sandbox:read-only (macOS Seatbelt)
-- reasoning --
Let me review the diff. Key files: sweep.rs, admin.rs, routes/mod.rs, metrics.rs, config.rs, main.rs.

Let me read the actual files under pr/ for context, especially store.rs (BlobStore, IndexEntry, rename behavior), and check things like: clear_partials deleting files currently being written by an in-flight fetch (BlobWriter writing to incoming — sweep removes partials regardless of age; an in-flight fetch's temp file would be deleted, causing the rename to fail or the blob to be lost). That's a real bug: clear_partials removes all files in incoming with no age check, while a concurrent fetch may be actively writing there. The comment claims "A file in incoming is a fetch that is not coming back" — but that's false under concurrency: a fetch in progress writes to incoming. Deletion of the open file on Unix is fine for the writer (fd stays valid), but the rename into blobs would then fail (source gone) — actually rename of a deleted path fails ENOENT, so the fetch fails. Actually on macOS/Linux, unlink of the path while open: writer holds the fd, write succeeds, then rename(path) fails because path no longer exists. So concurrent fetches get broken by every sweep. That's a real bug: no min_age applied to partials. Severity high.

Also `sweep` route runs `app.sweeper.sweep(dry_run)` — a synchronous blocking filesystem walk on the tokio runtime thread (async handler calls sync function). The module doc says the walk is synchronous deliberately, but calling it inside an async handler blocks the executor thread. Also the on-demand route doesn't wait for mutex — wait, `sweep` in Sweeper is pub and does NOT acquire the `running` mutex. The comment says "One sweep at a time... Held for the whole of a sweep, so this module's one-at-a-time promise is something the type keeps" — but `run()` takes the lock and then calls `self.sweep(false)`, while the admin route calls `app.sweeper.sweep(dry_run)` directly, bypassing the mutex. So a background sweep and an on-demand sweep can run concurrently, and two on-demand sweeps can run concurrently — violating the one-at-a-time promise stated in the module doc. That's a bug: admin.rs sweep should call `.run()`-like locking path. High severity: two concurrent sweeps double-count bytes and each compute totals from a moving store; also dry-run concurrent with real sweep. Actually more importantly: the lock is only taken in `run()`; `sweep()` is public and unguarded. This is the fault: the promise documented at lines about Mutex isn't kept for the route. Defect at sweep.rs:~110 (`pub fn sweep`) / admin.rs line calling it.

Also blocking: `sweep()` is sync and called from async handler `admin::sweep` directly → blocks tokio worker for the whole walk of a large store (65k dirs). Should use spawn_blocking. Medium/high.

Also in sweep(): `let Some(hex) = candidate.path.file_name()...else { continue; }` — this `continue` happens before the removal accounting? No, wait: the for loop: for each candidate, get hex from file_name; if it fails, `continue` — skipping the candidate entirely, meaning its size stays in `remaining`... fine. But note: `held` sums all candidates including non-file things. Files whose name isn't valid UTF-8 get skipped but their bytes counted in held; if store only contains those, sweep removes nothing but reports held > max. Minor.

Bigger: `remaining` only decreases and condition `remaining >= self.max_bytes` — uses `>=` vs `>`; fine.

Bug: candidates that are referenced but file_name not valid... skip.

Bug: `collect` on the blobs dir includes the index dir? No, separate.

Bug: `referenced` uses `collect` which collects files with `meta.is_dir()` recursion — fine.

Bug in `forget`: it removes index entries for `gone` digests, but `gone` includes blobs removed only because over-ceiling too — correct, those are gone from store. But wait: `forget` is called even in dry_run! In dry_run, nothing is removed, but `forget` still removes index entry files — `forget(&index, &gone)` runs regardless of dry_run. That's a real bug: a dry run deletes index entries while claiming to remove nothing. The docs say "?dry_run=true reports what one would reclaim without removing anything." But forget removes the index files for all candidate digests that would have been removed — including referenced-but-over-ceiling ones and unreferenced ones. So dry run destroys cache index state. High severity. Line: `forget(&index, &gone);` — no dry_run guard.

Wait — but in dry_run, `gone` is populated for all candidates matching remove criteria, including ones that wouldn't be removed... In dry run remove logic still computed; `gone.push(hex)` for all that would be removed. Then forget deletes index entries. Definitely a bug.

Another: `clear_partials` in dry run returns count of entries without removing — fine (report partials count).

Another: in sweep(), for a candidate whose name can't be turned into hex (e.g., non-UTF8 filename), `continue` skips before `remove` check — but also skips before checking unreferenced. Fine, minor.

Bug: in the removal loop, when `fs::remove_file` fails (in non-dry-run), the code still counts it as removed and subtracts bytes (`removed += 1; bytes += candidate.size;`). So metrics/report overstate reclamation and `remaining` drops below actual held → may remove fewer/more blobs than needed. Actually more importantly: the metric `record_sweep(removed, bytes)` counts blobs that failed to be removed, and bytes that weren't reclaimed. The comment says "Usually a blob that has already gone" — if it's already gone, then bytes weren't held in the first place... but `held` summed them from metadata before. Either way the counter overstates. Medium.

Bug: `held`/`remaining` computed from fs::metadata which follows symlinks — comment says links counted at link size, but `fs::metadata` follows symlinks (symlink_metadata doesn't). So a symlinked blob is counted at the size of the target, contradicting the comment. fs::metadata follows the link; fs::symlink_metadata doesn't. So the stated intent (count link size, not target) is wrong — comment/behavior mismatch. Also `clear_partials`' remove on a symlink removes the link... minor. Also collect recurses into dirs via metadata... Symlink to directory: meta.is_dir() true → recursion into target path — fine-ish. Low/medium: comment claims one thing, code does another; consequence: over-counting bytes on linked stores → premature eviction. I'd report low.

Config: `DEFAULT_CACHE_MIN_AGE: Duration = Duration::from_hours(1);` — std Duration has no `from_hours` or `from_mins` constructors! std::time::Duration has from_secs, from_millis, from_secs_f64... `from_hours`/`from_mins` don't exist in std. Unless this project has its own Duration... config.rs uses `Duration` — need to check import. If it's std::time::Duration, this won't compile. Let me check pr file. Could be a custom Duration type? Let me check. Also `sweep_interval.is_zero()` exists on std Duration. `Duration::from_mins` doesn't exist. This is likely a compile error — critical. Must verify by reading config.rs.

