refactor(webui): shrink fork implementation

2026-06-10 04:26:06 +08:00
parent 1f926e3769
commit 916525f94a
24 changed files with 134 additions and 879 deletions
@@ -5,13 +5,13 @@ import {
  useRef,
  useState,
  type ReactNode,
-  type SVGProps,
 } from "react";
 import {
  Check,
  ChevronRight,
  Clock3,
  Copy,
+  GitFork,
  ImageIcon,
  Sparkles,
  Wrench,
@@ -22,12 +22,6 @@ import { AttachmentTile } from "@/components/AttachmentTile";
 import { CliAppMentionText } from "@/components/CliAppMentionText";
 import { ImageLightbox } from "@/components/ImageLightbox";
 import { MarkdownText, preloadMarkdownText } from "@/components/MarkdownText";
-import {
-  Tooltip,
-  TooltipContent,
-  TooltipProvider,
-  TooltipTrigger,
-} from "@/components/ui/tooltip";
 import { cn } from "@/lib/utils";
 import { copyTextToClipboard } from "@/lib/clipboard";
 import { formatTurnLatency } from "@/lib/format";
@@ -90,7 +84,7 @@ export function MessageBubble({
    };
  }, []);

-  const onCopyMessage = useCallback(() => {
+  const onCopyAssistantReply = useCallback(() => {
    void copyTextToClipboard(message.content).then((ok) => {
      if (!ok) return;
      setCopied(true);
@@ -114,11 +108,6 @@ export function MessageBubble({
    const hasImages = images.length > 0;
    const hasMedia = media.length > 0;
    const hasText = message.content.trim().length > 0;
-    const showUserActions = hasText;
-    const timeLabel = formatMessageClock(message.createdAt);
-    const copyLabel = copied
-      ? t("message.copiedMessage", { defaultValue: "Copied" })
-      : t("message.copyMessage", { defaultValue: "Copy" });
    return (
      <div
        className={cn(
@@ -144,43 +133,6 @@ export function MessageBubble({
            />
          </p>
        ) : null}
-        {showUserActions ? (
-          <TooltipProvider delayDuration={180} skipDelayDuration={80}>
-            <div
-              className={cn(
-                "mt-0.5 flex h-8 items-center justify-end gap-1 self-end",
-                "text-[13px] text-muted-foreground/65 opacity-0 transition-opacity duration-150",
-                "group-focus-within:opacity-100 group-hover:opacity-100",
-              )}
-            >
-              {hasText ? (
-                <MessageActionTooltip label={copyLabel}>
-                  <button
-                    type="button"
-                    onClick={onCopyMessage}
-                    aria-label={copyLabel}
-                    className={cn(
-                      "inline-flex h-7 w-7 shrink-0 items-center justify-center rounded-full",
-                      "transition-colors hover:bg-muted/55 hover:text-foreground",
-                      "focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring",
-                    )}
-                  >
-                    {copied ? (
-                      <Check className="h-3.5 w-3.5" aria-hidden />
-                    ) : (
-                      <Copy className="h-3.5 w-3.5" aria-hidden />
-                    )}
-                  </button>
-                </MessageActionTooltip>
-              ) : null}
-              {timeLabel ? (
-                <span className="ml-1 shrink-0 select-none tabular-nums" title={timeLabel}>
-                  {timeLabel}
-                </span>
-              ) : null}
-            </div>
-          </TooltipProvider>
-        ) : null}
      </div>
    );
  }
@@ -235,54 +187,50 @@ export function MessageBubble({
          </MarkdownText>
          {media.length > 0 ? <MessageMedia media={media} align="left" /> : null}
          {showAssistantFooterRow ? (
-            <TooltipProvider delayDuration={180} skipDelayDuration={80}>
-              <div className="mt-2 flex min-h-8 flex-wrap items-center gap-x-2 gap-y-1 text-muted-foreground">
-                {showCopyButton ? (
-                  <MessageActionTooltip label={copyReplyLabel}>
-                    <button
-                      type="button"
-                      onClick={onCopyMessage}
-                      aria-label={copyReplyLabel}
-                      className={cn(
-                        "inline-flex h-8 w-8 shrink-0 items-center justify-center rounded-full",
-                        "transition-colors hover:bg-muted/55 hover:text-foreground",
-                        "focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring",
-                      )}
-                    >
-                      {copied ? (
-                        <Check className="h-4 w-4" aria-hidden />
-                      ) : (
-                        <Copy className="h-4 w-4" aria-hidden />
-                      )}
-                    </button>
-                  </MessageActionTooltip>
-                ) : null}
-                {showForkButton ? (
-                  <MessageActionTooltip label={forkLabel}>
-                    <button
-                      type="button"
-                      onClick={onForkFromHere}
-                      aria-label={forkLabel}
-                      className={cn(
-                        "inline-flex h-8 w-8 shrink-0 items-center justify-center rounded-full",
-                        "transition-colors hover:bg-muted/55 hover:text-foreground",
-                        "focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring",
-                      )}
-                    >
-                      <ForkFromHereIcon className="h-4 w-4" aria-hidden />
-                    </button>
-                  </MessageActionTooltip>
-                ) : null}
-                {showLatencyFooter ? (
-                  <span
-                    className="text-[11px] leading-none text-muted-foreground/70 tabular-nums"
-                    title={t("message.turnLatencyTitle")}
-                  >
-                    {formatTurnLatency(latencyMs)}
-                  </span>
-                ) : null}
-              </div>
-            </TooltipProvider>
+            <div className="mt-2 flex min-h-8 flex-wrap items-center gap-x-2 gap-y-1 text-muted-foreground">
+              {showCopyButton ? (
+                <button
+                  type="button"
+                  onClick={onCopyAssistantReply}
+                  aria-label={copyReplyLabel}
+                  title={copyReplyLabel}
+                  className={cn(
+                    "inline-flex h-8 w-8 shrink-0 items-center justify-center rounded-full",
+                    "transition-colors hover:bg-muted/55 hover:text-foreground",
+                    "focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring",
+                  )}
+                >
+                  {copied ? (
+                    <Check className="h-4 w-4" aria-hidden />
+                  ) : (
+                    <Copy className="h-4 w-4" aria-hidden />
+                  )}
+                </button>
+              ) : null}
+              {showForkButton ? (
+                <button
+                  type="button"
+                  onClick={onForkFromHere}
+                  aria-label={forkLabel}
+                  title={forkLabel}
+                  className={cn(
+                    "inline-flex h-8 w-8 shrink-0 items-center justify-center rounded-full",
+                    "transition-colors hover:bg-muted/55 hover:text-foreground",
+                    "focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring",
+                  )}
+                >
+                  <GitFork className="h-4 w-4" aria-hidden />
+                </button>
+              ) : null}
+              {showLatencyFooter ? (
+                <span
+                  className="text-[11px] leading-none text-muted-foreground/70 tabular-nums"
+                  title={t("message.turnLatencyTitle")}
+                >
+                  {formatTurnLatency(latencyMs)}
+                </span>
+              ) : null}
+            </div>
          ) : null}
        </>
      )}
@@ -290,27 +238,6 @@ export function MessageBubble({
  );
 }

