Function handle_pty_shell_create 

pub(super) async fn handle_pty_shell_create(
    __arg0: State<AppState>,
    __arg1: Json<PtyShellCreateRequest>,
) -> impl IntoResponse

POST /api/v1/ptyshell/create — attach to (creating if needed) “this pane’s one shell.”

Reuses the same sub-block a human’s composer-drawer shell already uses or will use (META_KEY_SHELL_SUBBLOCK_ID), in either direction: if the human already opened the drawer, the agent joins that exact PTY — same scrollback, same live output. If nothing exists yet, this creates it (the same view: "term", controller: "shell" headless-sub-block shape createsubblock’s WS handler builds for AgentShellSubblock.tsx) and persists the pointer, so a drawer opened afterward attaches to what the agent already started instead of spawning a second, independent shell. Either way, resync_controller runs before returning — unlike the WS path (which waits for a frontend to mount a term view and call ControllerResyncCommand), the PTY is live the moment this call returns; a UI viewer for it is optional, not a prerequisite.