improve native isolation

development.md

@@ -15,11 +15,14 @@ src/               main process (Node/Electron backend)
     lansync.js     LAN sync handlers (identity, devices, re-roll, sync + progress)
   runner.js        spawns wine/proton (env, prefix, playtime, logs) and owns
                    spawnTracked() - the log/playtime/exit tail every run shares
-  linuxrunner.js   native Linux apps: redirected HOME/XDG, bwrap or plain run
+  linuxrunner.js   native Linux apps: redirected HOME/XDG, the isolation level
+                   (none/relaxed/isolated/auto) and the handed-document path
   linuxapp.js      native app detection (ELF/AppImage/.desktop) + icon lookup
   sandbox.js       bubblewrap probe (functional, cached) + buildBwrapArgs
+                   (+ FS_ROOT, the one mount the relaxed level adds)
   library.js       apps registry (apps.json) + settings + playtime files, plus
-                   the "which prefix does this app use" / in-use guards
+                   the "which prefix does this app use" / in-use guards and
+                   the isolation-mode gate on the way in
   wines.js         wine/proton build scan, registry, portable symlink healing
   prefixes.js      prefix registry (files/wineprefixes)
   symlinks.js      relative symlink rewiring + executable-bit restoration
@@ -67,12 +70,13 @@ Renderer never touches Node/Electron directly — everything goes through the `w
 - Registries (apps.json, wines.json, prefixes.json) are rewritten whole via writeJson(); playtime lives in its own tiny file so the registry is not rewritten while a game runs.
 - Deleting user data needs a confirm modal; best-effort cleanup is try/catch-and-ignore with a comment saying why it is safe to ignore.
 - Windows apps run through runGame()/buildEnv() — never spawn wine directly elsewhere (prefix handling, Proton env and playtime live there).
-- Native Linux apps run through linuxrunner.runLinuxGame()/buildLinuxEnv() the same way: HOME and the XDG folders are redirected into `{prefix}/linux_pfx/`, and bwrap (when the probe says it works) forces the same layout with mounts. Never spawn a native app elsewhere. `game.kind` is absent on old entries — that means Windows; `game.isolation` is `auto` (bwrap when usable, plain run otherwise), `off` or `require` (refuse to start instead of quietly weakening). The chosen backend always lands in the log and the UI (a silent downgrade is the failure mode to avoid).
-- Under bwrap ONLY two things stay writable: the redirected home and the app's own folder (`writableAppDir`: inside files/apps, or the folder the app was imported from — never `/usr`, `/etc`, `/bin`… and never files/wines). Portable apps write logs and data next to themselves and a read-only app folder makes them refuse to start (Prism Launcher: "couldn't create a log file - Read-only file system"). Everything else is `EROFS` by design.
+- Native Linux apps run through linuxrunner.runLinuxGame()/buildLinuxEnv() the same way: HOME and the XDG folders are redirected into `{prefix}/linux_pfx/`, and bwrap (when the probe says it works) forces the same layout with mounts. Never spawn a native app elsewhere. `game.kind` is absent on old entries — that means Windows; `game.isolation` is one of four levels, resolved by linuxrunner.resolveLevel: `none` (plain run), `relaxed` (bwrap + the whole host filesystem mounted writable at sandbox.FS_ROOT) and `isolated` (bwrap with the stock read-only profile), with `auto` (default) meaning relaxed where bwrap works and none where it does not. Only `auto` may weaken itself — an explicit relaxed/isolated answers `sandbox-required` instead ("no silent downgrade"), and library.js maps the values launcher 0.5.x wrote (`off` → none, `require` → isolated) both when reading the registry and when a patch is saved. The level always lands in the log and the UI. resolveLevel awaits the probe when nothing has measured yet: a shortcut boots HEADLESS, so no renderer ran `sandbox:status` — without that wait `auto` would read an empty cache and quietly pick `none` (and an explicit level would refuse a machine that can sandbox perfectly well).
+- Under bwrap ONLY two things stay writable: the redirected home and the app's own folder (`writableAppDir`: inside files/apps, or the folder the app was imported from — never `/usr`, `/etc`, `/bin`… and never files/wines). Portable apps write logs and data next to themselves and a read-only app folder makes them refuse to start (Prism Launcher: "couldn't create a log file - Read-only file system"). Everything else is `EROFS` by design — at the isolated level. Relaxed is the deliberate exception and says so in the UI: `FS_ROOT` is the same filesystem, mounted writable, so "everything else" is only unreachable through the real paths.
 - Two pipes feed one log in spawnTracked: neither may end the stream (pipe(ws, { end: false }), closed when both sources drained, at the latest LOG_DRAIN_MS after the exit) and the write stream carries an error listener. Ending it at `exit` while a pipe still had data killed the whole launcher with ERR_STREAM_WRITE_AFTER_END.
 - A prefix or wine build a running app uses cannot be renamed/deleted (wine holds files open there): the guards sit next to the handlers in src/ipc/, use the games service's running list plus library.js helpers (prefixNameForGame/gamesUsingPrefix/is*InUse) and answer `{ ok:false, error:'inUse'|'hasApps', apps:[names] }` for the toast.
-- Long operations stream progress through the single import:progress slot as `{ phase: 'count'|'copy'|'remove', files, bytes, totalFiles, totalBytes }` (runWithProgress for deletes/imports). Emit 'count' (a treeSize walk) first, copy/remove through the fsutil helpers.
+- Long operations stream progress through the single import:progress slot as `{ phase: 'count'|'copy'|'remove', files, bytes, totalFiles, totalBytes }` (runWithProgress for deletes/imports). Emit 'count' (a treeSize walk) first, copy/remove through the fsutil helpers. An isolated hand-off has its own slot, handoff:progress (`{ phase: 'copy'|'done'|'error', name, bytes, totalBytes, notice }`), because it can start before the window exists: main.js gets the event first and, when `notice` is set (a copy above linuxrunner.STAGE_NOTICE_BYTES), puts the launcher window up so the renderer's popup can be seen; below that the copy is over before a window could paint. Copies of one file go through fsutil.copyFileProgress (streamed, throttled by progressGate, `.part` + rename).
 - CSS: reuse the existing variables/classes (.button, .field-label, .custom-select, form-card); spacing comes from --button-margin and flex gaps, not per-element magic numbers.
+- The blanket `transform: translateZ(0)` (crisper small glyphs) makes every element its own stacking context, so a select's own z-index cannot escape the wrapper it sits in: a list opened inside `.linux-only`, `.win-only` or an override row was painted UNDER the field label and textarea that follow it (measuring with `elementsFromPoint` over the open list returned the label). CustomSelect lifts the chain instead of the host — `lift()` adds `.select-lift` to every STATIC ancestor while the list is open, and `close()`/`closeAll()` take it off again; positioned ancestors are skipped, so the fixed modal overlay keeps stacking over every view on its own.
 
