The mirror would happily hold a four-shard model that nothing could serve. A
catalog entry names one source, the agent fetched one URL, and so a version of
several files had no way to be described — which is every safetensors model,
and every GGUF too large to ship whole.
A source ending in a slash names a version rather than a file. The agent fetches
every file in it into one directory and hands the engine the directory: vLLM
reads the shards and the config out of the folder, and llama.cpp is given the
first part and finds the rest beside it.
The trailing slash is the whole signal. A flag beside the source would be a
second place for the two to disagree, and a URL already distinguishes a
directory from a file everywhere else.
The mirror answers a version with a manifest instead of a file listing. A plain
file server gives HTML there, and something that has to know what a version
consists of would be left parsing it. It is on the byte listener, not the
management API: fetching weights is the one thing every node does, and making
it depend on the administrative port would undo the split that keeps that port
closeable.
Built from the directory rather than a file written beside it. A manifest on
disk is a second record of what is there, and the two disagree the first time
somebody copies a file in by hand — which the mirror explicitly allows.
The whole set or nothing. A directory with three of four shards loads as a
broken model rather than failing to load, so a completion marker is written
last and an interrupted fetch starts the missing files again rather than being
found and served. Files already there at the right size are not fetched twice.
Progress is reported under the version's address, not each file's: the shards
waiting on it asked for the version, and progress under a file's own URL
reaches nobody.
A filename from the manifest is refused if it contains a separator. The mirror
is a place an operator copies files into by hand, so what it reports is not
automatically safe to join onto a path.
An HTML listing where a manifest was expected says so. "invalid character '<'"
sends somebody looking at the wrong thing.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The mirror holds the weights, so the mirror does the downloading. A control
plane that had to pull the bytes itself and push them here would carry every
model twice over the network, through the one machine least able to spare the
bandwidth.
Two listeners, and the split is the point. Weights stay on plain HTTP where
every node can reach them: that path is eight nodes pulling forty gigabytes,
and putting a client certificate in front of it would mean re-certifying every
agent's fetcher in order to change how models are administered. Management gets
its own port, which can be given the fleet's CA — the same tlsconf the agent
stream uses, so this is a configuration rather than a new idea.
A fetch answers 202, not 200. The bytes are not here yet, and a caller that
read it as "done" would point a catalog at a file still arriving, which every
node would then copy. Progress is asked for rather than waited on, because no
client between here and the operator will hold a connection open for an hour.
A failed fetch is remembered with its reason. Forgetting it would leave the
control plane waiting on a model that is never coming, with nothing to say why.
Status falls back to reading the disk, so a restart does not report a model
that is plainly there as unknown.
Removal takes the whole version: a model split across files is useless with one
of them missing, and half a version on disk looks present and will not load. It
refuses while a download is running, because the fetch would carry on writing
and the file would reappear, looking like the delete had silently failed.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The mirror was a directory and a discipline written down in a README. This
makes the three operations that matter into commands, on the mirror host,
where `llmgw keys` already sets the precedent of operator tooling that works
on files rather than through the API.
The gateway still never writes to the mirror. That property was chosen
deliberately — a mirror writable by the thing reading from it is a way to
replace a model with one every node then fetches without complaint — and a
person running a command does not take it away. `serve` states it rather than
inheriting it, so a handler added later cannot quietly make the mirror
writable.
`add` downloads to a temporary name and renames, for the reason the agent's
fetcher does: a mirror is copied to every node, so a partial file here is a
partial file everywhere. It verifies the length the server promised, reports a
checksum — the mirror is the one place a corrupt file reaches every node
rather than being caught once — and refuses to replace an existing version,
which is the whole point of the layout.
`unused` refuses to answer when it cannot read the catalog. An empty catalog
and an unreachable one produce the same list, everything, and the obvious next
step after that list is deletion. It compares by path rather than by spelling,
because a base typed with a different scheme or a trailing slash would
otherwise report a file in use as unused.
`remove` checks the catalog first and says to retire the entry before deleting
the file, because a node that has to refetch a deleted file cannot, and that
failure arrives later, on the node, looking like something else.
Verified end to end: Range requests answer 206, which is what makes an
interrupted fetch on a node resume; writes answer 405; a traversal attempt
answers 404.
Note: internal/agent/supervisor's TestSidecarRunsBeforeEngine fails under full
suite load on main as well as here — it asserts that one shell's echo lands
before another's, which the supervisor does not promise. Everything else
passes. Left alone rather than fixed in a commit about mirrors.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
