Fix Ventoy installs with UDF 1.50 and a media-locating Setup launch

README.md

@@ -43,6 +43,35 @@ Windows. Test your ISO in a VM before installing it.**
 
 ![Build settings with Turbo mode and optional image cleanup](docs/images/ui-build-settings.png)
 
+## Booting from Ventoy
+
+ISOs built here boot from Ventoy in its default (non-wimboot) mode — no Rufus,
+no extracted USB stick, no manual patching. If an older build stops at
+**"A media driver your computer needs is missing"**, the wording is misleading:
+it is not a missing disk driver, it means Setup never saw its installation
+media. Rebuild the ISO; nothing about the Ventoy stick needs to change.
+
+Ventoy does not extract a Windows ISO. It boots the ISO's own `boot.wim` and
+injects `vtoyjump.exe` so the ISO can be mounted as a virtual drive before
+`setup.exe` runs. Two builder behaviours broke that:
+
+| Change | Why it broke Ventoy |
+| --- | --- |
+| The WinPE launch chain forced to a fixed `X:\sources\setup.exe` (`Setup\CmdLine` in the scripts, `winpeshl.ini` in the app) | Setup takes the boot RAM disk as its media root, finds no `install.wim` beside it and stops. Core only. |
+| `oscdimg -udfver102` | UDF 1.02 cannot describe a file larger than 4 GB, so a trimmed `install.wim` is written with metadata that lean readers mis-parse. |
+
+Both are fixed: the stock WinPE launch chain is left alone, so the boot image's
+own `setup.exe` bootstrap locates the media before running that media's
+`sources\setup.exe`, and ISOs are built with `-udfver150`. A build also refuses
+to emit an ISO whose `sources\` has no usable `install.wim`/`install.esd`,
+because that failure looks identical to this one.
+
+If a rebuilt ISO still fails, press `Shift+F10` at the error and run `diskpart`,
+then `list volume`. No virtual DVD drive means `vtoyjump` never ran;
+`X:\Windows\System32\ventoy\vtoype.log` records why a mount failed. `Ctrl+W` at
+the Ventoy menu switches to wimboot mode, a different boot path. Also check that
+Ventoy is 1.1.07 or newer and that its data partition is NTFS rather than exFAT.
+
 ## More information
 
 [Usage, compatibility and build instructions](docs/usage.md) ·

docs/usage.md

@@ -63,9 +63,14 @@ The six-step wizard provides:
   acknowledgement before a build.
 - Core and Custom WinSxS/component-payload removals always use the legacy
   Windows installer, including on 24H2 and newer media. The private Setup
-  boot image starts `wpeinit.exe`, then its matching `sources\setup.exe`
-  (`setup_old.exe` when present), instead of the newer SetupHost workflow.
-  This is automatic, not a hardware-bypass option; no installer from a
+  boot image starts `wpeinit.exe`, then the boot image's own `setup.exe`
+  bootstrap, which locates the installation media and runs that media's
+  matching `sources\setup.exe` (`setup_old.exe` when present) instead of the
+  newer SetupHost workflow. Starting a fixed `X:\sources\setup.exe` instead
+  would make Setup treat the boot RAM disk as the media root and stop with
+  "A media driver your computer needs is missing" — including under Ventoy,
+  which mounts the ISO as a virtual drive only after its own WinPE hook has
+  run. This is automatic, not a hardware-bypass option; no installer from a
   different Windows release is downloaded. Media without the classic
   executable fails explicitly. A resumed Core job also receives this change
   even if its final installation image was already compressed.
@@ -94,6 +99,44 @@ The six-step wizard provides:
   state, verified saved progress for **Resume build**, an output SHA-256, a JSON
   report, and separate interrupted-workspace discard/recovery.
 
+## Booting from Ventoy
+
+Output ISOs boot from Ventoy in its default (non-wimboot) mode, for both Tiny11
+and Tiny11 Core. Ventoy does not extract a Windows ISO: it boots the ISO's own
+`boot.wim` and injects `vtoyjump.exe`, which mounts the ISO as a virtual drive
+before `setup.exe` runs. Setup only reads `sources\install.wim` after that
+mount, so anything that stops the hook from running, or that hides the media
+from Setup, surfaces as the same misleading message:
+
+> A media driver your computer needs is missing. This could be a DVD, USB, or Hard disk driver.
+
+That message is not about a driver. It means Setup never saw its installation
+media. Three build-time causes are handled:
+
+| Cause | Handling |
+| --- | --- |
+| The WinPE launch chain forced to a fixed `X:\sources\setup.exe` (`Setup\CmdLine` in the scripts, `winpeshl.ini` in the app) | The stock launch chain is left alone. The boot image's own `setup.exe` bootstrap locates the media and runs that media's `sources\setup.exe`. |
+| `oscdimg -udfver102` | ISOs are built with `-udfver150`. UDF 1.02 cannot describe a file larger than 4 GB, which a trimmed `install.wim` exceeds. |
+| A failed image export that still deleted the old image | The build refuses to create an ISO whose `sources\` has no usable `install.wim`/`install.esd`, and removes leftover `install2.wim`/`install2.esd`. |
+
+If a current ISO still stops at that message, press `Shift+F10` and run:
+
+```
+diskpart
+list volume
+type X:\Windows\System32\ventoy\vtoype.log
+```
+
+- **No virtual DVD drive in `list volume`** — `vtoyjump` never ran, so the
+  problem is the boot image patch rather than the ISO contents.
+- **`vtoype.log`** records what `vtoyjump` did and why a mount failed.
+- **`Ctrl+W`** at the Ventoy menu switches to wimboot mode, a different boot
+  path worth trying as a workaround.
+
+Also check that Ventoy is **1.1.07 or newer**, that its data partition is
+**NTFS** rather than exFAT, and that the ISO sits on the first, large Ventoy
+partition rather than the 32 MB `VTOYEFI` one.
+
 ## Turbo mode and smaller images
 
