refactor(webui): shrink fork implementation

THIRD_PARTY_NOTICES.md

@@ -5,37 +5,6 @@ nanobot Python distribution (`pip install nanobot-ai`).
 
 ---
 
-## Tabler Icons — WebUI fork action icon (MIT)
-
-- **Source**: https://github.com/tabler/tabler-icons
-- **Bundled**: inline SVG path for `arrow-fork` in `nanobot/web/dist/assets/index-*.js`
-
-```
-The MIT License (MIT)
-
-Copyright (c) 2020-2026 Paweł Kuna
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
-```
-
----
-
 ## KaTeX — math rendering (MIT)
 
 - **Source**: https://github.com/KaTeX/KaTeX

nanobot/channels/websocket.py

@@ -696,22 +696,23 @@ class WebSocketChannel(BaseChannel):
                 if forked is None:
                     await self._send_event(connection, "error", detail="invalid fork source or index")
                     return
+                fork_id, fork_key = forked
             except Exception as exc:
                 self.logger.warning("fork_chat failed: {}", exc)
                 await self._send_event(connection, "error", detail="fork_chat_failed")
                 return
 
-            scope = self._workspaces.scope_for_session_key(forked.session_key)
+            scope = self._workspaces.scope_for_session_key(fork_key)
-            self._attach(connection, forked.chat_id)
+            self._attach(connection, fork_id)
-            await self._send_event(connection, "attached", chat_id=forked.chat_id)
+            await self._send_event(connection, "attached", chat_id=fork_id)
             await self._send_event(
                 connection,
                 "session_updated",
-                chat_id=forked.chat_id,
+                chat_id=fork_id,
                 scope="metadata",
                 workspace_scope=scope.payload(),
             )
-            await self._hydrate_after_subscribe(forked.chat_id)
+            await self._hydrate_after_subscribe(fork_id)
             return
         if t == "attach":
             cid = envelope.get("chat_id")

nanobot/webui/forking.py

@@ -1,14 +1,8 @@
-"""Helpers for WebUI chat forking.
+"""WebUI chat fork orchestration."""
-
-The WebSocket channel owns transport concerns only. This module owns the
-WebUI-specific session/transcript work needed to make a fork look like a normal
-chat in both browser WebUI and desktop.
-"""
 
 from __future__ import annotations
 
 import uuid
-from dataclasses import dataclass
 
 from nanobot.session.manager import SessionManager
 from nanobot.session.webui_turns import WEBUI_TITLE_METADATA_KEY, clean_generated_title
@@ -20,25 +14,14 @@ from nanobot.webui.transcript import (
 )
 
 
-@dataclass(frozen=True)
-class WebuiForkResult:
-    chat_id: str
-    session_key: str
-
-
 def create_webui_chat_fork(
     session_manager: SessionManager,
     *,
     source_chat_id: str,
     before_user_index: int,
     title: str | None = None,
-) -> WebuiForkResult | None:
+) -> tuple[str, str] | None:
-    """Create a WebUI chat fork from a completed assistant-turn boundary.
+    """Return ``(chat_id, session_key)`` for a new fork, or ``None`` for bad input."""
-
-    Returns ``None`` when the source/index is invalid. Exceptions are reserved
-    for unexpected I/O or persistence failures and are rolled back before being
-    re-raised.
-    """
     new_id = str(uuid.uuid4())
     source_key = f"websocket:{source_chat_id}"
     target_key = f"websocket:{new_id}"
@@ -68,4 +51,4 @@ def create_webui_chat_fork(
         delete_webui_transcript(target_key)
         session_manager.delete_session(target_key)
         raise
-    return WebuiForkResult(chat_id=new_id, session_key=target_key)
+    return new_id, target_key

nanobot/webui/transcript.py

@@ -286,6 +286,25 @@ def _is_user_transcript_row(row: dict[str, Any]) -> bool:
     return row.get("event") == "user" or row.get("role") == "user"
 
