fix(core): fix three JIT context bugs in read_file, read_many_files, and memoryDiscovery (#22679)

packages/core/src/utils/memoryDiscovery.test.ts

@@ -1155,6 +1155,60 @@ included directory memory
       // Ensure outer memory is NOT loaded
       expect(result.files.find((f) => f.path === outerMemory)).toBeUndefined();
     });
+
+    it('should resolve file target to its parent directory for traversal', async () => {
+      const rootDir = await createEmptyDir(
+        path.join(testRootDir, 'jit_file_resolve'),
+      );
+      const subDir = await createEmptyDir(path.join(rootDir, 'src'));
+
+      // Create the target file so fs.stat can identify it as a file
+      const targetFile = await createTestFile(
+        path.join(subDir, 'app.ts'),
+        'const x = 1;',
+      );
+
+      const subDirMemory = await createTestFile(
+        path.join(subDir, DEFAULT_CONTEXT_FILENAME),
+        'Src context rules',
+      );
+
+      const result = await loadJitSubdirectoryMemory(
+        targetFile,
+        [rootDir],
+        new Set(),
+      );
+
+      // Should find the GEMINI.md in the same directory as the file
+      expect(result.files).toHaveLength(1);
+      expect(result.files[0].path).toBe(subDirMemory);
+      expect(result.files[0].content).toBe('Src context rules');
+    });
+
+    it('should handle non-existent file target by using parent directory', async () => {
+      const rootDir = await createEmptyDir(
+        path.join(testRootDir, 'jit_nonexistent'),
+      );
+      const subDir = await createEmptyDir(path.join(rootDir, 'src'));
+
+      // Target file does NOT exist (e.g. write_file creating a new file)
+      const targetFile = path.join(subDir, 'new-file.ts');
+
+      const subDirMemory = await createTestFile(
+        path.join(subDir, DEFAULT_CONTEXT_FILENAME),
+        'Rules for new files',
+      );
+
+      const result = await loadJitSubdirectoryMemory(
+        targetFile,
+        [rootDir],
+        new Set(),
+      );
+
+      expect(result.files).toHaveLength(1);
+      expect(result.files[0].path).toBe(subDirMemory);
+      expect(result.files[0].content).toBe('Rules for new files');
+    });
   });
 
   it('refreshServerHierarchicalMemory should refresh memory and update config', async () => {

packages/core/src/utils/memoryDiscovery.ts

@@ -767,8 +767,24 @@ export async function loadJitSubdirectoryMemory(
     `(Trusted root: ${bestRoot})`,
   );
 
-  // Traverse from target up to the trusted root
-  const potentialPaths = await findUpwardGeminiFiles(resolvedTarget, bestRoot);
+  // Resolve the target to a directory before traversing upward.
+  // When the target is a file (e.g. /app/src/file.ts), start from its
+  // parent directory to avoid a wasted fs.access check on a nonsensical
+  // path like /app/src/file.ts/GEMINI.md.
+  let startDir = resolvedTarget;
+  try {
+    const stat = await fs.stat(resolvedTarget);
+    if (stat.isFile()) {
+      startDir = normalizePath(path.dirname(resolvedTarget));
+    }
+  } catch {
+    // If stat fails (e.g. file doesn't exist yet for write_file),
+    // assume it's a file path and use its parent directory.
+    startDir = normalizePath(path.dirname(resolvedTarget));
+  }
+
+  // Traverse from the resolved directory up to the trusted root
+  const potentialPaths = await findUpwardGeminiFiles(startDir, bestRoot);
 
   if (potentialPaths.length === 0) {
     return { files: [], fileIdentities: [] };