fix dll overrides & add disable UMU

README.md

@@ -69,7 +69,8 @@ A sync also carries **how the apps are set up**: the Wine/Proton build and prefi
 
 - **System Wine** — uses the `wine` binary from PATH.
 - **Imported builds** — drop any wine or Proton build into `files/wines/`. The folder may contain the build directly, or one level of nesting (zip-extracted layouts are detected automatically). After the copy, PLWL rewires the build's absolute symlinks to relative ones and restores the executable bit on the binaries it needs to run (`proton`, `wine`, `wineserver`, `winetricks`), so a build that arrived from a zip or another machine works without further fiddling. A build can also be given a **displayed name** of its own (Wine versions): it is used everywhere the build is offered — library config, settings and the *Open with PLWL* popup — while the folder in `files/wines/` keeps its name and the symlinks inside prefixes stay valid.
-- **Proton without Steam** — fully supported. Proton is invoked like Steam does it: `STEAM_COMPAT_CLIENT_INSTALL_PATH` points to a fake steam client folder, `STEAM_COMPAT_DATA_PATH` is a per-build compat folder, and the prefix lives at `<compat>/pfx` which PLWL links to its own prefix folder. No Steam installation required (GE builds work out of the box; for a few Valve builds that refuse to run without a client, PLWL fakes a minimal steam folder in `files/data/fake-steam`).
+- **Proton without Steam** — fully supported. Proton is invoked like Steam does it: `STEAM_COMPAT_DATA_PATH` is a per-build compat folder linked to the launcher's own prefix, and `STEAM_COMPAT_CLIENT_INSTALL_PATH` points at an installed Steam client when there is one (Proton reads its legacy DLLs and `steamclient.so` from there, read-only) and at the empty `files/data/fake-steam` otherwise. GE builds work out of the box: PLWL launches through Proton's built-in UMU path (`UMU_ID`), which needs no Steam client at all. An app that breaks under umu.exe has a per-app **Disable UMU** switch in its config — PLWL then runs the build's own wine directly (Proton's `runinprefix` verb): no umu.exe/steam.exe launcher and no Proton prefix setup take part, so the run stays as close to plain wine as possible. (Proton's session init still reads `STEAM_COMPAT_CLIENT_INSTALL_PATH` on every verb; a disableUmu run gets the empty `fake-steam` folder and nothing is copied out of it.)
+- **One C: drive per prefix** — Proton normally keeps its prefix one level deeper (`<compat>/pfx/drive_c`) than wine (`<prefix>/drive_c`), which left a prefix used with both kinds with two separate C: drives (two registries, two sets of saves). Whenever a prefix has no `pfx` yet (a fresh prefix, or a plain-wine prefix first used through Proton), PLWL makes `pfx` a relative symlink back to the prefix itself, so Proton and wine share one `drive_c`, one registry and one `dosdevices`. Existing layouts are left exactly as they are — prefixes from older versions keep their real `pfx/` folder, and a prefix with both `drive_c` trees keeps both, because two live Windows installs cannot be merged safely (both stay visible to the prefix import picker).
 
