diff --git a/features/eval.feature b/features/eval.feature
index ba4f2f29..b7e94d47 100644
--- a/features/eval.feature
+++ b/features/eval.feature
@@ -333,3 +333,25 @@ Feature: Evaluating PHP code and files.
       Args: arg1 arg2
       """
 
+  Scenario: Eval-file with STDIN should work with alias groups
+    Given a WP installation in 'site1'
+    And a WP installation in 'site2'
+    And a wp-cli.yml file:
+      """
+      @group:
+        - @site1
+        - @site2
+      @site1:
+        path: site1
+      @site2:
+        path: site2
+      """
+    And a stdin-test.php file:
+      """
+      <?php
+      echo "Executed from STDIN\n";
+      """
+
+    When I run `cat stdin-test.php | wp @group eval-file -`
+    Then STDOUT should match /Executed from STDIN.*Executed from STDIN/s
+
diff --git a/src/EvalFile_Command.php b/src/EvalFile_Command.php
index e83da319..4e96e3be 100644
--- a/src/EvalFile_Command.php
+++ b/src/EvalFile_Command.php
@@ -11,6 +11,24 @@ class EvalFile_Command extends WP_CLI_Command {
 	 */
 	const SHEBANG_PATTERN = '/^(#!.*)$/m';
 
+	/**
+	 * Cache for STDIN contents to support alias groups.
+	 *
+	 * When using alias groups, the same command is executed multiple times
+	 * in separate processes. STDIN can only be read once, so we cache it
+	 * in a temporary file that persists across processes.
+	 *
+	 * @var string|null
+	 */
+	private static $stdin_cache = null;
+
+	/**
+	 * Temporary file path for STDIN cache.
+	 *
+	 * @var string|null
+	 */
+	private static $stdin_cache_file = null;
+
 	/**
 	 * Loads and executes a PHP file.
 	 *
@@ -96,7 +114,57 @@ private static function execute_eval( $file, $positional_args, $use_include ) {
 		unset( $positional_args );
 
 		if ( '-' === $file ) {
-			eval( '?>' . file_get_contents( 'php://stdin' ) );
+			// Cache STDIN contents to support alias groups.
+			// When using alias groups, each site runs in a separate process,
+			// but they all share the same STDIN. Once STDIN is read, it's consumed.
+			// We cache it in a temporary file that persists across processes.
+			if ( null === self::$stdin_cache ) {
+				// Get a unique identifier for the cache file
+				// Use parent PID on Unix-like systems for sharing across child processes
+				// On Windows, this feature may have limitations due to lack of posix_getppid()
+				if ( function_exists( 'posix_getppid' ) ) {
+					$cache_id = posix_getppid();
+				} else {
+					// On Windows or systems without POSIX, use an environment variable if available
+					// or fall back to current PID (which won't share across processes)
+					$cache_id = getenv( 'WP_CLI_STDIN_CACHE_ID' ) ?: getmypid();
+				}
+				self::$stdin_cache_file = sys_get_temp_dir() . '/wp-cli-eval-stdin-' . $cache_id . '.php';
+
+				// Check if cache file already exists (created by a previous subprocess)
+				if ( file_exists( self::$stdin_cache_file ) ) {
+					$stdin_contents = file_get_contents( self::$stdin_cache_file );
+					if ( false === $stdin_contents ) {
+						WP_CLI::error( 'Failed to read from STDIN cache file.' );
+					}
+					self::$stdin_cache = (string) $stdin_contents;
+
+					// Clean up old cache files (older than 1 hour) to prevent accumulation
+					self::cleanup_old_cache_files();
+				} else {
+					// First process: read from STDIN and cache it
+					$stdin_contents = file_get_contents( 'php://stdin' );
+					if ( false === $stdin_contents ) {
+						WP_CLI::error( 'Failed to read from STDIN.' );
+					}
+					self::$stdin_cache = (string) $stdin_contents;
+
+					// Save to cache file for subsequent processes
+					$write_result = file_put_contents( self::$stdin_cache_file, self::$stdin_cache );
+					if ( false === $write_result ) {
+						WP_CLI::error( 'Failed to write STDIN cache file.' );
+					}
+
+					// Clean up old cache files (older than 1 hour) to prevent accumulation
+					self::cleanup_old_cache_files();
+
+					// Note: We intentionally don't clean up the current cache file immediately.
+					// If we delete it in the shutdown function, subsequent child processes
+					// won't be able to read it. The cleanup_old_cache_files() method handles
+					// removal of stale cache files.
+				}
+			}
+			eval( '?>' . self::$stdin_cache );
 		} elseif ( $use_include ) {
 			include $file;
 		} else {
@@ -113,4 +181,33 @@ private static function execute_eval( $file, $positional_args, $use_include ) {
 			eval( '?>' . $file_contents );
 		}
 	}
+
+	/**
+	 * Clean up old STDIN cache files to prevent accumulation.
+	 *
+	 * Removes cache files older than 1 hour from the system temp directory.
+	 * This is called when creating or reading a cache file to ensure stale
+	 * files don't accumulate if processes terminate unexpectedly.
+	 */
+	private static function cleanup_old_cache_files() {
+		$temp_dir      = sys_get_temp_dir();
+		$cache_pattern = $temp_dir . '/wp-cli-eval-stdin-*.php';
+		$cache_files   = glob( $cache_pattern );
+		$one_hour_ago  = time() - 3600;
+
+		if ( ! empty( $cache_files ) ) {
+			foreach ( $cache_files as $cache_file ) {
+				// Skip the current cache file
+				if ( $cache_file === self::$stdin_cache_file ) {
+					continue;
+				}
+
+				// Delete files older than 1 hour
+				$file_time = filemtime( $cache_file );
+				if ( false !== $file_time && $file_time < $one_hour_ago ) {
+					@unlink( $cache_file );
+				}
+			}
+		}
+	}
 }