Update README.md

MSVC/WinSDK/WDK/DXSDK payloads run into the hundreds of MB to several
GB, so a dropped connection or a retry after a transient error used to
mean throwing away everything already fetched and starting over from
byte 0. Track progress in a dest+".part" file and resume it via an
HTTP Range request, falling back to a full restart when the server
doesn't honor Range (200 instead of 206) or the local part is stale
(416).

README.md

@@ -1,4 +1,4 @@
-# vintner
+# Vintner
 
 [![CI](https://github.com/Cheviiot/vintner/actions/workflows/ci.yml/badge.svg)](https://github.com/Cheviiot/vintner/actions/workflows/ci.yml)
 [![Release](https://img.shields.io/github/v/release/Cheviiot/vintner)](https://github.com/Cheviiot/vintner/releases/latest)
@@ -8,8 +8,9 @@ vintner cross-compiles with the real MSVC toolchain on Linux, using Wine.
 One Go binary drops in as `cl`, `link`, `lib`, `rc`, `midl`, `mc`, `mt`,
 `dumpbin`, `msbuild`, `nmake`, `ml`, `ml64`, `armasm`, `armasm64`, plus
 `cmd`/`findstr` shims, so once installed you invoke the real Microsoft
-tools exactly like on Windows. It handles full MSBuild projects, and with
+tools exactly like on Windows. It handles full MSBuild projects, with
-`--with-wdk`, real KMDF/UMDF Windows drivers.
+`--with-wdk` real KMDF/UMDF Windows drivers, and with `--with-dxsdk` the
+real D3DX9 headers/libs.
 
 Inspired by [mstorsjo/msvc-wine](https://github.com/mstorsjo/msvc-wine)'s
 approach: download the real MSVC/WinSDK, wrap the compiler under Wine.
@@ -20,7 +21,11 @@ approach: download the real MSVC/WinSDK, wrap the compiler under Wine.
 - [Installation](#installation)
 - [Quick start](#quick-start)
 - [Commands](#commands)
+- [Invoking tools without PATH](#invoking-tools-without-path)
+- [Diagnosing problems (vintner doctor)](#diagnosing-problems-vintner-doctor)
 - [Building drivers (WDK)](#building-drivers-wdk)
+- [Building against D3DX9 (DirectX SDK)](#building-against-d3dx9-directx-sdk)
+- [Automated/scripted builds](#automatedscripted-builds)
 - [Language](#language)
 - [Shell completion](#shell-completion)
 - [Using clang-cl/lld-link instead of Wine](#using-clang-cllld-link-instead-of-wine)
@@ -42,9 +47,9 @@ depending on the name it's invoked as.
   then runs the real `.exe` under `wine`/`wine64`, and rewrites `z:\...`
   paths back to Unix paths in the output, so your build system's error
   parsing keeps working.
-- As `vintner`: it exposes the `download`, `install`, `env`, `version`
+- As `vintner`: it exposes the `download`, `install`, `env`, `version`,
-  and `completion` subcommands below (short aliases: `dl`, `i`, `e`, `v`;
+  `doctor` and `completion` subcommands below (short aliases: `dl`, `i`,
-  `help`/`h` prints usage).
+  `e`, `v`; `help`/`h` prints usage).
 
 ## Installation
 
@@ -74,11 +79,13 @@ as package dependencies.
 - `msitools` (`msiextract`) — unpacks the `.msi` payloads MSVC/WinSDK ship as.
 - `git` — applies the compatibility patches bundled with `download` (see
   [Compatibility patches](#compatibility-patches)).
+- `cabextract` — only needed for `download --with-dxsdk` (see
+  [Building against D3DX9](#building-against-d3dx9-directx-sdk)).
 
 On ALT Linux:
 
 ```bash
-pkcon install wine msitools git
+pkcon install wine msitools git cabextract
 ```
 
 ## Quick start
@@ -97,6 +104,9 @@ export PATH=~/.vintner/bin/x64:$PATH
 cl /nologo /EHsc hello.cpp
 ```
 
+Don't want to touch PATH? Skip step 3 and run tools through vintner
+directly instead - see [Invoking tools without PATH](#invoking-tools-without-path).
+
 ## Commands
 
 ```
@@ -104,6 +114,7 @@ vintner download (dl) --accept-license [--dest <dir>] [options]   fetch and unpa
 vintner install (i) [dir]                                         wire up wrappers for a downloaded MSVC
 vintner env (e) --bin <dir>/bin/<arch>                            print INCLUDE/LIB for native clang-cl/lld-link use
 vintner version (v)                                               print the version
+vintner doctor                                                    check wine/toolchain setup
 vintner help (h)                                                  print usage
 vintner completion bash|zsh                                       print a shell completion script
 ```
@@ -112,12 +123,13 @@ vintner completion bash|zsh                                       print a shell
 
 `download`'s main options: `--msvc-version`, `--sdk-version`,
 `--architecture` (repeatable: `x86`/`x64`/`arm`/`arm64`/`host`),
-`--host-arch`, `--only-host`, `--with-wdk` (see below), `--ignore`
+`--host-arch`, `--only-host`, `--with-wdk` (see below), `--with-dxsdk`
-(repeatable), `--only-download`, `--only-unpack`, `--keep-unpack`,
+(see below), `--ignore` (repeatable), `--only-download`, `--only-unpack`,
-`--skip-patch`, `--cache`, `--language`, `--include-optional`,
+`--keep-unpack`, `--skip-patch`, `--cache`, `--language`,
-`--skip-recommended`, `--major`, `--preview`, `--manifest`,
+`--include-optional`, `--skip-recommended`, `--major`, `--preview`,
-`--list-workloads`, `--list-components`, `--print-deps-tree`. Run
+`--manifest`, `--list-workloads`, `--list-components`,
-`vintner download -h` for the full list with descriptions.
+`--print-deps-tree`. Run `vintner download -h` for the full list with
+descriptions.
 
 `--list-workloads`/`--list-components` print every workload/component id
 and its human-readable title from the fetched manifest, then exit
@@ -126,6 +138,38 @@ package id or through `--with-*`. `--print-deps-tree` prints the
 dependency tree of whatever would actually be selected — honoring every
 other flag — without downloading anything.
 
+## Invoking tools without PATH
+
+`cl`, `link`, `msbuild`, and the rest also work as `vintner <tool>
+[args...]`, with no need to add `<dest>/bin/<arch>` to `PATH` or rely on
+the symlinks `install` sets up there:
+
+```bash
+vintner cl /nologo /EHsc hello.cpp
+vintner msbuild MyProject.sln
+```
+
+Resolves the toolchain to use from `VINTNER_BIN` if set (same meaning as
+`env --bin`: point it at a `<dest>/bin/<arch>` directory directly — useful
+for a non-default `--dest`, or to pick a specific architecture when more
+than one is installed), otherwise defaults to
+`~/.vintner/bin/<host-arch>`, the layout a plain `vintner download &&
+vintner install` with no `--dest` override produces.
+
+## Diagnosing problems (vintner doctor)
+
+```bash
+vintner doctor
+```
+
+Checks the things vintner actually needs at runtime — that `wine`/`wine64`
+is on `PATH` and actually runs, that `msitools`/`cabextract` are present,
+and that every installed `<dest>/bin/<arch>` toolchain (or the one
+`VINTNER_BIN` points at) has its MSVC/SDK/MSBuild directories in place —
+and prints a pass/fail checklist. Exits non-zero if anything failed.
+Useful before filing a bug, or after a `download`/`install` that seemed to
+finish but left tools failing in confusing ways.
+
 ## Building drivers (WDK)
 
 `--with-wdk` also fetches the Windows Driver Kit: headers, import libs,
@@ -143,6 +187,42 @@ work under Wine. Tested against a real sample driver from
 Only x64 and arm64 targets have a WDK package upstream; there's no x86 or
 arm one.
 
+## Building against D3DX9 (DirectX SDK)
+
+`--with-dxsdk` fetches the DirectX SDK (June 2010) — the last standalone
+release of D3DX9/10/11, XInput and XAudio2, dropped from the Windows SDK
+entirely once D3DX was deprecated. It unpacks the real headers and x86/x64
+import libs (`d3dx9.h`/`d3dx9.lib` included) to `<dest>/DXSDK`.
+
+```bash
+vintner download --accept-license --with-dxsdk
+```
+
+Point your project's `IncludePath`/`LibraryPath` at
+`<dest>/DXSDK/Include` and `<dest>/DXSDK/Lib/x86` or `<dest>/DXSDK/Lib/x64`.
+Requires `cabextract` on `PATH` (the installer is a self-extracting CAB
+archive).
+
+## Automated/scripted builds
+
+Every tool invocation runs unbounded by default, same as the real thing on
+Windows. Set `VINTNER_TIMEOUT` (a `time.ParseDuration` string, e.g. `30m`,
+`2h`) to have vintner kill and fail a build that runs longer than that
+instead of hanging forever - meant for CI and other unattended callers, not
+interactive use. This guards against one confirmed failure mode: an
+MSBuild node-reuse worker (`/nodeReuse:true` is MSBuild's own default) can
+survive its parent process under Wine and, if a prior build was
+interrupted mid-compile, come back wedged - reused by the next `msbuild`
+call and failing every subsequent build with a confusing, unrelated-looking
+error, indefinitely, until it's killed by hand. vintner already forces
+`/nodeReuse:false` on every `msbuild` invocation to prevent this in the
+first place; `VINTNER_TIMEOUT` is the backstop for whatever else might
+wedge under Wine that isn't MSBuild-specific.
+
+```bash
+VINTNER_TIMEOUT=30m msbuild MyProject.sln
+```
+
 ## Language
 
 CLI text (usage, progress lines, prompts) defaults to English. Set
@@ -157,6 +237,8 @@ Error text from internal packages stays in English regardless.
 
 ## Shell completion
 
+Already set up if you installed via Nivora. Otherwise:
+
 ```bash
 source <(vintner completion bash)   # or add to ~/.bashrc
 source <(vintner completion zsh)    # or add to ~/.zshrc

assets/vendor/toolrelay.cpp

@@ -79,8 +79,16 @@ HANDLE MakeKillOnCloseJob() {
 }
 
 bool IsMtExe(const wchar_t *path) {
-  const wchar_t *name = wcsrchr(path, L'\\');
+  // vintner passes toolExePath straight through from Go's filepath.Join,
-  name = name ? name + 1 : path;
+  // which uses forward slashes even for a path that's about to be handed
+  // to a native Windows process - so the separator here isn't reliably
+  // '\\'. Check both; using whichever comes later in the string covers a
+  // mixed-separator path too.
+  const wchar_t *back = wcsrchr(path, L'\\');
+  const wchar_t *fwd = wcsrchr(path, L'/');
+  const wchar_t *sep = back;
+  if (fwd && (!sep || fwd > sep)) sep = fwd;
+  const wchar_t *name = sep ? sep + 1 : path;
   return _wcsicmp(name, L"mt.exe") == 0;
 }
 

cmd/vintner/completion.go

@@ -1,6 +1,11 @@
 package main
 
-import "fmt"
+import (
+	"fmt"
+	"strings"
+
+	"github.com/Cheviiot/vintner/internal/wrapper"
+)
 
 // runCompletion prints a shell completion script for shell ("bash" or
 // "zsh") to stdout, meant to be sourced directly:
@@ -11,6 +16,11 @@ import "fmt"
 // The flag lists below are hand-maintained alongside download.go/env.go's
 // flag.FlagSet definitions rather than generated from them - there's no
 // reflection-friendly registry to walk, and the flag set rarely changes.
+// The tool name list isn't hand-maintained, though (see wrapper.ToolNames):
+// a hand-copied one already went stale once already for a flag
+// (--with-dxsdk missing from here after being added to download.go), and a
+// list of every wrapped tool has more entries and changes for the same
+// reasons the flag lists do, so it's worth generating for real.
 func runCompletion(args []string) int {
 	if len(args) != 1 {
 		fmt.Println("usage: vintner completion bash|zsh")
@@ -18,10 +28,10 @@ func runCompletion(args []string) int {
 	}
 	switch args[0] {
 	case "bash":
-		fmt.Print(bashCompletionScript)
+		fmt.Print(bashCompletionScript())
 		return 0
 	case "zsh":
-		fmt.Print(zshCompletionScript)
+		fmt.Print(zshCompletionScript())
 		return 0
 	default:
 		fmt.Printf("vintner completion: unsupported shell %q (want bash or zsh)\n", args[0])
@@ -33,9 +43,16 @@ const downloadFlags = "--dest --cache --major --preview --manifest --accept-lice
 	"--msvc-version --sdk-version --host-arch --only-host --language " +
 	"--include-optional --skip-recommended --only-download --only-unpack " +
 	"--keep-unpack --skip-patch --list-workloads --list-components " +
-	"--print-deps-tree --with-wdk --architecture --ignore -h --help"
+	"--print-deps-tree --with-wdk --with-dxsdk --architecture --ignore -h --help"
 
-var bashCompletionScript = `# vintner bash completion - eval "$(vintner completion bash)"
+// subcommandNames lists vintner's own management subcommands (long form
+// plus every short alias) - unlike the wrapped-tool names, these really are
+// fixed enough to hand-maintain: adding one is rare and always touches
+// main.go's dispatch switch right next to this file anyway.
+const subcommandNames = "download dl install i env e version v doctor help h completion"
+
+func bashCompletionScript() string {
+	return `# vintner bash completion - eval "$(vintner completion bash)"
 _vintner_complete() {
     local cur cmd
     COMPREPLY=()
@@ -43,7 +60,7 @@ _vintner_complete() {
     cmd="${COMP_WORDS[1]}"
 
     if [ "$COMP_CWORD" -eq 1 ]; then
-        COMPREPLY=($(compgen -W "download dl install i env e version v help h completion" -- "$cur"))
+        COMPREPLY=($(compgen -W "` + subcommandNames + ` ` + strings.Join(wrapper.ToolNames(), " ") + `" -- "$cur"))
         return 0
     fi
 
@@ -65,8 +82,15 @@ _vintner_complete() {
 }
 complete -F _vintner_complete vintner
 `
+}
 
-var zshCompletionScript = `#compdef vintner
+func zshCompletionScript() string {
+	var toolEntries strings.Builder
+	for _, name := range wrapper.ToolNames() {
+		fmt.Fprintf(&toolEntries, "        %q\n", name+":run this tool directly, e.g. \"vintner "+name+" ...\"")
+	}
+
+	return `#compdef vintner
 # vintner zsh completion - source <(vintner completion zsh)
 
 _vintner() {
@@ -80,10 +104,11 @@ _vintner() {
         'e:alias for env'
         'version:print the version'
         'v:alias for version'
+        'doctor:check wine/toolchain setup'
         'help:print usage'
         'h:alias for help'
         'completion:print a shell completion script'
-    )
+` + toolEntries.String() + `    )
 
     if (( CURRENT == 2 )); then
         _describe 'command' subcommands
@@ -115,6 +140,7 @@ _vintner() {
                 '--list-components[list available components and exit]'
                 '--print-deps-tree[print the dependency tree and exit]'
                 '--with-wdk[also fetch the Windows Driver Kit]'
+                '--with-dxsdk[also fetch the DirectX SDK]'
                 '--architecture[target architecture]:arch:(x86 x64 arm arm64 host)'
                 '--ignore[package id to skip]:package id:'
                 '-h[show help]'
@@ -138,3 +164,4 @@ _vintner() {
 
 _vintner "$@"
 `
+}

cmd/vintner/completion_test.go

@@ -4,6 +4,8 @@ import (
 	"os/exec"
 	"strings"
 	"testing"
+
+	"github.com/Cheviiot/vintner/internal/wrapper"
 )
 
 // TestCompletionScriptsAreSyntacticallyValid catches the easy way to break
@@ -15,8 +17,8 @@ func TestCompletionScriptsAreSyntacticallyValid(t *testing.T) {
 		shell  string
 		script string
 	}{
-		{"bash", bashCompletionScript},
+		{"bash", bashCompletionScript()},
-		{"zsh", zshCompletionScript},
+		{"zsh", zshCompletionScript()},
 	} {
 		t.Run(tc.shell, func(t *testing.T) {
 			if _, err := exec.LookPath(tc.shell); err != nil {
@@ -31,6 +33,24 @@ func TestCompletionScriptsAreSyntacticallyValid(t *testing.T) {
 	}
 }
 
