diff --git a/ml/rl/core/dataclasses.py b/ml/rl/core/dataclasses.py
index f35996175..b32e1270b 100644
--- a/ml/rl/core/dataclasses.py
+++ b/ml/rl/core/dataclasses.py
@@ -1,6 +1,10 @@
 #!/usr/bin/env python3
 
 
+import dataclasses
+import logging
+import os
+
 # Redirection to make import simpler
 from dataclasses import field  # noqa
 from typing import TYPE_CHECKING, Optional
@@ -8,8 +12,31 @@
 import pydantic
 
 
-class Config:
-    arbitrary_types_allowed = True
+try:
+    import fblearner.flow.api  # noqa
+
+    """
+    Inside FBLearner, we don't use pydantic for option parsing. Some types don't have
+    validator. This necessary to avoid pydantic complaining about validators.
+    """
+    USE_VANILLA_DATACLASS = True
+
+except ImportError:
+
+    USE_VANILLA_DATACLASS = False
+
+
+try:
+    # Allowing override, e.g., in unit test
+    USE_VANILLA_DATACLASS = bool(int(os.environ["USE_VANILLA_DATACLASS"]))
+except KeyError:
+    pass
+
+
+logger = logging.getLogger(__name__)
+
+
+logger.info(f"USE_VANILLA_DATACLASS: {USE_VANILLA_DATACLASS}")
 
 
 if TYPE_CHECKING:
@@ -23,16 +50,28 @@ class Config:
     def dataclass(
         _cls: Optional[pydantic.typing.AnyType] = None, *, config=None, **kwargs
     ):
-        """
-        Inside FB, we don't use pydantic for option parsing. Some types don't have
-        validator. This necessary to avoid pydantic complaining about validators.
-        """
+        def wrap(cls):
+            # We don't want to look at parent class
+            if "__post_init__" in cls.__dict__:
+                raise TypeError(
+                    f"{cls} has __post_init__. "
+                    "Please use __post_init_post_parse__ instead."
+                )
 
-        if config is None:
-            config = Config
+            if USE_VANILLA_DATACLASS:
+                try:
+                    post_init_post_parse = cls.__dict__["__post_init_post_parse__"]
+                    logger.info(
+                        f"Setting {cls.__name__}.__post_init__ to its "
+                        "__post_init_post_parse__"
+                    )
+                    cls.__post_init__ = post_init_post_parse
+                except KeyError:
+                    pass
 
-        def wrap(cls):
-            return pydantic.dataclasses.dataclass(cls, config=config, **kwargs)
+                return dataclasses.dataclass(**kwargs)(cls)
+            else:
+                return pydantic.dataclasses.dataclass(cls, **kwargs)
 
         if _cls is None:
             return wrap
diff --git a/ml/rl/core/registry_meta.py b/ml/rl/core/registry_meta.py
index 27ad5705e..d15fd151b 100644
--- a/ml/rl/core/registry_meta.py
+++ b/ml/rl/core/registry_meta.py
@@ -19,10 +19,21 @@ def __init__(cls, name, bases, attrs):
             logger.info("Adding REGISTRY to type {}".format(name))
             cls.REGISTRY: Dict[str, Type] = {}
             cls.REGISTRY_NAME = name
+            cls.REGISTRY_FROZEN = False
 
-        if not cls.__abstractmethods__:
+        assert not cls.REGISTRY_FROZEN, (
+            f"{cls.REGISTRY_NAME} has been used to fill a union. "
+            "Please rearrange your import orders"
+        )
+
+        if not cls.__abstractmethods__ and name != cls.REGISTRY_NAME:
             # Only register fully-defined classes
-            logger.info("Registering {} to {}".format(name, cls.REGISTRY_NAME))
+            logger.info(f"Registering {name} to {cls.REGISTRY_NAME}")
+            if hasattr(cls, "__registry_name__"):
+                registry_name = cls.__registry_name__
+                logger.info(f"Using {registry_name} instead of {name}")
+                name = registry_name
+            assert name not in cls.REGISTRY
             cls.REGISTRY[name] = cls
         else:
             logger.info(
@@ -33,6 +44,15 @@ def __init__(cls, name, bases, attrs):
 