 ## Translations
 

development.md

@@ -122,6 +122,34 @@ handlers in src/ipc/. Keep new APIs in that pattern.
   relative target) and after a unit lands (healUnitRoots). dosdevices drive
   mappings and targets that leave files/ (a mount, a system path, the user's
   home) stay absolute - they are machine-specific by design.
+- A prefix that has NO `pfx` yet gets ONE C: drive: `pfx` is a relative
+  symlink to the prefix itself, so Proton's `<compatdata>/pfx`
+  (runner.linkPrefix) resolves to `<prefix>` and shares `drive_c`, the
+  registry and `dosdevices` with plain wine. `prefixes.ensureUnifiedPrefix`
+  only ever CREATES that link; an existing layout (a real `pfx/` folder from
+  an older PLWL, a both-drives prefix) is left exactly as it is. Hoisting a
+  prefix's files one level up was tried and removed: it breaks every relative
+  link written against the old depth (the `umu.exe` link into the build is the
+  one that kills a Proton launch), and moving a live Windows install is not
+  the launcher's call. `healPrefix`/`rewireSymlinks` repairs such a prefix by
+  re-anchoring broken relative links through files/. Never assume a single
+  drive_c path: use `prefixDriveRoots()` (deduplicated) and compare realpaths
+  when deciding whether a folder is inside a prefix's C: drive.
+- App launch env is built in runner.buildEnv only. WINEDLLOVERRIDES is an
+  ordered semicolon list: inherited value first, the app's overrides last,
+  because Wine lets a later entry replace an earlier one for the same module.
+  An empty setting (`dll=`) is Wine's "disabled" and must survive the filter.
+  Proton appends its own dxvk/nvapi/steam.exe defaults AFTER everything, so an
+  app override only wins where Proton has no default. `disableUmu` (per app)
+  drops UMU_ID and switches Proton to its `runinprefix` verb, so no
+  umu.exe/steam.exe launcher and no Proton prefix setup take part - the
+  build's own wine runs as close to plain wine as it gets.
+  STEAM_COMPAT_CLIENT_INSTALL_PATH must be set in BOTH modes: Proton's session
+  init reads it on every verb (sync_appcache runs even for runinprefix, and
+  with SteamGameId set a missing variable aborts the launch with a KeyError
+  before wine starts). On the default path it prefers a real Steam client
+  found on the machine; a disableUmu run always gets the empty
+  files/data/fake-steam, whose contents are never read.
 - Wine and Proton create prefix links with ABSOLUTE local targets whenever they
   update a prefix (font/dll stubs, Steam appcache), so on-disk links are not
   always relative after a run: the sync payload relativizes them anyway, and

files/translations/en-us.json

@@ -81,11 +81,14 @@
     "config.prefixDefault": "Default prefix ({0})",
     "config.prefixLocked": "This app was imported from a prefix, its prefix cannot be changed",
     "config.prefixLockedHint": "Pinned to the prefix it was imported from (its paths are stored relative to it)",
+    "config.disableUmu": "Disable UMU (launch with wine directly)",
+    "config.disableUmuHint": "Runs the game with the build's own wine binary instead of its umu.exe/steam.exe launcher - no UMU and no Steam client is started, and Proton's prefix setup is skipped too. This is the closest to a plain wine run.",
     "config.dllOverrides": "DLL overrides",
     "config.overrides.add": "Add override",
     "config.overrides.dll": "DLL name",
     "config.overrides.setting": "Setting",
     "config.overrides.remove": "Remove",
+    "config.overrides.hint": "Wine module names, e.g. dinput8. native,builtin (the default) loads a DLL shipped with the game and falls back to Wine's builtin; disabled blocks the module. 'name=setting' pasted into the name box is split automatically.",
     "config.save": "Save changes",
     "config.shortcut": "Create shortcut",
     "config.shortcutCreated": "Shortcut for {0} created (menu + desktop)",

files/translations/pl.json

@@ -81,11 +81,14 @@
     "config.prefixDefault": "Prefiks domyślny ({0})",
     "config.prefixLocked": "Ta aplikacja została zaimportowana z prefiksu, nie można zmienić jej prefiksu",
     "config.prefixLockedHint": "Przypięta do prefiksu, z którego została zaimportowana (ścieżki trzymane są względem niego)",
+    "config.disableUmu": "Wyłącz UMU (uruchamiaj bezpośrednio wine)",
+    "config.disableUmuHint": "Uruchamia grę bezpośrednio binarką wine z builda, z pominięciem launchera umu.exe/steam.exe — bez UMU i bez uruchamiania klienta Steam, z pominięciem przygotowania prefiksu przez Protona. To najbliżej zwykłego uruchomienia wine.",
     "config.dllOverrides": "Nadpisania DLL",
     "config.overrides.add": "Dodaj nadpisanie",
     "config.overrides.dll": "Nazwa DLL",
     "config.overrides.setting": "Ustawienie",
     "config.overrides.remove": "Usuń",
+    "config.overrides.hint": "Nazwy modułów Wine, np. dinput8. native,builtin (domyślne) wczytuje DLL dołączony do gry, a gdy go nie ma — wbudowany Wine; disabled blokuje moduł. Wklejone 'nazwa=ustawienie' zostanie rozdzielone automatycznie.",
     "config.save": "Zapisz zmiany",
     "config.shortcut": "Utwórz skrót",
     "config.shortcutCreated": "Skrót dla {0} utworzony (menu + pulpit)",

renderer/app.js

@@ -1235,6 +1235,7 @@ async function openGameConfig(id) {
   const lockHint = qs('#gc-prefix-lock-hint')
   if (lockHint) lockHint.style.display = prefixLocked ? '' : 'none'
   renderOverrides(game.dllOverrides || [])
+  qs('#gc-disable-umu').checked = !!game.disableUmu
   renderTools()
 }
 
