fix(core): made context files append instead of replace (#26950)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

packages/cli/src/config/config.ts

@@ -16,7 +16,8 @@ import { hooksCommand } from '../commands/hooks.js';
 import { gemmaCommand } from '../commands/gemma.js';
 import {
   setGeminiMdFilename as setServerGeminiMdFilename,
-  getCurrentGeminiMdFilename,
+  resetGeminiMdFilename,
+  DEFAULT_CONTEXT_FILENAME,
   ApprovalMode,
   DEFAULT_GEMINI_EMBEDDING_MODEL,
   DEFAULT_FILE_FILTERING_OPTIONS,
@@ -619,7 +620,7 @@ export async function loadCliConfig(
     setServerGeminiMdFilename(settings.context.fileName);
   } else {
     // Reset to default if not provided in settings.
-    setServerGeminiMdFilename(getCurrentGeminiMdFilename());
+    resetGeminiMdFilename(DEFAULT_CONTEXT_FILENAME);
   }
 
   const fileService = new FileDiscoveryService(cwd);

packages/core/src/tools/memoryTool.test.ts

@@ -16,6 +16,7 @@ import {
 import {
   MemoryTool,
   setGeminiMdFilename,
+  resetGeminiMdFilename,
   getCurrentGeminiMdFilename,
   getAllGeminiMdFilenames,
   DEFAULT_CONTEXT_FILENAME,
@@ -45,14 +46,18 @@ vi.mock('node:fs/promises', async (importOriginal) => {
   };
 });
 
-vi.mock('fs', () => ({
-  mkdirSync: vi.fn(),
-  createWriteStream: vi.fn(() => ({
-    on: vi.fn(),
-    write: vi.fn(),
-    end: vi.fn(),
-  })),
-}));
+vi.mock('fs', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('fs')>();
+  return {
+    ...actual,
+    mkdirSync: vi.fn(),
+    createWriteStream: vi.fn(() => ({
+      on: vi.fn(),
+      write: vi.fn(),
+      end: vi.fn(),
+    })),
+  };
+});
 
 vi.mock('os');
 
@@ -77,30 +82,65 @@ describe('MemoryTool', () => {
 
   afterEach(() => {
     vi.restoreAllMocks();
-    setGeminiMdFilename(DEFAULT_CONTEXT_FILENAME);
+    resetGeminiMdFilename(DEFAULT_CONTEXT_FILENAME);
   });
 
   describe('setGeminiMdFilename', () => {
-    it('should update currentGeminiMdFilename when a valid new name is provided', () => {
+    it('should append to currentGeminiMdFilename when a valid new name is provided', () => {
       const newName = 'CUSTOM_CONTEXT.md';
       setGeminiMdFilename(newName);
-      expect(getCurrentGeminiMdFilename()).toBe(newName);
+      expect(getAllGeminiMdFilenames()).toEqual([
+        newName,
+        DEFAULT_CONTEXT_FILENAME,
+      ]);
     });
 
     it('should not update currentGeminiMdFilename if the new name is empty or whitespace', () => {
-      const initialName = getCurrentGeminiMdFilename();
+      const initialNames = getAllGeminiMdFilenames();
       setGeminiMdFilename('  ');
-      expect(getCurrentGeminiMdFilename()).toBe(initialName);
+      expect(getAllGeminiMdFilenames()).toEqual(initialNames);
 
       setGeminiMdFilename('');
-      expect(getCurrentGeminiMdFilename()).toBe(initialName);
+      expect(getAllGeminiMdFilenames()).toEqual(initialNames);
     });
 