-function MessageActionTooltip({
-  label,
-  children,
-}: {
-  label: string;
-  children: ReactNode;
-}) {
-  return (
-    <Tooltip>
-      <TooltipTrigger asChild>{children}</TooltipTrigger>
-      <TooltipContent
-        side="top"
-        align="center"
-        className="rounded-full border-border/70 bg-background px-2.5 py-1 text-[12px] font-medium text-foreground shadow-[0_8px_24px_rgba(15,23,42,0.13)] dark:border-white/10 dark:bg-neutral-900 dark:text-white"
-      >
-        {label}
-      </TooltipContent>
-    </Tooltip>
-  );
-}
-
 function AutomationSourceBadge({ label, triggerLabel }: { label: string; triggerLabel: string }) {
  return (
    <div
@@ -330,39 +257,6 @@ function AutomationSourceBadge({ label, triggerLabel }: { label: string; trigger
  );
 }

-function formatMessageClock(createdAt: number): string {
-  if (!Number.isFinite(createdAt) || createdAt <= 0) return "";
-  try {
-    return new Intl.DateTimeFormat(undefined, {
-      hour: "2-digit",
-      minute: "2-digit",
-    }).format(new Date(createdAt));
-  } catch {
-    return "";
-  }
-}
-
-function ForkFromHereIcon({ className, ...props }: SVGProps<SVGSVGElement>) {
-  // Tabler Icons "arrow-fork" (MIT, Copyright Paweł Kuna).
-  return (
-    <svg
-      className={className}
-      viewBox="0 0 24 24"
-      fill="none"
-      stroke="currentColor"
-      strokeWidth="2"
-      strokeLinecap="round"
-      strokeLinejoin="round"
-      {...props}
-    >
-      <path d="M16 3h5v5" />
-      <path d="M8 3h-5v5" />
-      <path d="M21 3l-7.536 7.536a5 5 0 0 0 -1.464 3.534v6.93" />
-      <path d="M3 3l7.536 7.536a5 5 0 0 1 1.464 3.534v.93" />
-    </svg>
-  );
-}
-
 function mergeMcpMentionPresets(
  presets: McpPresetInfo[],
  attachments: UIMcpPresetAttachment[] | undefined,
@@ -172,7 +172,6 @@ interface ThreadComposerProps {
  workspaceError?: string | null;
  onWorkspaceScopeChange?: (scope: WorkspaceScopePayload) => void;
  pendingQueueKey?: string | null;
-  externalError?: string | null;
 }

 const COMMAND_ICONS: Record<string, LucideIcon> = {
@@ -766,7 +765,6 @@ export function ThreadComposer({
  workspaceError = null,
  onWorkspaceScopeChange,
  pendingQueueKey = null,
-  externalError = null,
 }: ThreadComposerProps) {
  const { t } = useTranslation();
  const [value, setValue] = useState("");
@@ -1149,10 +1147,6 @@ export function ThreadComposer({
    });
  }, [clear, pendingQueueKey]);

