fix(webui): stabilize live thread rendering and navigation

nanobot/channels/websocket.py

@@ -1476,6 +1476,8 @@ class WebSocketChannel(BaseChannel):
                 payload["media_urls"] = urls
         if msg.reply_to:
             payload["reply_to"] = msg.reply_to
+        if msg.metadata.get("_tool_events"):
+            payload["tool_events"] = msg.metadata["_tool_events"]
         # Mark intermediate agent breadcrumbs (tool-call hints, generic
         # progress strings) so WS clients can render them as subordinate
         # trace rows rather than conversational replies.

tests/channels/test_websocket_channel.py

@@ -322,6 +322,54 @@ async def test_send_removes_connection_on_connection_closed() -> None:
     assert mock_ws not in channel._conn_chats
 
 
+@pytest.mark.asyncio
+async def test_send_progress_includes_structured_tool_events() -> None:
+    bus = MagicMock()
+    channel = WebSocketChannel({"enabled": True, "allowFrom": ["*"]}, bus)
+    mock_ws = AsyncMock()
+    channel._attach(mock_ws, "chat-1")
+
+    await channel.send(OutboundMessage(
+        channel="websocket",
+        chat_id="chat-1",
+        content='search "hermes"',
+        metadata={
+            "_progress": True,
+            "_tool_hint": True,
+            "_tool_events": [
+                {
+                    "version": 1,
+                    "phase": "start",
+                    "call_id": "call-1",
+                    "name": "web_search",
+                    "arguments": {"query": "hermes", "count": 8},
+                    "result": None,
+                    "error": None,
+                    "files": [],
+                    "embeds": [],
+                }
+            ],
+        },
+    ))
+
+    payload = json.loads(mock_ws.send.await_args.args[0])
+    assert payload["event"] == "message"
+    assert payload["kind"] == "tool_hint"
+    assert payload["tool_events"] == [
+        {
+            "version": 1,
+            "phase": "start",
+            "call_id": "call-1",
+            "name": "web_search",
+            "arguments": {"query": "hermes", "count": 8},
+            "result": None,
+            "error": None,
+            "files": [],
+            "embeds": [],
+        }
+    ]
+
+
 @pytest.mark.asyncio
 async def test_send_delta_removes_connection_on_connection_closed() -> None:
     bus = MagicMock()

webui/src/components/Sidebar.tsx

@@ -31,8 +31,10 @@ export function Sidebar(props: SidebarProps) {
   const normalizedQuery = query.trim().toLowerCase();
   const filteredSessions = useMemo(() => {
     if (!normalizedQuery) return props.sessions;
+    const terms = normalizedQuery.split(/\s+/).filter(Boolean);
     return props.sessions.filter((session) => {
       const haystack = [
+        session.title,
         session.preview,
         session.chatId,
         session.channel,
@@ -41,7 +43,7 @@ export function Sidebar(props: SidebarProps) {
         .filter(Boolean)
         .join(" ")
         .toLowerCase();
-      return haystack.includes(normalizedQuery);
+      return terms.every((term) => haystack.includes(term));
     });
   }, [normalizedQuery, props.sessions]);
 

webui/src/components/thread/ThreadShell.tsx

@@ -81,19 +81,33 @@ export function ThreadShell({
   const { t } = useTranslation();
   const chatId = session?.chatId ?? null;
   const historyKey = session?.key ?? null;
-  const { messages: historical, loading, hasPendingToolCalls } = useSessionHistory(historyKey);
-  const { modelName, token } = useClient();
+  const {
+    messages: historical,
+    loading,
+    hasPendingToolCalls,
+    refresh: refreshHistory,
+    version: historyVersion,
+  } = useSessionHistory(historyKey);
+  const { client, modelName, token } = useClient();
   const [booting, setBooting] = useState(false);
   const [slashCommands, setSlashCommands] = useState<SlashCommand[]>([]);
   const [heroImageMode, setHeroImageMode] = useState(false);
+  const [scrollToBottomSignal, setScrollToBottomSignal] = useState(0);
   const pendingFirstRef = useRef<PendingFirstMessage | null>(null);
   const messageCacheRef = useRef<Map<string, UIMessage[]>>(new Map());
   const lastCachedChatIdRef = useRef<string | null>(null);
+  const appliedHistoryVersionRef = useRef<Map<string, number>>(new Map());
+  const pendingCanonicalHydrateRef = useRef<Set<string>>(new Set());
 
   const initial = useMemo(() => {
     if (!chatId) return historical;
     return messageCacheRef.current.get(chatId) ?? historical;
   }, [chatId, historical]);
+  const handleTurnEnd = useCallback(() => {
+    if (chatId) pendingCanonicalHydrateRef.current.add(chatId);
+    refreshHistory();
+    onTurnEnd?.();
+  }, [chatId, onTurnEnd, refreshHistory]);
   const {
     messages,
     isStreaming,
@@ -102,22 +116,48 @@ export function ThreadShell({
     setMessages,
     streamError,
     dismissStreamError,
-  } = useNanobotStream(chatId, initial, hasPendingToolCalls, onTurnEnd);
+  } = useNanobotStream(chatId, initial, hasPendingToolCalls, handleTurnEnd);
   const showHeroComposer = messages.length === 0 && !loading;
 
