From df282a6e4d01c0ca37d418d6c48cbc51db9c91b4 Mon Sep 17 00:00:00 2001
From: Luan Taraschi <130802253+luantaraschi@users.noreply.github.com>
Date: Fri, 30 Oct 2026 11:29:22 -0300
Subject: [PATCH] fix(flags): stringify regex properties as compact JSON

Local regex and not_regex matching called str() on the property.
---
 .../local-eval-regex-json-string.md           |  5 +++++
 posthog/feature_flags.py                      |  4 +++-
 posthog/test/test_feature_flags.py            | 19 +++++++++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 .sampo/changesets/local-eval-regex-json-string.md

diff --git a/.sampo/changesets/local-eval-regex-json-string.md b/.sampo/changesets/local-eval-regex-json-string.md
new file mode 100644
index 00000000..d7f44458
--- /dev/null
+++ b/.sampo/changesets/local-eval-regex-json-string.md
@@ -0,0 +1,5 @@
+---
+posthog: patch
+---
+
+Stringify non-string properties as compact JSON for local `regex` and `not_regex` matching, so booleans, lists, and objects match the same way they do on the flags service.
diff --git a/posthog/feature_flags.py b/posthog/feature_flags.py
index e0ffda65..cfe847fb 100644
--- a/posthog/feature_flags.py
+++ b/posthog/feature_flags.py
@@ -1264,7 +1264,9 @@ def compute_exact_match(value, override_value):
         return matched
 
     if operator in ("regex", "not_regex"):
-        property_string = "null" if override_value is None else str(override_value)
+        property_string = _value_to_string(
+            override_value, UnresolvedFlagReason.MISSING_CONTEXT
+        )
         regex_match = _match_regex(str(value), property_string)
         if regex_match is None:
             return False
diff --git a/posthog/test/test_feature_flags.py b/posthog/test/test_feature_flags.py
index 14a1ed18..9c79813e 100644
--- a/posthog/test/test_feature_flags.py
+++ b/posthog/test/test_feature_flags.py
@@ -5871,6 +5871,25 @@ def test_match_properties_regex(self):
 
         self.assertFalse(match_property(property_d, {"key": "value"}))
 
+    @parameterized.expand(
+        [
+            ("list", r"\[1,2\]", [1, 2], True),
+            ("bool", "^true$", True, True),
+            ("python_bool_spelling", "True", True, False),
+            ("object", r'^\{"a":1,"b":\[null\]\}$', {"b": [None], "a": 1}, True),
+            ("python_object_spelling", "'a'", {"a": 1}, False),
+        ]
+    )
+    def test_regex_stringifies_non_string_properties_as_compact_json(
+        self, _name, pattern, property_value, expected
+    ):
+        regex = self.property("key", pattern, "regex")
+        not_regex = self.property("key", pattern, "not_regex")
+        self.assertEqual(expected, match_property(regex, {"key": property_value}))
+        self.assertEqual(
+            not expected, match_property(not_regex, {"key": property_value})
+        )
+
     def test_match_properties_math_operators(self):
         property_a = self.property(key="key", value=1, operator="gt")
         self.assertTrue(match_property(property_a, {"key": 2}))