fix(trt_llm): warn when python_version is ignored

truss/base/trt_llm_config.py

@@ -849,6 +849,15 @@ def trt_llm_common_validation(config: "TrussConfig"):
     from truss.base import truss_config
 
     assert config.trt_llm, "TRT-LLM configuration is required for TRT-LLM models"
+    default_python_version = truss_config.TrussConfig.model_fields[
+        "python_version"
+    ].default
+    if config.python_version != default_python_version:
+        logger.warning(
+            f"`python_version: {config.python_version}` has no effect on TRT-LLM models: "
+            "the TRT-LLM base image ships its own fixed Python interpreter, independent of "
+            "this setting."
+        )
     trt_llm_config: TRTLLMConfigurationV1 | TRTLLMConfigurationV2 = config.trt_llm.root
     base_model = (
         trt_llm_config.build.base_model

truss/tests/trt_llm/test_trt_llm_config.py

@@ -12,6 +12,7 @@
     TrussTRTLLMBuildConfiguration,
     TrussTRTLLMRuntimeConfiguration,
 )
+from truss.base.truss_config import TrussConfig
 
 
 def test_trt_llm_config_init_from_pydantic_models(trtllm_config):
@@ -246,3 +247,30 @@ def test_trt_llm_config_additional_fields(trtllm_config_v2):
 
     assert config.inference_stack == "v2"
     assert isinstance(config.build, TrussTRTLLMBuildConfiguration)
+
+
+def test_trt_llm_non_default_python_version_warns(trtllm_config, caplog):
+    """python_version has no effect on TRT-LLM models: the TRT-LLM base image ships
+    its own fixed Python interpreter. Setting a non-default value should warn."""
+    trtllm_config["python_version"] = "py311"
+
+    with caplog.at_level("WARNING"):
+        TrussConfig.from_dict(trtllm_config)
+
+    assert "has no effect on TRT-LLM models" in caplog.text
+
+
+def test_trt_llm_default_python_version_no_warning(trtllm_config, caplog):
+    with caplog.at_level("WARNING"):
+        TrussConfig.from_dict(trtllm_config)
+
+    assert "has no effect on TRT-LLM models" not in caplog.text
+
+
+def test_trt_llm_v2_non_default_python_version_warns(trtllm_config_v2, caplog):
+    trtllm_config_v2["python_version"] = "py311"
+
+    with caplog.at_level("WARNING"):
+        TrussConfig.from_dict(trtllm_config_v2)
+
+    assert "has no effect on TRT-LLM models" in caplog.text