🤖 Live compaction (#309)

Fixes #244

## Summary

Replaced the `compact_summary` tool with direct text streaming for
conversation compaction. The model now streams the summary directly
instead of using a tool call to return it.

## Changes

- **Removed** `compact_summary` tool definition and service
implementation
- **Updated** `StreamingMessageAggregator` to extract compaction summary
from text parts
- **Updated** `WorkspaceStore` to handle compaction on stream-end
instead of tool completion
- **Removed** toolPolicy requirement forcing `compact_summary` tool
usage
- **Updated** tests and mock scenarios to reflect new flow

## Benefits

1. **Live feedback**: Users can now see the compaction summary as it
streams in real-time
2. **Context efficiency**: Eliminates duplicate text (no tool call +
assistant message)
3. **Simpler protocol**: Fewer moving parts, less code to maintain

## Testing

- ✅ Unit tests pass (`src/utils/messages/compactionOptions.test.ts`)
- ✅ Type checking passes
- ✅ All existing tests pass (573 tests)

_Generated with `cmux`_

Author: ammar-agent

.gitignore

@@ -90,6 +90,11 @@ CODE_CHANGES.md
 README_COMPACT_HERE.md
 artifacts/
 tests/e2e/tmp/
+
+# Test temporary directories
+src/test-temp-*/
+tests/**/test-temp-*/
+
 runs/
 
 # Python

src/components/AIView.tsx

@@ -345,6 +345,8 @@ const AIViewInner: React.FC<AIViewProps> = ({
     chatInputAPI,
     jumpToBottom,
     handleOpenTerminal,
+    aggregator,
+    setEditingMessage,
   });
 
   // Clear editing state if the message being edited no longer exists
@@ -523,7 +525,11 @@ const AIViewInner: React.FC<AIViewProps> = ({
                       ? `${getModelName(currentModel)} streaming...`
                       : "streaming..."
                 }
-                cancelText={`hit ${formatKeybind(KEYBINDS.INTERRUPT_STREAM)} to cancel`}
+                cancelText={
+                  isCompacting
+                    ? `${formatKeybind(KEYBINDS.INTERRUPT_STREAM)} cancel | ${formatKeybind(KEYBINDS.ACCEPT_EARLY_COMPACTION)} accept early`
+                    : `hit ${formatKeybind(KEYBINDS.INTERRUPT_STREAM)} to cancel`
+                }
                 tokenCount={
                   activeStreamMessageId
                     ? aggregator.getStreamingTokenCount(activeStreamMessageId)

src/components/ChatInput.tsx

@@ -120,6 +120,7 @@ const ModelDisplayWrapper = styled.div`
 
 export interface ChatInputAPI {
   focus: () => void;
+  restoreText: (text: string) => void;
 }
 
 export interface ChatInputProps {
@@ -430,12 +431,24 @@ export const ChatInput: React.FC<ChatInputProps> = ({
     });
   }, []);
 
+  // Method to restore text to input (used by compaction cancel)
+  const restoreText = useCallback(
+    (text: string) => {
+      setInput(text);
+      focusMessageInput();
+    },
+    [focusMessageInput]
+  );
+
   // Provide API to parent via callback
   useEffect(() => {
     if (onReady) {
-      onReady({ focus: focusMessageInput });
+      onReady({
+        focus: focusMessageInput,
+        restoreText,
+      });
     }
-  }, [onReady, focusMessageInput]);
+  }, [onReady, focusMessageInput, restoreText]);
 
   useEffect(() => {
     const handleGlobalKeyDown = (event: KeyboardEvent) => {
@@ -948,7 +961,7 @@ export const ChatInput: React.FC<ChatInputProps> = ({
       return `Edit your message... (${formatKeybind(KEYBINDS.CANCEL_EDIT)} to cancel, ${formatKeybind(KEYBINDS.SEND_MESSAGE)} to send)`;
     }
     if (isCompacting) {
-      return `Compacting... (${formatKeybind(KEYBINDS.INTERRUPT_STREAM)} to cancel)`;
+      return `Compacting... (${formatKeybind(KEYBINDS.INTERRUPT_STREAM)} cancel | ${formatKeybind(KEYBINDS.ACCEPT_EARLY_COMPACTION)} accept early)`;
     }
 