+// TestCompletionScriptsListEveryTool guards against the exact staleness bug
+// found and fixed alongside this test: a hand-copied tool/flag list here
+// drifting from the real set in internal/wrapper (or download.go's flags)
+// as tools/flags get added. Every current tool name must appear in both
+// generated scripts.
+func TestCompletionScriptsListEveryTool(t *testing.T) {
+	bash := bashCompletionScript()
+	zsh := zshCompletionScript()
+	for _, name := range wrapper.ToolNames() {
+		if !strings.Contains(bash, name) {
+			t.Errorf("bash completion script doesn't mention tool %q", name)
+		}
+		if !strings.Contains(zsh, name+":") {
+			t.Errorf("zsh completion script doesn't mention tool %q", name)
+		}
+	}
+}
+
 func TestRunCompletionUnknownShell(t *testing.T) {
 	if code := runCompletion([]string{"fish"}); code != 1 {
 		t.Errorf("runCompletion([\"fish\"]) = %d, want 1", code)

cmd/vintner/doctor.go

@@ -0,0 +1,176 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"time"
+
+	"github.com/Cheviiot/vintner/internal/i18n"
+	"github.com/Cheviiot/vintner/internal/wineenv"
+)
+
+// runDoctor checks the pieces vintner actually needs at runtime - wine
+// itself, the optional extraction tools download needs, and every
+// installed <dest>/bin/<arch> toolchain's on-disk layout - and prints a
+// pass/fail checklist. The point is surfacing a broken setup as a short,
+// readable report instead of a wine-specific error buried deep inside a
+// build (see internal/wineenv.FindWine's own error, which this reuses).
+func runDoctor(args []string) int {
+	if len(args) > 0 && (args[0] == "-h" || args[0] == "--help") {
+		fmt.Fprintln(os.Stderr, i18n.T("doctor.usage"))
+		return 1
+	}
+
+	d := &doctorReport{}
+	d.checkWine()
+	d.checkExtractionTools()
+	d.checkToolchains()
+
+	if d.failed {
+		fmt.Println(i18n.T("doctor.summary_fail"))
+		return 1
+	}
+	fmt.Println(i18n.T("doctor.summary_ok"))
+	return 0
+}
+
+type doctorReport struct {
+	failed bool
+}
+
+func (d *doctorReport) ok(format string, args ...any) {
+	fmt.Printf("  [ok]   "+format+"\n", args...)
+}
+
+func (d *doctorReport) warn(format string, args ...any) {
+	fmt.Printf("  [warn] "+format+"\n", args...)
+}
+
+func (d *doctorReport) fail(format string, args ...any) {
+	fmt.Printf("  [FAIL] "+format+"\n", args...)
+	d.failed = true
+}
+
+func (d *doctorReport) checkWine() {
+	fmt.Println(i18n.T("doctor.section_wine"))
+
+	wineBin, err := wineenv.FindWine()
+	if err != nil {
+		d.fail("%s", err)
+		return
+	}
+	d.ok("found: %s", wineBin)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	out, err := exec.CommandContext(ctx, wineBin, "--version").Output()
+	if err != nil {
+		d.fail("%s --version failed: %v", wineBin, err)
+		return
+	}
+	d.ok("runs: %s", trimNewline(string(out)))
+}
+
+func (d *doctorReport) checkExtractionTools() {
+	fmt.Println(i18n.T("doctor.section_extract"))
+
+	if _, err := exec.LookPath("msiextract"); err != nil {
+		d.warn(i18n.T("doctor.msitools_missing"))
+	} else {
+		d.ok("msitools: found (needed by `vintner download`)")
+	}
+
+	if _, err := exec.LookPath("cabextract"); err != nil {
+		d.warn(i18n.T("doctor.cabextract_missing"))
+	} else {
+		d.ok("cabextract: found (needed by --with-wdk/--with-dxsdk)")
+	}
+}
+
+func (d *doctorReport) checkToolchains() {
+	fmt.Println(i18n.T("doctor.section_toolchain"))
+
+	if binDir := os.Getenv("VINTNER_BIN"); binDir != "" {
+		d.checkToolchainAt(binDir, "VINTNER_BIN="+binDir)
+		return
+	}
+
+	def, err := defaultToolchainDir()
+	if err != nil {
+		d.fail("%s", err)
+		return
+	}
+	destBin := filepath.Join(def, "bin")
+	archDirs := installedArchDirs(destBin)
+	if len(archDirs) == 0 {
+		d.fail(i18n.T("doctor.no_toolchain", destBin))
+		return
+	}
+	for _, arch := range archDirs {
+		d.checkToolchainAt(filepath.Join(destBin, arch), arch)
+	}
+}
+
+// installedArchDirs returns the subdirectories of destBin that carry their
+// own env.json, i.e. every architecture `vintner install` actually set up
+// (there can be more than one - e.g. x86 and x64 side by side).
+func installedArchDirs(destBin string) []string {
+	entries, err := os.ReadDir(destBin)
+	if err != nil {
+		return nil
+	}
+	var dirs []string
+	for _, e := range entries {
+		if !e.IsDir() {
+			continue
+		}
+		if _, err := os.Stat(filepath.Join(destBin, e.Name(), wineenv.ConfigFileName)); err == nil {
+			dirs = append(dirs, e.Name())
+		}
+	}
+	return dirs
+}
+
+func (d *doctorReport) checkToolchainAt(binDir, label string) {
+	cfg, err := wineenv.Load(binDir)
+	if err != nil {
+		d.fail("%s: %s", label, err)
+		return
+	}
+	baseUnix, err := wineenv.FindBaseUnix(binDir)
+	if err != nil {
+		d.fail("%s: %s", label, err)
+		return
+	}
+	d.ok("%s: MSVC %s, SDK %s, root %s", label, cfg.MSVCVer, cfg.SDKVer, baseUnix)
+
+	paths := wineenv.NewPaths(cfg, baseUnix)
+	for _, dir := range []struct{ name, path string }{
+		{"MSVC bin", paths.BinDir},
+		{"SDK bin", paths.SDKBinDir},
+		{"MSBuild bin", paths.MSBuildBinDir},
+	} {
+		if fi, err := os.Stat(dir.path); err != nil || !fi.IsDir() {
+			d.fail("%s: %s missing: %s", label, dir.name, dir.path)
+		} else {
+			d.ok("%s: %s: %s", label, dir.name, dir.path)
+		}
+	}
+
+	relay := filepath.Join(baseUnix, "bin", "toolrelay.exe")
+	if fi, err := os.Stat(relay); err != nil || fi.IsDir() {
+		d.warn("%s: toolrelay.exe not built (mt.exe's CMake exit-code translation won't apply; re-run `vintner install` to retry)", label)
+	} else {
+		d.ok("%s: toolrelay.exe: %s", label, relay)
+	}
+}
+
+func trimNewline(s string) string {
+	for len(s) > 0 && (s[len(s)-1] == '\n' || s[len(s)-1] == '\r') {
+		s = s[:len(s)-1]
+	}
+	return s
+}

cmd/vintner/doctor_test.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/Cheviiot/vintner/internal/wineenv"
+)
+
+func TestRunDoctorUsage(t *testing.T) {
+	for _, flag := range []string{"-h", "--help"} {
+		if code := runDoctor([]string{flag}); code != 1 {
+			t.Errorf("runDoctor([%q]) = %d, want 1", flag, code)
+		}
+	}
+}
+
+func TestDoctorReportOkWarnFail(t *testing.T) {
+	d := &doctorReport{}
+	d.ok("fine")
+	d.warn("meh")
+	if d.failed {
+		t.Fatal("ok/warn must not mark the report as failed")
+	}
+	d.fail("broken")
+	if !d.failed {
+		t.Fatal("fail must mark the report as failed")
+	}
+}
+
+func TestInstalledArchDirsFindsOnlyDirsWithEnvJSON(t *testing.T) {
+	destBin := t.TempDir()
+	for _, dir := range []string{"x64", "x86", "not-a-toolchain"} {
+		if err := os.MkdirAll(filepath.Join(destBin, dir), 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	for _, dir := range []string{"x64", "x86"} {
+		if err := os.WriteFile(filepath.Join(destBin, dir, wineenv.ConfigFileName), []byte("{}"), 0o644); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	got := installedArchDirs(destBin)
+	want := map[string]bool{"x64": true, "x86": true}
+	if len(got) != len(want) {
+		t.Fatalf("installedArchDirs = %v, want exactly %v", got, want)
+	}
+	for _, arch := range got {
+		if !want[arch] {
+			t.Errorf("installedArchDirs returned unexpected entry %q", arch)
+		}
+	}
+}
+
+func TestInstalledArchDirsMissingDir(t *testing.T) {
+	if got := installedArchDirs(filepath.Join(t.TempDir(), "does-not-exist")); got != nil {
+		t.Errorf("installedArchDirs on a missing dir = %v, want nil", got)
+	}
+}
+
+func TestCheckToolchainAtMissingEnvJSON(t *testing.T) {
+	d := &doctorReport{}
+	d.checkToolchainAt(t.TempDir(), "test")
+	if !d.failed {
+		t.Error("checkToolchainAt against a dir with no env.json should fail the report")
+	}
+}
+
+func TestTrimNewline(t *testing.T) {
+	cases := map[string]string{
+		"wine-9.0\n":   "wine-9.0",
+		"wine-9.0\r\n": "wine-9.0",
+		"wine-9.0":     "wine-9.0",
+		"":             "",
+	}
+	for in, want := range cases {
+		if got := trimNewline(in); got != want {
+			t.Errorf("trimNewline(%q) = %q, want %q", in, got, want)
+		}
+	}
+}

cmd/vintner/download.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/Cheviiot/vintner/internal/download"
 	"github.com/Cheviiot/vintner/internal/i18n"
+	"github.com/Cheviiot/vintner/internal/lock"
 )
 
 func runDownload(args []string) int {
@@ -35,6 +36,7 @@ func runDownload(args []string) int {
 	listComponents := fs.Bool("list-components", false, "list available components from the manifest and exit, without downloading anything")
 	printDepsTree := fs.Bool("print-deps-tree", false, "print the dependency tree of the selected packages and exit, without downloading anything")
 	withWDK := fs.Bool("with-wdk", false, "also fetch and install the Windows Driver Kit (headers, libs and MSBuild driver PlatformToolsets, for building KMDF/UMDF drivers)")
+	withDXSDK := fs.Bool("with-dxsdk", false, "also fetch and install the DirectX SDK (June 2010): real D3DX9/10/11, XInput and XAudio2 headers and import libs, dropped from the modern Windows SDK")
 	var archsFlag stringList
 	fs.Var(&archsFlag, "architecture", "target architecture to include (x86, x64, arm, arm64, host); repeatable")
 	var ignoreFlag stringList
@@ -176,6 +178,12 @@ func runDownload(args []string) int {
 		fmt.Fprintln(os.Stderr, "vintner download:", err)
 		return 1
 	}
+	unlock, err := lock.Acquire(destAbs)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "vintner download:", err)
+		return 1
+	}
+	defer unlock()
 
 	unpack := destAbs
 	if !*onlyUnpack {
@@ -219,6 +227,13 @@ func runDownload(args []string) int {
 		}
 	}
 
+	if *withDXSDK && !*onlyUnpack {
+		if err := downloadDXSDK(cache, destAbs); err != nil {
+			fmt.Fprintln(os.Stderr, "vintner download:", err)
+			return 1
+		}
+	}
+
 	fmt.Println(i18n.T("download.done", destAbs))
 	return 0
 }
@@ -255,6 +270,18 @@ func downloadWDK(opts *download.Options, selected []*download.Package, cache, de
 	return nil
 }
 
+// downloadDXSDK fetches and unpacks the DirectX SDK (June 2010) into
+// destAbs/DXSDK. See internal/download/dxsdk.go for why this is a separate
+// download path from the rest of ExpandSelection/FetchPayloads/Unpack.
+func downloadDXSDK(cache, destAbs string) error {
+	dxsdkDir, err := download.DownloadDXSDK(cache, destAbs)
+	if err != nil {
+		return err
+	}
+	fmt.Print(i18n.T("download.dxsdk_installed", dxsdkDir))
+	return nil
+}
+
 func contains(list []string, v string) bool {
 	for _, s := range list {
 		if s == v {

cmd/vintner/main.go

@@ -1,9 +1,9 @@
 // Command vintner cross compiles with the real MSVC toolchain on Linux
 // via Wine. It's a multi-call binary that behaves as `cl`, `link`, `lib`,
 // `rc`, `midl`, `mt`, `dumpbin`, `msbuild`, etc. when invoked under one of
-// those names (via symlinks set up by `vintner install`), and
+// those names (via symlinks set up by `vintner install`) or as
-// otherwise exposes the `download`/`install`/`env`/`version` management
+// `vintner <tool> ...` directly (see runTool), and otherwise exposes the
-// subcommands.
+// `download`/`install`/`env`/`version` management subcommands.
 package main
 
 import (
@@ -24,11 +24,8 @@ func main() {
 	base := filepath.Base(os.Args[0])
 	name := strings.TrimSuffix(strings.ToLower(base), ".exe")
 
-	if _, ok := wrapper.Tools[name]; ok {
+	if wrapper.IsTool(name) {
-		os.Exit(wrapper.Run(name, os.Args[1:]))
+		os.Exit(wrapper.Run(name, os.Args[1:], ""))
-	}
-	if name == "cmd" || name == "findstr" {
-		os.Exit(wrapper.Run(name, os.Args[1:]))
 	}
 
 	os.Exit(runCLI(os.Args[1:]))
@@ -40,6 +37,10 @@ func runCLI(args []string) int {
 		return 1
 	}
 
+	if wrapper.IsTool(args[0]) {
+		return runTool(args[0], args[1:])
+	}
+
 	switch args[0] {
 	case "download", "dl":
 		return runDownload(args[1:])
@@ -49,8 +50,10 @@ func runCLI(args []string) int {
 		return runEnv(args[1:])
 	case "completion":
 		return runCompletion(args[1:])
+	case "doctor":
+		return runDoctor(args[1:])
 	case "version", "v", "--version":
-		fmt.Println("vintner " + version)
+		fmt.Println(versionString())
 		return 0
 	case "-h", "--help", "help", "h":
 		printUsage()

cmd/vintner/tool.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/Cheviiot/vintner/internal/wrapper"
+)
+
+// runTool dispatches `vintner <tool> [args...]` (cl, link, msbuild, ...)
+// directly, without needing <dest>/bin/<arch> on PATH or a same-directory
+// symlink pointing back at this binary.
+//
+// Resolves which toolchain bin dir to use from VINTNER_BIN if set (same
+// meaning as `env --bin`: point it directly at a <dest>/bin/<arch>
+// directory - useful for a non-default --dest, or to pick a specific
+// architecture when more than one is installed), else defaults to
+// <defaultToolchainDir>/bin/<hostArch>, the layout a plain `vintner
+// download && vintner install` with no --dest override produces.
+func runTool(tool string, args []string) int {
+	binDir := os.Getenv("VINTNER_BIN")
+	if binDir == "" {
+		def, err := defaultToolchainDir()
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "vintner:", err)
+			return 1
+		}
+		binDir = filepath.Join(def, "bin", detectHostArch())
+	}
+	if fi, err := os.Stat(binDir); err != nil || !fi.IsDir() {
+		fmt.Fprintf(os.Stderr,
+			"vintner: no installed toolchain found at %s\n"+
+				"Run `vintner download --accept-license && vintner install` first, "+
+				"or set VINTNER_BIN to an existing <dest>/bin/<arch> directory.\n",
+			binDir)
+		return 1
+	}
+	return wrapper.Run(tool, args, binDir)
+}

cmd/vintner/tool_test.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+func TestRunToolReportsMissingToolchain(t *testing.T) {
+	t.Setenv("VINTNER_BIN", filepath.Join(t.TempDir(), "does-not-exist"))
+	if code := runTool("cl", nil); code != 1 {
+		t.Errorf("runTool with a nonexistent VINTNER_BIN = %d, want 1", code)
+	}
+}
+
+func TestRunToolUsesVINTNERBinOverDefault(t *testing.T) {
+	// A directory that exists but has no env.json - past the "toolchain
+	// found at all" check, into wrapper.Run's own (already-tested)
+	// env.json-loading error path. Confirms VINTNER_BIN is actually being
+	// read and passed through, without needing a full fake toolchain.
+	t.Setenv("VINTNER_BIN", t.TempDir())
+	if code := runTool("cl", nil); code != 1 {
+		t.Errorf("runTool with an empty VINTNER_BIN dir = %d, want 1 (from the missing env.json)", code)
+	}
+}

cmd/vintner/version.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"fmt"
+	"runtime/debug"
+)
+
+// versionString renders "vintner <version>" plus, when available, the git
+// commit and build time Go's toolchain embeds automatically (since Go
+// 1.18, `go build` stamps vcs.revision/vcs.time/vcs.modified into the
+// binary on its own - no -ldflags needed for this part, so it works the
+// same whether the binary came from CI or a plain local `go build`).
+// Knowing the exact commit a reported bug was built from, not just the
+// X.Y.Z tag, is the point: two builds of the same tag could still differ
+// if the tag was ever moved, or if someone built from an uncommitted tree.
+//
+// Note for anyone testing this: `go build` stamps vcs.* build settings,
+// but `go test` binaries don't get them - there's no environment where a
+// `go test` run can exercise the revision-formatting branch below, hence
+// formatVersion is split out and tested directly instead.
+func versionString() string {
+	revision, buildTime, dirty := "", "", false
+	if info, ok := debug.ReadBuildInfo(); ok {
+		for _, s := range info.Settings {
+			switch s.Key {
+			case "vcs.revision":
+				revision = s.Value
+			case "vcs.time":
+				buildTime = s.Value
+			case "vcs.modified":
+				dirty = s.Value == "true"
+			}
+		}
+	}
+	return formatVersion(version, revision, buildTime, dirty)
+}
+
+// formatVersion is the pure part of versionString: given a revision (full
+// git SHA, may be empty), it's shortened to 12 chars and marked "-dirty" if
+// the build tree had uncommitted changes.
+func formatVersion(ver, revision, buildTime string, dirty bool) string {
+	v := "vintner " + ver
+	if revision == "" {
+		return v
+	}
+	if len(revision) > 12 {
+		revision = revision[:12]
+	}
+	if dirty {
+		revision += "-dirty"
+	}
+	if buildTime != "" {
+		return fmt.Sprintf("%s (%s, %s)", v, revision, buildTime)
+	}
+	return fmt.Sprintf("%s (%s)", v, revision)
+}

