fix(windows): use PowerShell for command execution

internal/agent/loop_test.go

@@ -2404,7 +2404,11 @@ func TestRunApprovedNetworkBashPromptAppliesTurnNetworkGrant(t *testing.T) {
 	root := t.TempDir()
 	command := "PATH=.:$PATH curl https://example.com"
 	if runtime.GOOS == "windows" {
-		command = "set PATH=.;%PATH% && curl https://example.com"
+		if windowsTestUsesPowerShell() {
+			command = `$env:PATH = '.;' + $env:PATH; curl.cmd https://example.com`
+		} else {
+			command = "set PATH=.;%PATH% && curl https://example.com"
+		}
 		fakeCurl := filepath.Join(root, "curl.cmd")
 		if err := os.WriteFile(fakeCurl, []byte("@echo fake curl %*\r\n"), 0o755); err != nil {
 			t.Fatal(err)
@@ -2525,13 +2529,17 @@ func TestRunDoesNotOfferPrefixApprovalForUnsafeBashCommand(t *testing.T) {
 
 func TestRunPromptsForDestructiveShellInsteadOfSandboxDeny(t *testing.T) {
 	root := t.TempDir()
+	command := "echo rm -rf /"
+	if runtime.GOOS == "windows" && windowsTestUsesPowerShell() {
+		command = `Write-Output 'rm -rf /'`
+	}
 	registry := tools.NewRegistry()
 	registry.Register(tools.NewScopedBashTool(root, nil))
 	provider := &mockProvider{
 		turns: [][]zeroruntime.StreamEvent{
 			{
 				{Type: zeroruntime.StreamEventToolCallStart, ToolCallID: "call-1", ToolName: "bash"},
-				{Type: zeroruntime.StreamEventToolCallDelta, ToolCallID: "call-1", ArgumentsFragment: `{"command":"echo rm -rf /"}`},
+				{Type: zeroruntime.StreamEventToolCallDelta, ToolCallID: "call-1", ArgumentsFragment: `{"command":` + quoteJSONString(command) + `}`},
 				{Type: zeroruntime.StreamEventToolCallEnd, ToolCallID: "call-1"},
 				{Type: zeroruntime.StreamEventDone},
 			},
@@ -2627,6 +2635,12 @@ func TestRunAlwaysAllowWithoutSandboxStillAllowsCall(t *testing.T) {
 	}
 }
 
+func windowsTestUsesPowerShell() bool {
+	executable, _ := tools.HostShellCommand("")
+	name := strings.ToLower(filepath.Base(executable))
+	return strings.Contains(name, "powershell") || strings.HasPrefix(name, "pwsh")
+}
+
 func containsPermissionDecision(decisions []PermissionDecisionAction, want PermissionDecisionAction) bool {
 	for _, decision := range decisions {
 		if decision == want {
@@ -3160,22 +3174,17 @@ func TestBuildSystemPromptInjectsHostShellContext(t *testing.T) {
 		t.Fatalf("expected operating system in environment block, got %q", prompt)
 	}
 	if runtime.GOOS == "windows" {
-		for _, want := range []string{"Windows cmd.exe syntax", "cwd argument", "MSYS binaries", "grep", "require_escalated", "use double quotes around the value"} {
-			if !strings.Contains(prompt, want) {
-				t.Fatalf("expected Windows shell guidance to mention %q, got %q", want, prompt)
-			}
+		wants := []string{"workdir/cwd", "MSYS binaries"}
+		if windowsTestUsesPowerShell() {
+			wants = append(wants, "PowerShell", "Get-ChildItem", "Select-String", "$env:NAME", "require_escalated")
+		} else {
+			wants = append(wants, "cmd.exe", "double quotes")
 		}
-		// The examples must themselves use the safe (double-quoted) form; a
-		// single-quoted example here would teach the model the exact syntax
-		// that fails under cmd.exe.
-		for _, want := range []string{`--jq ".a | b"`, `-run "A|B"`} {
+		for _, want := range wants {
 			if !strings.Contains(prompt, want) {
-				t.Fatalf("expected double-quoted example %q in Windows shell guidance, got %q", want, prompt)
+				t.Fatalf("expected selected Windows shell guidance to mention %q, got %q", want, prompt)
 			}
 		}
-		if strings.Contains(prompt, `'.a | b'`) || strings.Contains(prompt, `'A|B'`) {
-			t.Fatalf("Windows shell guidance must not show the unsafe single-quoted form, got %q", prompt)
-		}
 	} else if !strings.Contains(prompt, "/bin/sh syntax") {
 		t.Fatalf("expected POSIX shell guidance in prompt, got %q", prompt)
 	}

