diff --git a/questions/inference_server/inference_server.py b/questions/inference_server/inference_server.py
index 0f49f2d..f87ed03 100644
--- a/questions/inference_server/inference_server.py
+++ b/questions/inference_server/inference_server.py
@@ -35,6 +35,7 @@
     fast_inference,
     fast_feature_extract_inference,
 )
+from questions.vllm_inference import fast_vllm_inference, VLLM_AVAILABLE
 from questions.utils import log_time
 from sellerinfo import session_secret
 from .models import build_model
@@ -478,10 +479,11 @@ async def feature_extraction(
 @app.get("/liveness_check")
 async def liveness_check(request: Request):
     # global daemon
-    inference_result = fast_inference(
-        generate_params=GenerateParams(text="hi my friend", min_probability=0.9, max_length=1, model='any'),
-        model_cache=MODEL_CACHE,
-    )
+    params = GenerateParams(text="hi my friend", min_probability=0.9, max_length=1, model='any')
+    if VLLM_AVAILABLE:
+        inference_result = fast_vllm_inference(params, MODEL_CACHE)
+    else:
+        inference_result = fast_inference(params, MODEL_CACHE)
     return JSONResponse(inference_result)
 
 
@@ -856,7 +858,10 @@ async def generate_route(
     #             status_code=401, detail="Please subscribe at https://text-generator.io/subscribe first"
     #         )
     # todo validate api key and user
-    inference_result = fast_inference(generate_params, MODEL_CACHE)
+    if VLLM_AVAILABLE:
+        inference_result = fast_vllm_inference(generate_params, MODEL_CACHE)
+    else:
+        inference_result = fast_inference(generate_params, MODEL_CACHE)
     # todo vuln
     if request and background_tasks:
         if "X-Rapid-API-Key" not in request.headers and "x-rapid-api-key" not in request.headers:
@@ -913,7 +918,10 @@ async def generate_route_bulk(
             return HTTPException(status_code=400, detail=validation_result)
 