@@ -1257,10 +1258,12 @@ function renderOverrides(overrides) {
   }
 }
 
+// native,builtin first: that is the default a new override row starts on
+// (load a native DLL when the game has one, fall back to Wine's builtin)
 const OVERRIDE_OPTIONS = [
+  { value: 'native,builtin', label: 'native,builtin' },
   { value: 'native', label: 'native' },
   { value: 'builtin', label: 'builtin' },
-  { value: 'native,builtin', label: 'native,builtin' },
   { value: 'builtin,native', label: 'builtin,native' },
   { value: '', label: 'disabled' }
 ]
@@ -1274,23 +1277,48 @@ function buildOverrideRow(o) {
   `
   row.querySelector('.dll').value = o.dll || ''
   const selectHost = document.createElement('span')
-  new CustomSelect(selectHost, OVERRIDE_OPTIONS, o.setting || 'native')
+  // a stored empty setting IS the "disabled" choice - a `||` fallback would
+  // turn every disabled override back into the default on reopen
+  new CustomSelect(selectHost, OVERRIDE_OPTIONS, o.setting == null ? 'native,builtin' : o.setting)
   row.insertBefore(selectHost, row.querySelector('[data-act=del]'))
   row.querySelector('[data-act=del]').onclick = () => row.remove()
   return row
 }
 
 function addOverrideRow() {
-  qs('#gc-overrides').appendChild(buildOverrideRow({ dll: '', setting: 'native' }))
+  qs('#gc-overrides').appendChild(buildOverrideRow({ dll: '', setting: 'native,builtin' }))
   const rows = qsa('#gc-overrides .override-row')
   rows[rows.length - 1].querySelector('.dll').focus()
 }
 
+// The setting a guide or a launch option uses ("n", "native,builtin", "d"...)
+// mapped onto the values this select offers. Unknown text keeps the select's
+// choice instead of inventing one.
+function normalizeOverrideSetting(raw) {
+  const v = String(raw || '').trim().toLowerCase().replace(/\s+/g, '')
+  if (!v || v === 'd' || v === 'disabled') return ''
+  if (v === 'n' || v === 'native') return 'native'
+  if (v === 'b' || v === 'builtin') return 'builtin'
+  if (v === 'n,b' || v === 'native,builtin') return 'native,builtin'
+  if (v === 'b,n' || v === 'builtin,native') return 'builtin,native'
+  return null
+}
+
 function readOverrides() {
-  return qsa('#gc-overrides .override-row').map(row => ({
-    dll: row.querySelector('.dll').value.trim(),
-    setting: row.querySelector('.custom-select').dataset.value ?? 'native'
-  })).filter(o => o.dll)
+  return qsa('#gc-overrides .override-row').map(row => {
+    let dll = row.querySelector('.dll').value.trim()
+    let setting = row.querySelector('.custom-select').dataset.value ?? 'native,builtin'
+    // "dinput8=native" pasted into the name box is the form every guide uses -
+    // split it here instead of storing a name with '=' that Wine cannot parse
+    const eq = dll.indexOf('=')
+    if (eq > 0) {
+      const pasted = normalizeOverrideSetting(dll.slice(eq + 1))
+      if (pasted !== null) setting = pasted
+      dll = dll.slice(0, eq).trim()
+    }
+    dll = dll.replace(/\.dll$/i, '')
+    return { dll, setting }
+  }).filter(o => o.dll)
 }
 
 async function saveGameConfig() {
@@ -1322,10 +1350,14 @@ async function saveGameConfig() {
     wine: selects['gc-wine'].value,
     prefix,
     env,
-    dllOverrides: readOverrides()
+    dllOverrides: readOverrides(),
+    disableUmu: qs('#gc-disable-umu').checked
   }
   await window.plwl.gamesUpdate(game.id, patch)
   state.games = await window.plwl.gamesList()
+  // show what was actually stored: a pasted "name=setting" was split and a
+  // .dll suffix stripped, so the rows would otherwise disagree with the file
+  renderOverrides(patch.dllOverrides)
   toast(t('config.saved'), 'success')
   if (prefixLockedHint) toast(t('config.prefixLocked'), 'error')
   if (state.currentView === 'gameconfig') {

renderer/index.html

@@ -180,12 +180,19 @@
           <span id="gc-prefix"></span>
           <p class="subtitle" id="gc-prefix-lock-hint" data-t="config.prefixLockedHint" style="display:none"></p>
 