Metrics: `values()` returns order: ..., sweep_bytes_reclaimed, sweep_blobs_removed — matches COUNTERS order (blobs_removed first in const array, then bytes_reclaimed). Wait: COUNTERS order: hits, misses, upstream_failures, policy_refusals, sweep_blobs_removed_total, sweep_bytes_reclaimed_total. values(): ..., sweep_bytes_reclaimed.load, sweep_blobs_removed.load. So values puts bytes before blobs, but COUNTERS lists blobs_removed before bytes_reclaimed. Mismatch → labels swapped: blobs-removed name renders bytes value and vice versa. That's the bug the comment at COUNTERS says side-by-side stops ("Keeping the two side by side is what stops a fifth counter from being rendered under a fourth one's name"). Real bug — high/medium. Verify indices: COUNTERS[4] = blobs_removed, COUNTERS[5] = bytes_reclaimed. values[4] = sweep_bytes_reclaimed, values[5] = sweep_blobs_removed. Yes, swapped. Doc in operations.md says watch `cairn_proxy_sweep_bytes_reclaimed_total` — would show blob counts. Report as bug.

Also main.rs: `tracing::info!(?reclaimed, ...)` fine.

routes/mod.rs: sweep route placed in untimed router — with comment justifying. Fine.

admin.rs: `use axum::Json` — routes/mod.rs also imports Json; fine. `RequestId` extractor — is it imported in admin.rs? Diff shows admin.rs uses `RequestId(request_id): RequestId` but imports shown: `use axum::extract::{Path, Query, State};` — RequestId is from crate::routes presumably; is there a `use crate::routes::RequestId;`? The diff doesn't show adding it. Let me check the file — the diff context only shows changed hunks; maybe existing import exists (purge route uses RequestId?). The purge handler earlier — let's read admin.rs to check. handle() takes raw &str; the purge route handler probably destructures RequestId. Need to read the file.

Also `reclaim` runs sync sweep blocking the async executor (mentioned). And also: the on-demand sweep route bypasses mutex (already noted).

Also the sweep route: while a background sweep holds the mutex, the route's sweep doesn't wait — concurrent. Yes.

Another: `spawn_sweeps` — `app.cfg.sweep_interval`; if sweep_interval validation only pushes a problem (fails startup? problems -> Err presumably). Fine.

Also: sweep removes blobs referenced by index when over ceiling — then forget deletes index entries. But if remove_file failed (blob still there) forget still deletes index entries → index points at existing blob, next request resolves... index removed → treated as miss → refetch and overwrite existing blob? BlobStore::put would rewrite. OK.

Also partials: `clear_partials` removes ALL files in incoming including those of in-flight fetches (no age filter) — top bug.

Also: `collect` in `referenced` — index dir may have nested structure (ecosystem/name dirs). fine.

Check `Reclaimed` includes `held` etc.

Let me read the files to confirm: config.rs Duration imports, admin.rs imports, store.rs (BlobWriter, incoming usage, IndexEntry), metrics.rs final, routes/mod.rs.

Also check `parse_duration` supports what; not needed.

One more: config validation checks sweep_interval zero but not cache_min_age zero — min_age zero is arguably valid (no grace). Fine.

Also `.env.example` fine.

Let me read pr files.
I'll read the changed files under `pr/` for context before judging.
└ 2461 tok ·  82.3 tok/s · 12K ctx · 6352ms ttft · 29.9s wall
↳ read_file: read pr/services/proxy/src/sweep.rs
└ read_file: read complete
↳ read_file: read pr/services/proxy/src/config.rs
└ read_file: read complete
↳ read_file: read pr/services/proxy/src/routes/admin.rs
└ read_file: read complete
↳ read_file: read pr/services/proxy/src/metrics.rs
└ read_file: read complete
auto-compress is on at 85% but the context window of "z-ai/glm-5.3-flash" on openrouter is unknown, so this run will not compress - set AFI_SOURCE_OPENROUTER_CONTEXT_WINDOW (or pass --context-window) to enable it
-- reasoning --
Key findings so far:

1. **metrics.rs values() order mismatch**: COUNTERS declares blobs_removed then bytes_reclaimed, but values() returns bytes then blobs (lines 94-95 vs 51-57). So the two new counters are swapped in the rendered output — `cairn_proxy_sweep_blobs_removed_total` reports bytes and vice versa. This is exactly the bug the comment "Keeping the two side by side..." was guarding against. Real bug. 🔴/🟠.

2. **sweep.rs clearing partials is unsafe with in-flight fetches**: `clear_partials` removes every file in `incoming`, but BlobWriter is actively writing there for in-flight fetches. The sweep has no coordination with the store's writer. Is there any in-flight protection? Need to check store.rs / cache.rs — does the writer create temp files in incoming and rename? A sweep removing a temp file mid-write would cause a fetch to fail. The comment claims "A file in incoming is a fetch that is not coming back" — but an in-flight fetch is coming back. Also min_age doesn't apply to partials. That's a real defect: a sweep can delete a partial for a fetch currently in progress. Also the index read: `referenced` reads index entries via collect() which uses fs::metadata — but also note: a fetch that just completed writes blob then index entry; between blob write and index entry write, a sweep considers the blob unreferenced and deletes it (age-gated? no — unreferenced bypasses min_age deliberately). Race: cache miss fetch completes → blob renamed into place → index entry written after. If sweep runs between, it deletes blob and then... actually index contains entry? Need to read store.rs to see write order.

Also forget(): index entries for blobs removed by ceiling eviction get deleted — fine. But note `forget` deletes index entries for any removed blob, including those removed because unreferenced — but unreferenced blobs have no index entries (or stale ones). Fine.

3. **routes/mod.rs**: removed the comment about cache route timeout; moved cache route into `untimed` which also includes the sweep route. The sweep route... also note the sweep route is under `untimed` — reasonable. But wait: bounded router merges untimed; the TimeoutLayer was applied to `bounded` before merge? Order: `bounded` has TimeoutLayer applied... Actually in axum, layer applied to `bounded` applies to routes in bounded only; merge(untimed) — the layer was applied before merge so untimed routes don't get it. OK, matches original.

4. **main.rs spawn_sweeps**: `app.sweeper.run()` is a synchronous blocking walk run inside the async task (sweep is a sync fn called inside async without spawn_blocking). The module doc acknowledges the walk is synchronous deliberately. But this blocks the tokio runtime thread for the duration of the sweep — with a multi-thread runtime, that stalls one worker thread, and since the sweep route also runs this on a request handler thread, a large store could block an executor thread for minutes. The module doc justifies sync vs tokio::fs, but doesn't spawn_blocking. That's a real performance defect: blocking the async runtime. 🟠 performance. Similarly the admin sweep route calls `app.sweeper.sweep(dry_run)` synchronously inside an async handler, blocking the runtime and also outside the timeout layer.

5. **Deadlock/order in background sweep**: not an issue.

6. **main.rs**: `ticks.tick()` first tick fires immediately? Tokio's interval first tick is immediate, not "one interval away" — the doc comment says "The first tick is one interval away". Tokio `interval()` fires the first tick immediately. So the first sweep runs right at startup, contradicting the comment. Minor: not a bug per se, but the comment claims a behavior opposite to what happens; effect: a just-started proxy sweeps a fresh cache immediately — harmless but the comment is wrong. Low severity (🔵 maintainability/comment). Actually the first tick of `tokio::time::interval` completes immediately — yes, documented behavior. So the comment is factually wrong. 🔵.

