diff --git a/posit-bakery/posit_bakery/config/image/dev_version/base.py b/posit-bakery/posit_bakery/config/image/dev_version/base.py
index 024b59357..b34e2a03d 100644
--- a/posit-bakery/posit_bakery/config/image/dev_version/base.py
+++ b/posit-bakery/posit_bakery/config/image/dev_version/base.py
@@ -6,6 +6,7 @@
 from pydantic import Field, field_validator, model_validator
 
 from posit_bakery.config.image.build_os import DEFAULT_PLATFORMS
+from posit_bakery.config.image.os_validators import OSValidatorMixin
 from posit_bakery.config.image.posit_product.const import ReleaseChannelEnum
 from posit_bakery.config.image.version import ImageVersion
 from posit_bakery.config.image.version_os import ImageVersionOS
@@ -15,7 +16,7 @@
 log = logging.getLogger(__name__)
 
 
-class BaseImageDevelopmentVersion(BakeryYAMLModel, abc.ABC):
+class BaseImageDevelopmentVersion(OSValidatorMixin, BakeryYAMLModel, abc.ABC):
     """Base class for tool options in the bakery configuration."""
 
     parent: Annotated[BakeryYAMLModel | None, Field(exclude=True, default=None, description="Parent Image object.")]
@@ -76,85 +77,6 @@ def deduplicate_registries(cls, registries: list[Registry | BaseRegistry]) -> li
                 )
         return sorted(list(unique_registries), key=lambda r: r.base_url)
 
-    @field_validator("os", mode="after")
-    @classmethod
-    def check_os_not_empty(cls, os: list[ImageVersionOS]) -> list[ImageVersionOS]:
-        """Ensures that the os list is not empty.
-
-        :param os: List of ImageVersionOS objects to check.
-        :param info: ValidationInfo containing the data being validated.
-
-        :return: The unmodified list of ImageVersionOS objects.
-        """
-        # Check that name is defined since it will already propagate a validation error if not.
-        if not os:
-            log.warning(
-                f"No OSes defined for image development version. At least one OS should be "
-                "defined for complete tagging and labeling of images."
-            )
-        return os
-
-    @field_validator("os", mode="after")
-    @classmethod
-    def deduplicate_os(cls, os: list[ImageVersionOS]) -> list[ImageVersionOS]:
-        """Ensures that the os list is unique and warns on duplicates.
-
-        :param os: List of ImageVersionOS objects to deduplicate.
-        :param info: ValidationInfo containing the data being validated.
-
-        :return: A list of unique ImageVersionOS objects.
-        """
-        unique_oses = set(os)
-        for unique_os in unique_oses:
-            if os.count(unique_os) > 1:
-                log.warning(f"Duplicate OS defined in config for image development version: {unique_os.name}")
-
-        return sorted(list(unique_oses), key=lambda o: o.name)
-
-    @field_validator("os", mode="after")
-    @classmethod
-    def make_single_os_primary(cls, os: list[ImageVersionOS]) -> list[ImageVersionOS]:
-        """Ensures that at most one OS is marked as primary.
-
-        :param os: List of ImageVersionOS objects to check.
-        :param info: ValidationInfo containing the data being validated.
-
-        :return: The list of ImageVersionOS objects with at most one primary OS.
-        """
-        # If there's only one OS, mark it as primary by default.
-        if len(os) == 1:
-            # Skip warning if name already propagates an error.
-            if not os[0].primary:
-                os[0].primary = True
-
-        return os
-
-    @field_validator("os", mode="after")
-    @classmethod
-    def max_one_primary_os(cls, os: list[ImageVersionOS]) -> list[ImageVersionOS]:
-        """Ensures that at most one OS is marked as primary.
-
-        :param os: List of ImageVersionOS objects to check.
-        :param info: ValidationInfo containing the data being validated.
-
-        :return: The list of ImageVersionOS objects with at most one primary OS.
-
-        :raises ValueError: If more than one OS is marked as primary.
-        """
-        primary_os_count = sum(1 for o in os if o.primary)
-        if primary_os_count > 1:
-            raise ValueError(
-                f"Only one OS can be marked as primary for image development version. "
-                f"Found {primary_os_count} OSes marked primary."
-            )
-        elif primary_os_count == 0:
-            log.warning(
-                f"No OS marked as primary for image development version. "
-                "At least one OS should be marked as primary for complete tagging and labeling of images."
-            )
-
-        return os
-
     @model_validator(mode="after")
     def extra_registries_or_override_registries(self) -> Self:
         """Ensures that only one of extraRegistries or overrideRegistries is defined.
diff --git a/posit-bakery/posit_bakery/config/image/dev_version/channel.py b/posit-bakery/posit_bakery/config/image/dev_version/channel.py
index 9e9019a6a..926e1e341 100644
--- a/posit-bakery/posit_bakery/config/image/dev_version/channel.py
+++ b/posit-bakery/posit_bakery/config/image/dev_version/channel.py
@@ -99,7 +99,7 @@ def get_version(self) -> str:
         result = get_product_artifact_by_channel(
             self.product,
             self.channel,
-            _os.buildOS,
+            _os.artifact_build_os,
             release_branch=self.release_branch or "latest",
         )
         return result.version
@@ -114,7 +114,7 @@ def get_url_by_os(self, generalize_architecture: bool = False) -> dict[str, str]
             result = get_product_artifact_by_channel(
                 self.product,
                 self.channel,
-                _os.buildOS,
+                _os.artifact_build_os,
                 version_override=self.version_override,
                 release_branch=self.release_branch or "latest",
             )
@@ -147,7 +147,7 @@ def _resolve_os_urls(self) -> list[ImageVersionOS]:
                 result = get_product_artifact_by_channel(
                     self.product,
                     self.channel,
-                    os_version.buildOS,
+                    os_version.artifact_build_os,
                     version_override=self.version_override,
                     release_branch=self.release_branch or "latest",
                 )
diff --git a/posit-bakery/posit_bakery/config/image/matrix.py b/posit-bakery/posit_bakery/config/image/matrix.py
index 3bb315b6d..d137a5658 100644
--- a/posit-bakery/posit_bakery/config/image/matrix.py
+++ b/posit-bakery/posit_bakery/config/image/matrix.py
@@ -21,6 +21,7 @@
 
 from posit_bakery.config.dependencies.version import DependencyVersion, extract_versions, strip_patch
 from posit_bakery.config.image.build_os import TargetPlatform, DEFAULT_PLATFORMS
+from posit_bakery.config.image.os_validators import OSValidatorMixin
 from posit_bakery.config.registry import BaseRegistry, Registry
 from posit_bakery.config.shared import BakeryPathMixin, BakeryYAMLModel
 from posit_bakery.config.templating import jinja2_env
@@ -62,7 +63,7 @@ def generate_default_name_pattern(data: dict[str, Any]) -> str:
     return pattern
 
 
-class ImageMatrix(BakeryPathMixin, BakeryYAMLModel):
+class ImageMatrix(OSValidatorMixin, BakeryPathMixin, BakeryYAMLModel):
     """Model representing a matrix of a image value combinations to build."""
 
     parent: Annotated[
@@ -167,91 +168,6 @@ def deduplicate_registries(
                 )
         return sorted(list(unique_registries), key=lambda r: r.base_url)
 