+          <label class="check-label">
+            <input type="checkbox" id="gc-disable-umu">
+            <span data-t="config.disableUmu"></span>
+          </label>
+          <p class="subtitle" data-t="config.disableUmuHint"></p>
+
           <label class="field-label" data-t="config.env"></label>
           <textarea id="gc-env" rows="3" data-ph="config.envHint"></textarea>
 
           <label class="field-label" data-t="config.dllOverrides"></label>
           <div id="gc-overrides" class="overrides"></div>
           <button class="button" id="gc-override-add" data-t="config.overrides.add"></button>
+          <p class="subtitle" data-t="config.overrides.hint"></p>
 
           <div class="form-actions">
             <button class="button danger" id="btn-gc-clear-playtime" data-t="config.clearPlaytime"></button>

src/importer.js

@@ -1,6 +1,7 @@
 'use strict'
 
-const fsp = require('fs').promises
+const fs = require('fs')
+const fsp = fs.promises
 const path = require('path')
 const { DIRS, resolvePortablePath } = require('./paths')
 const { newGame, newGameId, addGame } = require('./library')
@@ -82,8 +83,22 @@ async function importGameFromPrefix(prefix, srcDir, onProgress) {
   const driveRoots = prefixDriveRoots(prefix)
   if (!driveRoots.length) return { ok: false, error: 'no-drive-c' }
   const src = path.resolve(String(srcDir))
+  // realpath on both sides: a unified prefix reaches drive_c through the pfx
+  // symlink too, and that path is the same folder (see ensureUnifiedPrefix)
+  let realSrc
+  try {
+    realSrc = fs.realpathSync(src)
+  } catch {
+    return { ok: false, error: 'outside-drive-c' }
+  }
   const insideDrive = driveRoots.some(root => {
-    const rel = path.relative(root, src)
+    let realRoot
+    try {
+      realRoot = fs.realpathSync(root)
+    } catch {
+      return false
+    }
+    const rel = path.relative(realRoot, realSrc)
     return rel && !rel.startsWith('..') && !path.isAbsolute(rel)
   })
   if (!insideDrive) return { ok: false, error: 'outside-drive-c' }

src/library.js

@@ -217,6 +217,9 @@ function newGame({ id, name, exePath, workdir, mode }) {
     prefix: '',
     args: '',
     dllOverrides: [],
+    // Proton-only switch: keep UMU (the default path) or fall back to the
+    // build's steam.exe launcher for this app (see runner.buildEnv)
+    disableUmu: false,
     env: {},
     iconSource: '',
     playSeconds: 0,

src/openwith.js

@@ -73,6 +73,7 @@ function makeTarget(openPath, wineId, prefixName) {
     prefix: prefixName || '',
     args: '',
     dllOverrides: [],
+    disableUmu: false,
     env: {},
     iconSource: '',
     playSeconds: 0,

src/prefixes.js

@@ -15,6 +15,7 @@ function seed() {
   if (!defs || !Array.isArray(defs.prefixes) || !defs.prefixes.length) {
     const seeded = { default: MAIN, prefixes: [{ name: MAIN, created: Date.now(), locked: true }] }
     if (!fs.existsSync(prefixPath(MAIN))) fs.mkdirSync(prefixPath(MAIN), { recursive: true })
+    ensureUnifiedPrefix(MAIN)
     writeJson(REGISTRY, seeded)
   }
 }
@@ -42,22 +43,65 @@ function prefixExists(name) {
 }
 
