hyperhive/docs/integrations/matrix.md

# hive-matrix

Private Matrix homeserver (matrix-tuwunel — the conduwuit
successor) wrapped in a nixos-container, plus optional fluffychat-web
client at `chat.<swarm-domain>/` (the `gatewayHost` vhost). Configured via
`services.hyperhive.swarm.matrix.*`; vhost routing lives in
[`gateway.md`](../networking/gateway.md).

## Container shape

Same shape as [`gateway.md::hive-forge container shape`](../networking/gateway.md):

- Container name `hive-matrix` (not `h-*`) so c0re's lifecycle
  scanner ignores it; operator manages via the standard
  `nixos-container` CLI.
- Keeps hive-matrix from fighting any `services.matrix-*` the
  operator already runs on the host — separate systemd namespace,
  separate state dir.
- Container shares the host network namespace
  (`privateNetwork = false`) for state + systemd-unit isolation. Agents
  reach the homeserver at `chat.<swarm-domain>` via the gateway (agents
  run in private netns and can't access host loopback directly).
- Persistent state at
  `/var/lib/nixos-containers/hive-matrix/var/lib/matrix-tuwunel/`
  survives container restart / host reboot. To wipe, destroy the
  container.

## Identity vs API listener: `serverName` vs `gatewayHost`

Two distinct hostnames:

- **`serverName`** — matrix-spec `server_name`, embedded
  *irrevocably* in every `@user:<server_name>` and `!room:<server_name>`
  identifier minted on this homeserver. You can't change it later
  without abandoning every account and chat history. Defaults to the
  bare `services.hyperhive.swarm.domain`; clients autodiscover the
  actual API endpoint via the `.well-known/matrix/{client,server}`
  routes the gateway serves at that domain.
- **`gatewayHost`** — the API listener hostname, where the gateway's
  matrix vhost proxies `/_matrix/*` to tuwunel. Defaults to
  `chat.<services.hyperhive.swarm.domain>`. Set to `null` to skip the
  gateway vhost (tuwunel stays direct on `httpPort`).

Both default under the **swarm** domain, because a swarm runs one
homeserver: tying its identity to a single hive's domain would make
relocating the container between hives look like a different
homeserver.

⚠️ **they're still not interchangeable, and the difference is the
cost of changing one.** `gatewayHost` is a routing detail clients
rediscover through `.well-known`, so it's safe to move on a running
deployment. The matrix id format bakes `serverName` into every user and
room id, so adopting a new one does **not** rename the existing users and rooms —
it strands them, because their ids still name a homeserver that no
longer answers.

### Upgrading a homeserver that already has ids

`serverName`'s default has changed across releases. A homeserver that
has already minted ids under an older default must **pin the value it
actually minted them under**, not adopt the new default — see above
for why adopting a new one strands existing users and rooms:

```nix
services.hyperhive.swarm.matrix = {
  # whichever this deployment already uses
  serverName = config.services.hyperhive.domain;
  gatewayHost = "matrix.${config.services.hyperhive.domain}";
};
```

A rebuild on a host that already has a homeserver prints a
`hive-matrix: WARNING — … serverName is unset` line when this is missing,
naming the value it's about to default to. That warning is why this
section exists; it never fails the rebuild, so it's on you to act on it
before the homeserver mints the ids.

## Default-closed firewall

`openFirewall` defaults to `false` (secure-by-default): the host
reaches the homeserver on loopback, and agent containers reach it
at `chat.<swarm-domain>` via the gateway — so the firewall hole only
matters for access from *outside* the host. Flip to `true` when
announcing the homeserver to other hives or when an external matrix
client needs to reach the client-server API directly.

Federation port 8448 is intentionally not opened here — tuwunel
serves the federation API on the same `httpPort` as client-server
by default. Reaching it on 8448 needs either an explicit tuwunel
bind to that port OR a reverse-proxy + `.well-known/matrix/server`
delegation (the latter lives in `gateway.md::Discovery flow`).

## Provisioning flow (appservice)

<!-- vale write-good.Passive = NO -->
Registration is closed. The hive's own **appservice** creates accounts:
hive-c0re holds the appservice token, agents never see
it, and an agent only ever receives its own `access_token`.
<!-- vale write-good.Passive = YES -->

The appservice has no URL (`url: null` in its registration), so the
homeserver never calls out to it and there is no service to run. What the
registration buys is an identity the homeserver recognises — which is why
no secret has to be equal on both sides of the wire, and why account
creation doesn't depend on registration being open to anyone who learns
a token.