internal/agent/system_prompt.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/Gitlawb/zero/internal/config"
 	"github.com/Gitlawb/zero/internal/repomap"
+	"github.com/Gitlawb/zero/internal/tools"
 	"github.com/Gitlawb/zero/internal/workspaceseed"
 )
 
@@ -310,11 +311,7 @@ func workspaceContext(cwd string) string {
 	b.WriteString("<environment>\n")
 	b.WriteString("Working directory: " + cwd + "\n")
 	b.WriteString("Operating system: " + runtime.GOOS + "\n")
-	if runtime.GOOS == "windows" {
-		b.WriteString("Shell syntax: Windows cmd.exe syntax for exec_command/bash tools. To put | & > < etc inside an arg value, use double quotes around the value, not single quotes (single quotes do not protect metachars in cmd.exe): gh --jq \".a | b\", go test -run \"A|B\". Do not pipe to or invoke POSIX coreutils from Git for Windows (usr\\bin head/grep/tail/cat/...): they are MSYS binaries and fail under the write-restricted sandbox; use native Zero tools (grep, read_file, list_directory, glob) or cmd.exe findstr/more instead, or sandbox_permissions require_escalated only when host-level execution is truly required. Prefer the workdir/cwd argument over cd when changing directories.\n")
-	} else {
-		b.WriteString("Shell syntax: /bin/sh syntax for exec_command/bash tools; prefer the workdir/cwd argument instead of cd when changing directories.\n")
-	}
+	b.WriteString(tools.HostShellEnvironmentGuidance() + "\n")
 	if branch := gitBranchForPrompt(cwd); branch != "" {
 		b.WriteString("Git branch: " + branch + "\n")
 	}

internal/sandbox/analyzer.go

@@ -27,11 +27,22 @@ var destructivePrograms = map[string]bool{
 	"mkfs": true, "fdisk": true, "shred": true, "dd": true, "parted": true,
 }
 
+var powerShellRemoveItemPrograms = map[string]bool{
+	"remove-item": true,
+	"ri":          true,
+	"rd":          true,
+	"rmdir":       true,
+	"del":         true,
+	"erase":       true,
+	"rm":          true,
+}
+
 // networkPrograms are commands that perform network egress/ingress.
 var networkPrograms = map[string]bool{
 	"curl": true, "wget": true, "ssh": true, "scp": true, "sftp": true,
 	"rsync": true, "nc": true, "ncat": true, "netcat": true, "telnet": true,
-	"ftp": true,
+	"ftp": true, "iwr": true, "irm": true, "invoke-webrequest": true,
+	"invoke-restmethod": true,
 }
 
 var localServerPrograms = map[string]bool{
@@ -172,7 +183,10 @@ func analyzeInto(script string, result *AnalysisResult, seen map[string]bool, de
 		if commandUsesNetwork(prog, rest) {
 			result.Network = true
 		}
-		if destructivePrograms[prog] || (prog == "rm" && hasRecursiveForce(rest)) || (prog == "find" && hasFindDelete(rest)) {
+		if destructivePrograms[prog] ||
+			(prog == "rm" && hasRecursiveForce(rest)) ||
+			(powerShellRemoveItemPrograms[prog] && hasPowerShellRecursiveForce(rest)) ||
+			(prog == "find" && hasFindDelete(rest)) {
 			result.Destructive = true
 		}
 		return true
@@ -479,6 +493,19 @@ func hasRecursiveForce(args []*syntax.Word) bool {
 	return recursive && force
 }
 
