fix: add isDirectory() pre-check to Write/Read/Edit to prevent EISDIR errors

packages/builtin-tools/src/tools/FileEditTool/FileEditTool.ts

@@ -178,14 +178,26 @@ export const FileEditTool = buildTool({
 
     const fs = getFsImplementation()
 
-    // Prevent OOM on multi-GB files.
+    // 预检：防止 OOM（超大文件）+ 防止编辑目录路径
+    // 目录路径预检避免 AI 模型传入目录时触发原始 EISDIR 错误，
+    // 确保模型拿到清晰、可操作的指引消息。
     try {
-      const { size } = await fs.stat(fullFilePath)
-      if (size > MAX_EDIT_FILE_SIZE) {
+      const fileStat = await fs.stat(fullFilePath)
+      // 预检：如果路径已是一个存在的目录，及时拒绝并给出指引
+      // 避免 AI 模型传入目录路径后 Edit 工具读取文件时抛 EISDIR。
+      if (fileStat.isDirectory()) {
         return {
           result: false,
           behavior: 'ask',
-          message: `File is too large to edit (${formatFileSize(size)}). Maximum editable file size is ${formatFileSize(MAX_EDIT_FILE_SIZE)}.`,
+          message: `Cannot edit '${file_path}': the specified path is an existing directory. Use Bash ls to list files in this directory, or specify a filename path to edit a specific file.`,
+          errorCode: 10,
+        }
+      }
+      if (fileStat.size > MAX_EDIT_FILE_SIZE) {
+        return {
+          result: false,
+          behavior: 'ask',
+          message: `File is too large to edit (${formatFileSize(fileStat.size)}). Maximum editable file size is ${formatFileSize(MAX_EDIT_FILE_SIZE)}.`,
           errorCode: 10,
         }
       }

packages/builtin-tools/src/tools/FileEditTool/prompt.ts

@@ -24,5 +24,6 @@ Usage:${getPreReadInstruction()}
 - ALWAYS prefer editing existing files in the codebase. NEVER write new files unless explicitly required.
 - Only use emojis if the user explicitly requests it. Avoid adding emojis to files unless asked.
 - The edit will FAIL if \`old_string\` is not unique in the file. Either provide a larger string with more surrounding context to make it unique or use \`replace_all\` to change every instance of \`old_string\`.${minimalUniquenessHint}
-- Use \`replace_all\` for replacing and renaming strings across the file. This parameter is useful if you want to rename a variable for instance.`
+- Use \`replace_all\` for replacing and renaming strings across the file. This parameter is useful if you want to rename a variable for instance.
+- The file_path must be a file path, not a directory path. If the path resolves to an existing directory, the tool will reject it. Use a path that points to an existing file.`
 }

packages/builtin-tools/src/tools/FileReadTool/FileReadTool.ts

@@ -464,6 +464,23 @@ export const FileReadTool = buildTool({
       return { result: true }
     }
 
+    // 预检：如果路径已是一个存在的目录，及时拒绝并给出指引
+    // 避免 AI 模型用 Read 工具读取目录路径时抛出原始 EISDIR 错误，
+    // 模型拿到错误后不知该用 ls 列目录，可能做出错误恢复决策。
+    try {
+      const fileStat = await getFsImplementation().stat(fullFilePath)
+      if (fileStat.isDirectory()) {
+        return {
+          result: false,
+          message: `Cannot read '${file_path}': the specified path is an existing directory. Use Bash ls to list files in this directory, or specify a filename path to read a specific file.`,
+          errorCode: 10,
+        }
+      }
+    } catch (e) {
+      if (!isENOENT(e)) throw e
+      // ENOENT = 文件还不存在，放行，call() 会通过 findSimilarFile 给出友好建议
+    }
+
     // Binary extension check (string check on extension only, no I/O).
     // PDF, images, and SVG are excluded - this tool renders them natively.
     const ext = path.extname(fullFilePath).toLowerCase()

packages/builtin-tools/src/tools/FileWriteTool/FileWriteTool.ts

@@ -184,6 +184,17 @@ export const FileWriteTool = buildTool({
     let fileMtimeMs: number
     try {
       const fileStat = await fs.stat(fullFilePath)
+      // 预检：如果路径已是一个存在的目录，及时拒绝并给出指引
+      // 避免 AI 模型传入目录路径（如 my-docs/analysis/api/）后，
+      // Write 工具先 mkdir 再写文件时抛出原始 EISDIR 错误，
+      // 导致模型不知如何处理、可能误删目录内容。
+      if (fileStat.isDirectory()) {
+        return {
+          result: false,
+          message: `Cannot write to '${file_path}': the specified path is an existing directory. To write a file inside this directory, use a path that includes a filename with extension, e.g. '${file_path}/<filename>.md'. Use Bash ls to list existing files in this directory.`,
+          errorCode: 5,
+        }
+      }
       fileMtimeMs = fileStat.mtimeMs
     } catch (e) {
       if (isENOENT(e)) {

packages/builtin-tools/src/tools/FileWriteTool/prompt.ts

@@ -14,5 +14,6 @@ Usage:
 - This tool will overwrite the existing file if there is one at the provided path.${getPreReadInstruction()}
 - Prefer the Edit tool for modifying existing files \u2014 it only sends the diff. Only use this tool to create new files or for complete rewrites.
 - NEVER create documentation files (*.md) or README files unless explicitly requested by the User.
-- Only use emojis if the user explicitly requests it. Avoid writing emojis to files unless asked.`
+- Only use emojis if the user explicitly requests it. Avoid writing emojis to files unless asked.
+- The file_path must be a distinct file path, not a directory path. If the path resolves to an existing directory, the tool will reject it with a clear error message. Use a path that includes a filename with an appropriate extension (e.g., \`my-docs/analysis/api/report.md\`).`
 }