-  useEffect(() => {
-    if (externalError) setInlineError(externalError);
-  }, [externalError]);
-
  const appendTranscription = useCallback((text: string) => {
    const transcript = text.trim();
    if (!transcript) return;
@@ -8,10 +8,10 @@ import type { CliAppInfo, McpPresetInfo, UIMessage } from "@/lib/types";

 interface ThreadMessagesProps {
  messages: UIMessage[];
-  allMessages?: UIMessage[];
  /** When true, agent turn still in flight — keeps activity timeline expanded. */
  isStreaming?: boolean;
  hiddenMessageCount?: number;
+  hiddenUserMessageCount?: number;
  onLoadEarlier?: () => void;
  cliApps?: CliAppInfo[];
  mcpPresets?: McpPresetInfo[];
@@ -65,9 +65,9 @@ export function assistantCopyFlags(units: DisplayUnit[]): boolean[] {

 export function ThreadMessages({
  messages,
-  allMessages,
  isStreaming = false,
  hiddenMessageCount = 0,
+  hiddenUserMessageCount = 0,
  onLoadEarlier,
  cliApps = [],
  mcpPresets = [],
@@ -81,15 +81,12 @@ export function ThreadMessages({
    () => unitIndexAfterMessageCount(units, forkBoundaryMessageCount),
    [forkBoundaryMessageCount, units],
  );
-  const assistantForkIndexById = useMemo(
-    () => assistantForkIndexByMessageId(allMessages ?? messages),
-    [allMessages, messages],
-  );
  const copyFlags = useMemo(() => assistantCopyFlags(units), [units]);
  const liveActivityClusterIndices = useMemo(
    () => isStreaming ? currentActivityClusterIndices(units) : new Set<number>(),
    [isStreaming, units],
  );
+  let nextUserIndex = hiddenUserMessageCount;

  return (
    <div className="flex w-full flex-col">
@@ -123,6 +120,11 @@ export function ThreadMessages({
          unit.type === "message" && unit.message.role === "user"
            ? unit.message.id
            : undefined;
+        const forkIndex =
+          unit.type === "message" && unit.message.role === "assistant" && copyFlags[index]
+            ? nextUserIndex
+            : undefined;
+        if (unit.type === "message" && unit.message.role === "user") nextUserIndex += 1;

        return (
          <Fragment key={unitKey(unit, index)}>
@@ -149,20 +151,15 @@ export function ThreadMessages({
                  mcpPresets={mcpPresets}
                  onOpenFilePreview={onOpenFilePreview}
                  onForkFromHere={
-                    onForkFromMessage
-                      ? forkHandlerForAssistantMessage(
-                          unit.message,
-                          copyFlags[index],
-                          assistantForkIndexById,
-                          onForkFromMessage,
-                        )
+                    onForkFromMessage && forkIndex !== undefined
+                      ? () => onForkFromMessage(forkIndex)
                      : undefined
                  }
                />
              )}
            </div>
            {index === forkBoundaryAfterUnitIndex ? (
-              <ForkBoundaryDivider label={t("thread.fork.fromHistory")} />
+              <ForkBoundaryDivider label={t("thread.forkedFromHistory")} />
            ) : null}
          </Fragment>
        );
@@ -195,34 +192,6 @@ function ForkBoundaryDivider({ label }: { label: string }) {
  );
 }