 ### Native Linux apps
 
@@ -83,9 +87,10 @@ Renderer never touches Node/Electron directly — everything goes through the `w
 - SESSION_MANAGER is dropped in the sandbox: the session socket sits in the private `/tmp`, so the pointer led nowhere (Qt: "Could not open network socket").
 - Imports normalise permissions (fsutil.chmodTree): owner `rwx`, `x` mirrored from `r` (0644 → 0755). Sources are archives, FAT sticks and read-only backups.
 - **Reset Linux config** on every prefix row removes exactly what PLWL seeded (DESKTOP_SEEDS, the pulse cookie, `home/.Xauthority`, `.seeded.json`) plus the folders that existed only for the seed, so the next start seeds clean. syncDesktopConfig can only follow a copy it can still prove is its own; the reset does not argue. App data (`data/`, `cache/`, `state/`, `config/<app>/`, the rest of `home/`) is never touched, and a running app from that prefix blocks it (the usual `inUse` guard).
-- The user's real `~` is deliberately invisible in the sandbox (HOME is bound straight to `{prefix}/linux_pfx/home`), so absolute paths an app wrote into its config before the import (Prism's instance `JavaPath`) do not resolve — that is what `isolation: 'off'` is for.
+- With HOME bound straight to `{prefix}/linux_pfx/home`, the user's real `~` is invisible to the app — one reason absolute paths an app wrote into its config before the import (Prism's instance `JavaPath`) do not resolve. `relaxed` does not change that shadowing, but it does make the real filesystem reachable through `FS_ROOT`/home/… — and `none` gives the app the real paths outright, which is what those two levels are for.
 - A clicked link belongs to the host desktop, so it leaves through `org.freedesktop.portal.OpenURI` — both routes, because two different things open a link. The `xdg-open` BINARY is replaced inside the sandbox (a written shim `--ro-bind` over `/usr/bin/xdg-open`, the host's own script parked at `/tmp/.plwl-host/xdg-open` as what the shim falls back to for anything that is not a URI): Qt execs it (measured — `QGenericUnixServices` picks `xdg-open` first, and reaches the portal itself only under `/.flatpak-info`/`SNAP`, which a bwrap profile does not have) and so does Electron. GIO resolves an URI IN-PROCESS, which no shim can reach: for that the prefix seeds `home/.plwl/open-url` (launcher-written, like the shim) plus a desktop entry and a `mimeapps.list` naming it the default for `x-scheme-handler/http|https` and `text/html`. Without the seed GIO falls back to the host's `/usr/share` list — measured: it offered `brave-origin.desktop`, and `gio open` answered "The specified location is not supported". Measured end to end (both backends): the portal launches the host's `helium.desktop` with the exact URI. `GIO_USE_PORTALS=1` was measured and REJECTED: it opened NOTHING and still reported success (GIO's portal path wants a sandbox marker this launcher does not fake), while on a machine WITHOUT a portal it fails hard (“Failed to create OpenURI proxy”). The whole wiring is therefore written only when a session bus and a portal are present (`portalReady`), and a KDE-native app resolving through KIO in-process (`kde-open`) stays uncovered — KDE ignores the seeded list (measured).
-- A file handed over (a shortcut's `--file %f`, a drop on it) is the ONE path the sandbox cannot see by itself, and all three reasons are real: a file out of the user's home is buried under the prefix home, one out of `/tmp` sits behind the private tmpfs, and the rest of the machine is read-only. `handedFileBinds` returns it for `--bind` at the same path, placed AFTER the app data binds so it wins over the home mounted there, and writable — the way Wine hands a file over as `Z:\…` and may save it (parity with the Wine side is the point: same shortcut, same outcome). Prefix data is skipped, being the app's own writable home already; a folder and a path that is gone are skipped too, since a missing bind source makes bwrap refuse the launch. The argv is untouched: `linuxPathFor` still passes the host path to the app. Only a *new* run gets the mount — a handoff into an app already running in its own namespace cannot, and the app reports that itself.