cmd/vintner/version_test.go

@@ -0,0 +1,46 @@
+package main
+
+import "testing"
+
+func TestFormatVersion(t *testing.T) {
+	for _, tc := range []struct {
+		name                     string
+		ver, revision, buildTime string
+		dirty                    bool
+		want                     string
+	}{
+		{
+			name: "no VCS info at all",
+			ver:  "dev",
+			want: "vintner dev",
+		},
+		{
+			name:      "clean build with full info",
+			ver:       "0.3.0",
+			revision:  "6186837fd23616335ba8aff830801692a756799c",
+			buildTime: "2026-07-25T01:33:41Z",
+			want:      "vintner 0.3.0 (6186837fd236, 2026-07-25T01:33:41Z)",
+		},
+		{
+			name:     "dirty tree",
+			ver:      "0.3.0",
+			revision: "6186837fd23616335ba8aff830801692a756799c",
+			dirty:    true,
+			want:     "vintner 0.3.0 (6186837fd236-dirty)",
+		},
+		{
+			name:     "short revision left untouched",
+			ver:      "dev",
+			revision: "abc123",
+			want:     "vintner dev (abc123)",
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			got := formatVersion(tc.ver, tc.revision, tc.buildTime, tc.dirty)
+			if got != tc.want {
+				t.Errorf("formatVersion(%q, %q, %q, %v) = %q, want %q",
+					tc.ver, tc.revision, tc.buildTime, tc.dirty, got, tc.want)
+			}
+		})
+	}
+}

internal/download/dxsdk.go

@@ -0,0 +1,94 @@
+package download
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+)
+
+// The DirectX SDK (June 2010) is the last standalone release of D3DX9 (and
+// D3DX10/11, XInput, XAudio2, ...). Microsoft never carried D3DX forward
+// into the Windows 10/11 SDK - it's deprecated in favor of D3DCompiler/
+// WICTextureLoader/DirectXTex, but plenty of legacy code (this included)
+// still links against the real d3dx9.h/d3dx9.lib. Like the WDK (see
+// wdk.go), it isn't part of the VS installer manifest or any package feed
+// vsman knows about, so this is a separate, self-contained download path
+// outside ExpandSelection/FetchPayloads/UnpackSelectedPackages.
+//
+// The installer is a self-extracting PE with an appended CAB archive.
+// cabextract (already a vintner prerequisite - see runMsiExtract's sibling
+// extractWindowsSDKPackage) unpacks it directly, without needing Wine or a
+// separate archive tool. Its -F/--filter flag (repeatable) restricts
+// extraction to the Include and Lib subtrees actually needed for building -
+// about 21MB out of the installer's 1.2GB uncompressed payload.
+
+const dxsdkURL = "https://download.microsoft.com/download/A/E/7/AE743F1F-632B-4809-87A9-AA1BB3458E31/DXSDK_Jun10.exe"
+
+// dxsdkSHA256 pins the exact installer build this code was written against
+// (verified by fully extracting it with both cabextract and 7z and cross
+// checking the file lists) - the June 2010 DirectX SDK is a frozen legacy
+// artifact Microsoft is not going to rebuild. A var, not a const, so tests
+// can point it at a small fake payload instead of the real 600MB installer.
+var dxsdkSHA256 = "705271dc83bfee54d9b94e028426e288d5f070784b7446d164f48ecfbb2a02cb"
+
+// DownloadDXSDK fetches (or reuses a cached copy of) the DirectX SDK (June
+// 2010) installer into cacheDir, then unpacks its Include and Lib trees -
+// headers and x86/x64 import libs for D3DX9/10/11, XInput, XAudio2, and the
+// rest - into destDir/DXSDK. Returns that directory.
+func DownloadDXSDK(cacheDir, destDir string) (string, error) {
+	if _, err := exec.LookPath("cabextract"); err != nil {
+		return "", fmt.Errorf("cabextract not found in PATH (install the cabextract package): %w", err)
+	}
+
+	cacheFile := filepath.Join(cacheDir, "DXSDK_Jun10.exe")
+	if !isFile(cacheFile) {
+		fmt.Println("Downloading DirectX SDK (June 2010)")
+		if err := httpDownloadFile(dxsdkURL, cacheFile); err != nil {
+			return "", fmt.Errorf("downloading DirectX SDK: %w", err)
+		}
+	} else {
+		fmt.Println("Using existing file", filepath.Base(cacheFile))
+	}
+	sum, err := sha256File(cacheFile)
+	if err != nil {
+		return "", err
+	}
+	if !equalFoldHex(sum, dxsdkSHA256) {
+		return "", fmt.Errorf("incorrect hash for downloaded file %s, aborting", filepath.Base(cacheFile))
+	}
+
+	scratch, err := os.MkdirTemp(destDir, "dxsdk-unpack-")
+	if err != nil {
+		return "", err
+	}
+	defer os.RemoveAll(scratch)
+
+	if err := runCabextract(cacheFile, scratch, "DXSDK/Include/*", "DXSDK/Lib/*"); err != nil {
+		return "", fmt.Errorf("extracting DirectX SDK: %w", err)
+	}
+
+	dxsdkDir := filepath.Join(destDir, "DXSDK")
+	if err := combineDirTrees(filepath.Join(scratch, "DXSDK"), dxsdkDir); err != nil {
+		return "", fmt.Errorf("moving DirectX SDK content into place: %w", err)
+	}
+	return dxsdkDir, nil
+}
+
+// runCabextract extracts srcFile into destDir, restricted to entries
+// matching any of patterns (cabextract's -F, repeatable, glob-matched
+// against the full in-archive path).
+func runCabextract(srcFile, destDir string, patterns ...string) error {
+	if err := os.MkdirAll(destDir, 0o755); err != nil {
+		return err
+	}
+	args := []string{"-q", "-d", destDir}
+	for _, p := range patterns {
+		args = append(args, "-F", p)
+	}
+	args = append(args, srcFile)
+	cmd := exec.Command("cabextract", args...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}

internal/download/dxsdk_test.go

@@ -0,0 +1,111 @@
+package download
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+	"testing"
+)
+
+// withFakeCabextract prepends a directory containing a fake "cabextract"
+// script to PATH, so tests can exercise runCabextract/DownloadDXSDK without
+// the real tool (or a real DXSDK installer) present. The fake script
+// records the arguments it was invoked with to argsFile and creates an
+// empty DXSDK/Include and DXSDK/Lib under whatever -d directory it was
+// given, mimicking a successful (if empty) extraction.
+func withFakeCabextract(t *testing.T, argsFile string) {
+	t.Helper()
+	if runtime.GOOS == "windows" {
+		t.Skip("fake cabextract script requires a POSIX shell")
+	}
+	bin := t.TempDir()
+	script := `#!/bin/sh
+echo "$@" > "` + argsFile + `"
+dest=""
+prev=""
+for a in "$@"; do
+  if [ "$prev" = "-d" ]; then
+    dest="$a"
+  fi
+  prev="$a"
+done
+mkdir -p "$dest/DXSDK/Include" "$dest/DXSDK/Lib"
+`
+	path := filepath.Join(bin, "cabextract")
+	if err := os.WriteFile(path, []byte(script), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv("PATH", bin+":"+os.Getenv("PATH"))
+}
+
+func TestRunCabextractPassesFilterArgs(t *testing.T) {
+	dest := t.TempDir()
+	argsFile := filepath.Join(t.TempDir(), "args")
+	withFakeCabextract(t, argsFile)
+
+	src := filepath.Join(t.TempDir(), "installer.exe")
+	writeFile(t, src, "fake-installer-bytes")
+
+	if err := runCabextract(src, dest, "DXSDK/Include/*", "DXSDK/Lib/*"); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := os.ReadFile(argsFile)
+	if err != nil {
+		t.Fatalf("expected the fake cabextract to have run: %v", err)
+	}
+	want := "-q -d " + dest + " -F DXSDK/Include/* -F DXSDK/Lib/* " + src + "\n"
+	if string(got) != want {
+		t.Errorf("cabextract args = %q, want %q", got, want)
+	}
+}
+
+func TestDownloadDXSDKReusesCachedFileAndRejectsHashMismatch(t *testing.T) {
+	argsFile := filepath.Join(t.TempDir(), "args")
+	withFakeCabextract(t, argsFile)
+
+	cacheDir := t.TempDir()
+	destDir := t.TempDir()
+	writeFile(t, filepath.Join(cacheDir, "DXSDK_Jun10.exe"), "not the real installer")
+
+	_, err := DownloadDXSDK(cacheDir, destDir)
+	if err == nil {
+		t.Fatal("expected an error for a cached file that doesn't match dxsdkSHA256")
+	}
+	if _, statErr := os.Stat(argsFile); statErr == nil {
+		t.Error("cabextract should not have run before the hash was verified")
+	}
+}
+
+func TestDownloadDXSDKMovesExtractedContentIntoPlace(t *testing.T) {
+	argsFile := filepath.Join(t.TempDir(), "args")
+	withFakeCabextract(t, argsFile)
+
+	cacheDir := t.TempDir()
+	destDir := t.TempDir()
+	cacheFile := filepath.Join(cacheDir, "DXSDK_Jun10.exe")
+	writeFile(t, cacheFile, "fake-installer-bytes-for-hash-test")
+
+	// Patch the expected hash to match our fake cached file, since we can't
+	// (and shouldn't) fetch or embed the real 600MB installer in a test.
+	sum, err := sha256File(cacheFile)
+	if err != nil {
+		t.Fatal(err)
+	}
+	restore := dxsdkSHA256
+	dxsdkSHA256 = sum
+	defer func() { dxsdkSHA256 = restore }()
+
+	dxsdkDir, err := DownloadDXSDK(cacheDir, destDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if dxsdkDir != filepath.Join(destDir, "DXSDK") {
+		t.Errorf("DownloadDXSDK returned %q, want %q", dxsdkDir, filepath.Join(destDir, "DXSDK"))
+	}
+	for _, sub := range []string{"Include", "Lib"} {
+		if !isDir(filepath.Join(dxsdkDir, sub)) {
+			t.Errorf("expected %s/%s to exist after extraction", dxsdkDir, sub)
+		}
+	}
+}

internal/download/extract_test.go

@@ -0,0 +1,152 @@
+package download
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func writeFile(t *testing.T, path, content string) {
+	t.Helper()
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestCombineDirTreesNonexistentSrcIsNoop(t *testing.T) {
+	dest := t.TempDir()
+	if err := combineDirTrees(filepath.Join(t.TempDir(), "does-not-exist"), dest); err != nil {
+		t.Fatalf("combineDirTrees with a nonexistent src returned an error: %v", err)
+	}
+}
+
+func TestCombineDirTreesRenamesWholesaleWhenDestMissing(t *testing.T) {
+	root := t.TempDir()
+	src := filepath.Join(root, "src")
+	dest := filepath.Join(root, "nested", "dest")
+	writeFile(t, filepath.Join(src, "file.txt"), "hello")
+
+	if err := combineDirTrees(src, dest); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.ReadFile(filepath.Join(dest, "file.txt")); err != nil {
+		t.Errorf("expected %s/file.txt to exist after combine: %v", dest, err)
+	}
+	if isDir(src) {
+		t.Error("src should have been moved (renamed), not copied")
+	}
+}
+
+func TestCombineDirTreesMergesNewSubdir(t *testing.T) {
+	root := t.TempDir()
+	src, dest := filepath.Join(root, "src"), filepath.Join(root, "dest")
+	writeFile(t, filepath.Join(src, "NewDir", "a.txt"), "a")
+	writeFile(t, filepath.Join(dest, "Existing.txt"), "keep me")
+
+	if err := combineDirTrees(src, dest); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.ReadFile(filepath.Join(dest, "NewDir", "a.txt")); err != nil {
+		t.Errorf("expected merged NewDir/a.txt: %v", err)
+	}
+	if _, err := os.ReadFile(filepath.Join(dest, "Existing.txt")); err != nil {
+		t.Errorf("pre-existing dest file was lost: %v", err)
+	}
+}
+
+func TestCombineDirTreesMergesCaseInsensitiveCollision(t *testing.T) {
+	root := t.TempDir()
+	src, dest := filepath.Join(root, "src"), filepath.Join(root, "dest")
+	// src has "Include" (capital I), dest already has "include" (lowercase) -
+	// this is exactly the MSVC/WinSDK casing-inconsistency scenario the
+	// function's doc comment describes.
+	writeFile(t, filepath.Join(src, "Include", "new.h"), "new")
+	writeFile(t, filepath.Join(dest, "include", "old.h"), "old")
+
+	if err := combineDirTrees(src, dest); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.ReadFile(filepath.Join(dest, "include", "new.h")); err != nil {
+		t.Errorf("new.h should have merged into the existing lowercase 'include' dir: %v", err)
+	}
+	if _, err := os.ReadFile(filepath.Join(dest, "include", "old.h")); err != nil {
+		t.Errorf("old.h should still be there: %v", err)
+	}
+	if isDir(filepath.Join(dest, "Include")) {
+		t.Error("a separate capital-I 'Include' dir should not have been created")
+	}
+}
+
+func TestCombineDirTreesRecursesIntoExactNameMatch(t *testing.T) {
+	root := t.TempDir()
+	src, dest := filepath.Join(root, "src"), filepath.Join(root, "dest")
+	writeFile(t, filepath.Join(src, "lib", "x64", "new.lib"), "new")
+	writeFile(t, filepath.Join(dest, "lib", "x64", "old.lib"), "old")
+
+	if err := combineDirTrees(src, dest); err != nil {
+		t.Fatal(err)
+	}
+	for _, f := range []string{"new.lib", "old.lib"} {
+		if _, err := os.ReadFile(filepath.Join(dest, "lib", "x64", f)); err != nil {
+			t.Errorf("expected lib/x64/%s to survive the merge: %v", f, err)
+		}
+	}
+}
+
+func TestCopyRedirectedAssembliesNoConfigIsNoop(t *testing.T) {
+	dir := t.TempDir()
+	app := filepath.Join(dir, "MSBuild.exe")
+	if err := CopyRedirectedAssemblies(app); err != nil {
+		t.Fatalf("with no .config file present, expected no error, got: %v", err)
+	}
+}
+
+func TestCopyRedirectedAssembliesCopiesReferencedDLL(t *testing.T) {
+	dir := t.TempDir()
+	app := filepath.Join(dir, "MSBuild.exe")
+	writeFile(t, app+".config", `<?xml version="1.0"?>
+<configuration>
+  <runtime>
+    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
+      <dependentAssembly>
+        <codeBase version="1.0.0.0" href="amd64\Some.Assembly.dll"/>
+      </dependentAssembly>
+    </assemblyBinding>
+  </runtime>
+</configuration>`)
+	writeFile(t, filepath.Join(dir, "amd64", "Some.Assembly.dll"), "binary-content")
+
+	if err := CopyRedirectedAssemblies(app); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := os.ReadFile(filepath.Join(dir, "Some.Assembly.dll"))
+	if err != nil {
+		t.Fatalf("expected Some.Assembly.dll copied next to MSBuild.exe: %v", err)
+	}
+	if string(got) != "binary-content" {
+		t.Errorf("copied file content = %q, want %q", got, "binary-content")
+	}
+}
+
+func TestCopyRedirectedAssembliesSkipsMissingTarget(t *testing.T) {
+	dir := t.TempDir()
+	app := filepath.Join(dir, "MSBuild.exe")
+	writeFile(t, app+".config", `<?xml version="1.0"?>
+<configuration>
+  <runtime>
+    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
+      <dependentAssembly>
+        <codeBase href="nowhere\Missing.dll"/>
+      </dependentAssembly>
+    </assemblyBinding>
+  </runtime>
+</configuration>`)
+
+	if err := CopyRedirectedAssemblies(app); err != nil {
+		t.Fatalf("a redirect pointing at a nonexistent file should be silently skipped, got: %v", err)
+	}
+}

internal/download/fetch.go

@@ -149,27 +149,63 @@ func tryDownloadPayload(payload Payload, dest, fileID string, allowHashMismatch
 
 var downloadHTTPClient = &http.Client{Timeout: 30 * time.Minute}
 
+// httpDownloadFile downloads url to dest via a dest+".part" temp file,
+// resuming from wherever a previous attempt left off if one exists - MSVC/
+// WinSDK/WDK/DXSDK payloads run into the hundreds of MB to multiple GB, so
+// restarting an interrupted download from byte 0 (a dropped connection, a
+// retry after this same function returned an error) wastes real time and
+// bandwidth on a flaky connection. Requests a byte Range starting at the
+// existing .part file's size, if any; a server that doesn't honor Range
+// (responds 200 instead of 206) gets treated as sending the whole file
+// again from byte 0, so the .part is truncated and started over rather
+// than getting byte-0 content appended onto existing bytes.
 func httpDownloadFile(url, dest string) error {
-	resp, err := downloadHTTPClient.Get(url)
+	tmp := dest + ".part"
+	var offset int64
+	if fi, err := os.Stat(tmp); err == nil {
+		offset = fi.Size()
+	}
+
+	req, err := http.NewRequest(http.MethodGet, url, nil)
+	if err != nil {
+		return err
+	}
+	if offset > 0 {
+		req.Header.Set("Range", fmt.Sprintf("bytes=%d-", offset))
+	}
+	resp, err := downloadHTTPClient.Do(req)
 	if err != nil {
 		return err
 	}
 	defer resp.Body.Close()
-	if resp.StatusCode != http.StatusOK {
+
+	var out *os.File
+	switch resp.StatusCode {
+	case http.StatusOK:
+		// No partial-content support (or nothing to resume from): the body
+		// is the whole file from byte 0.
+		out, err = os.Create(tmp)
+	case http.StatusPartialContent:
+		out, err = os.OpenFile(tmp, os.O_WRONLY|os.O_APPEND, 0o644)
+	case http.StatusRequestedRangeNotSatisfiable:
+		// Our .part is already >= the real file size - stale or corrupt.
+		// Discard it; the next retry starts clean with no Range header.
+		os.Remove(tmp)
+		return fmt.Errorf("GET %s: range not satisfiable, discarding partial download and retrying from scratch", url)
+	default:
 		return fmt.Errorf("GET %s: %s", url, resp.Status)
 	}
-	tmp := dest + ".part"
-	out, err := os.Create(tmp)
 	if err != nil {
 		return err
 	}
+
 	if _, err := io.Copy(out, resp.Body); err != nil {
 		out.Close()
-		os.Remove(tmp)
+		// Deliberately not removing tmp here: whatever bytes made it to
+		// disk are exactly what the next attempt should resume from.
 		return err
 	}
 	if err := out.Close(); err != nil {
-		os.Remove(tmp)
 		return err
 	}
 	return os.Rename(tmp, dest)

