refactor(telegram): distill retained preview finalization

obviyus · obviyus · commit 2a39e6ae4158 · 2026-06-03T12:49:27.000Z
diff --git a/extensions/telegram/src/bot-message-dispatch.test.ts b/extensions/telegram/src/bot-message-dispatch.test.ts
@@ -3577,7 +3577,6 @@ describe("dispatchTelegramMessage draft streaming", () => {
     const { answerDraftStream } = setupDraftStreams({ answerMessageId: 2001 });
     dispatchReplyWithBufferedBlockDispatcher.mockImplementation(
       async ({ dispatcherOptions, replyOptions }) => {
-        // Force a generic rotation (tool-progress handoff)
         await replyOptions?.onToolStart?.({ name: "exec", phase: "start" });
         await dispatcherOptions.deliver(
           { text: "A".repeat(4000) + "B".repeat(4000) },
@@ -3592,7 +3591,6 @@ describe("dispatchTelegramMessage draft streaming", () => {
       textLimit: 4000,
     });
 
-    // The stream should receive the first chunk ("A"s), not skip it because of activeChunkIndex being falsely incremented
     expect(answerDraftStream.update).toHaveBeenCalledWith("A".repeat(4000));
   });
 
@@ -3604,11 +3602,12 @@ describe("dispatchTelegramMessage draft streaming", () => {
       return { queuedFinal: true };
     });
 
-    // Provide a config that disables partial answer streams (e.g. block mode explicitly enabled)
     await dispatchWithContext({
       context: createContext(),
       streamMode: "partial",
-      telegramCfg: { streaming: { mode: "partial", block: { enabled: true } } } as any,
+      telegramCfg: {
+        streaming: { mode: "partial", block: { enabled: true } },
+      } satisfies Parameters<typeof dispatchTelegramMessage>[0]["telegramCfg"],
     });
 
     const deliveredTexts = deliverReplies.mock.calls.flatMap((call) =>
diff --git a/extensions/telegram/src/lane-delivery-text-deliverer.ts b/extensions/telegram/src/lane-delivery-text-deliverer.ts
@@ -278,12 +278,12 @@ export function createLaneTextDeliverer(params: CreateLaneTextDelivererParams) {
         : [text];
 
     const clampActiveChunkIndex = () =>
-      Math.min(lane.activeChunkIndex ?? 0, Math.max(0, chunks.length - 1));
+      Math.min(lane.activeChunkIndex, Math.max(0, chunks.length - 1));
     const activeChunkIndex = clampActiveChunkIndex();
-    const firstChunk = chunks[activeChunkIndex];
+    const activeChunk = chunks[activeChunkIndex];
     const remainingChunks = chunks.slice(activeChunkIndex + 1);
 
-    if (!firstChunk || firstChunk.length > params.draftMaxChars) {
+    if (!activeChunk || activeChunk.length > params.draftMaxChars) {
       return undefined;
     }
 
@@ -297,12 +297,11 @@ export function createLaneTextDeliverer(params: CreateLaneTextDelivererParams) {
         deliveredText: deliveredStreamTextBeforeUpdate,
         finalText,
       }) &&
-      deliveredStreamTextBeforeUpdate.length > firstChunk.trimEnd().length;
+      deliveredStreamTextBeforeUpdate.length > activeChunk.trimEnd().length;
 
     const finalizeDeliveredPrefix = async (
       deliveredStreamText: string,
       messageId: number,
-      suffixSourceText = activeFullText,
     ): Promise<LaneDeliveryResult> => {
       lane.finalized = true;
       params.markDelivered();
@@ -321,7 +320,7 @@ export function createLaneTextDeliverer(params: CreateLaneTextDelivererParams) {
           }
         }
       }
-      const suffix = suffixSourceText.slice(deliveredStreamText.length);
+      const suffix = activeFullText.slice(deliveredStreamText.length);
       if (suffix.trim().length > 0) {
         for (const chunk of compactChunks(params.splitFinalTextForStream?.(suffix) ?? [])) {
           if (chunk.trim().length === 0) {
@@ -408,18 +407,18 @@ export function createLaneTextDeliverer(params: CreateLaneTextDelivererParams) {
     }
 
     if (!deliveredPrefixBeforeUpdate) {
-      lane.lastPartialText = firstChunk;
+      lane.lastPartialText = activeChunk;
       lane.hasStreamedMessage = true;
       lane.finalized = false;
-      stream.update(firstChunk);
+      stream.update(activeChunk);
     }
     if (isFinal) {
       await params.stopDraftLane(lane);
     } else {
       await params.flushDraftLane(lane);
     }
     const activeChunkIndexAfterStop = isFinal ? clampActiveChunkIndex() : activeChunkIndex;
-    const activeChunkAfterStop = chunks[activeChunkIndexAfterStop] ?? firstChunk;
+    const activeChunkAfterStop = chunks[activeChunkIndexAfterStop] ?? activeChunk;
     const remainingChunksAfterStop = chunks.slice(activeChunkIndexAfterStop + 1);
 
     const messageId = stream.messageId();
@@ -434,14 +433,14 @@ export function createLaneTextDeliverer(params: CreateLaneTextDelivererParams) {
 
     const deliveredStreamTextAfterStop = stream.lastDeliveredText?.();
     const activeChunkTextAfterStop = activeChunkAfterStop.trimEnd();
-    const retainedFirstChunkAfterStop =
+    const retainedActiveChunkAfterStop =
       activeChunkIndexAfterStop !== activeChunkIndex &&
-      deliveredStreamTextAfterStop === firstChunk.trimEnd();
+      deliveredStreamTextAfterStop === activeChunk.trimEnd();
     if (
       isFinal &&
       deliveredStreamTextAfterStop !== undefined &&
       deliveredStreamTextAfterStop !== activeChunkTextAfterStop &&
-      !retainedFirstChunkAfterStop
+      !retainedActiveChunkAfterStop
     ) {
       if (
         isDeliveredPrefix({ deliveredText: deliveredStreamTextAfterStop, finalText }) &&
