fix: telegram html formatting (#435, thanks @RandyVentures)

CHANGELOG.md

@@ -85,6 +85,7 @@
 - Telegram: add draft streaming via `sendMessageDraft` with `telegram.streamMode`, plus `/reasoning stream` for draft-only reasoning.
 - Telegram: honor `/activation` session mode for group mention gating and clarify group activation docs. Thanks @julianengel for PR #377.
 - Telegram: isolate forum topic transcripts per thread and validate Gemini turn ordering in multi-topic sessions. Thanks @hsrvc for PR #407.
+- Telegram: render Telegram-safe HTML for outbound formatting and fall back to plain text on parse errors. Thanks @RandyVentures for PR #435.
 - iMessage: ignore disconnect errors during shutdown (avoid unhandled promise rejections). Thanks @antons for PR #359.
 - Messages: stop defaulting ack reactions to 👀 when identity emoji is missing.
 - Auto-reply: require slash for control commands to avoid false triggers in normal text.

docs/providers/telegram.md

@@ -41,6 +41,12 @@ Multi-account support: use `telegram.accounts` with per-account tokens and optio
 - Replies always route back to the same Telegram chat.
 - Long-polling uses grammY runner with per-chat sequencing; overall concurrency is capped by `agent.maxConcurrent`.
 
+## Formatting (Telegram HTML)
+- Outbound Telegram text uses `parse_mode: "HTML"` (Telegram’s supported tag subset).
+- Markdown-ish input is rendered into **Telegram-safe HTML** (bold/italic/strike/code/links); block elements are flattened to text with newlines/bullets.
+- Raw HTML from models is escaped to avoid Telegram parse errors.
+- If Telegram rejects the HTML payload, Clawdbot retries the same message as plain text.
+
 ## Group activation modes
 
 By default, the bot only responds to mentions in groups (`@botname` or patterns in `routing.groupChat.mentionPatterns`). To change this behavior:

src/telegram/bot.ts

@@ -52,6 +52,7 @@ import type { RuntimeEnv } from "../runtime.js";
 import { loadWebMedia } from "../web/media.js";
 import { resolveTelegramAccount } from "./accounts.js";
 import { createTelegramDraftStream } from "./draft-stream.js";
+import { markdownToTelegramHtml } from "./format.js";
 import {
   readTelegramAllowFromStore,
   upsertTelegramPairingRequest,
@@ -1427,9 +1428,10 @@ async function sendTelegramText(
   if (threadParams) {
     baseParams.message_thread_id = threadParams.message_thread_id;
   }
+  const htmlText = markdownToTelegramHtml(text);
   try {
-    const res = await bot.api.sendMessage(chatId, text, {
-      parse_mode: "Markdown",
+    const res = await bot.api.sendMessage(chatId, htmlText, {
+      parse_mode: "HTML",
       ...baseParams,
     });
     return res.message_id;
@@ -1437,7 +1439,7 @@ async function sendTelegramText(
     const errText = formatErrorMessage(err);
     if (PARSE_ERR_RE.test(errText)) {
       runtime.log?.(
-        `telegram markdown parse failed; retrying without formatting: ${errText}`,
+        `telegram HTML parse failed; retrying without formatting: ${errText}`,
       );
       const res = await bot.api.sendMessage(chatId, text, {
         ...baseParams,

