sandbox:read-only (macOS Seatbelt)
-- reasoning --
Let me review the code. Key areas: sweep.rs logic, metrics ordering, config, routes.

Let me read the actual files under pr/ to check line numbers and context.

Potential defects I can spot from the diff:

1. metrics.rs: COUNTERS order vs values() order. COUNTERS array lists sweep_blobs_removed first, then sweep_bytes_reclaimed. values() returns sweep_bytes_reclaimed then sweep_blobs_removed. So the labels are mismatched — cairn_proxy_sweep_blobs_removed_total will report bytes reclaimed and vice versa. That's a bug. Need to check render code to confirm COUNTERS and values are zipped.

2. sweep.rs: the sweep decides removal but removes blobs whose age >= min_age; but when checking `remaining >= self.max_bytes` — remaining decreases; fine. But note: blobs not referenced (no index entry) are removed regardless of age — but also index entries for removed blobs get removed via forget. But forget only runs for blobs removed... `gone` includes all removed. But forget removes index entries for any removed digest, fine.

3. Bug: In sweep, when a remove_file fails (blob already gone), it still counts bytes and removed — reports metrics for bytes not reclaimed. Also `remaining` still decremented. Minor accounting bug. Actually if file removal failed, the blob is still there, but counted as reclaimed. Consequence: over-reported; next sweep still over ceiling... minor/medium.

4. clear_partials: removes ALL files in incoming, including files being actively written by in-flight fetches! BlobWriter writes temp file in incoming then renames. A sweep running concurrently with an active fetch would delete the partial being written, so the fetch's rename would fail. Need to check store.rs BlobWriter to see if incoming files are per-fetch. Also no age check on partials — the docs in .env say "How long a blob is left alone before a sweep may remove it" — min_age not applied to partials. A fetch in progress would have its temp file deleted mid-write. This is a real bug: race with concurrent writes. Need to check store.rs to see how writes work — whether the writer holds the file handle (deleting the path mid-write on Unix is fine, rename would fail with ENOENT). So the in-flight fetch fails, the fetch is retried... consequence: fetch error. And partials counter counts files being written. Worth checking store.rs.

5. routes/mod.rs: removed the comment about cache route but kept behavior. The sweep route outside timeout — a sweep of huge store could take long; deliberate.

6. admin.rs: sweep route authorise first — ok. `reclaim` calls `app.sweeper.sweep(dry_run)` directly, not `run()` — so an on-demand sweep doesn't take the mutex! The one-at-a-time promise: `run()` locks, but `sweep()` is called directly from the route handler, bypassing the lock. So a manual sweep can run concurrently with a background sweep — exactly the interleaving the module doc says must not happen ("Two of them over one directory would each decide what to remove from a total the other is already changing"). That's a real bug in admin.rs. The comment in Sweeper says "Held for the whole of a sweep, so this module's one-at-a-time promise is something the type keeps rather than something every caller remembers" — but the type doesn't keep it because sweep() is public and called directly. Definitely report.

7. Blocking: sweep() does synchronous fs I/O on the tokio runtime thread (the doc says deliberately synchronous). Called from an async handler — blocks the executor thread. The doc justifies for background task, but the route handler calls it synchronously in async context — blocking the runtime. Could be a finding (performance, medium). The doc comment in module says the walk is synchronous intentionally... but calling from the HTTP handler blocks a worker thread for potentially minutes. Worth 🟠 or 🟡.

8. Config: cache_min_age has no validation (can be zero — that's arguably fine, means no grace). sweep_interval zero check exists. cache_max_bytes zero check exists. OK.

9. main.rs spawn_sweeps: uses app.cfg — fine. `tracing::info!(?reclaimed, ...)` fine.

10. forget(): removes index entries for blobs removed. But if a blob was removed because not in index (index.contains_key false), forget does nothing for it — fine. But there's a bug: forget removes index entries when the blob is removed, but the dry run also calls forget? No — forget is called regardless of dry_run! In sweep(), after the loop, `forget(&index, &gone)` is called unconditionally — in a dry run, it deletes index entries for blobs it claims it would remove! That's a serious bug: dry run "removes nothing" but actually deletes index entries. Check: `let mut gone = Vec::new(); ... gone.push(hex.to_owned());` happens in both dry and non-dry runs. Then `forget(&index, &gone);` outside any dry_run check. Yes — dry run deletes index entries. That means the "would remove" set actually loses its index entries, so the next sweep will consider those blobs unreferenced and delete them regardless of age. Real bug, high severity. Also the docs promise dry run "reports what one would reclaim without removing anything" — it removes index entries.

11. In sweep, the removal condition `remaining >= self.max_bytes` — remaining starts at held; if held >= max, remove oldest. Fine. But `index.contains_key(hex)` — hex is file name from path; index keys are digest hex. Blob file names presumably digest hex. OK.

12. collect() uses fs::metadata which follows symlinks — for symlinks, metadata follows; size of target, contradicting the comment about links counted at link size (they use fs::metadata which follows symlinks, so a symlink to a big file counts target size; symlink_metadata wouldn't). The 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 it counts the target size. Bug: comment vs code mismatch; use fs::symlink_metadata. Medium/low.

13. clear_partials: no dry-run counting... it counts removed in dry_run too (removed += 1 when dry_run, without removing). Good for reporting. But it deletes in-flight temp files — check store.rs.

14. Reclaimed held: bytes of blob only; fine.

15. metrics: values order mismatch confirmed — COUNTERS[4] is sweep_blobs_removed_total but values()[4] is sweep_bytes_reclaimed. Need to see render function to confirm pairing. Let me read metrics.rs.

