diff --git a/api/core/workflow/nodes/llm/node.py b/api/core/workflow/nodes/llm/node.py
index be0675a0f2..6ca526919a 100644
--- a/api/core/workflow/nodes/llm/node.py
+++ b/api/core/workflow/nodes/llm/node.py
@@ -2,6 +2,8 @@ import base64
 import io
 import json
 import logging
+import os
+import re
 from collections.abc import Generator, Mapping, Sequence
 from typing import TYPE_CHECKING, Any, Optional, cast
 
@@ -96,6 +98,21 @@ if TYPE_CHECKING:
 
 logger = logging.getLogger(__name__)
 
+# Environment variable to control thinking tags preservation (default: true to maintain backward compatibility)
+# helper & env‑flag
+
+
+def _env_flag(name: str, default: bool = True) -> bool:
+    """Return an env var as bool (1/0 | true/false | yes/no)."""
+    val = os.getenv(name)
+    if val is None:
+        return default
+    return val.lower() in {"1", "true", "yes"}
+
+
+# keep `<think>` blocks unless explicitly disabled
+LLM_NODE_THINKING_TAGS_ENABLED = _env_flag("LLM_NODE_THINKING_TAGS_ENABLED")
+
 
 class LLMNode(BaseNode[LLMNodeData]):
     _node_data_cls = LLMNodeData
@@ -376,7 +393,12 @@ class LLMNode(BaseNode[LLMNodeData]):
         except OutputParserError as e:
             raise LLMNodeError(f"Failed to parse structured output: {e}")
 
-        yield ModelInvokeCompletedEvent(text=full_text_buffer.getvalue(), usage=usage, finish_reason=finish_reason)
+        # Apply thinking tags removal if disabled
+        result_text = full_text_buffer.getvalue()
+        if not LLM_NODE_THINKING_TAGS_ENABLED:
+            result_text = self._remove_thinking_tags(result_text)
+
+        yield ModelInvokeCompletedEvent(text=result_text, usage=usage, finish_reason=finish_reason)
 
     def _image_file_to_markdown(self, file: "File", /):
         text_chunk = f"![]({file.generate_url()})"
@@ -902,8 +924,13 @@ class LLMNode(BaseNode[LLMNodeData]):
         for text_part in self._save_multimodal_output_and_convert_result_to_markdown(invoke_result.message.content):
             buffer.write(text_part)
 
+        # Apply thinking tags removal if disabled
+        result_text = buffer.getvalue()
+        if not LLM_NODE_THINKING_TAGS_ENABLED:
+            result_text = self._remove_thinking_tags(result_text)
+
         return ModelInvokeCompletedEvent(
-            text=buffer.getvalue(),
+            text=result_text,
             usage=invoke_result.usage,
             finish_reason=None,
         )
@@ -1004,6 +1031,32 @@ class LLMNode(BaseNode[LLMNodeData]):
             logger.warning("unknown contents type encountered, type=%s", type(contents))
             yield str(contents)
 
+    def _remove_thinking_tags(self, text: str) -> str:
+        """
+        Remove thinking tags like <think></think> from the response text.
+        This handles reasoning models like qwen, deepseek-r1 that include thinking process.
+
+        Args:
+            text: The text content to clean
+
+        Returns:
+            Cleaned text with thinking tags removed
+        """
+        if not isinstance(text, str) or not text.strip():
+            return text
+
+        # Remove <think>...</think> blocks (case-insensitive, multiline)
+        # Pattern explanation:
+        # \s* - optional whitespace before <think>
+        # <think>.*?</think> - the thinking tag block (non-greedy)
+        # \s* - optional whitespace after </think>
+        cleaned_text = re.sub(r"\s*<think>.*?</think>\s*", " ", text, flags=re.IGNORECASE | re.DOTALL)
+
+        # Clean up multiple spaces and strip
+        cleaned_text = re.sub(r"\s+", " ", cleaned_text).strip()
+
+        return cleaned_text
+
 
