feat(train): Auto-detect subscription recipe hyperparameters in SFTTrainer

When a model has subscription-gated recipes (IsSubscriptionModel: true
in RecipeCollection), automatically attempt to fetch the recipe's
override_params from the S3 access point and merge additional
hyperparameter keys into the trainer's _specs schema.

This allows subscribed users to natively set datamix hyperparameters
(e.g. customer_data_percent, nova_*_percent) via trainer.hyperparameters
without any explicit flag or workaround.

For non-subscribed users, the fetch fails silently (AccessDenied) and
only standard recipe hyperparameters are available. The extra latency
only occurs when subscription recipes exist in the hub metadata.

Changes:
- After loading standard override_params, check if any recipe has
  IsSubscriptionModel: true
- If found: resolve {customer_id} placeholder with caller's account ID,
  download override_params from access point, merge extra keys
- Handle S3 access point ARN URI format for GetObject
- Silent fallback on failure (non-subscribed users unaffected)
- Add unit tests for positive, negative, and fallback cases

Author: haardm

sagemaker-train/src/sagemaker/train/common_utils/finetune_utils.py

@@ -358,21 +358,58 @@ def _get_fine_tuning_options_and_model_arn(model_name: str, customization_techni
             raise ValueError(f"No recipes found with Smtj for technique: {customization_technique}")
 
         # Select recipe based on training type
+        # Collect override_params from ALL matching recipes (standard + subscription)
         recipe = None
         if (isinstance(training_type, TrainingType) and training_type == TrainingType.LORA) or training_type == "LORA":
-            recipe = next((r for r in recipes_with_template if r.get("Peft")), None)
+            recipe = next((r for r in recipes_with_template if r.get("Peft") and not r.get("IsSubscriptionModel")), None)
         elif (isinstance(training_type, TrainingType) and training_type == TrainingType.FULL) or training_type == "FULL":
-            recipe = next((r for r in recipes_with_template if not r.get("Peft")), None)
+            recipe = next((r for r in recipes_with_template if not r.get("Peft") and not r.get("IsSubscriptionModel")), None)
 
         if not recipe:
             raise ValueError(f"No recipes found with Smtj for technique: {customization_technique},training_type:{training_type}")
 
-        elif recipe and recipe.get("SmtjOverrideParamsS3Uri"):
+        # Start with the standard recipe's override_params
+        options_dict = {}
+        if recipe.get("SmtjOverrideParamsS3Uri"):
             s3_uri = recipe["SmtjOverrideParamsS3Uri"]
-            s3 = boto3.client("s3")
-            bucket, key = s3_uri.replace("s3://", "").split("/", 1)
+            s3 = sagemaker_session.boto_session.client("s3")
+            uri_path = s3_uri.replace("s3://", "")
+            bucket, key = uri_path.split("/", 1)
             obj = s3.get_object(Bucket=bucket, Key=key)
             options_dict = json.loads(obj["Body"].read())
+
+        # Auto-detect and merge subscription recipe's override_params if available
+        if (isinstance(training_type, TrainingType) and training_type == TrainingType.LORA) or training_type == "LORA":
+            sub_recipe = next((r for r in recipes_with_template if r.get("Peft") and r.get("IsSubscriptionModel")), None)
+        else:
+            sub_recipe = next((r for r in recipes_with_template if not r.get("Peft") and r.get("IsSubscriptionModel")), None)
+
+        if sub_recipe and sub_recipe.get("SmtjOverrideParamsS3Uri"):
+            try:
+                sub_s3_uri = sub_recipe["SmtjOverrideParamsS3Uri"].replace("{customer_id}", sagemaker_session.boto_session.client("sts").get_caller_identity()["Account"])
+                sub_uri_path = sub_s3_uri.replace("s3://", "")
+                # Handle access point ARN URIs
+                if sub_uri_path.startswith("arn:"):
+                    arn_parts = sub_uri_path.split("/", 2)
+                    sub_bucket = arn_parts[0] + "/" + arn_parts[1]
+                    sub_key = arn_parts[2] if len(arn_parts) > 2 else ""
+                else:
+                    sub_bucket, sub_key = sub_uri_path.split("/", 1)
+                s3_sub = sagemaker_session.boto_session.client("s3")
+                sub_obj = s3_sub.get_object(Bucket=sub_bucket, Key=sub_key)
+                sub_options = json.loads(sub_obj["Body"].read())
+                # Merge: subscription params into _specs only (don't set defaults)
+                # This makes them settable but not serialized unless user explicitly sets them
+                for k, v in sub_options.items():
+                    if k not in options_dict:
+                        v_copy = v.copy() if isinstance(v, dict) else v
+                        if isinstance(v_copy, dict):
+                            v_copy['default'] = None  # No default — won't appear in to_dict() unless set
+                        options_dict[k] = v_copy
+            except Exception as e:
+                logger.debug(f"Could not fetch subscription recipe override_params: {type(e).__name__}: {e}")
+
+        if options_dict:
             return FineTuningOptions(options_dict), model_arn, is_gated_model
         else:
             return FineTuningOptions({}), model_arn, is_gated_model

sagemaker-train/tests/unit/train/common_utils/test_finetune_utils.py

@@ -1,3 +1,4 @@
+import json
 import pytest
 from unittest.mock import Mock, patch, MagicMock
 from sagemaker.train.common_utils.finetune_utils import (
@@ -304,6 +305,8 @@ def test__get_fine_tuning_options_and_model_arn(self, mock_boto_client, mock_get
         mock_s3_client.get_object.return_value = {
             "Body": Mock(read=Mock(return_value=b'{"learning_rate": 0.001}'))
         }
+        mock_session.boto_session.client.return_value = mock_s3_client
+        mock_session.boto_session.client.return_value = mock_s3_client
 
         result = _get_fine_tuning_options_and_model_arn("test-model", "SFT", "LORA", mock_session)
 
@@ -551,3 +554,140 @@ def test__validate_s3_path_exists_with_prefix_not_exists(self, mock_boto_client)
         mock_s3_client.put_object.assert_called_once_with(Bucket="test-bucket", Key="prefix/", Body=b'')
 
 
+
+    @patch('sagemaker.train.common_utils.finetune_utils._get_hub_content_metadata')
+    def test__get_fine_tuning_options_with_subscription_recipe_enabled(self, mock_get_hub_content):
+        """When  and user is subscribed, datamix HPs are available."""
+        mock_session = Mock()
+        mock_session.boto_session.region_name = "us-east-1"
+        mock_s3 = Mock()
+        mock_sts = Mock()
+        mock_sts.get_caller_identity.return_value = {"Account": "123456789012"}
+        mock_session.boto_session.client.side_effect = lambda service, **kwargs: mock_s3 if service == "s3" else mock_sts
+
+        mock_get_hub_content.return_value = {
+            'hub_content_arn': "arn:aws:sagemaker:us-east-1:123456789012:model/test-model",
+            'hub_content_document': {
+                "GatedBucket": False,
+                "RecipeCollection": [
+                    {
+                        "CustomizationTechnique": "SFT",
+                        "SmtjRecipeTemplateS3Uri": "s3://bucket/template.yaml",
+                        "SmtjOverrideParamsS3Uri": "s3://bucket/standard_params.json",
+                        "Name": "standard_sft"
+                    },
+                    {
+                        "CustomizationTechnique": "SFT",
+                        "SmtjRecipeTemplateS3Uri": "s3://arn:aws:s3:us-east-1:334772094012:accesspoint/recipes-123456789012/source/template.yaml",
+                        "SmtjOverrideParamsS3Uri": "s3://arn:aws:s3:us-east-1:334772094012:accesspoint/recipes-{customer_id}/source/params.json",
+                        "Name": "datamix_sft",
+                        "IsSubscriptionModel": True
+                    }
+                ]
+            }
+        }
+
+        # Standard recipe returns base params
+        standard_params = json.dumps({"max_steps": {"type": "integer", "required": True, "default": 100}})
+        # Subscription recipe returns datamix params
+        datamix_params = json.dumps({"customer_data_percent": {"type": "integer", "required": False, "default": 50}})
+
+        mock_s3.get_object.side_effect = [
+            {"Body": Mock(read=Mock(return_value=standard_params.encode()))},
+            {"Body": Mock(read=Mock(return_value=datamix_params.encode()))},
+        ]
+
+        options, model_arn, is_gated = _get_fine_tuning_options_and_model_arn(
+            "test-model", "SFT", "FULL", mock_session, 
+        )
+
+        assert "max_steps" in options._specs
+        assert "customer_data_percent" in options._specs
+        assert options._specs["customer_data_percent"]["default"] is None  # defaults are None so they dont serialize unless explicitly set
+
+    @patch('sagemaker.train.common_utils.finetune_utils._get_hub_content_metadata')
+    def test__get_fine_tuning_options_subscription_disabled_no_datamix_hps(self, mock_get_hub_content):
+        """When  (default), datamix HPs are NOT available."""
+        mock_session = Mock()
+        mock_session.boto_session.region_name = "us-east-1"
+        mock_s3 = Mock()
+        mock_session.boto_session.client.side_effect = lambda service, **kwargs: mock_s3
