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fix(flags): load definitions from a cache provider without a secret key #1039

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fix(flags): load definitions from a cache provider without a secret key #1039

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5 changes: 5 additions & 0 deletions .sampo/changesets/load-flags-from-cache-provider-without-key.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
pypi/posthog: patch
---

Load feature flag definitions from a `flag_definition_cache_provider` when no `secret_key` is set, so local evaluation works with a cache provider alone.
12 changes: 9 additions & 3 deletions posthog/client.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3479,6 +3479,12 @@ def _fetch_feature_flags_from_api(self):

self._last_feature_flag_poll = datetime.now(tz=timezone.utc)

def _can_load_feature_flags(self) -> bool:
return (
bool(self.personal_api_key)
or self._flag_definition_cache_provider is not None
)

def load_feature_flags(self):
"""
Load feature flags for local evaluation.
Expand All @@ -3497,7 +3503,7 @@ def load_feature_flags(self):
self._property_matching_version = 1
return

if not self.personal_api_key:
if not self._can_load_feature_flags():

@dustinbyrne dustinbyrne Oct 8, 2026

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[P2] Configuration docs omit provider-only polling eligibility

The constructor and module configuration docs (posthog/client.py:793–796 and posthog/__init__.py:365–368) describe enable_local_evaluation polling when a personal API key is configured. This patch also permits loading with a provider alone and, by default, starts background refresh after loading (client.py:3482–3486,3515–3525).

The existing description is incomplete rather than wholly false. Provider-only clients previously returned before poller creation; the changed eligibility check makes this lifecycle distinction relevant.

Consider documenting that either privileged configuration or a cache provider permits definition loading, that provider refreshes consult its fetch decision, and that enable_local_evaluation=False suppresses background polling without preventing explicit or first-use hydration.

Verification is a static comparison of these descriptions against the eligibility predicate and poller-start condition. This documentation-only recommendation does not require an automated behavioral regression.

self.log.warning(
"[FEATURE FLAGS] You have to specify a secret_key to use feature flags."
)
Expand Down Expand Up @@ -4007,7 +4013,7 @@ def _locally_evaluate_flag(
device_id: Optional[str] = None,
) -> tuple[Optional[FlagValue], _LocalEvaluationSnapshot]:
"""Return the local value and its definitions for consistent payload lookup."""
if self.feature_flags is None and self.personal_api_key:
if self.feature_flags is None and self._can_load_feature_flags():
self.load_feature_flags()
response = None

Expand Down Expand Up @@ -4734,7 +4740,7 @@ def _get_all_flags_and_payloads_locally(
person_properties = person_properties or {}
group_properties = group_properties or {}

if self.feature_flags is None and self.personal_api_key:
if self.feature_flags is None and self._can_load_feature_flags():
self.load_feature_flags()

flags: dict[str, FlagValue] = {}
Expand Down
50 changes: 50 additions & 0 deletions posthog/test/test_flag_definition_cache.py
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Expand Up @@ -10,6 +10,8 @@
from typing import Optional
from unittest import mock

from parameterized import parameterized

from posthog.client import Client
from posthog.flag_definition_cache import (
FlagDefinitionCacheData,
Expand Down Expand Up @@ -155,6 +157,54 @@ def test_uses_cached_data_when_should_fetch_returns_false(self, mock_get):

client.join()

@parameterized.expand(
[
("explicit_load", lambda client: client.load_feature_flags()),
(
"lazy_load_on_first_evaluation",
lambda client: client.get_feature_flag(
"rolled-out-flag", "some-user", only_evaluate_locally=True
),
),
]
)
@mock.patch("posthog.client.get")
def test_loads_from_cache_provider_without_secret_key(self, _name, load, mock_get):
self.cache_provider.should_fetch_return_value = False
self.cache_provider.stored_data = {
"flags": [
{
"key": "rolled-out-flag",
"active": True,
"filters": {
"groups": [{"properties": [], "rollout_percentage": 100}]
},
}
],
"group_type_mapping": {},
"cohorts": {},
}
client = Client(
FAKE_TEST_API_KEY,
flag_definition_cache_provider=self.cache_provider,
sync_mode=True,
enable_local_evaluation=False,
)

load(client)

mock_get.assert_not_called()
self.assertEqual(
[flag["key"] for flag in client.feature_flags], ["rolled-out-flag"]
)
self.assertTrue(
client.get_feature_flag(
"rolled-out-flag", "some-user", only_evaluate_locally=True
)
)

client.join()

@mock.patch("posthog.client.get")
def test_fetches_from_api_when_should_fetch_returns_true(self, mock_get):
"""When should_fetch returns True, fetch from API."""
Expand Down
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