Function sources_at 

pub fn sources_at(
    overrides: &Overrides,
    blocks: &Blocks,
    now: &Zoned,
) -> Sources

What the reasons’ sources say at now, from the pauses’ overrides and Health’s blocks: every reader of the switch builds them so (the window, the listener, the calls’ table, sioul remind --watch, sioul watch, the MCP), a pause ending Reachable in all of them (review of part 3, F7).