     def fill_union(cls):
         def wrapper(union):
+            cls.REGISTRY_FROZEN = True
+
+            def make_union_instance(inst, instance_class=None):
+                inst_class = instance_class or type(inst)
+                key = getattr(inst_class, "__registry_name__", inst_class.__name__)
+                return union(**{key: inst})
+
+            union.make_union_instance = make_union_instance
+
             if issubclass(union, TaggedUnion):
                 # OSS TaggedUnion
                 union.__annotations__ = {
diff --git a/ml/rl/parameters_seq2slate.py b/ml/rl/parameters_seq2slate.py
index 19f7fa3b2..b29a2ed3d 100644
--- a/ml/rl/parameters_seq2slate.py
+++ b/ml/rl/parameters_seq2slate.py
@@ -1,10 +1,11 @@
 #!/usr/bin/env python3
 # Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.
 
-from dataclasses import dataclass
 from enum import Enum
 from typing import Optional
 
+from ml.rl.core.dataclasses import dataclass
+
 
 class LearningMethod(Enum):
     TEACHER_FORCING = "teacher_forcing"
diff --git a/ml/rl/workflow/model_managers/discrete_dqn_base.py b/ml/rl/workflow/model_managers/discrete_dqn_base.py
index 8fbec00cb..d96765bd4 100644
--- a/ml/rl/workflow/model_managers/discrete_dqn_base.py
+++ b/ml/rl/workflow/model_managers/discrete_dqn_base.py
@@ -19,6 +19,7 @@
     ReaderOptions,
     RewardOptions,
     RLTrainingOutput,
+    RLTrainingReport,
     TableSpec,
 )
 from ml.rl.workflow.utils import train_and_evaluate_generic
@@ -172,4 +173,7 @@ def train(
             evaluation_page_handler,
             reader_options=self.reader_options,
         )
-        return RLTrainingOutput(training_report=reporter.generate_training_report())
+        training_report = RLTrainingReport.make_union_instance(
+            reporter.generate_training_report()
+        )
+        return RLTrainingOutput(training_report=training_report)
diff --git a/ml/rl/workflow/publishers/model_publisher.py b/ml/rl/workflow/publishers/model_publisher.py
index b7bbd13bc..700fb9b21 100644
--- a/ml/rl/workflow/publishers/model_publisher.py
+++ b/ml/rl/workflow/publishers/model_publisher.py
@@ -1,11 +1,13 @@
 #!/usr/bin/env python3
 
 import abc
+import inspect
 from typing import Optional
 
 from ml.rl.core.registry_meta import RegistryMeta
 from ml.rl.workflow.model_managers.model_manager import ModelManager
-from ml.rl.workflow.types import PublishingOutput, RecurringPeriod, RLTrainingOutput
+from ml.rl.workflow.result_registries import PublishingResult
+from ml.rl.workflow.types import RecurringPeriod, RLTrainingOutput
 
 
 class ModelPublisher(metaclass=RegistryMeta):
@@ -14,7 +16,6 @@ class ModelPublisher(metaclass=RegistryMeta):
     they can be registered in the workflows.
     """
 
