diff --git a/hosts/yarn/default.nix b/hosts/yarn/default.nix
index 0e1154a..bf548b8 100644
--- a/hosts/yarn/default.nix
+++ b/hosts/yarn/default.nix
@@ -159,17 +159,21 @@
       };
     };
 
-  # Steam launch options + per-app compat-tool pin via steam-config-nix
-  # (different-name/steam-config-nix). The patcher runs as a system oneshot
-  # at activation; closeSteam = true ensures Steam is shut down before the
-  # localconfig.vdf write so Steam can't clobber it on its next exit.
+  # Steam launch options via steam-config-nix (different-name/steam-config-
+  # nix). The patcher runs as a system oneshot at activation; closeSteam =
+  # true ensures Steam is shut down before the localconfig.vdf write so Steam
+  # can't clobber it on its next exit.
+  #
+  # No declarative compat-tool pin: nixpkgs' proton-ge-bin registers under
+  # its versioned tool id (e.g. GE-Proton10-34), not the generic "GE-Proton"
+  # string steam-config-nix's README assumes, so writing the latter resolved
+  # to no installed tool and silently fell back to bundled Proton. Pick the
+  # tool in Steam UI > Properties > Compatibility instead.
   programs.steam.config = {
     enable = true;
     closeSteam = true;
-    defaultCompatTool = "GE-Proton";
     apps."fh5" = {
       id = 1551360;
-      compatTool = "GE-Proton";
       launchOptions.env = {
         # OptiScaler FSR 4 INT8 path on this RDNA 3 (Navi 32) box.
         # PROTON_FSR4_UPGRADE opts FH5 into Proton's FSR 4 DLL upgrade;