diff --git a/cpp/tensorrt_llm/batch_manager/guidedDecoder.cpp b/cpp/tensorrt_llm/batch_manager/guidedDecoder.cpp
index edf8917d27..871a33e3ee 100644
--- a/cpp/tensorrt_llm/batch_manager/guidedDecoder.cpp
+++ b/cpp/tensorrt_llm/batch_manager/guidedDecoder.cpp
@@ -35,6 +35,8 @@ GuidedDecoder::GuidedDecoder(executor::GuidedDecodingConfig const& guidedDecodin
     , mLogitsDtype{logitsDtype}
     , mCopyBufferManager{std::make_shared<CudaStream>()}
 {
+    TLLM_CHECK_WITH_INFO(mGuidedDecodingBackend != executor::GuidedDecodingConfig::GuidedDecodingBackend::kLLGUIDANCE,
+        "LLGuidance is not supported for guided decoding in C++ runtime.");
     if (mGuidedDecodingBackend == executor::GuidedDecodingConfig::GuidedDecodingBackend::kXGRAMMAR)
     {
         mXGrammarMatchers.resize(mMaxNumSequences);
diff --git a/cpp/tensorrt_llm/executor/executorImpl.cpp b/cpp/tensorrt_llm/executor/executorImpl.cpp
index c2118bbf77..b9df58f9a7 100644
--- a/cpp/tensorrt_llm/executor/executorImpl.cpp
+++ b/cpp/tensorrt_llm/executor/executorImpl.cpp
@@ -1621,6 +1621,9 @@ std::tuple<Executor::Impl::RequestList, double> Executor::Impl::fetchNewRequests
                     TLLM_CHECK_WITH_INFO(mModel->hasGuidedDecoder(),
                         "Request is specified with GuidedDecodingParams, but GuidedDecoder is not setup. Please "
                         "provide a valid GuidedDecodingConfig to setup GuidedDecoder.");
+                    TLLM_CHECK_WITH_INFO(newReq->getGuidedDecodingParams()->getGuideType()
+                            != executor::GuidedDecodingParams::GuideType::kSTRUCTURAL_TAG,
+                        "Structural tag is not supported for guided decoding in C++ Executor.");
                 }
 
                 if (mModel->getWorldConfig().isLastPipelineParallelRank() && newReq->hasAdditionalOutputs())
diff --git a/examples/trtllm-eval/README.md b/examples/trtllm-eval/README.md
index c06310c388..217e292981 100644
--- a/examples/trtllm-eval/README.md
+++ b/examples/trtllm-eval/README.md
@@ -10,8 +10,7 @@ We provide a CLI tool `trtllm-eval` for evaluating model accuracy. It shares the
 pip install -r requirements.txt
 
 # Evaluate Llama-3.1-8B-Instruct on MMLU
-wget https://people.eecs.berkeley.edu/~hendrycks/data.tar && tar -xf data.tar
-trtllm-eval --model meta-llama/Llama-3.1-8B-Instruct mmlu --dataset_path data
+trtllm-eval --model meta-llama/Llama-3.1-8B-Instruct mmlu
 
 # Evaluate Llama-3.1-8B-Instruct on GSM8K
 trtllm-eval --model meta-llama/Llama-3.1-8B-Instruct gsm8k
diff --git a/tensorrt_llm/_torch/pyexecutor/grammar_matcher.py b/tensorrt_llm/_torch/pyexecutor/grammar_matcher.py
index 536caab6d3..23b0c729c0 100644
--- a/tensorrt_llm/_torch/pyexecutor/grammar_matcher.py
+++ b/tensorrt_llm/_torch/pyexecutor/grammar_matcher.py
@@ -96,7 +96,7 @@ class XGrammarMatcherFactory(GrammarMatcherFactory):
                 compiled_grammar = self._xgrammar_compiler.compile_structural_tag(
                     structures, triggers)
             case _:
-                raise ValueError(f"Unrecognized guide type: {guide_type}.")
+                raise ValueError(f"Unsupported guide type: {guide_type}.")
 
         matcher = xgrammar.GrammarMatcher(compiled_grammar)
         return XGrammarMatcher(matcher)
@@ -167,7 +167,7 @@ class LLGuidanceMatcherFactory(GrammarMatcherFactory):
                 # provide Lark-formatted grammar instead of standard EBNF.
                 grammar = llguidance.LLMatcher.grammar_from_lark(guide)
             case _:
-                raise ValueError(f"Unrecognized guide type: {guide_type}.")
+                raise ValueError(f"Unsupported guide type: {guide_type}.")
 
