perf: reduce active-turn chat rerenders during streaming

- Keep older assistant messages in the active turn stable while new content streams
- Prevent existing tool rows from rerendering when new tool activity is appended
- Tighten message and tool memo comparisons to isolate render work to changed rows

packages/ui/src/components/chat/ChatMessage.tsx

@@ -30,7 +30,7 @@ import type { TurnGroupingContext } from './lib/turns/types';
 import { copyTextToClipboard } from '@/lib/clipboard';
 import { FadeInOnReveal } from './message/FadeInOnReveal';
 import { streamPerfCount } from '@/stores/utils/streamDebug';
-import { areOptionalRenderRelevantMessagesEqual, areRenderRelevantMessageInfoEqual, areRenderRelevantPartsEqual } from './message/renderCompare';
+import { areOptionalRenderRelevantMessagesEqual, areRelevantTurnGroupingContextsEqual, areRenderRelevantMessageInfoEqual, areRenderRelevantPartsEqual } from './message/renderCompare';
 
 const ToolOutputDialog = React.lazy(() => import('./message/ToolOutputDialog'));
 
@@ -1129,12 +1129,14 @@ const ChatMessage: React.FC<ChatMessageProps> = ({
 };
 
 export default React.memo(ChatMessage, (prev, next) => {
+    const prevRole = deriveMessageRole(prev.message.info);
+
     return areRenderRelevantMessageInfoEqual(prev.message.info, next.message.info)
         && areRenderRelevantPartsEqual(prev.message.parts, next.message.parts)
         && areOptionalRenderRelevantMessagesEqual(prev.previousMessage, next.previousMessage)
         && areOptionalRenderRelevantMessagesEqual(prev.nextMessage, next.nextMessage)
         && prev.onContentChange === next.onContentChange
-        && prev.turnGroupingContext === next.turnGroupingContext
+        && areRelevantTurnGroupingContextsEqual(prev.turnGroupingContext, next.turnGroupingContext, prev.message.info.id, prevRole.isUser)
         && prev.assistantHeaderMessageId === next.assistantHeaderMessageId
         && prev.isInActiveTurn === next.isInActiveTurn
         && prev.activeStreamingPhase === next.activeStreamingPhase

packages/ui/src/components/chat/MessageList.tsx

@@ -3,7 +3,7 @@ import type { Part } from '@opencode-ai/sdk/v2';
 import { measureElement as measureVirtualElement, type VirtualItem, useVirtualizer } from '@tanstack/react-virtual';
 
 import ChatMessage from './ChatMessage';
-import { areOptionalRenderRelevantMessagesEqual, areRenderRelevantMessagesEqual } from './message/renderCompare';
+import { areOptionalRenderRelevantMessagesEqual, areRelevantTurnGroupingContextsEqual, areRenderRelevantMessagesEqual } from './message/renderCompare';
 import TurnItem from './components/TurnItem';
 import type { AnimationHandlers, ContentChangeReason } from '@/hooks/useChatScrollManager';
 import { filterSyntheticParts } from '@/lib/messages/synthetic';
@@ -480,15 +480,7 @@ const MessageRow = React.memo<MessageRowProps>(({
         && prev.onUserAnimationConsumed === next.onUserAnimationConsumed
         && prev.onContentChange === next.onContentChange
         && prev.scrollToBottom === next.scrollToBottom
-        && prevTurn?.turnId === nextTurn?.turnId
-        && prevTurn?.isFirstAssistantInTurn === nextTurn?.isFirstAssistantInTurn
-        && prevTurn?.isLastAssistantInTurn === nextTurn?.isLastAssistantInTurn
-        && prevTurn?.activityOwnerMessageId === nextTurn?.activityOwnerMessageId
-        && prevTurn?.isWorking === nextTurn?.isWorking
-        && prevTurn?.isGroupExpanded === nextTurn?.isGroupExpanded
-        && prevTurn?.toggleGroup === nextTurn?.toggleGroup
-        && prevTurn?.activityGroupSegments === nextTurn?.activityGroupSegments
-        && prevTurn?.activityParts === nextTurn?.activityParts
+        && areRelevantTurnGroupingContextsEqual(prevTurn, nextTurn, prev.message.info.id, resolveMessageRole(prev.message) === 'user')
         && prev.assistantHeaderMessageId === next.assistantHeaderMessageId
         && prev.isInActiveTurn === next.isInActiveTurn
         && prev.activeStreamingPhase === next.activeStreamingPhase

