fix(gateway): preserve repeated characters in chat stream merge (#72400)

* fix(gateway): preserve repeated characters in chat stream merge

* fix(gateway): cap live chat stream buffers

CHANGELOG.md

@@ -60,6 +60,7 @@ Docs: https://docs.openclaw.ai
 - WebChat/Control UI: support non-video file attachments in chat uploads while preserving the existing image attachment path and MIME-sniff fallback for generic image uploads. (#70947) Thanks @IAMSamuelRodda.
 - Skills/memory: restore Chokidar v5 hot reloads by watching concrete skill and memory roots with filters, including SKILL.md removals and deleted skill folders without broad workspace recursion. Fixes #27404, #33585, and #41606. Thanks @shelvenzhou, @08820048, and @rocke2020.
 - Gateway/chat: keep duplicate attachment-backed `chat.send` retries with the same idempotency key on the documented in-flight path so aborts still target the real active run. Fixes #70139. Thanks @Feelw00.
+- Gateway/chat: preserve repeated boundary characters while merging assistant chat stream deltas, including repeated digits, CJK characters, and markdown/table tokens. Fixes #63769; carries forward #63994 and #65457. Thanks @yon950905 and @mohuaxiao.
 - Plugins: share package entrypoint resolution between install and discovery, reject mismatched `runtimeExtensions`, and cache bundled runtime-dependency manifest reads during scans. Thanks @vincentkoc.
 - WhatsApp/Web: keep quiet but healthy linked-device sessions connected by basing the watchdog on WhatsApp Web transport activity, while retaining a longer app-silence cap so frame activity cannot mask a stuck session forever. Fixes #70678; carries forward the focused #71466 approach and keeps #63939 as related configurable-timeout follow-up. Thanks @vincentkoc and @oromeis.
 - Discord/gateway: count failed health-monitor restart attempts toward cooldown and hourly caps, and evict stale account lifecycle state during channel reloads so repeated Discord gateway recovery cannot loop on old status. Fixes #38596. (#40413) Thanks @jellyAI-dev and @vashquez.

src/gateway/live-chat-projector.ts

@@ -13,23 +13,13 @@ import {
 
 export { resolveAssistantEventPhase } from "../shared/chat-message-content.js";
 
-function appendUniqueSuffix(base: string, suffix: string): string {
-  if (!suffix) {
-    return base;
+export const MAX_LIVE_CHAT_BUFFER_CHARS = 500_000;
+
+function capLiveAssistantBuffer(text: string): string {
+  if (text.length <= MAX_LIVE_CHAT_BUFFER_CHARS) {
+    return text;
   }
-  if (!base) {
-    return suffix;
-  }
-  if (base.endsWith(suffix)) {
-    return base;
-  }
-  const maxOverlap = Math.min(base.length, suffix.length);
-  for (let overlap = maxOverlap; overlap > 0; overlap -= 1) {
-    if (base.slice(-overlap) === suffix.slice(0, overlap)) {
-      return base + suffix.slice(overlap);
-    }
-  }
-  return base + suffix;
+  return text.slice(-MAX_LIVE_CHAT_BUFFER_CHARS);
 }
 
 export function resolveMergedAssistantText(params: {
@@ -39,20 +29,20 @@ export function resolveMergedAssistantText(params: {
 }): string {
   const { previousText, nextText, nextDelta } = params;
   if (nextText && previousText) {
-    if (nextText.startsWith(previousText)) {
-      return nextText;
+    if (nextText.startsWith(previousText) && nextText.length > previousText.length) {
+      return capLiveAssistantBuffer(nextText);
     }
     if (previousText.startsWith(nextText) && !nextDelta) {
-      return previousText;
+      return capLiveAssistantBuffer(previousText);
     }
   }
   if (nextDelta) {
-    return appendUniqueSuffix(previousText, nextDelta);
+    return capLiveAssistantBuffer(previousText + nextDelta);
   }
   if (nextText) {
-    return nextText;
+    return capLiveAssistantBuffer(nextText);
   }
-  return previousText;
+  return capLiveAssistantBuffer(previousText);
 }
 
 export function normalizeLiveAssistantEventText(params: { text: string; delta?: unknown }): {

src/gateway/server-chat.stream-text-merge.test.ts

@@ -0,0 +1,73 @@
+import { describe, expect, it } from "vitest";
+import {
+  MAX_LIVE_CHAT_BUFFER_CHARS,
+  resolveMergedAssistantText,
+} from "./live-chat-projector.js";
+
+describe("server chat stream text merge", () => {
+  it.each([
+    {
+      name: "repeated digits",
+      chunks: ["1", "1", "1"],
+      expected: "111",
+    },
+    {
+      name: "repeated CJK punctuation",
+      chunks: ["。", "。", "。"],
+      expected: "。。。",
+    },
+    {
+      name: "repeated markdown emphasis tokens",
+      chunks: ["**", "**"],
+      expected: "****",
+    },
+    {
+      name: "repeated markdown table separators",
+      chunks: ["|", "|", "|"],
+      expected: "|||",
+    },
+  ])("appends incremental deltas without collapsing $name", ({ chunks, expected }) => {
+    const merged = chunks.reduce(
+      (previousText, nextDelta) =>
+        resolveMergedAssistantText({
+          previousText,
+          nextText: nextDelta,
+          nextDelta,
+        }),
+      "",
+    );
+
+    expect(merged).toBe(expected);
+  });
+
+  it("keeps cumulative snapshots from duplicating already-buffered text", () => {
+    expect(
+      resolveMergedAssistantText({
+        previousText: "Hello",
+        nextText: "Hello world",
+        nextDelta: " world",
+      }),
+    ).toBe("Hello world");
+  });
+
+  it("keeps non-prefix incremental segments after tool calls", () => {
+    expect(
+      resolveMergedAssistantText({
+        previousText: "Before tool call",
+        nextText: "After tool call",
+        nextDelta: "\nAfter tool call",
+      }),
+    ).toBe("Before tool call\nAfter tool call");
+  });
+
+  it("caps merged live text while preserving the newest assistant output", () => {
+    const result = resolveMergedAssistantText({
+      previousText: "a".repeat(MAX_LIVE_CHAT_BUFFER_CHARS - 2),
+      nextText: "",
+      nextDelta: "bbbb",
+    });
+
+    expect(result).toHaveLength(MAX_LIVE_CHAT_BUFFER_CHARS);
+    expect(result.endsWith("bbbb")).toBe(true);
+  });
+});