-    it('should handle an array of filenames', () => {
+    it('should handle adding an array of filenames', () => {
       const newNames = ['CUSTOM_CONTEXT.md', 'ANOTHER_CONTEXT.md'];
       setGeminiMdFilename(newNames);
-      expect(getCurrentGeminiMdFilename()).toBe('CUSTOM_CONTEXT.md');
-      expect(getAllGeminiMdFilenames()).toEqual(newNames);
+      expect(getAllGeminiMdFilenames()).toEqual([
+        ...newNames,
+        DEFAULT_CONTEXT_FILENAME,
+      ]);
+    });
+
+    it('should ensure uniqueness when adding names', () => {
+      setGeminiMdFilename(DEFAULT_CONTEXT_FILENAME);
+      expect(getAllGeminiMdFilenames()).toEqual([DEFAULT_CONTEXT_FILENAME]);
+
+      setGeminiMdFilename(['NEW.md', 'NEW.md']);
+      expect(getAllGeminiMdFilenames()).toEqual([
+        'NEW.md',
+        DEFAULT_CONTEXT_FILENAME,
+      ]);
+    });
+  });
+
+  describe('resetGeminiMdFilename', () => {
+    it('should replace all filenames with the provided one', () => {
+      setGeminiMdFilename('OTHER.md');
+      resetGeminiMdFilename('RESET.md');
+      expect(getAllGeminiMdFilenames()).toEqual(['RESET.md']);
+    });
+
+    it('should reset to default if no argument provided', () => {
+      resetGeminiMdFilename('OTHER.md');
+      resetGeminiMdFilename(DEFAULT_CONTEXT_FILENAME);
+      expect(getAllGeminiMdFilenames()).toEqual([DEFAULT_CONTEXT_FILENAME]);
+    });
+
+    it('should handle array reset', () => {
+      resetGeminiMdFilename(['A.md', 'B.md']);
+      expect(getAllGeminiMdFilenames()).toEqual(['A.md', 'B.md']);
     });
   });
 

packages/core/src/tools/memoryTool.ts

@@ -18,7 +18,7 @@ import * as path from 'node:path';
 import { Storage } from '../config/storage.js';
 import * as Diff from 'diff';
 import { DEFAULT_DIFF_OPTIONS } from './diffOptions.js';
-import { tildeifyPath } from '../utils/paths.js';
+import { resolveToRealPath, tildeifyPath } from '../utils/paths.js';
 import type {
   ModifiableDeclarativeTool,
   ModifyContext,
@@ -33,17 +33,65 @@ export const DEFAULT_CONTEXT_FILENAME = 'GEMINI.md';
 export const MEMORY_SECTION_HEADER = '## Gemini Added Memories';
 export const PROJECT_MEMORY_INDEX_FILENAME = 'MEMORY.md';
 
-// This variable will hold the currently configured filename for GEMINI.md context files.
-// It defaults to DEFAULT_CONTEXT_FILENAME but can be overridden by setGeminiMdFilename.
+// This variable will hold the currently configured filenames for GEMINI.md context files.
+// It defaults to DEFAULT_CONTEXT_FILENAME but can be extended by setGeminiMdFilename.
 let currentGeminiMdFilename: string | string[] = DEFAULT_CONTEXT_FILENAME;
 
+/**
+ * Adds one or more filenames to the current context filenames.
+ * Ensures uniqueness and maintains order.
+ */
 export function setGeminiMdFilename(newFilename: string | string[]): void {
-  if (Array.isArray(newFilename)) {
-    if (newFilename.length > 0) {
-      currentGeminiMdFilename = newFilename.map((name) => name.trim());
+  const filenames = Array.isArray(newFilename) ? newFilename : [newFilename];
+  const current = getAllGeminiMdFilenames();
+  const next = new Set<string>();
+
+  for (const filename of filenames) {
+    const trimmed = filename.trim();
+    if (trimmed !== '') {
+      const normalized = path.normalize(trimmed);
+      // Sanitize to prevent path traversal while allowing subdirectories
+      const validatedPath = resolveToRealPath(normalized);
+      if (validatedPath) {
+        next.add(normalized);
+      }
     }
-  } else if (newFilename && newFilename.trim() !== '') {
-    currentGeminiMdFilename = newFilename.trim();
+  }
+
+  for (const filename of current) {
+    next.add(filename);
+  }
+
+  const result = Array.from(next);
+  if (result.length > 1) {
+    currentGeminiMdFilename = result;
+  } else if (result.length === 1) {
+    currentGeminiMdFilename = result[0];
+  }
+}
+
+/**
+ * Resets the context filenames to the provided value, or the default if none provided.
+ * This replaces all current filenames.
+ */
+export function resetGeminiMdFilename(
+  filename: string | string[] = DEFAULT_CONTEXT_FILENAME,
+): void {
+  const filenames = Array.isArray(filename) ? filename : [filename];
+  const cleaned = Array.from(
+    new Set(
+      filenames
+        .map((f) => path.normalize(f.trim()))
+        .filter((f) => !!resolveToRealPath(f)),
+    ),
+  );
+
+  if (cleaned.length === 0) {
+    currentGeminiMdFilename = DEFAULT_CONTEXT_FILENAME;
+  } else if (cleaned.length === 1) {
+    currentGeminiMdFilename = cleaned[0];
+  } else {
+    currentGeminiMdFilename = cleaned;
   }
 }