1. **System activation** mints a 32-byte random hex appservice token (64
   chars) at `/var/lib/hyperhive/matrix-appservice-token` and its
   spec-required `hs_token` sibling, mode `0600 root:root`, then renders
   the registration to
   `/var/lib/hyperhive/matrix-appservice/hyperhive.yaml` (also `0600`).
   hive-c0re mints the tokens only when missing; the registration is
   re-rendered every time, because the token file can be overwritten in
   place by the swarm secret store and a registration naming a stale
   token authenticates nobody. Runs at activation time, before any
   container start, because the directory is bind-mounted and
   nixos-container refuses to start when a bind source is missing.
2. **Read-only bind-mount** maps that directory into the tuwunel
   container at the same path.
3. **systemd `LoadCredential=`** inside the container copies the
   registration into
   `/run/credentials/tuwunel.service/hyperhive-appservice.yaml`, owned by
   tuwunel's dynamic user with mode `0400`, at service start. The host
   file stays `root:root 0600` — no `chown :tuwunel` / `chmod 0640` /
   GID-pin gymnastics required. Keeps `DynamicUser = true` +
   `PrivateUsers = true` intact.
4. tuwunel's `appservice_dir` points at the credentials directory, not at
   the bind-mount path. It reads only `.yaml`/`.yml` entries from there,
   so the sibling credentials are invisible to it. The `.yaml` suffix on
   the credential id is what makes this work.
5. **hive-c0re** reads the appservice token and creates each account with
   one `POST /register` typed `m.login.application_service`, persisting
   the returned `access_token` to `<agent-state>/matrix-token`. It never
   mints the token itself: the value has to be the one the rendered
   registration names, and only the nix side writes that.
6. **An account that exists but has lost its token file** is re-tokened
   by an appservice `POST /login` — no password and no admin rights
   involved. A stored-password login and an admin-room password reset
   remain behind that, for accounts created before the appservice existed
   or named outside its namespace.
7. **hive-c0re restarts `hive-matrix-daemon`** for the agent
   immediately after writing the token so the daemon picks up the
   new credential without waiting for a full container restart. If
   the restart fails (for example daemon not yet running on first boot)
   hive-c0re logs the error as a warning and the `.path`-trigger sibling
   (`hive-matrix-daemon.path` watching for `matrix-token` appearance)
   brings the daemon up on the same boot cycle anyway.

### The appservice's sender account, and why it isn't an admin

`@hive:<server_name>` is the appservice's own `sender_localpart`, which
the homeserver creates itself when it loads the registration — on a
zero-user database, inside startup, before the HTTP listener accepts
anything. It's an **ordinary account**: nothing promotes it, and the
homeserver runs no `admin_execute` for it.

Its access token is the **sender token**, and it's the credential
hive-c0re presents for every homeserver call it makes on the hive's
behalf. `swarm-matrix-ctl` mints it inside the `hive-matrix`
container and publishes it to `swarm/services/matrix/sender-token`; the
hive reads it from there. The name says what it authenticates as — an
account the appservice registration brings into being — rather than any
privilege level, because it carries none.

It needs no promotion for what the hive does with it. Creating the hive
Space and the chat room, writing their hierarchy and join rules, and
inviting agents into them are all ordinary client calls that ride on
being the rooms' own creator at power level 100 — there is no homeserver
admin in any of it, and no Synapse admin API to reach for either, since
tuwunel has none.

Two operations need an admin **sender**: `hivectl matrix promote-user`
and `hivectl matrix reset-password`. Both are `!admin …` messages into
`#admins:<server_name>`, and tuwunel only treats a message as a command
when its sender is already an admin. They're swarm-level operations,
rehomed to the swarm tier rather than granted here; from the hive,
`@hive:` has no admin sender to make that call with, so both get the
admin room's refusal rather than an over-privileged credential that
every other call site would also carry. The one hive-side path that
depends on them is the automatic password recovery for an agent that
has lost its stored password — the admin-sender limitation doesn't
touch the ordinary appservice re-login above.

<details><summary>Upgrading a hive that used the registration token</summary>

Nothing to do, and nothing to time. The activation script mints the
appservice token and renders the registration before the homeserver
restarts, so the first boot after the switch already has both halves.

