diff --git a/news/changelog-1.9.md b/news/changelog-1.9.md
index 240630d15f0..8fc84d8a18a 100644
--- a/news/changelog-1.9.md
+++ b/news/changelog-1.9.md
@@ -3,7 +3,7 @@
 ## In this release
 
 - ([#14304](https://github.com/quarto-dev/quarto-cli/issues/14304)): Fix `quarto install tinytex` silently ignoring extraction failures. When archive extraction fails (e.g., `.tar.xz` on a system without `xz-utils`), the installer now reports a clear error instead of proceeding and failing with a confusing `NotFound` message.
-- ([#14367](https://github.com/quarto-dev/quarto-cli/issues/14367)): Fix Dart Sass invocation failing on enterprise Windows systems where Group Policy blocks `.bat` execution from `%TEMP%`. When the `safeWindowsExec` temp wrapper is blocked, Quarto now falls back to calling `sass.bat` directly.
+- ([#14367](https://github.com/quarto-dev/quarto-cli/issues/14367), [#14534](https://github.com/quarto-dev/quarto-cli/issues/14534)): Fix Dart Sass invocation failing on Windows when the user profile path contains `&` (e.g., `C:\Users\Tom & Jerry\`) and on enterprise systems where Group Policy blocks `.bat` execution from `%TEMP%`. Quarto now invokes the bundled `dart.exe` with `sass.snapshot` directly, bypassing `sass.bat` and `cmd.exe` entirely.
 - ([#14489](https://github.com/quarto-dev/quarto-cli/issues/14489)): Restore `--output-dir` support for `quarto preview` of single files when no `_quarto.yml` is present (e.g. R-package workspaces). Regression introduced in v1.9.18.
 
 ## In previous releases
diff --git a/src/core/dart-sass.ts b/src/core/dart-sass.ts
index 1d925889a06..1d08e2d68b9 100644
--- a/src/core/dart-sass.ts
+++ b/src/core/dart-sass.ts
@@ -1,20 +1,18 @@
 /*
  * dart-sass.ts
  *
- * Copyright (C) 2020-2022 Posit Software, PBC
+ * Copyright (C) 2020-2026 Posit Software, PBC
  */
 import { join } from "../deno_ral/path.ts";
 
 import { architectureToolsPath } from "./resources.ts";
 import { execProcess } from "./process.ts";
-import { ProcessResult } from "./process-types.ts";
 import { TempContext } from "./temp.ts";
 import { lines } from "./text.ts";
 import { debug, info } from "../deno_ral/log.ts";
 import { existsSync } from "../deno_ral/fs.ts";
 import { warnOnce } from "./log.ts";
 import { isWindows } from "../deno_ral/platform.ts";
-import { requireQuoting, safeWindowsExec } from "./windows.ts";
 
 export function dartSassInstallDir() {
   return architectureToolsPath("dart-sass");
@@ -60,17 +58,39 @@ export async function dartCompile(
  */
 export interface DartCommandOptions {
   /**
-   * Override the sass executable path.
-   * Primarily used for testing with spaced paths.
+   * Override the dart-sass install directory.
+   * Used for testing with non-standard paths (spaces, accented characters).
    */
-  sassPath?: string;
+  installDir?: string;
 }
 
-export async function dartCommand(
-  args: string[],
-  options?: DartCommandOptions,
-) {
-  const resolvePath = () => {
+/**
+ * Resolve the dart-sass command and its base arguments.
+ *
+ * On Windows, calls dart.exe + sass.snapshot directly instead of going
+ * through sass.bat. The bundled sass.bat is a thin wrapper generated by
+ * dart_cli_pkg that just runs:
+ *   "%SCRIPTPATH%\src\dart.exe" "%SCRIPTPATH%\src\sass.snapshot" %arguments%
+ *
+ * Template source:
+ *   https://github.com/google/dart_cli_pkg/blob/main/lib/src/templates/standalone/executable.bat.mustache
+ * Upstream issue to ship standalone .exe instead of .bat + dart.exe:
+ *   https://github.com/google/dart_cli_pkg/issues/67
+ *
+ * Bypassing sass.bat avoids multiple .bat file issues on Windows:
+ * - Deno quoting bugs with spaced paths (#13997)
+ * - cmd.exe OEM code page misreading UTF-8 accented paths (#14267)
+ * - Enterprise group policy blocking .bat execution (#6651)
+ */
+function resolveSassCommand(options?: DartCommandOptions): {
+  cmd: string;
+  baseArgs: string[];
+} {
+  const installDir = options?.installDir;
+  if (installDir == null) {
+    // Only check env var override when no explicit installDir is provided.
+    // If QUARTO_DART_SASS doesn't exist on disk, fall through to use the
+    // bundled dart-sass at the default architectureToolsPath.
     const dartOverrideCmd = Deno.env.get("QUARTO_DART_SASS");
     if (dartOverrideCmd) {
       if (!existsSync(dartOverrideCmd)) {
@@ -78,77 +98,51 @@ export async function dartCommand(
           `Specified QUARTO_DART_SASS does not exist, using built in dart sass.`,
         );
       } else {
-        return dartOverrideCmd;
+        return { cmd: dartOverrideCmd, baseArgs: [] };
       }
     }
+  }
 
