---
title: "Troubleshooting Electron 39.6.0 Tag Build Failure on Windows"
description: "It's been quite a while since I last built Electron on Windows. Yesterday afternoon, I tried building the electron@39.6.0 tag, but it failed repeatedly.…"
date: 2026-03-10
tags: ["electron"]
lang: en
url: https://bugs.cc/posts/troubleshooting-electron-39.6.0-tag-build-failure-on-windows/
translation: https://bugs.cc/zh/posts/troubleshooting-electron-39.6.0-tag-build-failure-on-windows/
---

# Troubleshooting Electron 39.6.0 Tag Build Failure on Windows

It's been quite a while since I last built Electron on Windows. Yesterday afternoon, I tried building the [electron@39.6.0] tag, but it failed repeatedly. Strangely, the latest commit built without any issues. I ended up debugging it late into the night.

I tried both PowerShell and Command Prompt, rebuilt the entire source tree from scratch, and even restarted my machine — to no avail.

**Reproduction Environment:**

- Electron 39.6.0 (tag)
- Windows 10/11
- Tested in both PowerShell and Cmd

My first suspicion was a depot_tools version issue, but [@electron/build-tools] updates depot_tools automatically before starting the build, so that wasn't the culprit.

Switching to the latest commit worked fine, confirming the problem wasn't system-wide.

The error suggested running `.\siso_failed_commands.bat` to replay the failed commands. When I executed it manually, the build succeeded without errors.

![Build Failure Log](https://bugs.cc/images/troubleshooting-electron-39.6.0-tag-build-failure-on-windows/failed-log.jpg)

![Executing siso_failed_commands.bat](https://bugs.cc/images/troubleshooting-electron-39.6.0-tag-build-failure-on-windows/siso-exec.png)

Manually running the batch file worked perfectly.

Taking a closer look at the error log, I spotted this:

```text
err: fork/exec /Users/live/.electron_build_tools/third_party/depot_tools/bootstrap-2@3_11_8_chromium_35_bin/python3/bin/python3.exe: The system cannot find the path specified.
```

The `C:` drive letter had been dropped. However, the path in `siso_failed_commands.bat` still included it.

![siso_failed_commands.bat Content](https://bugs.cc/images/troubleshooting-electron-39.6.0-tag-build-failure-on-windows/siso-bat-content.png)

This indicated that siso (the build executor) was stripping the drive letter prefix when spawning processes (`C:\foo` → `\foo`).

If the source code had been on the C: drive, the issue wouldn't have occurred. On Windows, paths starting with `/` are resolved relative to the root of the current drive of the process.

By default, [@electron/build-tools] installs depot_tools to `%USERPROFILE%\.electron_build_tools\third_party`.

The siso process was running with its working directory set to the build output folder: `D:\electron\release-39.6.0\src\out\Release`.

Since my Electron source was on the D: drive, stripping the drive letter turned the Python path into:

`D:/Users/live/.electron_build_tools/third_party/depot_tools/bootstrap-2@3_11_8_chromium_35_bin/python3/bin/python3.exe`

Which obviously didn't exist — hence "The system cannot find the path specified." 🤷‍♂️

In short: the build only fails if depot_tools and the Electron/Chromium source tree are on **different drives**. This also explains why Electron's CI always succeeds.

I eventually tracked the issue down to this Chromium change: <https://chromium-review.googlesource.com/c/build/+/7134259>

**Root Cause:** In Go, slices are reference types. Modifying a slice in place affects all references sharing the same backing array, causing the modification to be incorrectly propagated to later uses.

**Fix:** Use `slices.Clone()` to create an independent copy.

For now, my workaround is to keep the Electron source tree on the C: drive.

[electron@39.6.0]: https://github.com/electron/electron/tree/v39.6.0
[@electron/build-tools]: https://github.com/electron/build-tools