diff --git a/extensions/telegram/src/channel-actions.ts b/extensions/telegram/src/channel-actions.ts
index a0351aaac62..8cb8ac43934 100644
--- a/extensions/telegram/src/channel-actions.ts
+++ b/extensions/telegram/src/channel-actions.ts
@@ -214,7 +214,11 @@ export const telegramMessageActions: ChannelMessageActionAdapter = {
 
     if (action === "delete") {
       const chatId = readTelegramChatIdParam(params);
+      const hasMessageIdParam = Object.hasOwn(params, "messageId");
       const messageId = readTelegramMessageIdParam(params, { required: false });
+      if (hasMessageIdParam && typeof messageId !== "number") {
+        throw new Error("messageId must be a valid number for action=delete.");
+      }
       if (typeof messageId === "number") {
         return await handleTelegramAction(
           {
diff --git a/src/channels/plugins/actions/actions.test.ts b/src/channels/plugins/actions/actions.test.ts
index 21f1e720e0e..45b35ac7738 100644
--- a/src/channels/plugins/actions/actions.test.ts
+++ b/src/channels/plugins/actions/actions.test.ts
@@ -869,6 +869,29 @@ describe("telegramMessageActions", () => {
     expect(handleTelegramAction).not.toHaveBeenCalled();
   });
 
+  it("rejects invalid delete messageId instead of falling back to topic deletion", async () => {
+    const cfg = telegramCfg();
+    const handleAction = telegramMessageActions.handleAction;
+    if (!handleAction) {
+      throw new Error("telegram handleAction unavailable");
+    }
+
+    await expect(
+      handleAction({
+        channel: "telegram",
+        action: "delete",
+        params: {
+          to: "-1001234567890",
+          messageId: "oops",
+          topicId: 271,
+        },
+        cfg,
+      }),
+    ).rejects.toThrow(/messageId must be a valid number for action=delete/i);
+
+    expect(handleTelegramAction).not.toHaveBeenCalled();
+  });
+
   it("rejects topic-delete when threadId/topicId is missing", async () => {
     const cfg = telegramCfg();
     const handleAction = telegramMessageActions.handleAction;