 // Every Windows C: drive a prefix has: plain wine keeps one at the top
-// (WINEPREFIX=<prefix>), Proton-managed prefixes nest one under pfx/
-// (WINEPREFIX=<prefix>/pfx). A prefix used with BOTH wine kinds has both,
-// and an import may come from either one - so callers that can accept
-// several get them all, top level first.
+// (WINEPREFIX=<prefix>), legacy Proton-managed prefixes nest one under pfx/
+// (WINEPREFIX=<prefix>/pfx). A prefix used with BOTH wine kinds has both, and
+// an import may come from either one - so callers that can accept several get
+// them all, top level first. A unified prefix (pfx -> .) reaches the same
+// drive twice; it is reported once.
 function prefixDriveRoots(name) {
   const root = prefixPath(name)
   const found = []
+  const seen = new Set()
   for (const base of [root, path.join(root, 'pfx')]) {
     try {
       const driveC = path.join(base, 'drive_c')
-      if (fs.statSync(driveC).isDirectory()) found.push(driveC)
+      if (!fs.statSync(driveC).isDirectory()) continue
+      const real = fs.realpathSync(driveC)
+      if (seen.has(real)) continue
+      seen.add(real)
+      found.push(driveC)
     } catch {}
   }
   return found
 }
 
+function lstatOrNull(p) {
+  try {
+    return fs.lstatSync(p)
+  } catch {
+    return null
+  }
+}
+
+// Wine keeps its C: drive at <prefix>/drive_c, Proton always runs its prefix
+// from <compatdata>/pfx - and PLWL points compatdata at the launcher's prefix
+// folder, so without a link a prefix used with both wine kinds grows TWO C:
+// drives with separate registries, saves and installed DLLs. Making `pfx` a
+// relative symlink back to the prefix itself collapses them: Proton's
+// <compatdata>/pfx resolves to the prefix root, the exact folder wine uses.
+// Every walker PLWL owns (fsutil, symlinks, LAN sync) treats symlinks as
+// links and never follows them, so the self-reference is safe.
+//
+// Only a prefix that has no pfx AT ALL gets the link - that covers a fresh
+// prefix and a plain-wine prefix first used through Proton. An existing
+// layout is left exactly as it is: a prefix from an older PLWL keeps its real
+// pfx/ folder (and here the two wine kinds keep two C: drives), and a prefix
+// with both real drive_c trees keeps them - moving Windows installs around
+// behind the user's back loses data and breaks the absolute/relative links
+// inside them.
+function ensureUnifiedPrefix(name) {
+  if (!name) return false
+  const pfx = path.join(prefixPath(name), 'pfx')
+  if (lstatOrNull(pfx)) return false
+  try {
+    fs.symlinkSync('.', pfx, 'dir')
+    return true
+  } catch {
+    // the prefix folder may not exist yet - the link is added on creation
+    return false
+  }
+}
+
 // True when a path IS one of a prefix's own roots: the prefix folder, its
 // pfx/ or either drive_c. A copy/move import of such a folder would move the
 // prefix's C: drive (or the whole prefix) into files/apps, gutting it - the
@@ -82,6 +126,7 @@ function createPrefix(name) {
   if (clean.toLowerCase() === MAIN.toLowerCase()) return { ok: false, error: 'alreadyExists' }
   if (fs.existsSync(prefixPath(clean))) return { ok: false, error: 'alreadyExists' }
   fs.mkdirSync(prefixPath(clean), { recursive: true })
+  ensureUnifiedPrefix(clean)
   const defs = listPrefixes()
   defs.prefixes.push({ name: clean, created: Date.now() })
   if (!defs.prefixes.some(p => p.name === defs.default)) defs.default = clean
@@ -153,4 +198,4 @@ function setDefaultPrefix(name) {
   return { ok: true }
 }
 
-module.exports = { listPrefixes, savePrefixes, createPrefix, deletePrefix, renamePrefix, setDefaultPrefix, prefixPath, prefixExists, prefixDriveRoots, isPrefixRoot, healPrefix, MAIN }
+module.exports = { listPrefixes, savePrefixes, createPrefix, deletePrefix, renamePrefix, setDefaultPrefix, prefixPath, prefixExists, prefixDriveRoots, isPrefixRoot, healPrefix, ensureUnifiedPrefix, MAIN }

src/runner.js

@@ -2,13 +2,14 @@
 
 const path = require('path')
 const fs = require('fs')
+const os = require('os')
 const { spawn } = require('child_process')
 const { DIRS } = require('./paths')
-const { prefixPath } = require('./prefixes')
+const { prefixPath, ensureUnifiedPrefix } = require('./prefixes')
 const { prefixNameForGame } = require('./library')
 
