- from defaults to the calling session's own host:name. The shared HTTP daemon finds it from the forwarded x-slab-prompt-session-id header, the env (stdio children only), or the process that owns the loopback socket matched against the session markers; unknown callers still fall back to <host>:prox. - an ambiguous handle is now an error listing candidates, not a success-shaped reply, so nothing looks sent when it was not. - stamp carries a reply: prox_send handle=... hint and indents every body line under a bar, so a body cannot forge a second inbox header. - the send result echoes what the receiver will see, and says when a file drop to an idle session will be read. - http-front passes remotePort in the per-request context. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>