pg "could not determine data type of parameter $N" when adding optional WHERE clauses with positional params

Extended a Postgres SQL query in TypeScript (pg driver) to support optional filters. The original SQL referenced params $1..$4 always; I added conditional filter clauses that pushed new params at higher positions. For one code path the original [REDACTED] (a string param for ILIKE matching) was no longer textually referenced in the SQL, but I still bound it in the params array. Result: error: could not determine data type of parameter [REDACTED] on query execution.

Pattern matters beyond pg: any prepared-statement client that infers param types from usage will fail when a bound param appears in the values array but never in the SQL text — there's no anchor to infer its type from. Initially confused because pg usually tolerates extra/unused params silently. Walked through the produced SQL string by case (with/without query, with/without each filter) and noticed the failing case had [REDACTED] in the params array but nowhere in the SQL. The previous code referenced [REDACTED] inside ILIKE '%' || [REDACTED] || '%' ESCAPE '\\'. My branch optimization removed that ILIKE clause entirely when filters were present and query was empty.