-function assistantForkIndexByMessageId(messages: UIMessage[]): Map<string, number> {
-  const out = new Map<string, number>();
-  let nextUserIndex = 0;
-  for (const message of messages) {
-    if (message.role === "user") {
-      nextUserIndex += 1;
-    } else if (message.role === "assistant") {
-      out.set(message.id, nextUserIndex);
-    }
-  }
-  return out;
-}
-
-function forkHandlerForAssistantMessage(
-  message: UIMessage,
-  canForkAssistant: boolean,
-  assistantForkIndexById: Map<string, number>,
-  onForkFromMessage: NonNullable<ThreadMessagesProps["onForkFromMessage"]>,
-): (() => void) | undefined {
-  if (message.role === "assistant" && canForkAssistant) {
-    const beforeUserIndex = assistantForkIndexById.get(message.id);
-    return beforeUserIndex === undefined
-      ? undefined
-      : () => onForkFromMessage(beforeUserIndex);
-  }
-  return undefined;
-}
-
 function currentActivityClusterIndices(units: DisplayUnit[]): Set<number> {
  const indices = new Set<number>();
  let markedCurrentActivity = false;
@@ -278,8 +278,6 @@ export function ThreadShell({
  const [filePreviewPath, setFilePreviewPath] = useState<string | null>(null);
  const [filePreviewClosing, setFilePreviewClosing] = useState(false);
  const [filePreviewWidth, setFilePreviewWidth] = useState(FILE_PREVIEW_DEFAULT_WIDTH);
-  const [forkError, setForkError] = useState<string | null>(null);
-  const [forkHydratingChatId, setForkHydratingChatId] = useState<string | null>(null);
  const shellRef = useRef<HTMLElement | null>(null);
  const filePreviewWidthRef = useRef(FILE_PREVIEW_DEFAULT_WIDTH);
  const filePreviewCloseTimerRef = useRef<number | null>(null);
@@ -288,7 +286,6 @@ export function ThreadShell({
  const messageCacheRef = useRef<Map<string, UIMessage[]>>(new Map());
  /** Last chatId we associated with the in-memory thread (for cache-on-switch). */
  const prevChatIdForCacheRef = useRef<string | null>(null);
-  const prevChatIdForComposerRef = useRef<string | null>(chatId);
  /** Skip one message-cache write right after chatId changes (messages may not match yet). */
  const skipLayoutCacheRef = useRef(false);
  const appliedHistoryVersionRef = useRef<Map<string, number>>(new Map());
@@ -340,12 +337,6 @@ export function ThreadShell({
    };
  }, []);

-  useEffect(() => {
-    if (prevChatIdForComposerRef.current === chatId) return;
-    prevChatIdForComposerRef.current = chatId;
-    setForkError(null);
-  }, [chatId]);
-
  const displayMessages = useMemo(() => projectWebuiThreadMessages(messages), [messages]);

  const showHeroComposer = messages.length === 0 && !loading;
@@ -455,12 +446,6 @@ export function ThreadShell({
    setMessages(projectWebuiThreadMessages(historical));
  }, [chatId, historical, setMessages]);

-  useEffect(() => {
-    if (!chatId || loading || forkHydratingChatId !== chatId) return;
-    setForkHydratingChatId(null);
-    setScrollToBottomSignal((value) => value + 1);
-  }, [chatId, forkHydratingChatId, loading]);
-
  useLayoutEffect(() => {
    if (chatId) {
      const prev = prevChatIdForCacheRef.current;
@@ -539,7 +524,6 @@ export function ThreadShell({

  const handleThreadSend = useCallback(
    (content: string, images?: SendImage[], options?: SendOptions) => {
-      setForkError(null);
      setScrollToBottomSignal((value) => value + 1);
      send(content, images, withWorkspaceScope(options));
    },
@@ -637,21 +621,13 @@ export function ThreadShell({
  const handleForkFromMessage = useCallback(
    async (beforeUserIndex: number) => {
      if (!chatId || !onForkChat) return;
-      setForkError(null);
      const forkedChatId = await onForkChat(chatId, beforeUserIndex);
-      if (!forkedChatId) {
-        setForkError(t("thread.fork.failed", {
-          defaultValue: "Could not fork this chat. Try again.",
-        }));
-        return;
-      }
+      if (!forkedChatId) return;
      messageCacheRef.current.delete(forkedChatId);
      appliedHistoryVersionRef.current.delete(forkedChatId);
      pendingCanonicalHydrateRef.current.add(forkedChatId);
-      setForkHydratingChatId(forkedChatId);
-      setForkError(null);
    },
-    [chatId, onForkChat, t],
+    [chatId, onForkChat],
  );

  const composer = (
@@ -665,7 +641,7 @@ export function ThreadShell({
      {session ? (
        <ThreadComposer
          onSend={handleThreadSend}
-          disabled={!chatId || forkHydratingChatId === chatId}
+          disabled={!chatId}
          isStreaming={isStreaming}
          placeholder={
            showHeroComposer
@@ -692,7 +668,6 @@ export function ThreadShell({
          workspaceError={workspaceError}
          onWorkspaceScopeChange={onWorkspaceScopeChange}
          pendingQueueKey={chatId}
-          externalError={forkError}
        />
      ) : (
        <ThreadComposer
@@ -776,7 +751,6 @@ export function ThreadShell({
          showScrollToBottomButton={!!session}
          cliApps={cliApps}
          mcpPresets={mcpPresets}
-          allMessages={displayMessages}
          forkBoundaryMessageCount={forkBoundaryMessageCount}
          onOpenFilePreview={historyKey ? handleOpenFilePreview : undefined}
          onForkFromMessage={onForkChat ? handleForkFromMessage : undefined}
@@ -29,7 +29,6 @@ export interface ThreadViewportHandle {