-// The fake Steam install Proton is pointed at through
-// STEAM_COMPAT_CLIENT_INSTALL_PATH. Both folders Proton links into its prefix
+// The fake Steam install PLWL falls back to when no real Steam client is
+// found (see findSteamClientDir). Both folders Proton links into its prefix
 // have to exist: it symlinks <prefix>/drive_c/Program Files (x86)/Steam/
 // appcache -> <fake>/appcache while setting the prefix up, and a link into a
 // missing folder is a dangling link in a tree that gets synced.
@@ -19,6 +20,73 @@ function ensureFakeSteam() {
   return fake
 }
 
+// Proton expects the Steam client it is normally started by at
+// STEAM_COMPAT_CLIENT_INSTALL_PATH: it copies the client's legacy DLLs from
+// <client>/legacycompat into the prefix, its built-in steam.exe loads the
+// client's own steamclient.so, and media libs come from <client>/ubuntu12_*.
+// A client installed on this machine is worth using (read-only) - without one
+// a Valve build's launch dies in a "steamclient_main.c" assert dialog - and
+// only when there is none does PLWL fall back to the empty fake folder. GE
+// builds don't need any of it: their UMU path never starts steam.exe.
+const STEAM_CLIENT_MARKERS = [
+  ['legacycompat', 'steamclient.dll'],
+  ['ubuntu12_32', 'steamclient.so']
+]
+
+function findSteamClientDir() {
+  const home = os.homedir()
+  const dataHome = process.env.XDG_DATA_HOME || path.join(home, '.local', 'share')
+  const candidates = [
+    process.env.STEAM_COMPAT_CLIENT_INSTALL_PATH,
+    path.join(home, '.steam', 'steam'),
+    path.join(home, '.steam', 'root'),
+    path.join(dataHome, 'Steam'),
+    // flatpak Steam keeps its install inside the sandbox's data dir
+    path.join(home, '.var', 'app', 'com.valvesoftware.Steam', '.local', 'share', 'Steam')
+  ]
+  for (const dir of candidates) {
+    if (!dir) continue
+    for (const marker of STEAM_CLIENT_MARKERS) {
+      if (fs.existsSync(path.join(dir, ...marker))) return dir
+    }
+  }
+  return null
+}
+
+function steamClientDir() {
+  return findSteamClientDir() || ensureFakeSteam()
+}
+
+// Module names travel in a semicolon-separated WINEDLLOVERRIDES list where
+// '=' splits name from setting and ',' separates names - anything else in a
+// name would corrupt the entries around it. A trailing .dll is what guides
+// write; Wine strips it itself, so PLWL stores the bare name.
+function sanitizeDllName(name) {
+  const clean = String(name || '').trim().replace(/\.dll$/i, '')
+  return /^[^;=\s]+$/.test(clean) ? clean : ''
+}
+
+// Wine replaces an earlier entry for the same module with a later one, so an
+// inherited WINEDLLOVERRIDES goes FIRST and the app's own overrides are
+// appended after it. An empty setting is Wine's "disabled" and has to survive
+// as `name=`, not be dropped. Proton appends its own dxvk/nvapi/steam.exe
+// defaults after everything - an app override for one of those modules only
+// takes effect where Proton itself has no default.
+function dllOverridesFor(game, env) {
+  const parts = []
+  const inherited = String(env.WINEDLLOVERRIDES || '').trim().replace(/;+$/, '')
+  if (inherited) parts.push(inherited)
+  for (const entry of game.dllOverrides || []) {
+    if (!entry) continue
+    const dll = sanitizeDllName(entry.dll)
+    if (!dll) continue
+    const setting = String(entry.setting == null ? '' : entry.setting).trim()
+    if (!/^[a-z,]*$/i.test(setting)) continue
+    parts.push(`${dll}=${setting}`)
+  }
+  return parts.join(';')
+}
+
 // Wine only ever repairs links that are BROKEN: a prefix that came from
 // another machine (or from an older PLWL) can still hold absolute links into
 // its build that happen to resolve here, and those would be synced out again.
@@ -74,23 +142,41 @@ function buildEnv({ game, wine }) {
   const isProton = wine && wine.type === 'proton'
   // same fallback the games service snapshots into its running entries
   // (library.prefixNameForGame), so in-use checks always name this folder
-  const prefixDir = prefixPath(prefixNameForGame(game))
+  const prefixName = prefixNameForGame(game)
+  // a prefix with no pfx yet gets the shared-link layout, so every launch -
+  // wine, Proton, tools - lands on that prefix's ONE C: drive; an existing
+  // nested layout is left as it is (see ensureUnifiedPrefix)
+  try {
+    ensureUnifiedPrefix(prefixName)
+  } catch {}
+  const prefixDir = prefixPath(prefixName)
 