+- A file handed over (a shortcut's `--file %f`, a drop on it) is the one path the sandbox cannot see by itself: a file out of the user's home is buried under the prefix home, one out of `/tmp` sits behind the private tmpfs, and the rest of the machine is read-only. Per-file `--bind` (what 0.5.0 did) is the wrong tool: a mount cannot be added to a namespace that is ALREADY running, so a hand-off into a running app could never be served that way. `handedPathFor` instead names the document in the one shape the chosen level can reach, and the app is told nothing else: `none` → the real path; `relaxed` → `FS_ROOT` + the real path; `isolated` → a copy in `{prefix}/linux_pfx/home/plwl-handoff/<name>`, which is a live bind of the app's home, so it reaches a running app too (measured end to end in test/linux-e2e.js: both levels hand a document to a sandbox that is already up). Copies are one per name and refreshed on every open (the folder cannot grow), written through a `.part` name and renamed so nothing ever reads a half-written document, and the app's edits stay in the copy — that IS the level's promise. A handed path that is gone fails the hand-off instead of launching an app with no document.
+- `FS_ROOT` (`/tmp/plwl-fs-root`) is where relaxed mounts the host filesystem, and it has to live under the private `/tmp`: bubblewrap creates the mount point itself, and the root of a read-only root cannot be written to (measured on 0.12.0: `Can't create file /PLWL_FS_ROOT: Read-only file system`, for a `--dir` before the `--ro-bind / /` too). Measured also: through it the real `~` reads, a write lands on the real file, and a file created AFTER a sandboxed run started is visible inside it — that last one is what makes a hand-off into a running app possible at all.
 - Not built: a private or overlay `/etc` (`buildBwrapArgs` accepts `etcRoot`, nothing sets it; `--ro-bind / /` leaves `/etc` read-only, which is all we promise today), `--tmpfs /home` against OTHER users' homes (`hideHome` is plumbed, no UI) and `dataMode` — app data always lands in `{prefix}/linux_pfx`.
 - Measured, not assumed (Debian 13, kernel 6.12, `bwrap` 0.12.0): the functional probe passes here, no firejail/proot/fuse-overlayfs on the box, `/etc` is 16 MB and its `machine-id` is read-only even on the host.
 
@@ -131,12 +136,12 @@ node test/lansync-pending-links.test.js  # links to files created later, startup
 node test/lansync-consent.test.js        # accept / decline / timeout gate
 node test/lansync-token.test.js          # long-sync token expiry (sliding TTL)
 node test/bench-sync.js                  # timing: cold vs cached sync
-node test/linux-sandbox.test.js          # bwrap argv profile + auto/off/require choice
+node test/linux-sandbox.test.js          # bwrap argv profile + the four levels, handed paths, mode migration
 node test/linux-env.test.js              # redirected HOME/XDG_* for both backends
 node test/linux-import.test.js           # ELF/AppImage/.desktop detection + icons
 node test/linux-links.test.js            # link opening: shim binds + mime seed
 node test/linux-sync.test.js             # linux_pfx stays out of a sync
-node test/linux-e2e.js                   # REAL run: plain + bwrap (/etc read-only, home in prefix)
+node test/linux-e2e.js                   # REAL runs: plain, relaxed (+ its mount), isolated, hand-off into a running app
 npm start                                # click through the flow you touched
 
 # Repairing / testing a real instance (test/ scripts are gitignored helpers):