   useEffect(() => {
     if (!chatId || loading) return;
     const cached = messageCacheRef.current.get(chatId);
+    const appliedVersion = appliedHistoryVersionRef.current.get(chatId) ?? 0;
+    const hasPendingCanonicalHydrate = pendingCanonicalHydrateRef.current.has(chatId);
+    const hasNewCanonicalHistory = hasPendingCanonicalHydrate && historyVersion > appliedVersion;
     // When the user switches away and back, keep the local in-memory thread
     // state (including not-yet-persisted messages) instead of replacing it with
-    // whatever the history endpoint currently knows about.
+    // whatever the history endpoint currently knows about. Once a fresh
+    // canonical replay arrives after turn_end, prefer it so live Markdown/tool
+    // rendering converges to the same shape as a manual refresh.
     setMessages((prev) => {
+      if (hasNewCanonicalHistory && historical.length > 0) {
+        pendingCanonicalHydrateRef.current.delete(chatId);
+        appliedHistoryVersionRef.current.set(chatId, historyVersion);
+        messageCacheRef.current.set(chatId, historical);
+        return historical;
+      }
       if (cached && cached.length > 0) return cached;
       if (historical.length === 0 && prev.length > 0) return prev;
+      appliedHistoryVersionRef.current.set(chatId, historyVersion);
       return historical;
     });
     // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [loading, chatId, historical]);
+  }, [loading, chatId, historical, historyVersion]);
+
+  useEffect(() => {
+    if (!chatId) return;
+    return client.onSessionUpdate((updatedChatId) => {
+      if (updatedChatId !== chatId) return;
+      pendingCanonicalHydrateRef.current.add(chatId);
+      refreshHistory();
+    });
+  }, [chatId, client, refreshHistory]);
+
+  useEffect(() => {
+    if (!chatId || loading) return;
+    setScrollToBottomSignal((value) => value + 1);
+  }, [chatId, loading, historical]);
 
   useEffect(() => {
     if (chatId) return;
@@ -148,6 +188,7 @@ export function ThreadShell({
     const pending = pendingFirstRef.current;
     if (!pending) return;
     pendingFirstRef.current = null;
+    setScrollToBottomSignal((value) => value + 1);
     send(pending.content, pending.images, pending.options);
     setBooting(false);
   }, [chatId, send]);
@@ -181,18 +222,26 @@ export function ThreadShell({
     [booting, onCreateChat],
   );
 
+  const handleThreadSend = useCallback(
+    (content: string, images?: SendImage[], options?: SendOptions) => {
+      setScrollToBottomSignal((value) => value + 1);
+      send(content, images, options);
+    },
+    [send],
+  );
+
   const handleQuickAction = useCallback(
     (prompt: string) => {
       const options: SendOptions | undefined = heroImageMode
         ? { imageGeneration: { enabled: true, aspect_ratio: null } }
         : undefined;
       if (session) {
-        send(prompt, undefined, options);
+        handleThreadSend(prompt, undefined, options);
         return;
       }
       void handleWelcomeSend(prompt, undefined, options);
     },
-    [handleWelcomeSend, heroImageMode, send, session],
+    [handleThreadSend, handleWelcomeSend, heroImageMode, session],
   );
 
   const quickActionItems = heroImageMode ? IMAGE_QUICK_ACTION_KEYS : QUICK_ACTION_KEYS;
@@ -233,7 +282,7 @@ export function ThreadShell({
       ) : null}
       {session ? (
         <ThreadComposer
-          onSend={send}
+          onSend={handleThreadSend}
           disabled={!chatId}
           isStreaming={isStreaming}
           placeholder={
@@ -296,6 +345,8 @@ export function ThreadShell({
         isStreaming={isStreaming}
         emptyState={emptyState}
         composer={composer}
+        scrollToBottomSignal={scrollToBottomSignal}
+        conversationKey={historyKey}
       />
     </section>
   );

webui/src/components/thread/ThreadViewport.tsx

@@ -1,4 +1,4 @@
-import { type ReactNode, useCallback, useEffect, useRef, useState } from "react";
+import { type ReactNode, useCallback, useEffect, useLayoutEffect, useRef, useState } from "react";
 import { ArrowDown } from "lucide-react";
 import { useTranslation } from "react-i18next";
 
@@ -12,6 +12,8 @@ interface ThreadViewportProps {
   isStreaming: boolean;
   composer: ReactNode;
   emptyState?: ReactNode;
+  scrollToBottomSignal?: number;
+  conversationKey?: string | null;
 }
 
 const NEAR_BOTTOM_PX = 48;
@@ -21,26 +23,92 @@ export function ThreadViewport({
   isStreaming,
   composer,
   emptyState,
+  scrollToBottomSignal = 0,
+  conversationKey = null,
 }: ThreadViewportProps) {
   const { t } = useTranslation();
   const scrollRef = useRef<HTMLDivElement>(null);
+  const contentRef = useRef<HTMLDivElement>(null);
+  const bottomRef = useRef<HTMLDivElement>(null);
+  const lastConversationKeyRef = useRef<string | null>(conversationKey);
+  const pendingConversationScrollRef = useRef(true);
+  const scrollFrameIdsRef = useRef<number[]>([]);
+  const forceBottomUntilRef = useRef(0);
   const [atBottom, setAtBottom] = useState(true);
   const hasMessages = messages.length > 0;
 
-  const scrollToBottom = useCallback((smooth = false) => {
-    const el = scrollRef.current;
-    if (!el) return;
-    el.scrollTo({
-      top: el.scrollHeight,
-      behavior: smooth ? "smooth" : "auto",
-    });
+  const cancelScheduledBottomScroll = useCallback(() => {
+    for (const id of scrollFrameIdsRef.current) {
+      window.cancelAnimationFrame(id);
+    }
+    scrollFrameIdsRef.current = [];
   }, []);
 
+  const scrollToBottomNow = useCallback((smooth = false) => {
+    const el = scrollRef.current;
+    const marker = bottomRef.current;
+    const behavior: ScrollBehavior = smooth ? "smooth" : "auto";
+    if (marker) {
+      marker.scrollIntoView({ block: "end", behavior });
+    } else if (el) {
+      el.scrollTo({ top: el.scrollHeight, behavior });
+    }
+    setAtBottom(true);
+  }, []);
+
+  const scrollToBottom = useCallback((smooth = false, frames = 1) => {
+    cancelScheduledBottomScroll();
+    scrollToBottomNow(smooth);
+    for (let i = 1; i < frames; i += 1) {
+      const id = window.requestAnimationFrame(() => scrollToBottomNow(smooth));
+      scrollFrameIdsRef.current.push(id);
+    }
+  }, [cancelScheduledBottomScroll, scrollToBottomNow]);
+
   useEffect(() => {
     if (!atBottom) return;
     scrollToBottom(!isStreaming);
   }, [messages, isStreaming, atBottom, scrollToBottom]);
 