 
+def _write_transcript_lines(session_key: str, rows: list[dict[str, Any]]) -> None:
+    path = webui_transcript_path(session_key)
+    path.parent.mkdir(parents=True, exist_ok=True)
+    tmp_path = path.with_suffix(".jsonl.tmp")
+    try:
+        with open(tmp_path, "w", encoding="utf-8") as f:
+            for row in rows:
+                raw = json.dumps(row, ensure_ascii=False, separators=(",", ":"))
+                if len(raw.encode("utf-8")) > _MAX_TRANSCRIPT_FILE_BYTES:
+                    raise ValueError("webui transcript line too large")
+                f.write(raw + "\n")
+            f.flush()
+            os.fsync(f.fileno())
+        os.replace(tmp_path, path)
+    except BaseException:
+        tmp_path.unlink(missing_ok=True)
+        raise
+
+
 def fork_transcript_before_user_index(
     source_key: str,
     target_key: str,
@@ -324,22 +343,7 @@ def fork_transcript_before_user_index(
     if not found_target:
         return False
 
-    path = webui_transcript_path(target_key)
+    _write_transcript_lines(target_key, copied)
-    path.parent.mkdir(parents=True, exist_ok=True)
-    tmp_path = path.with_suffix(".jsonl.tmp")
-    try:
-        with open(tmp_path, "w", encoding="utf-8") as f:
-            for row in copied:
-                raw = json.dumps(row, ensure_ascii=False, separators=(",", ":"))
-                if len(raw.encode("utf-8")) > _MAX_TRANSCRIPT_FILE_BYTES:
-                    raise ValueError("webui transcript line too large")
-                f.write(raw + "\n")
-            f.flush()
-            os.fsync(f.fileno())
-        os.replace(tmp_path, path)
-    except BaseException:
-        tmp_path.unlink(missing_ok=True)
-        raise
     return True
 
 
@@ -360,51 +364,29 @@ def write_session_messages_as_transcript(
 ) -> None:
     """Write a minimal WebUI transcript from already-truncated session messages."""
     target_chat_id = _chat_id_from_session_key(target_key)
-    path = webui_transcript_path(target_key)
+    rows: list[dict[str, Any]] = []
-    path.parent.mkdir(parents=True, exist_ok=True)
+    for msg in messages:
-    tmp_path = path.with_suffix(".jsonl.tmp")
+        role = msg.get("role")
-    try:
+        content = msg.get("content")
-        with open(tmp_path, "w", encoding="utf-8") as f:
+        text = content if isinstance(content, str) else ""
-            for msg in messages:
+        if role == "user":
-                role = msg.get("role")
+            row: dict[str, Any] = {"event": "user", "chat_id": target_chat_id, "text": text}
-                content = msg.get("content")
+            media = msg.get("media")
-                text = content if isinstance(content, str) else ""
+            if isinstance(media, list) and media:
-                if role == "user":
+                row["media_paths"] = [str(p) for p in media if isinstance(p, str) and p]
-                    row: dict[str, Any] = {
+            for key in ("cli_apps", "mcp_presets"):
-                        "event": "user",
+                value = msg.get(key)
-                        "chat_id": target_chat_id,
+                if isinstance(value, list) and value:
-                        "text": text,
+                    row[key] = json.loads(json.dumps(value, ensure_ascii=False))
-                    }
+        elif role == "assistant" and text.strip():
-                    media = msg.get("media")
+            row = {"event": "message", "chat_id": target_chat_id, "text": text}
-                    if isinstance(media, list) and media:
+            media = msg.get("media")
-                        row["media_paths"] = [str(p) for p in media if isinstance(p, str) and p]
+            if isinstance(media, list) and media:
-                    for key in ("cli_apps", "mcp_presets"):
+                row["media"] = [str(p) for p in media if isinstance(p, str) and p]
-                        value = msg.get(key)
+        else:
-                        if isinstance(value, list) and value:
+            continue
-                            row[key] = json.loads(json.dumps(value, ensure_ascii=False))
+        rows.append(row)
-                elif role == "assistant":
+    _write_transcript_lines(target_key, rows)
-                    if not text.strip():
-                        continue
-                    row = {
-                        "event": "message",
-                        "chat_id": target_chat_id,
-                        "text": text,
-                    }
-                    media = msg.get("media")
-                    if isinstance(media, list) and media:
-                        row["media"] = [str(p) for p in media if isinstance(p, str) and p]
-                else:
-                    continue
-                raw = json.dumps(row, ensure_ascii=False, separators=(",", ":"))
-                if len(raw.encode("utf-8")) > _MAX_TRANSCRIPT_FILE_BYTES:
-                    raise ValueError("webui transcript line too large")
-                f.write(raw + "\n")
-            f.flush()
-            os.fsync(f.fileno())
-        os.replace(tmp_path, path)
-    except BaseException:
-        tmp_path.unlink(missing_ok=True)
-        raise
 
 
 def delete_webui_transcript(session_key: str) -> bool:
@@ -1411,25 +1393,12 @@ def replay_transcript_to_ui_messages(
     return messages
 
