argus's review on #5177: the git credential helper answered every `get`,
so a config PR's own flake inputs could have git send the builder's forge
token to any host. The helper is now configured under
`credential.<forge-url>.helper` and itself answers only an https request
whose host is the forge's; a test runs it as git does and checks that
other hosts, http and non-get operations get nothing.
Builds are bounded: every `build_agent` node needs the one `builder` jobq
resource, so one runs at a time and the rest wait pending, and a newer
head cancels its PR's pending build (a running one finishes and writes on
its own commit). The builder also holds a one-permit semaphore around each
build.
`builder` and `review-classifier`, the forge logins swarm-controller owns,
join nix/reserved-names.nix, with a test tying the list to both constants.
The builder is now opt-in like the CI runner: `allSwarmServices` no longer
turns it on, since it runs unreviewed config PRs through the host's nix
daemon. mara had not answered atlas's question on the PR.
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.