     // Build hints for normal input

src/components/Messages/AssistantMessage.tsx

@@ -8,6 +8,8 @@ import { MessageWindow } from "./MessageWindow";
 import { useStartHere } from "@/hooks/useStartHere";
 import { COMPACTED_EMOJI } from "@/constants/ui";
 import { ModelDisplay } from "./ModelDisplay";
+import { CompactingMessageContent } from "./CompactingMessageContent";
+import { CompactionBackground } from "./CompactionBackground";
 
 const RawContent = styled.pre`
   font-family: var(--font-monospace);
@@ -49,13 +51,15 @@ interface AssistantMessageProps {
   message: DisplayedMessage & { type: "assistant" };
   className?: string;
   workspaceId?: string;
+  isCompacting?: boolean;
   clipboardWriteText?: (data: string) => Promise<void>;
 }
 
 export const AssistantMessage: React.FC<AssistantMessageProps> = ({
   message,
   className,
   workspaceId,
+  isCompacting = false,
   clipboardWriteText = (data: string) => navigator.clipboard.writeText(data),
 }) => {
   const [showRaw, setShowRaw] = useState(false);
@@ -64,6 +68,7 @@ export const AssistantMessage: React.FC<AssistantMessageProps> = ({
   const content = message.content;
   const isStreaming = message.isStreaming;
   const isCompacted = message.isCompacted;
+  const isStreamingCompaction = isStreaming && isCompacting;
 
   // Use Start Here hook for final assistant messages
   const {
@@ -120,7 +125,14 @@ export const AssistantMessage: React.FC<AssistantMessageProps> = ({
 
     // Streaming text gets typewriter effect
     if (isStreaming) {
-      return <TypewriterMarkdown deltas={[content]} isComplete={false} />;
+      const contentElement = <TypewriterMarkdown deltas={[content]} isComplete={false} />;
+
+      // Wrap streaming compaction in special container
+      if (isStreamingCompaction) {
+        return <CompactingMessageContent>{contentElement}</CompactingMessageContent>;
+      }
+
+      return contentElement;
     }
 
     // Completed text renders as static content
@@ -154,6 +166,7 @@ export const AssistantMessage: React.FC<AssistantMessageProps> = ({
         message={message}
         buttons={buttons}
         className={className}
+        backgroundEffect={isStreamingCompaction ? <CompactionBackground /> : undefined}
       >
         {renderContent()}
       </MessageWindow>

src/components/Messages/CompactingMessageContent.tsx

@@ -0,0 +1,43 @@
+import React from "react";
+import styled from "@emotion/styled";
+
+/**
+ * Wrapper for compaction streaming content
+ * Provides max-height constraint with fade effect to imply content above
+ * No scrolling - content stays anchored to bottom, older content fades at top
+ */
+
+const Container = styled.div`
+  max-height: 300px;
+  overflow: hidden;
+  position: relative;
+  display: flex;
+  flex-direction: column;
+  justify-content: flex-end; /* Anchor content to bottom */
+
+  /* Fade effect: content fades progressively from top to bottom */
+  mask-image: linear-gradient(
+    to bottom,
+    transparent 0%,
+    rgba(0, 0, 0, 0.3) 5%,
+    rgba(0, 0, 0, 0.6) 10%,
+    rgba(0, 0, 0, 0.85) 15%,
+    black 20%
+  );
+  -webkit-mask-image: linear-gradient(
+    to bottom,
+    transparent 0%,
+    rgba(0, 0, 0, 0.3) 5%,
+    rgba(0, 0, 0, 0.6) 10%,
+    rgba(0, 0, 0, 0.85) 15%,
+    black 20%
+  );
+`;
+
+interface CompactingMessageContentProps {
+  children: React.ReactNode;
+}
+
+export const CompactingMessageContent: React.FC<CompactingMessageContentProps> = ({ children }) => {
+  return <Container>{children}</Container>;
+};

src/components/Messages/CompactionBackground.tsx

@@ -0,0 +1,85 @@
+import React from "react";
+import styled from "@emotion/styled";
+import { keyframes } from "@emotion/react";
+
+/**
+ * Animated background for compaction streaming
+ * Shimmer effect with moving gradient and particles for dynamic appearance
+ */
+
+const shimmer = keyframes`
+  0% {
+    background-position: -1000px 0;
+  }
+  100% {
+    background-position: 1000px 0;
+  }
+`;
+
+const gradientMove = keyframes`
+  0% {
+    background-position: 0% 50%;
+  }
+  50% {
+    background-position: 100% 50%;
+  }
+  100% {
+    background-position: 0% 50%;
+  }
+`;
+
+const Container = styled.div`
+  position: absolute;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+  overflow: hidden;
+  pointer-events: none;
+  border-radius: 6px;
+`;
+
+const AnimatedGradient = styled.div`
+  position: absolute;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+  background: linear-gradient(
+    -45deg,
+    var(--color-plan-mode-alpha),
+    color-mix(in srgb, var(--color-plan-mode) 30%, transparent),
+    var(--color-plan-mode-alpha),
+    color-mix(in srgb, var(--color-plan-mode) 25%, transparent)
+  );
+  background-size: 400% 400%;
+  animation: ${gradientMove} 8s ease infinite;
+  opacity: 0.4;
+`;
+
+const ShimmerLayer = styled.div`
+  position: absolute;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+  background: linear-gradient(
+    90deg,
+    transparent 0%,
+    transparent 40%,
+    var(--color-plan-mode-alpha) 50%,
+    transparent 60%,
+    transparent 100%
+  );
+  background-size: 1000px 100%;
+  animation: ${shimmer} 3s infinite linear;
+`;
+
+export const CompactionBackground: React.FC = () => {
+  return (
+    <Container>
+      <AnimatedGradient />
+      <ShimmerLayer />
+    </Container>
+  );
+};