7. **config.rs**: `cache_min_age` zero check missing — CAIRN_CACHE_MIN_AGE=0 means no grace; is that a problem? Not necessarily. But there's no validation for min_age. Not a defect per se.

Wait — check `Duration::from_hours` / `from_mins` — these are from a `duration-str`? No — std Duration has no from_hours. Presumably there's an extension trait elsewhere in the codebase. Existing code already used them in tests (from_mins in parse_duration test), so fine.

8. **routes/admin.rs `reclaim` is sync and not through the sweeper's mutex**: `app.sweeper.sweep(dry_run)` bypasses the `running` mutex! `Sweeper::run()` locks the mutex, but the route calls `sweep()` directly, so an on-demand sweep does NOT wait for a background sweep. Two concurrent sweeps over one directory — exactly the failure the module doc promises the type prevents ("One sweep at a time... something the type keeps rather than something every caller remembers"). The route violates it. 🟠/🔴 bug. Line: admin.rs:76 calling sweep directly, or sweep.rs:90 exposing sweep publicly. This is a real concurrency bug: two concurrent sweeps double-count bytes and delete more than intended, and dry-run racing with a real sweep gives wrong answers.

Also note the docs say `POST /v1/admin/cache/sweep` "runs one now" — consistent.

9. **dry-run semantics**: in dry_run, `forget` is not called but `gone` includes candidates that would be removed; fine since not removing. But wait — in dry_run, remove decision made on unreferenced blobs also — fine.

10. **sweep removes blobs not in index, but index reads race**: a blob just fetched: cache.rs writes blob and index entry. If sweep's `referenced()` runs between blob placement and index entry write, the blob is unreferenced → deleted regardless of age. Then the index entry is written pointing at a missing blob → next request miss & refetch. Actually that self-heals. But worse: the sweep deletes a blob that a concurrent request is about to serve... it re-verifies. Minor race, self-healing. Maybe not report.

Actually wait — check store.rs to see order: does index entry get written before or after blob? Need to read store.rs and cache.rs.

11. **clear_partials race with active writers** — need to check store.rs's BlobWriter: does it write into incoming and rename? A sweep deleting an in-progress temp file makes the ongoing fetch fail (write to unlinked file still succeeds on POSIX actually — unlink during write: the fd remains valid, writes go to unlinked inode, then rename fails with ENOENT). So the fetch fails; the client gets an error mid-download for a 200MiB download. Also it breaks the "partial blob" promise. Severity: medium. Also there's no min_age applied to partials, so a fetch of a large artifact (>15min? no—sweep interval) — the sweep could run during any in-flight fetch. Let me check store.rs.

12. **metrics doc line 31**: "what stops a fifth counter..." — stale comment, trivial.

13. **sweep.rs `held` counts but `remaining >= self.max_bytes`**: if held is already under max, no eviction — fine. Note strictness: removes until remaining < max. Fine.

14. **`collect` for index uses fs::metadata (follows symlinks)**: for index dir files fine.

15. **hex extraction from path file_name**: blob files are named by hex? Check store layout — blobs/sha256/<hex>? If blobs are nested blobs/sha256/ab/cdef..., file_name is still the hex. But if blob names include extension, index.contains_key(hex) fails → treated as unreferenced → deleted. Need store.rs.

16. **admin sweep route lacks timeout** — deliberate.

17. **`reclaim` metrics double count on error?** No.

Let me read store.rs and cache.rs and main.rs.
Now the store and cache paths, to check the sweep's assumptions against how blobs and index entries are actuallywritten.
└ 1822 tok ·  99.9 tok/s · 23K ctx · 1229ms ttft · 18.2s wall
↳ read_file: read pr/services/proxy/src/store.rs
└ read_file: read complete
↳ read_file: read pr/services/proxy/src/main.rs
└ read_file: read complete
↳ read_file: read pr/services/proxy/src/routes/cache.rs
└ read_file: read complete
-- reasoning --
Let me analyze carefully.

Key candidate defects:

1. **`clear_partials` deletes in-flight downloads.** `incoming/` holds temp files for *active* fetches, named `<pid>-<sequence>`. The sweep's `clear_partials` removes every file in `incoming/` with no age check — a fetch that is currently streaming a 200 MiB artifact for minutes is deleted mid-download; the writer keeps writing to the unlinked file, commit renames an unlinked inode → the blob disappears; then `open_blob` fails... actually commit renames temp → target; rename of unlinked file recreates the path? On POSIX, renaming a deleted-but-open file: the temp path no longer exists after unlink; `fs::rename(&temp, &target)` — the temp path no longer exists on disk, so rename fails with NotFound. Actually wait — unlink removes the directory entry; the temp path is gone; rename fails with ENOENT. So `commit` fails, request errors. Also the sweep can never distinguish "abandoned" from "in flight" — there's no min_age applied to partials. That's a real bug: `clear_partials` at sweep.rs:224-240 removes files in `incoming/` without any age threshold, while an active fetch can be writing there for the whole fetch_timeout (30s default, but download up to 256MiB may take longer; route untimed, fetch timeout 30s). With sweep interval 15m, an active download is a window of seconds-to-minutes; the 15m interval makes collision rare but the on-demand sweep route makes it reachable any minute. Severity: medium/high. Also there is no grace period — a fetch that started 1 second before the sweep gets killed. I'd call this 🟠 high.

2. **Sweep holds the async mutex across a fully synchronous, potentially long blocking walk** — `run()` acquires `tokio::sync::Mutex` then calls `self.sweep(false)`, a synchronous function doing recursive `fs::read_dir` over 65k dirs. This blocks the tokio worker thread (docs admit it's synchronous, "one pass of standard-library calls costs less"). This is a deliberate documented tradeoff. Also, it runs on the async runtime, stalling... The comment in module docs acknowledges this deliberately. But the admin route `sweep` handler calls `app.sweeper.sweep(dry_run)` directly (not `run()`), **bypassing the mutex**! Look: `reclaim()` in admin.rs:76 calls `app.sweeper.sweep(dry_run)` — not `app.sweeper.run()`. So an on-demand sweep can run concurrently with a background sweep — exactly the "two of them over one directory" the module doc promises can't happen. Two concurrent sweeps each compute `remaining` from their own snapshot and both delete; combined they can overshoot the ceiling badly (the doc says "take the store far below the ceiling either was aiming at"). Also two HTTP sweep requests concurrently bypass each other. The mutex promise "something the type keeps rather than something every caller remembers" is broken by the route calling `sweep()` directly. That's a solid 🔴/🟠 bug. admin.rs:76.

