diff --git a/scripts/localize_changes.py b/scripts/localize_changes.py
index 9b9bcd0b8248..2930e5efb61f 100644
--- a/scripts/localize_changes.py
+++ b/scripts/localize_changes.py
@@ -28,7 +28,7 @@
     r'(?P<key>"(?:\\.|[^"\\])*")'
 
 )
-SWIFT_DEFAULT = re.compile(r'defaultValue\s*:\s*(?P<value>"(?:\\.|[^"\\])*")')
+SWIFT_DEFAULT = re.compile(r'defaultValue\s*:\s*(?P<value>"""\n[\s\S]*?\n[ \t]*"""|"(?:\\.|[^"\\])*")')
 SWIFT_COMMENT = re.compile(r'comment\s*:\s*(?P<comment>"(?:\\.|[^"\\])*")')
 WEB_LOCALES = re.compile(r"export\s+const\s+locales\s*=\s*\[(?P<body>[\s\S]*?)\]\s*as\s+const")
 QUOTED = re.compile(r'"((?:\\.|[^"\\])*)"|\'((?:\\.|[^\'\\])*)\'')
@@ -107,9 +107,12 @@ def base_text(root: Path, base: str, path: str) -> str:
 
 
 def decode_swift_string(literal: str) -> str:
-    if not (literal.startswith('"') and literal.endswith('"')):
+    if literal.startswith('"""'):
+        value = multiline_swift_body(literal)
+    elif literal.startswith('"') and literal.endswith('"'):
+        value = literal[1:-1]
+    else:
         raise ValueError("unsupported Swift string literal")
-    value = literal[1:-1]
     if "\\(" in value:
         raise ValueError("interpolated defaultValue requires manual catalog review")
     result: list[str] = []
@@ -128,12 +131,38 @@ def decode_swift_string(literal: str) -> str:
     return "".join(result)
 
 
+def multiline_swift_body(literal: str) -> str:
+    """Strip a multi-line literal's delimiters and the closing delimiter's indentation, as Swift does."""
+    lines = literal.split("\n")
+    indent = lines[-1][: -len('"""')]
+    if lines[0] != '"""' or indent.strip():
+        raise ValueError("unsupported Swift string literal")
+    body = []
+    for line in lines[1:-1]:
+        if line.strip() and not line.startswith(indent):
+            raise ValueError("unsupported Swift string literal")
+        if line.endswith("\\"):
+            raise ValueError("unsupported Swift escape in defaultValue")
+        body.append(line[len(indent):] if line.strip() else "")
+    return "\n".join(body)
+
+
 def swift_call_suffix(text: str, start: int) -> str:
     """Read through the closing call parenthesis, respecting nested calls and strings."""
     depth = 1
     quoted = escaped = False
+    skip = 0
     for index in range(start, len(text)):
         char = text[index]
+        if skip:
+            skip -= 1
+            continue
+        if not quoted and text.startswith('"""', index):
+            end = text.find('"""', index + 3)
+            if end < 0:
+                return ""
+            skip = end + 2 - index
+            continue
         if quoted:
             if escaped:
                 escaped = False
diff --git a/tests/test_localize_changes.py b/tests/test_localize_changes.py
index 0c0b117879d2..745ff85300b5 100644
--- a/tests/test_localize_changes.py
+++ b/tests/test_localize_changes.py
@@ -59,6 +59,20 @@ def test_key_only_call_cannot_steal_next_default(self):
         self.assertEqual({key: value.source for key, value in messages.items()}, {"other": "Other"})
         self.assertTrue(any("cannot safely prepare" in item for item in attention))
 
+    def test_multiline_default_is_read_whole_and_deindented(self):
+        source = (
+            'let usage = String(localized: "cli.help", defaultValue: """\n'
+            '        Usage: cmux thing\n'
+            '\n'
+            '          --json  Output JSON\n'
+            '        """)\n'
+            'let next = String(localized: "cli.next", defaultValue: "Next")'
+        )
+        messages, attention = MODULE.parse_swift_messages("CLI/Thing.swift", source)
+        self.assertEqual(messages["cli.help"].source, "Usage: cmux thing\n\n  --json  Output JSON")
+        self.assertEqual(messages["cli.next"].source, "Next")
+        self.assertEqual(attention, [])
+
     def test_import_validates_all_catalog_locale_groups_before_writing(self):
         with tempfile.TemporaryDirectory() as directory:
             root = Path(directory)