internal/download/fetch_resume_test.go

@@ -0,0 +1,173 @@
+package download
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+func TestHTTPDownloadFileFullDownload(t *testing.T) {
+	const body = "the quick brown fox jumps over the lazy dog"
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprint(w, body)
+	}))
+	defer srv.Close()
+
+	dest := filepath.Join(t.TempDir(), "out")
+	if err := httpDownloadFile(srv.URL, dest); err != nil {
+		t.Fatal(err)
+	}
+	got, err := os.ReadFile(dest)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != body {
+		t.Errorf("downloaded content = %q, want %q", got, body)
+	}
+}
+
+// rangeServer serves a fixed body and honors byte-range requests, exactly
+// like a real payload host (GitHub Releases, nuget.org, etc.) would.
+func rangeServer(body string) *httptest.Server {
+	return httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		rng := r.Header.Get("Range")
+		if rng == "" {
+			w.WriteHeader(http.StatusOK)
+			fmt.Fprint(w, body)
+			return
+		}
+		var start int
+		if _, err := fmt.Sscanf(rng, "bytes=%d-", &start); err != nil || start < 0 || start > len(body) {
+			w.WriteHeader(http.StatusRequestedRangeNotSatisfiable)
+			return
+		}
+		w.Header().Set("Content-Range", "bytes "+strconv.Itoa(start)+"-"+strconv.Itoa(len(body)-1)+"/"+strconv.Itoa(len(body)))
+		w.WriteHeader(http.StatusPartialContent)
+		fmt.Fprint(w, body[start:])
+	}))
+}
+
+func TestHTTPDownloadFileResumesFromExistingPart(t *testing.T) {
+	const body = "the quick brown fox jumps over the lazy dog"
+	srv := rangeServer(body)
+	defer srv.Close()
+
+	dest := filepath.Join(t.TempDir(), "out")
+	partial := body[:10]
+	if err := os.WriteFile(dest+".part", []byte(partial), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := httpDownloadFile(srv.URL, dest); err != nil {
+		t.Fatal(err)
+	}
+	got, err := os.ReadFile(dest)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != body {
+		t.Errorf("resumed download content = %q, want %q (partial %q should have been continued, not duplicated or lost)", got, body, partial)
+	}
+}
+
+func TestHTTPDownloadFileRestartsWhenServerIgnoresRange(t *testing.T) {
+	const body = "the quick brown fox jumps over the lazy dog"
+	// Always answers 200 with the full body, regardless of Range - some
+	// servers/CDNs genuinely don't support partial content.
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprint(w, body)
+	}))
+	defer srv.Close()
+
+	dest := filepath.Join(t.TempDir(), "out")
+	// A stale/bogus .part that must NOT end up prepended to the real
+	// content - if httpDownloadFile appended instead of truncating here,
+	// the result would start with this garbage.
+	if err := os.WriteFile(dest+".part", []byte("GARBAGE-FROM-A-STALE-ATTEMPT"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := httpDownloadFile(srv.URL, dest); err != nil {
+		t.Fatal(err)
+	}
+	got, err := os.ReadFile(dest)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != body {
+		t.Errorf("content = %q, want exactly %q (no leftover garbage prepended)", got, body)
+	}
+}
+
+func TestHTTPDownloadFileKeepsPartOnMidTransferFailure(t *testing.T) {
+	const fullBody = "0123456789"
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprint(w, fullBody[:5])
+		if f, ok := w.(http.Flusher); ok {
+			f.Flush()
+		}
+		// Simulate a dropped connection partway through by closing the
+		// underlying connection abruptly instead of finishing the body.
+		hj, ok := w.(http.Hijacker)
+		if !ok {
+			return
+		}
+		conn, _, err := hj.Hijack()
+		if err == nil {
+			conn.Close()
+		}
+	}))
+	defer srv.Close()
+
+	dest := filepath.Join(t.TempDir(), "out")
+	err := httpDownloadFile(srv.URL, dest)
+	if err == nil {
+		t.Fatal("expected an error from the truncated connection")
+	}
+
+	partial, err := os.ReadFile(dest + ".part")
+	if err != nil {
+		t.Fatalf("expected the .part file with the bytes received so far to survive a failed download: %v", err)
+	}
+	if !strings.HasPrefix(fullBody, string(partial)) || len(partial) == 0 {
+		t.Errorf(".part content = %q, want a non-empty prefix of %q", partial, fullBody)
+	}
+}
+
+func TestHTTPDownloadFileRangeNotSatisfiableDiscardsPart(t *testing.T) {
+	const body = "short"
+	srv := rangeServer(body)
+	defer srv.Close()
+
+	dest := filepath.Join(t.TempDir(), "out")
+	// .part is already longer than the real file - triggers 416 from
+	// rangeServer's own bounds check.
+	if err := os.WriteFile(dest+".part", []byte("this partial file is way too long"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := httpDownloadFile(srv.URL, dest); err == nil {
+		t.Fatal("expected an error on the first (416) attempt")
+	}
+	if _, err := os.Stat(dest + ".part"); !os.IsNotExist(err) {
+		t.Error("expected the stale .part to be discarded after a 416 response")
+	}
+
+	// The retry (a fresh caller, no Range header since .part is gone) should
+	// now succeed cleanly.
+	if err := httpDownloadFile(srv.URL, dest); err != nil {
+		t.Fatalf("retry after discarding the stale .part failed: %v", err)
+	}
+	got, err := os.ReadFile(dest)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != body {
+		t.Errorf("content = %q, want %q", got, body)
+	}
+}

internal/download/fetch_test.go

@@ -0,0 +1,59 @@
+package download
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+func TestRetryBackoff(t *testing.T) {
+	for _, tc := range []struct {
+		attempt int
+		want    time.Duration
+	}{
+		{1, 1 * time.Second},
+		{2, 2 * time.Second},
+		{3, 4 * time.Second},
+		{4, 8 * time.Second},
+		{5, 10 * time.Second}, // capped
+		{10, 10 * time.Second},
+	} {
+		if got := retryBackoff(tc.attempt); got != tc.want {
+			t.Errorf("retryBackoff(%d) = %v, want %v", tc.attempt, got, tc.want)
+		}
+	}
+}
+
+func TestSHA256File(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "f")
+	if err := os.WriteFile(path, []byte("hello"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	got, err := sha256File(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// echo -n hello | sha256sum
+	want := "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"
+	if got != want {
+		t.Errorf("sha256File(hello) = %q, want %q", got, want)
+	}
+}
+
+func TestEqualFoldHex(t *testing.T) {
+	for _, tc := range []struct {
+		a, b string
+		want bool
+	}{
+		{"ABCDEF", "abcdef", true},
+		{"abc123", "ABC123", true},
+		{"abc123", "abc124", false},
+		{"abc", "abcd", false},
+		{"", "", true},
+	} {
+		if got := equalFoldHex(tc.a, tc.b); got != tc.want {
+			t.Errorf("equalFoldHex(%q, %q) = %v, want %v", tc.a, tc.b, got, tc.want)
+		}
+	}
+}

internal/download/manifest_test.go

@@ -0,0 +1,134 @@
+package download
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestPayloadName(t *testing.T) {
+	for _, tc := range []struct {
+		fileName string
+		want     string
+	}{
+		{"payload.msi", "payload.msi"},
+		{"folder/payload.msi", "payload.msi"},
+		{`folder\payload.msi`, "payload.msi"},
+		{`a\b/c\payload.msi`, "payload.msi"},
+		{"", ""},
+	} {
+		p := Payload{FileName: tc.fileName}
+		if got := p.Name(); got != tc.want {
+			t.Errorf("Payload{FileName: %q}.Name() = %q, want %q", tc.fileName, got, tc.want)
+		}
+	}
+}
+
+func TestPackageKey(t *testing.T) {
+	for _, tc := range []struct {
+		name string
+		p    Package
+		want string
+	}{
+		{"id only", Package{ID: "Foo"}, "Foo"},
+		{"id+version", Package{ID: "Foo", Version: "1.0"}, "Foo-1.0"},
+		{
+			"id+version+all arches",
+			Package{ID: "Foo", Version: "1.0", Chip: "x64", MachineArch: "x86", ProductArch: "neutral"},
+			"Foo-1.0-chip.x64-machineArch.x86-productArch.neutral",
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := tc.p.Key(); got != tc.want {
+				t.Errorf("Key() = %q, want %q", got, tc.want)
+			}
+		})
+	}
+}
+
+func TestPackageLocalized(t *testing.T) {
+	noResources := Package{}
+	if got := noResources.Localized("en"); got != nil {
+		t.Errorf("Localized() on a package with no LocalizedResources = %v, want nil", got)
+	}
+
+	p := Package{LocalizedResources: []LocalizedResource{
+		{Language: "de-DE", Title: "Deutsch"},
+		{Language: "en-US", Title: "English"},
+		{Language: "ru-RU", Title: "Русский"},
+	}}
+
+	for _, tc := range []struct {
+		lang      string
+		wantTitle string
+	}{
+		{"ru", "Русский"},
+		{"ru-RU", "Русский"},
+		{"en", "English"},
+		{"", "English"},   // "" defaults to "en"
+		{"fr", "English"}, // no fr variant, falls back to the en-* one
+	} {
+		t.Run("lang="+tc.lang, func(t *testing.T) {
+			got := p.Localized(tc.lang)
+			if got == nil {
+				t.Fatalf("Localized(%q) = nil", tc.lang)
+			}
+			if got.Title != tc.wantTitle {
+				t.Errorf("Localized(%q).Title = %q, want %q", tc.lang, got.Title, tc.wantTitle)
+			}
+		})
+	}
+}
+
+func TestPackageSizes(t *testing.T) {
+	p := Package{
+		InstallSizes: map[string]int64{"x86": 100, "x64": 200},
+		Payloads:     []Payload{{Size: 10}, {Size: 20}, {Size: 30}},
+	}
+	if got := p.InstalledSize(); got != 300 {
+		t.Errorf("InstalledSize() = %d, want 300", got)
+	}
+	if got := p.DownloadSize(); got != 60 {
+		t.Errorf("DownloadSize() = %d, want 60", got)
+	}
+}
+
+func TestPackageDependenciesNormalizesBothShapes(t *testing.T) {
+	p := Package{DependenciesRaw: map[string]json.RawMessage{
+		"Bare.Version":    json.RawMessage(`"1.0"`),
+		"Full.Object":     json.RawMessage(`{"version":"2.0","type":"Optional","id":"Real.Target"}`),
+		"Recommended.Dep": json.RawMessage(`{"version":"3.0","type":"Recommended"}`),
+	}}
+	deps := p.Dependencies()
+
+	if d := deps["Bare.Version"]; d.Version != "1.0" || d.TargetID != "" || d.Type != "" {
+		t.Errorf("Bare.Version = %+v, want Version=1.0 TargetID='' Type=''", d)
+	}
+	if d := deps["Full.Object"]; d.Version != "2.0" || d.TargetID != "Real.Target" || d.Type != "Optional" {
+		t.Errorf("Full.Object = %+v, want Version=2.0 TargetID=Real.Target Type=Optional", d)
+	}
+	if d := deps["Recommended.Dep"]; d.Version != "3.0" || d.Type != "Recommended" {
+		t.Errorf("Recommended.Dep = %+v, want Version=3.0 Type=Recommended", d)
+	}
+
+	// Calling Dependencies() again must return the same cached map, not
+	// re-parse (and must not panic on the second call).
+	if d2 := p.Dependencies(); len(d2) != len(deps) {
+		t.Errorf("second Dependencies() call returned a different map: %v vs %v", d2, deps)
+	}
+}
+
+func TestHumanizeBytes(t *testing.T) {
+	for _, tc := range []struct {
+		size int64
+		want string
+	}{
+		{500, "500 bytes"},
+		{2048, "2.0 KB"},
+		{5 * 1024 * 1024, "5.0 MB"},
+		{2 * 1024 * 1024 * 1024, "2.0 GB"},
+	} {
+		if got := HumanizeBytes(tc.size); got != tc.want {
+			t.Errorf("HumanizeBytes(%d) = %q, want %q", tc.size, got, tc.want)
+		}
+	}
+}

internal/download/wdk_test.go

@@ -0,0 +1,118 @@
+package download
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestWDKNuGetID(t *testing.T) {
+	for _, tc := range []struct{ arch, want string }{
+		{"x64", "Microsoft.Windows.WDK.x64"},
+		{"x86", "Microsoft.Windows.WDK.x64"}, // no 32-bit package exists
+		{"arm64", "Microsoft.Windows.WDK.ARM64"},
+	} {
+		if got := WDKNuGetID(tc.arch); got != tc.want {
+			t.Errorf("WDKNuGetID(%q) = %q, want %q", tc.arch, got, tc.want)
+		}
+	}
+}
+
+func TestSDKBuildPrefix(t *testing.T) {
+	for _, tc := range []struct {
+		name     string
+		selected []*Package
+		want     string
+	}{
+		{"no SDK package", []*Package{{ID: "Something.Else"}}, ""},
+		{"win10sdk", []*Package{{ID: "Win10SDK_10.0.26100", Version: "10.0.26100.1742"}}, "10.0.26100"},
+		{"win11sdk case-insensitive id", []*Package{{ID: "WIN11SDK_10.0.22621", Version: "10.0.22621.5"}}, "10.0.22621"},
+		{"short version", []*Package{{ID: "Win10SDK_x", Version: "10.0"}}, ""},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := SDKBuildPrefix(tc.selected); got != tc.want {
+				t.Errorf("SDKBuildPrefix(...) = %q, want %q", got, tc.want)
+			}
+		})
+	}
+}
+
+func TestFillMissingHostToolsCopiesWithoutOverwriting(t *testing.T) {
+	cDir := t.TempDir()
+	writeFile(t, filepath.Join(cDir, "bin", "10.0.26100.0", "x64", "stampinf.exe"), "x64-stampinf")
+	writeFile(t, filepath.Join(cDir, "bin", "10.0.26100.0", "x64", "inf2cat.exe"), "x64-inf2cat")
+	// x86 already ships its own real inf2cat.exe - must not be clobbered.
+	writeFile(t, filepath.Join(cDir, "bin", "10.0.26100.0", "x86", "inf2cat.exe"), "real-x86-inf2cat")
+
+	if err := fillMissingHostTools(cDir); err != nil {
+		t.Fatal(err)
+	}
+
+	x86Dir := filepath.Join(cDir, "bin", "10.0.26100.0", "x86")
+	stampinf, err := os.ReadFile(filepath.Join(x86Dir, "stampinf.exe"))
+	if err != nil {
+		t.Fatalf("expected stampinf.exe to be copied into x86: %v", err)
+	}
+	if string(stampinf) != "x64-stampinf" {
+		t.Errorf("copied stampinf.exe content = %q, want the x64 copy's content", stampinf)
+	}
+
+	inf2cat, err := os.ReadFile(filepath.Join(x86Dir, "inf2cat.exe"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(inf2cat) != "real-x86-inf2cat" {
+		t.Errorf("inf2cat.exe = %q, want the original x86 file preserved (not overwritten by the x64 copy)", inf2cat)
+	}
+}
+
+func TestFillMissingHostToolsNoBinDirIsNoop(t *testing.T) {
+	if err := fillMissingHostTools(t.TempDir()); err != nil {
+		t.Fatalf("missing bin/ dir should be a no-op, got: %v", err)
+	}
+}
+
+func TestDuplicateVersionedBuildTaskAssemblies(t *testing.T) {
+	cDir := t.TempDir()
+	buildDir := filepath.Join(cDir, "build")
+	writeFile(t, filepath.Join(buildDir, "Microsoft.DriverKit.Build.Tasks.17.0.dll"), "task-dll-bytes")
+	writeFile(t, filepath.Join(buildDir, "Microsoft.DriverKit.Build.Tasks.18.0.dll"), "already-there")
+	writeFile(t, filepath.Join(buildDir, "unrelated.dll"), "unrelated")
+
+	if err := duplicateVersionedBuildTaskAssemblies(cDir, "18.0"); err != nil {
+		t.Fatal(err)
+	}
+
+	// Already had an 18.0 copy - must not have been overwritten.
+	got, err := os.ReadFile(filepath.Join(buildDir, "Microsoft.DriverKit.Build.Tasks.18.0.dll"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != "already-there" {
+		t.Errorf("pre-existing 18.0 dll was overwritten: got %q", got)
+	}
+}
+
+func TestDuplicateVersionedBuildTaskAssembliesCreatesMissingCopy(t *testing.T) {
+	cDir := t.TempDir()
+	buildDir := filepath.Join(cDir, "build")
+	writeFile(t, filepath.Join(buildDir, "sub", "Foo.Bar.17.0.dll"), "bytes")
+
+	if err := duplicateVersionedBuildTaskAssemblies(cDir, "18.0"); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := os.ReadFile(filepath.Join(buildDir, "sub", "Foo.Bar.18.0.dll"))
+	if err != nil {
+		t.Fatalf("expected a Foo.Bar.18.0.dll duplicate: %v", err)
+	}
+	if string(got) != "bytes" {
+		t.Errorf("duplicated dll content = %q, want %q", got, "bytes")
+	}
+}
+
+func TestDuplicateVersionedBuildTaskAssembliesNoBuildDirIsNoop(t *testing.T) {
+	if err := duplicateVersionedBuildTaskAssemblies(t.TempDir(), "18.0"); err != nil {
+		t.Fatalf("missing build/ dir should be a no-op, got: %v", err)
+	}
+}

internal/i18n/i18n.go

@@ -73,18 +73,22 @@ Usage:
   vintner install (i) [dir]            wire up wrappers for a downloaded MSVC
   vintner env (e) --bin <dir/bin/arch> print INCLUDE/LIB for native clang-cl/lld-link use
   vintner version (v)                  print the version
+  vintner doctor                       check wine/toolchain setup
   vintner help (h)                     show this message
   vintner completion bash|zsh          print a shell completion script
 
 Run "vintner <command> --help" for that command's own options - download
-has many, including --with-wdk, --list-workloads, --list-components and
+has many, including --with-wdk, --with-dxsdk, --list-workloads,
---print-deps-tree.
+--list-components and --print-deps-tree.
 