-    @field_validator("os", mode="after")
-    @classmethod
-    def check_os_not_empty(cls, os: list[ImageVersionOS], info: ValidationInfo) -> list[ImageVersionOS]:
-        """Ensures that the os list is not empty.
-
-        :param os: List of ImageVersionOS objects to check.
-        :param info: ValidationInfo containing the data being validated.
-
-        :return: The unmodified list of ImageVersionOS objects.
-        """
-        # Check that name is defined since it will already propagate a validation error if not.
-        if info.data.get("namePattern") and not os:
-            log.warning(
-                f"No OSes defined for image matrix with name pattern '{info.data['namePattern']}'. At least one OS "
-                "should be defined for complete tagging and labeling of images."
-            )
-
-        return os
-
-    @field_validator("os", mode="after")
-    @classmethod
-    def deduplicate_os(cls, os: list[ImageVersionOS], info: ValidationInfo) -> list[ImageVersionOS]:
-        """Ensures that the os list is unique and warns on duplicates.
-
-        :param os: List of ImageVersionOS objects to deduplicate.
-        :param info: ValidationInfo containing the data being validated.
-
-        :return: A list of unique ImageVersionOS objects.
-        """
-        unique_oses = set(os)
-        for unique_os in unique_oses:
-            if info.data.get("namePattern") and os.count(unique_os) > 1:
-                log.warning(
-                    "Duplicate OS defined in config for image matrix with name pattern "
-                    f"'{info.data['namePattern']}': {unique_os.name}"
-                )
-
-        return sorted(list(unique_oses), key=lambda o: o.name)
-
-    @field_validator("os", mode="after")
-    @classmethod
-    def make_single_os_primary(cls, os: list[ImageVersionOS], info: ValidationInfo) -> list[ImageVersionOS]:
-        """Ensures that at most one OS is marked as primary.
-
-        :param os: List of ImageVersionOS objects to check.
-        :param info: ValidationInfo containing the data being validated.
-
-        :return: The list of ImageVersionOS objects with at most one primary OS.
-        """
-        # If there's only one OS, mark it as primary by default.
-        if len(os) == 1:
-            # Skip warning if name already propagates an error.
-            if info.data.get("namePattern") and not os[0].primary:
-                log.info(
-                    "Only one OS, {os[0].name}, defined for image matrix with name pattern "
-                    f"{info.data['namePattern']}. Marking it as primary OS."
-                )
-            os[0].primary = True
-        return os
-
-    @field_validator("os", mode="after")
-    @classmethod
-    def max_one_primary_os(cls, os: list[ImageVersionOS], info: ValidationInfo) -> list[ImageVersionOS]:
-        """Ensures that at most one OS is marked as primary.
-
-        :param os: List of ImageVersionOS objects to check.
-        :param info: ValidationInfo containing the data being validated.
-
-        :return: The list of ImageVersionOS objects with at most one primary OS.
-
-        :raises ValueError: If more than one OS is marked as primary.
-        """
-        primary_os_count = sum(1 for o in os if o.primary)
-        if info.data.get("namePattern") and primary_os_count > 1:
-            raise ValueError(
-                f"Only one OS can be marked as primary for image matrix with name pattern "
-                f"'{info.data['namePattern']}'. Found {primary_os_count} OSes marked primary."
-            )
-        elif info.data.get("namePattern") and primary_os_count == 0:
-            log.warning(
-                f"No OS marked as primary for image matrix with name pattern '{info.data['namePattern']}'. "
-                "At least one OS should be marked as primary for complete tagging and labeling of images."
-            )
-        return os
-
     @field_validator("dependencyConstraints", mode="after")
     @classmethod
     def check_duplicate_dependency_constraints(
diff --git a/posit-bakery/posit_bakery/config/image/os_validators.py b/posit-bakery/posit_bakery/config/image/os_validators.py
new file mode 100644
index 000000000..09f16ccf9
--- /dev/null
+++ b/posit-bakery/posit_bakery/config/image/os_validators.py
@@ -0,0 +1,128 @@
+import logging
+
+from pydantic import field_validator
+from pydantic_core.core_schema import ValidationInfo
+
+from posit_bakery.config.image.version_os import ImageVersionOS
+
+log = logging.getLogger(__name__)
+
+
+class OSValidatorMixin:
+    @field_validator("os", mode="after")
+    @classmethod
+    def check_os_not_empty(cls, os: list[ImageVersionOS], info: ValidationInfo) -> list[ImageVersionOS]:
+        """Ensures that the os list is not empty.
+
+        :param os: List of ImageVersionOS objects to check.
+        :param info: ValidationInfo containing the data being validated.
+
+        :return: The unmodified list of ImageVersionOS objects.
+        """
+        if not (info.data.get("name") or info.data.get("namePattern") or info.data.get("sourceType")):
+            return os
+        if not os:
+            log.warning(
+                "No OSes defined for the image configuration. At least one OS should be "
+                "defined for complete tagging and labeling of images."
+            )
+        return os
+
+    @field_validator("os", mode="after")
+    @classmethod
+    def deduplicate_os(cls, os: list[ImageVersionOS], info: ValidationInfo) -> list[ImageVersionOS]:
+        """Ensures that the os list is unique and warns on duplicates.
+
+        :param os: List of ImageVersionOS objects to deduplicate.
+        :param info: ValidationInfo containing the data being validated.
+
+        :return: A list of unique ImageVersionOS objects.
+        """
+        unique_oses = set(os)
+        for unique_os in unique_oses:
+            dupes = [o for o in os if o == unique_os]
+            if len(dupes) > 1:
+                artifact_os_values = {o.artifactOs for o in dupes}
+                if len(artifact_os_values) > 1:
+                    raise ValueError(
+                        f"Conflicting artifactOs values for OS '{unique_os.name}': "
+                        f"{sorted(str(v) for v in artifact_os_values)}. "
+                        "Each OS entry must have a consistent artifactOs."
+                    )
+                log.warning(f"Duplicate OS defined in the image configuration: {unique_os.name}")
+
+        return sorted(list(unique_oses), key=lambda o: o.name)
+
+    @field_validator("os", mode="after")
+    @classmethod
+    def make_single_os_primary(cls, os: list[ImageVersionOS], info: ValidationInfo) -> list[ImageVersionOS]:
+        """Ensures that a single OS entry is automatically marked as primary.
+
+        :param os: List of ImageVersionOS objects to check.
+        :param info: ValidationInfo containing the data being validated.
+
+        :return: The list of ImageVersionOS objects with the single OS marked primary.
+        """
+        # If there's only one OS, mark it as primary by default.
+        if len(os) == 1:
+            if not os[0].primary:
+                log.info(f"Only one OS defined; marking '{os[0].name}' as primary.")
+            os[0].primary = True
+        return os
+
+    @field_validator("os", mode="after")
+    @classmethod
+    def max_one_primary_os(cls, os: list[ImageVersionOS], info: ValidationInfo) -> list[ImageVersionOS]:
+        """Ensures that at most one OS is marked as primary.
+
+        :param os: List of ImageVersionOS objects to check.
+        :param info: ValidationInfo containing the data being validated.
+
+        :return: The list of ImageVersionOS objects with at most one primary OS.
+
+        :raises ValueError: If more than one OS is marked as primary.
+        """
+        if not (info.data.get("name") or info.data.get("namePattern") or info.data.get("sourceType")):
+            return os
+        primary_os_count = sum(1 for o in os if o.primary)
+        if primary_os_count > 1:
+            raise ValueError(
+                f"Only one OS can be marked as primary for the image configuration. "
+                f"Found {primary_os_count} OSes marked primary."
+            )
+        elif primary_os_count == 0:
+            log.warning(
+                "No OS marked as primary for the image configuration. "
+                "At least one OS should be marked as primary for complete tagging and labeling of images."
+            )
+        return os
+
+    # Must run after make_single_os_primary: Pydantic v2 runs field validators in
+    # declaration order within the class. Reordering this mixin will silently break
+    # the auto-promote invariant for single-OS scratch configs.
+    #
+    # Intentionally unguarded: an untaggable OS entry is always a config error
+    # regardless of whether the parent model's name/namePattern/sourceType is valid.
+    @field_validator("os", mode="after")
+    @classmethod
+    def error_untaggable_os(cls, os: list[ImageVersionOS], info: ValidationInfo) -> list[ImageVersionOS]:
+        """Ensures every non-primary OS has a tagDisplayName.
+
+        A non-primary OS with no tagDisplayName produces images that cannot be
+        reached by any tag — they are untaggable.
+
+        :param os: List of ImageVersionOS objects to check.
+        :param info: ValidationInfo containing the data being validated.
+
+        :return: The unmodified list of ImageVersionOS objects.
+
+        :raises ValueError: If a non-primary OS has an empty tagDisplayName.
+        """
+        for o in os:
+            if not o.tagDisplayName and not o.primary:
+                raise ValueError(
+                    f"OS entry '{o.name}' has an empty tagDisplayName but is not the primary OS. "
+                    "A non-primary OS with no tagDisplayName produces images that cannot be reached "
+                    "by any tag. Set it as primary or remove it from the image configuration."
+                )
+        return os
diff --git a/posit-bakery/posit_bakery/config/image/version.py b/posit-bakery/posit_bakery/config/image/version.py
index feede17d9..7d3e0e36b 100644
--- a/posit-bakery/posit_bakery/config/image/version.py
+++ b/posit-bakery/posit_bakery/config/image/version.py
@@ -11,6 +11,7 @@
 from pydantic_core.core_schema import ValidationInfo
 
