SERVER-130817 changed the default of internalQueryMaxMemoryUsageBytesPerOperation from effectively unbounded (LLONG_MAX) to max(1GB, 20% of available memory). This is an operation-wide cap enforced across all memory-tracked stages/expressions of a single operation.

Streams inherits this cap because the stream-processor ExpressionContext is built with an OperationContext. However, streams already has its own memory management: per-operator → per-processor ChunkedMemoryAggregator → node-level ConcurrentMemoryAggregator, enforced by KillAllMemoryUsageMonitor (tracked + RSS-based), with checkpoint recovery.

So we do not want to enforce an operation-wide memory limit on stream processing, because streams governs total/accumulated memory through its own aggregator and node-level monitor. We do want, though, to keep a bound on individual expression evaluation. To do this, streams should use the default standalone per-expression tracker (capped by internalQueryMaxSingleExpressionMemoryUsageBytes) without propagating usage to the operation-wide OperationMemoryUsageTracker.