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🤖 ## Summary Every Buzz channel has a **type**, such as an ordinary chat channel (`stream`), a forum, a DM or a workflow. A client app can only show the types it was built to understand. This PR makes the relay (the Buzz server) follow one rule everywhere: **a client sees a channel only if it knows that channel's type.** #8406 applied this rule to membership notices. This PR applies it to the reads that list channels without naming one: the channel list, "channels I belong to", the sidebar's unread list and artifact lists. Before, these reads left out one type by name: system channels. Now they return only the four types that every client has always known: `stream`, `forum`, `dm` and `workflow`. Today the result is the same for every user, because `system` is the only other type. ### Backward compatibility: old clients stay safe - A client that was released before a new channel type exists will never receive channels of that type in its lists. It cannot show such a channel correctly, so it does not get one. - Requests that old clients send today return exactly what they returned before. Nothing changes for them now or when a type is added later. ### Forward compatibility: new types can be added safely - Before, the rule was a deny list: "everything except `system`". Each new type would appear in every deployed client by default, unless someone remembered to update five separate checks in the relay. A missed check would show the new type to clients that cannot handle it. - Now the rule is an allow list that is frozen: the four original types. A new type is hidden by default, with no relay change needed. Clients that understand it can request it on purpose, the same way current clients request system channels today. Each new type gets its own opt-in, so adding a type cannot break clients that are already in use. ## Details - One frozen list, `buzz_core::channel::LEGACY_CHANNEL_TYPES`. Membership notices (#8406) now use the same constant, so channel reads and notices cannot drift apart. The duplicate `LEGACY_NOTICE_CHANNEL_TYPES` is removed. - One SQL helper, `legacy_channel_type_sql`, builds `channel_type IN ('stream', 'forum', 'dm', 'workflow')` from that list. It replaces the five `<> 'system'` checks: - `get_accessible_channel_ids` (both halves): the implicit channel scope of any filter without `#h`, for example kind 39000 channel metadata, REQ, COUNT and search; - `get_accessible_channels`: the channel list; - the personal-read sidebar roster; - artifact queries. - A filter that names a channel (`#h`, or `#d` on kinds 39000–39003) reads it under the ordinary rules, whatever its type: the reader is a member, or the channel is open. The uncached named-channel lookup, `get_readable_named_only_channels`, now returns every readable non-legacy channel with its type, not only system channels. Before, a non-member could not read an open later-type channel, and `#d` read nothing. Workflow run reads and thread windows use the same lookup. - The relay keeps each named channel in the scope of the filter that names it only. This also holds when it re-checks membership for a named channel that the cache lacks. - The opt-in to system channels (`#t:["system"]` or `#P` on kinds 39000–39003) adds readable **system** channels only. It never adds a channel of another type, even one that a sibling filter in the same request names. The relay scope type `NamedOnlyChannels` keeps the type with each channel, so the opt-in can tell them apart. - NIP-CL and NOSTR.md state the rule. ### Related issue Follows #8406 (the same rule for membership notices). ### Testing New Postgres tests use a scratch database with a `future_type` value added to `channel_type`, as a later migration would add one: - `reads_that_name_no_channel_leave_out_a_type_added_later`: the channel scope, the channel list and the sidebar roster leave out the later type and keep the legacy types. - `artifacts_of_a_later_channel_type_are_read_only_by_name`: artifact current and history queries and counts without `#h` leave out the later type. With `#h` naming the channel, they return it. - `channels_of_a_later_type_are_read_only_by_name`: production read paths (WS REQ, WS COUNT, HTTP `/query` and `/count`). A member reads a private later-type channel and anyone reads an open one, by `#h` and by `#d`; an outsider cannot read the private one; a read that names no channel returns neither. In one request, a filter that names the channel plus a `#P` or `#t:["system", <label>]` sibling: the sibling does not get it. - `a_named_channel_of_a_later_type_stays_in_its_named_filter`: the membership re-check for a channel joined mid-request, with an unnamed sibling and a `#P` sibling. Only the naming filter gets the channel. Each test fails when its predicate goes back to `<> 'system'`, when the named lookup loads only `system`, or when the opt-in adds every named-only channel. The #8406 notice tests and the system channel Postgres tests pass on this branch. --------- Signed-off-by: Logan Johnson <loganj@squareup.com> Co-authored-by: Larry <627498bd4bd1f281a16431e3c6cce3b5c25b6692798c78672298aefbf2f8f8b5@buzz.block.builderlab.xyz>