foch

Foch analyzes an ordered Europa Universalis IV playset and writes a separate, deterministic merged mod. It keeps the compatible contributions of each mod and reports genuine conflicts for review instead of silently picking a winner. Source mods and the game installation are only read. The foch-cli crate builds the foch program, including the foch lsp language server; the foch crate is the library behind it. foch-annotation, foch-lsp, foch-runner and foch-test are internal libraries of the program, published because crates.io builds foch-cli from published crates only; their Rust APIs carry no semver promise.

Foch supports Europa Universalis IV only and is alpha software: merging is not yet reliable across arbitrary modlists, so check a merged mod in game. The development plugin launcher supports isolated Windows x64 EU4 launches with a separately built DLL host; see the plugin deployment commands. Read the current boundary before relying on merge output.

Install

foch is built for Linux x64, macOS arm64 and Windows x64. The install section of the project README lists the channels a release has been installed and verified from. foch --version prints foch-cli <version> and the cwt-schema id of the rules embedded in that release.

The crates.io package foch 0.1.0 is an older, unrelated product. If you installed it, run cargo uninstall foch before installing foch-cli; both provide a foch executable.

First run

An installed program is not yet ready to merge. Foch first needs an EU4 base-data snapshot built from your own game installation:

foch data build eu4 --from-game-path "/path/to/Europa Universalis IV" --game-version auto --install

Build and try it walks through that setup and a first merge. Installation says nothing about merge quality, which the project measures separately; see the project status and the documentation.

Source and licensing

Foch's own code is AGPL-3.0-only. The program also contains an adaptation of Mergiraf (GPL-3.0-only) and embeds a rule pack compiled from the CWTools EU4 config (MIT), so the foch library and every foch program are distributed as AGPL-3.0-only AND GPL-3.0-only AND MIT; the source of the other five crates is AGPL-3.0-only. Each program also statically links Rust crates under their own licenses. See NOTICE.md and THIRD-PARTY-LICENSES.txt.

The source of each release is tag v<version> of https://github.com/Acture/foch with its two build submodules, src/packages/tree-sitter-paradox and src/packages/foch/vendor/cwtools-eu4-config. It is published as foch-<version>-source.tar.gz on that tag's GitHub release; GitHub's automatic source downloads leave out the submodules.