+func hasPowerShellRecursiveForce(args []*syntax.Word) bool {
+	recursive, force := false, false
+	for _, arg := range args {
+		switch strings.ToLower(wordText(arg)) {
+		case "-recurse", "-r":
+			recursive = true
+		case "-force":
+			force = true
+		}
+	}
+	return recursive && force
+}
+
 func hasFindDelete(args []*syntax.Word) bool {
 	for _, arg := range args {
 		if wordText(arg) == "-delete" {

internal/sandbox/analyzer_test.go

@@ -45,6 +45,27 @@ func TestAnalyzeCommand(t *testing.T) {
 		{name: "sudo dynamic flag then rm -rf", script: `sudo "$maybe" rm -rf /tmp/x`, destructive: true},
 
 		{name: "curl", script: "curl https://example.com", network: true},
+		{name: "PowerShell iwr alias", script: "iwr https://example.com", network: true},
+		{name: "PowerShell irm alias", script: "irm https://example.com", network: true},
+		{name: "PowerShell Invoke-WebRequest", script: "Invoke-WebRequest https://example.com", network: true},
+		{name: "PowerShell Invoke-RestMethod", script: "Invoke-RestMethod https://example.com", network: true},
+		{name: "PowerShell Remove-Item recursive force", script: `Remove-Item -Recurse -Force 'C:\temp\x'`, destructive: true},
+		{name: "PowerShell rm recursive force", script: `rm -Recurse -Force 'C:\temp\x'`, destructive: true},
+		{name: "PowerShell ri recursive force", script: `ri -Recurse -Force 'C:\temp\x'`, destructive: true},
+		{name: "PowerShell rd recursive force", script: `rd -Recurse -Force 'C:\temp\x'`, destructive: true},
+		{name: "PowerShell rmdir recursive force", script: `rmdir -Recurse -Force 'C:\temp\x'`, destructive: true},
+		{name: "PowerShell del recursive force", script: `del -Recurse -Force 'C:\temp\x'`, destructive: true},
+		{name: "PowerShell erase recursive force", script: `erase -Recurse -Force 'C:\temp\x'`, destructive: true},
+		{name: "PowerShell ambiguous force abbreviation", script: `Remove-Item -Recurse -f 'C:\temp\x'`, destructive: false},
+		{name: "PowerShell Remove-Item without recurse", script: `Remove-Item -Force 'C:\temp\x'`, destructive: false},
+		{name: "Windows curl cmd", script: "curl.cmd https://example.com", network: true},
+		{name: "Windows curl exe", script: "curl.exe https://example.com", network: true},
+		{name: "Windows drive path curl exe", script: `'C:\tools\curl.exe' https://example.com`, network: true},
+		{name: "Windows UNC path curl exe", script: `'\\server\share\curl.exe' https://example.com`, network: true},
+		{name: "Windows dot relative path curl exe", script: `'.\curl.exe' https://example.com`, network: true},
+		{name: "Windows relative path curl exe", script: `'tools\curl.exe' https://example.com`, network: true},
+		{name: "Windows drive relative path curl exe", script: `'C:curl.exe' https://example.com`, network: true},
+		{name: "Windows npm cmd", script: "npm.cmd install", network: true},
 		{name: "wget piped to shell", script: "wget -qO- https://x.test | sh", network: true},
 		{name: "python http server", script: "python3 -m http.server 8000", network: true},
 		{name: "python pip install", script: "python3 -m pip install requests", network: true},

internal/sandbox/engine_test.go

@@ -74,6 +74,25 @@ func TestEngineBashAllowGrantDoesNotBypassNetworkPrompt(t *testing.T) {
 	}
 }
 
+func TestEngineClassifiesPowerShellCurlCommandAsNetwork(t *testing.T) {
+	engine := NewEngine(EngineOptions{
+		WorkspaceRoot: t.TempDir(),
+		Policy:        DefaultPolicy(),
+	})
+	decision := engine.Evaluate(context.Background(), Request{
+		ToolName:       "bash",
+		SideEffect:     SideEffectShell,
+		Permission:     PermissionPrompt,
+		PermissionMode: PermissionModeAsk,
+		Args: map[string]any{
+			"command": `$env:PATH = '.;' + $env:PATH; curl.cmd https://example.com`,
+		},
+	})
+	if decision.Action != ActionPrompt || decision.Reason != ReasonNetworkBlocked || !HasRiskCategory(decision.Risk, "network") {
+		t.Fatalf("PowerShell curl command decision = %#v, want network prompt", decision)
+	}
+}
+
 func TestUnsandboxedExecutionAllowedPreservesDeniedReads(t *testing.T) {
 	root := t.TempDir()
 	policy := DefaultPolicy()

internal/sandbox/runner_windows_integration_test.go

@@ -266,6 +266,74 @@ func TestWindowsRestrictedTokenNestedPipeCapture(t *testing.T) {
 	}
 }
 
