feat: collapse finished agent work into a Worked for X dropdown (#1509)

Once an agent turn finishes, its reasoning/tool/exploration steps collapse
behind a single "Worked for …" toggle so the chat shows only the final reply,
mirroring Devin's transcript. Work stays expanded live and auto-collapses on
completion; the final reply text/cards remain visible.

Co-authored-by: open-swe[bot] <open-swe@users.noreply.github.com>

ui/src/components/agents/messages/AgentMessage.tsx

@@ -11,8 +11,32 @@ import { buildRenderItems, summarizeExploration, type RenderItem } from "./rende
 import { SubagentGroup } from "@/components/agents/subagents";
 import { summarizeChangedFiles } from "./summarizeChangedFiles";
 import { TurnChangedFilesCard } from "./TurnChangedFilesCard";
+import { WorkSummary } from "./WorkSummary";
 import type { ApprovalCallbacks, ChangedFileSummaryItem } from "./types";
 
+/**
+ * Render-item types kept visible (not collapsed) when a turn finishes — the
+ * agent's actual reply to the user. Everything else is "work".
+ */
+const REPLY_ITEM_TYPES = new Set<RenderItem["type"]>(["text-chunk", "reply-item"]);
+
+/**
+ * Split a finished turn's items into collapsible work and the trailing reply,
+ * where the reply is the maximal suffix made up solely of reply/text items.
+ */
+function splitWorkAndReply(items: RenderItem[]): {
+  workItems: RenderItem[];
+  replyItems: RenderItem[];
+} {
+  let splitIndex = items.length;
+  while (splitIndex > 0) {
+    const prev = items[splitIndex - 1];
+    if (!prev || !REPLY_ITEM_TYPES.has(prev.type)) break;
+    splitIndex -= 1;
+  }
+  return { workItems: items.slice(0, splitIndex), replyItems: items.slice(splitIndex) };
+}
+
 export function AgentMessage({
   message,
   isStreaming,
@@ -95,13 +119,41 @@ export function AgentMessage({
     wasExplorationLiveRef.current = false;
   }, [hasExploredGroups, isStreaming, exploredGroupIds, message.id]);
 
-  return (
+  // Measure wall-clock work time for live runs (most accurate); fall back to
-    <div className="my-2 min-w-0 space-y-2">
+  // the turn's first→last message timestamps for transcripts loaded from state.
-      {renderItems.map((item, index) => {
+  const [measuredDurationMs, setMeasuredDurationMs] = useState<number | null>(null);
-        switch (item.type) {
+  const workStartRef = useRef<number | null>(null);
+  const wasStreamingRef = useRef(false);
+  useEffect(() => {
+    if (isStreaming) {
+      if (workStartRef.current === null) workStartRef.current = Date.now();
+      wasStreamingRef.current = true;
+      return;
+    }
+    if (wasStreamingRef.current && workStartRef.current !== null) {
+      setMeasuredDurationMs(Date.now() - workStartRef.current);
+      wasStreamingRef.current = false;
+    }
+  }, [isStreaming]);
+
+  const workDurationMs = useMemo(() => {
+    if (measuredDurationMs !== null) return measuredDurationMs;
+    if (!message.startedAt) return null;
+    const start = Date.parse(message.startedAt);
+    const end = Date.parse(message.timestamp);
+    if (!Number.isFinite(start) || !Number.isFinite(end)) return null;
+    const delta = end - start;
+    return delta > 0 ? delta : null;
+  }, [measuredDurationMs, message.startedAt, message.timestamp]);
+
+  const { workItems, replyItems } = useMemo(() => splitWorkAndReply(renderItems), [renderItems]);
+  const collapseWork = !isStreaming && workItems.length > 0;
+
+  const renderItem = (item: RenderItem, index: number, total: number) => {
+    switch (item.type) {
           case "reasoning-item": {
             const reasoningChunk = item.chunk.kind === "reasoning" ? item.chunk : null;
-            const isLastItem = index === renderItems.length - 1;
+            const isLastItem = index === total - 1;
             return (
               <div key={item.key} className="flex-1 min-w-0">
                 <ReasoningBlock
@@ -216,7 +268,22 @@ export function AgentMessage({
               </div>
             );
         }
-      })}
+  };
+
+  return (
+    <div className="my-2 min-w-0 space-y-2">
+      {collapseWork ? (
+        <>
+          <WorkSummary durationMs={workDurationMs}>
+            {workItems.map((item, index) => renderItem(item, index, workItems.length))}
+          </WorkSummary>
+          {replyItems.map((item, index) =>
+            renderItem(item, workItems.length + index, renderItems.length),
+          )}
+        </>
+      ) : (
+        renderItems.map((item, index) => renderItem(item, index, renderItems.length))
+      )}
 