+
+        mock_get_hub_content.return_value = {
+            'hub_content_arn': "arn:aws:sagemaker:us-east-1:123456789012:model/test-model",
+            'hub_content_document': {
+                "GatedBucket": False,
+                "RecipeCollection": [
+                    {
+                        "CustomizationTechnique": "SFT",
+                        "SmtjRecipeTemplateS3Uri": "s3://bucket/template.yaml",
+                        "SmtjOverrideParamsS3Uri": "s3://bucket/standard_params.json",
+                        "Name": "standard_sft"
+                    },
+                    {
+                        "CustomizationTechnique": "SFT",
+                        "SmtjRecipeTemplateS3Uri": "s3://arn:aws:s3:us-east-1:334772094012:accesspoint/recipes-{customer_id}/source/template.yaml",
+                        "SmtjOverrideParamsS3Uri": "s3://arn:aws:s3:us-east-1:334772094012:accesspoint/recipes-{customer_id}/source/params.json",
+                        "Name": "datamix_sft",
+                        "IsSubscriptionModel": True
+                    }
+                ]
+            }
+        }
+
+        standard_params = json.dumps({"max_steps": {"type": "integer", "required": True, "default": 100}})
+        mock_s3.get_object.return_value = {"Body": Mock(read=Mock(return_value=standard_params.encode()))}
+
+        options, model_arn, is_gated = _get_fine_tuning_options_and_model_arn(
+            "test-model", "SFT", "FULL", mock_session, 
+        )
+
+        assert "max_steps" in options._specs
+        assert "customer_data_percent" not in options._specs
+
+    @patch('sagemaker.train.common_utils.finetune_utils._get_hub_content_metadata')
+    def test__get_fine_tuning_options_subscription_enabled_but_not_subscribed(self, mock_get_hub_content):
+        """When  but user is NOT subscribed, falls back gracefully."""
+        mock_session = Mock()
+        mock_session.boto_session.region_name = "us-east-1"
+        mock_s3 = Mock()
+        mock_sts = Mock()
+        mock_sts.get_caller_identity.return_value = {"Account": "999999999999"}
+        mock_session.boto_session.client.side_effect = lambda service, **kwargs: mock_s3 if service == "s3" else mock_sts
+
+        mock_get_hub_content.return_value = {
+            'hub_content_arn': "arn:aws:sagemaker:us-east-1:123456789012:model/test-model",
+            'hub_content_document': {
+                "GatedBucket": False,
+                "RecipeCollection": [
+                    {
+                        "CustomizationTechnique": "SFT",
+                        "SmtjRecipeTemplateS3Uri": "s3://bucket/template.yaml",
+                        "SmtjOverrideParamsS3Uri": "s3://bucket/standard_params.json",
+                        "Name": "standard_sft"
+                    },
+                    {
+                        "CustomizationTechnique": "SFT",
+                        "SmtjRecipeTemplateS3Uri": "s3://arn:aws:s3:us-east-1:334772094012:accesspoint/recipes-{customer_id}/source/template.yaml",
+                        "SmtjOverrideParamsS3Uri": "s3://arn:aws:s3:us-east-1:334772094012:accesspoint/recipes-{customer_id}/source/params.json",
+                        "Name": "datamix_sft",
+                        "IsSubscriptionModel": True
+                    }
+                ]
+            }
+        }
+
+        standard_params = json.dumps({"max_steps": {"type": "integer", "required": True, "default": 100}})
+        # First call succeeds (standard recipe), second call fails (access denied)
+        mock_s3.get_object.side_effect = [
+            {"Body": Mock(read=Mock(return_value=standard_params.encode()))},
+            Exception("Access Denied"),
+        ]
+
+        options, model_arn, is_gated = _get_fine_tuning_options_and_model_arn(
+            "test-model", "SFT", "FULL", mock_session, 
+        )
+
+        # Should still have standard params, just not datamix ones
+        assert "max_steps" in options._specs
+        assert "customer_data_percent" not in options._specs