+// TestWindowsRestrictedTokenPowerShell exercises the default Windows shell
+// shape end to end under the write-restricted token. It covers PowerShell
+// initialization, a native pipeline (which creates IPC objects), UTF-8 output,
+// and workspace write enforcement.
+func TestWindowsRestrictedTokenPowerShell(t *testing.T) {
+	if os.Getenv("ZERO_SANDBOX_REAL_SMOKE") != "1" {
+		t.Skip("set ZERO_SANDBOX_REAL_SMOKE=1 to run real Windows sandbox smoke tests")
+	}
+	runnerExe := realSmokeExecutable(t, "ZERO_WINDOWS_COMMAND_RUNNER_EXE", WindowsSandboxCommandRunnerName)
+	powerShell := realSmokePowerShell(t)
+
+	root := t.TempDir()
+	outside := t.TempDir()
+	sandboxHome := filepath.Join(root, ".zero-sandbox")
+	profile := PermissionProfile{
+		FileSystem: FileSystemPolicy{
+			Kind:                 FileSystemRestricted,
+			ReadRoots:            []string{root},
+			WriteRoots:           []WritableRoot{{Root: root}},
+			IncludePlatformRoots: true,
+			AllowTemp:            true,
+		},
+		Network: NetworkPolicy{Mode: NetworkDeny},
+	}
+	config := WindowsSandboxCommandArgsOptions{
+		SandboxHome:       sandboxHome,
+		CommandCWD:        root,
+		WorkspaceRoots:    []string{root},
+		PermissionProfile: profile,
+		SandboxLevel:      WindowsSandboxLevelUnelevated,
+	}
+
+	insideMarker := filepath.Join(root, "powershell-ok.txt")
+	script := "$ErrorActionPreference='Stop'; " +
+		"[Console]::OutputEncoding=[System.Text.Encoding]::UTF8; " +
+		"$values = 1,2,3 | ForEach-Object { $_ * 2 }; " +
+		"[IO.File]::WriteAllText(" + powershellSingleQuote(insideMarker) + ", (($values -join ',') + ' ✓'))"
+	runWindowsRealSmokeCommand(t, runnerExe, config, []string{
+		powerShell, "-NoLogo", "-NoProfile", "-Command", script,
+	}, 0)
+	if bytes, err := os.ReadFile(insideMarker); err != nil || strings.TrimSpace(string(bytes)) != "2,4,6 ✓" {
+		t.Fatalf("PowerShell sandbox marker = %q, %v; want pipeline output", bytes, err)
+	}
+
+	outsideMarker := filepath.Join(outside, "powershell-denied.txt")
+	deniedScript := "$ErrorActionPreference='Stop'; " +
+		"[IO.File]::WriteAllText(" + powershellSingleQuote(outsideMarker) + ", 'leaked')"
+	runWindowsRealSmokeCommand(t, runnerExe, config, []string{
+		powerShell, "-NoLogo", "-NoProfile", "-Command", deniedScript,
+	}, 1)
+	if _, err := os.Stat(outsideMarker); err == nil {
+		t.Fatal("sandboxed PowerShell wrote outside every granted root")
+	} else if !os.IsNotExist(err) {
+		t.Fatalf("stat outside PowerShell marker: %v", err)
+	}
+}
+
+func realSmokePowerShell(t *testing.T) string {
+	t.Helper()
+	for _, candidate := range []string{"pwsh.exe", "pwsh", "powershell.exe", "powershell"} {
+		if path, err := exec.LookPath(candidate); err == nil {
+			return path
+		}
+	}
+	t.Skip("PowerShell is unavailable")
+	return ""
+}
+
 func realSmokeExecutable(t *testing.T, envKey string, fallbackName string) string {
 	t.Helper()
 	if path := os.Getenv(envKey); path != "" {