   if (isProton) {
-    const fakeSteam = ensureFakeSteam()
-    const buildRoot = path.resolve(wine.path, '..')
-    env.STEAM_COMPAT_CLIENT_INSTALL_PATH = fakeSteam
     env.STEAM_COMPAT_DATA_PATH = path.join(DIRS.DATA, 'compat', game.id)
     env.STEAM_COMPAT_APP_ID = '0'
     env.SteamAppId = '0'
     env.SteamGameId = '0'
+    // Proton's session init reads STEAM_COMPAT_CLIENT_INSTALL_PATH on EVERY
+    // verb: its appcache sync (g_compatdata.sync_appcache) runs even for
+    // runinprefix and does os.environ["STEAM_COMPAT_CLIENT_INSTALL_PATH"] as
+    // soon as SteamGameId is set, so the variable must never be dropped - a
+    // missing one aborts the launch with a KeyError before wine even starts.
+    // Only what it POINTS AT depends on the mode: a UMU run may use a real
+    // client found on this machine, a disableUmu run always gets the empty
+    // fake folder (runinprefix copies nothing out of it; no steam.exe and no
+    // umu.exe is started there).
+    if (game.disableUmu) {
+      delete env.UMU_ID
+      env.STEAM_COMPAT_CLIENT_INSTALL_PATH = ensureFakeSteam()
+    } else {
+      env.STEAM_COMPAT_CLIENT_INSTALL_PATH = steamClientDir()
       // Launch like the UMU protocol does (UMU/PortProton/Heroic): with UMU_ID
-    // set, newer Protons (incl. DW Proton 11, GE-Proton 10+) run the game via
-    // their built-in umu.exe instead of the steam.exe helper, which would
-    // otherwise try to load Steam's steamclient.so and crash with an
-    // "Assertion failed \"!status\"" dialog (steamclient_main.c) when no
-    // Steam client is installed.
+      // set, newer Protons (incl. GE-Proton 9+) run the game through their
+      // built-in umu.exe instead of the steam.exe helper, which needs the
+      // Steam client's DLLs and dies in a "steamclient_main.c" assert dialog
+      // without them (see steamClientDir).
       if (!env.UMU_ID) env.UMU_ID = 'umu-0'
+    }
     env.WINEPREFIX = path.join(env.STEAM_COMPAT_DATA_PATH, 'pfx')
     env.PROTON_LOG_DIR = path.join(DIRS.DATA, 'logs')
     fs.mkdirSync(env.PROTON_LOG_DIR, { recursive: true })
@@ -108,16 +194,25 @@ function buildEnv({ game, wine }) {
     env.WINEPREFIX = prefixDir
   }
 
-  env.WINEDLLOVERRIDES = (game.dllOverrides || [])
-    .filter(o => o && o.dll && o.setting)
-    .map(o => `${o.dll}=${o.setting}`)
-    .join(';')
-  if (!env.WINEDLLOVERRIDES) delete env.WINEDLLOVERRIDES
+  const overrides = dllOverridesFor(game, env)
+  if (overrides) env.WINEDLLOVERRIDES = overrides
+  else delete env.WINEDLLOVERRIDES
 
+  // the app's own environment comes last: it overrides everything above,
+  // including a WINEDLLOVERRIDES configured here
   for (const [k, v] of Object.entries(game.env || {})) env[k] = v
   return { env, prefixDir }
 }
 