Wait — even in a dry run it also deletes partials? `sweep(dry_run=true)` → `clear_partials(dir, dry_run)` skips removal when dry_run. OK.

3. **Metrics counter/name mismatch**: `values()` returns `[..., sweep_bytes_reclaimed, sweep_blobs_removed]` zipped with COUNTERS in order blobs_removed, bytes_reclaimed. So `cairn_proxy_sweep_blobs_removed_total` gets rendered with the bytes value and vice versa. metrics.rs:94-95 vs 51-57. The doc comment even says "Keeping the two side by side is what stops a fifth counter from being rendered under a fourth one's name" — and they swapped them anyway. 🔴 definite bug: metrics rendered under swapped names.

4. **`scanned` / `held` etc.** fine.

5. **Sweep removes blobs not referenced by index even when under ceiling — including blobs whose index entry write is in flight?** Order in fetch: commit blob → register → link index entry. Between commit and link, blob exists but no index entry points at it. A concurrent sweep would delete it (remove because `!index.contains_key(hex)` — age does not enter, per comment). Then `link` writes an index entry pointing at a nonexistent blob → subsequent serve: resolve hits, open_blob → None → miss → refetch. That's just a refetch, self-healing. Minor. Also `store::remove` (purge) leaves stale entries deliberately, and sweep removes blobs not in index — wait, that logic: `!index.contains_key(hex)` removes blobs that no index entry names. But `BlobStore::remove` (purge) removes blob but leaves index entries — sweep's `referenced` builds index → those entries still name the digest, so hex IS in index → blob is kept?? But blob already gone. Fine.

But consider: a purge removed a blob; index entry remains pointing at it. Sweep: blob doesn't exist, no candidate. forget() only touches gone list. OK.

Now the more subtle one: sweep deletes blobs with no index entry. But are there legitimately-indexed-never blobs? During fetch window (commit→link) yes, brief. Deleting those causes refetch churn but not corruption... except: the fetch is still in flight! In cache.rs `fetch`, after `writer.commit()`, it registers with the registry, then links. If the sweep deletes the blob in that window, then `open_blob` fails → returns `Error::Storage` 500 ("blob committed by this request is already missing"). Actually the code even anticipates that with the error message. So a 500 on the fetch path under concurrent sweep. Combined with the no-age-check for unreferenced blobs. Medium.

6. **`forget()` runs even in dry_run?** In dry_run, `gone` includes candidates that would be removed, and `forget(&index, &gone)` deletes index entry files even in dry-run! Look at sweep(): `forget(&index, &gone)` is called unconditionally at line 140 — `gone` is pushed regardless of dry_run. So a dry-run sweep deletes index entries for blobs it would have removed — "reports what one would reclaim without removing anything" is violated: it removes index entries. Consequence: index entries removed while blob stays → next request misses and refetches (re-downloading and re-linking) — cache entries destroyed by a read-only operation. That's a real bug. sweep.rs:140 within dry_run. 🔴/🟠. The docs promise "with ?dry_run=true reports what one would reclaim without removing anything". Deleting index entries removes nothing permanent but destroys cache mappings → every entry forgotten must be refetched. High severity, clear line.

7. **`age` fallback `unwrap_or_default()`**: a blob whose mtime is in the future gets age 0 — that's fine (it's new). A blob with no mtime gets age 0 — kept. Fine.

8. **Ceiling check `remaining >= self.max_bytes`**: removes until remaining < max. Fine.

9. **`collect` uses `fs::metadata` (follows symlinks)** — comment says "A link is counted at the size of the link and not of whatever it points at", but `fs::metadata` follows symlinks; `fs::symlink_metadata` doesn't. So the comment is wrong: a symlink to a big file is counted at the target's size. That's a doc/behavior mismatch — low severity (🔵). Also a broken symlink is skipped (metadata errors → continue), fine. Actually also a symlink to a directory would be recursed into (is_dir true) → could loop infinitely on a symlink cycle. fs::metadata follows symlinks; a symlink cycle under blobs/ would cause infinite recursion → stack overflow / hang. That's an actual bug: collect recurses through symlinked directories with no cycle protection, and `fs::metadata` follows links contrary to the stated intent. Medium-low.

10. **`main.rs` spawn_sweeps loop**: `app.sweeper.run().await` — run takes mutex and calls sweep (sync blocking). The blocking sweep runs inside the async task on the tokio runtime — blocks a worker thread for the duration of the walk. Documented tradeoff. But worse: with `MissedTickBehavior::Delay`... fine.

Also, sweep task: if `run().await` panics, task dies silently — but no panic expected.

11. **`sweep_interval` validation checks zero but `cache_min_age` not validated** — zero min age is fine (grace of zero).

12. **`Duration::from_hours` / `from_mins`** — these are unstable nightly APIs in std! `Duration::from_hours` and `Duration::from_mins` were stabilized in Rust 1.87? Let me recall: `Duration::from_hours`, `from_mins`, `from_days` — these were stabilized... I believe `Duration::from_mins` etc. were stabilized in Rust 1.87.0 (2025)? Hmm. There's `Duration::from_hours` stabilized in 1.87? Actually I recall `Duration::from_hours/from_mins/from_days` were stabilized in Rust 1.87 (May 2025)? Let me think: these were feature `duration_from_float`? No. `duration_consts_float`? The constructors `from_secs_f64` etc. exist. `Duration::from_hours` was unstable feature `duration_from_hours`? I do recall stabilization of `Duration::from_days`, `from_hours`, `from_mins`, `from_weeks`? Hmm... Actually I don't think they're stable; they were still unstable (`duration_from_hours` feature) for a long time. But the tests at line 350-351 also use `Duration::from_mins(2)` and `from_hours(1)` — the code presumably compiles in this project (maybe pinned nightly). Since I can't verify, and the pre-existing test file maybe already used these... The tests existed? The diff didn't show tests changes in config.rs, but `from_mins`/`from_hours` in tests at line 350-351 — those lines are not in the diff, so they pre-exist. So it compiles in their setup. Not a finding.

13. **routes/mod.rs**: sweep route placed in `untimed` — a sweep of a large store may exceed 10s, so untimed is deliberate. OK. But the admin sweep handler runs the blocking sweep directly in the async handler (no spawn_blocking) — blocks a runtime worker for the whole walk. Same deliberate tradeoff per module docs. I'll skip or mention as low.

Actually wait — is there a timeout concern: sweep route in untimed group but still within TraceLayer. Fine.

14. **metrics.rs `values()` order vs COUNTERS** — covered (#3). Note the comment in metrics says "in the order [`Metrics::values`] reads them" — but values reads bytes_reclaimed before blobs_removed while COUNTERS lists blobs first. Definite swap.