<!-- vale write-good.Passive = NO -->
- **Existing accounts keep working.** An access token lives on the
  device that minted it; removing the registration token touches no
  device, no account and no session. `login_with_password` stays on, so
  the password fallback is still there too.
- **The per-agent sweep honours existing token files.** It skips any
  agent that already has a `matrix-token`, so it re-registers no account
  and displaces no session.
- **The sender account may already be an admin** on such a hive (it won the
  first-user grant when the hive was new). Nothing here demotes it; the
  homeserver no longer promotes it, so a hive built fresh has an
  ordinary account and an older one keeps whatever standing it acquired.
- **`/var/lib/hyperhive/matrix-register-token` stays on disk**, read by
  nothing. Delete it or leave it; neither does any harm.
- **`registrationTokenFile` is a removed option.** A config that still
  sets it fails to evaluate with a message naming the appservice — a hive
  that never set it (the default) is unaffected.
- **A swarm store holding the old `matrix/registration-token` path** is
  no longer read at all. The value that matters now lives at
  `matrix/appservice-token`, and `swarm-secret-publish` on the authelia
  host mints and `put`s it there — the hive uses its locally minted
  token only until the first successful read. See
  [`../swarm/secrets.md`](../swarm/secrets.md) for how that mint stays
  idempotent across runs.
<!-- vale write-good.Passive = YES -->

</details>

Initial rollout settings:

- `allow_federation = true` at the protocol level so swarms can be
  wired up later by extending `trustedServers` without a homeserver
  restart. `trusted_servers = []` keeps it effectively closed
  until you list peers.
- `allow_registration = false`. tuwunel checks this flag only for
  requests that arrive **without** an appservice token, so hive-c0re
  provisions exactly as before and tuwunel refuses everyone else. It's not a
  hardening afterthought: with no registration token configured,
  `allow_registration = true` makes tuwunel refuse to start unless
  `yes_i_am_very_very_sure_…_open_registration_…` is also set.
- `allow_encryption` — server-side E2EE switch, sourced from
  `services.hyperhive.swarm.matrix.allowEncryption` (**default `false`**, opt-in).
  Off by default because on the hive-internal homeserver the operator
  already controls the transport; turn it on for encrypted rooms on
  external / federated homeservers or to keep contents opaque to the
  homeserver admin. **The agent matrix client always supports decryption
  regardless of this flag** — it uses the `e2e-encryption` feature of
  `matrix-sdk` so it can read encrypted rooms it's invited to even when
  this homeserver doesn't permit room encryption. matrix-sdk stores
  crypto keys in the per-agent sqlite store under the state dir; they persist across
  restarts (lost on `--purge`). `read_room` decrypts via
  `room.messages()` — UTD events surface as `event_type =
  "m.room.encrypted"` with `body = "[unable to decrypt]"`.
  Cross-signing and automatic key backup aren't enabled for the first
  pass: static bearer-token bot accounts can't bootstrap cross-signing
  without MSC3967.

## Hive Matrix Space

On first boot, after hive-c0re provisions all agent accounts, it
creates a private **Matrix Space** named `"hive"` using the `@hive:`
account (`@hive:<server_name>`) and invites every provisioned agent
into it. This gives the operator a single Space in FluffyChat or any
Matrix client that groups all agent-to-agent + operator rooms in one
place.

<!-- vale write-good.Passive = NO -->
The sweep also provisions a default **`hive-chat` room** as an
`m.space.child` of the Space. Joining a Space doesn't autojoin
child rooms — the explicit room entry ensures the operator and every
agent can find a common chat room without manual setup. Room join is
restricted (any Space member including the operator can join; agents
are explicitly invited). Room version pinned to 10 for the restricted
join floor.
<!-- vale write-good.Passive = YES -->

**State**: hive-c0re persists both room IDs to `/var/lib/hyperhive/matrix/`
(mode `0600`, owned by the hive-c0re service user):
- `space-room-id` — the Space itself
- `chat-room-id` — the `hive-chat` room

These paths are **outside** every agent state dir and **aren't** deleted by
`nixos-container destroy --purge` — both survive full agent purges, and
hive-c0re reuses them on re-provision.

**Idempotent**: if the files exist and are non-empty, hive-c0re considers the Space and
room already created. Delete the files to force
re-creation (for example after a homeserver wipe).