-    @abc.abstractmethod
     def publish(
         self,
         model_manager: ModelManager,
@@ -22,7 +23,38 @@ def publish(
         recurring_workflow_id: int,
         child_workflow_id: int,
         recurring_period: Optional[RecurringPeriod],
-    ) -> PublishingOutput:
+    ):
+        """
+        This method takes RLTrainingOutput so that it can extract anything it
+        might need from it.
+
+        ModelManager is given here so that config can be shared
+        """
+        result = self.do_publish(
+            model_manager,
+            training_output,
+            recurring_workflow_id,
+            child_workflow_id,
+            recurring_period,
+        )
+        # Avoid circular dependency at import time
+        from ml.rl.workflow.types import PublishingResult__Union
+
+        # We need to use inspection because the result can be a future when running on
+        # FBL
+        result_type = inspect.signature(self.do_publish).return_annotation
+        assert result_type != inspect.Signature.empty
+        return PublishingResult__Union.make_union_instance(result, result_type)
+
+    @abc.abstractmethod
+    def do_publish(
+        self,
+        model_manager: ModelManager,
+        training_output: RLTrainingOutput,
+        recurring_workflow_id: int,
+        child_workflow_id: int,
+        recurring_period: Optional[RecurringPeriod],
+    ) -> PublishingResult:
         """
         This method takes RLTrainingOutput so that it can extract anything it
         might need from it.
diff --git a/ml/rl/workflow/publishers/no_publishing.py b/ml/rl/workflow/publishers/no_publishing.py
index 453464974..6f44af4ac 100644
--- a/ml/rl/workflow/publishers/no_publishing.py
+++ b/ml/rl/workflow/publishers/no_publishing.py
@@ -5,8 +5,8 @@
 
 from ml.rl.workflow.model_managers.model_manager import ModelManager
 from ml.rl.workflow.publishers.model_publisher import ModelPublisher
-from ml.rl.workflow.result_types import NoPublishingResults, PublishingResults
-from ml.rl.workflow.types import PublishingOutput, RecurringPeriod, RLTrainingOutput
+from ml.rl.workflow.result_types import NoPublishingResults
+from ml.rl.workflow.types import RecurringPeriod, RLTrainingOutput
 
 
 @dataclass
@@ -17,15 +17,12 @@ class NoPublishing(ModelPublisher):
     some publishing.
     """
 
-    def publish(
+    def do_publish(
         self,
         model_manager: ModelManager,
         training_output: RLTrainingOutput,
         recurring_workflow_id: int,
         child_workflow_id: int,
         recurring_period: Optional[RecurringPeriod],
-    ) -> PublishingOutput:
-        return PublishingOutput(
-            success=True,
-            results=PublishingResults(no_publishing_results=NoPublishingResults()),
-        )
+    ) -> NoPublishingResults:
+        return NoPublishingResults(success=True)
diff --git a/ml/rl/workflow/result_registries.py b/ml/rl/workflow/result_registries.py
new file mode 100644
index 000000000..1eaf08095
--- /dev/null
+++ b/ml/rl/workflow/result_registries.py
@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+# Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.
+
+from ml.rl.core.dataclasses import dataclass
+from ml.rl.core.registry_meta import RegistryMeta
+
+
+class TrainingReport(metaclass=RegistryMeta):
+    pass
+
+
+@dataclass
+class PublishingResult(metaclass=RegistryMeta):
+    success: bool
+
+
+@dataclass
+class ValidationResult(metaclass=RegistryMeta):
+    should_publish: bool
diff --git a/ml/rl/workflow/result_types.py b/ml/rl/workflow/result_types.py
index e86ad92bd..5718809c4 100644
--- a/ml/rl/workflow/result_types.py
+++ b/ml/rl/workflow/result_types.py
@@ -1,26 +1,15 @@
 #!/usr/bin/env python3
-
-from typing import NamedTuple, Optional
+# Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.
 
 from ml.rl.core.dataclasses import dataclass
-from ml.rl.core.tagged_union import TaggedUnion
-
-
-class NoPublishingResults(NamedTuple):
-    pass
-
-
-class NoValidationResults(NamedTuple):
-    pass
+from ml.rl.workflow.result_registries import PublishingResult, ValidationResult
 
 
 @dataclass
-class PublishingResults(TaggedUnion):
-    no_publishing_results: Optional[NoPublishingResults] = None
-    # Add your own validation results type here
+class NoPublishingResults(PublishingResult):
+    __registry_name__ = "no_publishing_results"
 