 interface ThreadViewportProps {
  messages: UIMessage[];
-  allMessages?: UIMessage[];
  isStreaming: boolean;
  composer: ReactNode;
  emptyState?: ReactNode;
@@ -64,7 +63,6 @@ export function windowMessages(messages: UIMessage[], visibleCount: number): UIM

 export const ThreadViewport = forwardRef<ThreadViewportHandle, ThreadViewportProps>(function ThreadViewport({
  messages,
-  allMessages,
  isStreaming,
  composer,
  emptyState,
@@ -100,6 +98,10 @@ export const ThreadViewport = forwardRef<ThreadViewportHandle, ThreadViewportPro
    [messages, visibleMessageCount],
  );
  const hiddenMessageCount = messages.length - visibleMessages.length;
+  const hiddenUserMessageCount =
+    hiddenMessageCount > 0
+      ? messages.slice(0, hiddenMessageCount).filter((message) => message.role === "user").length
+      : 0;
  const visibleForkBoundaryMessageCount =
    forkBoundaryMessageCount !== null && forkBoundaryMessageCount > hiddenMessageCount
      ? forkBoundaryMessageCount - hiddenMessageCount
@@ -299,9 +301,9 @@ export const ThreadViewport = forwardRef<ThreadViewportHandle, ThreadViewportPro
              <div className="mx-auto w-full max-w-[49.5rem]">
                <ThreadMessages
                  messages={visibleMessages}
-                  allMessages={allMessages ?? messages}
                  isStreaming={isStreaming}
                  hiddenMessageCount={hiddenMessageCount}
+                  hiddenUserMessageCount={hiddenUserMessageCount}
                  onLoadEarlier={loadEarlierMessages}
                  cliApps={cliApps}
                  mcpPresets={mcpPresets}
@@ -811,10 +811,7 @@
    },
    "scrollToBottom": "Scroll to bottom",
    "loadEarlier": "Load earlier messages",
-    "fork": {
-      "failed": "Could not fork this chat. Try again.",
-      "fromHistory": "Forked from history"
-    },
+    "forkedFromHistory": "Forked from history",
    "promptNavigator": {
      "open": "Open prompt navigator",
      "title": "Prompts",
@@ -854,8 +851,6 @@
    "imageAttachment": "Image attachment",
    "automationSourceFallback": "Automation",
    "automationTriggered": "Triggered automatically",
-    "copyMessage": "Copy",
-    "copiedMessage": "Copied",
    "forkFromHere": "Fork",
    "copyReply": "Copy",
    "copiedReply": "Copied",
@@ -811,10 +811,7 @@
    },
    "scrollToBottom": "Desplazarse al final",
    "loadEarlier": "Cargar mensajes anteriores",
-    "fork": {
-      "failed": "No se pudo bifurcar este chat. Inténtalo de nuevo.",
-      "fromHistory": "Bifurcado desde el historial"
-    },
+    "forkedFromHistory": "Bifurcado desde el historial",
    "promptNavigator": {
      "open": "Abrir navegador de prompts",
      "title": "Prompts",
@@ -840,8 +837,6 @@
    "agentActivityLiveSummary": "En curso… · {{reasoning}} pasos · {{tools}} llamadas a herramientas",
    "agentActivityLiveToolsOnly": "En curso… · {{tools}} llamadas a herramientas",
    "imageAttachment": "Imagen adjunta",
-    "copyMessage": "Copiar",
-    "copiedMessage": "Copiado",
    "forkFromHere": "Bifurcar",
    "copyReply": "Copiar",
    "copiedReply": "Copiado",
@@ -811,10 +811,7 @@
    },
    "scrollToBottom": "Faire défiler vers le bas",
    "loadEarlier": "Charger les messages précédents",
-    "fork": {
-      "failed": "Impossible de bifurquer cette conversation. Réessayez.",
-      "fromHistory": "Bifurqué depuis l'historique"
-    },
+    "forkedFromHistory": "Bifurqué depuis l'historique",
    "promptNavigator": {
      "open": "Ouvrir le navigateur de prompts",
      "title": "Prompts",
@@ -840,8 +837,6 @@
    "agentActivityLiveSummary": "En cours… · {{reasoning}} étapes · {{tools}} appels d’outils",
    "agentActivityLiveToolsOnly": "En cours… · {{tools}} appels d’outils",
    "imageAttachment": "Pièce jointe image",
-    "copyMessage": "Copier",
-    "copiedMessage": "Copié",
    "forkFromHere": "Bifurquer",
    "copyReply": "Copier",
    "copiedReply": "Copié",
@@ -811,10 +811,7 @@
    },
    "scrollToBottom": "Gulir ke bawah",