15. **`SweepQuery` dry_run parse**: `?dry_run=true` — bool deserialization accepts "true"/"1"? serde bool from query string via axum Query uses serde_urlencoded — "true"/"false" work, "1"? serde's bool deserializer from urlencoded accepts "true"/"false" only? It accepts "true","false","1","0"? serde_urlencoded parses bool via `bool::from_str`? It uses `serde::de::Unexpected`... serde_urlencoded's deserializer for bool: parses "true"/"false" (case-insensitive?) Actually it handles "true"/"false" and "1"/"0"? Minor; docs say `?dry_run=true`. Fine.

16. **`held` computed after `clear_partials`** — fine.

17. **`reclaim()` in admin: on-demand sweep calls `sweep` (not `run`) — concurrent with background sweep. Also dry-run shares the same issue.** This is finding #2, main.rs line vs admin.rs:76.

18. **cache_min_age unused for unreferenced blobs** — intentional per comment.

19. **sweep removes index entries via `forget` while a concurrent fetch's `link` might re-create them** — race, minor.

20. **`clear_partials` and active fetch interplay** — finding #1. Note fetch timeout 30s on upstream, and downloads are up to 256MiB. The route is untimed; upstream fetch has 30s timeout (fetch_timeout covers the whole upstream fetch? presumably). Even so, a slow download of 256 MiB could take over the sweep interval? 15m interval — unlikely, but admin-triggered sweep anytime makes it likely. Also on a busy proxy with many concurrent fetches, incoming always has in-flight files; every 15m sweep will kill some in-flight downloads. Actually wait: how long does a fetch hold a temp file? `upstreams.fetch` with 30s timeout — bounded by 30s. A sweep every 15 minutes has maybe a small chance of overlapping a 30s fetch window; with, say, dozens of concurrent fetches, chance is nontrivial. And an admin-triggered sweep during a big fetch will kill it. Severity 🟠.

Also note `clear_partials` doesn't respect min_age either — a file created 1 second ago is removed. The doc for min_age says "How long a blob is left alone before a sweep may remove it" — partials are not blobs, arguably. But removing in-flight writes is the bug.

21. **`forget` in dry run** — finding #6, line 140.

22. **metrics docs say six counters "worth having" but `values()`/render**: confirmed swap. Which line to cite: metrics.rs:94-95 (order of loads) — the fault is between COUNTERS (51-57) and values (94-95). Cite metrics.rs:94.

23. **routes/mod.rs removed comment / moved sweep into untimed** — fine deliberate.

24. **Admin sweep bypasses mutex also means concurrent with background sweep → both compute from stale `held` and both remove; the store can be driven far below the ceiling.** Include in finding #2.

25. Another: **`scanned` counts files under blobs only; `held` includes... fine.**

26. **`collect` recursion depth**: blobs/sha256 has 2 levels; index has ecosystem/name/version/file nesting. Depth fine. But symlink cycles — see #9.

27. **Config validation: `cache_min_age` zero allowed** — with min_age=0, every sweep removes all blobs over ceiling down to... fine, operator's choice.

28. **`DEFAULT_CACHE_MAX_BYTES = 32 * 1024 * 1024 * 1024`** = 32GiB, matches .env.example 34359738368 = 32 GiB. ✓.

29. **`spawn_sweeps` before `axum::serve`... the first tick one interval away — doc says so; tokio::interval first tick is immediate!** Wait! `tokio::time::interval` fires the first tick *immediately*. The doc comment in main.rs says "The first tick is one interval away, which is what keeps a proxy that has only just started from sweeping a cache it has not begun to fill." That's wrong: tokio's `interval` completes the first tick immediately. So the proxy sweeps right at startup, every startup. Consequence: a proxy that restarts repeatedly (e.g., crash loop, or frequent deploys) sweeps its full cache at every start — but wait, what would a startup sweep remove? Unreferenced blobs (stale index entries after... no, index intact) — blobs with no index entry and blobs over ceiling. Actually at startup with a full store over the ceiling, an immediate sweep starts evicting immediately — that's maybe desirable. But the doc claims otherwise. Is the immediate sweep harmful? It deletes partials at startup (none), deletes blobs nothing points at — fine. Hmm, is there harm? The comment's claim is false, but the behavior (sweep at startup) mostly harmless. Still, it contradicts the stated intent — 🟡 medium/low: behavior doesn't match documented intent. Actually there's a subtler harm: main.rs comment says it prevents sweeping "a cache it has not begun to fill" — sweeping at startup is harmless-ish. But also: `interval` first tick immediate means spawn_sweeps runs a full synchronous walk at startup, blocking a runtime thread right as the service starts accepting requests. Low-medium. I'd report 🟡: main.rs:108-115 — first tick fires immediately, contradicting the comment and sweeping at startup.

Let me double-check tokio semantics: `interval(period)`: "An interval will tick indefinitely. At any time, the Interval value can be dropped. ... The first tick completes immediately." Yes — tokio::time::interval's first tick completes immediately. Confirmed bug in the comment/behavior.

30. **`run()` vs blocking**: The async task calls `app.sweeper.run().await` — the lock is a tokio Mutex (good, held across await points... but sweep is sync so fine). But the synchronous `sweep` call inside `run` blocks the runtime thread. Deliberate per docs. Skip.

31. **`forget` removes index entries for blobs removed, but blobs removed include those already missing (remove_file failed)** — `gone` includes blobs whose removal failed (e.g., PermissionError) → forget deletes the index entry pointing at a blob that still exists! Wait: remove_file error other than NotFound — comment says "usually a blob that has already gone". If removal fails for a persistent reason (permission), we still push to `gone` and delete index entries → the blob remains but is unreachable → orphaned blob never reclaimable? Actually next sweep: blob is a candidate, index doesn't contain it → remove attempted again. It stays a candidate; fine, eventually consistent-ish. Minor; and bytes counted as reclaimed though not freed → `bytes` overcounts when removal fails. `remaining` decreases even though file still there → sweep reports bytes reclaimed that weren't, and the ceiling accounting thinks it's under the ceiling while the file persists. Next sweep will retry removal. Low. Could report 🔵: sweep.rs:125-137 counts a blob as removed/reclaimed even when `fs::remove_file` fails, so the counters overstate and remaining underestimates. Low severity.

32. **`referenced` reads every index entry with sync fs::read — index walk also counts index files as "candidates"? No, candidates collected only from BLOBS. `collect(dir, &mut entries)` for index — uses `Candidate` with size/age but only path used. OK.

But note: `collect` on the index dir — index entries are files; if an index entry is itself a directory (weird), recursion. Fine.

33. **`held` vs metric "Bytes of blob the store held"** — includes files in blobs only; symlinks counted at target size (see #9).