     for generate_params in bulk_params:
-        inference_result = fast_inference(generate_params)
+        if VLLM_AVAILABLE:
+            inference_result = fast_vllm_inference(generate_params)
+        else:
+            inference_result = fast_inference(generate_params)
         inference_results.append(inference_result)
     # todo vuln
     if request and background_tasks:
@@ -989,7 +997,10 @@ async def openai_route_named(
             status_code=401,
             detail="Please subscribe at https://text-generator.io/subscribe first, also ensure you have a credit card on file"
         )
-    inference_result = fast_inference(generate_params, MODEL_CACHE)
+    if VLLM_AVAILABLE:
+        inference_result = fast_vllm_inference(generate_params, MODEL_CACHE)
+    else:
+        inference_result = fast_inference(generate_params, MODEL_CACHE)
     if not openai_params.echo:
         ## remove all the inputs from the generated texts
         for i in range(len(inference_result)):
diff --git a/questions/vllm_inference.py b/questions/vllm_inference.py
new file mode 100644
index 0000000..8c70d79
--- /dev/null
+++ b/questions/vllm_inference.py
@@ -0,0 +1,88 @@
+import math
+from typing import List
+
+from nltk import sent_tokenize
+from loguru import logger
+
+from questions.models import GenerateParams
+from questions.fixtures import set_stop_reason, get_stop_reason
+from questions.post_process_results import post_process_results
+from questions.constants import weights_path_tgz
+from questions.utils import log_time
+from questions.inference_server.model_cache import ModelCache
+
+try:
+    from vllm import LLM, SamplingParams
+    VLLM_AVAILABLE = True
+except Exception:  # pragma: no cover - vllm may not be installed
+    LLM = None
+    SamplingParams = None
+    VLLM_AVAILABLE = False
+
+
+def load_vllm_model(model_path: str = weights_path_tgz):
+    if not VLLM_AVAILABLE:
+        raise RuntimeError("vllm is not installed")
+    return LLM(model=model_path)
+
+
+def _apply_custom_stop(text: str, logprobs: List[float], generate_params: GenerateParams) -> str:
+    """Apply custom stopping conditions on generated text."""
+    cumulative_prob = 1.0
+    output = ""
+    for token_text, logprob in zip(text.split(), logprobs):
+        output += token_text + " "
+        if generate_params.min_probability and logprob is not None:
+            cumulative_prob *= math.exp(logprob)
+            if cumulative_prob < generate_params.min_probability:
+                set_stop_reason("min_probability")
+                return output.strip()
+        if generate_params.max_sentences:
+            if len(sent_tokenize(output)) > generate_params.max_sentences:
+                set_stop_reason("max_sentences")
+                return output.strip()
+    return output.strip()
+
+
+def fast_vllm_inference(generate_params: GenerateParams, model_cache: ModelCache = None):
+    """Run inference with vLLM and apply custom stopping criteria."""
+    if not VLLM_AVAILABLE:
+        raise RuntimeError("vllm is not installed")
+
+    llm = None
+    if model_cache is not None:
+        llm = model_cache.add_or_get("vllm_model", lambda: load_vllm_model())
+    else:
+        llm = load_vllm_model()
+
+    sampling_params = SamplingParams(
+        temperature=generate_params.temperature,
+        top_p=generate_params.top_p,
+        top_k=generate_params.top_k,
+        max_tokens=generate_params.max_length,
+        stop=generate_params.stop_sequences or None,
+        repetition_penalty=generate_params.repetition_penalty,
+    )
+
+    with log_time("vllm_generate"):
+        outputs = llm.generate([generate_params.text], sampling_params)
+
+    results = []
+    for output in outputs:
+        candidate = output.outputs[0]
+        generated = _apply_custom_stop(candidate.text, candidate.logprobs, generate_params)
+        full_text = generate_params.text + generated
+        results.append({"generated_text": full_text, "stop_reason": get_stop_reason()})
+
+    processed = post_process_results(
+        [r["generated_text"] for r in results],
+        generate_params,
+        generate_params.text,
+        generate_params.text,
+    )
+
+    final = []
+    for result, processed_text in zip(results, processed):
+        result["generated_text"] = processed_text
+        final.append(result)
+    return final
diff --git a/tests/conftest.py b/tests/conftest.py
index 87963c8..c1b0bc6 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,10 +1,14 @@
-import httpx
+try:
+    import httpx
+except ImportError:  # pragma: no cover - optional dependency
+    httpx = None
 
-_old_init = httpx.Client.__init__
+if httpx:
+    _old_init = httpx.Client.__init__
 
-def fixed_init(self, *args, **kwargs):
-    # Remove 'app' from kwargs if present
-    kwargs.pop('app', None)
-    _old_init(self, *args, **kwargs)
+    def fixed_init(self, *args, **kwargs):
+        # Remove 'app' from kwargs if present
+        kwargs.pop('app', None)
+        _old_init(self, *args, **kwargs)
 
-httpx.Client.__init__ = fixed_init 
\ No newline at end of file
+    httpx.Client.__init__ = fixed_init
diff --git a/tests/unit/test_vllm_inference.py b/tests/unit/test_vllm_inference.py
new file mode 100644
index 0000000..9419105
--- /dev/null
+++ b/tests/unit/test_vllm_inference.py
@@ -0,0 +1,12 @@
+import pytest
+
+from questions.vllm_inference import VLLM_AVAILABLE, fast_vllm_inference
+from questions.models import GenerateParams
+from questions.inference_server.model_cache import ModelCache
+
+
+@pytest.mark.skipif(VLLM_AVAILABLE, reason="vllm available - skip lightweight test")
+def test_vllm_missing():
+    params = GenerateParams(text="hi")
+    with pytest.raises(RuntimeError):
+        fast_vllm_inference(params, ModelCache())