-    const command = isWindows ? "sass.bat" : "sass";
-    return architectureToolsPath(join("dart-sass", command));
-  };
-  const sass = options?.sassPath ?? resolvePath();
+  const sassDir = installDir ?? architectureToolsPath("dart-sass");
 
-  // Process result helper (shared by Windows and non-Windows paths)
-  const processResult = (result: ProcessResult): string | undefined => {
-    if (result.success) {
-      if (result.stderr) {
-        info(result.stderr);
-      }
-      return result.stdout;
-    } else {
-      debug(`[DART path]   : ${sass}`);
-      debug(`[DART args]   : ${args.join(" ")}`);
-      debug(`[DART stdout] : ${result.stdout}`);
-      debug(`[DART stderr] : ${result.stderr}`);
-
-      const errLines = lines(result.stderr || "");
-      // truncate the last 2 lines (they include a pointer to the temp file containing
-      // all of the concatenated sass, which is more or less incomprehensible for users.
-      const errMsg = errLines.slice(0, errLines.length - 2).join("\n");
-      throw new Error("Theme file compilation failed:\n\n" + errMsg);
-    }
-  };
-
-  // On Windows, use safeWindowsExec to handle paths with spaces
-  // (e.g., when Quarto is installed in C:\Program Files\)
-  // See https://github.com/quarto-dev/quarto-cli/issues/13997
   if (isWindows) {
-    const quoted = requireQuoting([sass, ...args]);
-    const result = await safeWindowsExec(
-      quoted.args[0],
-      quoted.args.slice(1),
-      (cmd: string[]) => {
-        return execProcess({
-          cmd: cmd[0],
-          args: cmd.slice(1),
-          stdout: "piped",
-          stderr: "piped",
-        });
-      },
-    );
-    if (result.success) {
-      return processResult(result);
-    }
-
-    // safeWindowsExec failed — fall back to direct execution (v1.8 behavior).
-    // Enterprise environments may block .bat execution from %TEMP% via
-    // Group Policy / AppLocker, causing the temp wrapper to fail.
-    // See https://github.com/quarto-dev/quarto-cli/issues/14367
-    debug("[DART] safeWindowsExec failed, falling back to direct execution");
-    const directResult = await execProcess({
-      cmd: sass,
-      args,
-      stdout: "piped",
-      stderr: "piped",
-    });
-    return processResult(directResult);
+    return {
+      cmd: join(sassDir, "src", "dart.exe"),
+      baseArgs: [join(sassDir, "src", "sass.snapshot")],
+    };
   }
 