 def _combine_message_content_with_role(
     *, contents: Optional[str | list[PromptMessageContentUnionTypes]] = None, role: PromptMessageRole
diff --git a/api/tests/integration_tests/workflow/nodes/test_llm.py b/api/tests/integration_tests/workflow/nodes/test_llm.py
index ff119b7482..de1f400ec1 100644
--- a/api/tests/integration_tests/workflow/nodes/test_llm.py
+++ b/api/tests/integration_tests/workflow/nodes/test_llm.py
@@ -286,3 +286,121 @@ def test_extract_json():
     ]
     result = {"name": "test", "age": 123}
     assert all(_parse_structured_output(item) == result for item in llm_texts)
+
+
+@pytest.mark.parametrize(
+    ("thinking_tags_enabled", "should_preserve_tags"),
+    [
+        ("true", True),  # LLM_NODE_THINKING_TAGS_ENABLED=true -> tags should be preserved
+        ("false", False),  # LLM_NODE_THINKING_TAGS_ENABLED=false -> tags should be removed
+    ],
+)
+def test_execute_llm_with_thinking_tags(flask_req_ctx, thinking_tags_enabled, should_preserve_tags):
+    """Test LLM node with thinking tags removal controlled via environment variable."""
+    import os
+
+    with patch.dict(os.environ, {"LLM_NODE_THINKING_TAGS_ENABLED": thinking_tags_enabled}):
+        # Reload the module to pick up the environment variable change
+        import importlib
+
+        from core.workflow.nodes.llm import node
+
+        importlib.reload(node)
+
+        node_instance = init_llm_node(
+            config={
+                "id": "llm",
+                "data": {
+                    "title": f"thinking tags test ({'preserved' if should_preserve_tags else 'removed'})",
+                    "type": "llm",
+                    "model": {
+                        "provider": "langgenius/openrouter",
+                        "name": "qwen/qwen-2.5-72b-instruct",
+                        "mode": "chat",
+                        "completion_params": {},
+                    },
+                    "prompt_template": [
+                        {
+                            "role": "system",
+                            "text": "you are a helpful assistant.",
+                        },
+                        {"role": "user", "text": "Say hello"},
+                    ],
+                    "memory": None,
+                    "context": {"enabled": False},
+                    "vision": {"enabled": False},
+                },
+            },
+        )
+
+        # Create mock LLM result with thinking tags
+        mock_usage = LLMUsage(
+            prompt_tokens=10,
+            prompt_unit_price=Decimal("0.001"),
+            prompt_price_unit=Decimal("1000"),
+            prompt_price=Decimal("0.00001"),
+            completion_tokens=15,
+            completion_unit_price=Decimal("0.002"),
+            completion_price_unit=Decimal("1000"),
+            completion_price=Decimal("0.00003"),
+            total_tokens=25,
+            total_price=Decimal("0.00004"),
+            currency="USD",
+            latency=0.3,
+        )
+
+        # Mock response with thinking tags (simulating Qwen reasoning behavior)
+        mock_message = AssistantPromptMessage(
+            content="<think>Let me think about this greeting...</think>Hello! How can I help you today?"
+        )
+
+        mock_llm_result = LLMResult(
+            model="qwen/qwen-2.5-72b-instruct",
+            prompt_messages=[],
+            message=mock_message,
+            usage=mock_usage,
+        )
+
+        mock_model_instance = MagicMock()
+        mock_model_instance.invoke_llm.return_value = mock_llm_result
+
+        mock_model_config = MagicMock()
+        mock_model_config.mode = "chat"
+        mock_model_config.provider = "langgenius/openrouter"
+        mock_model_config.model = "qwen/qwen-2.5-72b-instruct"
+        mock_model_config.provider_model_bundle.configuration.tenant_id = "9d2074fc-6f86-45a9-b09d-6ecc63b9056b"
+
+        def mock_fetch_model_config_func(_node_data_model):
+            return mock_model_instance, mock_model_config
+
+        def mock_get_model_instance(_self, **kwargs):
+            return mock_model_instance
+
+        with (
+            patch.object(node_instance, "_fetch_model_config", mock_fetch_model_config_func),
+            patch("core.model_manager.ModelManager.get_model_instance", mock_get_model_instance),
+        ):
+            # Execute node
+            result = node_instance._run()
+            assert isinstance(result, Generator)
+
+            # Verify behavior based on the parameter
+            for item in result:
+                if isinstance(item, RunCompletedEvent):
+                    assert item.run_result.status == WorkflowNodeExecutionStatus.SUCCEEDED
+                    output_text = item.run_result.outputs.get("text")
+                    assert output_text is not None
+
+                    if should_preserve_tags:
+                        # Verify thinking tags are preserved when enabled
+                        assert "<think>" in output_text
+                        assert "</think>" in output_text
+                        assert "Let me think about this greeting..." in output_text
+                        assert "Hello! How can I help you today?" in output_text
+                    else:
+                        # Verify thinking tags are removed when disabled
+                        assert "<think>" not in output_text
+                        assert "</think>" not in output_text
+                        assert "Hello! How can I help you today?" in output_text
+                        # Verify thinking content is not in output
+                        assert "Let me think about this greeting..." not in output_text
diff --git a/api/tests/unit_tests/core/workflow/nodes/llm/test_node.py b/api/tests/unit_tests/core/workflow/nodes/llm/test_node.py
index fefad0ec95..274ff5fb77 100644
--- a/api/tests/unit_tests/core/workflow/nodes/llm/test_node.py
+++ b/api/tests/unit_tests/core/workflow/nodes/llm/test_node.py
@@ -1,4 +1,6 @@
 import base64
+import importlib
+import os
 import uuid
 from collections.abc import Sequence
 from typing import Optional
@@ -6,6 +8,7 @@ from unittest import mock
 