+// Proton verbs: 'run' goes through the build's umu.exe/steam.exe launcher,
+// while 'runinprefix' runs the build's wine directly (same session env, no
+// umu/steam launcher ever starts - see game.disableUmu). runinprefix also skips
+// Proton's prefix setup, so a prefix that never saw a normal Proton run stays
+// a plain wine prefix instead of gaining Proton's default DLLs.
+function protonVerb(game) {
+  return game.disableUmu ? 'runinprefix' : 'run'
+}
+
 function parseArgs(args) {
   const out = []
   const re = /"([^"]*)"|'([^']*)'|(\S+)/g
@@ -167,7 +262,7 @@ async function runGame({ game, wine, systemWine, onExit }) {
   let base
   if (isProton) {
     cmd = wine.wineBin || path.join(wine.path, 'proton')
-    base = ['run', exe, ...argList]
+    base = [protonVerb(game), exe, ...argList]
   } else {
     cmd = systemWine ? 'wine' : wine.wineBin
     base = [exe, ...argList]
@@ -200,6 +295,13 @@ async function runGame({ game, wine, systemWine, onExit }) {
       started = true
       const logFile = latestLogPath(game.id)
       const ws = openLatestLog(game.id)
+      // a launch line of our own before the raw wine output: when a game
+      // refuses to start, "which prefix, which overrides, umu or steam.exe"
+      // is exactly what has to be answerable from the log
+      ws.write(`[plwl] ${cmd} ${base.join(' ')}\n`)
+      ws.write(`[plwl] WINEPREFIX=${env.WINEPREFIX}\n`)
+      if (env.WINEDLLOVERRIDES) ws.write(`[plwl] WINEDLLOVERRIDES=${env.WINEDLLOVERRIDES}\n`)
+      if (isProton) ws.write(`[plwl] proton launcher: ${game.disableUmu ? 'direct wine (no UMU, no Steam)' : `umu.exe (UMU_ID=${env.UMU_ID})`}\n`)
       child.stdout.pipe(ws)
       child.stderr.pipe(ws)
       child.unref()
@@ -237,7 +339,7 @@ async function runTool({ game, wine, tool, args, systemWine }) {
   let base
   if (isProton) {
     cmd = wine.wineBin || path.join(wine.path, 'proton')
-    base = ['run', tool, ...argList]
+    base = [protonVerb(game), tool, ...argList]
   } else if (systemWine) {
     cmd = tool
     base = argList

src/symlinks.js

@@ -16,7 +16,11 @@
 //
 // Everything here rewires a link to a RELATIVE path when the file it points at
 // can be found locally, so the tree stays relocatable forever, and restores
-// the executable bit on the binaries a wine/proton build needs.
+// the executable bit on the binaries a wine/proton build needs. An absolute
+// link is always rewritten; a relative one is only touched when it no longer
+// resolves, because a tree that changed layout (a prefix whose contents moved
+// one level up, see prefixes.ensureUnifiedPrefix) keeps relative links written
+// against the old depth and every one of them breaks at once.
 
 const fsp = require('fs').promises
 const fs = require('fs')
@@ -116,10 +120,11 @@ function relativeTarget(link, target, roots) {
   return null
 }
 
-// Rewire every absolute symlink under `root` that can be expressed relative to
-// `roots` (usually [root, DIRS.FILES]). Returns how many links changed. A link
-// may only become rewirable once another link it chains through has been
-// fixed, so the pass repeats until nothing changes.
+// Rewire the symlinks under `root` that can be expressed relative to `roots`
+// (usually [root, DIRS.FILES]): absolute ones always, relative ones only when
+// they no longer resolve. Returns how many links changed. A link may only
+// become rewirable once another link it chains through has been fixed, so the
+// pass repeats until nothing changes.
 async function rewireSymlinks(root, roots = []) {
   if (!root) return 0
   const candidates = [root, ...roots.filter(r => r && r !== root)]
@@ -135,8 +140,13 @@ async function rewireSymlinks(root, roots = []) {
       } catch {
         continue
       }
-      if (!path.isAbsolute(target)) continue // already relocatable
-      const next = relativeTarget(link, path.normalize(target), candidates)
+      const absolute = path.isAbsolute(target)
+      // a relative link that still resolves is already relocatable - only a
+      // broken one is worth touching, and the suffix search in relativeTarget
+      // finds the file it was pointing at before the layout changed
+      if (!absolute && exists(path.resolve(path.dirname(link), target))) continue
+      const from = absolute ? path.normalize(target) : path.resolve(path.dirname(link), target)
+      const next = relativeTarget(link, from, candidates)
       if (!next || next === target) continue
       try {
         await fsp.unlink(link)