diff --git a/CHANGELOG.md b/CHANGELOG.md
index 33dc3964efd..a2212c281c5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@ Docs: https://docs.openclaw.ai
 - Cron/agents: forward embedded-run tool policy and internal event params into the attempt layer so `--tools` allowlists, cron-owned message-tool suppression, explicit message targeting, and command-path internal events all take effect at runtime again. (#62675) Thanks @hexsprite.
 - Setup/providers: guard preferred-provider lookup during setup so malformed plugin metadata with a missing provider id no longer crashes the wizard with `Cannot read properties of undefined (reading 'trim')`. (#66649) Thanks @Tianworld.
 - Matrix/security: normalize sandboxed profile avatar params, preserve `mxc://` avatar URLs, and surface gmail watcher stop failures during reload. (#64701) Thanks @slepybear.
+- Telegram/documents: drop leaked binary caption bytes from inbound Telegram text handling so document uploads like `.mobi` or `.epub` no longer explode prompt token counts. (#66663) Thanks @joelnishanth.
 
 ## 2026.4.14
 
diff --git a/extensions/telegram/src/bot-handlers.runtime.ts b/extensions/telegram/src/bot-handlers.runtime.ts
index cf2e81f0174..7447b696164 100644
--- a/extensions/telegram/src/bot-handlers.runtime.ts
+++ b/extensions/telegram/src/bot-handlers.runtime.ts
@@ -212,7 +212,7 @@ export const registerTelegramHandlers = ({
       entry.debounceLane === "forward" ? FORWARD_BURST_DEBOUNCE_MS : debounceMs,
     buildKey: (entry) => entry.debounceKey,
     shouldDebounce: (entry) => {
-      const text = entry.msg.text ?? entry.msg.caption ?? "";
+      const text = getTelegramTextParts(entry.msg).text;
       const hasDebounceableText = shouldDebounceTextInbound({
         text,
         cfg,
@@ -248,7 +248,7 @@ export const registerTelegramHandlers = ({
         return;
       }
       const combinedText = entries
-        .map((entry) => entry.msg.text ?? entry.msg.caption ?? "")
+        .map((entry) => getTelegramTextParts(entry.msg).text)
         .filter(Boolean)
         .join("\n");
       const combinedMedia = entries.flatMap((entry) => entry.allMedia);
@@ -836,7 +836,7 @@ export const registerTelegramHandlers = ({
       // for reactions, we cannot determine if the reaction came from a topic, so block all
       // reactions if requireTopic is enabled for this DM.
       if (!isGroup) {
-        const requireTopic = (eventAuthContext.groupConfig as TelegramDirectConfig | undefined)
+        const requireTopic = (eventAuthContext.groupConfig)
           ?.requireTopic;
         if (requireTopic === true) {
           logVerbose(
diff --git a/extensions/telegram/src/bot/body-helpers.ts b/extensions/telegram/src/bot/body-helpers.ts
index 8564e9545ca..064e1371645 100644
--- a/extensions/telegram/src/bot/body-helpers.ts
+++ b/extensions/telegram/src/bot/body-helpers.ts
@@ -92,14 +92,25 @@ export function buildSenderLabel(msg: Message, senderId?: number | string) {
 
 export type TelegramTextEntity = NonNullable<Message["entities"]>[number];
 
+export function isBinaryContent(text: string): boolean {
+  for (let i = 0; i < text.length; i++) {
+    const code = text.charCodeAt(i);
+    if (code <= 0x1f && code !== 0x09 && code !== 0x0a && code !== 0x0d) {
+      return true;
+    }
+  }
+  return false;
+}
+
 export function getTelegramTextParts(
   msg: Pick<Message, "text" | "caption" | "entities" | "caption_entities">,
 ): {
   text: string;
   entities: TelegramTextEntity[];
 } {
-  const text = msg.text ?? msg.caption ?? "";
-  const entities = msg.entities ?? msg.caption_entities ?? [];
+  const raw = msg.text ?? msg.caption ?? "";
+  const text = isBinaryContent(raw) ? "" : raw;
+  const entities = text ? (msg.entities ?? msg.caption_entities ?? []) : [];
   return { text, entities };
 }
 