## Configuration tuning

```nix
services.hyperhive.swarm.matrix = {
  trustedServers  = [ "matrix.org" "example.com" ];   # default: []
  maxRequestSize  = 20000000;                          # default: 20 MB
};
```

**`trustedServers`** (default `[]`) — list of peer homeserver names
whose signing keys tuwunel fetches and trusts. tuwunel enables
federation at the protocol level from first boot (`allow_federation =
true`) but trusts no remote homeserver until you list it here. For a closed
single-hive deployment the default empty list is correct — add peer
hive domains here when connecting hives into a swarm (see
[`docs/swarm/`](../swarm/README.md)).

**`maxRequestSize`** (default `20_000_000` bytes = 20 MB) — maximum
size of a single matrix client request body. Matches the matrix-spec
recommendation for media uploads and the upstream tuwunel default.
Raise for deployments that need large file transfers; lower for
resource-constrained hosts where a 20 MB request is unexpectedly large.

## Assertion rationale

`config.assertions` in this module fail eval early rather than ship
surprising behaviour:

- **`services.hyperhive.swarm.matrix.gatewayHost != ""`** — same footgun as `forge.domain`:
  empty string renders `.<hive>`-shaped garbage in both nginx
  `server_name` (treated as wildcard catch-all, surprising) and
  `/etc/hosts` (invalid entry). `null` is the right opt-out shape;
  a config assertion rejects empty string explicitly.
SSO is unconditional, so the three below are requirements of running a
homeserver at all rather than of a setting:

- **Set `sso.clientSecretFile`** — fails at eval, not at boot:
  tuwunel reads its identity providers from the config file, so a
  half-configured one can stop the homeserver from starting outright
  rather than merely hiding a login button. On a host that also runs
  the swarm's authelia it's wired up for you.
- **Set `swarm.authelia.url`** — without a provider URL there
  is nothing to discover against.
- **Set `gatewayHost != null`** — the SSO callback URL is
  format-locked to `<homeserver>/_matrix/client/unstable/login/sso/callback/<client_id>`,
  and the identity provider needs a public name to redirect the
  browser to.

`server_name`'s own bogus-value guard lives in `hive-network.nix`
(`services.hyperhive.domain != null`), not here — see
[`docs/networking/network.md`](../networking/network.md).

## fluffychat-web build fixes

`pkgs.fluffychat-web` ships from `flutter341.buildFlutterApplication`,
which has two upstream gaps for fluffychat's web target:

- The dart web-worker entry point (`web/native_executor.dart`) isn't
  compiled — `buildFlutterApplication` only runs `flutter build web`
  on the main entry.
- `native_imaging`'s C source isn't built — emscripten isn't a
  flutter-builder native build input.

Both fixed in `nix/host-modules/hive-matrix.nix` via two derivations:

- **`fluffychat-web-imaging`** builds `Imaging.{js,wasm}` from the
  `native_imaging` C source via `pkgs.emscripten`. Source comes
  from `pkgs.fluffychat-web.passthru.pubspecLock.dependencySources.native_imaging`
  — already in the build closure of the flutter app, so no parallel
  hash pin and version autosyncs with nixpkgs bumps. Build closure
  is ~3.6 GiB (emscripten LLVM); runtime closure is just the two
  output files. `dontConfigure = true` because cmake runs inside
  `js/Makefile` via `emcmake cmake`, not at the package root. The
  build script needs `HOME` + `EM_CACHE` writable for emscripten's
  on-demand sysroot build (libc, libc++ → wasm).
- **`fluffychat-web-fixed`** is `pkgs.fluffychat-web` plus a
  `postInstall` patch that (a) compiles `web/native_executor.dart`
  via `dart compile js` (dart from the flutter341 closure, no
  incremental cost) and (b) installs `fluffychat-web-imaging`'s
  outputs into `$out`.

Two subtle details worth knowing before touching either derivation:

- **`make -C js`** instead of `cd js; make` — keeps the build-phase
  pwd at the source root so `installPhase` doesn't have to know
  about the cd. Robust against future reorders / `dontBuild`.
- **`web/native_executor.dart`** as a build-CWD-relative path,
  *not* `$src/web/...` — `dart`'s `package_config.json` walk-up
  needs to hit `buildFlutterApplication`'s pub-get output
  (`.dart_tool/` in the build CWD). Walking up from a read-only
  `$src/` store path finds no `.dart_tool/` and errors with
  "Couldn't resolve the package 'matrix'."

Drop both derivations when nixpkgs's flutter builder grows worker
+ emcc support upstream.

Mount point is `chat.<swarm-domain>/` (the `gatewayHost` vhost);
upstream `--base-href "/"` is correct at sub-domain root, no override.