34. Now the security check on the sweep route: it's auth'd like purge. Placed in `untimed` router — fine. But wait: is `/v1/admin/cache/sweep` POST route added to `untimed` which is merged into `bounded` which has TimeoutLayer of 10s applied to `bounded`... Let me re-read routes/mod.rs merged structure. In the diff, `bounded` gets TimeoutLayer(10s), then `.merge(untimed)`. Wait — order matters: if TimeoutLayer is applied to `bounded` before merging, then merged routes... In axum, `merge` combines routers; layers applied via `.layer()` on `bounded` apply only to routes added to `bounded` before the `.layer()` call? Actually `Router::layer` wraps all routes currently in the router. Routes added after (via merge) are not wrapped. Let me check the actual file to see the order of `.layer` vs `.merge`.
The `sweep` handler calls `sweeper.sweep()` directly rather than `run()`, and the metrics ordering looks swapped. Let me check the router wiring order and the digest/error helpers the sweep relies on.
└ 4414 tok ·  96.4 tok/s · 31K ctx · 1318ms ttft · 45.8s wall
↳ read_file: read pr/services/proxy/src/routes/mod.rs
└ read_file: read complete
↳ read_file: read pr/services/proxy/src/digest.rs
└ read_file: read complete
-- reasoning --
Now let me analyze the defects.

1. **Metrics ordering bug** (metrics.rs): `COUNTERS` order is blobs_removed then bytes_reclaimed (indices 4,5), but `values()` returns bytes_reclaimed then blobs_removed. So `cairn_proxy_sweep_blobs_removed_total` gets rendered with the bytes value and vice versa. Concrete defect — metrics.rs:88-96 vs 33-58. Severity: medium/orange? It corrupts the metrics that operators alert on per the docs ("Watch cairn_proxy_sweep_bytes_reclaimed_total"). I'd call it 🟠 high.

2. **`forget` bug** (sweep.rs:249-256): `forget(&index, &gone)` deletes index entries for removed digests. But `gone` includes blobs removed due to being unreferenced — those are unreferenced so no index entries anyway (fine). For blobs removed due to the ceiling, `forget` removes the index entries even in **dry_run**! In dry_run, no blob is removed, but `gone` is still populated, and `forget` unconditionally does `fs::remove_file(path)` on index entries. So a dry run deletes index entries while leaving blobs — well, index entries deleted while blobs remain; next request treats as miss and refetches + relinks. Not data loss but the dry run "reports what one would reclaim without removing anything" — it removes index entries. That's a real bug: sweep.rs:140 calls forget unconditionally, including in dry_run. Line: sweep.rs:140 (and forget fn 249). That's the big one: dry_run promises "without removing anything" (admin.rs doc, docs) but deletes index entry files. Severity: orange/high.

   Wait, double-check: in dry_run, remove=true branch still pushes to `gone` (line 137). Yes, `gone.push(hex.to_owned())` happens regardless of dry_run. Then forget unconditionally removes files. Confirmed.

3. **Blocking sync I/O on the async runtime** (sweep.rs): the module doc explicitly says the walk is synchronous std-lib calls — but `Sweeper::run()` is async and calls `self.sweep(false)` while holding the tokio Mutex, executed directly on a tokio worker thread. `Sweeper::sweep` does blocking fs I/O on the async executor (main.rs:116 `app.sweeper.run().await` in a tokio::spawn task). For a large store this blocks a runtime worker thread for potentially many seconds/minutes. It's an intentional trade-off per the doc comment ("One pass of standard-library calls costs less than the scheduling would") — they rejected tokio::fs but didn't use spawn_blocking. Blocking the runtime worker is a real issue but the doc acknowledges the sync walk; however blocking the async runtime (vs. tokio::task::spawn_blocking) still starves other tasks. This is a deliberate documented choice; medium at best. Hmm. The doc argues against tokio::fs round trips, but spawn_blocking would run the whole walk on one blocking thread — they didn't consider that. I'd report as 🟡 performance.

4. **`sweep` route doesn't take the mutex / races with background sweep** (admin.rs:76): `reclaim()` calls `app.sweeper.sweep(dry_run)` directly instead of `app.sweeper.run()`, bypassing the `running: Mutex`. The module doc says "One sweep at a time... this module's one-at-a-time promise is something the type keeps rather than something every caller remembers" — but the HTTP handler calls `sweep()` directly, which does not take the lock. So an on-demand sweep can run concurrently with the background sweep, exactly the interleaving the mutex exists to prevent: both compute `held` from the same store, both remove down to the ceiling, taking the store far below the ceiling. Also a dry_run concurrent with a real sweep gives inconsistent numbers. Concrete: admin.rs:76 should be `run()`/lock. Severity: 🟠 (causes over-eviction under operator action, exactly when disk is full and someone runs it).

   Also in dry-run the handler could use run() and lock... but run() forces dry_run=false. Still, the non-dry path is the dangerous one.

5. **`clear_partials` counts entries it can't remove**? It increments only on success (or dry run). Fine. But it removes subdirectories? `fs::remove_file` on a directory fails → logged and continue. incoming only has files. Fine.

6. **Dry run counts... actually in dry_run, `remove_file` not called but removed incremented — matches "what a pass would reclaim". OK.

7. **`forget` in dry run also deletes entries for blobs the dry run "would" remove** — covered by #2.

8. **Race between sweep and cache writes**: `clear_partials` deletes every file in `incoming`, including temp files of in-flight downloads (BlobWriter temp_path lives in incoming). A sweep deletes the partial of an active fetch; the writer keeps writing to the unlinked inode, and commit's rename fails (file gone → rename of missing file errors) → fetch fails with an io error. That's a real defect: sweep.rs:224-240 removes files regardless of age (no min_age for partials), while active downloads legitimately have files in `incoming`. Docs claim "A file in `incoming` is a fetch that is not coming back" — false for in-flight fetches which can take up to fetch_timeout 30s. An operator-triggered sweep during heavy download traffic kills in-flight fetches. Severity: 🟠 or 🟡. I'd say 🟡/🟠. Consequence: concurrent downloads fail with storage errors. Given an admin sweep is triggered exactly when disk is full (busy traffic), it's likely. 🟠 maybe. I'll go 🟡... Actually the consequence is a failed client build; medium. 🟡.

9. **`age_of` uses modified time; metadata follows symlinks** (fs::metadata follows links — consistent with doc). `collect` on blobs: uses file_name as hex; fine.

10. **Sweep deletes blobs not in the index that are currently being written/served?** A blob just committed but before `link()` — index doesn't contain the digest yet, so sweep removes it: the fetch that just committed then `open_blob` fails → 500 "blob committed by this request is already missing". Timing: commit → register_version (network call, up to seconds) → link. During that window a sweep deletes the blob as unreferenced. Race exists but the min_age doesn't apply to unreferenced blobs ("Age does not enter into the first"). Background sweep every 15 min, small window — low severity, but real. Also a blob being *served* right now from an index entry: sweep removes it (over ceiling) while a download streams it — unlink on open file is fine on Unix; serve continues. OK. The commit-window race: 🟡 or 🔵. Actually the comment in cache.rs:90-97 anticipates outside deletions. I'd mention 🔵 maybe. Hmm, but this is a genuine consequence: concurrent miss + sweep → client gets 500 instead of the artifact. Report as 🔵/🟡.

