From 354ffab61688140b1d000ab01116fc1f07517a53 Mon Sep 17 00:00:00 2001
From: Petrus Pennanen <petrus.pennanen@gmail.com>
Date: Sun, 27 Sep 2026 13:59:50 +0300
Subject: [PATCH] Strip reasoning whose opening tag never appeared ('</think>
 answer')

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 carwatch/grounding.py       | 11 +++++++++++
 tests/test_scaffold_leak.py | 17 +++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/carwatch/grounding.py b/carwatch/grounding.py
index 4999169..b3e03dd 100644
--- a/carwatch/grounding.py
+++ b/carwatch/grounding.py
@@ -52,6 +52,12 @@
 
 _THINK_BLOCK = re.compile(r"<(think|thinking|reasoning)>.*?</\1>",
                           re.IGNORECASE | re.DOTALL)
+# A reasoning block whose OPENING tag was never in the output: chat templates
+# that start the model inside <think> (Qwen3.6 on the VTA, 27 Sep 2026) make
+# it emit "...reasoning...</think> answer", or just "</think> answer" when the
+# reasoning went to a separate field. The paired pattern above cannot see it,
+# and the bare tag was posted to the room and handed to the voice.
+_THINK_CLOSE = re.compile(r"</(think|thinking|reasoning)>", re.IGNORECASE)
 _BULLET = re.compile(r"^\s*(?:[-*\u2022]|\d+[.)])\s+")
 
 
@@ -68,6 +74,11 @@ def strip_scaffold(text: str) -> str:
     if not text:
         return text
     cleaned = _THINK_BLOCK.sub("", text).strip()
+    closes = list(_THINK_CLOSE.finditer(cleaned))
+    if closes:
+        after = cleaned[closes[-1].end():].strip()
+        if after:
+            cleaned = after
     lines = cleaned.splitlines()
     i, dropping = 0, False
     while i < len(lines):
diff --git a/tests/test_scaffold_leak.py b/tests/test_scaffold_leak.py
index 5a0f1b6..7d978fd 100644
--- a/tests/test_scaffold_leak.py
+++ b/tests/test_scaffold_leak.py
@@ -58,5 +58,22 @@ def test_prompt_and_stripper_share_the_headings(self):
         self.assertIn(CANNOT_HEADING, p)
 
 
+
+class StrayThinkClose(unittest.TestCase):
+    """VTA 27 Sep: '</think>  Kuule, Petrus, ...' reached the room and the voice."""
+
+    def test_bare_closing_tag_is_dropped(self):
+        self.assertEqual(strip_scaffold("</think>  Kuule, Petrus."), "Kuule, Petrus.")
+
+    def test_reasoning_before_unopened_close_is_dropped(self):
+        self.assertEqual(strip_scaffold("The user greets me.\nI should reply.</think>\nHello Petrus!"),
+                         "Hello Petrus!")
+
+    def test_paired_block_still_works(self):
+        self.assertEqual(strip_scaffold("<think>hmm</think>Hi."), "Hi.")
+
+    def test_only_reasoning_is_not_emptied(self):
+        self.assertTrue(strip_scaffold("thinking only</think>").strip())
+
 if __name__ == "__main__":
     unittest.main()