fix webui tool trace dedupe

webui/src/hooks/useNanobotStream.ts

@@ -2,7 +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 { mergeUniqueToolTraceLines, toolTraceLinesFromEvents } from "@/lib/tool-traces";
 import type { StreamError } from "@/lib/nanobot-client";
 import type {
   InboundEvent,
@@ -652,10 +652,16 @@ export function useNanobotStream(
                 : last.content
                   ? [last.content]
                   : [];
+              const mergedLines = structuredLines.length > 0
+                ? mergeUniqueToolTraceLines(previousTraces, structuredLines)
+                : null;
+              if (mergedLines && !mergedLines.added) return prev;
               const merged: UIMessage = {
                 ...last,
-                traces: [...previousTraces, ...lines],
-                content: lines[lines.length - 1],
+                traces: mergedLines ? mergedLines.traces : [...previousTraces, ...lines],
+                content: mergedLines
+                  ? mergedLines.traces[mergedLines.traces.length - 1]
+                  : lines[lines.length - 1],
                 activitySegmentId: last.activitySegmentId ?? segmentId,
               };
               return [...prev.slice(0, -1), merged];

webui/src/lib/tool-traces.ts

@@ -44,20 +44,35 @@ const VALID_PHASES = new Set(["start", "end", "error"]);
 export function toolTraceLinesFromEvents(events: unknown): string[] {
   if (!Array.isArray(events)) return [];
   const seen = new Set<string>();
-  return events
-    .filter((event) => {
-      if (!event || typeof event !== "object") return false;
-      const phase = (event as { phase?: unknown }).phase;
-      if (!(phase && typeof phase === "string" && VALID_PHASES.has(phase))) {
-        return false;
-      }
-      const callId = (event as { call_id?: unknown }).call_id;
-      if (callId && typeof callId === "string") {
-        if (seen.has(callId)) return false;
-        seen.add(callId);
-      }
-      return true;
-    })
-    .map(formatToolCallTrace)
-    .filter((trace): trace is string => !!trace);
+  const lines: string[] = [];
+  for (const event of events) {
+    if (!event || typeof event !== "object") continue;
+    const phase = (event as { phase?: unknown }).phase;
+    if (!(phase && typeof phase === "string" && VALID_PHASES.has(phase))) continue;
+    const callId = (event as { call_id?: unknown }).call_id;
+    if (callId && typeof callId === "string") {
+      if (seen.has(callId)) continue;
+      seen.add(callId);
+    }
+    const line = formatToolCallTrace(event);
+    if (!line) continue;
+    lines.push(line);
+  }
+  return lines;
+}
+
+export function mergeUniqueToolTraceLines(
+  previousTraces: string[],
+  lines: string[],
+): { traces: string[]; added: boolean } {
+  const seen = new Set(previousTraces);
+  const traces = [...previousTraces];
+  let added = false;
+  for (const line of lines) {
+    if (seen.has(line)) continue;
+    seen.add(line);
+    traces.push(line);
+    added = true;
+  }
+  return { traces, added };
 }

webui/src/tests/useNanobotStream.test.tsx

@@ -308,6 +308,56 @@ describe("useNanobotStream", () => {
     );
   });
 
+  it("dedupes finish-phase tool events after their start trace", () => {
+    const fake = fakeClient();
+    const { result } = renderHook(() => useNanobotStream("chat-tool-finish", EMPTY_MESSAGES), {
+      wrapper: wrap(fake.client),
+    });
+
+    act(() => {
+      fake.emit("chat-tool-finish", {
+        event: "message",
+        chat_id: "chat-tool-finish",
+        text: 'exec({"cmd":"ls"})',
+        kind: "tool_hint",
+        tool_events: [{
+          phase: "start",
+          call_id: "call-exec",
+          name: "exec",
+          arguments: { cmd: "ls" },
+        }],
+      });
+      fake.emit("chat-tool-finish", {
+        event: "message",
+        chat_id: "chat-tool-finish",
+        text: "",
+        kind: "progress",
+        tool_events: [
+          {
+            phase: "end",
+            call_id: "call-exec",
+            name: "exec",
+            arguments: { cmd: "ls" },
+            result: "ok",
+          },
+          {
+            phase: "error",
+            call_id: "call-read",
+            name: "read_file",
+            arguments: { path: "notes.md" },
+            error: "missing",
+          },
+        ],
+      });
+    });
+
+    expect(result.current.messages).toHaveLength(1);
+    expect(result.current.messages[0].traces).toEqual([
+      'exec({"cmd":"ls"})',
+      'read_file({"path":"notes.md"})',
+    ]);
+  });
+
   it("renders live file_edit events as their own activity trace", () => {
     const fake = fakeClient();
     const { result } = renderHook(() => useNanobotStream("chat-file-edit", EMPTY_MESSAGES), {