 The settings page has independent **Turbo mode**, **Remove redundant image

src/Tiny11Builder.Core/BuildEngine.Tail.cs

@@ -304,6 +304,7 @@ await s.Tracking.RunAsync("checkpoint:compressed", "Compress", "Save verified co
     private async Task CreateIsoAsync(BuildSession s, CancellationToken token)
     {
         s.Stage("Create ISO", "Creating a UEFI-bootable ISO using Microsoft's oscdimg.", token);
+        RequireInstallableMedia(s);
         if (File.Exists(s.TemporaryIso))
         {
             PathSafety.RejectReparsePoints(s.TemporaryIso);
@@ -313,12 +314,52 @@ private async Task CreateIsoAsync(BuildSession s, CancellationToken token)
         var efi = Path.Combine(s.Staging, s.EfiRelative);
         var boot = s.Image.Architecture == "x64" && File.Exists(bios) ?
             $"-bootdata:2#p0,e,b{bios}#pEF,e,b{efi}" : $"-bootdata:1#pEF,e,b{efi}";
+        // -u2 is the ISO9660 + Joliet + UDF layout Microsoft's own retail media uses; ISO9660 alone cannot hold a
+        // file larger than 4 GB, so the UDF layer is what carries install.wim. -udfver150 rather than the default
+        // UDF 1.02: 1.02 cannot describe a single file larger than 4 GB, and a trimmed install.wim routinely exceeds
+        // that. oscdimg still writes such a file, but the on-disc metadata ends up in a form lenient readers accept
+        // and lean ones mis-parse. This is a large-file robustness fix; it is not what stopped Ventoy booting.
         var isoResult = await runner.RunAsync(s.Recipe.OscdimgPath,
-            ["-m", "-o", "-u2", "-udfver102", boot, s.Staging, s.TemporaryIso], s.Log, token, finishOnCancellation: false).ConfigureAwait(false);
+            ["-m", "-o", "-u2", "-udfver150", boot, s.Staging, s.TemporaryIso], s.Log, token, finishOnCancellation: false).ConfigureAwait(false);
         if (isoResult.ExitCode != 0 || !File.Exists(s.TemporaryIso) || new FileInfo(s.TemporaryIso).Length < 34816)
             throw new IOException($"oscdimg did not produce an ISO (exit {isoResult.ExitCode}). {isoResult.Output}");
     }
 
+    /// <summary>
+    /// Refuses to publish media that Windows Setup cannot install from. Every failure below looks identical to the
+    /// user - "A media driver your computer needs is missing" - while the real cause is an ISO with no installation
+    /// image, so the build has to stop here and name it instead of shipping a disc that cannot install.
+    /// </summary>
+    private static void RequireInstallableMedia(BuildSession s)
+    {
+        var sources = Path.Combine(s.Staging, "sources");
+        // An export interrupted between writing and renaming can leave a second image behind. Setup picks the first
+        // image it finds in sources\, so a stale partial one would silently win over the finished one.
+        foreach (var stray in new[] { "install2.wim", "install2.esd" })
+        {
+            var file = Path.Combine(sources, stray);
+            if (!File.Exists(file)) continue;
+            PathSafety.RejectReparsePoints(file);
+            File.Delete(file);
+            s.Warn($"Removed a leftover {stray} from the sources folder; Setup would have detected it as the installation image.");
+        }
+        var images = new[] { "install.wim", "install.esd" }.Select(name => Path.Combine(sources, name))
+            .Where(File.Exists).ToArray();
+        if (images.Length == 0)
+            throw new IOException("The media has no sources\\install.wim or install.esd, so Windows Setup would stop " +
+                "with \"A media driver your computer needs is missing\" even though no driver is involved. The image " +
+                "export step failed; no ISO was created.");
+        // The export stage already proved each image is complete (DISM lists its single edition and its WIM header and
+        // footer parse), so only the size is worth reporting here.
+        foreach (var image in images)
+            s.Log($"Install image {Path.GetFileName(image)}: {new FileInfo(image).Length / (1024d * 1024d):0} MB");
+        // Ventoy only applies its Windows boot patch to an ISO it recognises as standard installation media; without
+        // these it is treated as a generic image and never mounts itself as the drive Setup reads from.
+        foreach (var required in new[] { @"setup.exe", @"sources\boot.wim", @"boot\bcd", @"boot\boot.sdi" })
+            if (!File.Exists(Path.Combine(s.Staging, required)))
+                s.Log($"Ventoy compatibility: the staged media has no {required}, so Ventoy will not recognise this ISO as Windows media.");
+    }
+
     private static async Task<BuildResult> VerifyAndPublishAsync(BuildSession s, CancellationToken token)
     {
         s.Stage("Verify output", "Hashing the completed ISO and publishing it without overwriting existing files.", token);

