Fix alt modifier ignored in ANSI_SEQUENCES_KEYS tuple branch

src/textual/_xterm_parser.py

@@ -374,7 +374,10 @@ def _sequence_to_key_events(
             # If the sequence mapped to a tuple, then it's values from the
             # `Keys` enum. Raise key events from what we find in the tuple.
             for key in keys:
-                yield events.Key(key.value, sequence if len(sequence) == 1 else None)
+                key_name = key.value
+                if alt:
+                    key_name = f"alt+{key_name}"
+                yield events.Key(key_name, sequence if len(sequence) == 1 else None)
             return
         # If keys is a string, the intention is that it's a mapping to a
         # character, which should really be treated as the sequence for the

tests/test_xterm_parser.py

@@ -191,6 +191,8 @@ def test_double_escape(parser):
         ("\x1b[65;4u", "alt+shift+a"),
         ("\x1bA", "alt+shift+a"),
         ("\x1b[120;7u", "alt+ctrl+x"),
+        ("\x1b\r", "alt+enter"),
+        ("\x1b ", "alt+space"),
     ],
 )
 def test_keys(parser, sequence: str, key: str) -> None: