enqueueMessage method

Future<void> enqueueMessage(String id, SubagentMessage message, { bool capText = true, })

Queues message for id (Phase 3b agent_message / parent steering). Throws StateError for an unknown id or a full pending queue; caps the body at maxReplyChars unless capText is false — the warm-wake resume path passes the parent's steering verbatim (the mailbox cap would silently truncate it AND shrink it under the over-window guard, letting an oversized request slip through to the provider). Aborted children refuse new messages.

With a messaging fabric the message is DELIVERED to the recipient's inbox (cross-process visible); otherwise it sits in the in-process pending queue. main (selfId) is a valid recipient — that is how children message the parent.

Implementation

Future<void> enqueueMessage(
  String id,
  SubagentMessage message, {
  bool capText = true,
}) async {
  final handle = _handles[id];
  await _guardRecipient(id, handle);
  final capped = capText ? _capMessage(message) : message;
  final gateway = a2aGateway;
  if (gateway != null && id.contains('@')) {
    await _deliverViaA2a(gateway, id, capped);
    return;
  }
  if (messaging != null) {
    await _deliverViaFabric(id, handle, capped);
    return;
  }
  if (handle!.pendingMessages.length >= maxPendingMessages) {
    throw StateError(
      'subagent "$id" pending queue is full ($maxPendingMessages) — '
      'the child must consume its messages first',
    );
  }
  handle.pendingMessages.add(capped);
  _touchWithMessage(handle, capped);
}