src/Tiny11Builder.Core/SetupInstaller.cs

@@ -24,16 +24,37 @@ internal static void ApplyLegacy(string mount, Action<string> log)
         ImageFileAccess.ValidateFile(program);
         if (new FileInfo(program).Length == 0)
             throw new InvalidDataException("The legacy installer in the Windows Setup image is empty.");
+
+        // Start the boot image's own setup bootstrap, and let it find the media, instead of starting a fixed path
+        // inside the boot RAM disk.
+        //
+        // boot.wim is loaded to X:, but the installation media is not there. From a USB stick it is another drive;
+        // under Ventoy it is not a drive at all until vtoyjump.exe has mounted the ISO as a virtual one, and Ventoy
+        // runs that hook from the same WinPE launch chain this file configures. Setup started as
+        // X:\sources\setup.exe takes the directory it was loaded from as the media root, finds no install.wim beside
+        // it, and stops with "A media driver your computer needs is missing" - which reads like a missing storage
+        // driver but only means Setup never saw its media. setup.exe at the root of the boot image is the stock
+        // bootstrap: it locates the media and then runs that media's matching sources\setup.exe, which is the classic
+        // installer this method exists to select. Only when the image ships no bootstrap does the fixed path remain.
+        var launch = "%SYSTEMDRIVE%\\" + executable;
+        var bootstrap = Path.Combine(mount, "setup.exe");
+        if (File.Exists(bootstrap))
+        {
+            ImageFileAccess.ValidateFile(bootstrap);
+            if (new FileInfo(bootstrap).Length == 0)
+                throw new InvalidDataException("The Setup bootstrap in the Windows Setup image is empty.");
+            launch = @"%SYSTEMDRIVE%\setup.exe";
+        }
         var path = Path.Combine(mount, @"Windows\System32\winpeshl.ini");
         PathSafety.RejectReparsePoints(Path.GetDirectoryName(path)!);
         if (File.Exists(path))
         {
             using var privileges = new ImageOperations.PrivilegeScope();
             ImageFileAccess.DeleteEntry(path);
         }
-        var content = "[LaunchApps]\r\n%SYSTEMROOT%\\System32\\wpeinit.exe\r\n%SYSTEMDRIVE%\\" + executable + "\r\n";
+        var content = "[LaunchApps]\r\n%SYSTEMROOT%\\System32\\wpeinit.exe\r\n" + launch + "\r\n";
         File.WriteAllText(path, content, Encoding.ASCII);
         if (File.ReadAllText(path) != content) throw new IOException("The legacy Windows Setup startup configuration could not be verified.");
-        log($"Legacy installer enabled: %SYSTEMDRIVE%\\{executable}. Required by Core/component-store removals.");
+        log($"Legacy installer enabled: {launch}. Required by Core/component-store removals.");
     }
 }

tests/Tiny11Builder.Core.Tests/SetupInstallerTests.cs

@@ -47,6 +47,23 @@ public void Legacy_startup_initializes_PE_then_runs_the_matching_classic_install
         Assert.Throws<InvalidDataException>(() => SetupInstaller.ApplyLegacy(fixture.Root, messages.Add));
     }
 
+    [Fact]
+    public void Legacy_startup_uses_the_media_bootstrap_so_Setup_finds_its_media_outside_the_ram_disk()
+    {
+        using var fixture = new BuildFixture();
+        var mount = NativeTests.CreateOwnedMount(fixture.Root);
+        Directory.CreateDirectory(Path.Combine(mount, "sources"));
+        File.WriteAllText(Path.Combine(mount, @"sources\setup.exe"), "same-build classic binary");
+        File.WriteAllText(Path.Combine(mount, "setup.exe"), "stock media bootstrap");
+        var messages = new List<string>();
+        SetupInstaller.ApplyLegacy(mount, messages.Add);
+        var ini = File.ReadAllText(Path.Combine(mount, @"Windows\System32\winpeshl.ini"));
+        // A fixed X:\sources\setup.exe makes Setup treat the RAM disk as the media root, which is empty under
+        // Ventoy until vtoyjump mounts the ISO. The bootstrap locates the real media first.
+        Assert.Equal("[LaunchApps]\r\n%SYSTEMROOT%\\System32\\wpeinit.exe\r\n%SYSTEMDRIVE%\\setup.exe\r\n", ini);
+        Assert.Single(messages);
+    }
+
     [Fact]
     public void Missing_classic_installer_is_a_loud_failure_not_a_new_installer_fallback()
     {