fix(tools): Windows cmd.exe quoting guidance and clipboard escaping fix

internal/agent/loop_test.go

@@ -2907,9 +2907,20 @@ func TestBuildSystemPromptInjectsHostShellContext(t *testing.T) {
 		t.Fatalf("expected operating system in environment block, got %q", prompt)
 	}
 	if runtime.GOOS == "windows" {
-		if !strings.Contains(prompt, "Windows cmd.exe syntax") || !strings.Contains(prompt, "cwd argument") {
+		if !strings.Contains(prompt, "Windows cmd.exe syntax") || !strings.Contains(prompt, "use double quotes around the value") {
 			t.Fatalf("expected Windows cmd.exe shell guidance in prompt, got %q", prompt)
 		}
+		// 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"`} {
+			if !strings.Contains(prompt, want) {
+				t.Fatalf("expected double-quoted example %q in Windows shell guidance, 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

@@ -259,7 +259,7 @@ func workspaceContext(cwd string) string {
 	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; prefer the workdir/cwd argument instead of cd when changing directories.\n")
+		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\". Avoid POSIX-only commands (head, tail, ls, cat, grep, ps, ...); prefer workdir/cwd over cd; prefer native tools (list_directory, read_file, grep, glob) over shell for file ops.\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")
 	}

internal/imageinput/clipboard.go

@@ -75,7 +75,13 @@ func readClipboardImageWindows() ([]byte, error) {
 	tmpPath := tmpFile.Name()
 	tmpFile.Close()
 	defer os.Remove(tmpPath)
-	script := `Add-Type -AssemblyName System.Windows.Forms; Add-Type -AssemblyName System.Drawing; $img = [System.Windows.Forms.Clipboard]::GetImage(); if ($img -ne $null) { $img.Save('` + tmpPath + `', [System.Drawing.Imaging.ImageFormat]::Png) }`
+
+	// Stay on -Command: -File is subject to script execution policy (default
+	// Restricted on Windows clients) and Windows PowerShell decodes BOM-less
+	// UTF-8 .ps1 files as ANSI. Doubling single quotes is all the escaping the
+	// single-quoted PowerShell literal needs.
+	escapedTmpPath := strings.ReplaceAll(tmpPath, "'", "''")
+	script := `Add-Type -AssemblyName System.Windows.Forms; Add-Type -AssemblyName System.Drawing; $img = [System.Windows.Forms.Clipboard]::GetImage(); if ($img -ne $null) { $img.Save('` + escapedTmpPath + `', [System.Drawing.Imaging.ImageFormat]::Png) }`
 	cmd := exec.Command("powershell", "-NoProfile", "-Command", script)
 	if err := cmd.Run(); err != nil {
 		return nil, nil

internal/tools/bash_tool_test.go

@@ -125,6 +125,9 @@ func TestBashToolDescribesHostShellSyntax(t *testing.T) {
 		if !strings.Contains(description, "cmd.exe") || !strings.Contains(description, "cwd") {
 			t.Fatalf("expected Windows cmd.exe and cwd guidance in bash description, got %q", description)
 		}
+		if !strings.Contains(description, "double quotes") || !strings.Contains(description, `--jq ".a | b"`) {
+			t.Fatalf("expected the double-quote metacharacter rule in bash description, got %q", description)
+		}
 		return
 	}
 	if !strings.Contains(description, "/bin/sh") {

internal/tools/exec_command_test.go

@@ -501,10 +501,11 @@ func TestCollectRespectsDeadlineUnderContinuousOutput(t *testing.T) {
 	elapsed := time.Since(start)
 
 	// Generous slack over `wait` for scheduling jitter under a continuously
-	// writing goroutine — this must stay a small multiple of wait, not
-	// "however long the writer keeps going" (which is what the bug produced:
-	// this test would hang past the 30s test timeout without the fix).
-	if elapsed > 3*wait {
+	// writing goroutine (worse on Windows CI under load). This must stay a
+	// small multiple of wait, not "however long the writer keeps going"
+	// (which is what the bug produced: this test would hang past the 30s
+	// test timeout without the fix).
+	if elapsed > 5*wait {
 		t.Fatalf("collect took %v under continuous output, want close to the %v deadline", elapsed, wait)
 	}
 }

internal/tools/shell_runtime.go

@@ -37,7 +37,7 @@ func detectShellRuntime(goos string) shellRuntime {
 func shellGuidanceForGOOS(goos string) string {
 	runtime := detectShellRuntime(goos)
 	if goos == "windows" {
-		return "Uses " + runtime.Syntax + " syntax on Windows; prefer cwd over cd when changing directories."
+		return "Uses " + runtime.Syntax + " syntax on Windows; prefer cwd over cd when changing directories. To include | & > < or other metacharacters in an argument value, wrap the value in double quotes (e.g. --jq \".a | b\"); single quotes do not protect metacharacters in cmd.exe."
 	}
 	guidance := "Uses " + runtime.Syntax + " syntax."
 	if goos == "darwin" {