#668 [Breaking] Add extendable parameter to Image class Pull request opened by pingsutw ## Summary This PR adds an

extendable

parameter to the

Image

class to control whether additional layers can be added to an image after creation. This feature enables users to: • Create base images that can be extended with additional layers (default behavior) • Lock down final production images to prevent accidental modifications • Explicitly control image mutability throughout the image building pipeline ## Changes ### Core Implementation • Added

extendable: bool = field(default=True)

to the

Image

dataclass • Updated

Image.clone()

method to accept and preserve the

extendable

parameter • Added validation in

clone()

to prevent adding layers to non-extendable images • The extendable property is preserved when cloning without explicitly specifying it ### Examples Updated Updated all examples that use

.clone()

followed by layer additions to explicitly set `extendable=True`: •

examples/basics/frames.py

•

examples/connectors/databricks_example.py

•

examples/genai/anthropic_deep_research_agent.py

•

examples/genai/anthropic_pbj_agent.py

•

examples/image/clone_existing_image.py

(with documentation) •

examples/image/private_base_image.py

•

examples/plugins/spark_dataframe_example.py

•

examples/plugins/spark_example.py

### New Example • Added

examples/image/extendable_image.py

demonstrating comprehensive usage of the extendable parameter ### Tests Added comprehensive unit tests covering: • Default extendable behavior • Setting extendable to False • Preventing layer additions to non-extendable images • Preserving extendable value on clone • Changing extendable value on clone • Allowing layers on extendable images ## Behavior Default (extendable=True): img = Image.from_debian_base(registry="ghcr.io/myorg", name="myapp") img = img.with_pip_packages("numpy") # ✓ Works Non-extendable (extendable=False): img = Image.from_debian_base(registry="ghcr.io/myorg", name="myapp") final_img = img.clone(name="final", extendable=False) final_img.with_pip_packages("numpy") # ✗ Raises ValueError Making extendable again: new_img = final_img.clone(name="new", extendable=True) new_img.with_pip_packages("numpy") # ✓ Works ## Test Plan 1. Run unit tests:

pytest tests/flyte/test_image.py::test_extendable*

2. Verify examples run without errors 3. Test that non-extendable images properly reject layer additions 4. Verify backward compatibility - existing code continues to work (default is True) ## Breaking Changes None. This is a backward-compatible addition with

extendable=True

as the default. flyteorg/flyte-sdk