Windows 11 Insider Preview Build 26300.7939 adds a registry switch that locks batch files while they execute, preventing mid‑run modifications that can cause “file in use” errors. The setting is enabled by creating a DWORD value named LockBatchFilesWhenInUse under HKLM\Software\Microsoft\Command Processor and setting it to 1. Once active, the command processor holds an exclusive lock on each batch file for the entire run, which stops rogue installers or driver updates from corrupting scripts on the fly. After applying the tweak, a simple self‑modifying script runs without error, confirming the protection is working.

How to lock batch files in Windows 11 Insider Preview Build 26300.7939

The latest Dev Channel preview adds a registry switch that stops batch scripts from being altered while they run. This article shows exactly where to poke the Registry, why it matters, and how to confirm the setting is actually doing its job.

Why the new lock matters

A handful of insiders reported mysterious “file in use” errors after a recent driver update rewrote a maintenance script on the fly. The culprit turned out to be Windows allowing the batch file to be edited while the Command Processor was still executing it. With the new LockBatchFilesWhenInUse value, the system takes a brief lock at launch and keeps the file read‑only for the duration of the run, cutting down on those intermittent failures.

Enabling the lock

First, open the Registry Editor with administrative rights – this is required because the key lives under HKLM. Navigate to HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor. If the Command Processor subkey doesn’t exist, create it. Then add a new DWORD value named LockBatchFilesWhenInUse and set it to 1. Setting the value to 1 tells the command processor to acquire an exclusive lock on any batch file as soon as execution starts, preventing other processes (including rogue installers) from sneaking in changes mid‑flight.

Testing that it works

A quick sanity check is to run a simple script that appends text to itself while looping. Without the lock, the script will eventually throw “Access denied” or silently corrupt its own contents. After enabling the registry key, the same script runs to completion and the file remains pristine. Observing this behavior proves the lock is active without needing any special diagnostics tools.

When you might skip it

If batch files are only used in a controlled environment – for example, a single‑user workstation that never runs third‑party installers – the extra registry tweak adds little value. In those cases, the default behavior is fine and fiddling with HKLM can feel like overkill.

That’s all there is to it. Give the lock a try next time a script mysteriously crashes mid‑run; you might just save yourself a headache.

Announcing Windows 11 Insider Preview Build 26300.7939 (Dev Channel)

Hello Windows Insiders, today we are releasing Windows 11 Insider Preview Build 26300.7939 (KB 5077243) to the Dev Channel.

Announcing Windows 11 Insider Preview Build 26300.7939 (Dev Channel)