What problem does it solve? When multiple AI agent sessions run on the same machine, coordinating them normally requires the human to relay information between windows. This Skill lets one agent session send a message directly to another session, to every session in a project, or to every session on the machine, with delivery handled automatically by each session's hook. ## Core Features & Use Cases - Three send shapes: 1:1 sends via --session-id, project broadcasts via --project-id, and machine broadcasts when neither target is given; if both are given, the session target wins. - Mandatory sender identity: session and project ids are derived from harness environment variables, pid ancestry, and the .ai-badger/project-id walk, or passed explicitly; unresolvable identity refuses the send with a non-zero exit. - Target validation: a --project-id target is checked against projects resolvable on this machine before anything is written, so undeliverable rows are never stored. - Use Case: An agent finishes investigating a bug and runs the send script with another session's id and the message "found it, see src/bus.py"; the receiving session's delivery hook injects the message into its context on its next turn. ## Quick Start Ask the agent to send a message to another session by running the send_message.py script with --content and the target --session-id.