 from posit_bakery.config.dependencies import DependencyVersionsField
+from posit_bakery.config.image.os_validators import OSValidatorMixin
 from posit_bakery.config.image.posit_product.const import ReleaseChannelEnum
 from posit_bakery.config.registry import BaseRegistry
 from posit_bakery.config.registry import Registry
@@ -27,7 +28,7 @@
 log = logging.getLogger(__name__)
 
 
-class ImageVersion(BakeryPathMixin, BakeryYAMLModel):
+class ImageVersion(OSValidatorMixin, BakeryPathMixin, BakeryYAMLModel):
     """Model representing a version of an image."""
 
     parent: Annotated[
@@ -174,87 +175,6 @@ def deduplicate_registries(
                 )
         return sorted(list(unique_registries), key=lambda r: r.base_url)
 
-    @field_validator("os", mode="after")
-    @classmethod
-    def check_os_not_empty(cls, os: list[ImageVersionOS], info: ValidationInfo) -> list[ImageVersionOS]:
-        """Ensures that the os list is not empty.
-
-        :param os: List of ImageVersionOS objects to check.
-        :param info: ValidationInfo containing the data being validated.
-
-        :return: The unmodified list of ImageVersionOS objects.
-        """
-        # Check that name is defined since it will already propagate a validation error if not.
-        if info.data.get("name") and not os:
-            log.warning(
-                f"No OSes defined for image version '{info.data['name']}'. At least one OS should be defined for "
-                f"complete tagging and labeling of images."
-            )
-        return os
-
-    @field_validator("os", mode="after")
-    @classmethod
-    def deduplicate_os(cls, os: list[ImageVersionOS], info: ValidationInfo) -> list[ImageVersionOS]:
-        """Ensures that the os list is unique and warns on duplicates.
-
-        :param os: List of ImageVersionOS objects to deduplicate.
-        :param info: ValidationInfo containing the data being validated.
-
-        :return: A list of unique ImageVersionOS objects.
-        """
-        unique_oses = set(os)
-        for unique_os in unique_oses:
-            if info.data.get("name") and os.count(unique_os) > 1:
-                log.warning(f"Duplicate OS defined in config for image version '{info.data['name']}': {unique_os.name}")
-
-        return sorted(list(unique_oses), key=lambda o: o.name)
-
-    @field_validator("os", mode="after")
-    @classmethod
-    def make_single_os_primary(cls, os: list[ImageVersionOS], info: ValidationInfo) -> list[ImageVersionOS]:
-        """Ensures that at most one OS is marked as primary.
-
-        :param os: List of ImageVersionOS objects to check.
-        :param info: ValidationInfo containing the data being validated.
-
-        :return: The list of ImageVersionOS objects with at most one primary OS.
-        """
-        # If there's only one OS, mark it as primary by default.
-        if len(os) == 1:
-            # Skip warning if name already propagates an error.
-            if info.data.get("name") and not os[0].primary:
-                log.info(
-                    f"Only one OS, {os[0].name}, defined for image version {info.data['name']}. Marking it as primary "
-                    f"OS."
-                )
-            os[0].primary = True
-        return os
-
-    @field_validator("os", mode="after")
-    @classmethod
-    def max_one_primary_os(cls, os: list[ImageVersionOS], info: ValidationInfo) -> list[ImageVersionOS]:
-        """Ensures that at most one OS is marked as primary.
-
-        :param os: List of ImageVersionOS objects to check.
-        :param info: ValidationInfo containing the data being validated.
-
-        :return: The list of ImageVersionOS objects with at most one primary OS.
-
-        :raises ValueError: If more than one OS is marked as primary.
-        """
-        primary_os_count = sum(1 for o in os if o.primary)
-        if primary_os_count > 1:
-            raise ValueError(
-                f"Only one OS can be marked as primary for image version '{info.data['name']}'. "
-                f"Found {primary_os_count} OSes marked primary."
-            )
-        elif info.data.get("name") and primary_os_count == 0:
-            log.warning(
-                f"No OS marked as primary for image version '{info.data['name']}'. "
-                "At least one OS should be marked as primary for complete tagging and labeling of images."
-            )
-        return os
-
     @field_validator("dependencies", mode="after")
     @classmethod
     def check_duplicate_dependencies(
diff --git a/posit-bakery/posit_bakery/config/image/version_os.py b/posit-bakery/posit_bakery/config/image/version_os.py
index 9e4d63d08..e2894879e 100644
--- a/posit-bakery/posit_bakery/config/image/version_os.py
+++ b/posit-bakery/posit_bakery/config/image/version_os.py
@@ -5,12 +5,49 @@
 from pydantic import BaseModel, Field, field_validator, field_serializer
 from pydantic_core.core_schema import ValidationInfo
 
-from posit_bakery.config.shared import BakeryYAMLModel, ExtensionField, TagDisplayNameField
+from posit_bakery.config.shared import BakeryYAMLModel
+from posit_bakery.const import (
+    REGEX_IMAGE_TAG_SUFFIX_ALLOWED_CHARACTERS_PATTERN,
+    REGEX_OS_EXTENSION_PATTERN,
+    REGEX_OS_TAG_DISPLAY_NAME_PATTERN,
+)
 from .build_os import BuildOS, SUPPORTED_OS, ALTERNATE_NAMES, TargetPlatform, DEFAULT_PLATFORMS
 from .posit_product.const import URL_WITH_ENV_VARS_REGEX_PATTERN
 
+_OSLESS_NAMES = frozenset({"scratch"})
+
 log = logging.getLogger(__name__)
 
+_NAME_VERSION_PATTERN = re.compile(r"(?P<name>[\D]+)(?P<version>[\d.]*)")
+
+
+def _resolve_name_to_build_os(name: str) -> BuildOS:
+    name = name.lower().strip()
+    match = _NAME_VERSION_PATTERN.match(name)
+    if not match:
+        log.warning(f"Could not identify '{name}' as a supported OS.")
+        return SUPPORTED_OS["unknown"]
+    match_dict = match.groupdict()
+    match_dict["name"] = match_dict.get("name", "").strip().rstrip("-")
+
+    if match_dict["name"] in ALTERNATE_NAMES:
+        match_dict["name"] = ALTERNATE_NAMES[match_dict["name"]]
+
+    if not match_dict.get("version"):
+        if match_dict["name"] in SUPPORTED_OS:
+            if isinstance(SUPPORTED_OS.get(match_dict["name"]), BuildOS):
+                return SUPPORTED_OS[match_dict["name"]]
+            else:
+                # Convert to int before max() to get numeric ordering (9 < 10), not lexical ("9" > "10")
+                latest = str(max([int(x) for x in SUPPORTED_OS[match_dict["name"]].keys()]))
+                return SUPPORTED_OS[match_dict["name"]][latest]
+    else:
+        match_dict["version"] = match_dict.get("version", "").split(".")[0]
+        if match_dict["name"] in SUPPORTED_OS and match_dict["version"] in SUPPORTED_OS.get(match_dict["name"]):
+            return SUPPORTED_OS[match_dict["name"]][match_dict["version"]]
+
+    return SUPPORTED_OS["unknown"]
+
 
