rawText, 4000);
@@ -744,13 +745,16 @@ export async function sendMessageTelegram(
           error,
         )}`,
       );
-      return await sendPlainChunkedText(opts.plainText ?? rawText, context);
+      return await sendPlainChunkedText(fallbackText, context);
     }
-    const plainTextChunks = splitTelegramPlainTextFallback(
-      opts.plainText ?? rawText,
-      htmlChunks.length,
-      4000,
-    );
+    const fixedPlainTextChunks = splitTelegramPlainTextChunks(fallbackText, 4000);
+    if (fixedPlainTextChunks.length > htmlChunks.length) {
+      logVerbose(
+        `telegram ${context} plain-text fallback needs more chunks than HTML; sending plain text`,
+      );
+      return await sendPlainChunkedText(fallbackText, context);
+    }
+    const plainTextChunks = splitTelegramPlainTextFallback(fallbackText, htmlChunks.length, 4000);
     const chunks = htmlChunks.map((chunk, index) => ({
       rawText: chunk,
       htmlText: chunk,