+  useEffect(() => {
+    if (scrollToBottomSignal <= 0) return;
+    forceBottomUntilRef.current = Date.now() + 2_000;
+    scrollToBottom(true, 8);
+  }, [scrollToBottomSignal, scrollToBottom]);
+
+  useLayoutEffect(() => {
+    if (lastConversationKeyRef.current === conversationKey) return;
+    lastConversationKeyRef.current = conversationKey;
+    pendingConversationScrollRef.current = true;
+    forceBottomUntilRef.current = Date.now() + 2_000;
+    setAtBottom(true);
+  }, [conversationKey]);
+
+  useLayoutEffect(() => {
+    if (!pendingConversationScrollRef.current) return;
+    if (!conversationKey) {
+      pendingConversationScrollRef.current = false;
+      scrollToBottom(false, 4);
+      return;
+    }
+    scrollToBottom(false, 8);
+    if (!hasMessages) return;
+    pendingConversationScrollRef.current = false;
+  }, [conversationKey, hasMessages, messages, scrollToBottom]);
+
+  useEffect(() => cancelScheduledBottomScroll, [cancelScheduledBottomScroll]);
+
+  useEffect(() => {
+    const target = contentRef.current;
+    if (!target || typeof ResizeObserver === "undefined") return;
+    const observer = new ResizeObserver(() => {
+      if (!atBottom && Date.now() > forceBottomUntilRef.current) return;
+      scrollToBottom(false, 4);
+    });
+    observer.observe(target);
+    return () => observer.disconnect();
+  }, [atBottom, hasMessages, scrollToBottom]);
+
   useEffect(() => {
     const el = scrollRef.current;
     if (!el) return;
@@ -68,7 +136,7 @@ export function ThreadViewport({
         )}
       >
         {hasMessages ? (
-          <div className="mx-auto flex min-h-full w-full max-w-[64rem] flex-col">
+          <div ref={contentRef} className="mx-auto flex min-h-full w-full max-w-[64rem] flex-col">
             <div className="flex-1 px-4 pb-20 pt-4">
               <div className="mx-auto w-full max-w-[49.5rem]">
                 <ThreadMessages messages={messages} />
@@ -82,7 +150,7 @@ export function ThreadViewport({
             </div>
           </div>
         ) : (
-          <div className="mx-auto flex min-h-full w-full max-w-[72rem] flex-col px-4">
+          <div ref={contentRef} className="mx-auto flex min-h-full w-full max-w-[72rem] flex-col px-4">
             <div className="flex w-full flex-1 items-center justify-center pb-[7vh] pt-8">
               <div className="flex w-full max-w-[58rem] flex-col gap-6">
                 {emptyState}
@@ -91,6 +159,7 @@ export function ThreadViewport({
             </div>
           </div>
         )}
+        <div ref={bottomRef} aria-hidden className="h-px" />
       </div>
 
       <div

webui/src/hooks/useNanobotStream.ts

@@ -2,6 +2,7 @@ import { useCallback, useEffect, useRef, useState } from "react";
 
 import { useClient } from "@/providers/ClientProvider";
 import { toMediaAttachment } from "@/lib/media";
+import { toolTraceLinesFromEvents } from "@/lib/tool-traces";
 import type { StreamError } from "@/lib/nanobot-client";
 import type {
   InboundEvent,
@@ -107,6 +108,59 @@ function closeReasoningStream(prev: UIMessage[]): UIMessage[] {
   return prev;
 }
 
+function isReasoningOnlyPlaceholder(message: UIMessage): boolean {
+  return (
+    message.role === "assistant"
+    && message.kind !== "trace"
+    && message.content.trim().length === 0
+    && !!message.reasoning
+    && !message.reasoningStreaming
+    && !message.media?.length
+  );
+}
+
+function isToolTrace(message: UIMessage | undefined): boolean {
+  return message?.kind === "trace";
+}
+
+function pruneReasoningOnlyPlaceholders(prev: UIMessage[]): UIMessage[] {
+  return prev.filter((message, index) => {
+    if (!isReasoningOnlyPlaceholder(message)) return true;
+    // A reasoning-only assistant row immediately followed by tool traces is
+    // the live equivalent of a persisted assistant tool-call message with
+    // empty content, reasoning_content, and tool_calls. Keep it so live render
+    // and history replay stay isomorphic.
+    return isToolTrace(prev[index + 1]);
+  });
+}
+
+function absorbCompleteAssistantMessage(
+  prev: UIMessage[],
+  message: Omit<UIMessage, "id" | "role" | "createdAt">,
+): UIMessage[] {
+  const last = prev[prev.length - 1];
+  if (!last || !isReasoningOnlyPlaceholder(last)) {
+    return [
+      ...prev,
+      {
+        id: crypto.randomUUID(),
+        role: "assistant",
+        createdAt: Date.now(),
+        ...message,
+      },
+    ];
+  }
+  return [
+    ...prev.slice(0, -1),
+    {
+      ...last,
+      ...message,
+      isStreaming: false,
+      reasoningStreaming: false,
+    },
+  ];
+}
+
 /**
  * Subscribe to a chat by ID. Returns the in-memory message list for the chat,
  * a streaming flag, and a ``send`` function. Initial history must be seeded
@@ -286,9 +340,10 @@ export function useNanobotStream(
           streamEndTimerRef.current = null;
         }
         setIsStreaming(false);
-        setMessages((prev) =>
-          prev.map((m) => (m.isStreaming ? { ...m, isStreaming: false } : m)),
-        );
+        setMessages((prev) => {
+          const finalized = prev.map((m) => (m.isStreaming ? { ...m, isStreaming: false } : m));
+          return pruneReasoningOnlyPlaceholders(finalized);
+        });
         suppressStreamUntilTurnEndRef.current = false;
         onTurnEnd?.();
         return;
@@ -314,14 +369,20 @@ export function useNanobotStream(
         // Attach them to the last trace row if it was the last emitted item
         // so a sequence of calls collapses into one compact trace group.
         if (ev.kind === "tool_hint" || ev.kind === "progress") {
-          const line = ev.text;
+          const structuredLines = toolTraceLinesFromEvents(ev.tool_events);
+          const lines = structuredLines.length > 0
+            ? structuredLines
+            : ev.text
+              ? [ev.text]
+              : [];
+          if (lines.length === 0) return;
           setMessages((prev) => {
             const last = prev[prev.length - 1];
             if (last && last.kind === "trace" && !last.isStreaming) {
               const merged: UIMessage = {
                 ...last,
-                traces: [...(last.traces ?? [last.content]), line],
-                content: line,
+                traces: [...(last.traces ?? [last.content]), ...lines],
+                content: lines[lines.length - 1],
               };
               return [...prev.slice(0, -1), merged];
             }
@@ -331,8 +392,8 @@ export function useNanobotStream(
                 id: crypto.randomUUID(),
                 role: "tool",
                 kind: "trace",
-                content: line,
-                traces: [line],
+                content: lines[lines.length - 1],
+                traces: lines,
                 createdAt: Date.now(),
               },
             ];
@@ -354,16 +415,10 @@ export function useNanobotStream(
         setMessages((prev) => {
           const filtered = activeId ? prev.filter((m) => m.id !== activeId) : prev;
           const content = ev.text;
-          return [
-            ...filtered,
-            {
-              id: crypto.randomUUID(),
-              role: "assistant",
-              content,
-              createdAt: Date.now(),
-              ...(hasMedia ? { media } : {}),
-            },
-          ];
+          return absorbCompleteAssistantMessage(filtered, {
+            content,
+            ...(hasMedia ? { media } : {}),
+          });
         });
         if (hasMedia) {
           suppressStreamUntilTurnEndRef.current = true;
@@ -395,7 +450,7 @@ export function useNanobotStream(
 