src/components/Messages/MessageRenderer.tsx

@@ -31,7 +31,12 @@ export const MessageRenderer = React.memo<MessageRendererProps>(
         );
       case "assistant":
         return (
-          <AssistantMessage message={message} className={className} workspaceId={workspaceId} />
+          <AssistantMessage
+            message={message}
+            className={className}
+            workspaceId={workspaceId}
+            isCompacting={isCompacting}
+          />
         );
       case "tool":
         return <ToolMessage message={message} className={className} workspaceId={workspaceId} />;

src/components/Messages/MessageWindow.tsx

@@ -7,6 +7,7 @@ import { formatTimestamp } from "@/utils/ui/dateTime";
 import { TooltipWrapper, Tooltip } from "../Tooltip";
 
 const MessageBlock = styled.div<{ borderColor: string; backgroundColor?: string }>`
+  position: relative;
   margin-bottom: 15px;
   margin-top: 15px;
   background: ${(props) => props.backgroundColor ?? "#1e1e1e"};
@@ -16,6 +17,8 @@ const MessageBlock = styled.div<{ borderColor: string; backgroundColor?: string
 `;
 
 const MessageHeader = styled.div`
+  position: relative;
+  z-index: 1;
   padding: 8px 12px;
   background: rgba(255, 255, 255, 0.05);
   border-bottom: 1px solid rgba(255, 255, 255, 0.1);
@@ -51,6 +54,8 @@ const ButtonGroup = styled.div`
 `;
 
 const MessageContent = styled.div`
+  position: relative;
+  z-index: 1;
   padding: 12px;
 `;
 
@@ -85,6 +90,7 @@ interface MessageWindowProps {
   children: ReactNode;
   className?: string;
   rightLabel?: ReactNode;
+  backgroundEffect?: ReactNode; // Optional background effect (e.g., animation)
 }
 
 export const MessageWindow: React.FC<MessageWindowProps> = ({
@@ -96,6 +102,7 @@ export const MessageWindow: React.FC<MessageWindowProps> = ({
   children,
   className,
   rightLabel,
+  backgroundEffect,
 }) => {
   const [showJson, setShowJson] = useState(false);
 
@@ -111,6 +118,7 @@ export const MessageWindow: React.FC<MessageWindowProps> = ({
 
   return (
     <MessageBlock borderColor={borderColor} backgroundColor={backgroundColor} className={className}>
+      {backgroundEffect}
       <MessageHeader>
         <LeftSection>
           <MessageTypeLabel>{label}</MessageTypeLabel>

src/components/Messages/UserMessage.tsx

@@ -102,7 +102,7 @@ export const UserMessage: React.FC<UserMessageProps> = ({
             onClick: handleEdit,
             disabled: isCompacting,
             tooltip: isCompacting
-              ? `Cannot edit while compacting (press ${formatKeybind(KEYBINDS.INTERRUPT_STREAM)} to cancel)`
+              ? `Cannot edit while compacting (${formatKeybind(KEYBINDS.INTERRUPT_STREAM)} to cancel)`
               : undefined,
           },
         ]

src/constants/storage.ts

@@ -47,6 +47,14 @@ export function getLastThinkingByModelKey(modelName: string): string {
   return `lastThinkingByModel:${modelName}`;
 }
 
+/**
+ * Get storage key for cancelled compaction tracking.
+ * Stores compaction-request user message ID to verify freshness across reloads.
+ */
+export function getCancelledCompactionKey(workspaceId: string): string {
+  return `workspace:${workspaceId}:cancelled-compaction`;
+}
+
 /**
  * Get the localStorage key for the UI mode for a workspace
  * Format: "mode:{workspaceId}"