11. **`held` sums only blob candidates but ceiling enforcement compares `remaining >= self.max_bytes` where remaining starts at `held`** — includes blobs that will be removed as unreferenced? No wait — candidates sorted by age; the loop removes unreferenced ones whenever encountered and subtracts. remaining tracks the total correctly. OK.

    But note: the condition `remaining >= self.max_bytes` — blobs with age < min_age are kept, so if all old blobs removed and still over ceiling, loop stops (youngest kept). Fine, that's design.

12. **`scanned` counts blobs, fine. `partials` not counted in `bytes`/`removed` metrics — metrics record only removed/bytes; partials bytes unaccounted. Minor; docs say bytes_reclaimed is "Bytes those blobs occupied. Blobs only." Intentional.

13. **config: `cache_min_age` not validated** — no zero check; min_age zero means everything evictable immediately. That's arguably fine (operator choice). Not a defect.

14. **`Duration::from_hours` / `from_mins`** — these are stable Rust? `Duration::from_hours` was stabilized in Rust 1.87? Actually `Duration::from_hours`/`from_mins`... `Duration::from_secs_f32` etc. Hmm. `Duration::from_hours` is unstable (`duration_consts_float`? no—`Duration::from_hours` is `duration_from_hours` unstable feature). Let me think: Rust stabilized `Duration::from_weeks`? No — `from_weeks`/`from_days`/`from_hours`/`from_mins` are unstable under `duration_constants` feature. As of Rust 1.53 they were nightly-only; still unstable as of 2025? I believe `duration_constants` is still unstable. Hmm, actually I recall `Duration::from_hours` still unstable on stable as of 1.80s. Let me check: there is `core::time::Duration::from_hours` tracked in issue #120301, feature `duration_constants`, still unstable. So `const DEFAULT_CACHE_MIN_AGE: Duration = Duration::from_hours(1);` would fail to compile on stable. But wait — config.rs tests already use `Duration::from_mins(2)` in existing test code (line 350 pre-existing? test at line 350 `assert_eq!(parse_duration(" 2m "), Ok(Duration::from_mins(2)))` — that's in the existing test file since tests reference it; the diff didn't add that). Hmm, the test line exists in the checked-out file but tests may be pre-existing code... The diff doesn't show tests being added, so `from_mins` usage in tests pre-exists. If it compiles, then maybe the project uses a nightly or the feature got stabilized. I can't run cargo. Risky to report. Also main.rs uses `env!("CARGO_PKG_VERSION")` etc. I'll skip — can't verify toolchain. Actually wait, could check whether the repo has rust-toolchain file. Not worth it; pre-existing test uses from_mins, so if it compiles it compiles. Skip.

15. **`main.rs` shutdown**: spawn_sweeps task holds... on graceful shutdown the sweep task is aborted when runtime drops. Fine, documented.

16. **Sweep task never yields during long sweep** — combined with #3.

17. **Admin sweep route has no timeout** (untimed) — a blocking sweep inside the handler blocks the whole runtime worker including... axum serve runs on multi-thread runtime, one worker blocked but others continue. With #3, a big sweep could block one worker for minutes. Combined severity.

18. **`reclaim()` in admin.rs runs synchronous blocking sweep inside async handler** — same as #3, blocking a runtime thread, and the mutex in run() is not used for the route, so also #4.

19. **SweepQuery dry_run deserialization**: `?dry_run=true` — bool parses "true". `?dry_run` alone fails (missing value for bool → 400). Fine.

20. **`forget` removes index entries even for digests removed... in dry_run** — #2. Also in dry run, `gone` non-empty → forget deletes entries. Confirmed the biggest bug.

21. **Metrics doc comment mismatch**: "Keeping the two side by side..." fine.

22. Another: **metrics values order vs COUNTERS** — #1.

23. **`clear_partials` in dry run counts files it couldn't... fine.

24. **sweep removes blobs but `held` computed before partial clearing** — partials aren't blobs; fine.

25. **Route path conflict**: `/v1/admin/cache/{digest}` DELETE vs `/v1/admin/cache/sweep` POST — different methods, no conflict.

26. **`collect` for index reads each file then `forget` removes them; index dir walk uses `collect` which pushes all files including non-JSON. Fine.

27. **Symlink following in `collect`**: `fs::metadata` follows symlinks; a symlinked subdirectory could cause cycle/infinite recursion? A link to a parent dir → infinite recursion. Edge case; doc mentions links counted by size. Follows symlink to file counts target's size (contradicts comment claiming link counted at size of link — `fs::metadata` follows, so it's target size; `symlink_metadata` would be link size). Hmm, comment says "A link is counted at the size of the link and not of whatever it points at" — but `fs::metadata` follows symlinks, so size is of the target. The comment is wrong, but behavior: following symlinks also risks recursing into symlinked directories → potential infinite loop / double-counting blobs linked in from elsewhere (over-counting → over-eviction). Minor. Could report as 🔵 correctness: comment vs fs::metadata. It's a real mismatch: the code doesn't do what the comment claims. 🔵.

Let me also double check the mutex-bypass severity: `run()` locks, `sweep()` public doesn't. Handler calls `sweep(dry_run)` directly (admin.rs:76). Yes.

Also `spawn_sweeps` holds `app` clone forever — after graceful shutdown completes, serve returns, but the sweep task keeps runtime alive? `main` returns after serve() returns; #[tokio::main] shuts down runtime, which waits for... runtime shutdown waits for blocking tasks; spawned tasks are dropped at runtime drop. Actually `Runtime::shutdown` waits for tasks to complete? Dropping the runtime cancels tasks. `#[tokio::main]` drops the runtime at the end of async main, which... when a runtime is dropped while inside it (from within the async block?), actually main's future completes and then Runtime is dropped, canceling spawned tasks. There's a known subtlety: dropping runtime from within runtime context panics? No — `#[tokio::main]` handles it fine. Skip.

One more: `sweep` in admin runs blocking I/O while holding no lock; and `run()` in the background holds the tokio Mutex across a blocking call — another task awaiting the lock blocks a worker, but that's an async wait, fine.

Also: **`record_sweep` double counting for on-demand sweep** — handler records metrics; background task also records. Fine, not double for same sweep.

Metrics severity: values swapped → the two sweep counters render each other's values. The docs tell operators to watch `cairn_proxy_sweep_bytes_reclaimed_total`. That's a high-ish bug but the fix is trivial; I'd rate 🟠.

Dry-run deleting index entries: 🟠 (violates explicit promise; consequence: cache invalidated → refetch storm; also for blobs that "would" be removed, entries deleted while blobs kept — inconsistent).