 
 @dataclass
-class ValidationResults(TaggedUnion):
-    no_validation_results: Optional[NoValidationResults] = None
-    # Add your own validation results type here
+class NoValidationResults(ValidationResult):
+    __registry_name__ = "no_validation_results"
diff --git a/ml/rl/workflow/tagged_union.py b/ml/rl/workflow/tagged_union.py
new file mode 100644
index 000000000..1c5d69376
--- /dev/null
+++ b/ml/rl/workflow/tagged_union.py
@@ -0,0 +1,4 @@
+#!/usr/bin/env python3
+# Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.
+
+from ml.rl.core.tagged_union import TaggedUnion  # noqa F401
diff --git a/ml/rl/workflow/training.py b/ml/rl/workflow/training.py
index 6530d3055..b281b6fa9 100644
--- a/ml/rl/workflow/training.py
+++ b/ml/rl/workflow/training.py
@@ -1,5 +1,6 @@
 #!/usr/bin/env python3
 
+import dataclasses
 import logging
 from typing import Dict, NamedTuple, Optional, Tuple
 
@@ -8,10 +9,12 @@
 from ml.rl.workflow.model_managers.union import ModelManager__Union
 from ml.rl.workflow.publishers.union import ModelPublisher__Union
 from ml.rl.workflow.types import (
+    PublishingResult__Union,
     RecurringPeriod,
     RewardOptions,
     RLTrainingOutput,
     TableSpec,
+    ValidationResult__Union,
 )
 from ml.rl.workflow.validators.union import ModelValidator__Union
 
@@ -159,11 +162,11 @@ def run_validator(
     validator: ModelValidator__Union, training_output: RLTrainingOutput
 ) -> RLTrainingOutput:
     assert (
-        training_output.validation_output is None
+        training_output.validation_result is None
     ), f"validation_output was set to f{training_output.validation_output}"
     model_validator = validator.value
-    validation_output = model_validator.validate(training_output)
-    return training_output._replace(validation_output=validation_output)
+    validation_result = model_validator.validate(training_output)
+    return dataclasses.replace(training_output, validation_result=validation_result)
 
 
 def run_publisher(
@@ -175,15 +178,15 @@ def run_publisher(
     recurring_period: Optional[RecurringPeriod],
 ) -> RLTrainingOutput:
     assert (
-        training_output.publishing_output is None
+        training_output.publishing_result is None
     ), f"publishing_output was set to f{training_output.publishing_output}"
     model_publisher = publisher.value
     model_manager = model_chooser.value
-    publishing_output = model_publisher.publish(
+    publishing_result = model_publisher.publish(
         model_manager,
         training_output,
         recurring_workflow_id,
         child_workflow_id,
         recurring_period,
     )
-    return training_output._replace(publishing_output=publishing_output)
+    return dataclasses.replace(training_output, publishing_result=publishing_result)
diff --git a/ml/rl/workflow/types.py b/ml/rl/workflow/types.py
index 11dcaa7c0..cde1fd0bc 100644
--- a/ml/rl/workflow/types.py
+++ b/ml/rl/workflow/types.py
@@ -1,11 +1,13 @@
 #!/usr/bin/env python3
 # Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.
 
-from dataclasses import dataclass
 from datetime import datetime as RecurringPeriod  # noqa
 from typing import Dict, List, NamedTuple, Optional
 
-from ml.rl.core.tagged_union import TaggedUnion  # noqa F401
+# Triggering registration to registries
+import ml.rl.workflow.result_types  # noqa
+import ml.rl.workflow.training_reports  # noqa
+from ml.rl.core.dataclasses import dataclass
 from ml.rl.preprocessing.normalization import (
     DEFAULT_MAX_QUANTILE_SIZE,
     DEFAULT_MAX_UNIQUE_ENUM,
@@ -13,7 +15,12 @@
     DEFAULT_QUANTILE_K2_THRESHOLD,
 )
 from ml.rl.types import BaseDataClass
-from ml.rl.workflow.result_types import PublishingResults, ValidationResults
+from ml.rl.workflow.result_registries import (
+    PublishingResult,
+    TrainingReport,
+    ValidationResult,
+)
+from ml.rl.workflow.tagged_union import TaggedUnion  # noqa F401
 
