* fix(agents): keep null in the task output schema embedded in the prompt
build_task_prompt_with_schema embeds the task output schema into the prompt
via generate_model_description, whose strip_null_types defaults to True.
Combined with ensure_all_properties_required, an Optional[str] = None field
reaches the model as a required, non-nullable string, contradicting the
provider-side response schema generated from the same model.
That sanitizer targets OpenAI strict function-calling schemas. This call site
produces prompt prose, where those constraints do not apply.
Pass strip_null_types=False, matching the existing call for tool schemas in
utilities/agent_utils.py.
Fixes#6774
* test(agents): cover the output_json branch of the prompt schema
build_task_prompt_with_schema embeds a schema on both the output_json and
the output_pydantic branch, and this PR changes both. The regression test
only built a Task with output_pydantic, so the output_json branch shipped
unpinned.
Parameterize over both output attributes. Checked on this branch with the
fix reverted: both cases fail on the missing anyOf, and both pass with it.
Also compare the anyOf members as a set, so member order is not part of the
test contract.
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Co-authored-by: Vidit Ostwal <110953813+Vidit-Ostwal@users.noreply.github.com>
