fix(core): shrink file diff session records

packages/cli/src/acp-integration/session/emitters/ToolCallEmitter.test.ts

@@ -233,6 +233,41 @@ describe('ToolCallEmitter', () => {
       );
     });
 
+    it('should not replay truncated session previews as full diffs', async () => {
+      await emitter.emitResult({
+        toolName: 'edit_file',
+        callId: 'call-edit',
+        success: true,
+        message: [],
+        resultDisplay: {
+          fileName: '/test/file.ts',
+          originalContent: 'old preview',
+          newContent: 'new preview',
+          truncatedForSession: true,
+          fileDiffLength: 200000,
+          fileDiffTruncated: true,
+        },
+      });
+
+      expect(sendUpdateSpy).toHaveBeenCalledWith(
+        expect.objectContaining({
+          sessionUpdate: 'tool_call_update',
+          toolCallId: 'call-edit',
+          status: 'completed',
+          content: [
+            {
+              type: 'content',
+              content: {
+                type: 'text',
+                text: 'Full diff omitted from saved session history for /test/file.ts. Original fileDiff length: 200000 chars.',
+              },
+            },
+          ],
+          _meta: { toolName: 'edit_file' },
+        }),
+      );
+    });
+
     it('should transform message parts to content', async () => {
       await emitter.emitResult({
         toolName: 'test_tool',

packages/cli/src/acp-integration/session/emitters/ToolCallEmitter.ts

@@ -20,6 +20,7 @@ import type {
 } from '@agentclientprotocol/sdk';
 import type { Part } from '@google/genai';
 import { ToolNames, Kind } from '@qwen-code/qwen-code-core';
+import { buildTruncatedDiffPreviewText } from '../../../utils/truncatedDiffPreview.js';
 
 /**
  * Unified tool call event emitter.
@@ -273,6 +274,16 @@ export class ToolCallEmitter extends BaseEmitter {
 
     // Check if this is a diff display (edit tool result)
     if ('fileName' in obj && 'newContent' in obj) {
+      if (obj['truncatedForSession'] === true) {
+        return {
+          type: 'content',
+          content: {
+            type: 'text',
+            text: buildTruncatedDiffPreviewText(obj),
+          },
+        };
+      }
+
       return {
         type: 'diff',
         path: obj['fileName'] as string,

packages/cli/src/ui/components/messages/ToolMessage.test.tsx

@@ -274,6 +274,27 @@ describe('<ToolMessage />', () => {
     expect(lastFrame()).toMatch(/MockDiff:--- a\/file\.txt/);
   });
 
+  it('renders a saved-session preview notice for truncated diff results', () => {
+    const diffResult = {
+      fileDiff: '--- file.txt\n+++ file.txt\n@@ -1 +1 @@\n-omitted\n+preview',
+      fileName: 'file.txt',
+      originalContent: 'old preview',
+      newContent: 'new preview',
+      truncatedForSession: true,
+      fileDiffLength: 123456,
+      fileDiffTruncated: true,
+    };
+    const { lastFrame } = renderWithContext(
+      <ToolMessage {...baseProps} resultDisplay={diffResult} />,
+      StreamingState.Idle,
+    );
+
+    expect(lastFrame()).toContain(
+      'Saved session preview only; full diff omitted from JSONL (123456 chars).',
+    );
+    expect(lastFrame()).toContain('MockDiff:--- file.txt');
+  });
+
   it('renders emphasis correctly', () => {
     const { lastFrame: highEmphasisFrame } = renderWithContext(
       <ToolMessage {...baseProps} emphasis="high" />,

packages/cli/src/ui/components/messages/ToolMessage.tsx

@@ -22,6 +22,7 @@ import type {
   AnsiOutputDisplay,
   Config,
   McpToolProgressData,
+  FileDiff,
 } from '@qwen-code/qwen-code-core';
 import { AgentExecutionDisplay } from '../subagents/index.js';
 import { ToolConfirmationMessage } from './ToolConfirmationMessage.js';
@@ -49,6 +50,14 @@ const DEFAULT_SHELL_OUTPUT_MAX_LINES = 5;
 // outputs that will get truncated further MaxSizedBox anyway.
 const MAXIMUM_RESULT_DISPLAY_CHARACTERS = 1000000;
 export type TextEmphasis = 'high' | 'medium' | 'low';
+type DiffResultDisplay = Pick<
+  FileDiff,
+  | 'fileDiff'
+  | 'fileName'
+  | 'truncatedForSession'
+  | 'fileDiffLength'
+  | 'fileDiffTruncated'
+>;
 
 function sliceTextForMaxHeight(
   text: string,
@@ -175,7 +184,7 @@ const useResultDisplayRenderer = (
     ) {
       return {
         type: 'diff',
-        data: resultDisplay as { fileDiff: string; fileName: string },
+        data: resultDisplay as DiffResultDisplay,
       };
     }
 