 
-def fork_boundary_message_count(
+def fork_boundary_message_count(lines: list[dict[str, Any]]) -> int | None:
-    lines: list[dict[str, Any]],
-    *,
-    augment_user_media: Callable[[list[str]], list[dict[str, Any]]] | None = None,
-    augment_assistant_media: Callable[[list[str]], list[dict[str, Any]]] | None = None,
-    augment_assistant_text: Callable[[str], str] | None = None,
-) -> int | None:
     """Return the replayed UI message count before the first fork marker, if any."""
     for idx, rec in enumerate(lines):
         if rec.get("event") != WEBUI_FORK_MARKER_EVENT:
             continue
-        return len(
+        return len(replay_transcript_to_ui_messages(lines[:idx]))
-            replay_transcript_to_ui_messages(
-                lines[:idx],
-                augment_user_media=augment_user_media,
-                augment_assistant_media=augment_assistant_media,
-                augment_assistant_text=augment_assistant_text,
-            ),
-        )
     return None
 
 
@@ -1446,12 +1415,7 @@ def build_webui_thread_response(
     if not lines:
         return None
     lines = inject_missing_user_events_from_session(session_key, lines, session_messages)
-    fork_boundary = fork_boundary_message_count(
+    fork_boundary = fork_boundary_message_count(lines)
-        lines,
-        augment_user_media=augment_user_media,
-        augment_assistant_media=augment_assistant_media,
-        augment_assistant_text=augment_assistant_text,
-    )
     msgs = replay_transcript_to_ui_messages(
         lines,
         augment_user_media=augment_user_media,

tests/agent/test_session_manager_history.py

@@ -454,34 +454,6 @@ def test_fork_session_before_user_index_copies_only_prefix(tmp_path):
     assert [m["content"] for m in saved["messages"]] == ["round1", "answer1"]
 
 
-def test_fork_session_from_middle_assistant_reply_keeps_selected_turn(tmp_path):
-    manager = SessionManager(tmp_path)
-    source = manager.get_or_create("websocket:source")
-    source.add_message("user", "round1")
-    source.add_message("assistant", "answer1")
-    source.add_message("user", "round2")
-    source.add_message("assistant", "answer2")
-    source.add_message("user", "round3 must not appear")
-    source.add_message("assistant", "answer3 must not appear")
-    manager.save(source)
-
-    forked = manager.fork_session_before_user_index(
-        "websocket:source",
-        "websocket:fork",
-        2,
-    )
-
-    assert forked is not None
-    assert [m["content"] for m in forked.messages] == [
-        "round1",
-        "answer1",
-        "round2",
-        "answer2",
-    ]
-    saved = manager.read_session_file("websocket:fork")
-    assert "round3 must not appear" not in str(saved)
-
-
 def test_fork_session_rejects_negative_missing_and_out_of_range(tmp_path):
     manager = SessionManager(tmp_path)
     source = manager.get_or_create("websocket:source")

tests/channels/test_websocket_channel.py

@@ -2398,17 +2398,12 @@ async def test_fork_chat_copies_only_prefix_session_and_transcript(
     source.metadata["webui"] = True
     source.add_message("user", "round1")
     source.add_message("assistant", "answer1")
-    source.add_message("user", "round2 fork me")
+    source.add_message("user", "future")
-    source.add_message("assistant", "answer2")
-    source.add_message("user", "round3 must not appear")
     sessions.save(source)
     for ev in (
         {"event": "user", "chat_id": "source", "text": "round1"},
         {"event": "message", "chat_id": "source", "text": "answer1"},
-        {"event": "turn_end", "chat_id": "source"},
+        {"event": "user", "chat_id": "source", "text": "future"},
-        {"event": "user", "chat_id": "source", "text": "round2 fork me"},
-        {"event": "message", "chat_id": "source", "text": "answer2"},
-        {"event": "user", "chat_id": "source", "text": "round3 must not appear"},
     ):
         append_transcript_object("websocket:source", ev)
 