packages/ui/src/components/chat/message/parts/ProgressiveGroup.tsx

@@ -20,6 +20,7 @@ import { useDirectoryStore } from '@/stores/useDirectoryStore';
 import { useUIStore } from '@/stores/useUIStore';
 import ReasoningPart from './ReasoningPart';
 import JustificationBlock from './JustificationBlock';
+import { areRenderRelevantPartsEqual } from '../renderCompare';
 
 interface ProgressiveGroupProps {
     parts: TurnActivityPart[];
@@ -380,6 +381,115 @@ type AggregatedRow =
     | { type: 'justification'; activity: TurnActivityPart }
     | { type: 'tool-fallback'; activity: TurnActivityPart };
 
+interface ExpandableToolRowProps {
+    activity: TurnActivityPart;
+    isExpanded: boolean;
+    syntaxTheme: Record<string, React.CSSProperties>;
+    isMobile: boolean;
+    onToggleTool: (toolId: string) => void;
+    onShowPopup: (content: ToolPopupContent) => void;
+    onContentChange?: (reason?: ContentChangeReason) => void;
+    animateTailText: boolean;
+    animateRows: boolean;
+}
+
+const ExpandableToolRow: React.FC<ExpandableToolRowProps> = ({
+    activity,
+    isExpanded,
+    syntaxTheme,
+    isMobile,
+    onToggleTool,
+    onShowPopup,
+    onContentChange,
+    animateTailText,
+    animateRows,
+}) => {
+    const handleToggle = React.useCallback(() => {
+        onToggleTool(activity.id);
+    }, [activity.id, onToggleTool]);
+
+    const content = (
+        <ToolPart
+            part={activity.part as ToolPartType}
+            isExpanded={isExpanded}
+            onToggle={handleToggle}
+            syntaxTheme={syntaxTheme}
+            isMobile={isMobile}
+            onContentChange={onContentChange}
+            onShowPopup={onShowPopup}
+            animateTailText={animateTailText}
+        />
+    );
+
+    const maybeWrapped = animateTailText ? (
+        <ToolRevealOnMount animate={true} wipe>
+            {content}
+        </ToolRevealOnMount>
+    ) : content;
+
+    if (!animateRows) {
+        return maybeWrapped;
+    }
+
+    return <FadeInOnReveal>{maybeWrapped}</FadeInOnReveal>;
+};
+
+const MemoExpandableToolRow = React.memo(ExpandableToolRow, (prev, next) => {
+    return prev.isExpanded === next.isExpanded
+        && prev.syntaxTheme === next.syntaxTheme
+        && prev.isMobile === next.isMobile
+        && prev.onToggleTool === next.onToggleTool
+        && prev.onShowPopup === next.onShowPopup
+        && prev.onContentChange === next.onContentChange
+        && prev.animateTailText === next.animateTailText
+        && prev.animateRows === next.animateRows
+        && prev.activity.id === next.activity.id
+        && prev.activity.kind === next.activity.kind
+        && prev.activity.endedAt === next.activity.endedAt
+        && areRenderRelevantPartsEqual([prev.activity.part], [next.activity.part]);
+});
+
+interface StaticGroupedToolRowProps {
+    toolName: string;
+    activities: TurnActivityPart[];
+    animateTailText: boolean;
+    animateRows: boolean;
+}
+
+const StaticGroupedToolRow: React.FC<StaticGroupedToolRowProps> = ({
+    toolName,
+    activities,
+    animateTailText,
+    animateRows,
+}) => {
+    const content = (
+        <StaticToolRow
+            toolName={toolName}
+            activities={activities}
+            animateTailText={animateTailText}
+        />
+    );
+
+    const maybeWrapped = animateTailText ? (
+        <ToolRevealOnMount animate={true} wipe>
+            {content}
+        </ToolRevealOnMount>
+    ) : content;
+
+    if (!animateRows) {
+        return maybeWrapped;
+    }
+
+    return <FadeInOnReveal>{maybeWrapped}</FadeInOnReveal>;
+};
+
+const MemoStaticGroupedToolRow = React.memo(StaticGroupedToolRow, (prev, next) => {
+    return prev.toolName === next.toolName
+        && prev.animateTailText === next.animateTailText
+        && prev.animateRows === next.animateRows
+        && areActivityListsEqual(prev.activities, next.activities);
+});
+
 /**
  * Aggregate sorted activity parts into display rows.
  * Static tools are rendered as one row per call.
@@ -440,7 +550,36 @@ const aggregateRows = (parts: TurnActivityPart[]): AggregatedRow[] => {
  * Render a static aggregated tool row.
  * Shows: [icon] DisplayName file1.tsx file2.tsx ...
  */
-export const StaticToolRow: React.FC<{
+const areActivityListsEqual = (left: TurnActivityPart[], right: TurnActivityPart[]): boolean => {
+    if (left === right) {
+        return true;
+    }
+
+    if (left.length !== right.length) {
+        return false;
+    }
+
+    for (let index = 0; index < left.length; index += 1) {
+        const leftActivity = left[index];
+        const rightActivity = right[index];
+
+        if (leftActivity.id !== rightActivity.id) {
+            return false;
+        }
+
+        if (leftActivity.kind !== rightActivity.kind || leftActivity.endedAt !== rightActivity.endedAt) {
+            return false;
+        }
+
+        if (!areRenderRelevantPartsEqual([leftActivity.part], [rightActivity.part])) {
+            return false;
+        }
+    }
+
+    return true;
+};
+
+const StaticToolRowInner: React.FC<{
     toolName: string;
     activities: TurnActivityPart[];
     animateTailText: boolean;
@@ -590,6 +729,12 @@ export const StaticToolRow: React.FC<{
     );
 };
 