 class ImageVersionOS(BakeryYAMLModel):
     """Model representing a supported operating system for an image version."""
@@ -33,16 +70,30 @@ class ImageVersionOS(BakeryYAMLModel):
         Field(default=DEFAULT_PLATFORMS, description="List of platforms to build for this image."),
     ]
     extension: Annotated[
-        ExtensionField,
+        str,
         Field(
+            default_factory=lambda data: (
+                ""
+                if data.get("name", "").lower().strip() in _OSLESS_NAMES
+                else re.sub(r"[^a-zA-Z0-9_-]", "", data.get("name", "").lower())
+            ),
+            pattern=REGEX_OS_EXTENSION_PATTERN,
+            validate_default=True,
             description="File extension used in the Containerfile filename in the pattern "
             "Containerfile.<os>.<variant> for this OS. Set to an empty string if no extension is needed.",
             examples=["ubuntu2204", "debian12"],
         ),
     ]
     tagDisplayName: Annotated[
-        TagDisplayNameField,
+        str,
         Field(
+            default_factory=lambda data: (
+                ""
+                if data.get("name", "").lower().strip() in _OSLESS_NAMES
+                else re.sub(REGEX_IMAGE_TAG_SUFFIX_ALLOWED_CHARACTERS_PATTERN, "-", data.get("name", "").lower())
+            ),
+            pattern=REGEX_OS_TAG_DISPLAY_NAME_PATTERN,
+            validate_default=True,
             description="The name used in image tags for this OS. This is used to create the tag "
             "in the format <image>:<version>-<os>-<variant>.",
             examples=["ubuntu-22.04", "debian-12"],
@@ -66,6 +117,14 @@ class ImageVersionOS(BakeryYAMLModel):
             pattern=URL_WITH_ENV_VARS_REGEX_PATTERN,
         ),
     ]
+    artifactOs: Annotated[
+        str | None,
+        Field(
+            default=None,
+            description="OS name for artifact download URL resolution when this OS cannot "
+            "resolve artifacts directly (e.g. scratch).",
+        ),
+    ]
 
     def __hash__(self):
         """Unique hash for an ImageVersionOS object."""
@@ -80,54 +139,34 @@ def __eq__(self, other):
             return hash(self) == hash(other)
         return False
 
+    @field_validator("artifactOs", mode="after")
+    @classmethod
+    def validate_artifact_os(cls, value: str | None) -> str | None:
+        if value is None:
+            return None
+        resolved = _resolve_name_to_build_os(value)
+        if resolved == SUPPORTED_OS["unknown"]:
+            raise ValueError(f"artifactOs '{value}' is not a recognized OS name")
+        return value
+
     @field_validator("buildOS", mode="after")
     @classmethod
     def populate_build_os(cls, value: BuildOS, info: ValidationInfo) -> BuildOS:
-        """Populates the build_os field based on the name field. If the OS cannot be determined, it defaults to unknown."""
-        # If the buildOS is already set to a known value, return it directly.
+        """Populates the buildOS field from the name field."""
         if isinstance(value, BuildOS) and value != SUPPORTED_OS["unknown"]:
             return value
-
-        name_pattern = re.compile(r"(?P<name>[\D]+)(?P<version>[\d.]*)")
         name = info.data.get("name")
         if name is None:
             return SUPPORTED_OS["unknown"]
-
-        name = name.lower().strip()
-        match = name_pattern.match(name)
-        if not match:
-            log.warning(f"Could not identify '{name}' as a supported OS.")
-            return SUPPORTED_OS["unknown"]
-        match_dict = match.groupdict()
-        match_dict["name"] = match_dict.get("name", "").strip()
-
-        # Handle possible alternate names for some OSes.
-        if match_dict["name"] in ALTERNATE_NAMES:
-            match_dict["name"] = ALTERNATE_NAMES[match_dict["name"]]
-
-        # Ideally, a name and version should be in the name field. If not, we try to infer an unversioned OS
-        # (such as scratch) or default to the latest version of a known OS.
-        if not match_dict.get("version"):
-            if match_dict["name"] in SUPPORTED_OS:
-                # If only the name is provided and it's an unversioned OS, use it.
-                if isinstance(SUPPORTED_OS.get(match_dict["name"]), BuildOS):
-                    return SUPPORTED_OS[match_dict["name"]]
-                # Otherwise, use the latest version of the matching OS name if possible.
-                else:
-                    # This line converts each version of the OS from a string to an int, finds the max, then converts it
-                    # back to a string. This ensures that we get the latest version numerically, not lexically.
-                    latest = str(max([int(x) for x in SUPPORTED_OS[match_dict["name"]].keys()]))
-                    return SUPPORTED_OS[match_dict["name"]][latest]
-        # Otherwise, assume a two-part name and version in the name field.
-        else:
-            match_dict["version"] = match_dict.get("version", "").split(".")[0]
-            # Check if the name and version are in the supported OS list.
-            if match_dict["name"] in SUPPORTED_OS and match_dict["version"] in SUPPORTED_OS.get(match_dict["name"]):
-                return SUPPORTED_OS[match_dict["name"]][match_dict["version"]]
-
-        return SUPPORTED_OS["unknown"]
+        return _resolve_name_to_build_os(name)
 
     @field_serializer("platforms")
     def serialize_platforms(self, platforms: list[TargetPlatform]) -> list[str]:
         """Serialize the platforms field to a list of strings for YAML output."""
         return [platform.value for platform in platforms]
+
+    @property
+    def artifact_build_os(self) -> BuildOS:
+        if self.artifactOs is not None:
+            return _resolve_name_to_build_os(self.artifactOs)
+        return self.buildOS
diff --git a/posit-bakery/posit_bakery/const.py b/posit-bakery/posit_bakery/const.py
index d8a3bd098..81320d9aa 100644
--- a/posit-bakery/posit_bakery/const.py
+++ b/posit-bakery/posit_bakery/const.py
@@ -24,6 +24,10 @@ class GetTagsOutputFormat(str, Enum):
     UID = "uid"
 