@@ -2437,133 +2432,12 @@ async def test_fork_chat_copies_only_prefix_session_and_transcript(
     assert [m["content"] for m in saved["messages"]] == ["round1", "answer1"]
     assert saved["metadata"]["title"] == "Fork: Old title"
     fork_lines = read_transcript_lines(f"websocket:{fork_id}")
-    assert [line.get("text") for line in fork_lines] == ["round1", "answer1", None, None]
+    assert [line.get("text") for line in fork_lines] == ["round1", "answer1", None]
     assert fork_lines[-1]["event"] == "fork_marker"
     assert all(line.get("chat_id") == fork_id for line in fork_lines)
-    assert "round3 must not appear" not in json.dumps(saved, ensure_ascii=False)
+    assert "future" not in json.dumps(saved, ensure_ascii=False)
     bus.publish_inbound.assert_not_awaited()
 
-
-@pytest.mark.asyncio
-async def test_fork_chat_falls_back_to_session_prefix_when_transcript_lacks_user_rows(
-    bus: MagicMock,
-    tmp_path,
-    monkeypatch: pytest.MonkeyPatch,
-) -> None:
-    monkeypatch.setattr("nanobot.config.paths.get_data_dir", lambda: tmp_path)
-    sessions = SessionManager(tmp_path / "sessions")
-    source = sessions.get_or_create("websocket:source")
-    source.metadata["webui"] = True
-    source.add_message("user", "round1")
-    source.add_message("assistant", "answer1")
-    source.add_message("user", "round2 fork me")
-    source.add_message("assistant", "answer2")
-    source.add_message("user", "round3 must not appear")
-    sessions.save(source)
-    append_transcript_object(
-        "websocket:source",
-        {"event": "message", "chat_id": "source", "text": "answer1"},
-    )
-
-    channel = WebSocketChannel(
-        {"enabled": True, "allowFrom": ["*"], "host": "127.0.0.1"},
-        bus,
-        gateway=_basic_handler(bus, session_manager=sessions, workspace_path=tmp_path),
-    )
-    conn = AsyncMock()
-
-    await channel._dispatch_envelope(
-        conn,
-        "webui-client",
-        {"type": "fork_chat", "source_chat_id": "source", "before_user_index": 1},
-    )
-
-    sent = [json.loads(call.args[0]) for call in conn.send.await_args_list]
-    attached = next(item for item in sent if item["event"] == "attached")
-    fork_id = attached["chat_id"]
-    saved = sessions.read_session_file(f"websocket:{fork_id}")
-    assert [m["content"] for m in saved["messages"]] == ["round1", "answer1"]
-    fork_lines = read_transcript_lines(f"websocket:{fork_id}")
-    assert [line.get("text") for line in fork_lines] == ["round1", "answer1", None]
-    assert fork_lines[-1]["event"] == "fork_marker"
-    assert "round3 must not appear" not in json.dumps(fork_lines, ensure_ascii=False)
-    bus.publish_inbound.assert_not_awaited()
-
-
-@pytest.mark.asyncio
-async def test_fork_chat_allows_index_equal_to_user_count(
-    bus: MagicMock,
-    tmp_path,
-    monkeypatch: pytest.MonkeyPatch,
-) -> None:
-    monkeypatch.setattr("nanobot.config.paths.get_data_dir", lambda: tmp_path)
-    sessions = SessionManager(tmp_path / "sessions")
-    source = sessions.get_or_create("websocket:source")
-    source.metadata["webui"] = True
-    source.add_message("user", "round1")
-    source.add_message("assistant", "answer1")
-    sessions.save(source)
-    append_transcript_object("websocket:source", {"event": "user", "chat_id": "source", "text": "round1"})
-    append_transcript_object(
-        "websocket:source",
-        {"event": "message", "chat_id": "source", "text": "answer1"},
-    )
-
-    channel = WebSocketChannel(
-        {"enabled": True, "allowFrom": ["*"], "host": "127.0.0.1"},
-        bus,
-        gateway=_basic_handler(bus, session_manager=sessions, workspace_path=tmp_path),
-    )
-    conn = AsyncMock()
-
-    await channel._dispatch_envelope(
-        conn,
-        "webui-client",
-        {"type": "fork_chat", "source_chat_id": "source", "before_user_index": 1},
-    )
-
-    sent = [json.loads(call.args[0]) for call in conn.send.await_args_list]
-    attached = next(item for item in sent if item["event"] == "attached")
-    fork_id = attached["chat_id"]
-    saved = sessions.read_session_file(f"websocket:{fork_id}")
-    assert [m["content"] for m in saved["messages"]] == ["round1", "answer1"]
-    fork_lines = read_transcript_lines(f"websocket:{fork_id}")
-    assert [line.get("text") for line in fork_lines] == ["round1", "answer1", None]
-    assert fork_lines[-1]["event"] == "fork_marker"
-    bus.publish_inbound.assert_not_awaited()
-
-
-@pytest.mark.asyncio
-async def test_fork_chat_rejects_invalid_source_and_index(bus: MagicMock, tmp_path) -> None:
-    sessions = SessionManager(tmp_path / "sessions")
-    channel = WebSocketChannel(
-        {"enabled": True, "allowFrom": ["*"], "host": "127.0.0.1"},
-        bus,
-        gateway=_basic_handler(bus, session_manager=sessions, workspace_path=tmp_path),
-    )
-    conn = AsyncMock()
-
-    await channel._dispatch_envelope(
-        conn,
-        "webui-client",
-        {"type": "fork_chat", "source_chat_id": "bad/source", "before_user_index": 0},
-    )
-    payload = json.loads(conn.send.await_args.args[0])
-    assert payload["event"] == "error"
-    assert payload["detail"] == "invalid source_chat_id"
-
-    conn.reset_mock()
-    await channel._dispatch_envelope(
-        conn,
-        "webui-client",
-        {"type": "fork_chat", "source_chat_id": "missing", "before_user_index": -1},
-    )
-    payload = json.loads(conn.send.await_args.args[0])
-    assert payload["event"] == "error"
-    assert payload["detail"] == "invalid before_user_index"
-    bus.publish_inbound.assert_not_awaited()
-
-
 @pytest.mark.asyncio
 async def test_webui_message_envelope_appends_user_transcript(
     bus: MagicMock,