    "loadEarlier": "Muat pesan sebelumnya",
-    "fork": {
-      "failed": "Tidak dapat mem-fork chat ini. Coba lagi.",
-      "fromHistory": "Fork dari riwayat"
-    },
+    "forkedFromHistory": "Fork dari riwayat",
    "promptNavigator": {
      "open": "Buka navigator prompt",
      "title": "Prompt",
@@ -840,8 +837,6 @@
    "agentActivityLiveSummary": "Berjalan… · {{reasoning}} langkah · {{tools}} panggilan alat",
    "agentActivityLiveToolsOnly": "Berjalan… · {{tools}} panggilan alat",
    "imageAttachment": "Lampiran gambar",
-    "copyMessage": "Salin",
-    "copiedMessage": "Disalin",
    "forkFromHere": "Fork",
    "copyReply": "Salin",
    "copiedReply": "Disalin",
@@ -811,10 +811,7 @@
    },
    "scrollToBottom": "一番下へスクロール",
    "loadEarlier": "以前のメッセージを読み込む",
-    "fork": {
-      "failed": "このチャットを分岐できませんでした。もう一度お試しください。",
-      "fromHistory": "履歴から分岐"
-    },
+    "forkedFromHistory": "履歴から分岐",
    "promptNavigator": {
      "open": "プロンプトナビゲーターを開く",
      "title": "プロンプト",
@@ -840,8 +837,6 @@
    "agentActivityLiveSummary": "実行中… · {{reasoning}} ステップ · ツール呼び出し {{tools}} 回",
    "agentActivityLiveToolsOnly": "実行中… · ツール呼び出し {{tools}} 回",
    "imageAttachment": "画像の添付",
-    "copyMessage": "コピー",
-    "copiedMessage": "コピー済み",
    "forkFromHere": "分岐",
    "copyReply": "コピー",
    "copiedReply": "コピー済み",
@@ -811,10 +811,7 @@
    },
    "scrollToBottom": "맨 아래로 스크롤",
    "loadEarlier": "이전 메시지 불러오기",
-    "fork": {
-      "failed": "이 채팅을 분기할 수 없습니다. 다시 시도해 주세요.",
-      "fromHistory": "기록에서 분기됨"
-    },
+    "forkedFromHistory": "기록에서 분기됨",
    "promptNavigator": {
      "open": "프롬프트 탐색기 열기",
      "title": "프롬프트",
@@ -840,8 +837,6 @@
    "agentActivityLiveSummary": "진행 중… · {{reasoning}}단계 · 도구 호출 {{tools}}회",
    "agentActivityLiveToolsOnly": "진행 중… · 도구 호출 {{tools}}회",
    "imageAttachment": "이미지 첨부",
-    "copyMessage": "복사",
-    "copiedMessage": "복사됨",
    "forkFromHere": "분기",
    "copyReply": "복사",
    "copiedReply": "복사됨",
@@ -811,10 +811,7 @@
    },
    "scrollToBottom": "Cuộn xuống cuối",
    "loadEarlier": "Tải tin nhắn trước đó",
-    "fork": {
-      "failed": "Không thể rẽ nhánh cuộc trò chuyện này. Hãy thử lại.",
-      "fromHistory": "Tách nhánh từ lịch sử"
-    },
+    "forkedFromHistory": "Tách nhánh từ lịch sử",
    "promptNavigator": {
      "open": "Mở trình điều hướng prompt",
      "title": "Prompt",
@@ -840,8 +837,6 @@
    "agentActivityLiveSummary": "Đang chạy… · {{reasoning}} bước · {{tools}} lần gọi công cụ",
    "agentActivityLiveToolsOnly": "Đang chạy… · {{tools}} lần gọi công cụ",
    "imageAttachment": "Tệp hình ảnh đính kèm",
-    "copyMessage": "Sao chép",
-    "copiedMessage": "Đã sao chép",
    "forkFromHere": "Tách nhánh",
    "copyReply": "Sao chép",
    "copiedReply": "Đã sao chép",
@@ -811,10 +811,7 @@
    },
    "scrollToBottom": "滚动到底部",
    "loadEarlier": "加载更早消息",
-    "fork": {
-      "failed": "无法分叉这个对话，请重试。",
-      "fromHistory": "从历史消息分叉"
-    },
+    "forkedFromHistory": "从历史消息分叉",
    "promptNavigator": {
      "open": "打开输入导航",
      "title": "输入列表",
@@ -854,8 +851,6 @@
    "imageAttachment": "图片附件",
    "automationSourceFallback": "自动化",
    "automationTriggered": "自动触发",
-    "copyMessage": "复制",
-    "copiedMessage": "已复制",
    "forkFromHere": "分叉",
    "copyReply": "复制",
    "copiedReply": "已复制",
@@ -811,10 +811,7 @@
    },
    "scrollToBottom": "捲動到底部",
    "loadEarlier": "載入更早訊息",
-    "fork": {
-      "failed": "無法分叉這個對話，請重試。",
-      "fromHistory": "從歷史訊息分叉"
-    },
+    "forkedFromHistory": "從歷史訊息分叉",
    "promptNavigator": {
      "open": "開啟輸入導覽",
      "title": "輸入列表",
@@ -840,8 +837,6 @@
    "agentActivityLiveSummary": "進行中… · {{reasoning}} 步 · {{tools}} 次工具呼叫",
    "agentActivityLiveToolsOnly": "進行中… · {{tools}} 次工具呼叫",
    "imageAttachment": "圖片附件",
-    "copyMessage": "複製",
-    "copiedMessage": "已複製",
    "forkFromHere": "分叉",
    "copyReply": "複製",
    "copiedReply": "已複製",
@@ -76,22 +76,6 @@ describe("MessageBubble", () => {

