From 0240baa357522654026e4aa04c716d209f79b704 Mon Sep 17 00:00:00 2001
From: arasovic <me@arasmehmet.com>
Date: Tue, 31 Mar 2026 19:42:44 +0300
Subject: [PATCH] fix: strip orphaned think/reasoning tags from user-facing
 responses

Some models (e.g. Kimi K2.5 on Alibaba OpenAI-compatible endpoint)
emit reasoning text followed by a closing </think> without a matching
opening <think> tag.  The existing paired-tag regexes in
_strip_think_blocks() cannot match these orphaned tags, so </think>
leaks into user-facing responses on all platforms.

Add a catch-all regex that strips any remaining opening or closing
think/thinking/reasoning/REASONING_SCRATCHPAD tags after the existing
paired-block removal pass.

Closes #4285
---
 run_agent.py            |  1 +
 tests/test_run_agent.py | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/run_agent.py b/run_agent.py
index 13278d94c04..717c26b4a7d 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -1389,6 +1389,7 @@ class AIAgent:
         content = re.sub(r'<thinking>.*?</thinking>', '', content, flags=re.DOTALL | re.IGNORECASE)
         content = re.sub(r'<reasoning>.*?</reasoning>', '', content, flags=re.DOTALL)
         content = re.sub(r'<REASONING_SCRATCHPAD>.*?</REASONING_SCRATCHPAD>', '', content, flags=re.DOTALL)
+        content = re.sub(r'</?(?:think|thinking|reasoning|REASONING_SCRATCHPAD)>\s*', '', content, flags=re.IGNORECASE)
         return content
 
     def _looks_like_codex_intermediate_ack(
diff --git a/tests/test_run_agent.py b/tests/test_run_agent.py
index 7ea3a63fe23..aa74164a754 100644
--- a/tests/test_run_agent.py
+++ b/tests/test_run_agent.py
@@ -230,6 +230,27 @@ class TestStripThinkBlocks:
         assert "line1" not in result
         assert "visible" in result
 
+    def test_orphaned_closing_think_tag(self, agent):
+        result = agent._strip_think_blocks("some reasoning</think>actual answer")
+        assert "</think>" not in result
+        assert "actual answer" in result
+
+    def test_orphaned_closing_thinking_tag(self, agent):
+        result = agent._strip_think_blocks("reasoning</thinking>answer")
+        assert "</thinking>" not in result
+        assert "answer" in result
+
+    def test_orphaned_opening_think_tag(self, agent):
+        result = agent._strip_think_blocks("<think>orphaned reasoning without close")
+        assert "<think>" not in result
+
+    def test_mixed_orphaned_and_paired_tags(self, agent):
+        text = "stray</think><think>paired reasoning</think> visible"
+        result = agent._strip_think_blocks(text)
+        assert "</think>" not in result
+        assert "<think>" not in result
+        assert "visible" in result
+
 
 class TestExtractReasoning:
     def test_reasoning_field(self, agent):