         matcher = llguidance.LLMatcher(self._tokenizer, grammar)
         if matcher.is_error():
diff --git a/tensorrt_llm/evaluate/json_mode_eval.py b/tensorrt_llm/evaluate/json_mode_eval.py
index 69c41699cd..1854488bce 100644
--- a/tensorrt_llm/evaluate/json_mode_eval.py
+++ b/tensorrt_llm/evaluate/json_mode_eval.py
@@ -13,6 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import json
+import os
 from typing import Iterable, List, Optional, Union
 
 import click
@@ -56,8 +57,13 @@ class JsonModeEval(Evaluator):
         for i, sample in enumerate(self.data):
             if i >= self.num_samples:
                 break
+            schema = sample["schema"]
+            if os.environ.get("TRTLLM_XGUIDANCE_LENIENT") == "1":
+                schema = json.loads(schema)
+                schema["x-guidance"] = {"lenient": True}
+                schema = json.dumps(schema)
             sampling_args = {
-                "guided_decoding": GuidedDecodingParams(json=sample["schema"])
+                "guided_decoding": GuidedDecodingParams(json=schema)
             }
             yield sample["prompt"], sampling_args, sample["completion"]
 
diff --git a/tensorrt_llm/llmapi/llm_args.py b/tensorrt_llm/llmapi/llm_args.py
index 636740d599..a0c2124960 100644
--- a/tensorrt_llm/llmapi/llm_args.py
+++ b/tensorrt_llm/llmapi/llm_args.py
@@ -879,8 +879,11 @@ class BaseLlmArgs(BaseModel):
     enable_chunked_prefill: bool = Field(default=False,
                                          description="Enable chunked prefill.")
 
-    guided_decoding_backend: Optional[str] = Field(
-        default=None, description="Guided decoding backend.")
+    guided_decoding_backend: Optional[Literal["xgrammar", "llguidance"]] = Field(
+        default=None,
+        description=
+        "Guided decoding backend. llguidance is supported in PyTorch backend only."
+    )
 
     batched_logits_processor: Optional[object] = Field(
         default=None,
diff --git a/tensorrt_llm/sampling_params.py b/tensorrt_llm/sampling_params.py
index 04442a2e1f..42ccf02f13 100644
--- a/tensorrt_llm/sampling_params.py
+++ b/tensorrt_llm/sampling_params.py
@@ -19,7 +19,7 @@ class GuidedDecodingParams:
         regex (str, optional): The generated text is amenable to the user-specified regular expression. Defaults to None.
         grammar (str, optional): The generated text is amenable to the user-specified extended Backus-Naur form (EBNF) grammar. Defaults to None.
         json_object (bool): If True, the generated text is amenable to json format. Defaults to False.
-        structural_tag (str, optional): The generated text is amenable to the user-specified structural tag. Defaults to None.
+        structural_tag (str, optional): The generated text is amenable to the user-specified structural tag. Structural tag is supported by xgrammar in PyTorch backend only. Defaults to None.
     """  # noqa: E501
 
     json: Optional[Union[str, BaseModel, dict]] = None
diff --git a/tests/integration/defs/accuracy/test_llm_api.py b/tests/integration/defs/accuracy/test_llm_api.py
index 8cdb49cf56..576b56b817 100644
--- a/tests/integration/defs/accuracy/test_llm_api.py
+++ b/tests/integration/defs/accuracy/test_llm_api.py
@@ -58,16 +58,18 @@ class TestLlama3_1_8BInstruct(LlmapiAccuracyTestHarness):
             task = GSM8K(self.MODEL_NAME)
             task.evaluate(llm)
 
-    def test_guided_decoding(self):
-        llm = LLM(self.MODEL_PATH, guided_decoding_backend="xgrammar")
+    @pytest.mark.parametrize("backend", ["xgrammar"])
+    def test_guided_decoding(self, backend: str):
+        llm = LLM(self.MODEL_PATH, guided_decoding_backend=backend)
         with llm:
             task = JsonModeEval(self.MODEL_NAME)
             task.evaluate(llm)
 
     @pytest.mark.skip_less_device(4)
-    def test_guided_decoding_4gpus(self):
+    @pytest.mark.parametrize("backend", ["xgrammar"])
+    def test_guided_decoding_4gpus(self, backend: str):
         llm = LLM(self.MODEL_PATH,
-                  guided_decoding_backend="xgrammar",
+                  guided_decoding_backend=backend,
                   tensor_parallel_size=2,
                   pipeline_parallel_size=2)
         with llm:
diff --git a/tests/integration/defs/accuracy/test_llm_api_pytorch.py b/tests/integration/defs/accuracy/test_llm_api_pytorch.py
index c4bfad8a8e..9b4d47c947 100644
--- a/tests/integration/defs/accuracy/test_llm_api_pytorch.py
+++ b/tests/integration/defs/accuracy/test_llm_api_pytorch.py
@@ -12,6 +12,8 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import os
+
 import pytest
 
 from tensorrt_llm import LLM
@@ -277,9 +279,11 @@ class TestLlama3_1_8BInstruct(LlmapiAccuracyTestHarness):
             task = MMLU(self.MODEL_NAME)
             task.evaluate(llm)
 
-    def test_guided_decoding(self):
+    @pytest.mark.parametrize("backend", ["xgrammar", "llguidance"])
+    def test_guided_decoding(self, backend: str, mocker):
+        mocker.patch.dict(os.environ, {"TRTLLM_XGUIDANCE_LENIENT": "1"})
         llm = LLM(self.MODEL_PATH,
-                  guided_decoding_backend="xgrammar",
+                  guided_decoding_backend=backend,
                   disable_overlap_scheduler=True,
                   use_cuda_graph=True)
         with llm:
@@ -287,9 +291,11 @@ class TestLlama3_1_8BInstruct(LlmapiAccuracyTestHarness):
             task.evaluate(llm)
 