 --dest/[dir] default to ~/.vintner if omitted.
 Language: set VINTNER_LANG=ru (or LANG=ru_RU...) for Russian output.
 Completion: source <(vintner completion bash)  # or zsh
 
-Once installed, add <dir>/bin/<arch> to PATH and invoke the tools directly:
+Once installed, add <dir>/bin/<arch> to PATH and invoke the tools directly,
+or skip PATH and run them through vintner itself - "vintner cl ...",
+"vintner msbuild ...", etc. (set VINTNER_BIN to a <dir>/bin/<arch> if it's
+not the default ~/.vintner/bin/<host-arch>):
   cl, link, lib, ml, ml64, mc, midl, mt, rc, dumpbin, msbuild, nmake, armasm, armasm64, cmd, findstr
 `,
 		RU: `vintner — кросс-компиляция настоящим MSVC на Linux через Wine
@@ -95,18 +99,23 @@ Once installed, add <dir>/bin/<arch> to PATH and invoke the tools directly:
   vintner install (i) [каталог]        настроить обёртки для скачанного MSVC
   vintner env (e) --bin <dir/bin/arch> вывести INCLUDE/LIB для clang-cl/lld-link напрямую
   vintner version (v)                  показать версию
+  vintner doctor                       проверить настройку wine/toolchain
   vintner help (h)                     показать эту справку
   vintner completion bash|zsh          вывести скрипт автодополнения для оболочки
 
 Запустите «vintner <команда> --help» для параметров конкретной команды —
-у download их много, включая --with-wdk, --list-workloads, --list-components
+у download их много, включая --with-wdk, --with-dxsdk, --list-workloads,
-и --print-deps-tree.
+--list-components и --print-deps-tree.
 
 --dest/[каталог] по умолчанию — ~/.vintner.
 Язык: установите VINTNER_LANG=en (или LANG=en_US...) для вывода на английском.
+Можно не трогать PATH: "vintner cl ...", "vintner msbuild ..." и т.д. работают
+напрямую (VINTNER_BIN — если каталог не стандартный ~/.vintner/bin/<hostarch>).
 Автодополнение: source <(vintner completion bash)  # или zsh
 
-После установки добавьте <dir>/bin/<arch> в PATH и вызывайте инструменты напрямую:
+После установки добавьте <dir>/bin/<arch> в PATH и вызывайте инструменты
+напрямую, либо не трогая PATH — «vintner cl ...», «vintner msbuild ...»
+и т.д.:
   cl, link, lib, ml, ml64, mc, midl, mt, rc, dumpbin, msbuild, nmake, armasm, armasm64, cmd, findstr
 `,
 	},
@@ -124,8 +133,8 @@ Once installed, add <dir>/bin/<arch> to PATH and invoke the tools directly:
 		RU: "Каталог не указан, используется значение по умолчанию: %s",
 	},
 	"install.done": {
-		EN: "Done. Add %s to PATH to use cl, link, lib, ...",
+		EN: "Done. Add %s to PATH to use cl, link, lib, ... directly, or run them as \"vintner cl\", \"vintner link\", etc. without touching PATH.",
-		RU: "Готово. Добавьте %s в PATH, чтобы использовать cl, link, lib и т.д.",
+		RU: "Готово. Добавьте %s в PATH, чтобы использовать cl, link, lib и т.д. напрямую, либо запускайте их как «vintner cl», «vintner link» и т.д., не трогая PATH.",
 	},
 
 	"env.usage": {
@@ -161,6 +170,10 @@ Once installed, add <dir>/bin/<arch> to PATH and invoke the tools directly:
 		EN: "Installed WDK (%s) %s at %s\n",
 		RU: "WDK (%s) %s установлен в %s\n",
 	},
+	"download.dxsdk_installed": {
+		EN: "Installed DirectX SDK (June 2010) at %s\n",
+		RU: "DirectX SDK (июнь 2010) установлен в %s\n",
+	},
 	"download.workloads_header": {
 		EN: "Available Workloads (%d):\n",
 		RU: "Доступные рабочие нагрузки (Workload) (%d):\n",
@@ -177,4 +190,41 @@ Once installed, add <dir>/bin/<arch> to PATH and invoke the tools directly:
 		EN: "Do you accept the license? Answer \"yes\" or \"no\": ",
 		RU: "Вы принимаете лицензию? Ответьте «yes» или «no»: ",
 	},
+
+	"doctor.usage": {
+		EN: "usage: vintner doctor",
+		RU: "использование: vintner doctor",
+	},
+	"doctor.section_wine": {
+		EN: "Wine:",
+		RU: "Wine:",
+	},
+	"doctor.section_extract": {
+		EN: "Extraction tools:",
+		RU: "Инструменты распаковки:",
+	},
+	"doctor.section_toolchain": {
+		EN: "Installed toolchain:",
+		RU: "Установленный набор инструментов:",
+	},
+	"doctor.msitools_missing": {
+		EN: "msitools: not found (install the msitools package - needed by `vintner download`)",
+		RU: "msitools: не найден (установите пакет msitools — нужен для `vintner download`)",
+	},
+	"doctor.cabextract_missing": {
+		EN: "cabextract: not found (install the cabextract package - only needed for --with-wdk/--with-dxsdk)",
+		RU: "cabextract: не найден (установите пакет cabextract — нужен только для --with-wdk/--with-dxsdk)",
+	},
+	"doctor.no_toolchain": {
+		EN: "no installed toolchain found under %s (run `vintner download --accept-license && vintner install` first, or set VINTNER_BIN)",
+		RU: "установленный набор инструментов не найден в %s (сначала выполните `vintner download --accept-license && vintner install`, либо задайте VINTNER_BIN)",
+	},
+	"doctor.summary_ok": {
+		EN: "\nAll checks passed.",
+		RU: "\nВсе проверки пройдены.",
+	},
+	"doctor.summary_fail": {
+		EN: "\nSome checks failed - see [FAIL] lines above.",
+		RU: "\nНекоторые проверки не пройдены — см. строки [FAIL] выше.",
+	},
 }

internal/install/install.go

@@ -15,6 +15,7 @@ import (
 	"strings"
 
 	"github.com/Cheviiot/vintner/assets"
+	"github.com/Cheviiot/vintner/internal/lock"
 	"github.com/Cheviiot/vintner/internal/wineenv"
 )
 
@@ -34,6 +35,12 @@ func Install(dest, selfBinary string) error {
 		return fmt.Errorf("destination %q is not a directory", dest)
 	}
 
+	unlock, err := lock.Acquire(dest)
+	if err != nil {
+		return err
+	}
+	defer unlock()
+
 	// Targets are relative so the whole installed tree stays relocatable -
 	// moving or renaming dest doesn't break these symlinks the way an
 	// absolute target baked in at install time would.
@@ -62,6 +69,10 @@ func Install(dest, selfBinary string) error {
 		return err
 	}
 
+	if err := aliasPlatformToolsets(dest); err != nil {
+		return err
+	}
+
 	includeDir := filepath.Join(msvcDir, "include")
 	if err := Lowercase(includeDir, LowercaseOptions{Symlink: true}); err != nil {
 		return fmt.Errorf("lowercasing %s: %w", includeDir, err)

internal/install/platformtoolsets.go

@@ -0,0 +1,92 @@
+package install
+
+import (
+	"os"
+	"path/filepath"
+	"regexp"
+
+	"github.com/Cheviiot/vintner/internal/wineenv"
+)
+
+var rePlatformToolsetDir = regexp.MustCompile(`^v(\d+)$`)
+
+// aliasPlatformToolsets makes every historical PlatformToolset name in
+// wineenv.KnownPlatformToolsets resolve to the one compiler `download`
+// actually fetched.
+//
+// MSBuild decides whether a PlatformToolset is "installed" at all - the
+// check behind MSB8020 - by testing whether
+// MSBuild/Microsoft/VC/v<schema>/Platforms/<arch>/PlatformToolsets/<toolset>/
+// exists on disk (Microsoft.Cpp.props, via
+// ToolLocationHelper.FindRootFolderWhereAllFilesExist). That's a plain file
+// lookup, not influenced by any environment variable - unlike the later,
+// env-var-driven VCInstallDir_<N> checks internal/wrapper's msbuildEnv
+// covers, this one needs the actual directory to exist under dest.
+// Microsoft's own downloaded MSBuild package only ships a PlatformToolsets
+// entry for the exact generation matching the fetched compiler, so any
+// project pinned to an older PlatformToolset (v142 for a project last saved
+// under VS2019, say) fails this check outright even though the one real
+// toolchain installed could easily build it.
+//
+// Toolset.props/Toolset.targets don't hardcode a version number (they just
+// import version-agnostic files like Microsoft.Cpp.MSVC.Toolset.<arch>.props),
+// so a symlink under any other historical name is a correct, transparent
+// alias rather than a divergent copy.
+func aliasPlatformToolsets(dest string) error {
+	schemaDirs, err := filepath.Glob(filepath.Join(dest, "MSBuild", "Microsoft", "VC", "v*"))
+	if err != nil {
+		return err
+	}
+	for _, schemaDir := range schemaDirs {
+		archDirs, err := filepath.Glob(filepath.Join(schemaDir, "Platforms", "*", "PlatformToolsets"))
+		if err != nil {
+			return err
+		}
+		for _, toolsetsDir := range archDirs {
+			if err := aliasOneDir(toolsetsDir); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+// aliasOneDir symlinks every name in wineenv.KnownPlatformToolsets that
+// doesn't already exist in toolsetsDir onto whichever real v<N> toolset
+// subdirectory is actually present there.
+func aliasOneDir(toolsetsDir string) error {
+	entries, err := os.ReadDir(toolsetsDir)
+	if err != nil {
+		return err
+	}
+	var real string
+	for _, e := range entries {
+		if !e.IsDir() {
+			continue
+		}
+		if rePlatformToolsetDir.MatchString(e.Name()) {
+			real = e.Name()
+			break
+		}
+	}
+	if real == "" {
+		// Nothing numeric here (e.g. only the WindowsKernelModeDriver10.0-style
+		// WDK toolsets) - nothing to alias.
+		return nil
+	}
+
+	for _, n := range wineenv.KnownPlatformToolsets {
+		alias := "v" + n
+		if alias == real {
+			continue
+		}
+		aliasPath := filepath.Join(toolsetsDir, alias)
+		if exists(aliasPath) {
+			continue
+		}
+		if err := os.Symlink(real, aliasPath); err != nil {
+			return err
+		}
+	}
+	return nil
+}

internal/install/platformtoolsets_test.go

@@ -0,0 +1,106 @@
+package install
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/Cheviiot/vintner/internal/wineenv"
+)
+
+func TestAliasPlatformToolsetsAliasesRealToolset(t *testing.T) {
+	dest := t.TempDir()
+	toolsetsDir := filepath.Join(dest, "MSBuild", "Microsoft", "VC", "v180", "Platforms", "x64", "PlatformToolsets")
+	realDir := filepath.Join(toolsetsDir, "v145")
+	if err := os.MkdirAll(realDir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(realDir, "Toolset.props"), []byte("<Project/>"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	// A WDK toolset entry alongside it - must not be mistaken for the real
+	// numeric toolset or itself get aliased over.
+	if err := os.MkdirAll(filepath.Join(toolsetsDir, "WindowsKernelModeDriver10.0"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := aliasPlatformToolsets(dest); err != nil {
+		t.Fatalf("aliasPlatformToolsets: %v", err)
+	}
+
+	for _, n := range wineenv.KnownPlatformToolsets {
+		alias := filepath.Join(toolsetsDir, "v"+n)
+		fi, err := os.Lstat(alias)
+		if err != nil {
+			t.Errorf("expected v%s alias to exist: %v", n, err)
+			continue
+		}
+		if fi.Mode()&os.ModeSymlink == 0 {
+			t.Errorf("v%s should be a symlink, got mode %v", n, fi.Mode())
+			continue
+		}
+		target, err := os.Readlink(alias)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if target != "v145" {
+			t.Errorf("v%s symlink target = %q, want \"v145\"", n, target)
+		}
+		// Follow the alias and confirm it actually reaches the real content.
+		if !isFile(filepath.Join(toolsetsDir, "v"+n, "Toolset.props")) {
+			t.Errorf("v%s/Toolset.props not reachable through the alias", n)
+		}
+	}
+
+	if exists(filepath.Join(toolsetsDir, "WindowsKernelModeDriver10.0", "v"+wineenv.KnownPlatformToolsets[0])) {
+		t.Error("WDK toolset directory should not have been touched")
+	}
+}
+
+func TestAliasPlatformToolsetsDoesNotOverwriteExisting(t *testing.T) {
+	dest := t.TempDir()
+	toolsetsDir := filepath.Join(dest, "MSBuild", "Microsoft", "VC", "v180", "Platforms", "x64", "PlatformToolsets")
+	if err := os.MkdirAll(filepath.Join(toolsetsDir, "v145"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	// v142 already genuinely installed (e.g. a real VS install with several
+	// side-by-side toolsets) - must be left alone, not replaced with an alias.
+	real142 := filepath.Join(toolsetsDir, "v142")
+	if err := os.MkdirAll(real142, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(real142, "Toolset.props"), []byte("<!-- real v142 -->"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := aliasPlatformToolsets(dest); err != nil {
+		t.Fatalf("aliasPlatformToolsets: %v", err)
+	}
+
+	fi, err := os.Lstat(real142)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if fi.Mode()&os.ModeSymlink != 0 {
+		t.Error("pre-existing v142 directory should not have been replaced with a symlink")
+	}
+}
+
+func TestAliasPlatformToolsetsNoNumericToolset(t *testing.T) {
+	dest := t.TempDir()
+	// Only a WDK-style toolset present, nothing numeric to alias from.
+	toolsetsDir := filepath.Join(dest, "MSBuild", "Microsoft", "VC", "v180", "Platforms", "x64", "PlatformToolsets")
+	if err := os.MkdirAll(filepath.Join(toolsetsDir, "WindowsUserModeDriver10.0"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := aliasPlatformToolsets(dest); err != nil {
+		t.Fatalf("aliasPlatformToolsets: %v", err)
+	}
+
+	for _, n := range wineenv.KnownPlatformToolsets {
+		if exists(filepath.Join(toolsetsDir, "v"+n)) {
+			t.Errorf("v%s should not have been created with no real numeric toolset present", n)
+		}
+	}
+}

internal/lock/lock.go

@@ -0,0 +1,49 @@
+// Package lock guards a destination directory against two `vintner
+// download`/`install` runs mutating it at the same time.
+package lock
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"syscall"
+)
+
+// FileName is the advisory lock file `download` and `install` both take
+// out against their (usually shared) destination directory before
+// touching anything in it - concurrent download+install, or two
+// downloads, against the same dest could otherwise interleave badly:
+// combineDirTrees' merge logic assumes it's the only thing moving files
+// into a given target at a time, and two `os.Rename` calls racing for the
+// same destination path is exactly the kind of thing that corrupts a tree
+// instead of erroring cleanly.
+const FileName = ".vintner.lock"
+
+// Acquire takes an exclusive, non-blocking lock on dest (creating dest if
+// it doesn't exist yet) and returns a func to release it, which the caller
+// must defer. If another vintner process already holds the lock, returns
+// an error immediately instead of blocking - there's no reason a second
+// invocation should silently queue up and wait for the first to finish
+// touching the same directory; the caller should simply not have started
+// it yet. Uses flock(2), so a crashed holder's lock is released
+// automatically by the kernel when its file descriptor closes - never
+// needs manual cleanup, unlike a plain "does a file exist" lock
+// convention would.
+func Acquire(dest string) (unlock func(), err error) {
+	if err := os.MkdirAll(dest, 0o755); err != nil {
+		return nil, err
+	}
+	path := filepath.Join(dest, FileName)
+	f, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0o644)
+	if err != nil {
+		return nil, err
+	}
+	if err := syscall.Flock(int(f.Fd()), syscall.LOCK_EX|syscall.LOCK_NB); err != nil {
+		f.Close()
+		return nil, fmt.Errorf("another vintner download/install is already running against %s", dest)
+	}
+	return func() {
+		syscall.Flock(int(f.Fd()), syscall.LOCK_UN)
+		f.Close()
+	}, nil
+}

internal/lock/lock_test.go

@@ -0,0 +1,124 @@
+package lock
+
+import (
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+func TestAcquireAndRelease(t *testing.T) {
+	dest := t.TempDir()
+
+	unlock, err := Acquire(dest)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(filepath.Join(dest, FileName)); err != nil {
+		t.Errorf("expected the lock file to exist while held: %v", err)
+	}
+	unlock()
+
+	// Released - a second Acquire against the same dest must now succeed.
+	unlock2, err := Acquire(dest)
+	if err != nil {
+		t.Fatalf("Acquire after release failed: %v", err)
+	}
+	unlock2()
+}
+
+func TestAcquireCreatesDestIfMissing(t *testing.T) {
+	dest := filepath.Join(t.TempDir(), "does", "not", "exist", "yet")
+	unlock, err := Acquire(dest)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer unlock()
+	if fi, err := os.Stat(dest); err != nil || !fi.IsDir() {
+		t.Errorf("expected Acquire to create %s, stat err: %v", dest, err)
+	}
+}
+
+func TestAcquireFailsWhileAlreadyHeld(t *testing.T) {
+	dest := t.TempDir()
+
+	unlock, err := Acquire(dest)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer unlock()
+
+	if _, err := Acquire(dest); err == nil {
+		t.Fatal("expected a second Acquire against the same dest, while the first is still held, to fail")
+	}
+}
+
+func TestAcquireSucceedsAfterHolderReleases(t *testing.T) {
+	dest := t.TempDir()
+
+	unlock1, err := Acquire(dest)
+	if err != nil {
+		t.Fatal(err)
+	}
+	unlock1()
+
+	unlock2, err := Acquire(dest)
+	if err != nil {
+		t.Fatalf("Acquire should succeed once the first holder released: %v", err)
+	}
+	unlock2()
+}
+
+// TestAcquireFailsAcrossRealProcesses is the real end-to-end check: flock
+// is per-open-file-description, not per-process or per-thread, so a lock
+// held by *this* test process via one fd could in principle still be
+// re-acquirable by another fd in the same process depending on the
+// platform's exact semantics. Spawning this test binary as a genuinely
+// separate child process (via the standard TestMain re-exec trick) and
+// having it hold the lock while the parent tries to acquire it is what
+// actually proves two independent `vintner download`/`install` processes
+// contend correctly, not just two Go-level calls in one process.
+func TestAcquireFailsAcrossRealProcesses(t *testing.T) {
+	if os.Getenv("VINTNER_LOCK_TEST_HOLD") != "" {
+		unlock, err := Acquire(os.Getenv("VINTNER_LOCK_TEST_HOLD"))
+		if err != nil {
+			os.Exit(2)
+		}
+		defer unlock()
+		// Signal readiness, then wait to be killed by the parent. A plain
+		// `select {}` here would have zero other goroutines able to ever
+		// wake it, which Go's runtime provably detects as a deadlock and
+		// crashes on ("fatal error: all goroutines are asleep") - a real
+		// timer avoids that.
+		os.Stdout.WriteString("locked\n")
+		time.Sleep(time.Minute)
+	}
+
+	dest := t.TempDir()
+	exe, err := os.Executable()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cmd := exec.Command(exe, "-test.run=TestAcquireFailsAcrossRealProcesses")
+	cmd.Env = append(os.Environ(), "VINTNER_LOCK_TEST_HOLD="+dest)
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := cmd.Start(); err != nil {
+		t.Fatal(err)
+	}
+	defer cmd.Process.Kill()
+
+	buf := make([]byte, len("locked\n"))
+	if _, err := io.ReadFull(stdout, buf); err != nil || string(buf) != "locked\n" {
+		t.Fatalf("child process didn't report holding the lock: %v (%q)", err, buf)
+	}
+
+	if _, err := Acquire(dest); err == nil {
+		t.Fatal("expected Acquire to fail while a separate process holds the lock")
+	}
+}

internal/wineenv/platformtoolsets.go

@@ -0,0 +1,15 @@
+package wineenv
+
+// KnownPlatformToolsets are every numeric PlatformToolset short name
+// Microsoft.Cpp.Default.props has ever defined a
+// _PlatformToolsetShortNameFor_v<N> entry for (VS2013 through the VS2022
+// initial release; excludes the _xp/_wp80/_wp81 variants, which aren't
+// purely numeric). vintner only ever installs one compiler generation, but
+// real .vcxproj files in the wild are pinned to whichever generation they
+// were last edited under - v142 (VS2019) for anything not yet retargeted is
+// extremely common. Shared between internal/install (which symlinks these
+// names onto the one real MSBuild PlatformToolsets directory) and
+// internal/wrapper (which mirrors the same names onto VCInstallDir_<N>/
+// VCToolsInstallDir_<N> for the older, environment-variable-driven toolset
+// redirect chain) - see doc comments there for why both are needed.
+var KnownPlatformToolsets = []string{"90", "100", "110", "120", "140", "141", "142", "143"}

internal/wineenv/wine.go

@@ -14,5 +14,5 @@ func FindWine() (string, error) {
 	if p, err := exec.LookPath("wine"); err == nil {
 		return p, nil
 	}
-	return "", fmt.Errorf("neither wine64 nor wine found in PATH")
+	return "", fmt.Errorf("neither wine64 nor wine found in PATH (install the wine package)")
 }

internal/wineenv/wine_test.go

@@ -0,0 +1,60 @@
+package wineenv
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func fakeBinary(t *testing.T, name string) {
+	t.Helper()
+	bin := t.TempDir()
+	path := filepath.Join(bin, name)
+	if err := os.WriteFile(path, []byte("#!/bin/sh\n"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv("PATH", bin)
+}
+
+func TestFindWinePrefersWine64(t *testing.T) {
+	bin := t.TempDir()
+	for _, name := range []string{"wine64", "wine"} {
+		if err := os.WriteFile(filepath.Join(bin, name), []byte("#!/bin/sh\n"), 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	t.Setenv("PATH", bin)
+
+	got, err := FindWine()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if filepath.Base(got) != "wine64" {
+		t.Errorf("FindWine() = %q, want wine64 to be preferred over wine", got)
+	}
+}
+
+func TestFindWineFallsBackToWine(t *testing.T) {
+	fakeBinary(t, "wine")
+
+	got, err := FindWine()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if filepath.Base(got) != "wine" {
+		t.Errorf("FindWine() = %q, want wine", got)
+	}
+}
+
+func TestFindWineErrorIsActionable(t *testing.T) {
+	t.Setenv("PATH", t.TempDir()) // empty dir, neither binary present
+
+	_, err := FindWine()
+	if err == nil {
+		t.Fatal("expected an error when neither wine64 nor wine is on PATH")
+	}
+	if !strings.Contains(err.Error(), "install") {
+		t.Errorf("FindWine() error = %q, want it to say what to install (matching msiextract/cabextract's error style)", err)
+	}
+}

internal/wrapper/clpost_test.go

@@ -0,0 +1,61 @@
+package wrapper
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestClPostProcessRewritesLineDirectivesInPreprocessedOutput(t *testing.T) {
+	dir := t.TempDir()
+	fi := filepath.Join(dir, "out.i")
+	// A #line directive as cl.exe's /P emits it: z:-prefixed, backslash
+	// path, doubled ("escaped") backslashes, CRLF line ending.
+	input := "#line 1 \"z:\\\\home\\\\user\\\\src\\\\hello.c\"\r\n" +
+		"int main(void) { return 0; }\r\n"
+	if err := os.WriteFile(fi, []byte(input), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	clPostProcess([]string{"/P", "/Fi" + fi, "hello.c"})
+
+	got, err := os.ReadFile(fi)
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := "#line 1 \"/home/user/src/hello.c\"\n" +
+		"int main(void) { return 0; }\n"
+	if string(got) != want {
+		t.Errorf("clPostProcess output = %q, want %q", got, want)
+	}
+}
+
+func TestClPostProcessNoopWithoutP(t *testing.T) {
+	dir := t.TempDir()
+	fi := filepath.Join(dir, "out.i")
+	original := "#line 1 \"z:\\\\foo.c\"\r\n"
+	if err := os.WriteFile(fi, []byte(original), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	// No "/P" flag - should leave the file untouched even though -Fi is present.
+	clPostProcess([]string{"/Fi" + fi, "foo.c"})
+
+	got, err := os.ReadFile(fi)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != original {
+		t.Errorf("file was modified without /P: got %q, want unchanged %q", got, original)
+	}
+}
+
+func TestClPostProcessNoopWithoutFi(t *testing.T) {
+	// Must not panic or error when -Fi wasn't passed - just silently skip.
+	clPostProcess([]string{"/P", "foo.c"})
+}
+
+func TestClPostProcessMissingFileIsSilent(t *testing.T) {
+	// The referenced -Fi file doesn't exist - clPostProcess must not panic.
+	clPostProcess([]string{"/P", "/Fi" + filepath.Join(t.TempDir(), "missing.i"), "foo.c"})
+}

internal/wrapper/msbuildenv.go

@@ -29,7 +29,28 @@ func msbuildEnv(cfg *wineenv.Config, paths *wineenv.Paths) map[string]string {
 		// tools onto the same UTC clock removes the mismatch.
 		"TZ": "UTC",
 
+		// VCToolsVersion must be a real version string, not left unset:
+		// Microsoft.Cpp.VCTools.props itself falls back to the literal
+		// placeholder "VCToolsVersion_is_not_defined" whenever it's empty,
+		// and that placeholder then reaches unconditional (not gated behind
+		// CheckMSVCComponents) version-string comparisons elsewhere in
+		// Microsoft.CppBuild.targets, e.g. the SegmentHeap manifest check's
+		// VersionGreaterThanOrEquals(), which throws MSB4184 on a
+		// non-version string.
+		//
+		// CheckMSVCComponents=false is what actually makes an aliased
+		// PlatformToolset safe to combine with that real version: without
+		// it, CheckVCToolsetVersion (Microsoft.CppBuild.targets, MSB8052)
+		// rejects the combination whenever VCToolsVersion's numeric
+		// generation doesn't match PlatformToolset's - exactly the legacy-
+		// project case toolsetSuffixes/aliasPlatformToolsets exist for (a
+		// v142 project against the one real, newer compiler actually
+		// installed). Everything else CheckMSVCComponents gates
+		// (Microsoft.CppBuild.targets ~495-535) is diagnostic-only - MFC/ATL/
+		// Spectre component presence warnings, none of it feeding into the
+		// actual compile/link - so disabling it costs nothing here.
 		"DisableRegistryUse":  "true",
+		"CheckMSVCComponents": "false",
 		"VCToolsVersion":      cfg.MSVCVer,
 		"VsInstallRoot":       paths.BaseWin + `\`,
 		"VSInstallDir":        paths.BaseWin + `\`,
@@ -58,20 +79,29 @@ func msbuildEnv(cfg *wineenv.Config, paths *wineenv.Paths) map[string]string {
 		"Platform": msbuildPlatform(cfg.Arch),
 	}
 
-	// Microsoft.Cpp.props resolves the compiler/toolset location through
+	// VCInstallDir_<N>/VCToolsInstallDir_<N> are consulted under two
-	// VCInstallDir_<N>/VCToolsInstallDir_<N>, where <N> is whatever numeric
+	// completely different numbering schemes, both needing the single real
-	// suffix the installed MSBuild toolset property sheets use (e.g.
+	// toolchain behind every <N> they might ask for:
-	// .../MSBuild/Microsoft/VC/v180 -> "180"). Populate every one actually
+	//
-	// present, so a project pinned to any of them resolves to the one real
+	//  - Microsoft.Cpp.Default.props keys its early "is this toolset even
-	// toolchain that's installed.
+	//    installed" check (the one MSB8020 comes from) off <N> = the
-	matches, _ := filepath.Glob(filepath.Join(paths.BaseUnix, "MSBuild", "Microsoft", "VC", "v*"))
+	//    PlatformToolset suffix a .vcxproj actually declares (v142, v143,
-	for _, m := range matches {
+	//    v145, ...) - the same short name Microsoft stamps on
-		sub := reToolsetDir.FindStringSubmatch(filepath.Base(m))
+	//    VC/Auxiliary/Build/Microsoft.VCToolsVersion.v<N>.default.props for
-		if sub == nil {
+	//    the downloaded compiler.
-			continue
+	//  - Microsoft.CppBuild.targets (MSB8070) instead keys off <N> = the
-		}
+	//    MSBuild targets-schema version whose Microsoft.Cpp.props ended up
-		env["VCInstallDir_"+sub[1]] = paths.MSVCBaseWin + `\`
+	//    imported for this run (MSBuild/Microsoft/VC/v150|v160|v170|v180 -
-		env["VCToolsInstallDir_"+sub[1]] = paths.MSVCDirWin + `\`
+	//    fixed, shipped identically with every MSBuild release, unrelated to
+	//    which compiler is installed), to locate the specific toolset
+	//    version subfolder.
+	//
+	// Populate every <N> from both sources, all pointing at the one real
+	// toolchain that's installed, so a project pinned to any PlatformToolset
+	// resolves at every stage MSBuild checks it.
+	for _, n := range toolsetSuffixes(paths.BaseUnix) {
+		env["VCInstallDir_"+n] = paths.MSVCBaseWin + `\`
+		env["VCToolsInstallDir_"+n] = paths.MSVCDirWin + `\`
 	}
 
 	if strings.HasSuffix(paths.MSBuildBinDir, "amd64") {
@@ -94,6 +124,133 @@ func msbuildEnv(cfg *wineenv.Config, paths *wineenv.Paths) map[string]string {
 	return env
 }
 
+// toolsetSuffixes collects every numeric <N> that either VCInstallDir_<N>
+// lookup mechanism (see msbuildEnv) might be asked to resolve for this
+// installation: PlatformToolset short names from
+// vc/Auxiliary/Build/Microsoft.VCToolsVersion.v<N>.default.props, MSBuild
+// targets-schema versions from MSBuild/Microsoft/VC/v<N>, and every
+// historical PlatformToolset name (see wineenv.KnownPlatformToolsets) - a
+// project pinned to any of them all resolves to the one real toolchain
+// installed.
+func toolsetSuffixes(baseUnix string) []string {
+	seen := map[string]bool{}
+	var suffixes []string
+
+	record := func(n string) {
+		if seen[n] {
+			return
+		}
+		seen[n] = true
+		suffixes = append(suffixes, n)
+	}
+
+	add := func(dir, prefix, suffix string) {
+		matches, _ := filepath.Glob(filepath.Join(dir, "*"))
+		for _, m := range matches {
+			name := filepath.Base(m)
+			if prefix != "" {
+				if !strings.HasPrefix(name, prefix) {
+					continue
+				}
+				name = strings.TrimPrefix(name, prefix)
+			}
+			name = strings.TrimSuffix(name, suffix)
+			sub := reToolsetDir.FindStringSubmatch(name)
+			if sub == nil {
+				continue
+			}
+			record(sub[1])
+		}
+	}
+
+	add(filepath.Join(baseUnix, "vc", "Auxiliary", "Build"), "Microsoft.VCToolsVersion.", ".default.props")
+	add(filepath.Join(baseUnix, "MSBuild", "Microsoft", "VC"), "", "")
+	for _, n := range wineenv.KnownPlatformToolsets {
+		record(n)
+	}
+
+	return suffixes
+}
+
+// reGlobalProp matches an MSBuild global-property command-line switch
+// ("/p:Name=...", "-property:Name=...", case-insensitive on both the
+// -p/-property spelling and the property name) so msbuildGlobalArgs can tell
+// whether the caller already pinned a given property themselves.
+func reGlobalProp(name string) *regexp.Regexp {
+	return regexp.MustCompile(`(?i)^[-/](p|property):` + regexp.QuoteMeta(name) + `=`)
+}
+
+// msbuildGlobalArgs returns /p: switches to prepend to an MSBuild invocation,
+// one per forced property not already present in args.
+//
+// WindowsTargetPlatformVersion is the one property that needs this rather
+// than an env var: unlike VCInstallDir_<N> (an input to a props-file
+// *lookup*, so any value msbuildEnv sets is visible no matter what a project
+// pins its PlatformToolset to), WindowsTargetPlatformVersion is itself the
+// value most legacy .vcxproj files hardcode directly in a PropertyGroup -
+// and an explicit PropertyGroup assignment always wins over an inherited
+// environment variable of the same name. A command-line global property is
+// the one thing a project file can't override, which is exactly what's
+// needed here: vintner only ever installs one Windows SDK version, so - same
+// reasoning as the PlatformToolset fallback above - any project should
+// transparently build against that one installed version rather than fail
+// outright over an exact version string it happened to be pinned to when
+// last saved from a real Windows SDK selector dropdown.
+func msbuildGlobalArgs(cfg *wineenv.Config, args []string) []string {
+	forced := map[string]string{
+		"WindowsTargetPlatformVersion": cfg.SDKVer,
+	}
+
+	var out []string
+	for name, value := range forced {
+		re := reGlobalProp(name)
+		alreadySet := false
+		for _, a := range args {
+			if re.MatchString(a) {
+				alreadySet = true
+				break
+			}
+		}
+		if !alreadySet {
+			out = append(out, "/p:"+name+"="+value)
+		}
+	}
+	return out
+}
+
+var reNodeReuse = regexp.MustCompile(`(?i)^[-/](nodereuse|nr):`)
+
+// msbuildNodeReuseArgs returns ["/nodeReuse:false"] unless args already pins
+// node reuse one way or the other.
+//
+// MSBuild's node-reuse worker processes (its own /nodeReuse:true default)
+// don't behave like a normal child process here: they're meant to outlive
+// the parent msbuild.exe invocation that spawned them, waiting around under
+// Wine for the *next* msbuild call to reuse them - so nothing about
+// vintner's own process-lifetime handling (see signals.go) touches them,
+// and there's no parent process left to notice if one wedges. If a build is
+// interrupted (Ctrl-C, a killed session, a crashed Wine transport) mid-
+// compile, the worker can be left holding a half-open pipe/mutex,
+// permanently deadlocked rather than exited - confirmed in practice: a
+// stale reused node kept throwing an unrelated-looking
+// `System.TypeLoadException` on Microsoft.VisualStudio.Telemetry on every
+// subsequent build, for hours, until it was killed by hand and the next
+// build got a fresh node. Forcing node reuse off means every invocation
+// gets a clean process, so a wedged one can never poison a later,
+// unrelated build - at the cost of the couple-hundred-ms/node startup time
+// node reuse exists to save. Callers who deliberately want reuse (e.g.
+// running many builds back to back and are prepared to clean up wedged
+// nodes themselves) can still pass their own /nodeReuse or /nr switch to
+// override this.
+func msbuildNodeReuseArgs(args []string) []string {
+	for _, a := range args {
+		if reNodeReuse.MatchString(a) {
+			return nil
+		}
+	}
+	return []string{"/nodeReuse:false"}
+}
+
 func msbuildPlatform(arch string) string {
 	switch arch {
 	case "x86":