 
+# Extension allows letters, digits, underscores, and hyphens (e.g. "ubuntu2204").
+# Tag display names additionally allow dots (e.g. "ubuntu-22.04").
+REGEX_OS_EXTENSION_PATTERN = r"^[a-zA-Z0-9_-]*$"
+REGEX_OS_TAG_DISPLAY_NAME_PATTERN = r"^[a-zA-Z0-9_.-]*$"
 REGEX_FULL_IMAGE_TAG_PATTERN = (
     r"^(?P<repository>[\w.\-_]+((?::\d+|)(?=/[a-z0-9._-]+/[a-z0-9._-]+))|)"
     r"(?:/|)(?P<image>[a-z0-9.\-_]+(?:/[a-z0-9.\-_]+|))(:(?P<tag>[\w.\-_]{1,127})|)$"
diff --git a/posit-bakery/posit_bakery/image/image_target.py b/posit-bakery/posit_bakery/image/image_target.py
index 9009e5d9a..98beb4995 100644
--- a/posit-bakery/posit_bakery/image/image_target.py
+++ b/posit-bakery/posit_bakery/image/image_target.py
@@ -695,7 +695,7 @@ def build(
                     cache_from=cache_from,
                     cache_to=cache_to,
                     metadata_file=metadata_file,
-                    platforms=platforms or self.image_os.platforms,
+                    platforms=build_platforms,
                     target=self.build_target,
                     secrets=[s.as_cli_option() for s in self.resolved_build_secrets],
                     progress=False if SETTINGS.log_level >= logging.ERROR else "auto",
diff --git a/posit-bakery/test/cli/testdata/ci/matrix/multiversion/default.json b/posit-bakery/test/cli/testdata/ci/matrix/multiversion/default.json
new file mode 100644
index 000000000..699c5c863
--- /dev/null
+++ b/posit-bakery/test/cli/testdata/ci/matrix/multiversion/default.json
@@ -0,0 +1 @@
+[{"image": "test-image", "version": "2.0.0", "dev": false, "platform": "linux/amd64"}, {"image": "test-image", "version": "1.0.0", "dev": false, "platform": "linux/amd64"}]
diff --git a/posit-bakery/test/cli/testdata/get/tags/barebones/default.json b/posit-bakery/test/cli/testdata/get/tags/barebones/default.json
index a16069f47..b947d1e9b 100644
--- a/posit-bakery/test/cli/testdata/get/tags/barebones/default.json
+++ b/posit-bakery/test/cli/testdata/get/tags/barebones/default.json
@@ -3,9 +3,7 @@
         "1.0.0": {
             "Scratch": [
                 "ghcr.io/posit-dev/scratch:1.0.0",
-                "ghcr.io/posit-dev/scratch:1.0.0-scratch",
-                "ghcr.io/posit-dev/scratch:latest",
-                "ghcr.io/posit-dev/scratch:scratch"
+                "ghcr.io/posit-dev/scratch:latest"
             ]
         }
     }
diff --git a/posit-bakery/test/cli/testdata/get/tags/barebones/uid.json b/posit-bakery/test/cli/testdata/get/tags/barebones/uid.json
index 755f6f7b5..315441c46 100644
--- a/posit-bakery/test/cli/testdata/get/tags/barebones/uid.json
+++ b/posit-bakery/test/cli/testdata/get/tags/barebones/uid.json
@@ -1,8 +1,6 @@
 {
   "scratch-1-0-0-scratch": [
     "ghcr.io/posit-dev/scratch:1.0.0",
-    "ghcr.io/posit-dev/scratch:1.0.0-scratch",
-    "ghcr.io/posit-dev/scratch:latest",
-    "ghcr.io/posit-dev/scratch:scratch"
+    "ghcr.io/posit-dev/scratch:latest"
   ]
 }
diff --git a/posit-bakery/test/config/image/dev_version/test_channel.py b/posit-bakery/test/config/image/dev_version/test_channel.py
index b39b5e8f5..48f73db77 100644
--- a/posit-bakery/test/config/image/dev_version/test_channel.py
+++ b/posit-bakery/test/config/image/dev_version/test_channel.py
@@ -104,8 +104,8 @@ def test_check_os_not_empty(self, caplog):
 
         assert "WARNING" in caplog.text
         assert (
-            "No OSes defined for image development version. At least one OS should be defined "
-            "for complete tagging and labeling of images." in caplog.text
+            "No OSes defined for the image configuration. At least one OS should be "
+            "defined for complete tagging and labeling of images." in caplog.text
         )
 
     def test_deduplicate_os(self, caplog):
@@ -129,7 +129,7 @@ def test_deduplicate_os(self, caplog):
         assert len(i.os) == 1
         assert i.os[0].name == "Ubuntu 22.04"
         assert "WARNING" in caplog.text
-        assert "Duplicate OS defined in config for image development version: Ubuntu 22.04" in caplog.text
+        assert "Duplicate OS defined in the image configuration: Ubuntu 22.04" in caplog.text
 
     def test_make_single_os_primary(self, caplog):
         """Test that if only one OS is defined, it is automatically made primary."""
@@ -150,7 +150,7 @@ def test_max_one_primary_os(self):
         """Test that an error is raised if multiple primary OSes are defined."""
         with pytest.raises(
             ValidationError,
-            match="Only one OS can be marked as primary for image development version. Found 2 OSes marked primary.",
+            match="Only one OS can be marked as primary for the image configuration. Found 2 OSes marked primary.",
         ):
             with patch("posit_bakery.config.image.dev_version.channel.get_product_artifact_by_channel") as mock_get:
                 mock_get.return_value = ReleaseChannelResult(
@@ -181,8 +181,8 @@ def test_no_primary_os_warning(self, caplog):
 
         assert "WARNING" in caplog.text
         assert (
-            "No OS marked as primary for image development version. At least one OS should be "
-            "marked as primary for complete tagging and labeling of images." in caplog.text
+            "No OS marked as primary for the image configuration. "
+            "At least one OS should be marked as primary for complete tagging and labeling of images." in caplog.text
         )
 
     def test_extra_registries_or_override_registries(self):
@@ -1033,6 +1033,51 @@ def test_workbench_daily(
         assert dev_version.get_url_by_os()[_os.name] == expected_session_url
 
 
+class TestArtifactOsForScratch:
+    def test_resolve_os_urls_uses_artifact_os_for_scratch(self):
+        from posit_bakery.config.image.build_os import SUPPORTED_OS
+        from posit_bakery.config.image.posit_product.main import ReleaseChannelResult
+
+        expected_url = "https://cdn.posit.co/connect/daily/ubuntu2404/amd64/rstudio-connect_2026.05.0_amd64.deb"
+        with patch("posit_bakery.config.image.dev_version.channel.get_product_artifact_by_channel") as mock_get:
+            mock_get.return_value = ReleaseChannelResult(
+                version="2026.05.0",
+                download_url=expected_url,
+            )
+            version = ImageDevelopmentVersionFromProductChannel(
+                sourceType="stream",
+                product="connect",
+                channel="daily",
+                os=[{"name": "scratch", "artifactOs": "ubuntu-24.04"}],
+            )
+            resolved = version._resolve_os_urls()
+
+        for call in mock_get.call_args_list:
+            assert call.args[2] == SUPPORTED_OS["ubuntu"]["24"]
+        assert len(resolved) == 1
+        assert resolved[0].artifactDownloadURL == expected_url
+
+    def test_get_version_uses_artifact_os_for_scratch(self):
+        from posit_bakery.config.image.build_os import SUPPORTED_OS
+        from posit_bakery.config.image.posit_product.main import ReleaseChannelResult
+
+        with patch("posit_bakery.config.image.dev_version.channel.get_product_artifact_by_channel") as mock_get:
+            mock_get.return_value = ReleaseChannelResult(
+                version="2026.05.0",
+                download_url="https://cdn.posit.co/connect/daily/ubuntu2404/amd64/rstudio-connect_2026.05.0_amd64.deb",
+            )
+            version = ImageDevelopmentVersionFromProductChannel(
+                sourceType="stream",
+                product="connect",
+                channel="daily",
+                os=[{"name": "scratch", "artifactOs": "ubuntu-24.04", "primary": True}],
+            )
+            result = version.get_version()
+
+        assert result == "2026.05.0"
+        assert mock_get.call_args.args[2] == SUPPORTED_OS["ubuntu"]["24"]
+
+
 class TestResolveOsUrls:
     def test_sets_artifact_download_url(self):
         with patch("posit_bakery.config.image.dev_version.channel.get_product_artifact_by_channel") as mock_get:
diff --git a/posit-bakery/test/config/image/test_matrix.py b/posit-bakery/test/config/image/test_matrix.py
index c1679b73d..a10d2c55c 100644
--- a/posit-bakery/test/config/image/test_matrix.py
+++ b/posit-bakery/test/config/image/test_matrix.py
@@ -214,7 +214,7 @@ def test_check_os_not_empty(self, caplog):
         ImageMatrix(values={"go_version": ["1.24", "1.25"]}, os=[])
         assert "WARNING" in caplog.text
         assert (
-            "No OSes defined for image matrix with name pattern 'go_version{{ Values.go_version }}'. At least one OS should be "
+            "No OSes defined for the image configuration. At least one OS should be "
             "defined for complete tagging and labeling of images." in caplog.text
         )
 
