[lmeyerov]

Summary

• Lower Cypher = null comparisons to an explicit never_match predicate so they cannot be overwritten as "no existing predicate" during conjunction composition.
• Preserve raw JSON filter_dict={"v": None} no-match semantics.
• Add focused pandas, Polars, and cuDF coverage for operand order, conjunctions, IS NULL, NOT, OR, projection, and strict missing-property behavior.
• Add changelog entry.

Evidence

• Integrated head: abe80de830df63d1e2dfefe6fc3e033192be2f72, tree f982721664955eb44f4007480eb9a4471b0053c8, base/master 682b6a5e3bafd1c68d37690509148ca2c63fc232.
• Integrated CPU/Polars focused lanes: 69 passed, 15 skipped; Ruff, surface guard, full type-hygiene guard, and diff-check pass.
• The broad conformance matrix was not treated as local CPU evidence because its cuDF selection hits the host's known CUDA allocation failure. Hosted exact-head lanes remain the integration gate.
• The earlier DGX 40 passed run is retained as historical evidence for the pre-integration head; it does not certify this rebased head.
• Final-head DGX runtime control passed on cuDF 26.02.01; focused exact-head GPU suite is 15 passed, 31 deselected. Receipt: worker/receipts/abe80de83-2236-final-cudf.md.
• Exact base: 5cb023e1ee524c1eafd10ef13e50a88e7b15100d
• Exact head: 3e2bd2130d08123acc268529f8db04436abe2a75
• Final amended head: 0e5c11262c83f75348404b9358bfb95f36676c53
• Exact base: 5cb023e1ee524c1eafd10ef13e50a88e7b15100d
• Local focused: 27 passed, 13 skipped (cuDF cases skip without GPU); ruff passed.
• Exact-source DGX focused (26.02-gfql, TEST_CUDF=1): 40 passed, zero skips.
• Exact-source DGX broad (new file + test_lowering.py): 1719 passed, 5 skipped, with six failures.
• The same six broad failures reproduce at exact base 5cb023e1. They involve cuDF row-pipeline/list/entity handling and one cuGraph edge-direction assertion; none exercises null-equality filtering.

Gates

Exact-head CI 40077120699, CodeQL 40077120695, and RTD are terminal green at 0e5c11262c83f75348404b9358bfb95f36676c53.

Merge remains gated on planner review.