 import pytest
 
+import core.workflow.nodes.llm.node
 from core.app.entities.app_invoke_entities import InvokeFrom, ModelConfigWithCredentialsEntity
 from core.entities.provider_configuration import ProviderConfiguration, ProviderModelBundle
 from core.entities.provider_entities import CustomConfiguration, SystemConfiguration
@@ -663,3 +666,104 @@ class TestSaveMultimodalOutputAndConvertResultToMarkdown:
         assert list(gen) == []
         mock_file_saver.save_binary_string.assert_not_called()
         mock_file_saver.save_remote_url.assert_not_called()
+
+
+class TestThinkingTagsRemoval:
+    """Test cases for thinking tags removal functionality in LLM Node."""
+
+    def test_remove_single_thinking_tag(self, llm_node):
+        """Test removal of single thinking tag block."""
+        input_text = "<think>This is my thinking process</think>Hello, how can I help you?"
+        expected = "Hello, how can I help you?"
+
+        result = llm_node._remove_thinking_tags(input_text)
+        assert result == expected
+
+    def test_remove_multiple_thinking_tags(self, llm_node):
+        """Test removal of multiple thinking tag blocks."""
+        input_text = "<think>First thought</think>Hello<think>Second thought</think> World!"
+        expected = "Hello World!"
+
+        result = llm_node._remove_thinking_tags(input_text)
+        assert result == expected
+
+    def test_remove_multiline_thinking_tag(self, llm_node):
+        """Test removal of multiline thinking tag blocks."""
+        input_text = """<think>
+This is a multiline
+thinking process
+with multiple lines
+</think>Final answer here."""
+        expected = "Final answer here."
+
+        result = llm_node._remove_thinking_tags(input_text)
+        assert result == expected
+
+    def test_case_insensitive_removal(self, llm_node):
+        """Test case-insensitive thinking tag removal."""
+        input_text = "<THINK>Uppercase thinking</THINK>Response"
+        expected = "Response"
+
+        result = llm_node._remove_thinking_tags(input_text)
+        assert result == expected
+
+    def test_no_thinking_tags(self, llm_node):
+        """Test text without thinking tags remains unchanged."""
+        input_text = "Hello, this is a normal response without thinking tags."
+        expected = input_text
+
+        result = llm_node._remove_thinking_tags(input_text)
+        assert result == expected
+
+    def test_empty_string(self, llm_node):
+        """Test empty string handling."""
+        input_text = ""
+        expected = ""
+
+        result = llm_node._remove_thinking_tags(input_text)
+        assert result == expected
+
+    def test_only_thinking_tag(self, llm_node):
+        """Test string with only thinking tag."""
+        input_text = "<think>Only thinking, no response</think>"
+        expected = ""
+
+        result = llm_node._remove_thinking_tags(input_text)
+        assert result == expected
+
+    def test_whitespace_handling(self, llm_node):
+        """Test proper whitespace handling after tag removal."""
+        input_text = "<think>Thinking</think>   Response with spaces"
+        expected = "Response with spaces"
+
+        result = llm_node._remove_thinking_tags(input_text)
+        assert result == expected
+
+    def test_none_input(self, llm_node):
+        """Test None input handling."""
+        result = llm_node._remove_thinking_tags(None)
+        assert result is None
+
+    def test_non_string_input(self, llm_node):
+        """Test non-string input handling."""
+        result = llm_node._remove_thinking_tags(123)
+        assert result == 123
+
+    @mock.patch.dict("os.environ", {"LLM_NODE_THINKING_TAGS_ENABLED": "true"})
+    def test_environment_variable_enabled(self):
+        """Test that environment variable is properly read when enabled."""
+        importlib.reload(core.workflow.nodes.llm.node)
+        assert core.workflow.nodes.llm.node.LLM_NODE_THINKING_TAGS_ENABLED is True
+
+    @mock.patch.dict("os.environ", {"LLM_NODE_THINKING_TAGS_ENABLED": "false"})
+    def test_environment_variable_disabled(self):
+        """Test that environment variable is properly read when disabled."""
+        importlib.reload(core.workflow.nodes.llm.node)
+        assert core.workflow.nodes.llm.node.LLM_NODE_THINKING_TAGS_ENABLED is False
+
+    def test_environment_variable_default(self):
+        """Test that environment variable defaults to True."""
+        with mock.patch.dict("os.environ"):
+            os.environ.pop("LLM_NODE_THINKING_TAGS_ENABLED", None)
+            importlib.reload(core.workflow.nodes.llm.node)
+            assert core.workflow.nodes.llm.node.LLM_NODE_THINKING_TAGS_ENABLED is True
diff --git a/docker/.env.example b/docker/.env.example
index a05141569b..f220de8746 100644
--- a/docker/.env.example
+++ b/docker/.env.example
@@ -824,6 +824,10 @@ HTTP_REQUEST_NODE_MAX_BINARY_SIZE=10485760
 HTTP_REQUEST_NODE_MAX_TEXT_SIZE=1048576
 HTTP_REQUEST_NODE_SSL_VERIFY=True
 
