Edit tool fails to add trailing newline when creating new files (oldString === "")

[dosmanak]

When using the Edit tool to create new files (with oldString === ""), the tool writes the newString content exactly as provided without ensuring the file ends with a newline character.

Problem Details

In packages/opencode/src/tool/edit.ts (

opencode/packages/opencode/src/tool/edit.ts

Line 37 in 3c96bf8

export const EditTool = Tool.define("edit", {

), the new file creation path (lines ~55-65) handles the case where params.oldString === "":

if (params.oldString === "") {
  const existed = await Filesystem.exists(filePath)
  contentNew = params.newString
  // ...
  await Filesystem.write(filePath, params.newString)  // ← No EOF newline handling

Unlike the existing file modification path which preserves line ending behavior through detectLineEnding() and convertToLineEnding(), the new file creation path performs no EOF newline validation or enforcement.

Expected Behavior

When creating new files via the Edit tool, the content should automatically have a trailing newline added if one is not present, ensuring consistency with the project's coding standards.

Current Behavior

New files are created with exactly the content provided in newString, regardless of whether it ends with a newline.

Proposed Solution

Add EOF newline enforcement in the new file creation path, similar to how existing file edits handle line endings:

if (params.oldString === "") {
  // ... existing code ...
  let contentToWrite = params.newString
  if (!contentToWrite.endsWith('\n')) {
    contentToWrite += '\n'
  }
  await Filesystem.write(filePath, contentToWrite)

OpenCode version

1.1.56

Steps to reproduce

Let the edit tool create a new text file

Screenshot and/or share link

No response

Operating System

GNU/Linux Archlinux

Terminal

kitty

[github-actions]

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[github-actions]

Thanks for updating the issue! It now includes the required details — a clear description with a specific code reference, reproduction steps, and system information. Everything looks good.

[ariane-emory]

This sounds it would be undesirable behaviour to me. Files without a trailing new line are often useful, and agents ought have an easy way to write such files if they want to. Forcing a trailing newline simply makes the edit tool less powerful and less flexible.

[dosmanak]

I understand in case of creating binary files, but for text files a newline at the end of file is good practice and a POSIX standard.
See https://stackoverflow.com/a/729795/1849577

[ariane-emory]

Personally, I often require Markdown files without a trailing newline.