> For the complete documentation index, see [llms.txt](https://docs.kouch.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.kouch.dev/docs/adr/0010-mods-netplay-game-settings.md).

# ADR 0010: Per-game Workshop mods, Steam netplay with matched mods, game-style settings

## Status

Accepted 2026-09-26. Pulls work forward from FEATURE\_PLAN Phase 5 (netplay) and Phase 7 (Workshop).

## Decision

**Game-style settings**

* Profile schema v2 adds `options`: typed settings declared by the profile.
* Each option is applied either as a launch argument or as a `config_edit`.
* They appear in a game-style options menu, with tabs Graphics, Controls, Audio, Multiplayer and Advanced.
* Options can be set per emulator and per game.

**Per-game mods**

* Sources: Workshop items tagged `mod`, a local `mods` folder, and `.kod` files that contain a `mods/` folder.
* Mods must be data only. They go through the theme validator plus an executable denylist.
* Mods are applied before launch and reverted after the game exits.
* A manifest records every file placed, so the revert still happens on the next start after a crash.

**Steam netplay**

* Lobby data carries:
  * the game hash
  * the emulator and its version
  * the ordered list of mods
* A player can join only if their own copy of the game has the same hash. **The ROM is never transferred.**
* Missing Workshop mods are downloaded automatically. Local-only mods must match by hash.
* Traffic goes over Steam's relay, through a local proxy to the emulator's own netplay. Each profile describes that netplay through a `netplay` adapter.

## Consequences

* Workshop items and Steam invites need Kouch's own app id. Lobbies can be tested on app 480.
* LAN play Mode A (ADR 0007) stays as the option that works without Steam.


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