docs(security): Option A (uninstall pyarrow) probed and rejected — record why

[brownjuly2003-code]

What

Comment-only follow-up to #228. The external-review suggestion "eliminate the last safety ignore by uninstalling unused pyarrow from the Flink image" was probed in the real agentflow-flink-local image before touching any code, and it fails:

pip uninstall -y pyarrow
python -c "import apache_beam"
  File ".../apache_beam/io/__init__.py", line 28: from apache_beam.io.parquetio import *
  File ".../apache_beam/io/parquetio.py", line 161, in _ArrowTableToBeamRows
    def process(self, element) -> Iterator[pa.Table]:
AttributeError: 'NoneType' object has no attribute 'Table'

beam 2.61 soft-imports pyarrow (pa = None on failure) but its parquetio class bodies evaluate pa.Table annotations at import time — so the whole beam package (which the PyFlink harness imports) is unimportable without pyarrow. The record goes into the ignore comment so the idea is not re-opened by a future session or audit.

Probe context: image probes also confirmed the positive claims from the review — submit-side and beam-worker imports succeed with pyarrow present, and the import-attempt trace shows pyarrow is pulled in via apache_beam.io.parquetio, not by any PyFlink DataStream path.

Verification

• yaml.safe_load OK; tests/unit/test_security_workflow.py passes.

🤖 Generated with Claude Code

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