       {changedFiles.length > 0 && !isStreaming && (
         <TurnChangedFilesCard

ui/src/components/agents/messages/ReasoningBlock.tsx

@@ -1,10 +1,7 @@
 import { useEffect, useRef, useState } from "react";
 import { ChevronRight } from "lucide-react";
 
-function formatElapsed(ms: number): string {
+import { formatElapsed } from "@/lib/utils";
-  const secs = Math.max(1, Math.ceil(ms / 1000));
-  return secs < 60 ? `${secs}s` : `${Math.floor(secs / 60)}m ${secs % 60}s`;
-}
 
 function reasoningLabel(elapsedMs: number | null): string {
   if (elapsedMs === null) return "Thought";

ui/src/components/agents/messages/ThinkingSpinner.tsx

@@ -1,5 +1,7 @@
 import { useEffect, useRef, useState } from "react";
 
+import { formatElapsed } from "@/lib/utils";
+
 const BUSY_TEXTS: { present: string; past: string }[] = [
   { present: "vibing...", past: "Vibed" },
   { present: "noodling...", past: "Noodled" },
@@ -14,11 +16,6 @@ const BUSY_TEXTS: { present: string; past: string }[] = [
   { present: "processing...", past: "Processed" },
 ];
 
-function formatElapsed(ms: number): string {
-  const secs = Math.max(1, Math.ceil(ms / 1000));
-  return secs < 60 ? `${secs}s` : `${Math.floor(secs / 60)}m ${secs % 60}s`;
-}
-
 const THINKING_SETTLE_MS = 300;
 
 export function ThinkingSpinner({

ui/src/components/agents/messages/WorkSummary.tsx

@@ -0,0 +1,43 @@
+import { useState, type ReactNode } from "react";
+import { ChevronRight } from "lucide-react";
+
+import { formatElapsed } from "@/lib/utils";
+
+/**
+ * Collapses a finished agent turn's working steps (reasoning, tool calls,
+ * exploration, edits, …) behind a single "Worked for …" toggle so the
+ * transcript shows only the final reply by default.
+ */
+export function WorkSummary({
+  durationMs,
+  children,
+}: {
+  durationMs: number | null;
+  children: ReactNode;
+}) {
+  const [expanded, setExpanded] = useState(false);
+  const label =
+    durationMs && durationMs >= 1000 ? `Worked for ${formatElapsed(durationMs)}` : "Worked";
+
+  return (
+    <div className="my-1">
+      <button
+        type="button"
+        onClick={() => setExpanded((value) => !value)}
+        className="flex items-center gap-1 text-left transition-opacity hover:opacity-90"
+        aria-expanded={expanded}
+      >
+        <ChevronRight
+          className={`h-3 w-3 text-[color:var(--ui-text-dim)] shrink-0 transition-transform ${expanded ? "rotate-90" : ""}`}
+          aria-hidden
+        />
+        <span className="text-xs text-[color:var(--ui-text-dim)]">{label}</span>
+      </button>
+      {expanded && (
+        <div className="mt-1 ml-1 space-y-2 border-l-2 border-[var(--ui-border)] pl-3">
+          {children}
+        </div>
+      )}
+    </div>
+  );
+}

ui/src/lib/agents/streamMessagesToUi.ts

@@ -79,7 +79,13 @@ function mergeTextChunks(chunks: Array<Chunk>): Array<Chunk> {
   return chunks.filter((c, i) => c.kind !== "text" || i === lastText);
 }
 
-type AgentTurn = { id: string; author: Message["author"]; timestamp: string; chunks: Array<Chunk> };
+type AgentTurn = {
+  id: string;
+  author: Message["author"];
+  timestamp: string;
+  startedAt: string;
+  chunks: Array<Chunk>;
+};
 
 function messageTimestamp(raw: BaseMessage): string {
   const msg = raw as unknown as Record<string, unknown>;
@@ -304,6 +310,7 @@ export function streamMessagesToUi(
         id: msgId,
         author: "agent",
         timestamp,
+        startedAt: timestamp,
         chunks: [...chunks],
       };
     } else {

ui/src/lib/agents/types.ts

@@ -138,6 +138,8 @@ export interface Message {
   id: string
   author: Author
   timestamp: string
+  /** Timestamp of the first message in an agent turn; used to derive work duration. */
+  startedAt?: string
   chunks: Array<Chunk>
   hidden?: boolean
 }

ui/src/lib/utils.ts

@@ -14,6 +14,14 @@ export function cn(...inputs: Array<ClassValue>) {
   return twMerge(clsx(inputs))
 }
 
+/**
+ * Format an elapsed duration in milliseconds as a compact string (e.g. "5s", "3m 20s").
+ */
+export function formatElapsed(ms: number): string {
+  const secs = Math.max(1, Math.ceil(ms / 1000));
+  return secs < 60 ? `${secs}s` : `${Math.floor(secs / 60)}m ${secs % 60}s`;
+}
+
 /**
  * Intl.RelativeTimeFormat instance for formatting relative times.
  */