    expect(row).toHaveClass("ml-auto", "flex");
    expect(pill).toHaveClass("ml-auto", "w-fit", "rounded-[18px]");
-    expect(screen.getByRole("button", { name: "Copy" })).toBeInTheDocument();
-    expect(screen.queryByRole("button", { name: "Fork" })).not.toBeInTheDocument();
-  });
-
-  it("does not render fork control for user messages", () => {
-    const onForkFromHere = vi.fn();
-    const message: UIMessage = {
-      id: "u-fork",
-      role: "user",
-      content: "continue from here",
-      createdAt: new Date("2026-06-06T09:04:00Z").getTime(),
-    };
-
-    render(<MessageBubble message={message} onForkFromHere={onForkFromHere} />);
-
-    expect(screen.getByRole("button", { name: "Copy" })).toBeInTheDocument();
    expect(screen.queryByRole("button", { name: "Fork" })).not.toBeInTheDocument();
  });

@@ -766,223 +766,6 @@ describe("ThreadShell", () => {
    );
  });

-  it("shows an error without changing the draft when assistant fork fails", async () => {
-    const client = makeClient();
-    const onForkChat = vi.fn().mockResolvedValue(null);
-    vi.stubGlobal(
-      "fetch",
-      vi.fn(async (input: RequestInfo | URL) => {
-        const url = String(input);
-        if (url.includes("websocket%3Achat-a/webui-thread")) {
-          return httpJson(transcriptFromSimpleMessages([
-            { role: "user", content: "fork me" },
-            { role: "assistant", content: "answer" },
-          ]));
-        }
-        return {
-          ok: false,
-          status: 404,
-          json: async () => ({}),
-        };
-      }),
-    );
-
-    render(
-      wrap(
-        client,
-        <ThreadShell
-          session={session("chat-a")}
-          title="Chat chat-a"
-          onToggleSidebar={() => {}}
-          onForkChat={onForkChat}
-        />,
-      ),
-    );
-
-    const targetText = await screen.findByText("answer");
-    fireEvent.change(screen.getByLabelText("Message input"), {
-      target: { value: "keep my current draft" },
-    });
-    fireEvent.click(within(targetText.closest(".w-full") as HTMLElement).getByRole("button", {
-      name: "Fork",
-    }));
-
-    await waitFor(() => expect(onForkChat).toHaveBeenCalledWith("chat-a", 1));
-    expect(screen.getByLabelText("Message input")).toHaveValue("keep my current draft");
-    expect(screen.getByRole("alert")).toHaveTextContent("Could not fork this chat");
-    expect(client.sendMessage).not.toHaveBeenCalled();
-  });
-
-  it("hydrates a successful fork from canonical history without later source messages", async () => {
-    const client = makeClient();
-    const onForkChat = vi.fn().mockResolvedValue("chat-fork");
-    vi.stubGlobal(
-      "fetch",
-      vi.fn(async (input: RequestInfo | URL) => {
-        const url = String(input);
-        if (url.includes("websocket%3Achat-a/webui-thread")) {
-          return httpJson(transcriptFromSimpleMessages([
-            { role: "user", content: "round1" },
-            { role: "assistant", content: "answer1" },
-            { role: "user", content: "round2 fork me" },
-            { role: "assistant", content: "answer2" },
-            { role: "user", content: "round3 must not appear" },
-          ]));
-        }
-        if (url.includes("websocket%3Achat-fork/webui-thread")) {
-          return httpJson(transcriptFromSimpleMessages([
-            { role: "user", content: "round1" },
-            { role: "assistant", content: "answer1" },
-            { role: "user", content: "round2 fork me" },
-            { role: "assistant", content: "answer2" },
-          ]));
-        }
-        if (url.includes("websocket%3Achat-other/webui-thread")) {
-          return httpJson(transcriptFromSimpleMessages([
-            { role: "user", content: "other chat" },
-          ]));
-        }
-        return {
-          ok: false,
-          status: 404,
-          json: async () => ({}),
-        };
-      }),
-    );
-
-    const { rerender } = render(
-      wrap(
-        client,
-        <ThreadShell
-          session={session("chat-a")}
-          title="Chat chat-a"
-          onToggleSidebar={() => {}}
-          onForkChat={onForkChat}
-        />,
-      ),
-    );
-
-    const targetText = await screen.findByText("answer2");
-    fireEvent.click(within(targetText.closest(".w-full") as HTMLElement).getByRole("button", {
-      name: "Fork",
-    }));
-
-    await waitFor(() => expect(onForkChat).toHaveBeenCalledWith("chat-a", 2));