diff --git a/extensions/telegram/src/bot/helpers.test.ts b/extensions/telegram/src/bot/helpers.test.ts
index 348d44cdf40..a22607a9b07 100644
--- a/extensions/telegram/src/bot/helpers.test.ts
+++ b/extensions/telegram/src/bot/helpers.test.ts
@@ -7,6 +7,7 @@ import {
   expandTextLinks,
   getTelegramTextParts,
   hasBotMention,
+  isBinaryContent,
   normalizeForwardedContext,
   resolveTelegramDirectPeerId,
   resolveTelegramForumFlag,
@@ -444,6 +445,67 @@ describe("describeReplyTarget", () => {
   });
 });
 
+describe("isBinaryContent", () => {
+  it("returns false for normal user text", () => {
+    expect(isBinaryContent("Hello, world!")).toBe(false);
+  });
+
+  it("returns false for text with common whitespace (tabs, newlines)", () => {
+    expect(isBinaryContent("line one\nline two\ttab")).toBe(false);
+  });
+
+  it("returns true for string containing null bytes", () => {
+    expect(isBinaryContent("PK\x00\x03\x04")).toBe(true);
+  });
+
+  it("returns true for typical binary file header bytes", () => {
+    const mobiBinarySnippet = "\x00\x00\x00\x01BOOKMOBI\x00\x00\x02\x0E";
+    expect(isBinaryContent(mobiBinarySnippet)).toBe(true);
+  });
+
+  it("returns false for empty string", () => {
+    expect(isBinaryContent("")).toBe(false);
+  });
+});
+
+describe("getTelegramTextParts — binary caption filtering (#66647)", () => {
+  it("strips binary caption content to prevent token explosion", () => {
+    const binaryCaption = "PK\x03\x04\x14\x00\x08binary-ebook-data";
+    const result = getTelegramTextParts({
+      caption: binaryCaption,
+      caption_entities: [{ type: "mention", offset: 0, length: 5 }],
+      chat: { id: 1, type: "private" },
+      date: 1,
+      message_id: 1,
+    } as any);
+    expect(result.text).toBe("");
+    expect(result.entities).toEqual([]);
+  });
+
+  it("preserves normal caption text", () => {
+    const result = getTelegramTextParts({
+      caption: "Here is my document",
+      caption_entities: [],
+      chat: { id: 1, type: "private" },
+      date: 1,
+      message_id: 1,
+    } as any);
+    expect(result.text).toBe("Here is my document");
+  });
+
+  it("strips binary content in msg.text as well", () => {
+    const result = getTelegramTextParts({
+      text: "\x00\x01\x02 binary junk",
+      entities: [{ type: "bold", offset: 0, length: 3 }],
+      chat: { id: 1, type: "private" },
+      date: 1,
+      message_id: 1,
+    } as any);
+    expect(result.text).toBe("");
+    expect(result.entities).toEqual([]);
+  });
+});
+
 describe("hasBotMention", () => {
   it("prefers caption text and caption entities when message text is absent", () => {
     expect(
diff --git a/extensions/telegram/src/bot/helpers.ts b/extensions/telegram/src/bot/helpers.ts
index 4d176f30a28..4251d97229b 100644
--- a/extensions/telegram/src/bot/helpers.ts
+++ b/extensions/telegram/src/bot/helpers.ts
@@ -18,6 +18,7 @@ import {
   extractTelegramLocation,
   getTelegramTextParts,
   hasBotMention,
+  isBinaryContent,
   normalizeForwardedContext,
   resolveTelegramMediaPlaceholder,
   type TelegramForwardedContext,
@@ -32,6 +33,7 @@ export {
   extractTelegramLocation,
   getTelegramTextParts,
   hasBotMention,
+  isBinaryContent,
   normalizeForwardedContext,
   resolveTelegramMediaPlaceholder,
 };