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When a CWI index is used with a $ne: null predicate on a non-wildcard indexed field alongside a wildcard-field predicate, the query planner now inserts an unnecessary FETCH stage. This is a regression introduced by SERVER-95374. A regular non-sparse compound index, a non-wildcard sparse index, and a non-wildcard sparse compound index all produce covered plans for $ne: null. CWI matched this behaviour before SERVER-95374. Example db.demo.drop(); db.demo.createIndex({ "w.$**": 1, unit: 1 }); db.demo.insertMany([ { w: { x: "A" }, unit: 1 }, { w: { x: "A" }, unit: 2 }, { w: { x: "B" }, unit: 3 }, { w: { x: "B" }, unit: 4 }, ]); Before SERVER-95374, this query was covered (totalDocsExamined = 0, PROJECTION_COVERED): db.demo.aggregate([ { $match: { "w.x": "A", unit: { $ne: null } } }, { $project: { _id: 0, unit: 1 } }, ]); After SERVER-95374 it produces PROJECTION_SIMPLE with a FETCH stage and totalDocsExamined = 4. Fix traverseAndPropagateANDRelatedPredicates strips index assignments from all $not nodes unconditionally, rather than applying the same $ne: null exception that nodeIsSupportedBySparseIndex already carves out for sparse indexes. Smarter stripping logic - analogous to that can restore the pre-regression behaviour.

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