[BUG] [copilot] File extensions are missing when copilot downloads Blob/FlyteFile inputs

[ddl-rliu]

Flyte & Flytekit version

Flyte 1.16

Describe the bug

Copilot today has the following behavior:

# ContainerTask, as an example
def t1(file: FlyteFile["csv"]):
    ... # copilot downloads the file to e.g. /inputs/file

Sometimes, this is unintuitive (perhaps a bug? or an enhancement request? not clear...) and it may be expected that the file is downloaded to /inputs/file.csv instead.

Expected behavior

The file is downloaded to /inputs/file.csv instead. However, the "bugfix" must be done carefully, as it is likely that existing workflows are already expecting the file to be downloaded to /inputs/file.

Additional context to reproduce

No response

Screenshots

No response

Are you sure this issue hasn't been raised already?

• Yes

Have you read the Code of Conduct?

• Yes

[runllm]

It seems likely that Copilot currently downloads FlyteFile inputs without preserving the file extension, resulting in files like /inputs/file instead of /inputs/file.csv. This behavior is not explicitly documented as a bug or feature, but the expectation for extension preservation is reasonable, especially when using typed FlyteFile["csv"] inputs. However, changing this behavior could break existing workflows that rely on the current naming convention, so any fix should be backward-compatible or configurable.

The data sources do not explicitly document Copilot's file naming behavior for FlyteFile downloads, nor do they specify whether extensions are preserved or omitted. The FlyteFile documentation and code examples show that the file name (including extension) is maintained when downloading remote files, but do not clarify Copilot's handling in ContainerTask scenarios. Therefore, this issue is only partially addressed in the data sources, and a careful, configurable fix is advisable to avoid breaking existing workflows. Would you like a step-by-step breakdown of the relevant FlyteFile behaviors and possible mitigation strategies?

Sources:

• FlyteFile test cases

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[ddl-rliu]

Addressed by #7009 flyteorg/flytekit#3406