With no since the pages are the whole list. The last page carries an ETag, the position the read ended at: send it as since to read only what changed since then, and also as If-None-Match, so that a read finding nothing changed is a 304 with no body. Send each next_cursor as since to continue; a null next_cursor means the last page. A since the API cannot continue (from another sign-in) is a 400: read from the start. Where the firm's practice system shows each person their own matters (capabilities.matter_visibility is member), the page holds the matters THE CALLER is shown there and no others, besides the matters the firm made itself, and only while the caller's own sign-in there is live (member.system_link.status is connected on GET /v1/me): a caller who has not signed in, or whose sign-in is no longer accepted, is served none of that system's matters until they sign in again, and so is everybody at a firm that disconnected it. Each such row's updated_at is the later of the matter's own and the instant the caller's access to it last changed, so a matter that became visible arrives on an incremental pull. One the system withdrew from the caller arrives once, with active false, on a pull whose since is from before the withdrawal, and never again whatever changes on it; a pull with no since holds none. Every other firm's answer is unchanged.

Operator mount: an operator acting for the firm named in the path, as its oldest active admin, else its oldest active billing member; X-Six-Minute-Acting-As names them. 404 for no such firm, 409 urn:six-minute:problem:no-acting-member for one with neither.