@@ -233,9 +233,7 @@ def test_deduplicate_os(self, caplog):
         assert len(matrix.os) == 1
         assert matrix.os[0].name == "Ubuntu 22.04"
         assert "WARNING" in caplog.text
-        assert (
-            "Duplicate OS defined in config for image matrix with name pattern 'go_version{{ Values.go_version }}': Ubuntu 22.04"
-        ) in caplog.text
+        assert ("Duplicate OS defined in the image configuration: Ubuntu 22.04") in caplog.text
 
     def test_make_single_os_primary(self, caplog):
         """Test that if only one OS is defined, it is automatically made primary."""
@@ -249,7 +247,7 @@ def test_max_one_primary_os(self):
         """Test that an error is raised if multiple primary OSes are defined."""
         with pytest.raises(
             ValidationError,
-            match="Only one OS can be marked as primary for image matrix with name pattern 'go_version{{ Values.go_version }}'. Found 2 OSes marked primary.",
+            match="Only one OS can be marked as primary for the image configuration. Found 2 OSes marked primary.",
         ):
             ImageMatrix(
                 values={"go_version": ["1.24", "1.25"]},
@@ -264,8 +262,8 @@ def test_no_primary_os_warning(self, caplog):
         ImageMatrix(values={"go_version": ["1.24", "1.25"]}, os=[{"name": "Ubuntu 22.04"}, {"name": "Ubuntu 24.04"}])
         assert "WARNING" in caplog.text
         assert (
-            "No OS marked as primary for image matrix with name pattern 'go_version{{ Values.go_version }}'. At least one OS should be marked as primary for "
-            "complete tagging and labeling of images." in caplog.text
+            "No OS marked as primary for the image configuration. "
+            "At least one OS should be marked as primary for complete tagging and labeling of images." in caplog.text
         )
 
     def test_check_duplicate_dependencies(self):
diff --git a/posit-bakery/test/config/image/test_version.py b/posit-bakery/test/config/image/test_version.py
index 1723f2008..ba5e0a55b 100644
--- a/posit-bakery/test/config/image/test_version.py
+++ b/posit-bakery/test/config/image/test_version.py
@@ -91,8 +91,8 @@ def test_check_os_not_empty(self, caplog):
         ImageVersion(name="1.0.0", os=[])
         assert "WARNING" in caplog.text
         assert (
-            "No OSes defined for image version '1.0.0'. At least one OS should be defined for complete tagging and "
-            "labeling of images." in caplog.text
+            "No OSes defined for the image configuration. At least one OS should be "
+            "defined for complete tagging and labeling of images." in caplog.text
         )
 
     def test_deduplicate_os(self, caplog):
@@ -110,7 +110,21 @@ def test_deduplicate_os(self, caplog):
         assert len(i.os) == 1
         assert i.os[0].name == "Ubuntu 22.04"
         assert "WARNING" in caplog.text
-        assert "Duplicate OS defined in config for image version '1.0.0': Ubuntu 22.04" in caplog.text
+        assert "Duplicate OS defined in the image configuration: Ubuntu 22.04" in caplog.text
+
+    def test_conflicting_artifact_os_raises(self):
+        """Duplicate OS entries with different artifactOs values are a config error."""
+        mock_parent = MagicMock(spec=Image)
+        mock_parent.path = Path("/tmp/path")
+        with pytest.raises(ValidationError, match="Conflicting artifactOs values for OS 'scratch'"):
+            ImageVersion(
+                parent=mock_parent,
+                name="1.0.0",
+                os=[
+                    {"name": "scratch", "artifactOs": "ubuntu-22.04", "primary": True},
+                    {"name": "scratch", "artifactOs": "ubuntu-24.04"},
+                ],
+            )
 
     def test_make_single_os_primary(self, caplog):
         """Test that if only one OS is defined, it is automatically made primary."""
@@ -124,7 +138,7 @@ def test_max_one_primary_os(self):
         """Test that an error is raised if multiple primary OSes are defined."""
         with pytest.raises(
             ValidationError,
-            match="Only one OS can be marked as primary for image version '1.0.0'. Found 2 OSes marked primary.",
+            match="Only one OS can be marked as primary for the image configuration. Found 2 OSes marked primary.",
         ):
             ImageVersion(
                 name="1.0.0",
@@ -139,8 +153,8 @@ def test_no_primary_os_warning(self, caplog):
         ImageVersion(name="1.0.0", os=[{"name": "Ubuntu 22.04"}, {"name": "Ubuntu 24.04"}])
         assert "WARNING" in caplog.text
         assert (
-            "No OS marked as primary for image version '1.0.0'. At least one OS should be marked as primary for "
-            "complete tagging and labeling of images." in caplog.text
+            "No OS marked as primary for the image configuration. "
+            "At least one OS should be marked as primary for complete tagging and labeling of images." in caplog.text
         )
 
     def test_check_duplicate_dependencies(self):
@@ -712,3 +726,29 @@ def test_parsed_version_unparseable_returns_none_with_warning(self, caplog):
         assert v.parsed_version is None
         warnings = [r for r in caplog.records if "Unparseable version string" in r.message]
         assert len(warnings) == 1
+
+    def test_non_primary_scratch_os_raises(self):
+        with pytest.raises(ValidationError, match="empty tagDisplayName"):
+            ImageVersion(
+                name="2026.05.0",
+                os=[
+                    {"name": "scratch", "primary": False},
+                    {"name": "Ubuntu 22.04", "primary": True},
+                ],
+            )
+
+    def test_single_scratch_os_auto_promoted_to_primary(self):
+        v = ImageVersion(name="2026.05.0", os=[{"name": "scratch"}])
+        assert v.os[0].primary
+        assert v.os[0].tagDisplayName == ""
+
+    def test_explicit_primary_scratch_in_multi_os_passes(self):
+        v = ImageVersion(
+            name="2026.05.0",
+            os=[
+                {"name": "scratch", "primary": True},
+                {"name": "Ubuntu 22.04", "primary": False},
+            ],
+        )
+        scratch_entry = next(o for o in v.os if o.name.lower() == "scratch")
+        assert scratch_entry.primary
diff --git a/posit-bakery/test/config/image/test_version_os.py b/posit-bakery/test/config/image/test_version_os.py
index d9ba4e10b..cdb21fafe 100644
--- a/posit-bakery/test/config/image/test_version_os.py
+++ b/posit-bakery/test/config/image/test_version_os.py
@@ -122,6 +122,17 @@ def test_equality(self):
         assert os1 != os3
         assert os2 != os3
 
+    @pytest.mark.parametrize("name", ["scratch", "Scratch", "SCRATCH", " scratch "])
+    def test_scratch_derives_empty_extension_and_tag(self, name):
+        i = ImageVersionOS(name=name)
+        assert i.extension == ""
+        assert i.tagDisplayName == ""
+
+    def test_empty_extension_accepted_explicitly(self):
+        i = ImageVersionOS(name="Ubuntu 22.04", extension="", tagDisplayName="")
+        assert i.extension == ""
+        assert i.tagDisplayName == ""
+
     @pytest.mark.parametrize(
         "input_name,expected_build_os",
         [
@@ -146,6 +157,8 @@ def test_equality(self):
             ("Rocky Linux 10", SUPPORTED_OS["rocky"]["10"]),
             ("Rocky 9", SUPPORTED_OS["rocky"]["9"]),
             ("Rocky", SUPPORTED_OS["rocky"]["10"]),
+            ("Scratch", SUPPORTED_OS["scratch"]),
+            ("scratch", SUPPORTED_OS["scratch"]),
         ],
     )
     def test_populate_build_os(self, input_name, expected_build_os):
@@ -153,3 +166,29 @@ def test_populate_build_os(self, input_name, expected_build_os):
         os = ImageVersionOS(name=input_name)
 
