diff --git a/src/app.rs b/src/app.rs
index 3804775..b523422 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -2177,7 +2177,7 @@ fn group_thousands(digits: &str) -> String {
     let len = bytes.len();
     let mut out = String::with_capacity(len + len / 3);
     for (i, b) in bytes.iter().enumerate() {
-        if i > 0 && (len - i) % 3 == 0 {
+        if i > 0 && (len - i).is_multiple_of(3) {
             out.push(',');
         }
         out.push(*b as char);
diff --git a/src/game_launch.rs b/src/game_launch.rs
index bb53eb7..a5a4a1f 100644
--- a/src/game_launch.rs
+++ b/src/game_launch.rs
@@ -58,6 +58,7 @@ pub fn launch(
     }
 
     prepare_prefix(profile, log)?;
+    ensure_dll_override(profile, log);
     ensure_license(profile, log)?;
 
     let mut cmd = Command::new(&profile.runner);
@@ -95,6 +96,99 @@ pub fn launch(
     Ok(())
 }
 
+/// The registry key Wine reads DLL overrides from, and the one value the hook needs.
+///
+/// Wine loads its own builtin `version.dll` unless an override says otherwise, so the
+/// game-directory proxy is ignored by default. `WINEDLLOVERRIDES` fixes that only for
+/// a process we spawn ourselves — it cannot help a player who presses Play in Steam,
+/// which is why the old advice was to paste launch options by hand (see
+/// `setup::STEAM_LAUNCH_OPTIONS`). Asking a player to edit launch options is exactly
+/// the kind of step that makes this unusable for anyone who does not already know what
+/// a DLL override is.
+///
+/// Persisting the override in the prefix registry removes the manual step entirely: it
+/// survives restarts and applies to every launch path, including Steam. This mirrors
+/// what BepInEx documents for Proton (configure the proxy in winecfg rather than the
+/// environment) and what Proton itself already does in this prefix for other titles.
+const DLL_OVERRIDE_KEY: &str = r"HKCU\Software\Wine\DllOverrides";
+const HOOK_DLL_VALUE: &str = "version";
+const HOOK_DLL_OVERRIDE: &str = "native,builtin";
+
+/// `reg add` argv that persists the hook's DLL override, native-first with a builtin
+/// fallback. `/f` makes it idempotent, so this is safe to run on every launch and
+/// repairs a prefix a player has reset or replaced.
+fn dll_override_args() -> [&'static str; 10] {
+    [
+        "reg",
+        "add",
+        DLL_OVERRIDE_KEY,
+        "/v",
+        HOOK_DLL_VALUE,
+        "/t",
+        "REG_SZ",
+        "/d",
+        HOOK_DLL_OVERRIDE,
+        "/f",
+    ]
+}
+
+/// Persist the hook's DLL override into the prefix, so the game loads the proxy no
+/// matter how it is started.
+///
+/// Best-effort by design: a failure here is not fatal, because a launch we spawn also
+/// carries `WINEDLLOVERRIDES`. It is reported in plain language rather than as a Wine
+/// error, since the player cannot act on the latter.
+fn ensure_dll_override(profile: &GameProfile, log: &Log) {
+    if profile.wine_prefix.trim().is_empty() {
+        return;
+    }
+    let mut cmd = Command::new(&profile.runner);
+    cmd.args(dll_override_args())
+        .current_dir(&profile.game_dir)
+        .stdout(Stdio::null())
+        .stderr(Stdio::null());
+    for (k, v) in &profile.env {
+        cmd.env(k, v);
+    }
+    cmd.env("WINEPREFIX", &profile.wine_prefix);
+    match cmd.status() {
+        Ok(status) if status.success() => {
+            say(log, "[launcher] game files ready (mod support enabled)");
+        }
+        Ok(_) | Err(_) => say(
+            log,
+            "[launcher] could not pre-enable mod support in the game prefix; \
+             launching anyway (this launch still enables it directly)",
+        ),
+    }
+}
+
+#[cfg(test)]
+mod override_tests {
+    use super::*;
+
+    #[test]
+    fn dll_override_is_persisted_native_first_and_idempotently() {
+        let args = dll_override_args();
+        assert_eq!(args[0], "reg");
+        assert_eq!(args[1], "add");
+        assert_eq!(
+            args[2], r"HKCU\Software\Wine\DllOverrides",
+            "Wine reads overrides from this key; a typo silently leaves the hook unloaded"
+        );
+        assert_eq!(args[4], "version", "the hook ships as a version.dll proxy");
+        assert_eq!(
+            args[8], "native,builtin",
+            "native first so the proxy wins, builtin as fallback so a missing proxy \
+             cannot make the game unlaunchable"
+        );
+        assert_eq!(
+            args[9], "/f",
+            "idempotent, so running it on every launch repairs a reset prefix"
+        );
+    }
+}
+
 /// The `WINEDLLOVERRIDES` value the game must be started with.
 ///
 /// The hook ships as a `version.dll` proxy inside the game directory, and Proton
diff --git a/src/setup.rs b/src/setup.rs
index 0fba7cb..2b7ef9c 100644
--- a/src/setup.rs
+++ b/src/setup.rs
@@ -126,8 +126,14 @@ pub fn hook_dll_deployed(game_dir: &Path) -> bool {
     game_dir.join("version.dll").exists()
 }
 
-/// The Steam launch options the user needs to paste in to enable the override.
-/// Proton loads local DLLs named in WINEDLLOVERRIDES ahead of system ones.
+/// Steam launch options that enable the hook's DLL override.
+///
+/// Kept only as a fallback to show a user who runs the game outside this launcher on
+/// a prefix we have never prepared. It is NOT the normal path any more: the launcher
+/// persists the override in the prefix registry itself
+/// (`game_launch::ensure_dll_override`), which applies to every launch including
+/// Steam's own Play button. Telling a player to paste launch options is exactly the
+/// kind of manual step this launcher exists to remove.
 pub const STEAM_LAUNCH_OPTIONS: &str = "WINEDLLOVERRIDES=\"version=n,b\" %command%";
 
 // ── Game launch ───────────────────────────────────────────────────────────────