-    await act(async () => {
-      rerender(
-        wrap(
-          client,
-          <ThreadShell
-            session={session("chat-fork")}
-            title="Chat chat-fork"
-            onToggleSidebar={() => {}}
-            onForkChat={onForkChat}
-          />,
-        ),
-      );
-    });
-
-    await waitFor(() => expect(screen.getByText("answer1")).toBeInTheDocument());
-    expect(screen.getByText("answer2")).toBeInTheDocument();
-    expect(screen.queryByText("round3 must not appear")).not.toBeInTheDocument();
-    expect(screen.getByLabelText("Message input")).toHaveValue("");
-
-    await act(async () => {
-      rerender(
-        wrap(
-          client,
-          <ThreadShell
-            session={session("chat-other")}
-            title="Chat chat-other"
-            onToggleSidebar={() => {}}
-            onForkChat={onForkChat}
-          />,
-        ),
-      );
-    });
-
-    await waitFor(() =>
-      expect(screen.getByLabelText("Message input")).toHaveValue(""),
-    );
-
-    await act(async () => {
-      rerender(
-        wrap(
-          client,
-          <ThreadShell
-            session={null}
-            title="New chat"
-            onToggleSidebar={() => {}}
-            onForkChat={onForkChat}
-          />,
-        ),
-      );
-    });
-
-    expect(screen.getByLabelText("Message input")).toHaveValue("");
-  });
-
-  it("forks from completed assistant replies without pre-filling the assistant text", async () => {
-    const client = makeClient();
-    const onForkChat = vi.fn().mockResolvedValue("chat-fork");
-    vi.stubGlobal(
-      "fetch",
-      vi.fn(async (input: RequestInfo | URL) => {
-        const url = String(input);
-        if (url.includes("websocket%3Achat-a/webui-thread")) {
-          return httpJson(transcriptFromSimpleMessages([
-            { role: "user", content: "round1" },
-            { role: "assistant", content: "answer1" },
-          ]));
-        }
-        if (url.includes("websocket%3Achat-fork/webui-thread")) {
-          return httpJson(transcriptFromSimpleMessages([
-            { role: "user", content: "round1" },
-            { role: "assistant", content: "answer1" },
-          ]));
-        }
-        return {
-          ok: false,
-          status: 404,
-          json: async () => ({}),
-        };
-      }),
-    );
-
-    const { rerender } = render(
-      wrap(
-        client,
-        <ThreadShell
-          session={session("chat-a")}
-          title="Chat chat-a"
-          onToggleSidebar={() => {}}
-          onForkChat={onForkChat}
-        />,
-      ),
-    );
-
-    await screen.findByText("answer1");
-    fireEvent.click(screen.getAllByRole("button", { name: "Fork" }).at(-1)!);
-
-    await waitFor(() => expect(onForkChat).toHaveBeenCalledWith("chat-a", 1));
-    await act(async () => {
-      rerender(
-        wrap(
-          client,
-          <ThreadShell
-            session={session("chat-fork")}
-            title="Chat chat-fork"
-            onToggleSidebar={() => {}}
-            onForkChat={onForkChat}
-          />,
-        ),
-      );
-    });
-
-    await waitFor(() => expect(screen.getByText("answer1")).toBeInTheDocument());
-    expect(screen.getByLabelText("Message input")).toHaveValue("");
-  });
-
  it("does not cache optimistic messages under the next chat during a session switch", async () => {
    const client = makeClient();
    const onNewChat = vi.fn().mockResolvedValue("chat-b");
@@ -230,24 +230,6 @@ describe("useSessions", () => {
    expect(result.current.sessions[0]?.workspaceScope).toEqual(workspaceScope);
  });

-  it("keeps a fork title visible while the server session list catches up", async () => {
-    vi.mocked(api.listSessions).mockResolvedValue([]);
-    const client = fakeClient();
-    client.forkChat.mockResolvedValue("chat-fork");
-
-    const { result } = renderHook(() => useSessions(), {
-      wrapper: wrap(client),
-    });
-
-    await waitFor(() => expect(result.current.loading).toBe(false));
-    await act(async () => {
-      await result.current.forkChat("source", 2, "Fork: Original title");
-    });
-
-    expect(client.forkChat).toHaveBeenCalledWith("source", 2, "Fork: Original title");
-    expect(result.current.sessions[0]?.title).toBe("Fork: Original title");
-  });
-
  it("passes through WebUI transcript user media as images and media", async () => {
    vi.mocked(api.fetchWebuiThread).mockResolvedValue({
      schemaVersion: 3,