diff --git a/src/main/kotlin/kestrel/engine/ParameterSubstitution.kt b/src/main/kotlin/kestrel/engine/ParameterSubstitution.kt
new file mode 100644
index 0000000..e4b7b4f
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+++ b/src/main/kotlin/kestrel/engine/ParameterSubstitution.kt
@@ -0,0 +1,158 @@
+package kestrel.engine
+
+import kestrel.KestrelException
+import kestrel.sql.ast.Assignment
+import kestrel.sql.ast.BetweenExpression
+import kestrel.sql.ast.BinaryExpression
+import kestrel.sql.ast.CallExpression
+import kestrel.sql.ast.CaseExpression
+import kestrel.sql.ast.CastExpression
+import kestrel.sql.ast.CollateExpression
+import kestrel.sql.ast.ColumnExpression
+import kestrel.sql.ast.ConflictAction
+import kestrel.sql.ast.ConflictDoNothing
+import kestrel.sql.ast.ConflictDoUpdate
+import kestrel.sql.ast.CubeSpec
+import kestrel.sql.ast.CurrentValueExpression
+import kestrel.sql.ast.DeleteStatement
+import kestrel.sql.ast.ExistsExpression
+import kestrel.sql.ast.Expression
+import kestrel.sql.ast.ExpressionProjection
+import kestrel.sql.ast.FrameBound
+import kestrel.sql.ast.FromItem
+import kestrel.sql.ast.FunctionExpression
+import kestrel.sql.ast.GroupingSetsSpec
+import kestrel.sql.ast.GroupingSpec
+import kestrel.sql.ast.InExpression
+import kestrel.sql.ast.InSubqueryExpression
+import kestrel.sql.ast.InsertStatement
+import kestrel.sql.ast.IsNullExpression
+import kestrel.sql.ast.LikeExpression
+import kestrel.sql.ast.LiteralExpression
+import kestrel.sql.ast.MergeActionExpression
+import kestrel.sql.ast.MergeMatchedDelete
+import kestrel.sql.ast.MergeMatchedUpdate
+import kestrel.sql.ast.MergeNotMatchedInsert
+import kestrel.sql.ast.MergeStatement
+import kestrel.sql.ast.MergeWhenClause
+import kestrel.sql.ast.NextValueExpression
+import kestrel.sql.ast.OnConflictClause
+import kestrel.sql.ast.OrderBy
+import kestrel.sql.ast.ParameterExpression
+import kestrel.sql.ast.PreparableStatement
+import kestrel.sql.ast.Projection
+import kestrel.sql.ast.QueryStatement
+import kestrel.sql.ast.RollupSpec
+import kestrel.sql.ast.ScalarSubqueryExpression
+import kestrel.sql.ast.SelectStatement
+import kestrel.sql.ast.SetOperationStatement
+import kestrel.sql.ast.StarProjection
+import kestrel.sql.ast.SubquerySource
+import kestrel.sql.ast.TableSource
+import kestrel.sql.ast.UnaryExpression
+import kestrel.sql.ast.UpdateStatement
+import kestrel.sql.ast.WindowExpression
+import kestrel.sql.ast.WithQuery
+import kestrel.storage.Value
+
+/**
+ * Resolves `$1`, `$2`, ... [ParameterExpression] placeholders inside a [PreparableStatement] -
+ * the only place they are ever actually turned into real values. Walks exactly the shape
+ * [kestrel.catalog.RelationRename]/[kestrel.catalog.DependencyAnalysis] already walk for a view's
+ * defining query (FROM/JOIN targets, derived tables, CTE bodies, set-operation branches, every
+ * subquery nested in WHERE/HAVING/projection/GROUP BY/ORDER BY/window frames), plus the parts only
+ * a top-level DML statement has that a view's body never does: INSERT's VALUES rows and ON CONFLICT
+ * clause, UPDATE's SET assignments, and MERGE's USING source/ON condition/WHEN clauses - since a
+ * prepared statement can be any [PreparableStatement] kind, not just a SELECT.
+ * [kestrel.engine.Executor.resolveExecute] is the only caller.
