From 284667ca0b3641a08bf55a22e809ffcfb7a321a9 Mon Sep 17 00:00:00 2001
From: blockgroot <170620375+blockgroot@users.noreply.github.com>
Date: Thu, 6 Aug 2026 17:11:32 +0530
Subject: [PATCH] fix(trt_llm): warn when python_version is ignored

TRT-LLM base images ship their own fixed Python interpreter, and
docker_build_setup.py overrides config.base_image + python_executable_path
unconditionally for every TRT-LLM v1 and v2 model. As a result,
python_version was accepted and validated but had no effect on TRT-LLM
deployments, with nothing surfacing that to the user.

Warn in trt_llm_common_validation() when python_version differs from its
default alongside a TRT-LLM config, matching the existing warning idiom
in the same function. This is additive only: the override behavior is
unchanged, existing configs just get visibility into it.

Fixes #2168
---
 truss/base/trt_llm_config.py               |  9 +++++++
 truss/tests/trt_llm/test_trt_llm_config.py | 28 ++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/truss/base/trt_llm_config.py b/truss/base/trt_llm_config.py
index 200c891ed..52bb5be41 100644
--- a/truss/base/trt_llm_config.py
+++ b/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
diff --git a/truss/tests/trt_llm/test_trt_llm_config.py b/truss/tests/trt_llm/test_trt_llm_config.py
index e005c22cc..f4fe231af 100644
--- a/truss/tests/trt_llm/test_trt_llm_config.py
+++ b/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