Fix forwarding ARN sequence lengths from QairtPipelinePass to QairtEncapsulationPass (microsoft#2526)

QairtEncapsulation uses sequence_lengths from model_attributes to
compute max_length in genai_config.json. QairtGenAIBuilder populates
this via its own config, but QairtPipelinePass had no equivalent path.
Extract the arn list from the genai_builder.transform_options in the
YAML recipe and pass it through model_attributes so QairtEncapsulation
can pick it up.

Previously caused an issue in execution where context length would be
exceeded and some kind of crash would occur

## Describe your changes

## Checklist before requesting a review
- [x] Add unit tests for this change.
- [x] Make sure all tests can pass.
- [x] Update documents if necessary.
- [x] Lint and apply fixes to your code by running `lintrunner -a`
- [x] Is this a user-facing change? If yes, give a description of this
change to be included in the release notes.

## (Optional) Issue link

Author: qti-kromero

olive/passes/qairt/pipeline.py

@@ -154,4 +154,12 @@ def _run_for_config(
             if src.exists() and not dst.exists():
                 shutil.copy2(src, dst)
 
-        return QairtModelHandler(model_path=output_model_path)
+        # Forward AR decode lengths to QairtEncapsulation so it can compute max_length correctly.
+        # arn in the pipeline recipe is the equivalent of sequence_lengths in QairtGenAIBuilder.
+        arn = recipe_data.get("stages", {}).get("genai_builder", {}).get("transform_options", {}).get("arn")
+        if arn is not None and (not isinstance(arn, list) or not arn or not all(isinstance(v, int) for v in arn)):
+            raise ValueError(
+                f"stages.genai_builder.transform_options.arn must be a non-empty list of integers, got: {arn!r}"
+            )
+        model_attrs = {"sequence_lengths": arn} if arn else {}
+        return QairtModelHandler(model_path=output_model_path, model_attributes=model_attrs)

test/passes/qairt/test_pipeline_pass.py

@@ -228,6 +228,79 @@ def test_pipeline_pass_missing_recipe_file(tmp_path, mock_hf_model, mock_pipelin
         pipeline_pass.run(mock_hf_model, str(output_path))
 
 
+def test_pipeline_pass_forwards_arn_as_sequence_lengths(tmp_path, mock_hf_model, recipe_file, mock_pipeline_modules):
+    """ARN from genai_builder.transform_options is forwarded as sequence_lengths in model_attributes."""
+    output_path = tmp_path / "output"
+
+    mock_pipeline_modules["Recipe"].from_file.return_value = {
+        "stages": {
+            "genai_builder": {
+                "transform_options": {
+                    "arn": [128, 1024, 4096],
+                }
+            }
+        }
+    }
+
+    pipeline_pass = create_pass_from_dict(
+        QairtPipelinePass,
+        {"recipe": str(recipe_file)},
+        disable_search=True,
+    )
+
+    result = pipeline_pass.run(mock_hf_model, str(output_path))
+
+    assert isinstance(result, QairtModelHandler)
+    assert result.model_attributes == {"sequence_lengths": [128, 1024, 4096]}
+
+
+@pytest.mark.parametrize(
+    "bad_arn",
+    [
+        "128,1024",  # string instead of list
+        1024,  # bare int
+        [],  # empty list
+        [128, "1024"],  # list with non-int element
+    ],
+)
+def test_pipeline_pass_invalid_arn_raises(tmp_path, mock_hf_model, recipe_file, mock_pipeline_modules, bad_arn):
+    """A malformed arn value raises ValueError with a clear message before propagating downstream."""
+    output_path = tmp_path / "output"
+
+    mock_pipeline_modules["Recipe"].from_file.return_value = {
+        "stages": {"genai_builder": {"transform_options": {"arn": bad_arn}}}
+    }
+
+    pipeline_pass = create_pass_from_dict(
+        QairtPipelinePass,
+        {"recipe": str(recipe_file)},
+        disable_search=True,
+    )
+
+    with pytest.raises(ValueError, match="must be a non-empty list of integers"):
+        pipeline_pass.run(mock_hf_model, str(output_path))
+
+
+def test_pipeline_pass_no_arn_yields_empty_model_attributes(
+    tmp_path, mock_hf_model, recipe_file, mock_pipeline_modules
+):
+    """When genai_builder.transform_options has no arn, sequence_lengths is not set in model_attributes."""
+    output_path = tmp_path / "output"
+
+    mock_pipeline_modules["Recipe"].from_file.return_value = {"stages": {"genai_builder": {"transform_options": {}}}}
+
+    pipeline_pass = create_pass_from_dict(
+        QairtPipelinePass,
+        {"recipe": str(recipe_file)},
+        disable_search=True,
+    )
+
+    result = pipeline_pass.run(mock_hf_model, str(output_path))
+
+    assert isinstance(result, QairtModelHandler)
+    assert "sequence_lengths" not in (result.model_attributes or {})
+
+
 def test_pipeline_pass_import_error(tmp_path, mock_hf_model, recipe_file):
     """Test that ImportError is raised if qairt cannot be imported."""