From a88ad2eaec90241530476fdfcb11022a72c1e5d7 Mon Sep 17 00:00:00 2001
From: Cohen Karnell <7363269+ckarnell@users.noreply.github.com>
Date: Fri, 14 Aug 2026 09:31:02 -0400
Subject: [PATCH 1/2] fix(ai): honor a default_cache_ttl_seconds of 0

---
 posthog/ai/prompts.py           |  4 +++-
 posthog/test/ai/test_prompts.py | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/posthog/ai/prompts.py b/posthog/ai/prompts.py
index 0e5ef38b..c83483a4 100644
--- a/posthog/ai/prompts.py
+++ b/posthog/ai/prompts.py
@@ -173,7 +173,9 @@ def __init__(
                 failures are reported to PostHog error tracking via capture_exception().
         """
         self._default_cache_ttl_seconds = (
-            default_cache_ttl_seconds or DEFAULT_CACHE_TTL_SECONDS
+            default_cache_ttl_seconds
+            if default_cache_ttl_seconds is not None
+            else DEFAULT_CACHE_TTL_SECONDS
         )
         self._cache: Dict[PromptCacheKey, CachedPrompt] = {}
         self._has_warned_deprecation = False
diff --git a/posthog/test/ai/test_prompts.py b/posthog/test/ai/test_prompts.py
index 15d4b911..df9d9ed7 100644
--- a/posthog/test/ai/test_prompts.py
+++ b/posthog/test/ai/test_prompts.py
@@ -512,6 +512,26 @@ def test_use_custom_default_cache_ttl_from_constructor(
         prompts.get("test-prompt", with_metadata=False)
         self.assertEqual(mock_get.call_count, 2)
 
+    @patch("posthog.ai.prompts._get_session")
+    @patch("posthog.ai.prompts.time.time")
+    def test_default_cache_ttl_seconds_zero_disables_caching(
+        self, mock_time, mock_get_session
+    ):
+        """A default TTL of 0 should disable caching, matching the per-call option."""
+        mock_get = mock_get_session.return_value.get
+        mock_get.return_value = MockResponse(json_data=self.mock_prompt_response)
+        mock_time.return_value = 1000.0
+
+        posthog = self.create_mock_posthog()
+        prompts = Prompts(posthog, default_cache_ttl_seconds=0)
+
+        prompts.get("test-prompt", with_metadata=False)
+        self.assertEqual(mock_get.call_count, 1)
+
+        # No time has passed, and a TTL of 0 still means every read refetches.
+        prompts.get("test-prompt", with_metadata=False)
+        self.assertEqual(mock_get.call_count, 2)
+
     @patch("posthog.ai.prompts._get_session")
     def test_url_encode_prompt_names_with_special_characters(self, mock_get_session):
         """Should URL-encode prompt names with special characters."""

From c8946e99318f9afe818da4007941505e0551d3fc Mon Sep 17 00:00:00 2001
From: Manoel Aranda Neto <marandaneto@gmail.com>
Date: Sat, 15 Aug 2026 08:21:28 +0200
Subject: [PATCH 2/2] chore: add changeset for prompt cache TTL fix

---
 .sampo/changesets/gallant-queen-vainamoinen.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .sampo/changesets/gallant-queen-vainamoinen.md

diff --git a/.sampo/changesets/gallant-queen-vainamoinen.md b/.sampo/changesets/gallant-queen-vainamoinen.md
new file mode 100644
index 00000000..3b7bf481
--- /dev/null
+++ b/.sampo/changesets/gallant-queen-vainamoinen.md
@@ -0,0 +1,5 @@
+---
+pypi/posthog: patch
+---
+
+Honor `default_cache_ttl_seconds=0` in AI prompts so callers can disable default prompt caching.