tests/utils/test_webui_transcript.py

@@ -46,33 +46,6 @@ def test_fork_transcript_before_user_index_copies_only_prefix(tmp_path, monkeypa
     assert "round3 must not appear" not in "\n".join(str(line.get("text")) for line in lines)
 
 
-def test_fork_transcript_from_middle_assistant_reply_keeps_selected_turn(
-    tmp_path,
-    monkeypatch,
-) -> None:
-    monkeypatch.setattr("nanobot.config.paths.get_data_dir", lambda: tmp_path)
-    source = "websocket:source"
-    for ev in (
-        {"event": "user", "chat_id": "source", "text": "round1"},
-        {"event": "message", "chat_id": "source", "text": "answer1"},
-        {"event": "user", "chat_id": "source", "text": "round2"},
-        {"event": "message", "chat_id": "source", "text": "answer2"},
-        {"event": "user", "chat_id": "source", "text": "round3 must not appear"},
-        {"event": "message", "chat_id": "source", "text": "answer3 must not appear"},
-    ):
-        append_transcript_object(source, ev)
-
-    ok = fork_transcript_before_user_index(source, "websocket:fork", 2)
-
-    assert ok is True
-    assert [line.get("text") for line in read_transcript_lines("websocket:fork")] == [
-        "round1",
-        "answer1",
-        "round2",
-        "answer2",
-    ]
-
-
 def test_fork_transcript_rejects_out_of_range_user_index(tmp_path, monkeypatch) -> None:
     monkeypatch.setattr("nanobot.config.paths.get_data_dir", lambda: tmp_path)
     source = "websocket:source"
@@ -82,24 +55,6 @@ def test_fork_transcript_rejects_out_of_range_user_index(tmp_path, monkeypatch)
     assert read_transcript_lines("websocket:fork") == []
 
 
-def test_fork_transcript_allows_index_equal_to_user_count(tmp_path, monkeypatch) -> None:
-    monkeypatch.setattr("nanobot.config.paths.get_data_dir", lambda: tmp_path)
-    source = "websocket:source"
-    for ev in (
-        {"event": "user", "chat_id": "source", "text": "round1"},
-        {"event": "message", "chat_id": "source", "text": "answer1"},
-    ):
-        append_transcript_object(source, ev)
-
-    ok = fork_transcript_before_user_index(source, "websocket:fork", 1)
-
-    assert ok is True
-    assert [line.get("text") for line in read_transcript_lines("websocket:fork")] == [
-        "round1",
-        "answer1",
-    ]
-
-
 def test_build_response_reports_fork_boundary_from_marker(tmp_path, monkeypatch) -> None:
     monkeypatch.setattr("nanobot.config.paths.get_data_dir", lambda: tmp_path)
     key = "websocket:fork"

webui/src/components/MessageBubble.tsx

@@ -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">
-              <div className="mt-2 flex min-h-8 flex-wrap items-center gap-x-2 gap-y-1 text-muted-foreground">
+              {showCopyButton ? (
-                {showCopyButton ? (
+                <button
-                  <MessageActionTooltip label={copyReplyLabel}>
+                  type="button"
-                    <button
+                  onClick={onCopyAssistantReply}
-                      type="button"
+                  aria-label={copyReplyLabel}
-                      onClick={onCopyMessage}
+                  title={copyReplyLabel}
-                      aria-label={copyReplyLabel}
+                  className={cn(
-                      className={cn(
+                    "inline-flex h-8 w-8 shrink-0 items-center justify-center rounded-full",
-                        "inline-flex h-8 w-8 shrink-0 items-center justify-center rounded-full",
+                    "transition-colors hover:bg-muted/55 hover:text-foreground",
-                        "transition-colors hover:bg-muted/55 hover:text-foreground",
+                    "focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring",
-                        "focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring",
+                  )}
-                      )}
+                >
-                    >
+                  {copied ? (
-                      {copied ? (
+                    <Check className="h-4 w-4" aria-hidden />
-                        <Check className="h-4 w-4" aria-hidden />
+                  ) : (
-                      ) : (
+                    <Copy className="h-4 w-4" aria-hidden />
-                        <Copy className="h-4 w-4" aria-hidden />
+                  )}
-                      )}
+                </button>
-                    </button>
+              ) : null}
-                  </MessageActionTooltip>
+              {showForkButton ? (
-                ) : null}
+                <button
-                {showForkButton ? (
+                  type="button"
-                  <MessageActionTooltip label={forkLabel}>
+                  onClick={onForkFromHere}
-                    <button
+                  aria-label={forkLabel}
-                      type="button"
+                  title={forkLabel}
-                      onClick={onForkFromHere}
+                  className={cn(
-                      aria-label={forkLabel}
+                    "inline-flex h-8 w-8 shrink-0 items-center justify-center rounded-full",
-                      className={cn(
+                    "transition-colors hover:bg-muted/55 hover:text-foreground",
-                        "inline-flex h-8 w-8 shrink-0 items-center justify-center rounded-full",
+                    "focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring",
-                        "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>
-                      <ForkFromHereIcon className="h-4 w-4" aria-hidden />
+              ) : null}
-                    </button>
+              {showLatencyFooter ? (
-                  </MessageActionTooltip>
+                <span
-                ) : null}
+                  className="text-[11px] leading-none text-muted-foreground/70 tabular-nums"
-                {showLatencyFooter ? (
+                  title={t("message.turnLatencyTitle")}
-                  <span
+                >
-                    className="text-[11px] leading-none text-muted-foreground/70 tabular-nums"
+                  {formatTurnLatency(latencyMs)}
-                    title={t("message.turnLatencyTitle")}
+                </span>
-                  >
+              ) : null}
-                    {formatTurnLatency(latencyMs)}
+            </div>
-                  </span>
-                ) : null}
-              </div>
-            </TooltipProvider>
           ) : 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,

webui/src/components/thread/ThreadComposer.tsx

@@ -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;