 
 @dataclass
@@ -36,11 +43,23 @@ class PreprocessingOptions(BaseDataClass):
     assert_whitelist_feature_coverage: bool = True
 
 
-class PublishingOutput(NamedTuple):
-    success: bool
-    results: PublishingResults
+@PublishingResult.fill_union()
+class PublishingResult__Union(TaggedUnion):
+    pass
+
+
+@ValidationResult.fill_union()
+class ValidationResult__Union(TaggedUnion):
+    pass
 
 
-class ValidationOutput(NamedTuple):
-    should_publish: bool
-    results: ValidationResults
+@TrainingReport.fill_union()
+class RLTrainingReport(TaggedUnion):
+    pass
+
+
+@dataclass
+class RLTrainingOutput:
+    validation_result: Optional[ValidationResult__Union] = None
+    publishing_result: Optional[PublishingResult__Union] = None
+    training_report: Optional[RLTrainingReport] = None
diff --git a/ml/rl/workflow/validators/model_validator.py b/ml/rl/workflow/validators/model_validator.py
index e439c37fe..1e1860198 100644
--- a/ml/rl/workflow/validators/model_validator.py
+++ b/ml/rl/workflow/validators/model_validator.py
@@ -1,10 +1,12 @@
 #!/usr/bin/env python3
 
 import abc
+import inspect
 import logging
 
 from ml.rl.core.registry_meta import RegistryMeta
-from ml.rl.workflow.types import RLTrainingOutput, ValidationOutput
+from ml.rl.workflow.result_registries import ValidationResult
+from ml.rl.workflow.types import RLTrainingOutput
 
 
 logger = logging.getLogger(__name__)
@@ -16,8 +18,23 @@ class ModelValidator(metaclass=RegistryMeta):
     they can be registered in the workflows.
     """
 
+    def validate(self, training_output: RLTrainingOutput):
+        """
+        This method takes RLTrainingOutput so that it can extract anything it
+        might need from it.
+        """
+        result = self.do_validate(training_output)
+        # Avoid circular dependency at import time
+        from ml.rl.workflow.types import ValidationResult__Union
+
+        # We need to use inspection because the result can be a future when running on
+        # FBL
+        result_type = inspect.signature(self.do_validate).return_annotation
+        assert result_type != inspect.Signature.empty
+        return ValidationResult__Union.make_union_instance(result, result_type)
+
     @abc.abstractmethod
-    def validate(self, training_output: RLTrainingOutput) -> ValidationOutput:
+    def do_validate(self, training_output: RLTrainingOutput) -> ValidationResult:
         """
         This method takes RLTrainingOutput so that it can extract anything it
         might need from it.
diff --git a/ml/rl/workflow/validators/no_validation.py b/ml/rl/workflow/validators/no_validation.py
index a1c930973..8d0e6dea6 100644
--- a/ml/rl/workflow/validators/no_validation.py
+++ b/ml/rl/workflow/validators/no_validation.py
@@ -2,8 +2,8 @@
 
 from dataclasses import dataclass
 
-from ml.rl.workflow.result_types import NoValidationResults, ValidationResults
-from ml.rl.workflow.types import RLTrainingOutput, ValidationOutput
+from ml.rl.workflow.result_types import NoValidationResults
+from ml.rl.workflow.types import RLTrainingOutput
 from ml.rl.workflow.validators.model_validator import ModelValidator
 
 
@@ -15,8 +15,5 @@ class NoValidation(ModelValidator):
     some validation.
     """
 
-    def validate(self, training_output: RLTrainingOutput) -> ValidationOutput:
-        return ValidationOutput(
-            should_publish=True,
-            results=ValidationResults(no_validation_results=NoValidationResults()),
-        )
+    def do_validate(self, training_output: RLTrainingOutput) -> NoValidationResults:
+        return NoValidationResults(should_publish=True)