src/telegram/format.test.ts

@@ -0,0 +1,50 @@
+import { describe, expect, it } from "vitest";
+
+import { markdownToTelegramHtml } from "./format.js";
+
+describe("markdownToTelegramHtml", () => {
+  it("renders basic inline formatting", () => {
+    const res = markdownToTelegramHtml("hi _there_ **boss** `code`");
+    expect(res).toBe("hi <i>there</i> <b>boss</b> <code>code</code>");
+  });
+
+  it("renders links as Telegram-safe HTML", () => {
+    const res = markdownToTelegramHtml("see [docs](https://example.com)");
+    expect(res).toBe('see <a href="https://example.com">docs</a>');
+  });
+
+  it("escapes raw HTML", () => {
+    const res = markdownToTelegramHtml("<b>nope</b>");
+    expect(res).toBe("&lt;b&gt;nope&lt;/b&gt;");
+  });
+
+  it("escapes unsafe characters", () => {
+    const res = markdownToTelegramHtml("a & b < c");
+    expect(res).toBe("a &amp; b &lt; c");
+  });
+
+  it("renders paragraphs with blank lines", () => {
+    const res = markdownToTelegramHtml("first\n\nsecond");
+    expect(res).toBe("first\n\nsecond");
+  });
+
+  it("renders lists without block HTML", () => {
+    const res = markdownToTelegramHtml("- one\n- two");
+    expect(res).toBe("• one\n• two");
+  });
+
+  it("renders ordered lists with numbering", () => {
+    const res = markdownToTelegramHtml("2. two\n3. three");
+    expect(res).toBe("2. two\n3. three");
+  });
+
+  it("flattens headings and blockquotes", () => {
+    const res = markdownToTelegramHtml("# Title\n\n> Quote");
+    expect(res).toBe("Title\n\nQuote");
+  });
+
+  it("renders fenced code blocks", () => {
+    const res = markdownToTelegramHtml("```js\nconst x = 1;\n```");
+    expect(res).toBe("<pre><code>const x = 1;\n</code></pre>");
+  });
+});

src/telegram/format.ts

@@ -0,0 +1,141 @@
+import MarkdownIt from "markdown-it";
+
+type ListState = {
+  type: "bullet" | "ordered";
+  index: number;
+};
+
+type RenderEnv = {
+  telegramListStack?: ListState[];
+  telegramLinkStack?: boolean[];
+};
+
+const md = new MarkdownIt({
+  html: false,
+  linkify: true,
+  breaks: false,
+  typographer: false,
+});
+
+md.enable("strikethrough");
+
+const { escapeHtml } = md.utils;
+
+function getListStack(env: RenderEnv): ListState[] {
+  if (!env.telegramListStack) env.telegramListStack = [];
+  return env.telegramListStack;
+}
+
+function getLinkStack(env: RenderEnv): boolean[] {
+  if (!env.telegramLinkStack) env.telegramLinkStack = [];
+  return env.telegramLinkStack;
+}
+
+md.renderer.rules.text = (tokens, idx) =>
+  escapeHtml(tokens[idx]?.content ?? "");
+
+md.renderer.rules.softbreak = () => "\n";
+md.renderer.rules.hardbreak = () => "\n";
+
+md.renderer.rules.paragraph_open = () => "";
+md.renderer.rules.paragraph_close = (_tokens, _idx, _opts, env) => {
+  const stack = getListStack(env as RenderEnv);
+  return stack.length ? "" : "\n\n";
+};
+
+md.renderer.rules.heading_open = () => "";
+md.renderer.rules.heading_close = () => "\n\n";
+
+md.renderer.rules.blockquote_open = () => "";
+md.renderer.rules.blockquote_close = () => "\n";
+
+md.renderer.rules.bullet_list_open = (_tokens, _idx, _opts, env) => {
+  getListStack(env as RenderEnv).push({ type: "bullet", index: 0 });
+  return "";
+};
+md.renderer.rules.bullet_list_close = (_tokens, _idx, _opts, env) => {
+  getListStack(env as RenderEnv).pop();
+  return "";
+};
+md.renderer.rules.ordered_list_open = (tokens, idx, _opts, env) => {
+  const start = Number(tokens[idx]?.attrGet("start") ?? "1");
+  getListStack(env as RenderEnv).push({ type: "ordered", index: start - 1 });
+  return "";
+};
+md.renderer.rules.ordered_list_close = (_tokens, _idx, _opts, env) => {
+  getListStack(env as RenderEnv).pop();
+  return "";
+};
+md.renderer.rules.list_item_open = (_tokens, _idx, _opts, env) => {
+  const stack = getListStack(env as RenderEnv);
+  const top = stack[stack.length - 1];
+  if (!top) return "";
+  top.index += 1;
+  const indent = "  ".repeat(Math.max(0, stack.length - 1));
+  const prefix = top.type === "ordered" ? `${top.index}. ` : "• ";
+  return `${indent}${prefix}`;
+};
+md.renderer.rules.list_item_close = () => "\n";
+
+md.renderer.rules.em_open = () => "<i>";
+md.renderer.rules.em_close = () => "</i>";
+md.renderer.rules.strong_open = () => "<b>";
+md.renderer.rules.strong_close = () => "</b>";
+md.renderer.rules.s_open = () => "<s>";
+md.renderer.rules.s_close = () => "</s>";
+
+md.renderer.rules.code_inline = (tokens, idx) =>
+  `<code>${escapeHtml(tokens[idx]?.content ?? "")}</code>`;
+md.renderer.rules.code_block = (tokens, idx) =>
+  `<pre><code>${escapeHtml(tokens[idx]?.content ?? "")}</code></pre>\n`;
+md.renderer.rules.fence = (tokens, idx) =>
+  `<pre><code>${escapeHtml(tokens[idx]?.content ?? "")}</code></pre>\n`;
+
+md.renderer.rules.link_open = (tokens, idx, _opts, env) => {
+  const href = tokens[idx]?.attrGet("href") ?? "";
+  const safeHref = escapeHtml(href);
+  const stack = getLinkStack(env as RenderEnv);
+  const hasHref = Boolean(safeHref);
+  stack.push(hasHref);
+  return hasHref ? `<a href="${safeHref}">` : "";
+};
+md.renderer.rules.link_close = (_tokens, _idx, _opts, env) => {
+  const stack = getLinkStack(env as RenderEnv);
+  const hasHref = stack.pop();
+  return hasHref ? "</a>" : "";
+};
+
+md.renderer.rules.image = (tokens, idx) => {
+  const alt = tokens[idx]?.content ?? "";
+  return escapeHtml(alt);
+};
+
+md.renderer.rules.html_block = (tokens, idx) =>
+  escapeHtml(tokens[idx]?.content ?? "");
+md.renderer.rules.html_inline = (tokens, idx) =>
+  escapeHtml(tokens[idx]?.content ?? "");
+
+md.renderer.rules.table_open = () => "";
+md.renderer.rules.table_close = () => "";
+md.renderer.rules.thead_open = () => "";
+md.renderer.rules.thead_close = () => "";
+md.renderer.rules.tbody_open = () => "";
+md.renderer.rules.tbody_close = () => "";
+md.renderer.rules.tr_open = () => "";
+md.renderer.rules.tr_close = () => "\n";
+md.renderer.rules.th_open = () => "";
+md.renderer.rules.th_close = () => "\t";
+md.renderer.rules.td_open = () => "";
+md.renderer.rules.td_close = () => "\t";
+
+md.renderer.rules.hr = () => "\n";
+
+export function markdownToTelegramHtml(markdown: string): string {
+  const env: RenderEnv = {};
+  const rendered = md.render(markdown ?? "", env);
+  return rendered
+    .replace(/[ \t]+\n/g, "\n")
+    .replace(/\t+\n/g, "\n")
+    .replace(/\n{3,}/g, "\n\n")
+    .trimEnd();
+}

src/telegram/monitor.test.ts

@@ -51,7 +51,7 @@ vi.mock("./bot.js", () => ({
       const text = ctx.message.text ?? ctx.message.caption ?? "";
       if (isGroup && !text.includes("@mybot")) return;
       if (!text.trim()) return;
-      await api.sendMessage(chatId, `echo:${text}`, { parse_mode: "Markdown" });
+      await api.sendMessage(chatId, `echo:${text}`, { parse_mode: "HTML" });
     };
     return {
       on: vi.fn(),
@@ -102,7 +102,7 @@ describe("monitorTelegramProvider (grammY)", () => {
       getFile: vi.fn(async () => ({})),
     });
     expect(api.sendMessage).toHaveBeenCalledWith(123, "echo:hi", {
-      parse_mode: "Markdown",
+      parse_mode: "HTML",
     });
   });
 

src/telegram/send.test.ts

@@ -15,7 +15,7 @@ describe("sendMessageTelegram", () => {
     loadWebMedia.mockReset();
   });
 
-  it("falls back to plain text when Telegram rejects Markdown", async () => {
+  it("falls back to plain text when Telegram rejects HTML", async () => {
     const chatId = "123";
     const parseErr = new Error(
       "400: Bad Request: can't parse entities: Can't find end of the entity starting at byte offset 9",
@@ -37,8 +37,8 @@ describe("sendMessageTelegram", () => {
       verbose: true,
     });
 
