sdk: Don't use fs.exists, create helper

Author: jahooma

common/src/project-file-tree.ts

@@ -4,7 +4,7 @@ import * as ignore from 'ignore'
 import { sortBy } from 'lodash'
 
 import { DEFAULT_IGNORED_PATHS } from './old-constants'
-import { isValidProjectRoot } from './util/file'
+import { fileExists, isValidProjectRoot } from './util/file'
 
 import type { CodebuffFileSystem } from './types/filesystem'
 import type { DirectoryNode, FileTreeNode } from './util/file'
@@ -167,7 +167,7 @@ export async function parseGitignore(params: {
   ]
 
   for (const ignoreFilePath of ignoreFiles) {
-    if (!(await fs.exists(ignoreFilePath))) continue
+    if (!(await fileExists({ filePath: ignoreFilePath, fs }))) continue
 
     const ignoreContent = await fs.readFile(ignoreFilePath, 'utf8')
     const lines = ignoreContent.split('\n')

common/src/types/filesystem.ts

@@ -6,5 +6,5 @@ import type fs from 'fs'
  */
 export type CodebuffFileSystem = Pick<
   typeof fs.promises,
-  'exists' | 'mkdir' | 'readdir' | 'readFile' | 'stat' | 'writeFile'
+  'mkdir' | 'readdir' | 'readFile' | 'stat' | 'writeFile'
 >

common/src/util/file.ts

@@ -248,13 +248,31 @@ export const ensureEndsWithNewline = (
   return contents + '\n'
 }
 
+/**
+ * Node-compatible file existence check.
+ * Uses fs.stat instead of Bun-specific fs.exists.
+ */
+export async function fileExists(params: {
+  filePath: string
+  fs: CodebuffFileSystem
+}): Promise<boolean> {
+  const { filePath, fs } = params
+
+  try {
+    await fs.stat(filePath)
+    return true
+  } catch {
+    return false
+  }
+}
+
 export const ensureDirectoryExists = async (params: {
   baseDir: string
   fs: CodebuffFileSystem
 }) => {
   const { baseDir, fs } = params
 
-  if (!(await fs.exists(baseDir))) {
+  if (!(await fileExists({ filePath: baseDir, fs }))) {
     await fs.mkdir(baseDir, { recursive: true })
   }
 }

evals/scaffolding.ts

@@ -44,17 +44,7 @@ function readMockFile(projectRoot: string, filePath: string): string | null {
 
 let toolCalls: ClientToolCall[] = []
 let toolResults: ToolMessage[] = []
-const defaultFs: CodebuffFileSystem = {
-  ...(fs.promises as unknown as CodebuffFileSystem),
-  exists: async (pathLike) => {
-    try {
-      await fs.promises.access(pathLike as fs.PathLike)
-      return true
-    } catch {
-      return false
-    }
-  },
-}
+const defaultFs: CodebuffFileSystem = fs.promises as unknown as CodebuffFileSystem
 let projectRootForMocks: string | undefined
 
 export function createFileReadingMock(projectRoot: string) {

sdk/src/tools/change-file.ts

@@ -3,6 +3,8 @@ import path from 'path'
 import { applyPatch } from 'diff'
 import z from 'zod/v4'
 
+import { fileExists } from '@codebuff/common/util/file'
+
 import type { CodebuffToolOutput } from '@codebuff/common/tools/list'
 import type { CodebuffFileSystem } from '@codebuff/common/types/filesystem'
 
@@ -96,8 +98,8 @@ async function applyChanges(params: {
     const { path: filePath, content, type } = change
     try {
       const fullPath = path.join(projectRoot, filePath)
-      const fileExists = await fs.exists(fullPath)
-      if (!fileExists) {
+      const exists = await fileExists({ filePath: fullPath, fs })
+      if (!exists) {
         const dirPath = path.dirname(fullPath)
         await fs.mkdir(dirPath, { recursive: true })
       }
@@ -114,7 +116,7 @@ async function applyChanges(params: {
         await fs.writeFile(fullPath, newContent)
       }
 
-      if (fileExists) {
+      if (exists) {
         modified.push(filePath)
       } else {
         created.push(filePath)