internal/sandbox/safe_command.go

@@ -430,25 +430,70 @@ func shellDashCPayload(program string, fields []string) string {
 // name: it strips shell quoting/escaping characters (", ', `, \) wherever they
 // appear in the token (including embedded ones like `vi\m` or `v"i"m`), strips
 // leading command-substitution markers, removes any directory prefix (so
-// /usr/bin/vim and C:\tools\vim.exe match "vim"), and lowercases. This closes
-// path/quote/substitution evasions of the detector.
+// /usr/bin/vim and C:\tools\vim.exe match "vim"), removes Windows executable
+// suffixes, and lowercases. This closes path/quote/substitution evasions of the
+// detector and keeps curl.exe/npm.cmd equivalent to curl/npm for risk analysis.
 func normalizeProgramToken(field string) string {
 	token := strings.TrimSpace(field)
 	token = strings.TrimLeft(token, "$(")
 	token = strings.TrimRight(token, ")")
-	// Strip shell quoting/escaping characters (", ', `, \) wherever they appear
-	// in the token — surrounding, embedded, or as a mid-word escape — so
-	// "vim", v"i"m, 'v'im, and vi\m all collapse to the program name. This is
-	// done BEFORE the directory-prefix trim so an escape can't masquerade as a
-	// path separator (e.g. vi\m must become vim, not m).
-	token = stripChars(token, "\"'`\\")
-	// Strip a directory prefix so /usr/bin/vim reduces to the basename. (A
-	// Windows-style backslash path separator is already removed above, so only
-	// the POSIX separator remains to split on.)
-	if i := strings.LastIndex(token, "/"); i >= 0 {
-		token = token[i+1:]
-	}
-	return strings.ToLower(token)
+	// PowerShell commonly invokes drive-letter, UNC, and relative paths. Extract
+	// their basename while backslashes still carry path-separator meaning;
+	// removing them first would turn C:\tools\curl.exe into c:toolscurl.exe and
+	// bypass the canonical curl risk entry.
+	pathToken := stripChars(token, "\"'`")
+	if windowsPathBasename, ok := windowsExecutablePathBasename(pathToken); ok {
+		token = windowsPathBasename
+	} else {
+		// Strip shell quoting/escaping characters (", ', `, \) wherever they
+		// appear in the token — surrounding, embedded, or as a mid-word escape
+		// — so "vim", v"i"m, 'v'im, and vi\m all collapse to the program name.
+		token = stripChars(token, "\"'`\\")
+		// Strip a directory prefix so /usr/bin/vim reduces to the basename.
+		if i := strings.LastIndex(token, "/"); i >= 0 {
+			token = token[i+1:]
+		}
+	}
+	token = strings.ToLower(token)
+	for _, suffix := range []string{".exe", ".cmd", ".bat", ".com"} {
+		if strings.HasSuffix(token, suffix) {
+			return strings.TrimSuffix(token, suffix)
+		}
+	}
+	return token
+}
+
+func windowsExecutablePathBasename(token string) (string, bool) {
+	drivePath := len(token) >= 3 &&
+		((token[0] >= 'a' && token[0] <= 'z') || (token[0] >= 'A' && token[0] <= 'Z')) &&
+		token[1] == ':'
+	uncPath := strings.HasPrefix(token, `\\`)
+	explicitRelativePath := strings.HasPrefix(token, `.\`) || strings.HasPrefix(token, `..\`)
+	backslashRelativePath := strings.ContainsRune(token, '\\') && hasWindowsExecutableSuffix(token)
+	if !drivePath && !uncPath && !explicitRelativePath && !backslashRelativePath {
+		return "", false
+	}
+	index := strings.LastIndexAny(token, `\/`)
+	if index >= 0 {
+		if index+1 >= len(token) {
+			return "", false
+		}
+		return token[index+1:], true
+	}
+	if drivePath && len(token) > 2 {
+		return token[2:], true
+	}
+	return "", false
+}
+
+func hasWindowsExecutableSuffix(token string) bool {
+	token = strings.ToLower(token)
+	for _, suffix := range []string{".exe", ".cmd", ".bat", ".com"} {
+		if strings.HasSuffix(token, suffix) {
+			return true
+		}
+	}
+	return false
 }
 
 // stripChars returns s with every rune in cutset removed.