       const previews = hasImages ? images!.map((i) => i.preview) : undefined;
       setMessages((prev) => [
-        ...prev,
+        ...pruneReasoningOnlyPlaceholders(prev),
         {
           id: crypto.randomUUID(),
           role: "user",

webui/src/hooks/useSessions.ts

@@ -10,6 +10,7 @@ import {
 } from "@/lib/api";
 import { deriveTitle } from "@/lib/format";
 import { toMediaAttachment } from "@/lib/media";
+import { formatToolCallTrace } from "@/lib/tool-traces";
 import type { ChatSummary, UIMessage } from "@/lib/types";
 
 const EMPTY_MESSAGES: UIMessage[] = [];
@@ -31,24 +32,6 @@ function reasoningFromHistory(message: HistoryMessage): string | undefined {
   return parts.length > 0 ? parts.join("\n\n") : undefined;
 }
 
-function formatToolCallTrace(call: unknown): string | null {
-  if (!call || typeof call !== "object") return null;
-  const item = call as {
-    name?: unknown;
-    function?: { name?: unknown; arguments?: unknown };
-  };
-  const name =
-    typeof item.function?.name === "string"
-      ? item.function.name
-      : typeof item.name === "string"
-        ? item.name
-        : "";
-  if (!name) return null;
-  const args = item.function?.arguments;
-  if (typeof args === "string" && args.trim()) return `${name}(${args})`;
-  return `${name}()`;
-}
-
 function toolTracesFromHistory(message: HistoryMessage): string[] {
   if (!Array.isArray(message.tool_calls)) return [];
   return message.tool_calls
@@ -133,23 +116,31 @@ export function useSessionHistory(key: string | null): {
   messages: UIMessage[];
   loading: boolean;
   error: string | null;
+  refresh: () => void;
+  version: number;
   /** ``true`` when the last persisted assistant turn has ``tool_calls`` but no
    *  final text yet — the model was still processing when the page loaded. */
   hasPendingToolCalls: boolean;
 } {
   const { token } = useClient();
+  const [refreshSeq, setRefreshSeq] = useState(0);
+  const refresh = useCallback(() => {
+    setRefreshSeq((value) => value + 1);
+  }, []);
   const [state, setState] = useState<{
     key: string | null;
     messages: UIMessage[];
     loading: boolean;
     error: string | null;
     hasPendingToolCalls: boolean;
+    version: number;
   }>({
     key: null,
     messages: [],
     loading: false,
     error: null,
     hasPendingToolCalls: false,
+    version: 0,
   });
 
   useEffect(() => {
@@ -160,19 +151,23 @@ export function useSessionHistory(key: string | null): {
         loading: false,
         error: null,
         hasPendingToolCalls: false,
+        version: 0,
       });
       return;
     }
     let cancelled = false;
     // Mark the new key as loading immediately so callers never see stale
     // messages from the previous session during the render right after a switch.
-    setState({
-      key,
-      messages: [],
-      loading: true,
-      error: null,
-      hasPendingToolCalls: false,
-    });
+    setState((prev) => prev.key === key
+      ? { ...prev, loading: true, error: null }
+      : {
+          key,
+          messages: [],
+          loading: true,
+          error: null,
+          hasPendingToolCalls: false,
+          version: 0,
+        });
     (async () => {
       try {
         const body = await fetchSessionMessages(token, key);
@@ -203,7 +198,9 @@ export function useSessionHistory(key: string | null): {
               : {}),
           };
           const traces = m.role === "assistant" ? toolTracesFromHistory(m) : [];
-          if (traces.length === 0) return [row];
+          if (traces.length === 0) {
+            return row.content.trim() || row.media?.length ? [row] : [];
+          }
           return [
             ...(row.content.trim() || row.reasoning || row.media?.length ? [row] : []),
             {
@@ -225,55 +222,74 @@ export function useSessionHistory(key: string | null): {
           lastRaw?.role === "assistant" &&
           Array.isArray(lastRaw.tool_calls) &&
           lastRaw.tool_calls.length > 0;
-        setState({
+        setState((prev) => ({
           key,
           messages: ui,
           loading: false,
           error: null,
           hasPendingToolCalls: hasPending,
-        });
+          version: prev.key === key ? prev.version + 1 : 1,
+        }));
       } catch (e) {
         if (cancelled) return;
         // A 404 just means the session hasn't been persisted yet (brand-new
         // chat, first message not sent). That's a normal state, not an error.
         if (e instanceof ApiError && e.status === 404) {
-          setState({
+          setState((prev) => ({
             key,
             messages: [],
             loading: false,
             error: null,
             hasPendingToolCalls: false,
-          });
+            version: prev.key === key ? prev.version + 1 : 1,
+          }));
         } else {
-          setState({
+          setState((prev) => ({
             key,
             messages: [],
             loading: false,
             error: (e as Error).message,
             hasPendingToolCalls: false,
-          });
+            version: prev.key === key ? prev.version : 0,
+          }));
         }
       }
     })();
     return () => {
       cancelled = true;
     };
-  }, [key, token]);
+  }, [key, token, refreshSeq]);
 
   if (!key) {
-    return { messages: EMPTY_MESSAGES, loading: false, error: null, hasPendingToolCalls: false };
+    return {
+      messages: EMPTY_MESSAGES,
+      loading: false,
+      error: null,
+      refresh,
+      version: 0,
+      hasPendingToolCalls: false,
+    };
   }
 
   // Even before the effect above commits its loading state, never surface the
   // previous session's payload for a brand-new key.
   if (state.key !== key) {
-    return { messages: EMPTY_MESSAGES, loading: true, error: null, hasPendingToolCalls: false };
+    return {
+      messages: EMPTY_MESSAGES,
+      loading: true,
+      error: null,
+      refresh,
+      version: 0,
+      hasPendingToolCalls: false,
+    };
   }
 
   return {
     messages: state.messages,
     loading: state.loading,
     error: state.error,
+    refresh,
+    version: state.version,
     hasPendingToolCalls: state.hasPendingToolCalls,
   };
 }

webui/src/lib/tool-traces.ts

@@ -0,0 +1,30 @@
+export function formatToolCallTrace(call: unknown): string | null {
+  if (!call || typeof call !== "object") return null;
+  const item = call as {
+    name?: unknown;
+    arguments?: unknown;
+    function?: { name?: unknown; arguments?: unknown };
+  };
+  const name =
+    typeof item.function?.name === "string"
+      ? item.function.name
+      : typeof item.name === "string"
+        ? item.name
+        : "";
+  if (!name) return null;
+  const args = item.function?.arguments ?? item.arguments;
+  if (typeof args === "string" && args.trim()) return `${name}(${args})`;
+  if (args && typeof args === "object") return `${name}(${JSON.stringify(args)})`;
+  return `${name}()`;
+}
+
+export function toolTraceLinesFromEvents(events: unknown): string[] {
+  if (!Array.isArray(events)) return [];
+  return events
+    .filter((event) => {
+      if (!event || typeof event !== "object") return false;
+      return (event as { phase?: unknown }).phase === "start";
+    })
+    .map(formatToolCallTrace)
+    .filter((trace): trace is string => !!trace);
+}

webui/src/lib/types.ts

@@ -53,6 +53,18 @@ export interface UIMessage {
   reasoningStreaming?: boolean;
 }
 
+export interface ToolProgressEvent {
+  version?: number;
+  phase?: "start" | "end" | "error" | string;
+  call_id?: string;
+  name?: string;
+  arguments?: unknown;
+  result?: unknown;
+  error?: unknown;
+  files?: unknown[];
+  embeds?: unknown[];
+}
+
 export interface ChatSummary {
   /** Server-side session key, e.g. ``websocket:abcd-...``. */
   key: string;
@@ -146,6 +158,7 @@ export type InboundEvent =
       reply_to?: string;
       media?: string[];
       media_urls?: Array<{ url: string; name?: string }>;
+      tool_events?: ToolProgressEvent[];
       /** Present when the frame is an agent breadcrumb (e.g. tool hint,
        * generic progress line) rather than a conversational reply. */
       kind?: "tool_hint" | "progress" | "reasoning";

webui/src/tests/app-layout.test.tsx

@@ -342,6 +342,7 @@ describe("App layout", () => {
         chatId: "chat-alpha",
         createdAt: new Date().toISOString(),
         updatedAt: new Date().toISOString(),
+        title: "Q2 roadmap",
         preview: "Project planning notes",
       },
       {
@@ -358,15 +359,22 @@ describe("App layout", () => {
 
     await waitFor(() => expect(connectSpy).toHaveBeenCalled());
     const sidebar = screen.getByRole("navigation", { name: "Sidebar navigation" });
-    expect(within(sidebar).getByText("Project planning notes")).toBeInTheDocument();
+    expect(within(sidebar).getByText("Q2 roadmap")).toBeInTheDocument();
     expect(within(sidebar).getByText("Travel ideas")).toBeInTheDocument();
 
     fireEvent.change(screen.getByRole("textbox", { name: "Search chats" }), {
-      target: { value: "travel" },
+      target: { value: "planning" },
     });
 
-    expect(within(sidebar).queryByText("Project planning notes")).not.toBeInTheDocument();
-    expect(within(sidebar).getByText("Travel ideas")).toBeInTheDocument();
+    expect(within(sidebar).getByText("Q2 roadmap")).toBeInTheDocument();
+    expect(within(sidebar).queryByText("Travel ideas")).not.toBeInTheDocument();
+
+    fireEvent.change(screen.getByRole("textbox", { name: "Search chats" }), {
+      target: { value: "road q2" },
+    });
+
+    expect(within(sidebar).getByText("Q2 roadmap")).toBeInTheDocument();
+    expect(within(sidebar).queryByText("Travel ideas")).not.toBeInTheDocument();
   });
 
   it("opens a blank start page without creating an empty chat", async () => {

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

@@ -8,6 +8,7 @@ import { ClientProvider } from "@/providers/ClientProvider";
 function makeClient() {
   const errorHandlers = new Set<(err: { kind: string }) => void>();
   const chatHandlers = new Map<string, Set<(ev: import("@/lib/types").InboundEvent) => void>>();
+  const sessionUpdateHandlers = new Set<(chatId: string) => void>();
   return {
     status: "open" as const,
     defaultChatId: null as string | null,
@@ -30,12 +31,21 @@ function makeClient() {
         errorHandlers.delete(handler);
       };
     },
+    onSessionUpdate: (handler: (chatId: string) => void) => {
+      sessionUpdateHandlers.add(handler);
+      return () => {
+        sessionUpdateHandlers.delete(handler);
+      };
+    },
     _emitError(err: { kind: string }) {
       for (const h of errorHandlers) h(err);
     },
     _emitChat(chatId: string, ev: import("@/lib/types").InboundEvent) {
       for (const h of chatHandlers.get(chatId) ?? []) h(ev);
     },
+    _emitSessionUpdate(chatId: string) {
+      for (const h of sessionUpdateHandlers) h(chatId);
+    },
     sendMessage: vi.fn(),
     newChat: vi.fn(),
     attach: vi.fn(),
@@ -573,6 +583,134 @@ describe("ThreadShell", () => {
     await waitFor(() => expect(screen.getByText("live assistant reply")).toBeInTheDocument());
   });
 
+  it("replaces live streamed content with canonical history after turn end", async () => {
+    const client = makeClient();
+    let historyCalls = 0;
+    vi.stubGlobal(
+      "fetch",
+      vi.fn(async (input: RequestInfo | URL) => {
+        const url = String(input);
+        if (url.includes("websocket%3Achat-a/messages")) {
+          historyCalls += 1;
+          return httpJson({
+            key: "websocket:chat-a",
+            created_at: null,
+            updated_at: null,
+            messages: historyCalls === 1
+              ? [{ role: "user", content: "question" }]
+              : [
+                  { role: "user", content: "question" },
+                  { role: "assistant", content: "canonical markdown answer" },
+                ],
+          });
+        }
+        return {
+          ok: false,
+          status: 404,
+          json: async () => ({}),
+        };
+      }),
+    );
+
+    render(
+      wrap(
+        client,
+        <ThreadShell
+          session={session("chat-a")}
+          title="Chat chat-a"
+          onToggleSidebar={() => {}}
+          onNewChat={() => {}}
+        />,
+      ),
+    );
+
+    await waitFor(() => expect(screen.getByText("question")).toBeInTheDocument());
+    await act(async () => {
+      client._emitChat("chat-a", {
+        event: "delta",
+        chat_id: "chat-a",
+        text: "live half-parsed | markdown",
+      });
+      client._emitChat("chat-a", {
+        event: "turn_end",
+        chat_id: "chat-a",
+      });
+    });
+
+    await waitFor(() => expect(screen.getByText("canonical markdown answer")).toBeInTheDocument());
+    expect(screen.queryByText("live half-parsed | markdown")).not.toBeInTheDocument();
+  });
+
+  it("scrolls to the bottom after loading a session from the blank new-chat page", async () => {
+    const client = makeClient();
+    const scrollIntoView = vi.fn();
+    const originalScrollIntoView = HTMLElement.prototype.scrollIntoView;
+    HTMLElement.prototype.scrollIntoView = scrollIntoView;
+    vi.stubGlobal(
+      "fetch",
+      vi.fn(async (input: RequestInfo | URL) => {
+        const url = String(input);
+        if (url.includes("websocket%3Achat-a/messages")) {
+          return httpJson({
+            key: "websocket:chat-a",
+            created_at: null,
+            updated_at: null,
+            messages: [
+              { role: "user", content: "question" },
+              { role: "assistant", content: "loaded answer" },
+            ],
+          });
+        }
+        return {
+          ok: false,
+          status: 404,
+          json: async () => ({}),
+        };
+      }),
+    );
+
+    try {
+      const { rerender } = render(
+        wrap(
+          client,
+          <ThreadShell
+            session={null}
+            title="nanobot"
+            onToggleSidebar={() => {}}
+            onNewChat={() => {}}
+          />,
+        ),
+      );
+
+      expect(screen.getByText("What can I do for you?")).toBeInTheDocument();
+      scrollIntoView.mockClear();
+
+      await act(async () => {
+        rerender(
+          wrap(
+            client,
+            <ThreadShell
+              session={session("chat-a")}
+              title="Chat chat-a"
+              onToggleSidebar={() => {}}
+              onNewChat={() => {}}
+            />,
+          ),
+        );
+      });
+
+      await waitFor(() => expect(screen.getByText("loaded answer")).toBeInTheDocument());
+      await waitFor(() =>
+        expect(scrollIntoView).toHaveBeenCalledWith({
+          block: "end",
+          behavior: "smooth",
+        }),
+      );
+    } finally {
+      HTMLElement.prototype.scrollIntoView = originalScrollIntoView;
+    }
+  });
+
   it("opens slash commands on the blank welcome page", async () => {
     const client = makeClient();
     vi.stubGlobal(