internal/wrapper/msbuildenv_test.go

@@ -0,0 +1,222 @@
+package wrapper
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/Cheviiot/vintner/internal/wineenv"
+)
+
+func TestMsbuildPlatform(t *testing.T) {
+	for _, tc := range []struct{ arch, want string }{
+		{"x86", "Win32"},
+		{"x64", "x64"},
+		{"arm", "ARM"},
+		{"arm64", "ARM64"},
+	} {
+		if got := msbuildPlatform(tc.arch); got != tc.want {
+			t.Errorf("msbuildPlatform(%q) = %q, want %q", tc.arch, got, tc.want)
+		}
+	}
+}
+
+func newTestPaths(t *testing.T, cfg *wineenv.Config) (*wineenv.Paths, string) {
+	t.Helper()
+	base := t.TempDir()
+	return wineenv.NewPaths(cfg, base), base
+}
+
+func TestMsbuildEnvBasics(t *testing.T) {
+	cfg := &wineenv.Config{Arch: "x64", Host: "x64", DotnetHost: "amd64", MSVCVer: "14.51.36231", SDKVer: "10.0.26100.0"}
+	paths, _ := newTestPaths(t, cfg)
+
+	env := msbuildEnv(cfg, paths)
+
+	if env["TZ"] != "UTC" {
+		t.Errorf(`env["TZ"] = %q, want "UTC"`, env["TZ"])
+	}
+	if env["DisableRegistryUse"] != "true" {
+		t.Errorf(`env["DisableRegistryUse"] = %q, want "true"`, env["DisableRegistryUse"])
+	}
+	if env["CheckMSVCComponents"] != "false" {
+		t.Errorf(`env["CheckMSVCComponents"] = %q, want "false" (else CheckVCToolsetVersion errors on an aliased PlatformToolset)`, env["CheckMSVCComponents"])
+	}
+	// VCToolsVersion must be a real version string (see msbuildEnv's doc
+	// comment on it: leaving it unset makes Microsoft.Cpp.VCTools.props
+	// substitute a placeholder that then breaks unconditional version
+	// comparisons elsewhere). CheckMSVCComponents=false is what keeps this
+	// safe to combine with an aliased PlatformToolset.
+	if env["VCToolsVersion"] != cfg.MSVCVer {
+		t.Errorf(`env["VCToolsVersion"] = %q, want %q`, env["VCToolsVersion"], cfg.MSVCVer)
+	}
+	if env["WindowsTargetPlatformVersion"] != cfg.SDKVer {
+		t.Errorf(`env["WindowsTargetPlatformVersion"] = %q, want %q`, env["WindowsTargetPlatformVersion"], cfg.SDKVer)
+	}
+	if env["Platform"] != "x64" {
+		t.Errorf(`env["Platform"] = %q, want "x64"`, env["Platform"])
+	}
+	if env["SignMode"] != "off" {
+		t.Errorf(`env["SignMode"] = %q, want "off" (driver builds must not attempt real signing)`, env["SignMode"])
+	}
+	// No WDK content on disk in this test - must not claim otherwise.
+	if _, ok := env["WDKContentRoot"]; ok {
+		t.Error(`env["WDKContentRoot"] set even though no wdk/<arch>/c directory exists`)
+	}
+}
+
+func TestMsbuildEnvDiscoversEveryToolsetVersion(t *testing.T) {
+	cfg := &wineenv.Config{Arch: "x64", Host: "x64", DotnetHost: "amd64", MSVCVer: "14.51.36231", SDKVer: "10.0.26100.0"}
+	paths, base := newTestPaths(t, cfg)
+
+	// Real layout has two independent sources feeding VCInstallDir_<N>/
+	// VCToolsInstallDir_<N> (see toolsetSuffixes' doc comment for why both
+	// are needed): the PlatformToolset short names a downloaded compiler
+	// ships default-props for, and MSBuild's own fixed schema-version dirs.
+	buildDir := filepath.Join(base, "vc", "Auxiliary", "Build")
+	if err := os.MkdirAll(buildDir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	for _, name := range []string{
+		"Microsoft.VCToolsVersion.v145.default.props",
+		"Microsoft.VCToolsVersion.v143.default.props",
+		"Microsoft.VCToolsVersion.default.props", // no version suffix - must not match
+	} {
+		if err := os.WriteFile(filepath.Join(buildDir, name), nil, 0o644); err != nil {
+			t.Fatal(err)
+		}
+	}
+	for _, v := range []string{"v180", "not-a-version"} {
+		if err := os.MkdirAll(filepath.Join(base, "MSBuild", "Microsoft", "VC", v), 0o755); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	env := msbuildEnv(cfg, paths)
+
+	for _, n := range []string{"145", "143", "180"} {
+		if _, ok := env["VCInstallDir_"+n]; !ok {
+			t.Errorf("expected VCInstallDir_%s to be set", n)
+		}
+		if _, ok := env["VCToolsInstallDir_"+n]; !ok {
+			t.Errorf("expected VCToolsInstallDir_%s to be set", n)
+		}
+	}
+	if _, ok := env["VCInstallDir_not-a-version"]; ok {
+		t.Error("a directory not matching v<digits> should not have produced a VCInstallDir_ entry")
+	}
+}
+
+func TestToolsetSuffixesDedupsOverlap(t *testing.T) {
+	base := t.TempDir()
+	buildDir := filepath.Join(base, "vc", "Auxiliary", "Build")
+	if err := os.MkdirAll(buildDir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(buildDir, "Microsoft.VCToolsVersion.v180.default.props"), nil, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.MkdirAll(filepath.Join(base, "MSBuild", "Microsoft", "VC", "v180"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+
+	got := toolsetSuffixes(base)
+	count := 0
+	for _, n := range got {
+		if n == "180" {
+			count++
+		}
+	}
+	if count != 1 {
+		t.Errorf("toolsetSuffixes() returned %q with %d entries for \"180\" (from both sources), want exactly 1", got, count)
+	}
+}
+
+func TestMsbuildGlobalArgsForcesWindowsTargetPlatformVersion(t *testing.T) {
+	cfg := &wineenv.Config{SDKVer: "10.0.26100.0"}
+
+	got := msbuildGlobalArgs(cfg, []string{"Foo.sln", "/p:Configuration=Release"})
+	want := "/p:WindowsTargetPlatformVersion=10.0.26100.0"
+	found := false
+	for _, a := range got {
+		if a == want {
+			found = true
+		}
+	}
+	if !found {
+		t.Errorf("msbuildGlobalArgs(...) = %v, want it to contain %q", got, want)
+	}
+}
+
+func TestMsbuildGlobalArgsRespectsExplicitOverride(t *testing.T) {
+	cfg := &wineenv.Config{SDKVer: "10.0.26100.0"}
+
+	for _, explicit := range []string{
+		"/p:WindowsTargetPlatformVersion=10.0.19041.0",
+		"-p:WindowsTargetPlatformVersion=10.0.19041.0",
+		"/property:WindowsTargetPlatformVersion=10.0.19041.0",
+	} {
+		got := msbuildGlobalArgs(cfg, []string{"Foo.sln", explicit})
+		for _, a := range got {
+			if reGlobalProp("WindowsTargetPlatformVersion").MatchString(a) {
+				t.Errorf("msbuildGlobalArgs with explicit %q also injected %q - should have left the caller's value alone", explicit, a)
+			}
+		}
+	}
+}
+
+func TestMsbuildEnvDetectsWDKContentRoot(t *testing.T) {
+	cfg := &wineenv.Config{Arch: "x64", Host: "x64", DotnetHost: "amd64", MSVCVer: "14.51.36231", SDKVer: "10.0.26100.0"}
+	paths, base := newTestPaths(t, cfg)
+
+	if err := os.MkdirAll(filepath.Join(base, "wdk", "x64", "c"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+
+	env := msbuildEnv(cfg, paths)
+
+	if env["WDKContentRoot"] == "" {
+		t.Error("expected WDKContentRoot to be set once wdk/x64/c exists on disk")
+	}
+	if env["WDKBuildFolder"] != cfg.SDKVer {
+		t.Errorf(`env["WDKBuildFolder"] = %q, want %q`, env["WDKBuildFolder"], cfg.SDKVer)
+	}
+}
+
+func TestMsbuildEnvPreferredToolArchitecture(t *testing.T) {
+	// PreferredToolArchitecture should only be set when the host toolset
+	// bin dir is the 64-bit ("amd64") .NET host - not for arm64.
+	cfg64 := &wineenv.Config{Arch: "x64", Host: "x64", DotnetHost: "amd64", MSVCVer: "1", SDKVer: "1"}
+	paths64, _ := newTestPaths(t, cfg64)
+	if env := msbuildEnv(cfg64, paths64); env["PreferredToolArchitecture"] != "x64" {
+		t.Errorf(`with DotnetHost=amd64, PreferredToolArchitecture = %q, want "x64"`, env["PreferredToolArchitecture"])
+	}
+
+	cfgARM := &wineenv.Config{Arch: "arm64", Host: "arm64", DotnetHost: "arm64", MSVCVer: "1", SDKVer: "1"}
+	pathsARM, _ := newTestPaths(t, cfgARM)
+	if env := msbuildEnv(cfgARM, pathsARM); env["PreferredToolArchitecture"] != "" {
+		t.Errorf(`with DotnetHost=arm64, PreferredToolArchitecture = %q, want unset`, env["PreferredToolArchitecture"])
+	}
+}
+
+func TestMsbuildNodeReuseArgsForcesOffByDefault(t *testing.T) {
+	got := msbuildNodeReuseArgs([]string{"Foo.sln", "/p:Configuration=Release"})
+	want := []string{"/nodeReuse:false"}
+	if len(got) != 1 || got[0] != want[0] {
+		t.Errorf("msbuildNodeReuseArgs(...) = %v, want %v", got, want)
+	}
+}
+
+func TestMsbuildNodeReuseArgsRespectsExplicitOverride(t *testing.T) {
+	for _, explicit := range []string{
+		"/nodeReuse:true",
+		"-nodeReuse:true",
+		"/nr:true",
+		"/NODEREUSE:FALSE", // caller explicitly wanting it off too - still shouldn't double up
+	} {
+		got := msbuildNodeReuseArgs([]string{"Foo.sln", explicit})
+		if got != nil {
+			t.Errorf("msbuildNodeReuseArgs with explicit %q = %v, want nil (left alone)", explicit, got)
+		}
+	}
+}

internal/wrapper/native.go

@@ -1,6 +1,7 @@
 package wrapper
 
 import (
+	"fmt"
 	"os"
 	"os/exec"
 )
@@ -25,17 +26,21 @@ func execInherit(args []string) int {
 	if len(args) == 0 {
 		return 0
 	}
-	cmd := exec.Command(args[0], args[1:]...)
+	tc, cleanup := newToolCommand(args[0], args[1:]...)
-	cmd.Stdin = os.Stdin
+	defer cleanup()
-	cmd.Stdout = os.Stdout
+	tc.Stdin = os.Stdin
-	cmd.Stderr = os.Stderr
+	tc.Stdout = os.Stdout
-	setNewProcessGroup(cmd)
+	tc.Stderr = os.Stderr
-	if err := cmd.Start(); err != nil {
+	if err := tc.Start(); err != nil {
 		return 127
 	}
-	stopSignals := forwardSignals(cmd.Process)
+	stopSignals := forwardSignals(tc.Process)
 	defer stopSignals()
-	if err := cmd.Wait(); err != nil {
+	if err := tc.Wait(); err != nil {
+		if tc.timedOut() {
+			fmt.Fprintln(os.Stderr, tc.timeoutMessage())
+			return 124
+		}
 		if exitErr, ok := err.(*exec.ExitError); ok {
 			return exitErr.ExitCode()
 		}

internal/wrapper/run.go

@@ -30,7 +30,15 @@ const toolRelayName = "toolrelay.exe"
 
 // Run executes the named multi-call tool with args, exactly as the original
 // bash wrappers would, and returns the process exit code.
-func Run(tool string, args []string) int {
+//
+// binDir is the <dest>/bin/<arch> directory holding env.json for this
+// invocation. Pass "" for the ordinary multi-call case (invoked as `cl`,
+// `link`, etc. via a same-directory symlink) to have it resolved from the
+// running binary's own location; a non-empty value is for `vintner <tool>
+// ...` direct dispatch (see cmd/vintner's runTool), which isn't running
+// from inside any particular <dest>/bin/<arch> and so has nothing to
+// resolve on its own.
+func Run(tool string, args []string, binDir string) int {
 	if nativeTools[tool] {
 		return runNative(tool, args)
 	}
@@ -41,19 +49,23 @@ func Run(tool string, args []string) int {
 		return 127
 	}
 
+	scriptDir := binDir
+	if scriptDir == "" {
 		// os.Executable() (backed by /proc/self/exe on Linux) fully resolves
-	// symlinks, unlike os.Args[0]: not every shell passes a PATH-resolved
+		// symlinks, unlike os.Args[0]: not every shell passes a
-	// absolute path as argv[0] (some just pass the bare command name), which
+		// PATH-resolved absolute path as argv[0] (some just pass the bare
-	// would make an argv[0]-based lookup resolve against the caller's cwd
+		// command name), which would make an argv[0]-based lookup resolve
-	// instead of the actual install dir. `install` sets each arch dir up
+		// against the caller's cwd instead of the actual install dir.
-	// with its own local copy of the binary precisely so this resolves to
+		// `install` sets each arch dir up with its own local copy of the
-	// <dest>/bin/<arch>, not <dest>/bin.
+		// binary precisely so this resolves to <dest>/bin/<arch>, not
+		// <dest>/bin.
 		exePath, err := os.Executable()
 		if err != nil {
 			fmt.Fprintln(os.Stderr, "vintner:", err)
 			return 1
 		}
-	scriptDir := filepath.Dir(exePath)
+		scriptDir = filepath.Dir(exePath)
+	}
 
 	cfg, err := wineenv.Load(scriptDir)
 	if err != nil {
@@ -83,26 +95,30 @@ func Run(tool string, args []string) int {
 		// MSBuild: skip all filtering/toolrelay (its output is meant to be
 		// read as-is), and add the extra environment MSBuild's own
 		// toolset/SDK-detection props need on top of the generic
-		// INCLUDE/LIB/WINEPATH.
+		// INCLUDE/LIB/WINEPATH, plus any global properties a project file
-		cmd := exec.Command(wineBin, append([]string{toolExePath}, rewritten...)...)
+		// itself could otherwise override (see msbuildGlobalArgs) and a
+		// forced /nodeReuse:false (see msbuildNodeReuseArgs).
+		msArgs := append(msbuildGlobalArgs(cfg, rewritten), rewritten...)
+		msArgs = append(msbuildNodeReuseArgs(rewritten), msArgs...)
+		tc, cleanup := newToolCommand(wineBin, append([]string{toolExePath}, msArgs...)...)
+		defer cleanup()
 		env := buildEnv(paths)
 		for k, v := range msbuildEnv(cfg, paths) {
 			env = append(env, k+"="+v)
 		}
-		cmd.Env = env
+		tc.Env = env
-		cmd.Stdin = os.Stdin
+		tc.Stdin = os.Stdin
-		setNewProcessGroup(cmd)
+		exitCode = runRawStdout(tc)
-		exitCode = runRawStdout(cmd)
 	default:
 		relay := filepath.Join(paths.BaseUnix, "bin", toolRelayName)
 		if fi, err := os.Stat(relay); err == nil && !fi.IsDir() {
 			exitCode = runViaToolRelay(wineBin, relay, toolExePath, rewritten, paths, s.stdoutFilter, s.stderrFilter)
 		} else {
-			cmd := exec.Command(wineBin, append([]string{toolExePath}, rewritten...)...)
+			tc, cleanup := newToolCommand(wineBin, append([]string{toolExePath}, rewritten...)...)
-			cmd.Env = buildEnv(paths)
+			defer cleanup()
-			cmd.Stdin = os.Stdin
+			tc.Env = buildEnv(paths)
-			setNewProcessGroup(cmd)
+			tc.Stdin = os.Stdin
-			exitCode = runFiltered(cmd, s.stdoutFilter, s.stderrFilter)
+			exitCode = runFiltered(tc, s.stdoutFilter, s.stderrFilter)
 		}
 	}
 