+export const StaticToolRow = React.memo(StaticToolRowInner, (prev, next) => {
+    return prev.toolName === next.toolName
+        && prev.animateTailText === next.animateTailText
+        && areActivityListsEqual(prev.activities, next.activities);
+});
+
 /**
  * Inline reasoning text block — rendered as dimmed italic markdown.
  */
@@ -683,18 +828,6 @@ const ProgressiveGroup: React.FC<ProgressiveGroupProps> = ({
         return <FadeInOnReveal key={key}>{content}</FadeInOnReveal>;
     };
 
-    const renderToolRow = (key: string, content: React.ReactNode, animate: boolean) => {
-        if (!animate) {
-            return wrapRow(key, content);
-        }
-        return wrapRow(
-            key,
-            <ToolRevealOnMount animate={true} wipe>
-                {content}
-            </ToolRevealOnMount>
-        );
-    };
-
     const renderedRows = shouldRenderRows
         ? visibleRows.map((row, index) => {
         switch (row.type) {
@@ -721,52 +854,46 @@ const ProgressiveGroup: React.FC<ProgressiveGroupProps> = ({
                 );
 
             case 'tool-expandable':
-                return renderToolRow(
-                    row.activity.id,
-                    <>
-                        <ToolPart
-                            part={row.activity.part as ToolPartType}
-                            isExpanded={expandedTools.has(row.activity.id)}
-                            onToggle={() => onToggleTool(row.activity.id)}
-                            syntaxTheme={syntaxTheme}
-                            isMobile={isMobile}
-                            onContentChange={onContentChange}
-                            onShowPopup={onShowPopup}
-                            animateTailText={Boolean(animatedToolIds?.has(row.activity.id))}
-                        />
-                    </>,
-                    Boolean(animatedToolIds?.has(row.activity.id))
+                return (
+                    <MemoExpandableToolRow
+                        key={row.activity.id}
+                        activity={row.activity}
+                        isExpanded={expandedTools.has(row.activity.id)}
+                        syntaxTheme={syntaxTheme}
+                        isMobile={isMobile}
+                        onToggleTool={onToggleTool}
+                        onShowPopup={onShowPopup}
+                        onContentChange={onContentChange}
+                        animateTailText={Boolean(animatedToolIds?.has(row.activity.id))}
+                        animateRows={animateRows}
+                    />
                 );
 
             case 'tool-static-group':
-                return renderToolRow(
-                    `static-${row.toolName}-${row.activities[0]?.id ?? index}`,
-                    <>
-                        <StaticToolRow
-                            toolName={row.toolName}
-                            activities={row.activities}
-                            animateTailText={row.activities.some((activity) => animatedToolIds?.has(activity.id))}
-                        />
-                    </>,
-                    row.activities.some((activity) => animatedToolIds?.has(activity.id))
+                return (
+                    <MemoStaticGroupedToolRow
+                        key={`static-${row.toolName}-${row.activities[0]?.id ?? index}`}
+                        toolName={row.toolName}
+                        activities={row.activities}
+                        animateTailText={row.activities.some((activity) => animatedToolIds?.has(activity.id))}
+                        animateRows={animateRows}
+                    />
                 );
 