-    expect(sendMessage).toHaveBeenNthCalledWith(1, chatId, "_oops_", {
-      parse_mode: "Markdown",
+    expect(sendMessage).toHaveBeenNthCalledWith(1, chatId, "<i>oops</i>", {
+      parse_mode: "HTML",
     });
     expect(sendMessage).toHaveBeenNthCalledWith(2, chatId, "_oops_");
     expect(res.chatId).toBe(chatId);
@@ -60,7 +60,7 @@ describe("sendMessageTelegram", () => {
     });
 
     expect(sendMessage).toHaveBeenCalledWith("123", "hi", {
-      parse_mode: "Markdown",
+      parse_mode: "HTML",
     });
   });
 
@@ -175,7 +175,7 @@ describe("sendMessageTelegram", () => {
     });
 
     expect(sendMessage).toHaveBeenCalledWith(chatId, "hello forum", {
-      parse_mode: "Markdown",
+      parse_mode: "HTML",
       message_thread_id: 271,
     });
   });
@@ -197,7 +197,7 @@ describe("sendMessageTelegram", () => {
     });
 
     expect(sendMessage).toHaveBeenCalledWith(chatId, "reply text", {
-      parse_mode: "Markdown",
+      parse_mode: "HTML",
       reply_to_message_id: 100,
     });
   });
@@ -220,7 +220,7 @@ describe("sendMessageTelegram", () => {
     });
 
     expect(sendMessage).toHaveBeenCalledWith(chatId, "forum reply", {
-      parse_mode: "Markdown",
+      parse_mode: "HTML",
       message_thread_id: 271,
       reply_to_message_id: 500,
     });
@@ -249,12 +249,17 @@ describe("sendMessageTelegram", () => {
       replyToMessageId: 100,
     });
 
-    // First call: with Markdown + thread params
-    expect(sendMessage).toHaveBeenNthCalledWith(1, chatId, "_bad markdown_", {
-      parse_mode: "Markdown",
-      message_thread_id: 271,
-      reply_to_message_id: 100,
-    });
+    // First call: with HTML + thread params
+    expect(sendMessage).toHaveBeenNthCalledWith(
+      1,
+      chatId,
+      "<i>bad markdown</i>",
+      {
+        parse_mode: "HTML",
+        message_thread_id: 271,
+        reply_to_message_id: 100,
+      },
+    );
     // Second call: plain text BUT still with thread params (critical!)
     expect(sendMessage).toHaveBeenNthCalledWith(2, chatId, "_bad markdown_", {
       message_thread_id: 271,

src/telegram/send.ts

@@ -8,6 +8,7 @@ import { mediaKindFromMime } from "../media/constants.js";
 import { isGifMedia } from "../media/mime.js";
 import { loadWebMedia } from "../web/media.js";
 import { resolveTelegramAccount } from "./accounts.js";
+import { markdownToTelegramHtml } from "./format.js";
 
 type TelegramSendOpts = {
   token?: string;
@@ -204,20 +205,21 @@ export async function sendMessageTelegram(
   if (!text || !text.trim()) {
     throw new Error("Message must be non-empty for Telegram sends");
   }
+  const htmlText = markdownToTelegramHtml(text);
   const textParams = hasThreadParams
-    ? { parse_mode: "Markdown" as const, ...threadParams }
-    : { parse_mode: "Markdown" as const };
+    ? { parse_mode: "HTML" as const, ...threadParams }
+    : { parse_mode: "HTML" as const };
   const res = await request(
-    () => api.sendMessage(chatId, text, textParams),
+    () => api.sendMessage(chatId, htmlText, textParams),
     "message",
   ).catch(async (err) => {
-    // Telegram rejects malformed Markdown (e.g., unbalanced '_' or '*').
+    // Telegram rejects malformed HTML (e.g., unsupported tags or entities).
     // When that happens, fall back to plain text so the message still delivers.
     const errText = formatErrorMessage(err);
     if (PARSE_ERR_RE.test(errText)) {
       if (opts.verbose) {
         console.warn(
-          `telegram markdown parse failed, retrying as plain text: ${errText}`,
+          `telegram HTML parse failed, retrying as plain text: ${errText}`,
         );
       }
       return await request(