@@ -378,19 +387,38 @@ const StringResultRenderer: React.FC<{
  * Component to render diff results
  */
 const DiffResultRenderer: React.FC<{
-  data: { fileDiff: string; fileName: string };
+  data: DiffResultDisplay;
   availableHeight?: number;
   childWidth: number;
   settings?: LoadedSettings;
-}> = ({ data, availableHeight, childWidth, settings }) => (
-  <DiffRenderer
-    diffContent={data.fileDiff}
-    filename={data.fileName}
-    availableTerminalHeight={availableHeight}
-    contentWidth={childWidth}
-    settings={settings}
-  />
-);
+}> = ({ data, availableHeight, childWidth, settings }) => {
+  const diffHeight =
+    data.truncatedForSession && availableHeight !== undefined
+      ? Math.max(1, availableHeight - 1)
+      : availableHeight;
+
+  return (
+    <Box flexDirection="column">
+      {data.truncatedForSession && (
+        <Text color={theme.status.warning} wrap="wrap">
+          {data.fileDiffTruncated
+            ? 'Saved session preview only; full diff omitted from JSONL'
+            : 'Saved session preview only; full file contents truncated in JSONL'}
+          {data.fileDiffTruncated && typeof data.fileDiffLength === 'number'
+            ? ` (${data.fileDiffLength} chars).`
+            : '.'}
+        </Text>
+      )}
+      <DiffRenderer
+        diffContent={data.fileDiff}
+        filename={data.fileName}
+        availableTerminalHeight={diffHeight}
+        contentWidth={childWidth}
+        settings={settings}
+      />
+    </Box>
+  );
+};
 
 export interface ToolMessageProps extends IndividualToolCallDisplay {
   availableTerminalHeight?: number;

packages/cli/src/ui/utils/export/collect.test.ts

@@ -0,0 +1,89 @@
+/**
+ * @license
+ * Copyright 2025 Qwen Team
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, expect, it, vi } from 'vitest';
+import type { ChatRecord, Config } from '@qwen-code/qwen-code-core';
+import { collectSessionData } from './collect.js';
+
+describe('collectSessionData', () => {
+  const config = {
+    getToolRegistry: vi.fn().mockReturnValue({
+      getTool: vi.fn().mockReturnValue(null),
+    }),
+  } as unknown as Config;
+
+  it('skips line-count fallback for truncated saved-session previews', async () => {
+    const records: ChatRecord[] = [
+      {
+        uuid: 'assistant-1',
+        parentUuid: null,
+        sessionId: 'session-1',
+        timestamp: '2025-01-01T00:00:00.000Z',
+        type: 'assistant',
+        cwd: '',
+        version: '1.0.0',
+        message: {
+          role: 'model',
+          parts: [
+            {
+              functionCall: {
+                id: 'call-1',
+                name: 'edit_file',
+                args: { file_path: '/test/file.ts' },
+              },
+            },
+          ],
+        },
+      },
+      {
+        uuid: 'tool-1',
+        parentUuid: 'assistant-1',
+        sessionId: 'session-1',
+        timestamp: '2025-01-01T00:00:01.000Z',
+        type: 'tool_result',
+        cwd: '',
+        version: '1.0.0',
+        message: {
+          role: 'user',
+          parts: [
+            {
+              functionResponse: {
+                id: 'call-1',
+                name: 'edit_file',
+                response: { output: 'ok' },
+              },
+            },
+          ],
+        },
+        toolCallResult: {
+          callId: 'call-1',
+          resultDisplay: {
+            fileName: 'file.ts',
+            fileDiff:
+              '--- file.ts\n+++ file.ts\n@@ -1,2 +1,2 @@\n-old\n-preview\n+new\n+preview',
+            originalContent: 'old\npreview',
+            newContent: 'new\npreview',
+            truncatedForSession: true,
+          },
+        },
+      },
+    ];
+
+    const data = await collectSessionData(
+      {
+        sessionId: 'session-1',
+        startTime: '2025-01-01T00:00:00.000Z',
+        messages: records,
+      },
+      config,
+    );
+
+    expect(data.metadata?.filesWritten).toBe(1);
+    expect(data.metadata?.uniqueFiles).toEqual(['/test/file.ts']);
+    expect(data.metadata?.linesAdded).toBe(0);
+    expect(data.metadata?.linesRemoved).toBe(0);
+  });
+});