Race killing in-flight downloads via clear_partials: 🟠? The sweep has no age filter on incoming files. A download in progress has temp file in incoming; background sweep (15m interval) rarely collides, but on-demand sweep under disk pressure collides likely, and consequence is a failed fetch (client error, retryable). Also worse: partial removal while writing — writer keeps writing to unlinked file, commit rename fails → Error::Storage → 500. I'll rate 🟡.

Commit-window race (blob unreferenced between commit and link): 🔵.

Blocking runtime: 🟡 performance.

Symlink comment mismatch: 🔵.

Line numbers in changed files:
- metrics.rs: `values()` lines 88-97; order swap vs COUNTERS at 50-57. Point at 94-95.
- sweep.rs:140 `forget(&index, &gone);` — dry run deletion. Point at 140 (or 249-256).
- admin.rs:76 `app.sweeper.sweep(dry_run)` bypassing mutex.
- sweep.rs:230-238 clear_partials removing in-flight temp files.
- sweep.rs:90/84 blocking call in async context (run at 82-85 calls sweep directly on the runtime thread; main.rs:116 awaits it in tokio::spawn). Point at sweep.rs:84 or 90. Category performance.
- sweep.rs:164 fs::metadata follows symlinks contradicting comment. 🔵.
- sweep.rs:119 unreferenced-blob removal with no age guard hitting commit-window blob → 500. 🔵. Maybe skip to avoid padding? It is concrete and line-pointable. Include as 🔵.

Also check `Reclaimed` serialization: `?reclaimed` in tracing with Debug — fine.

One more possible: `held` includes blobs; the ceiling check `remaining >= self.max_bytes` — when store at exactly max, evicts. Fine.

Also `.env.example` says CAIRN_CACHE_MAX_BYTES default 34359738368 = 32 GiB ✓.

Also config validation: no check that cache_min_age... fine.

Check `parse_bytes` for "256 mib" — trim_end_matches alphabetic handles spaces? digits = "256 ", unit = "mib"; digits.trim() parsed. OK pre-existing.

Dry-run also counts partials it would remove — reports in `partials` field, doesn't remove. OK.

Wait, one more on forget: it also deletes index entries for digests that were removed because unreferenced — but those have no index entries by definition (index map only contains digests parsed from index). `index.get(hex)` for unreferenced digest returns None. Fine.

Another: in dry_run, metrics not recorded ✓.

Also, does `forget` in a dry run mean the *next* real sweep deletes the blobs? No — blobs remain, index entries gone → blobs become unreferenced → next sweep removes them. So a dry run causes actual removals later. Include that consequence.

Final list:

🟠 bug metrics.rs:94-95 — sweep counters rendered under each other's names.
🟠 bug sweep.rs:140 — dry run deletes index entries.
🟠 bug admin.rs:76 — bypasses mutex, concurrent sweeps.
🟡 performance sweep.rs:84 — blocking fs walk on async runtime worker.
🟡 bug sweep.rs:232 — clear_partials removes temp files of in-flight downloads (no age check).
🔵 bug sweep.rs:119 — newly committed blob deleted before link → 500.
🔵 bug sweep.rs:164 — fs::metadata follows symlinks; comment claims link-size counting; symlinked dirs → recursion/over-count.

That's 7 findings, each line-pointable. Good.
Review complete. Findings:

🟠 `bug` services/proxy/src/metrics.rs:94: `values()` returns `sweep_bytes_reclaimed` then `sweep_blobs_removed`, but `COUNTERS` (lines 50-57) lists `..._blobs_removed_total` first, and `render` zips the two — each scrape renders the byte count under `cairn_proxy_sweep_blobs_removed_total` and the blob count under `..._bytes_reclaimed_total`. Operations.md tells operators to alert on `cairn_proxy_sweep_bytes_reclaimed_total`, which would actually report blob counts.

🟠 `bug` services/proxy/src/sweep.rs:140: `forget(&index, &gone)` runs unconditionally, but `gone` is populated even when `dry_run` is true (line 137), and `forget` really deletes the index files (line 252). A `?dry_run=true` sweep — documented as reporting "without removing anything" (admin.rs, operations.md) — deletes index entries for blobs a hypothetical sweep would remove, turning "would be reclaimed" into "will be reclaimed": the surviving blobs become unreferenced and the next real sweep takes them.

🟠 `bug` services/proxy/src/admin.rs:76: `reclaim` calls `app.sweeper.sweep(dry_run)` directly, bypassing the `running` mutex that `Sweeper::run` (sweep.rs:82-85) exists to take. An on-demand sweep therefore runs concurrently with the background sweep — both compute `held` from the same store and each evicts down to the ceiling, taking the store far below the ceiling either aimed at, exactly the failure the module doc (sweep.rs:10-12) says the type prevents.

🟡 `performance` services/proxy/src/sweep.rs:84: `run` is `async` but calls the fully synchronous `self.sweep(false)` — a blocking recursive `read_dir`/`remove_file` walk over up to tens of thousands of files — directly on a tokio worker thread (spawned at main.rs:116), stalling that worker for the whole pass instead of using `tokio::task::spawn_blocking`. The module doc rejects `tokio::fs` per-call overhead but not the blocking-the-executor cost; the route handler (admin.rs:76) blocks a worker the same way inside an async request.

🟡 `bug` services/proxy/src/sweep.rs:232: `clear_partials` removes every file in `incoming` with no age check, but `incoming` is also where live downloads are written (`temp_path`, store.rs:201-206, files that persist for the up-to-30s `fetch_timeout`). A sweep concurrent with traffic unlinks temp files of in-flight fetches; the writer keeps writing to the unlinked inode and `commit`'s rename fails (store.rs:259), so clients get 500s. The comment's premise ("a file in `incoming` is a fetch that is not coming back") is false for fetches still in flight.

🔵 `bug` services/proxy/src/sweep.rs:119: a blob with no index entry is removed regardless of age. Between `writer.commit()` (cache.rs:151) and `store.link()` (cache.rs:163) there is a window — the registry registration network call — during which the just-committed blob is on disk but unreferenced, so a sweep in that window deletes it and the client gets the "blob committed by this request is already missing" 500 (cache.rs:90-97). The min-age grace period is documented as covering "a package one job in a pipeline fetched" but does not cover this case.

🔵 `bug` services/proxy/src/sweep.rs:164: `fs::metadata` follows symlinks, so the comment's claim that "a link is counted at the size of the link and not of whatever it points at" is false — linked-in blobs are counted at their target's full size (over-counting toward eviction), and a symlinked directory is recursed into (line 168), which on a link pointing back up the tree never terminates. `symlink_metadata` plus a link/skip decision is what the comment describes.
└ 4934 tok ·  90.4 tok/s · 35K ctx · 3045ms ttft · 54.6s wall