             case 'tool-fallback':
-                return renderToolRow(
-                    row.activity.id,
-                    <>
-                        <ToolPart
-                            part={row.activity.part as ToolPartType}
-                            isExpanded={expandedTools.has(row.activity.id)}
-                            onToggle={() => onToggleTool(row.activity.id)}
-                            syntaxTheme={syntaxTheme}
-                            isMobile={isMobile}
-                            onContentChange={onContentChange}
-                            onShowPopup={onShowPopup}
-                            animateTailText={Boolean(animatedToolIds?.has(row.activity.id))}
-                        />
-                    </>,
-                    Boolean(animatedToolIds?.has(row.activity.id))
+                return (
+                    <MemoExpandableToolRow
+                        key={row.activity.id}
+                        activity={row.activity}
+                        isExpanded={expandedTools.has(row.activity.id)}
+                        syntaxTheme={syntaxTheme}
+                        isMobile={isMobile}
+                        onToggleTool={onToggleTool}
+                        onShowPopup={onShowPopup}
+                        onContentChange={onContentChange}
+                        animateTailText={Boolean(animatedToolIds?.has(row.activity.id))}
+                        animateRows={animateRows}
+                    />
                 );
 
             default:

packages/ui/src/components/chat/message/parts/ToolPart.tsx

@@ -40,6 +40,7 @@ import { ToolRevealOnMount } from './ToolRevealOnMount';
 import { getToolIcon } from './toolPresentation';
 import { useDurationTickerNow } from './useDurationTicker';
 import { resolveFallbackTaskSessionId } from './resolveFallbackTaskSessionId';
+import { areRenderRelevantPartsEqual } from '../renderCompare';
 
 type ToolStateWithMetadata = ToolStateUnion & { metadata?: Record<string, unknown>; input?: Record<string, unknown>; output?: string; error?: string; time?: { start: number; end?: number } };
 
@@ -2472,4 +2473,12 @@ const ToolPart: React.FC<ToolPartProps> = ({
     );
 };
 
-export default ToolPart;
+export default React.memo(ToolPart, (prev, next) => {
+    return areRenderRelevantPartsEqual([prev.part], [next.part])
+        && prev.isExpanded === next.isExpanded
+        && prev.syntaxTheme === next.syntaxTheme
+        && prev.isMobile === next.isMobile
+        && prev.onContentChange === next.onContentChange
+        && prev.onShowPopup === next.onShowPopup
+        && prev.animateTailText === next.animateTailText;
+});

packages/ui/src/components/chat/message/renderCompare.ts

@@ -1,4 +1,5 @@
 import type { Message, Part } from '@opencode-ai/sdk/v2';
+import type { TurnActivityGroup, TurnActivityRecord, TurnDiffStats, TurnGroupingContext } from '../lib/turns/types';
 