packages/cli/src/ui/utils/export/collect.ts

@@ -171,6 +171,7 @@ function calculateFileStats(records: ChatRecord[]): FileOperationStats {
         originalContent?: string | null;
         newContent?: string;
         diffStat?: { model_added_lines?: number; model_removed_lines?: number };
+        truncatedForSession?: boolean;
       };
 
       // Determine operation type based on content fields
@@ -197,7 +198,7 @@ function calculateFileStats(records: ChatRecord[]): FileOperationStats {
           // Use diffStat if available for accurate counts
           stats.linesAdded += display.diffStat.model_added_lines ?? 0;
           stats.linesRemoved += display.diffStat.model_removed_lines ?? 0;
-        } else {
+        } else if (!display.truncatedForSession) {
           // Fallback: count lines in content
           const oldText = String(display.originalContent ?? '');
           const newText = String(display.newContent ?? '');

packages/cli/src/ui/utils/export/normalize.test.ts

@@ -0,0 +1,72 @@
+/**
+ * @license
+ * Copyright 2025 Qwen Team
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, expect, it, vi } from 'vitest';
+import type { ChatRecord, Config } from '@qwen-code/qwen-code-core';
+import { normalizeSessionData } from './normalize.js';
+
+describe('normalizeSessionData', () => {
+  const config = {
+    getToolRegistry: vi.fn().mockReturnValue(undefined),
+  } as unknown as Config;
+
+  it('does not export truncated saved-session previews as full diffs', () => {
+    const record: ChatRecord = {
+      uuid: 'tool-1',
+      parentUuid: null,
+      sessionId: 'session-1',
+      timestamp: '2025-01-01T00:00:00.000Z',
+      type: 'tool_result',
+      cwd: '',
+      version: '1.0.0',
+      message: {
+        role: 'user',
+        parts: [
+          {
+            functionResponse: {
+              id: 'call-1',
+              name: 'edit_file',
+              response: { output: 'ok' },
+            },
+          },
+        ],
+      },
+      toolCallResult: {
+        callId: 'call-1',
+        resultDisplay: {
+          fileName: '/test/file.ts',
+          fileDiff:
+            '--- /test/file.ts\n+++ /test/file.ts\n@@ -1 +1 @@\n-omitted\n+preview',
+          originalContent: 'old preview',
+          newContent: 'new preview',
+          truncatedForSession: true,
+          fileDiffLength: 200000,
+          fileDiffTruncated: true,
+        },
+      },
+    };
+
+    const normalized = normalizeSessionData(
+      {
+        sessionId: 'session-1',
+        startTime: '2025-01-01T00:00:00.000Z',
+        messages: [],
+      },
+      [record],
+      config,
+    );
+
+    expect(normalized.messages[0].toolCall?.content).toEqual([
+      {
+        type: 'content',
+        content: {
+          type: 'text',
+          text: 'Full diff omitted from saved session history for /test/file.ts. Original fileDiff length: 200000 chars.',
+        },
+      },
+    ]);
+  });
+});

packages/cli/src/ui/utils/export/normalize.ts

@@ -7,6 +7,7 @@
 import type { Part } from '@google/genai';
 import { ToolNames } from '@qwen-code/qwen-code-core';
 import type { ChatRecord, Config, Kind } from '@qwen-code/qwen-code-core';
+import { buildTruncatedDiffPreviewText } from '../../../utils/truncatedDiffPreview.js';
 import type { ExportMessage, ExportSessionData } from './types.js';
 
 /**
@@ -283,6 +284,18 @@ function extractDiffContent(
 
   const display = resultDisplay as Record<string, unknown>;
   if ('fileName' in display && 'newContent' in display) {
+    if (display['truncatedForSession'] === true) {
+      return [
+        {
+          type: 'content',
+          content: {
+            type: 'text',
+            text: buildTruncatedDiffPreviewText(display),
+          },
+        },
+      ];
+    }
+
     return [
       {
         type: 'diff',