         assert os.buildOS == expected_build_os
+
+
+class TestImageVersionOSArtifactOs:
+    def test_artifact_os_accepted_for_known_os(self):
+        i = ImageVersionOS(name="scratch", artifactOs="ubuntu-24.04")
+        assert i.artifactOs == "ubuntu-24.04"
+
+    def test_artifact_os_rejected_for_unknown_os(self):
+        with pytest.raises(ValidationError, match="not a recognized OS name"):
+            ImageVersionOS(name="scratch", artifactOs="not-a-real-os")
+
+    def test_artifact_os_defaults_to_none(self):
+        i = ImageVersionOS(name="scratch")
+        assert i.artifactOs is None
+
+    def test_artifact_build_os_returns_resolved_os_when_set(self):
+        i = ImageVersionOS(name="scratch", artifactOs="ubuntu-24.04")
+        assert i.artifact_build_os == SUPPORTED_OS["ubuntu"]["24"]
+
+    def test_artifact_build_os_falls_back_to_build_os_when_unset(self):
+        i = ImageVersionOS(name="Ubuntu 22.04")
+        assert i.artifact_build_os == SUPPORTED_OS["ubuntu"]["22"]
+
+    def test_artifact_build_os_for_scratch_without_artifact_os(self):
+        i = ImageVersionOS(name="scratch")
+        assert i.artifact_build_os == SUPPORTED_OS["scratch"]
diff --git a/posit-bakery/test/config/templating/test_render.py b/posit-bakery/test/config/templating/test_render.py
index 7c8a0ceb2..4fdd0caff 100644
--- a/posit-bakery/test/config/templating/test_render.py
+++ b/posit-bakery/test/config/templating/test_render.py
@@ -67,7 +67,7 @@ def test_regexReplace_filter(self):
         env = jinja2_env()
         assert env.from_string("{{ 'hello world' | regexReplace('world', 'there') }}").render() == "hello there"
         assert env.from_string("{{ 'foo-bar-baz' | regexReplace('-', '_') }}").render() == "foo_bar_baz"
-        assert env.from_string(r"{{ '123-456-789' | regexReplace('\d', 'X') }}").render() == "XXX-XXX-XXX"
+        assert env.from_string(r"{{ '123-456-789' | regexReplace('\\d', 'X') }}").render() == "XXX-XXX-XXX"
 
 
 def test_render_template():
diff --git a/posit-bakery/test/config/test_config.py b/posit-bakery/test/config/test_config.py
index d31a7d8b2..bee1a8e49 100644
--- a/posit-bakery/test/config/test_config.py
+++ b/posit-bakery/test/config/test_config.py
@@ -858,14 +858,14 @@ def test_create_version(self, get_tmpcontext):
         )
         assert expected_yaml in (context / "bakery.yaml").read_text()
         assert (context / image.name / new_version).is_dir()
-        assert (context / image.name / new_version / f"Containerfile.{previous_os.extension}").is_file()
+        containerfile_name = f"Containerfile.{previous_os.extension}" if previous_os.extension else "Containerfile"
+        assert (context / image.name / new_version / containerfile_name).is_file()
         expected_containerfile = textwrap.dedent("""\
         FROM scratch
 
         COPY scratch/2.0.0/deps/packages.txt /tmp/packages.txt
         """)
-        assert expected_containerfile == (context / image.name / new_version / "Containerfile.scratch").read_text()
-        assert (context / image.name / new_version / "Containerfile.scratch").is_file()
+        assert expected_containerfile == (context / image.name / new_version / containerfile_name).read_text()
         assert (context / image.name / new_version / "deps").is_dir()
         assert (context / image.name / new_version / "deps" / "packages.txt").is_file()
         assert (context / image.name / new_version / "test").is_dir()
@@ -895,13 +895,13 @@ def test_create_version_nested_subpath(self, get_tmpcontext):
         )
         assert expected_yaml in (context / "bakery.yaml").read_text()
         assert (context / "scratch" / "2" / "0" / "0").is_dir()
-        assert (context / "scratch" / "2" / "0" / "0" / "Containerfile.scratch").is_file()
+        assert (context / "scratch" / "2" / "0" / "0" / "Containerfile").is_file()
         expected_containerfile = textwrap.dedent("""\
         FROM scratch
 
         COPY scratch/2/0/0/deps/packages.txt /tmp/packages.txt
         """)
-        assert expected_containerfile == (context / "scratch" / "2" / "0" / "0" / "Containerfile.scratch").read_text()
+        assert expected_containerfile == (context / "scratch" / "2" / "0" / "0" / "Containerfile").read_text()
 
     def test_create_version_exists_force(self, get_tmpcontext):
         """Test creating an existing version in the BakeryConfig with force works."""
@@ -928,10 +928,10 @@ def test_create_version_exists_force(self, get_tmpcontext):
         )
         assert expected_yaml in (context / "bakery.yaml").read_text()
         assert (context / "scratch" / "1").is_dir()
-        assert (context / "scratch" / "1" / "Containerfile.scratch").is_file()
+        assert (context / "scratch" / "1" / "Containerfile").is_file()
         assert (
             "COPY scratch/1/deps/packages.txt /tmp/packages.txt"
-            in (context / "scratch" / "1" / "Containerfile.scratch").read_text()
+            in (context / "scratch" / "1" / "Containerfile").read_text()
         )
         assert not (context / "1.0.0").is_dir()
 
diff --git a/posit-bakery/test/features/cli/ci/matrix.feature b/posit-bakery/test/features/cli/ci/matrix.feature
index 243a794ba..bfd188960 100644
--- a/posit-bakery/test/features/cli/ci/matrix.feature
+++ b/posit-bakery/test/features/cli/ci/matrix.feature
@@ -47,3 +47,10 @@ Feature: matrix
             | --image-version | 9.9.9 |
         When I execute the command
         Then The command fails
+
+    Scenario: Generating a full CI matrix for the multiversion suite
+        Given I call bakery ci matrix
+        * in the multiversion context
+        When I execute the command
+        Then The command succeeds
+        * the matrix matches testdata ci/matrix/multiversion/default.json
diff --git a/posit-bakery/test/image/bake/testdata/cache_registry/barebones_plan.json b/posit-bakery/test/image/bake/testdata/cache_registry/barebones_plan.json
index b799058da..c733ba7cf 100644
--- a/posit-bakery/test/image/bake/testdata/cache_registry/barebones_plan.json
+++ b/posit-bakery/test/image/bake/testdata/cache_registry/barebones_plan.json
@@ -14,7 +14,7 @@
   "target": {
     "scratch-1-0-0-scratch": {
       "context": ".",
-      "dockerfile": "scratch/1.0.0/Containerfile.scratch",
+      "dockerfile": "scratch/1.0.0/Containerfile",
       "labels": {
         "org.opencontainers.image.created": "2025-01-01T00:00:00+00:00",
         "org.opencontainers.image.source": "https://github.com/posit-images-shared/posit-images-shared",
@@ -30,9 +30,7 @@
       },
       "tags": [
         "ghcr.io/posit-dev/scratch:1.0.0",
-        "ghcr.io/posit-dev/scratch:1.0.0-scratch",
-        "ghcr.io/posit-dev/scratch:latest",
-        "ghcr.io/posit-dev/scratch:scratch"
+        "ghcr.io/posit-dev/scratch:latest"
       ],
       "args": {},
       "platforms": [
@@ -41,13 +39,13 @@
       "cache_from": [
         {
           "type": "registry",
-          "ref": "ghcr.io/posit-dev/scratch/cache:1.0.0-scratch-amd64"
+          "ref": "ghcr.io/posit-dev/scratch/cache:1.0.0--amd64"
         }
       ],
       "cache_to": [
         {
           "type": "registry",
-          "ref": "ghcr.io/posit-dev/scratch/cache:1.0.0-scratch-amd64",
+          "ref": "ghcr.io/posit-dev/scratch/cache:1.0.0--amd64",
           "mode": "max",
           "compression": "zstd",
           "oci-mediatypes": "true"
diff --git a/posit-bakery/test/image/bake/testdata/default/barebones_plan.json b/posit-bakery/test/image/bake/testdata/default/barebones_plan.json
index 1fb21bbab..fe87abbd4 100644
--- a/posit-bakery/test/image/bake/testdata/default/barebones_plan.json
+++ b/posit-bakery/test/image/bake/testdata/default/barebones_plan.json
@@ -14,7 +14,7 @@
   "target": {
     "scratch-1-0-0-scratch": {
       "context": ".",
-      "dockerfile": "scratch/1.0.0/Containerfile.scratch",
+      "dockerfile": "scratch/1.0.0/Containerfile",
       "labels": {
         "org.opencontainers.image.created": "2025-01-01T00:00:00+00:00",
         "org.opencontainers.image.source": "https://github.com/posit-images-shared/posit-images-shared",
@@ -30,9 +30,7 @@
       },
       "tags": [
         "ghcr.io/posit-dev/scratch:1.0.0",
-        "ghcr.io/posit-dev/scratch:1.0.0-scratch",
-        "ghcr.io/posit-dev/scratch:latest",
-        "ghcr.io/posit-dev/scratch:scratch"
+        "ghcr.io/posit-dev/scratch:latest"
       ],
       "args": {},
       "platforms": [
diff --git a/posit-bakery/test/image/bake/testdata/temp_registry/barebones_plan.json b/posit-bakery/test/image/bake/testdata/temp_registry/barebones_plan.json
index 7076e2df2..9d6044289 100644
--- a/posit-bakery/test/image/bake/testdata/temp_registry/barebones_plan.json
+++ b/posit-bakery/test/image/bake/testdata/temp_registry/barebones_plan.json
@@ -14,7 +14,7 @@
   "target": {
     "scratch-1-0-0-scratch": {
       "context": ".",
-      "dockerfile": "scratch/1.0.0/Containerfile.scratch",
+      "dockerfile": "scratch/1.0.0/Containerfile",
       "labels": {
         "org.opencontainers.image.created": "2025-01-01T00:00:00+00:00",
         "org.opencontainers.image.source": "https://github.com/posit-images-shared/posit-images-shared",
diff --git a/posit-bakery/test/image/test_image_target.py b/posit-bakery/test/image/test_image_target.py
index c07546cb3..5d9bbaf89 100644
--- a/posit-bakery/test/image/test_image_target.py
+++ b/posit-bakery/test/image/test_image_target.py
@@ -1137,6 +1137,26 @@ def test_get_merge_sources_empty_metadata_no_sources(self, basic_standard_image_
 