 type MessageRecord = {
   info: Message;
@@ -113,3 +114,171 @@ export const areOptionalRenderRelevantMessagesEqual = (left?: MessageRecord, rig
   }
   return areRenderRelevantMessagesEqual(left, right);
 };
+
+const areTurnDiffStatsEqual = (left?: TurnDiffStats, right?: TurnDiffStats): boolean => {
+  if (!left || !right) {
+    return left === right;
+  }
+
+  return left.additions === right.additions
+    && left.deletions === right.deletions
+    && left.files === right.files;
+};
+
+const areTurnActivityRecordsEqual = (left: TurnActivityRecord, right: TurnActivityRecord): boolean => {
+  return left.id === right.id
+    && left.messageId === right.messageId
+    && left.kind === right.kind
+    && left.partIndex === right.partIndex
+    && left.endedAt === right.endedAt
+    && areRenderRelevantPartsEqual([left.part], [right.part]);
+};
+
+const areRelevantActivityPartsEqual = (
+  left: TurnActivityRecord[] | undefined,
+  right: TurnActivityRecord[] | undefined,
+  messageId: string,
+): boolean => {
+  let leftIndex = 0;
+  let rightIndex = 0;
+
+  while (true) {
+    while (leftIndex < (left?.length ?? 0) && left?.[leftIndex]?.messageId !== messageId) {
+      leftIndex += 1;
+    }
+    while (rightIndex < (right?.length ?? 0) && right?.[rightIndex]?.messageId !== messageId) {
+      rightIndex += 1;
+    }
+
+    const leftRecord = left?.[leftIndex];
+    const rightRecord = right?.[rightIndex];
+
+    if (!leftRecord || !rightRecord) {
+      return leftRecord === rightRecord;
+    }
+
+    if (!areTurnActivityRecordsEqual(leftRecord, rightRecord)) {
+      return false;
+    }
+
+    leftIndex += 1;
+    rightIndex += 1;
+  }
+};
+
+const areTurnActivityGroupsEqual = (left: TurnActivityGroup, right: TurnActivityGroup): boolean => {
+  if (left.id !== right.id || left.anchorMessageId !== right.anchorMessageId || left.afterToolPartId !== right.afterToolPartId) {
+    return false;
+  }
+
+  if (left.parts.length !== right.parts.length) {
+    return false;
+  }
+
+  for (let index = 0; index < left.parts.length; index += 1) {
+    if (!areTurnActivityRecordsEqual(left.parts[index], right.parts[index])) {
+      return false;
+    }
+  }
+
+  return true;
+};
+
+const hasRelevantActivitySegments = (segments: TurnActivityGroup[] | undefined, messageId: string): boolean => {
+  return Boolean(segments?.some((segment) => segment.anchorMessageId === messageId));
+};
+
+const areRelevantActivitySegmentsEqual = (
+  left: TurnActivityGroup[] | undefined,
+  right: TurnActivityGroup[] | undefined,
+  messageId: string,
+): boolean => {
+  let leftIndex = 0;
+  let rightIndex = 0;
+
+  while (true) {
+    while (leftIndex < (left?.length ?? 0) && left?.[leftIndex]?.anchorMessageId !== messageId) {
+      leftIndex += 1;
+    }
+    while (rightIndex < (right?.length ?? 0) && right?.[rightIndex]?.anchorMessageId !== messageId) {
+      rightIndex += 1;
+    }
+
+    const leftSegment = left?.[leftIndex];
+    const rightSegment = right?.[rightIndex];
+
+    if (!leftSegment || !rightSegment) {
+      return leftSegment === rightSegment;
+    }
+
+    if (!areTurnActivityGroupsEqual(leftSegment, rightSegment)) {
+      return false;
+    }
+
+    leftIndex += 1;
+    rightIndex += 1;
+  }
+};
+
+export const areRelevantTurnGroupingContextsEqual = (
+  left: TurnGroupingContext | undefined,
+  right: TurnGroupingContext | undefined,
+  messageId: string,
+  isUserMessage: boolean,
+): boolean => {
+  if (left === right) {
+    return true;
+  }
+
+  if (!left || !right) {
+    return left === right;
+  }
+
+  if (isUserMessage) {
+    return true;
+  }
+
+  if (left.turnId !== right.turnId) return false;
+  if (left.isFirstAssistantInTurn !== right.isFirstAssistantInTurn) return false;
+  if (left.isLastAssistantInTurn !== right.isLastAssistantInTurn) return false;
+  if (left.isWorking !== right.isWorking) return false;
+  if (left.hasTools !== right.hasTools) return false;
+  if (left.hasReasoning !== right.hasReasoning) return false;
+  if (left.userMessageCreatedAt !== right.userMessageCreatedAt) return false;
+  if (left.userMessageVariant !== right.userMessageVariant) return false;
+
+  const headerRelevant = left.headerMessageId === messageId || right.headerMessageId === messageId;
+  if (headerRelevant && left.headerMessageId !== right.headerMessageId) {
+    return false;
+  }
+
+  const ownerRelevant = left.activityOwnerMessageId === messageId || right.activityOwnerMessageId === messageId;
+  if (ownerRelevant && left.activityOwnerMessageId !== right.activityOwnerMessageId) {
+    return false;
+  }
+
+  if (!areRelevantActivityPartsEqual(left.activityParts, right.activityParts, messageId)) {
+    return false;
+  }
+
+  if (!areRelevantActivitySegmentsEqual(left.activityGroupSegments, right.activityGroupSegments, messageId)) {
+    return false;
+  }
+
+  const segmentsRelevant = hasRelevantActivitySegments(left.activityGroupSegments, messageId)
+    || hasRelevantActivitySegments(right.activityGroupSegments, messageId);
+
+  if ((ownerRelevant || segmentsRelevant) && left.isGroupExpanded !== right.isGroupExpanded) {
+    return false;
+  }
+
+  if ((ownerRelevant || segmentsRelevant) && left.toggleGroup !== right.toggleGroup) {
+    return false;
+  }
+
+  if ((ownerRelevant || segmentsRelevant) && !areTurnDiffStatsEqual(left.diffStats, right.diffStats)) {
+    return false;
+  }
+
+  return true;
+};