webui/src/components/thread/ThreadMessages.tsx

@@ -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
+                    onForkFromMessage && forkIndex !== undefined
-                      ? forkHandlerForAssistantMessage(
+                      ? () => onForkFromMessage(forkIndex)
-                          unit.message,
-                          copyFlags[index],
-                          assistantForkIndexById,
-                          onForkFromMessage,
-                        )
                       : 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;

webui/src/components/thread/ThreadShell.tsx

@@ -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) {
+      if (!forkedChatId) return;
-        setForkError(t("thread.fork.failed", {
-          defaultValue: "Could not fork this chat. Try again.",
-        }));
-        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}

webui/src/components/thread/ThreadViewport.tsx

@@ -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}

webui/src/i18n/locales/en/common.json

@@ -811,10 +811,7 @@
     },
     "scrollToBottom": "Scroll to bottom",
     "loadEarlier": "Load earlier messages",
-    "fork": {
+    "forkedFromHistory": "Forked from history",
-      "failed": "Could not fork this chat. Try again.",
-      "fromHistory": "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",

webui/src/i18n/locales/es/common.json

@@ -811,10 +811,7 @@
     },
     "scrollToBottom": "Desplazarse al final",
     "loadEarlier": "Cargar mensajes anteriores",
-    "fork": {
+    "forkedFromHistory": "Bifurcado desde el historial",
-      "failed": "No se pudo bifurcar este chat. Inténtalo de nuevo.",
-      "fromHistory": "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",

webui/src/i18n/locales/fr/common.json

@@ -811,10 +811,7 @@
     },
     "scrollToBottom": "Faire défiler vers le bas",
     "loadEarlier": "Charger les messages précédents",
-    "fork": {
+    "forkedFromHistory": "Bifurqué depuis l'historique",
-      "failed": "Impossible de bifurquer cette conversation. Réessayez.",
-      "fromHistory": "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",

webui/src/i18n/locales/id/common.json

@@ -811,10 +811,7 @@
     },
     "scrollToBottom": "Gulir ke bawah",
     "loadEarlier": "Muat pesan sebelumnya",
-    "fork": {
+    "forkedFromHistory": "Fork dari riwayat",
-      "failed": "Tidak dapat mem-fork chat ini. Coba lagi.",
-      "fromHistory": "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",

webui/src/i18n/locales/ja/common.json

@@ -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": {
+    "forkedFromHistory": "履歴から分岐",
-      "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"
-    },
     "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",

webui/src/i18n/locales/ko/common.json

@@ -811,10 +811,7 @@
     },
     "scrollToBottom": "맨 아래로 스크롤",
     "loadEarlier": "이전 메시지 불러오기",
-    "fork": {
+    "forkedFromHistory": "기록에서 분기됨",
-      "failed": "이 채팅을 분기할 수 없습니다. 다시 시도해 주세요.",
-      "fromHistory": "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",

webui/src/i18n/locales/vi/common.json

@@ -811,10 +811,7 @@
     },
     "scrollToBottom": "Cuộn xuống cuối",
     "loadEarlier": "Tải tin nhắn trước đó",
-    "fork": {
+    "forkedFromHistory": "Tách nhánh từ lịch sử",
-      "failed": "Không thể rẽ nhánh cuộc trò chuyện này. Hãy thử lại.",
-      "fromHistory": "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",

webui/src/i18n/locales/zh-CN/common.json

@@ -811,10 +811,7 @@
     },
     "scrollToBottom": "滚动到底部",
     "loadEarlier": "加载更早消息",
-    "fork": {
+    "forkedFromHistory": "从历史消息分叉",
-      "failed": "无法分叉这个对话，请重试。",
-      "fromHistory": "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",

webui/src/i18n/locales/zh-TW/common.json

@@ -811,10 +811,7 @@
     },
     "scrollToBottom": "捲動到底部",
     "loadEarlier": "載入更早訊息",
-    "fork": {
+    "forkedFromHistory": "從歷史訊息分叉",
-      "failed": "無法分叉這個對話，請重試。",
-      "fromHistory": "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",

webui/src/tests/message-bubble.test.tsx

@@ -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();
   });
 

webui/src/tests/thread-shell.test.tsx

@@ -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");

webui/src/tests/useSessions.test.tsx

@@ -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,