         assert len(basic_standard_image_target.get_merge_sources()) == 0
 
+    def test_containerfile_with_scratch_os_has_no_os_component(self, basic_standard_image_target):
+        """Scratch OS (empty extension) with no variant produces a plain Containerfile."""
+        from posit_bakery.config import ImageVersionOS
+
+        basic_standard_image_target.image_os = ImageVersionOS(name="scratch")
+        basic_standard_image_target.image_variant = None
+        assert basic_standard_image_target.containerfile.name == "Containerfile"
+
+    @pytest.mark.build
+    def test_build_uses_build_platforms_when_image_os_is_none(self, basic_standard_image_target):
+        """build() uses DEFAULT_PLATFORMS when image_os is None instead of crashing."""
+        basic_standard_image_target.image_os = None
+        with (
+            patch("python_on_whales.docker.build") as mock_build,
+            patch("pathlib.Path.is_file", return_value=True),
+        ):
+            basic_standard_image_target.build()
+        call_kwargs = mock_build.call_args[1]
+        assert call_kwargs["platforms"] == ["linux/amd64"]
+
     def test_get_merge_sources_single_platform(self, basic_standard_image_target):
         """Test get_merge_sources works with single platform."""
         basic_standard_image_target.build_metadata = [
diff --git a/posit-bakery/test/plugins/builtin/dgoss/test_command.py b/posit-bakery/test/plugins/builtin/dgoss/test_command.py
index 5e9ee5a5e..4c53ea145 100644
--- a/posit-bakery/test/plugins/builtin/dgoss/test_command.py
+++ b/posit-bakery/test/plugins/builtin/dgoss/test_command.py
@@ -25,18 +25,16 @@ def test_from_image_target(self, basic_standard_image_target):
         assert basic_standard_image_target.context.version_path / "test" == dgoss_command.test_path
         assert dgoss_command.wait == 1
 
-    def test_dgoss_environment(self, basic_standard_image_target):
+    def test_dgoss_environment(self, basic_standard_image_target, monkeypatch):
         """Test that DGossCommand dgoss_environment returns the expected environment variables."""
+        monkeypatch.delenv("GITHUB_ACTIONS", raising=False)
         dgoss_command = DGossCommand.from_image_target(image_target=basic_standard_image_target)
         expected_env = {
             "GOSS_FILES_PATH": str(basic_standard_image_target.context.version_path / "test"),
             "GOSS_SLEEP": "1",
             "GOSS_OPTS": "--format json --no-color",
         }
-        for key, value in expected_env.items():
-            assert dgoss_command.dgoss_environment[key] == value, (
-                f"Expected {key} to be {value}, got {dgoss_command.dgoss_environment[key]}"
-            )
+        assert dgoss_command.dgoss_environment == expected_env
 
     def test_image_environment(self, basic_standard_image_target):
         """Test that DGossCommand image_environment returns the expected environment variables."""
diff --git a/posit-bakery/test/resources/barebones/bakery.yaml b/posit-bakery/test/resources/barebones/bakery.yaml
index de374f3aa..7640a47ad 100644
--- a/posit-bakery/test/resources/barebones/bakery.yaml
+++ b/posit-bakery/test/resources/barebones/bakery.yaml
@@ -16,3 +16,4 @@ images:
         latest: true
         os:
           - name: "Scratch"
+            extension: ""
diff --git a/posit-bakery/test/resources/barebones/scratch/1.0.0/Containerfile.scratch b/posit-bakery/test/resources/barebones/scratch/1.0.0/Containerfile
similarity index 100%
rename from posit-bakery/test/resources/barebones/scratch/1.0.0/Containerfile.scratch
rename to posit-bakery/test/resources/barebones/scratch/1.0.0/Containerfile
diff --git a/posit-bakery/test/resources/barebones/scratch/template/Containerfile.scratch.jinja2 b/posit-bakery/test/resources/barebones/scratch/template/Containerfile.jinja2
similarity index 100%
rename from posit-bakery/test/resources/barebones/scratch/template/Containerfile.scratch.jinja2
rename to posit-bakery/test/resources/barebones/scratch/template/Containerfile.jinja2
diff --git a/posit-bakery/test/resources/fail-fast/scratch/1.0.0/Containerfile.scratch.min b/posit-bakery/test/resources/fail-fast/scratch/1.0.0/Containerfile.min
similarity index 100%
rename from posit-bakery/test/resources/fail-fast/scratch/1.0.0/Containerfile.scratch.min
rename to posit-bakery/test/resources/fail-fast/scratch/1.0.0/Containerfile.min
diff --git a/posit-bakery/test/resources/fail-fast/scratch/1.0.0/Containerfile.scratch.std b/posit-bakery/test/resources/fail-fast/scratch/1.0.0/Containerfile.std
similarity index 100%
rename from posit-bakery/test/resources/fail-fast/scratch/1.0.0/Containerfile.scratch.std
rename to posit-bakery/test/resources/fail-fast/scratch/1.0.0/Containerfile.std
diff --git a/posit-bakery/test/resources/multiversion/bakery.yaml b/posit-bakery/test/resources/multiversion/bakery.yaml
new file mode 100644
index 000000000..a7a2d91bb
--- /dev/null
+++ b/posit-bakery/test/resources/multiversion/bakery.yaml
@@ -0,0 +1,23 @@
+repository:
+  url: "github.com/posit-dev/images-shared"
+  vendor: "Posit Software, PBC"
+  maintainer:
+    name: "Posit Docker Team"
+    email: "docker@posit.co"
+
+registries:
+  - host: "ghcr.io"
+    namespace: "posit-dev"
+
+images:
+  - name: "test-image"
+    versions:
+      - name: "2.0.0"
+        latest: true
+        os:
+          - name: Ubuntu 22.04
+            primary: true
+      - name: "1.0.0"
+        os:
+          - name: Ubuntu 22.04
+            primary: true