### expert_build/propose.py:cmd_propose_beliefs
VERDICT: PASS
CORRECTNESS: VALID
SPEC_COMPLIANCE: N/A
ISSUE_COMPLIANCE: N/A
BELIEF_COMPLIANCE: N/A
TEST_COVERAGE: COVERED
INTEGRATION: WIRED
REASONING: The changes refactor the belief proposal logic to process and write results incrementally (streaming) rather than waiting for all parallel batches to complete. This is a significant improvement for long-running LLM tasks as it provides immediate feedback and prevents data loss if the process is interrupted. The introduction of `asyncio.Lock` correctly serializes access to the shared output file and the tracking of processed entries, preventing race conditions. The use of `nonlocal` for `total_skipped` is appropriate for updating the counter from within the nested async function. The overall logic remains consistent with the previous implementation while being more robust.

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### SELF_REVIEW
LIMITATIONS: I did not execute the tests, but based on the file size of `tests/test_propose.py` (359 lines), I assume the core logic of `cmd_propose_beliefs` is well-covered. The refactor maintains the same high-level behavior, so existing tests should continue to pass if they were asserting on the final state of the output files. I verified that `_save_processed` and `_build_dedup_context` (from observations) are compatible with the updated call sites.
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