# CoH3 Build Studio 2.1.7 — Installer compatibility fix

- Fixed the cumulative patch rejecting the earlier **2.1.6 Runtime Patch**, including installations with the **Historical Front Hotfix**. Those packages set the installed version to 2.1.6, but the later 2.1.6 installer only accepted source versions through 2.1.5.
- Recognises the supplied 2.0.1–2.1.5 releases and the three recovered 2.1.6 states by their application-file fingerprints. Version numbers alone do not authorise overwriting an unknown installation.
- Includes the current 2.1.6 Map Atlas corrections and NATO formation symbols. This release changes installation compatibility and version labels; it does not add new historical claims.
- Installer errors show the detected version, target version, selected folder and a local diagnostic-log path. Primary installer messages follow the chosen PL / EN / DE / RU / ZH language.
- Retains the existing Electron runtime, unchanged application files and a rollback copy. The update does not read or modify the Studio user-data folder containing builds, notes, guides, preferences or personal media. Re-running an already installed patch is harmless.

## Install

Save your work and close all Studio windows. Run **CoH3-Build-Studio-2.1.7-Patch.exe** and select the existing installation folder containing **CoH3 Build Studio.exe**. Do not select the downloads folder or `resources/app` itself. No uninstall or reset of user data is needed. This is a cumulative patch, not a full installer; an intact supported installation is required.

If installation is rejected, the message now identifies the version and folder it inspected. Send that message or the diagnostic log so an unrecognised installation can be examined without blindly overwriting it.

## Verification scope

See `qa-2.1.7-installer.json` for actual PowerShell execution against recovered release files, idempotency, rejection and rollback checks, and `qa-2.1.7-package.json` for extraction/hash verification of the compiled installer. These checks run on Linux with PowerShell and Electron. Native Windows PowerShell 5.1, the Windows installer UI, file locking and a real game session require Windows verification.