From 76f7b1bffd578e7c6ceca569d52b0fba9da81580 Mon Sep 17 00:00:00 2001
From: Spencer <spencertang@google.com>
Date: Tue, 7 Apr 2026 21:16:38 +0000
Subject: [PATCH] fix(cli): bound memory growth in high-volume components

---
 packages/cli/src/ui/components/AnsiOutput.tsx |  5 ++--
 .../messages/SubagentProgressDisplay.tsx      |  8 +++----
 .../src/ui/components/shared/text-buffer.ts   | 24 ++++++++++++++++++-
 3 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/packages/cli/src/ui/components/AnsiOutput.tsx b/packages/cli/src/ui/components/AnsiOutput.tsx
index 617740d4ad..77af60e519 100644
--- a/packages/cli/src/ui/components/AnsiOutput.tsx
+++ b/packages/cli/src/ui/components/AnsiOutput.tsx
@@ -35,16 +35,17 @@ export const AnsiOutputText: React.FC<AnsiOutputProps> = ({
       ? Math.min(availableHeightLimit, maxLines)
       : (availableHeightLimit ?? maxLines ?? DEFAULT_HEIGHT);
 
+  const MAXIMUM_ANSI_LINES_RENDERED = 1000;
   const lastLines = Array.isArray(data)
     ? disableTruncation
-      ? data
+      ? data.slice(-MAXIMUM_ANSI_LINES_RENDERED)
       : numLinesRetained === 0
         ? []
         : data.slice(-numLinesRetained)
     : [];
   return (
     <Box flexDirection="column" width={width} flexShrink={0} overflow="hidden">
-      {(lastLines as AnsiLine[]).map((line: AnsiLine, lineIndex: number) => (
+      {lastLines.map((line: AnsiLine, lineIndex: number) => (
         <Box key={lineIndex} height={1} overflow="hidden">
           <AnsiLineText line={line} />
         </Box>
diff --git a/packages/cli/src/ui/components/messages/SubagentProgressDisplay.tsx b/packages/cli/src/ui/components/messages/SubagentProgressDisplay.tsx
index 995c404d9d..8289e9ec71 100644
--- a/packages/cli/src/ui/components/messages/SubagentProgressDisplay.tsx
+++ b/packages/cli/src/ui/components/messages/SubagentProgressDisplay.tsx
@@ -86,8 +86,9 @@ export const SubagentProgressDisplay: React.FC<
         </Box>
       )}
       <Box flexDirection="column" marginLeft={0} gap={0}>
-        {(historyOverrides ?? progress.recentActivity).map(
-          (item: SubagentActivityItem) => {
+        {(historyOverrides ?? progress.recentActivity)
+          .slice(-100)
+          .map((item: SubagentActivityItem) => {
             if (item.type === 'thought') {
               const isCancellation = item.content === 'Request cancelled.';
               const icon = isCancellation ? 'ℹ ' : '💭';
@@ -155,8 +156,7 @@ export const SubagentProgressDisplay: React.FC<
               );
             }
             return null;
-          },
-        )}
+          })}
       </Box>
 
       {progress.result && (
diff --git a/packages/cli/src/ui/components/shared/text-buffer.ts b/packages/cli/src/ui/components/shared/text-buffer.ts
index d6b95d6016..56ab575c96 100644
--- a/packages/cli/src/ui/components/shared/text-buffer.ts
+++ b/packages/cli/src/ui/components/shared/text-buffer.ts
@@ -2779,7 +2779,29 @@ export function textBufferReducer(
   action: TextBufferAction,
   options: TextBufferOptions = {},
 ): TextBufferState {
-  const newState = textBufferReducerLogic(state, action, options);
+  let newState = textBufferReducerLogic(state, action, options);
+
+  const MAX_TEXT_BUFFER_LINES = 10000;
+  if (newState.lines.length > MAX_TEXT_BUFFER_LINES) {
+    const excess = newState.lines.length - MAX_TEXT_BUFFER_LINES;
+    const newLines = newState.lines.slice(excess);
+    const newCursorRow = Math.max(0, newState.cursorRow - excess);
+    let newExpandedPaste = newState.expandedPaste;
+    if (newExpandedPaste) {
+      const newStartLine = newExpandedPaste.startLine - excess;
+      if (newStartLine < 0) {
+        newExpandedPaste = null;
+      } else {
+        newExpandedPaste = { ...newExpandedPaste, startLine: newStartLine };
+      }
+    }
+    newState = {
+      ...newState,
+      lines: newLines,
+      cursorRow: newCursorRow,
+      expandedPaste: newExpandedPaste,
+    };
+  }
 
   const newTransformedLines =
     newState.lines !== state.lines