-  // Non-Windows: direct execution
+  return { cmd: join(sassDir, "sass"), baseArgs: [] };
+}
+
+export async function dartCommand(
+  args: string[],
+  options?: DartCommandOptions,
+) {
+  const { cmd, baseArgs } = resolveSassCommand(options);
+
   const result = await execProcess({
-    cmd: sass,
-    args,
+    cmd,
+    args: [...baseArgs, ...args],
     stdout: "piped",
     stderr: "piped",
   });
-  return processResult(result);
+
+  if (result.success) {
+    if (result.stderr) {
+      info(result.stderr);
+    }
+    return result.stdout;
+  } else {
+    debug(`[DART cmd]    : ${cmd}`);
+    debug(`[DART args]   : ${[...baseArgs, ...args].join(" ")}`);
+    debug(`[DART stdout] : ${result.stdout}`);
+    debug(`[DART stderr] : ${result.stderr}`);
+
+    const errLines = lines(result.stderr || "");
+    // truncate the last 2 lines (they include a pointer to the temp file containing
+    // all of the concatenated sass, which is more or less incomprehensible for users.
+    const errMsg = errLines.slice(0, errLines.length - 2).join("\n");
+    throw new Error("Theme file compilation failed:\n\n" + errMsg);
+  }
 }
diff --git a/tests/unit/dart-sass.test.ts b/tests/unit/dart-sass.test.ts
index 0e37241353c..6d5d3de86b9 100644
--- a/tests/unit/dart-sass.test.ts
+++ b/tests/unit/dart-sass.test.ts
@@ -2,7 +2,10 @@
  * dart-sass.test.ts
  *
  * Tests for dart-sass functionality.
- * Validates fix for https://github.com/quarto-dev/quarto-cli/issues/13997
+ * Validates fixes for:
+ *   https://github.com/quarto-dev/quarto-cli/issues/13997 (spaced paths)
+ *   https://github.com/quarto-dev/quarto-cli/issues/14267 (accented paths)
+ *   https://github.com/quarto-dev/quarto-cli/issues/6651  (enterprise .bat blocking)
  *
  * Copyright (C) 2020-2025 Posit Software, PBC
  */
@@ -13,46 +16,53 @@ import { isWindows } from "../../src/deno_ral/platform.ts";
 import { join } from "../../src/deno_ral/path.ts";
 import { dartCommand, dartSassInstallDir } from "../../src/core/dart-sass.ts";
 
+/**
+ * Helper: create a junction to the real dart-sass install dir at `targetDir`.
+ * Returns cleanup function to remove the junction.
+ */
+async function createDartSassJunction(targetDir: string) {
+  const sassInstallDir = dartSassInstallDir();
+  const result = await new Deno.Command("cmd", {
+    args: ["/c", "mklink", "/J", targetDir, sassInstallDir],
+  }).output();
+
+  if (!result.success) {
+    const stderr = new TextDecoder().decode(result.stderr);
+    throw new Error(`Failed to create junction: ${stderr}`);
+  }
+
+  return async () => {
+    await new Deno.Command("cmd", {
+      args: ["/c", "rmdir", targetDir],
+    }).output();
+  };
+}
+
 // Test that dartCommand handles spaced paths on Windows (issue #13997)
-// The bug only triggers when BOTH the executable path AND arguments contain spaces.
+// dart.exe is called directly, bypassing sass.bat and its quoting issues.
 unitTest(
   "dartCommand - handles spaced paths on Windows (issue #13997)",
   async () => {
-    // Create directories with spaces for both sass and file arguments
     const tempBase = Deno.makeTempDirSync({ prefix: "quarto_test_" });
     const spacedSassDir = join(tempBase, "Program Files", "dart-sass");
     const spacedProjectDir = join(tempBase, "My Project");
-    const sassInstallDir = dartSassInstallDir();
+
+    let removeJunction: (() => Promise<void>) | undefined;
 
     try {
-      // Create directories
       Deno.mkdirSync(join(tempBase, "Program Files"), { recursive: true });
       Deno.mkdirSync(spacedProjectDir, { recursive: true });
 
-      // Create junction (Windows directory symlink) to actual dart-sass
-      const junctionResult = await new Deno.Command("cmd", {
-        args: ["/c", "mklink", "/J", spacedSassDir, sassInstallDir],
-      }).output();
+      removeJunction = await createDartSassJunction(spacedSassDir);
 
-      if (!junctionResult.success) {
-        const stderr = new TextDecoder().decode(junctionResult.stderr);
-        throw new Error(`Failed to create junction: ${stderr}`);
-      }
-
-      // Create test SCSS file in spaced path (args with spaces)
       const inputScss = join(spacedProjectDir, "test style.scss");
       const outputCss = join(spacedProjectDir, "test style.css");
       Deno.writeTextFileSync(inputScss, "body { color: red; }");
 
-      const spacedSassPath = join(spacedSassDir, "sass.bat");
-
-      // This is the exact bug scenario: spaced exe path + spaced args
-      // Without the fix, this fails with "C:\...\Program" not recognized
       const result = await dartCommand([inputScss, outputCss], {
-        sassPath: spacedSassPath,
+        installDir: spacedSassDir,
       });
 
-      // Verify compilation succeeded (no stdout expected for file-to-file compilation)
       assert(
         result === undefined || result === "",
         "Sass compile should succeed (no stdout for file-to-file compilation)",
@@ -62,14 +72,103 @@ unitTest(
         "Output CSS file should be created",
       );
     } finally {
-      // Cleanup: remove junction first (rmdir for junctions), then temp directory
       try {
-        await new Deno.Command("cmd", {
-          args: ["/c", "rmdir", spacedSassDir],
-        }).output();
+        if (removeJunction) await removeJunction();
+        await Deno.remove(tempBase, { recursive: true });
+      } catch (e) {
+        console.debug("Test cleanup failed:", e);
+      }
+    }
+  },
+  { ignore: !isWindows },
+);
+
+// Test that dartCommand handles ampersand in paths (issue #14534)
+// Windows user profile paths like C:\Users\Tom & Jerry\ broke dart-sass
+// because the temp .bat wrapper written by safeWindowsExec was split on `&`
+// by cmd.exe. Direct dart.exe invocation bypasses cmd.exe entirely.
+unitTest(
+  "dartCommand - handles ampersand in paths (issue #14534)",
+  async () => {
+    const tempBase = Deno.makeTempDirSync({ prefix: "quarto_test_" });
+    const ampSassDir = join(tempBase, "Tom & Jerry", "dart-sass");
+    const ampProjectDir = join(tempBase, "Tom & Jerry", "project");
+
+    let removeJunction: (() => Promise<void>) | undefined;
+
+    try {
+      Deno.mkdirSync(join(tempBase, "Tom & Jerry"), { recursive: true });
+      Deno.mkdirSync(ampProjectDir, { recursive: true });
+
+      removeJunction = await createDartSassJunction(ampSassDir);
+
+      const inputScss = join(ampProjectDir, "style.scss");
+      const outputCss = join(ampProjectDir, "style.css");
+      Deno.writeTextFileSync(inputScss, "body { color: green; }");
+
+      const result = await dartCommand([inputScss, outputCss], {
+        installDir: ampSassDir,
+      });
+
+      assert(
+        result === undefined || result === "",
+        "Sass compile should succeed with ampersand in path",
+      );
+      assert(
+        Deno.statSync(outputCss).isFile,
+        "Output CSS file should be created at ampersand path",
+      );
+    } finally {
+      try {
+        if (removeJunction) await removeJunction();
+        await Deno.remove(tempBase, { recursive: true });
+      } catch (e) {
+        console.debug("Test cleanup failed:", e);
+      }
+    }
+  },
+  { ignore: !isWindows },
+);
+
+// Test that dartCommand handles accented characters in paths (issue #14267)
+// Accented chars in user paths (e.g., C:\Users\Sébastien\) broke when
+// dart-sass was invoked through a .bat wrapper with UTF-8/OEM mismatch.
+unitTest(
+  "dartCommand - handles accented characters in paths (issue #14267)",
+  async () => {
+    const tempBase = Deno.makeTempDirSync({ prefix: "quarto_test_" });
+    const accentedSassDir = join(tempBase, "Sébastien", "dart-sass");
+    const accentedProjectDir = join(tempBase, "Sébastien", "project");
+
+    let removeJunction: (() => Promise<void>) | undefined;
+
+    try {
+      Deno.mkdirSync(join(tempBase, "Sébastien"), { recursive: true });
+      Deno.mkdirSync(accentedProjectDir, { recursive: true });
+
+      removeJunction = await createDartSassJunction(accentedSassDir);
+
+      const inputScss = join(accentedProjectDir, "style.scss");
+      const outputCss = join(accentedProjectDir, "style.css");
+      Deno.writeTextFileSync(inputScss, "body { color: blue; }");
+
+      const result = await dartCommand([inputScss, outputCss], {
+        installDir: accentedSassDir,
+      });
+
+      assert(
+        result === undefined || result === "",
+        "Sass compile should succeed with accented path",
+      );
+      assert(
+        Deno.statSync(outputCss).isFile,
+        "Output CSS file should be created at accented path",
+      );
+    } finally {
+      try {
+        if (removeJunction) await removeJunction();
         await Deno.remove(tempBase, { recursive: true });
       } catch (e) {
-        // Best effort cleanup - log for debugging if it fails
         console.debug("Test cleanup failed:", e);
       }
     }