Limitations

Firestore is the provider with the most query-engine gaps among the Vali-Flow NoSql adapters. Unsupported nodes throw immediately at translation time rather than silently producing an incorrect filter.

Limitation	Detail
Contains / StartsWith / EndsWith	Throw NotSupportedException. Firestore has no LIKE, regex, or substring query operator. Filter client-side after fetching, or integrate a dedicated search index (Algolia, Elasticsearch, Typesense) for text search.
.Not(inner)	Throws NotSupportedException unconditionally. The SDK exposes no Filter.Not(filter) composition. Use .NotEqualTo(x => x.Field, v) directly instead of .Not(f => f.EqualTo(x => x.Field, v)) — that reaches Filter.NotEqualTo via EqualNode.IsNegated.
Negated .In(...)	Not reachable yet. The SDK exposes Filter.NotInArray(field, values), but the current IR's InNode has no IsNegated flag (unlike EqualNode), so no ValiFlow<T> method reaches it yet.
Nested AND/OR	Not a gap, just a shape note: chaining three or more conditions produces nested Filter.And(a, Filter.And(b, c)) rather than a single flat call. Firestore accepts nested composite filters, so this is semantically equivalent — only relevant if you inspect the generated Filter for debugging.

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