# swarm-controller

The **swarm-level** daemon. Where `hive-c0re` owns the agents on one host, this
owns what is true _across_ hives — so a swarm runs one of them and most hives
leave it off.

Opt-in per host via `services.hyperhive.deploy.swarm-controller.enable`, which is
deliberately **not** derived from
`services.hyperhive.deploy.hive-controller.enable`: turning it on is a statement
about swarm topology, not about whether this host runs a hive.

## What it does

The swarm's control plane. The swarm UI and `swarmctl` are its clients.

- **Hive directory** — serves `swarm.hives` (`GET /api/hives`) and what each
  hive last published about itself (`GET /api/hives/status`).
- **Agent roster and wanted state** — every agent the swarm knows
  (`GET /api/agents`, `/api/agents/status`), and the state it declares for
  each one on its hive (`up`/`offline`/`paused`/`destroyed`,
  `PUT /api/hives/{hive}/agents/{agent}/state`).
- **Job graph** — a `hive-jobq` scheduler, served at `GET /api/jobq/graph`.
  Every provisioning step below runs as a node in it.
- **Agent creation** — `POST /api/agents` queues the SSO identity (through
  `swarm-authelia-bridge`), forge user, config repo, store identity, forge
  token and matrix account, declares the agent `paused`, then sends its hive
  a deploy message.
- **Agent credentials** — at start and every five minutes it re-checks every
  agent's forge token and matrix account, and renews store certificates and
  queue secrets as they age.
- **Linked external accounts** — an operator-supplied matrix or forge
  account for one agent, stored in the swarm secret store
  (`PUT /api/hives/{hive}/agents/{agent}/matrix-accounts/{account}`,
  `.../forge-accounts/{label}`); distinct from the agent's own swarm-minted
  accounts above.
- **Config PR status** — each agent's open config-repo PR, cached from forge
  webhooks (`GET /api/config-prs`, `/api/agents/{name}/config-pr`).
- **Swarm-wide forge objects and webhooks** →
  [`docs/swarm/README.md`](../docs/swarm/README.md#swarm-wide-forge-objects).
- **Relays** — each agent's terminal and turn-state header as SSE, agent
  icons, the cross-repo issue report, and the UI's quick links.

It reads its configuration once at startup, from the environment the nix module
sets. The one file it persists is `webhook-secret` in its state directory.
The job graph lives in memory; hive status and wanted state live in the swarm
queue, so both survive a restart.

## Why a unix socket, not a port

The hive-gateway's nginx is the only intended client and reaches the socket
through a bind-mount. A listener that is never bound to an address cannot be
reached from off-host by mistake.

The socket path is `services.hyperhive.deploy.swarm-controller.socketPath`, default
`/run/swarm-controller/controller.sock`, exported to the process as
`SWARM_CONTROLLER_SOCKET`.

## ⚠️ The socket's directory is its access control

The socket is `0666`. It has to be: nginx runs as a different user and
`connect(2)` needs write. This matches how `hive-c0re` publishes the per-agent
sockets, and rests on the same argument — _"the bind source dir is per-agent on
host so blast radius is unchanged."_

What keeps that safe is that the directory holds **one** socket. So:

> **Never point `socketPath` at a directory that carries anything else.**
> `/run/hyperhive` above all — it holds `host.sock`, the host **admin** socket.
> Pointing nginx at that directory to reach this socket would put the admin
> socket within its reach too.

nginx is a host service, so nothing narrows what it can reach except the
directory itself — that is the whole of the access control. A unit test pins
the default path so a tidying edit fails instead of reviewing cleanly.

`RuntimeDirectoryPreserve=yes` and the daemon's stale-socket unlink on start are
a **pair**: preserving the directory without the unlink means `bind` fails with
`EADDRINUSE` after a restart.

## Packaging

Built by the workspace derivation and extracted as its own package
(`nix build .#swarm-controller`). Deliberately **not** in `nix/packages`'
`daemonBins` — that list is the core stack and drives the bundle
`services.hyperhive.c0re.package` points at, so folding this in would put a
swarm-scoped service into every hive's closure.