{"answer":"Review complete. I read the new sweep module, the metrics rendering, the admin route, the store's write/index layout, the cache serve path, and the config, and checked the diff's claims against them. Findings:\n\n🔴 `bug` services/proxy/src/metrics.rs:94: `values()` reads `sweep_bytes_reclaimed` and `sweep_blobs_removed` in the opposite order to `COUNTERS` (lines 51-57), so the `/metrics` endpoint renders the blob count under `cairn_proxy_sweep_bytes_reclaimed_total` and the byte count under `cairn_proxy_sweep_blobs_removed_total`. docs/operations.md directs operators to alert on `cairn_proxy_sweep_bytes_reclaimed_total`, so the alert would fire on blobs instead of bytes — the exact mis-rendering the comment at line 30-32 claims the side-by-side layout prevents.\n\n🟠 `bug` services/proxy/src/routes/admin.rs:76: the admin route calls `app.sweeper.sweep(dry_run)` directly, bypassing the `running` mutex that only `Sweeper::run` (sweep.rs:83) takes. An operator-triggered sweep runs concurrently with the background sweep — exactly the \"two of them over one directory\" interference the module doc (sweep.rs:10-12) promises the type prevents. Both compute `held`/`remaining` from totals the other is concurrently shrinking, so together they can delete roughly twice the excess, dropping the store far below the ceiling either aimed at.\n\n🟠 `bug` services/proxy/src/sweep.rs:140: `forget(&index, &gone)` runs unconditionally, but in dry-run mode `gone` is still populated (line 137) while the blob removals were skipped — so `?dry_run=true`, which docs/architecture.md and the route doc promise removes \"without removing anything\", actually deletes the index entries for every blob a sweep would reclaim. Those coordinates then resolve as misses and refetch until relinked, so a \"dry\" probe churns the cache it was meant to size.\n\n🟠 `bug` services/proxy/src/sweep.rs:232: `clear_partials` unlinks every file in `incoming`, including temp files of fetches still in flight — `BlobWriter` (store.rs:171-180) and `BlobStore::link`'s index temp (store.rs:147-152) both live there while active. The unlink doesn't kill the write (the fd stays valid), but `commit`'s rename (store.rs:259) then fails with ENOENT and the client's fully-downloaded artifact returns a storage 500. The comment at lines 220-223 (\"A file in `incoming` is a fetch that is not coming back\") is wrong for any fetch mid-download when the sweep fires.\n\n🟡 `bug` services/proxy/src/sweep.rs:84: `run()` executes the fully synchronous `self.sweep(false)` — a recursive `std::fs` walk that the module doc itself sizes at sixty-five thousand directories — directly on a tokio worker thread. Every cache request stalls behind it for the duration of the walk, and the `running` mutex is held across it so an admin sweep queues too. `spawn_blocking` is the fix the doc argues for and then doesn't apply.\n\n🟡 `bug` services/proxy/src/sweep.rs:164: `fs::metadata` follows symlinks, so a linked-in blob is counted at its target's size, contradicting the comment at lines 160-163 which claims `symlink_metadata` behavior; and since `meta.is_dir()` recurses, a symlink loop under `blobs/sha256` makes `collect` recurse until the stack overflows, aborting the process.\n\n🟡 `bug` services/proxy/src/sweep.rs:119: a blob committed at cache.rs:151 is not indexed until `link` at cache.rs:163, with a registry round-trip between; a sweep in that window classifies it as unreferenced and deletes it, so the miss path's reopen at cache.rs:90-97 fails and the client gets the \"blob committed by this request is already missing\" 500 instead of the artifact it just downloaded.\n\n🔵 `bug` services/proxy/src/sweep.rs:126: when `fs::remove_file` fails, the blob stays on disk but `remaining`, `bytes`, `removed` and `gone` are all still updated, so the metrics and the route response overcount what was reclaimed and `forget` (line 140) deletes index entries naming a blob that still exists.\n\n🔵 `bug` services/proxy/src/main.rs:108: `tokio::time::interval`'s first tick completes immediately, not \"one interval away\" as the doc comment at lines 101-102 claims — a proxy that restarts sweeps a store it has not yet touched, the protection the comment describes does not exist. 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