+# LLM node thinking tags preservation (default: true)
+# Set to false to remove <think></think> tags from reasoning models like DeepSeek-R1, Qwen
+LLM_NODE_THINKING_TAGS_ENABLED=true
+
 # Respect X-* headers to redirect clients
 RESPECT_XFORWARD_HEADERS_ENABLED=false
 
diff --git a/docker/docker-compose.yaml b/docker/docker-compose.yaml
index 5962adb079..8b52419fa7 100644
--- a/docker/docker-compose.yaml
+++ b/docker/docker-compose.yaml
@@ -366,6 +366,7 @@ x-shared-env: &shared-api-worker-env
   HTTP_REQUEST_NODE_MAX_BINARY_SIZE: ${HTTP_REQUEST_NODE_MAX_BINARY_SIZE:-10485760}
   HTTP_REQUEST_NODE_MAX_TEXT_SIZE: ${HTTP_REQUEST_NODE_MAX_TEXT_SIZE:-1048576}
   HTTP_REQUEST_NODE_SSL_VERIFY: ${HTTP_REQUEST_NODE_SSL_VERIFY:-True}
+  LLM_NODE_THINKING_TAGS_ENABLED: ${LLM_NODE_THINKING_TAGS_ENABLED:-true}
   RESPECT_XFORWARD_HEADERS_ENABLED: ${RESPECT_XFORWARD_HEADERS_ENABLED:-false}
   SSRF_PROXY_HTTP_URL: ${SSRF_PROXY_HTTP_URL:-http://ssrf_proxy:3128}
   SSRF_PROXY_HTTPS_URL: ${SSRF_PROXY_HTTPS_URL:-http://ssrf_proxy:3128}