internal_call_transformer

Metadata key marking a model call as internal to middleware.

Kept separate from lc_source so filtering doesn't affect its existing semantics.

Return metadata that marks a model call as internal to middleware.

Keep internal model calls out of run.messages and the raw event log.

Used by middleware that makes internal model calls and runs before built-in transformers.

For tagged events, streamed message-start events are marked as tool-role and whole-AIMessage payloads are cleared so MessagesTransformer ignores them. The mutated events are then dropped from the raw log.

Only events within this transformer's scope are modified.