machines-6657 · Oct 3, 2026
diff --git a/src/semver/version.py b/src/semver/version.py
@@ -304,12 +304,29 @@ def _increment_prerelease(string: str) -> str:
         """
         match = Version._LAST_PRERELEASE.search(string)
         if match:
-            next_ = str(int(match.group(2)) + 1)
+            next_ = Version._increment_digits(match.group(2))
             string = match.group(1) + next_ if match.group(1) else next_
         else:
             string += ".0"
         return string
 
+    @staticmethod
+    def _increment_digits(digits: str) -> str:
+        """Increment an ASCII decimal string without converting it to an int."""
+        if not digits.isascii():
+            # Preserve the historical handling of non-ASCII digits accepted
+            # by direct construction; parsed SemVer identifiers are ASCII.
+            return str(int(digits) + 1)
+
+        # Match int() normalization; the build caller preserves padding.
+        result = list(digits.lstrip("0") or "0")
+        for index in range(len(result) - 1, -1, -1):
+            if result[index] != "9":
+                result[index] = chr(ord(result[index]) + 1)
+                return "".join(result)
+            result[index] = "0"
+        return "1" + "".join(result)
+
     @staticmethod
     def _increment_string(string: str) -> str:
         """
@@ -323,7 +340,7 @@ def _increment_string(string: str) -> str:
         """
         match = Version._LAST_NUMBER.search(string)
         if match:
-            next_ = str(int(match.group(1)) + 1)
+            next_ = Version._increment_digits(match.group(1))
             start, end = match.span(1)
             string = string[: max(end - len(next_), start)] + next_ + string[end:]
         return string

diff --git a/tests/test_bump_long_identifiers.py b/tests/test_bump_long_identifiers.py
@@ -0,0 +1,75 @@
+import sys
+
+import pytest
+
+from semver import Version
+
+
+def test_bump_prerelease_with_long_numeric_identifier():
+    identifier = "9" * 5000
+    version = f"1.2.3-rc.{identifier}"
+
+    assert Version.is_valid(version)
+    assert str(Version.parse(version).bump_prerelease()) == f"1.2.3-rc.1{'0' * 5000}"
+
+
+def test_bump_build_with_long_numeric_identifier():
+    identifier = "9" * 5000
+    version = f"1.2.3+build.{identifier}"
+
+    assert Version.is_valid(version)
+    assert str(Version.parse(version).bump_build()) == f"1.2.3+build.1{'0' * 5000}"
+
+
+def test_bump_build_preserves_leading_zeroes_when_carrying():
+    version = Version.parse("1.2.3+build.0099")
+
+    assert str(version.bump_build()) == "1.2.3+build.0100"
+
+
+@pytest.mark.parametrize(
+    "prerelease, expected",
+    [("0009", "10"), ("rc.0099", "rc.100"), ("rc.0000", "rc.1")],
+)
+def test_bump_prerelease_normalizes_constructor_leading_zeroes(prerelease, expected):
+    version = Version(1, 2, 3, prerelease=prerelease)
+
+    assert version.bump_prerelease().prerelease == expected
+    assert version.prerelease == prerelease
+
+
+@pytest.mark.parametrize(
+    "part, identifier, expected",
+    [
+        ("prerelease", "rc.\u0660\u0660\u0669\u0669", "rc.100"),
+        ("build", "build.\u0660\u0660\u0669\u0669", "build.\u0660100"),
+    ],
+)
+def test_bump_preserves_constructor_unicode_digit_behavior(part, identifier, expected):
+    version = Version(1, 2, 3, **{part: identifier})
+
+    assert getattr(getattr(version, f"bump_{part}")(), part) == expected
+
+
+@pytest.mark.parametrize("part", ["prerelease", "build"])
+def test_bump_long_identifier_without_carry_does_not_change_int_limit(part):
+    identifier = "1" + "0" * 4999
+    version = Version.parse(f"1.2.3{'-' if part == 'prerelease' else '+'}{identifier}")
+    original_limit = (
+        sys.get_int_max_str_digits() if hasattr(sys, "get_int_max_str_digits") else None
+    )
+
+    bumped = getattr(version, f"bump_{part}")()
+
+    assert getattr(bumped, part) == "1" + "0" * 4998 + "1"
+    assert Version.is_valid(str(bumped))
+    assert getattr(version, part) == identifier
+    if original_limit is not None:
+        assert sys.get_int_max_str_digits() == original_limit
+
+
+def test_bump_long_build_preserves_all_leading_zeroes():
+    identifier = "0" * 5000
+    version = Version.parse(f"1.2.3+{identifier}")
+
+    assert version.bump_build().build == "0" * 4999 + "1"