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

@@ -0,0 +1,164 @@
+import { act, render, waitFor } from "@testing-library/react";
+import { describe, expect, it, vi } from "vitest";
+
+import { ThreadViewport } from "@/components/thread/ThreadViewport";
+import type { UIMessage } from "@/lib/types";
+
+const messages: UIMessage[] = [
+  {
+    id: "u1",
+    role: "user",
+    content: "hello",
+    createdAt: Date.now(),
+  },
+];
+
+const emptyMessages: UIMessage[] = [];
+
+describe("ThreadViewport", () => {
+  it("resets to the bottom when opening a different conversation", async () => {
+    const scrollIntoView = vi.fn();
+    const originalScrollIntoView = HTMLElement.prototype.scrollIntoView;
+    HTMLElement.prototype.scrollIntoView = scrollIntoView;
+
+    try {
+      const { container, rerender } = render(
+        <ThreadViewport
+          messages={messages}
+          isStreaming={false}
+          composer={<div />}
+          conversationKey="chat-a"
+        />,
+      );
+      const scroller = container.firstElementChild?.firstElementChild as HTMLElement;
+      Object.defineProperties(scroller, {
+        scrollHeight: { configurable: true, value: 2400 },
+        clientHeight: { configurable: true, value: 600 },
+        scrollTop: { configurable: true, value: 0 },
+      });
+      act(() => {
+        scroller.dispatchEvent(new Event("scroll"));
+      });
+      scrollIntoView.mockClear();
+
+      rerender(
+        <ThreadViewport
+          messages={messages}
+          isStreaming={false}
+          composer={<div />}
+          conversationKey="chat-b"
+        />,
+      );
+
+      await waitFor(() =>
+        expect(scrollIntoView).toHaveBeenCalledWith({
+          block: "end",
+          behavior: "auto",
+        }),
+      );
+    } finally {
+      HTMLElement.prototype.scrollIntoView = originalScrollIntoView;
+    }
+  });
+
+  it("waits for hydrated messages before fulfilling open-chat bottom scroll", async () => {
+    const scrollIntoView = vi.fn();
+    const originalScrollIntoView = HTMLElement.prototype.scrollIntoView;
+    HTMLElement.prototype.scrollIntoView = scrollIntoView;
+
+    try {
+      const { container, rerender } = render(
+        <ThreadViewport
+          messages={emptyMessages}
+          isStreaming={false}
+          composer={<div />}
+          conversationKey={null}
+        />,
+      );
+      const scroller = container.firstElementChild?.firstElementChild as HTMLElement;
+      Object.defineProperty(scroller, "scrollHeight", {
+        configurable: true,
+        value: 0,
+      });
+      scrollIntoView.mockClear();
+
+      rerender(
+        <ThreadViewport
+          messages={emptyMessages}
+          isStreaming={false}
+          composer={<div />}
+          conversationKey="chat-a"
+        />,
+      );
+      expect(scrollIntoView).toHaveBeenCalledWith({
+        block: "end",
+        behavior: "auto",
+      });
+
+      Object.defineProperty(scroller, "scrollHeight", {
+        configurable: true,
+        value: 2400,
+      });
+      scrollIntoView.mockClear();
+
+      rerender(
+        <ThreadViewport
+          messages={messages}
+          isStreaming={false}
+          composer={<div />}
+          conversationKey="chat-a"
+        />,
+      );
+
+      await waitFor(() =>
+        expect(scrollIntoView).toHaveBeenCalledWith({
+          block: "end",
+          behavior: "auto",
+        }),
+      );
+    } finally {
+      HTMLElement.prototype.scrollIntoView = originalScrollIntoView;
+    }
+  });
+
+  it("scrolls to the bottom when explicitly signalled after send", async () => {
+    const scrollIntoView = vi.fn();
+    const originalScrollIntoView = HTMLElement.prototype.scrollIntoView;
+    HTMLElement.prototype.scrollIntoView = scrollIntoView;
+
+    try {
+      const { container, rerender } = render(
+        <ThreadViewport
+          messages={messages}
+          isStreaming={false}
+          composer={<div />}
+          scrollToBottomSignal={0}
+        />,
+      );
+      const scroller = container.firstElementChild?.firstElementChild as HTMLElement;
+      Object.defineProperty(scroller, "scrollHeight", {
+        configurable: true,
+        value: 2400,
+      });
+      scrollIntoView.mockClear();
+
+      rerender(
+        <ThreadViewport
+          messages={messages}
+          isStreaming={false}
+          composer={<div />}
+          scrollToBottomSignal={1}
+        />,
+      );
+
+      await waitFor(() =>
+        expect(scrollIntoView).toHaveBeenCalledWith({
+          block: "end",
+          behavior: "smooth",
+        }),
+      );
+    } finally {
+      HTMLElement.prototype.scrollIntoView = originalScrollIntoView;
+    }
+  });
+});

webui/src/tests/useNanobotStream.test.tsx

@@ -113,6 +113,43 @@ describe("useNanobotStream", () => {
     expect(result.current.messages[1].kind).toBeUndefined();
   });
 
+  it("renders live tool traces from structured tool events", () => {
+    const fake = fakeClient();
+    const { result } = renderHook(() => useNanobotStream("chat-tool-events", EMPTY_MESSAGES), {
+      wrapper: wrap(fake.client),
+    });
+
+    act(() => {
+      fake.emit("chat-tool-events", {
+        event: "message",
+        chat_id: "chat-tool-events",
+        text: 'search "hermes"',
+        kind: "tool_hint",
+        tool_events: [
+          {
+            phase: "start",
+            name: "web_search",
+            arguments: { query: "NousResearch hermes-agent", count: 8 },
+          },
+          {
+            phase: "start",
+            name: "web_search",
+            arguments: { query: "hermes-agent GitHub stars", count: 8 },
+          },
+        ],
+      });
+    });
+
+    expect(result.current.messages).toHaveLength(1);
+    expect(result.current.messages[0].traces).toEqual([
+      'web_search({"query":"NousResearch hermes-agent","count":8})',
+      'web_search({"query":"hermes-agent GitHub stars","count":8})',
+    ]);
+    expect(result.current.messages[0].content).toBe(
+      'web_search({"query":"hermes-agent GitHub stars","count":8})',
+    );
+  });
+
   it("accumulates reasoning_delta chunks on a placeholder until reasoning_end", () => {
     const fake = fakeClient();
     const { result } = renderHook(() => useNanobotStream("chat-r", EMPTY_MESSAGES), {
@@ -315,6 +352,148 @@ describe("useNanobotStream", () => {
     expect(result.current.messages[2].reasoning).toBe("Second reasoning.");
   });
 
+  it("keeps tool-call reasoning before the matching live tool trace", () => {
+    const fake = fakeClient();
+    const { result } = renderHook(() => useNanobotStream("chat-tool-reasoning", EMPTY_MESSAGES), {
+      wrapper: wrap(fake.client),
+    });
+
+    act(() => {
+      fake.emit("chat-tool-reasoning", {
+        event: "reasoning_delta",
+        chat_id: "chat-tool-reasoning",
+        text: "I should search first.",
+      });
+      fake.emit("chat-tool-reasoning", {
+        event: "reasoning_end",
+        chat_id: "chat-tool-reasoning",
+      });
+      fake.emit("chat-tool-reasoning", {
+        event: "message",
+        chat_id: "chat-tool-reasoning",
+        text: "web_search({\"query\":\"hermes\"})",
+        kind: "tool_hint",
+      });
+      fake.emit("chat-tool-reasoning", {
+        event: "turn_end",
+        chat_id: "chat-tool-reasoning",
+      });
+    });
+
+    expect(result.current.messages).toHaveLength(2);
+    expect(result.current.messages[0]).toMatchObject({
+      role: "assistant",
+      content: "",
+      reasoning: "I should search first.",
+      reasoningStreaming: false,
+      isStreaming: false,
+    });
+    expect(result.current.messages[1]).toMatchObject({
+      role: "tool",
+      kind: "trace",
+      traces: ["web_search({\"query\":\"hermes\"})"],
+    });
+  });
+
+  it("absorbs non-streamed final answers into the preceding reasoning placeholder", () => {
+    const fake = fakeClient();
+    const { result } = renderHook(() => useNanobotStream("chat-final-reasoning", EMPTY_MESSAGES), {
+      wrapper: wrap(fake.client),
+    });
+
+    act(() => {
+      fake.emit("chat-final-reasoning", {
+        event: "message",
+        chat_id: "chat-final-reasoning",
+        text: "web_search({\"query\":\"hermes\"})",
+        kind: "tool_hint",
+      });
+      fake.emit("chat-final-reasoning", {
+        event: "reasoning_delta",
+        chat_id: "chat-final-reasoning",
+        text: "Got results; now summarize.",
+      });
+      fake.emit("chat-final-reasoning", {
+        event: "reasoning_end",
+        chat_id: "chat-final-reasoning",
+      });
+      fake.emit("chat-final-reasoning", {
+        event: "message",
+        chat_id: "chat-final-reasoning",
+        text: "Hermes is an open-source agent project.",
+      });
+      fake.emit("chat-final-reasoning", {
+        event: "turn_end",
+        chat_id: "chat-final-reasoning",
+      });
+    });
+
+    expect(result.current.messages).toHaveLength(2);
+    expect(result.current.messages[0]).toMatchObject({
+      role: "tool",
+      kind: "trace",
+    });
+    expect(result.current.messages[1]).toMatchObject({
+      role: "assistant",
+      content: "Hermes is an open-source agent project.",
+      reasoning: "Got results; now summarize.",
+      reasoningStreaming: false,
+      isStreaming: false,
+    });
+  });
+
+  it("prunes reasoning-only placeholders when a turn ends without an answer", () => {
+    const fake = fakeClient();
+    const { result } = renderHook(() => useNanobotStream("chat-empty-thinking", EMPTY_MESSAGES), {
+      wrapper: wrap(fake.client),
+    });
+
+    act(() => {
+      fake.emit("chat-empty-thinking", {
+        event: "reasoning_delta",
+        chat_id: "chat-empty-thinking",
+        text: "thinking without final text",
+      });
+      fake.emit("chat-empty-thinking", {
+        event: "reasoning_end",
+        chat_id: "chat-empty-thinking",
+      });
+      fake.emit("chat-empty-thinking", {
+        event: "turn_end",
+        chat_id: "chat-empty-thinking",
+      });
+    });
+
+    expect(result.current.messages).toHaveLength(0);
+    expect(result.current.isStreaming).toBe(false);
+  });
+
+  it("drops stale reasoning-only placeholders before sending the next user turn", () => {
+    const fake = fakeClient();
+    const initialMessages = [
+      {
+        id: "stale-thinking",
+        role: "assistant" as const,
+        content: "",
+        reasoning: "leftover thinking",
+        reasoningStreaming: false,
+        createdAt: Date.now(),
+      },
+    ];
+    const { result } = renderHook(
+      () => useNanobotStream("chat-stale-thinking", initialMessages),
+      { wrapper: wrap(fake.client) },
+    );
+
+    act(() => {
+      result.current.send("fine");
+    });
+
+    expect(result.current.messages).toHaveLength(1);
+    expect(result.current.messages[0].role).toBe("user");
+    expect(result.current.messages[0].content).toBe("fine");
+  });
+
   it("attaches assistant media_urls to complete messages", () => {
     const fake = fakeClient();
     const { result } = renderHook(() => useNanobotStream("chat-m", EMPTY_MESSAGES), {

webui/src/tests/useSessions.test.tsx

@@ -245,6 +245,30 @@ describe("useSessions", () => {
     expect(result.current.messages[0].reasoningStreaming).toBe(false);
   });
 
+  it("drops replayed assistant turns that only contain reasoning", async () => {
+    vi.mocked(api.fetchSessionMessages).mockResolvedValue({
+      key: "websocket:chat-empty-reasoning",
+      created_at: "2026-04-20T10:00:00Z",
+      updated_at: "2026-04-20T10:05:00Z",
+      messages: [
+        {
+          role: "assistant",
+          content: "",
+          timestamp: "2026-04-20T10:00:01Z",
+          reasoning_content: "orphan reasoning",
+        },
+      ],
+    });
+
+    const { result } = renderHook(() => useSessionHistory("websocket:chat-empty-reasoning"), {
+      wrapper: wrap(fakeClient()),
+    });
+
+    await waitFor(() => expect(result.current.loading).toBe(false));
+
+    expect(result.current.messages).toHaveLength(0);
+  });
+
   it("hydrates historical assistant tool calls into a replay trace row", async () => {
     vi.mocked(api.fetchSessionMessages).mockResolvedValue({
       key: "websocket:chat-tools",