     @pytest.mark.skip_less_device(4)
-    def test_guided_decoding_4gpus(self):
+    @pytest.mark.parametrize("backend", ["xgrammar", "llguidance"])
+    def test_guided_decoding_4gpus(self, backend: str, mocker):
+        mocker.patch.dict(os.environ, {"TRTLLM_XGUIDANCE_LENIENT": "1"})
         llm = LLM(self.MODEL_PATH,
-                  guided_decoding_backend="xgrammar",
+                  guided_decoding_backend=backend,
                   disable_overlap_scheduler=True,
                   use_cuda_graph=True,
                   tensor_parallel_size=2,
diff --git a/tests/integration/test_lists/qa/examples_test_list.txt b/tests/integration/test_lists/qa/examples_test_list.txt
index bf8a86411a..4d0d0da24e 100644
--- a/tests/integration/test_lists/qa/examples_test_list.txt
+++ b/tests/integration/test_lists/qa/examples_test_list.txt
@@ -418,8 +418,8 @@ accuracy/test_llm_api.py::TestQwen2_7BInstruct::test_weight_only
 accuracy/test_cli_flow.py::TestQwen2_7BInstruct::test_int4_awq_prequantized
 accuracy/test_cli_flow.py::TestQwen2_57B_A14B::test_tp4
 accuracy/test_cli_flow.py::TestQwen2_57B_A14B::test_tp2pp2
-accuracy/test_llm_api.py::TestLlama3_1_8BInstruct::test_guided_decoding
-accuracy/test_llm_api.py::TestLlama3_1_8BInstruct::test_guided_decoding_4gpus
+accuracy/test_llm_api.py::TestLlama3_1_8BInstruct::test_guided_decoding[xgrammar]
+accuracy/test_llm_api.py::TestLlama3_1_8BInstruct::test_guided_decoding_4gpus[xgrammar]
 accuracy/test_llm_api.py::TestQwen2_5_1_5BInstruct::test_auto_dtype
 accuracy/test_llm_api.py::TestQwen2_5_1_5BInstruct::test_weight_only
 accuracy/test_llm_api.py::TestLlama3_1_8B::test_fp8_rowwise
@@ -440,8 +440,10 @@ accuracy/test_llm_api_pytorch.py::TestLlama3_1_8B::test_nvfp4
 accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_fp8_llm_sampler
 accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_eagle3
 accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_ngram
-accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_guided_decoding
-accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_guided_decoding_4gpus
+accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_guided_decoding[xgrammar]
+accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_guided_decoding[llguidance]
+accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_guided_decoding_4gpus[xgrammar]
+accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_guided_decoding_4gpus[llguidance]
 accuracy/test_llm_api_pytorch.py::TestLlama3_3_70BInstruct::test_fp8_tp4
 accuracy/test_llm_api_pytorch.py::TestLlama3_3_70BInstruct::test_nvfp4_tp4
 accuracy/test_cli_flow.py::TestLlama3_3_70BInstruct::test_fp8_prequantized_tp4
diff --git a/tests/integration/test_lists/test-db/l0_a100.yml b/tests/integration/test_lists/test-db/l0_a100.yml
index 5f152ad9ce..3cf77d6067 100644
--- a/tests/integration/test_lists/test-db/l0_a100.yml
+++ b/tests/integration/test_lists/test-db/l0_a100.yml
@@ -46,7 +46,7 @@ l0_a100:
   - accuracy/test_cli_flow.py::TestLlama3_2_1B::test_smooth_quant_ootb_manage_weights
   - accuracy/test_cli_flow.py::TestLlama3_8BInstruct::test_int8_gptq
   - accuracy/test_cli_flow.py::TestQwen2_7BInstruct::test_int4_awq_prequantized
-  - accuracy/test_llm_api.py::TestLlama3_1_8BInstruct::test_guided_decoding
+  - accuracy/test_llm_api.py::TestLlama3_1_8BInstruct::test_guided_decoding[xgrammar]
 - condition:
     ranges:
       system_gpu_count:
diff --git a/tests/integration/test_lists/test-db/l0_dgx_h100.yml b/tests/integration/test_lists/test-db/l0_dgx_h100.yml
index 569e07377a..8c874e82f3 100644
--- a/tests/integration/test_lists/test-db/l0_dgx_h100.yml
+++ b/tests/integration/test_lists/test-db/l0_dgx_h100.yml
@@ -31,7 +31,7 @@ l0_dgx_h100:
   - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_fp8_4gpus[tp2pp2-fp8kv=True-attn_backend=TRTLLM-torch_compile=False]
   - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_fp8_4gpus[pp4-fp8kv=True-attn_backend=TRTLLM-torch_compile=False]
   - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_fp8_4gpus[tp2pp2-fp8kv=True-attn_backend=TRTLLM-torch_compile=True]
-  - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_guided_decoding_4gpus
+  - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_guided_decoding_4gpus[xgrammar]
   - disaggregated/test_disaggregated.py::test_disaggregated_multi_gpu_with_mpirun[TinyLlama-1.1B-Chat-v1.0]
   - disaggregated/test_disaggregated.py::test_disaggregated_multi_gpu_with_mpirun_trt_backend[TinyLlama-1.1B-Chat-v1.0]
   - disaggregated/test_disaggregated.py::test_disaggregated_cuda_graph[TinyLlama-1.1B-Chat-v1.0]
diff --git a/tests/integration/test_lists/test-db/l0_dgx_h200.yml b/tests/integration/test_lists/test-db/l0_dgx_h200.yml
index 6fd0b9875f..657ab4475a 100644
--- a/tests/integration/test_lists/test-db/l0_dgx_h200.yml
+++ b/tests/integration/test_lists/test-db/l0_dgx_h200.yml
@@ -92,6 +92,7 @@ l0_dgx_h200:
   - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_fp8_4gpus[tp2pp2-fp8kv=True-attn_backend=FLASHINFER-torch_compile=False]
   - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_fp8_4gpus[tp2pp2-fp8kv=True-attn_backend=FLASHINFER-torch_compile=True]
   - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_fp8_4gpus[pp4-fp8kv=True-attn_backend=FLASHINFER-torch_compile=False]
+  - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_guided_decoding_4gpus[llguidance]
 - condition:
     ranges:
       system_gpu_count:
@@ -120,7 +121,7 @@ l0_dgx_h200:
   - accuracy/test_llm_api.py::TestQwen2_7BInstruct::test_tp2
   - accuracy/test_llm_api.py::TestLlama3_1_8BInstruct::test_cp2
   - accuracy/test_llm_api.py::TestLlama3_1_8BInstruct::test_tp2cp2
-  - accuracy/test_llm_api.py::TestLlama3_1_8BInstruct::test_guided_decoding_4gpus
+  - accuracy/test_llm_api.py::TestLlama3_1_8BInstruct::test_guided_decoding_4gpus[xgrammar]
   - examples/test_llama.py::test_llm_llama_long_alpaca_8gpu_summary[pg64317-tp4pp2-nb:4]
   - examples/test_llama.py::test_llm_llama_v2_lora_benchmark_2gpu[chinese_lora-llama-v2-13b-hf]
   - examples/test_mixtral.py::test_llm_mixtral_moe_plugin_lora_4gpus[Mixtral-8x7B-v0.1-chinese-mixtral-lora]
diff --git a/tests/integration/test_lists/test-db/l0_h100.yml b/tests/integration/test_lists/test-db/l0_h100.yml
index bb6af71122..42c8dbb8bb 100644
--- a/tests/integration/test_lists/test-db/l0_h100.yml
+++ b/tests/integration/test_lists/test-db/l0_h100.yml
@@ -29,7 +29,7 @@ l0_h100:
   - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_bfloat16[attn_backend=FLASHINFER-torch_compile=True]
   - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_chunked_prefill[attn_backend=TRTLLM] TIMEOUT (90)
   - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_chunked_prefill[attn_backend=FLASHINFER] TIMEOUT (60)
-  - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_guided_decoding
+  - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_guided_decoding[xgrammar]
   - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_fp8[fp8kv=False-attn_backend=TRTLLM-torch_compile=False]
   - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_fp8[fp8kv=False-attn_backend=TRTLLM-torch_compile=True]
   - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_fp8[fp8kv=False-attn_backend=FLASHINFER-torch_compile=False]
@@ -182,6 +182,7 @@ l0_h100:
   - accuracy/test_llm_api_pytorch.py::TestDeepSeekV3Lite::test_fp8_block_scales[mtp=vanilla-fp8kv=False-attention_dp=False-cuda_graph=False-overlap_scheduler=False-torch_compile=False]
   - accuracy/test_llm_api_pytorch.py::TestDeepSeekV3Lite::test_no_kv_cache_reuse[quant_dtype=none-mtp_nextn=2-fp8kv=False-attention_dp=True-cuda_graph=True-overlap_scheduler=True]
   - accuracy/test_llm_api_pytorch.py::TestQwen3_30B_A3B::test_fp8_block_scales[latency]
+  - accuracy/test_llm_api_pytorch.py::TestLlama3_1_8BInstruct::test_guided_decoding[llguidance]
 - condition:
     ranges:
       system_gpu_count:
diff --git a/tests/integration/test_lists/waives.txt b/tests/integration/test_lists/waives.txt
index 6b69817e3b..11ee02bdf7 100644
--- a/tests/integration/test_lists/waives.txt
+++ b/tests/integration/test_lists/waives.txt
@@ -433,7 +433,7 @@ accuracy/test_llm_api_pytorch.py::TestDeepSeekV3Lite::test_nvfp4_4gpus[moe_backe
 accuracy/test_llm_api_pytorch.py::TestDeepSeekV3Lite::test_nvfp4_4gpus[moe_backend=TRTLLM-mtp_nextn=2-tp4-fp8kv=True-attention_dp=True-cuda_graph=True-overlap_scheduler=True-torch_compile=False] SKIP (https://nvbugs/5349343)
 accuracy/test_llm_api_pytorch.py::TestDeepSeekV3Lite::test_nvfp4_4gpus[moe_backend=TRTLLM-mtp_nextn=2-ep4-fp8kv=True-attention_dp=True-cuda_graph=True-overlap_scheduler=True-torch_compile=False] SKIP (https://nvbugs/5349343)
 full:B200/test_e2e.py::test_ptp_quickstart_advanced_deepseek_multi_nodes[DeepSeek-R1/DeepSeek-R1-0528-FP4] SKIP (https://nvbugs/5344688)
-accuracy/test_llm_api.py::TestLlama3_1_8BInstruct::test_guided_decoding_4gpus SKIP (https://nvbugs/5346443)
+accuracy/test_llm_api.py::TestLlama3_1_8BInstruct::test_guided_decoding_4gpus[xgrammar] SKIP (https://nvbugs/5346443)
 test_e2e.py::test_openai_reasoning SKIP (https://nvbugs/5355091)
 test_e2e.py::test_openai_misc_example SKIP (https://nvbugs/5355091)
 accuracy/test_disaggregated_serving.py::TestDeepSeekV3Lite::test_auto_dtype[mtp_nextn=0-overlap_scheduler=False] SKIP (https://nvbugs/5354956)
diff --git a/tests/unittest/api_stability/references_committed/llm.yaml b/tests/unittest/api_stability/references_committed/llm.yaml
index a30e62645f..7d26c9093e 100644
--- a/tests/unittest/api_stability/references_committed/llm.yaml
+++ b/tests/unittest/api_stability/references_committed/llm.yaml
@@ -62,7 +62,7 @@ methods:
         annotation: Optional[tensorrt_llm.sampling_params.BatchedLogitsProcessor]
         default: null
       guided_decoding_backend:
-        annotation: Optional[str]
+        annotation: Optional[Literal["xgrammar", "llguidance"]]
         default: null
       # Quantization and calibration
       quant_config: