The auth callout grants an agent that presents its own queue credential
one more subject, `$KV.agent-icons.<agent>`: its own key in the
agent-icons bucket and no other. The hive's shared agent client is
granted none of the bucket, since every agent on a hive presents it.
hive-agent writes `/etc/hyperhive/icon.svg`, the file its `GET /icon`
serves, to that key once per start, as a JetStream publish straight to
the subject (what `kv::Store::put` sends, minus the bucket lookup), so
the one subject is the whole grant. No icon deletes the key. A failed
write, including one that arrives before the bucket exists, is retried
with backoff until acked. An agent connected with the hive's shared
client publishes nothing.
swarm-controller creates the bucket as soon as its queue connection is
up, instead of on the first icon read, so an agent's write does not
wait for someone to look.
Measured against a local nats-server with a user allowed publish on
`$KV.agent-icons.atlas` only: the write to its own key is stored and
readable, a write to `$KV.agent-icons.argus` is refused (the ack times
out), the DEL marker makes the key read as absent, and a write before
the bucket exists fails with "no responders".
`scripts/check-issue-refs.sh` blocks a `#N`-shaped reference in source.
The quoted ruling reads identically without it, so the tag goes rather
than a lint suppression.
An agent is not fixed to a hive, so its icon cannot be resolved as
hive -> agent. This adds the swarm-level half: an `agent-icons` KV
bucket keyed by the agent name alone — no hive token, so an agent that
moves hives keeps its icon and one that is stopped still has one — and
`GET /api/agents/<name>/icon` on swarm-controller serving it
same-origin, like every other `/api/*` route swarm-ui calls.
404 is the "this agent has no icon" answer, the same contract the
per-agent harness's own `GET /icon` has for an unconfigured agent.
Until the agent-side publisher lands, that is every agent's answer:
the publisher runs inside the container and an agent's NATS grants are
hive-scoped, which cannot authorise a write to a single-token agent
key. The read side needs no grant change — the controller already
holds `$KV.*.>` and `$JS.API.DIRECT.GET.*.>`.
The response carries `Content-Security-Policy: sandbox` and `nosniff`:
the body is an operator-authored SVG served from this daemon's own
origin, and an SVG can carry script.
Hive-side icon serving is untouched.
Refs #4502