@@ -137,20 +153,20 @@ func runViaToolRelay(wineBin, relayExe, exePath string, args []string, paths *wi
 	defer os.Remove(stderrFifo)
 
 	cmdArgs := append([]string{relayExe, exePath}, args...)
-	cmd := exec.Command(wineBin, cmdArgs...)
+	tc, cleanup := newToolCommand(wineBin, cmdArgs...)
-	cmd.Env = append(buildEnv(paths), "MSVCGOWINE_STDOUT="+stdoutFifo, "MSVCGOWINE_STDERR="+stderrFifo)
+	defer cleanup()
-	setNewProcessGroup(cmd)
+	tc.Env = append(buildEnv(paths), "MSVCGOWINE_STDOUT="+stdoutFifo, "MSVCGOWINE_STDERR="+stderrFifo)
 	if devNull, err := os.OpenFile(os.DevNull, os.O_WRONLY, 0); err == nil {
 		defer devNull.Close()
-		cmd.Stdout = devNull
+		tc.Stdout = devNull
-		cmd.Stderr = devNull
+		tc.Stderr = devNull
 	}
 
-	if err := cmd.Start(); err != nil {
+	if err := tc.Start(); err != nil {
 		fmt.Fprintln(os.Stderr, "vintner:", err)
 		return 1
 	}
-	stopSignals := forwardSignals(cmd.Process)
+	stopSignals := forwardSignals(tc.Process)
 	defer stopSignals()
 
 	var wg sync.WaitGroup
@@ -174,10 +190,14 @@ func runViaToolRelay(wineBin, relayExe, exePath string, args []string, paths *wi
 		pumpLines(f, os.Stderr, stderrF)
 	}()
 
-	err := cmd.Wait()
+	err := tc.Wait()
 	wg.Wait()
 
 	if err != nil {
+		if tc.timedOut() {
+			fmt.Fprintln(os.Stderr, tc.timeoutMessage())
+			return 124
+		}
 		if exitErr, ok := err.(*exec.ExitError); ok {
 			return exitErr.ExitCode()
 		}
@@ -193,23 +213,23 @@ func runViaToolRelay(wineBin, relayExe, exePath string, args []string, paths *wi
 // own copy goroutines - not the caller's terminal or pipe - are exposed to
 // Wine's background processes holding those descriptors open; see
 // pipeDrainGrace.
-func runRawStdout(cmd *exec.Cmd) int {
+func runRawStdout(tc *toolCommand) int {
-	stdout, err := cmd.StdoutPipe()
+	stdout, err := tc.StdoutPipe()
 	if err != nil {
 		fmt.Fprintln(os.Stderr, "vintner:", err)
 		return 1
 	}
-	stderr, err := cmd.StderrPipe()
+	stderr, err := tc.StderrPipe()
 	if err != nil {
 		fmt.Fprintln(os.Stderr, "vintner:", err)
 		return 1
 	}
 
-	if err := cmd.Start(); err != nil {
+	if err := tc.Start(); err != nil {
 		fmt.Fprintln(os.Stderr, "vintner:", err)
 		return 1
 	}
-	stopSignals := forwardSignals(cmd.Process)
+	stopSignals := forwardSignals(tc.Process)
 	defer stopSignals()
 
 	doneOut := make(chan struct{})
@@ -217,11 +237,15 @@ func runRawStdout(cmd *exec.Cmd) int {
 	go func() { io.Copy(os.Stdout, stdout); close(doneOut) }()
 	go func() { io.Copy(os.Stderr, stderr); close(doneErr) }()
 
-	err = cmd.Wait()
+	err = tc.Wait()
 	drain(doneOut)
 	drain(doneErr)
 
 	if err != nil {
+		if tc.timedOut() {
+			fmt.Fprintln(os.Stderr, tc.timeoutMessage())
+			return 124
+		}
 		if exitErr, ok := err.(*exec.ExitError); ok {
 			return exitErr.ExitCode()
 		}
@@ -269,23 +293,23 @@ func buildEnv(p *wineenv.Paths) []string {
 
 // runFiltered streams stdout/stderr line by line through the tool's
 // filters (CR-stripping always applied first), then waits for completion.
-func runFiltered(cmd *exec.Cmd, stdoutF, stderrF lineFilter) int {
+func runFiltered(tc *toolCommand, stdoutF, stderrF lineFilter) int {
-	stdout, err := cmd.StdoutPipe()
+	stdout, err := tc.StdoutPipe()
 	if err != nil {
 		fmt.Fprintln(os.Stderr, "vintner:", err)
 		return 1
 	}
-	stderr, err := cmd.StderrPipe()
+	stderr, err := tc.StderrPipe()
 	if err != nil {
 		fmt.Fprintln(os.Stderr, "vintner:", err)
 		return 1
 	}
 
-	if err := cmd.Start(); err != nil {
+	if err := tc.Start(); err != nil {
 		fmt.Fprintln(os.Stderr, "vintner:", err)
 		return 1
 	}
-	stopSignals := forwardSignals(cmd.Process)
+	stopSignals := forwardSignals(tc.Process)
 	defer stopSignals()
 
 	doneOut := make(chan struct{})
@@ -293,11 +317,15 @@ func runFiltered(cmd *exec.Cmd, stdoutF, stderrF lineFilter) int {
 	go func() { pumpLines(stdout, os.Stdout, stdoutF); close(doneOut) }()
 	go func() { pumpLines(stderr, os.Stderr, stderrF); close(doneErr) }()
 
-	err = cmd.Wait()
+	err = tc.Wait()
 	drain(doneOut)
 	drain(doneErr)
 
 	if err != nil {
+		if tc.timedOut() {
+			fmt.Fprintln(os.Stderr, tc.timeoutMessage())
+			return 124
+		}
 		if exitErr, ok := err.(*exec.ExitError); ok {
 			return exitErr.ExitCode()
 		}

internal/wrapper/timeout.go

@@ -0,0 +1,97 @@
+package wrapper
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+	"syscall"
+	"time"
+)
+
+// waitDelay bounds how long cmd.Wait() itself may block after the process
+// group has already been told to die (by a timeout or a forwarded signal) -
+// usually resolved immediately, but a wedged Wine transport is exactly the
+// case that isn't guaranteed to notice a plain SIGKILL right away.
+const waitDelay = 5 * time.Second
+
+// commandTimeout returns how long a single tool invocation may run before
+// vintner kills it and reports a timeout, from VINTNER_TIMEOUT (a
+// time.ParseDuration string, e.g. "30m", "2h"). Unset, empty, or invalid
+// all mean "no timeout" (0) - the default stays a plain, unbounded build,
+// matching every real build observed so far (Ogre3D's from-scratch build
+// alone ran several minutes). This exists for exactly one failure mode: a
+// wedged Wine-hosted process (a corrupted MSBuild node-reuse worker in the
+// one confirmed case so far, but nothing about the mechanism is
+// MSBuild-specific) that will otherwise never exit on its own, hanging
+// vintner - and whatever's waiting on vintner - forever with no feedback.
+// Automated/scripted callers that would rather fail loudly after N minutes
+// than risk hanging indefinitely can set this; interactive use is
+// unaffected unless it's set.
+func commandTimeout() time.Duration {
+	v := os.Getenv("VINTNER_TIMEOUT")
+	if v == "" {
+		return 0
+	}
+	d, err := time.ParseDuration(v)
+	if err != nil || d <= 0 {
+		return 0
+	}
+	return d
+}
+
+// toolCommand wraps the exec.Cmd every wine-hosted tool invocation is built
+// from, plus enough state to tell a VINTNER_TIMEOUT kill apart from every
+// other failure once Wait() returns.
+type toolCommand struct {
+	*exec.Cmd
+	ctx     context.Context
+	cancel  context.CancelFunc
+	timeout time.Duration // 0 if VINTNER_TIMEOUT wasn't set
+}
+
+// newToolCommand builds a toolCommand: its own process group
+// (setNewProcessGroup) and, when VINTNER_TIMEOUT is set, a deadline that
+// kills the *whole group* - not just the immediate `wine` process, since a
+// wedged Wine-hosted child surviving past its parent is exactly the
+// scenario this needs to reach - if the tool hasn't finished in time.
+//
+// Callers must defer the returned cleanup func, and should call
+// timedOut() after Wait() returns to tell a timeout-triggered kill apart
+// from every other failure.
+func newToolCommand(name string, args ...string) (tc *toolCommand, cleanup func()) {
+	timeout := commandTimeout()
+	if timeout <= 0 {
+		cmd := exec.Command(name, args...)
+		setNewProcessGroup(cmd)
+		return &toolCommand{Cmd: cmd, ctx: context.Background()}, func() {}
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	cmd := exec.CommandContext(ctx, name, args...)
+	setNewProcessGroup(cmd)
+	// cmd.Cancel's default (Go 1.20+) only signals the immediate child;
+	// override it to reach the whole process group, same as
+	// forwardSignals - the wedged process a timeout exists to clean up is
+	// typically under wine, not wine itself.
+	cmd.Cancel = func() error {
+		if cmd.Process == nil {
+			return nil
+		}
+		return syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
+	}
+	cmd.WaitDelay = waitDelay
+	tc = &toolCommand{Cmd: cmd, ctx: ctx, cancel: cancel, timeout: timeout}
+	return tc, cancel
+}
+
+// timedOut reports whether this command was killed by its own
+// VINTNER_TIMEOUT deadline rather than exiting (however it exited) on its
+// own - call after Wait() returns a non-nil error.
+func (tc *toolCommand) timedOut() bool {
+	return tc.ctx.Err() == context.DeadlineExceeded
+}
+
+func (tc *toolCommand) timeoutMessage() string {
+	return fmt.Sprintf("vintner: %s: timed out after %s (VINTNER_TIMEOUT), killed", tc.Path, tc.timeout)
+}

internal/wrapper/timeout_test.go

@@ -0,0 +1,82 @@
+package wrapper
+
+import (
+	"syscall"
+	"testing"
+	"time"
+)
+
+func TestCommandTimeout(t *testing.T) {
+	for _, tc := range []struct {
+		name string
+		env  string
+		want time.Duration
+	}{
+		{"unset", "", 0},
+		{"valid", "30m", 30 * time.Minute},
+		{"invalid unit-less number", "30", 0},
+		{"zero", "0s", 0},
+		{"negative", "-5m", 0},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Setenv("VINTNER_TIMEOUT", tc.env)
+			if got := commandTimeout(); got != tc.want {
+				t.Errorf("commandTimeout() with VINTNER_TIMEOUT=%q = %v, want %v", tc.env, got, tc.want)
+			}
+		})
+	}
+}
+
+// TestNewToolCommandKillsOnTimeout is the real end-to-end check: start a
+// process that would otherwise run far longer than the timeout (mimicking
+// a wedged Wine-hosted tool), and confirm newToolCommand's deadline
+// actually kills it - not just that timedOut() would report true in
+// principle, but that Wait() actually returns, promptly, with the process
+// gone.
+func TestNewToolCommandKillsOnTimeout(t *testing.T) {
+	t.Setenv("VINTNER_TIMEOUT", "300ms")
+
+	tc, cleanup := newToolCommand("sleep", "30")
+	defer cleanup()
+
+	if err := tc.Start(); err != nil {
+		t.Fatalf("starting sleep: %v", err)
+	}
+	pid := tc.Process.Pid
+
+	done := make(chan error, 1)
+	go func() { done <- tc.Wait() }()
+
+	select {
+	case err := <-done:
+		if err == nil {
+			t.Fatal("expected sleep 30 to be killed by the timeout, but it exited successfully")
+		}
+		if !tc.timedOut() {
+			t.Errorf("Wait() returned an error (%v) but timedOut() = false", err)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("newToolCommand's timeout did not kill the process within 5s of a 300ms deadline")
+	}
+
+	// Belt-and-suspenders: the process should genuinely be gone, not just
+	// reported as such. Signal 0 sends nothing but still fails with ESRCH
+	// once the pid is gone - the standard Unix way to probe existence.
+	if err := syscall.Kill(pid, 0); err == nil {
+		t.Errorf("pid %d still exists after the timeout killed it", pid)
+	}
+}
+
+func TestNewToolCommandNoTimeoutByDefault(t *testing.T) {
+	t.Setenv("VINTNER_TIMEOUT", "")
+
+	tc, cleanup := newToolCommand("true")
+	defer cleanup()
+
+	if err := tc.Run(); err != nil {
+		t.Fatalf("running `true` with no VINTNER_TIMEOUT set: %v", err)
+	}
+	if tc.timedOut() {
+		t.Error("timedOut() = true for a command that finished well within any reasonable time, with no timeout configured")
+	}
+}

internal/wrapper/tools.go

@@ -4,7 +4,11 @@
 // filtering its output.
 package wrapper
 
-import "github.com/Cheviiot/vintner/internal/wineenv"
+import (
+	"sort"
+
+	"github.com/Cheviiot/vintner/internal/wineenv"
+)
 
 // dirKind selects which install directory a tool's real .exe lives in.
 type dirKind int
@@ -46,6 +50,32 @@ var Tools = map[string]spec{
 // nativeTools are handled entirely without Wine.
 var nativeTools = map[string]bool{"cmd": true, "findstr": true}
 
+// IsTool reports whether name is a recognized wrapped tool - either a
+// Wine-hosted one in Tools or a native shim in nativeTools. Shared between
+// the ordinary multi-call dispatch (invoked *as* one of these names via a
+// same-directory symlink) and `vintner <tool> ...` direct dispatch, so both
+// recognize exactly the same set of names.
+func IsTool(name string) bool {
+	_, ok := Tools[name]
+	return ok || nativeTools[name]
+}
+
+// ToolNames returns every recognized tool name, sorted - Tools and
+// nativeTools combined. Used to generate shell completion without a
+// separate hand-maintained list that could drift from the real set (as
+// happened once already with a stale --with-dxsdk completion entry).
+func ToolNames() []string {
+	names := make([]string, 0, len(Tools)+len(nativeTools))
+	for name := range Tools {
+		names = append(names, name)
+	}
+	for name := range nativeTools {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	return names
+}
+
 func (s spec) exeDir(p *wineenv.Paths) string {
 	switch s.dir {
 	case dirSDK:

internal/wrapper/tools_test.go

@@ -0,0 +1,63 @@
+package wrapper
+
+import (
+	"testing"
+
+	"github.com/Cheviiot/vintner/internal/wineenv"
+)
+
+func TestSpecExeDir(t *testing.T) {
+	paths := &wineenv.Paths{
+		BinDir:        "/bin-dir",
+		SDKBinDir:     "/sdk-bin-dir",
+		MSBuildBinDir: "/msbuild-bin-dir",
+	}
+	for _, tc := range []struct {
+		name string
+		dir  dirKind
+		want string
+	}{
+		{"dirBin", dirBin, "/bin-dir"},
+		{"dirSDK", dirSDK, "/sdk-bin-dir"},
+		{"dirMSBuild", dirMSBuild, "/msbuild-bin-dir"},
+	} {
+		s := spec{dir: tc.dir}
+		if got := s.exeDir(paths); got != tc.want {
+			t.Errorf("%s: exeDir() = %q, want %q", tc.name, got, tc.want)
+		}
+	}
+}
+
+func TestToolsAndNativeToolsAreDisjoint(t *testing.T) {
+	for name := range Tools {
+		if nativeTools[name] {
+			t.Errorf("%q is in both Tools and nativeTools", name)
+		}
+	}
+}
+
+func TestEveryToolHasAnExeName(t *testing.T) {
+	for name, s := range Tools {
+		if s.exeName == "" {
+			t.Errorf("Tools[%q] has no exeName", name)
+		}
+	}
+}
+
+func TestIsTool(t *testing.T) {
+	for name := range Tools {
+		if !IsTool(name) {
+			t.Errorf("IsTool(%q) = false, want true (it's in Tools)", name)
+		}
+	}
+	for name := range nativeTools {
+		if !IsTool(name) {
+			t.Errorf("IsTool(%q) = false, want true (it's in nativeTools)", name)
+		}
+	}
+	for _, name := range []string{"download", "install", "env", "version", "help", "completion", "frobnicate", ""} {
+		if IsTool(name) {
+			t.Errorf("IsTool(%q) = true, want false", name)
+		}
+	}
+}