+ */
+internal object ParameterSubstitution {
+
+    /** Highest 1-based parameter index anywhere in [statement] - 0 if it has none. EXECUTE must supply exactly this many arguments. */
+    fun parameterCount(statement: PreparableStatement): Int = when (statement) {
+        is QueryStatement -> maxIndexInQuery(statement)
+        is InsertStatement -> maxOf(
+            statement.rows.maxOfOrNull { row -> row.maxOfOrNull { it?.let(::maxIndexInExpression) ?: 0 } ?: 0 } ?: 0,
+            statement.onConflict?.let(::maxIndexInOnConflict) ?: 0,
+            statement.returning?.let(::maxIndexInProjection) ?: 0
+        )
+        is UpdateStatement -> maxOf(
+            statement.assignments.maxOfOrNull { it.value?.let(::maxIndexInExpression) ?: 0 } ?: 0,
+            statement.where?.let(::maxIndexInExpression) ?: 0,
+            statement.returning?.let(::maxIndexInProjection) ?: 0
+        )
+        is DeleteStatement -> maxOf(
+            statement.where?.let(::maxIndexInExpression) ?: 0,
+            statement.returning?.let(::maxIndexInProjection) ?: 0
+        )
+        is MergeStatement -> maxOf(
+            maxIndexInFromItem(statement.source),
+            maxIndexInExpression(statement.onCondition),
+            statement.whenClauses.maxOfOrNull(::maxIndexInWhenClause) ?: 0,
+            statement.returning?.let(::maxIndexInProjection) ?: 0
+        )
+    }
+
+    fun substitute(statement: PreparableStatement, boundValues: List<Value>): PreparableStatement = when (statement) {
+        is QueryStatement -> substituteQuery(statement, boundValues)
+        is InsertStatement -> statement.copy(
+            rows = statement.rows.map { row -> row.map { it?.let { expression -> substituteExpression(expression, boundValues) } } },
+            onConflict = statement.onConflict?.let { substituteOnConflict(it, boundValues) },
+            returning = statement.returning?.let { substituteProjection(it, boundValues) }
+        )
+        is UpdateStatement -> statement.copy(
+            assignments = substituteAssignments(statement.assignments, boundValues),
+            where = statement.where?.let { substituteExpression(it, boundValues) },
+            returning = statement.returning?.let { substituteProjection(it, boundValues) }
+        )
+        is DeleteStatement -> statement.copy(
+            where = statement.where?.let { substituteExpression(it, boundValues) },
+            returning = statement.returning?.let { substituteProjection(it, boundValues) }
+        )
+        is MergeStatement -> statement.copy(
+            source = substituteFromItem(statement.source, boundValues),
+            onCondition = substituteExpression(statement.onCondition, boundValues),
+            whenClauses = statement.whenClauses.map { substituteWhenClause(it, boundValues) },
+            returning = statement.returning?.let { substituteProjection(it, boundValues) }
+        )
+    }
+
+    private fun substituteAssignments(assignments: List<Assignment>, boundValues: List<Value>): List<Assignment> =
+        assignments.map { it.copy(value = it.value?.let { value -> substituteExpression(value, boundValues) }) }
+
+    private fun substituteOnConflict(clause: OnConflictClause, boundValues: List<Value>): OnConflictClause =
+        clause.copy(action = substituteConflictAction(clause.action, boundValues))
+
+    private fun substituteConflictAction(action: ConflictAction, boundValues: List<Value>): ConflictAction = when (action) {
+        ConflictDoNothing -> action
+        is ConflictDoUpdate -> action.copy(
+            assignments = substituteAssignments(action.assignments, boundValues),
+            where = action.where?.let { substituteExpression(it, boundValues) }
+        )
+    }
+
+    private fun substituteWhenClause(clause: MergeWhenClause, boundValues: List<Value>): MergeWhenClause = when (clause) {
+        is MergeMatchedUpdate -> clause.copy(
+            condition = clause.condition?.let { substituteExpression(it, boundValues) },
+            assignments = substituteAssignments(clause.assignments, boundValues)
+        )
+        is MergeMatchedDelete -> clause.copy(condition = clause.condition?.let { substituteExpression(it, boundValues) })
+        is MergeNotMatchedInsert -> clause.copy(
+            condition = clause.condition?.let { substituteExpression(it, boundValues) },
+            values = clause.values.map { it?.let { expression -> substituteExpression(expression, boundValues) } }
+        )
+    }
+
+    private fun substituteQuery(query: QueryStatement, boundValues: List<Value>): QueryStatement = when (query) {
+        is SelectStatement -> substituteSelect(query, boundValues)
+        is SetOperationStatement -> query.copy(
+            left = substituteQuery(query.left, boundValues),
+            right = substituteQuery(query.right, boundValues),
+            orderBy = query.orderBy?.let { substituteOrderBy(it, boundValues) }
+        )
+        is WithQuery -> query.copy(
+            ctes = query.ctes.map { it.copy(query = substituteQuery(it.query, boundValues)) },
+            body = substituteQuery(query.body, boundValues)
+        )
+    }
+