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hyperhive/swarm-builder/README.md
atlas b68b74d687 swarm-builder: build each agent config PR head and post a commit status
A new `swarm-builder` service, in its own container on the host that sets
`deploy.builder.enable` (defaulted on by `allSwarmServices` where the host
has the builder's store leaf, like the review classifier).

When an `agent-configs/<agent>` PR is opened, reopened or synchronized,
swarm-controller queues a `build_agent` jobq node. The node sets a
`swarm-builder` commit status to pending on the PR head, sends
`{agent, rev, pr}` to the builder over NATS request-reply
(`$SWARM.builder.build`), and writes success (store path), failure (last
line nix printed) or error (no builder / no reply) on the head. The node
fails when the build does, so the Jobs page matches the PR.

The builder builds nix/builder/check-flake's `check` with every input
overridden: hyperhive and nixpkgs to the host's own
`c0re.hyperhiveFlake`/`c0re.nixpkgsFlake` (what a hive there renders into
its meta flake), and the agent to the PR head on the forge. Evaluation is
pure and runs in the container; builds go to the host nix daemon as an
untrusted client. The private config repo is fetched with the token of a
new read-only `builder` forge account (in the `hives` team), which the
controller mints into `swarm/services/builder/forge/token`; git gets it
from a credential helper reading the child's environment, so it is in no
argument or URL.

Credentials: a `builder` store leaf minted by glue-bao-tls on the store
host, a `swarm-builder` reader policy (forge token + its own OIDC client
secret), an authelia machine client, and a `--builder-client` grant in the
queue's auth-callout responder. The controller gains a grant on the token
path and the secret publisher a deny on it.

This is the agent-config build check atlas scoped on #5081 (slice 3):
nothing is pushed to a cache, nothing is written to KV, and a red status
gates no deploy. The check composes agent-base + the config without the
values a hive adds (CA, docs, claude-code path, ports, input follows), so
it can disagree with a hive's own build.
2026-10-14 03:30:46 +02:00

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Markdown

# swarm-builder
The swarm builder's build service, in the `swarm-builder` container on the
host that sets `deploy.builder.enable`. The design is
[`docs/swarm/builder.md`](../docs/swarm/builder.md).
swarm-controller sends one request per config PR head: an agent, a commit and
the PR. This service builds that agent config on the agent base this host was
deployed with, through the host's nix daemon, and answers with the system
closure's store path or the tail of what `nix` printed. The controller turns
the answer into a `swarm-builder` commit status on the PR's head.
## What a build is
- `nix build` of `nix/builder/check-flake`'s `check` output, with its three
inputs overridden: `hyperhive` and `nixpkgs` to this host's own sources, and
`agent` to `git+https://<forge>/agent-configs/<agent>?ref=refs/pull/<pr>/head&rev=<rev>`.
- The evaluation runs here, pure; the builds run in the host daemon's sandbox
as an untrusted client, so a config can neither set daemon options nor read
this service's environment.
- Nothing is pushed and nothing is recorded: the closure stays in the host's
store until it is collected.
## Credentials
The container holds one credential: its own store certificate, which nspawn
hands in at start without a copy on disk. With it the service reads its
queue client secret at start and its read-only forge token at every build.
`git` gets the token through a credential helper reading the child's
environment, never in a URL or an argument. Its store role reads exactly
those two paths.