From d9ed2c425a1b522319ac4af078cf3385997e6c64 Mon Sep 17 00:00:00 2001
From: Ayaan Zaidi <zaidi@uplause.io>
Date: Thu, 26 Feb 2026 16:13:24 +0530
Subject: [PATCH] fix(telegram): prime final preview before stop flush

---
 src/telegram/bot-message-dispatch.test.ts | 35 +++++++++++++++++++++++
 src/telegram/lane-delivery.ts             |  5 ++++
 2 files changed, 40 insertions(+)

diff --git a/src/telegram/bot-message-dispatch.test.ts b/src/telegram/bot-message-dispatch.test.ts
index 7e82adafec2..7f62a77ae16 100644
--- a/src/telegram/bot-message-dispatch.test.ts
+++ b/src/telegram/bot-message-dispatch.test.ts
@@ -381,6 +381,41 @@ describe("dispatchTelegramMessage draft streaming", () => {
     expect(draftStream.stop).toHaveBeenCalled();
   });
 
+  it("primes stop() with final text when pending partial is below initial threshold", async () => {
+    let answerMessageId: number | undefined;
+    const answerDraftStream = {
+      update: vi.fn(),
+      flush: vi.fn().mockResolvedValue(undefined),
+      messageId: vi.fn().mockImplementation(() => answerMessageId),
+      clear: vi.fn().mockResolvedValue(undefined),
+      stop: vi.fn().mockImplementation(async () => {
+        answerMessageId = 777;
+      }),
+      forceNewMessage: vi.fn(),
+    };
+    const reasoningDraftStream = createDraftStream();
+    createTelegramDraftStream
+      .mockImplementationOnce(() => answerDraftStream)
+      .mockImplementationOnce(() => reasoningDraftStream);
+    dispatchReplyWithBufferedBlockDispatcher.mockImplementation(
+      async ({ dispatcherOptions, replyOptions }) => {
+        await replyOptions?.onPartialReply?.({ text: "no" });
+        await dispatcherOptions.deliver({ text: "no problem" }, { kind: "final" });
+        return { queuedFinal: true };
+      },
+    );
+    deliverReplies.mockResolvedValue({ delivered: true });
+    editMessageTelegram.mockResolvedValue({ ok: true, chatId: "123", messageId: "777" });
+
+    await dispatchWithContext({ context: createContext() });
+
+    expect(answerDraftStream.update).toHaveBeenCalledWith("no");
+    expect(answerDraftStream.update).toHaveBeenLastCalledWith("no problem");
+    expect(editMessageTelegram).toHaveBeenCalledWith(123, 777, "no problem", expect.any(Object));
+    expect(deliverReplies).not.toHaveBeenCalled();
+    expect(answerDraftStream.stop).toHaveBeenCalled();
+  });
+
   it("does not overwrite finalized preview when additional final payloads are sent", async () => {
     const draftStream = createDraftStream(999);
     createTelegramDraftStream.mockReturnValue(draftStream);
diff --git a/src/telegram/lane-delivery.ts b/src/telegram/lane-delivery.ts
index 91aa59dc888..64902ac3911 100644
--- a/src/telegram/lane-delivery.ts
+++ b/src/telegram/lane-delivery.ts
@@ -123,6 +123,11 @@ export function createLaneTextDeliverer(params: CreateLaneTextDelivererParams) {
     const hadPreviewMessage =
       typeof previewMessageIdOverride === "number" || typeof lanePreviewMessageId === "number";
     if (stopBeforeEdit) {
+      if (!hadPreviewMessage && context === "final") {
+        // If debounce prevented the first preview, replace stale pending partial text
+        // before final stop() flush sends the first visible preview.
+        lane.stream.update(text);
+      }
       await params.stopDraftLane(lane);
     }
     const previewMessageId =