16. routes/mod.rs: moving sweep route out of timeout — fine.

17. admin.rs: `use axum::Json` conflicts with existing import? The file already imports? Line shows `use axum::{Json};` added; there might be an existing `use axum::Json` in the file causing a compile error (duplicate import). Need to check admin.rs imports. Diff shows removal of `use axum::extract::{Path, State};` replaced with added Query; and adds `use axum::Json;` and `use serde::Deserialize;`. If the file already had `use axum::Json` elsewhere (for purge response?), duplicate import = compile error. Need to read the file.

Also `RequestId` extractor — admin.rs needs it imported; check.

Let
└ 1651 tok · 121.6 tok/s · 12K ctx · 1180ms ttft · 13.6s wall
↳ 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
↳ read_file: read pr/services/proxy/src/sweep.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 --
Now I need to look at store.rs to understand the layout: blob paths, index entries, how `resolve` works, whether blobs are stored under blobs/sha256/<hex> or in subdirectories (e.g. sharded by prefix). Also check main.rs, routes/mod.rs, config.rs.

Key potential defects in sweep.rs:

1. **collect on INDEX dir**: `referenced` calls `collect(dir, ...)` which pushes Candidates for every file, but collect also recurses. Fine. But `collect` for the index builds Candidate structs — harmless.

2. **clear_partials deletes files in incoming even when they're actively being written!** A fetch in progress writes a temp file in `incoming`. The sweep deletes it while a live fetch is writing. The comment says "A file in `incoming` is a fetch that is not coming back" — but a concurrent fetch writes there. Need to check store.rs to see whether writes go into `incoming` with no age check. If so, a sweep can delete a partial being written by a live request, causing the writer to fail or worse: writer finishes hashing, then tries to rename/re-link the file that no longer exists → error or... Actually on Unix, the writer holds an open file handle; deleting the path means rename fails (ENOENT) or the write continues into an unlinked inode — bytes lost but no corruption. The fetch fails; client retries. Still a defect: sweep kills in-flight fetches. Note `clear_partials` doesn't respect min_age either — even blobs get min_age grace, but in-flight partials get none. Worth checking store.rs for naming scheme. This could be flagged medium.

3. **Eviction loop condition `remaining >= self.max_bytes`**: this uses `>=` so blobs removed until remaining < max_bytes. That means the store stays under ceiling. But blobs with age < min_age can never be removed, so if store holds > max_bytes of fresh blobs, the sweep can't fix it — acceptable, documented.

But bigger bug: **`remaining` accounting treats blobs not referenced by index as reclaimable regardless, fine. However, the removal condition is evaluated with `remaining` decreasing; when store is under ceiling, no age-based removal. OK.

4. **`remove = !index.contains_key(hex)` then `forget` removes index entries for gone blobs.** But blobs removed due to ceiling overflow that ARE in the index: `gone.push(hex)` includes them, so `forget` deletes their index entries. That's intended ("Drops the index entries naming digests that are no longer in the store").

But wait: a blob that fails to be removed (fs::remove_file error, e.g. already gone via purge) is still counted in `bytes` and `removed` and pushed to `gone`, then `forget` deletes its index entries — deleting index entries for a blob that still exists on disk (if remove failed for a different reason, e.g. EPERM) — index entry removed but blob remains, orphaning a live blob; next sweep it's unreferenced and gets removed. Minor.

Also `removed` and `bytes` count blobs that failed to be removed — counters overstate. Also dry_run: `bytes` counted without removal, fine.

Bigger issue: **metrics double counting**: `admin::reclaim` calls `app.sweeper.sweep(dry_run)` directly, NOT `run()` — so the on-demand sweep does NOT take the `running` mutex! The mutex is only in `run()`. So an on-demand sweep can run concurrently with a background sweep, defeating the "one sweep at a time" promise that the type claims to keep ("Held for the whole of a sweep, so this module's one-at-a-time promise is something the type keeps"). That's a real bug: routes/admin.rs:76 calls `sweep` instead of `run`. Severity: orange/high. The two sweeps would each compute `held` from the other's changing state and double-remove / take store far below ceiling. Also, sweep() is sync and runs on the async runtime thread — blocking the executor for a long walk. The route handler calls `sweep` synchronously in an async fn, blocking the tokio worker thread — documented rationale for sync walk was about avoiding tokio::fs round trips, but running it inline on the runtime blocks a worker; also route is in "untimed" router so no timeout, but the sync walk blocks. That might be intentional design ("The walk is synchronous"). Hmm, the module doc justifies sync std-lib calls but running it directly on the async executor blocks the runtime thread. With multi-thread runtime maybe tolerated. Could flag blue.

5. **Missing min_age check for unreferenced blobs**: documented intentionally.

6. **clear_partials during dry_run**: fine.

7. **`collect` uses `fs::metadata` which follows symlinks** — comment says links counted at link size, but `fs::metadata` follows symlinks, returning target metadata (target size, and is_dir if target is dir → recursion into symlinked dirs → potential infinite loop / escaping the store!). Should use `symlink_metadata`. The comment claims link counted at size of the link, which is wrong: `fs::metadata` follows the link. So a symlink to a huge file counts target size; worse, symlink to a directory recurses. That's a bug: sweep.rs:164. Orange.

8. **First sweep timing**: main.rs says first tick is one interval away — correct for tokio interval. OK.

9. **Metrics COUNTERS order vs values order**: COUNTERS lists blobs_removed first, then bytes_reclaimed. values() returns bytes_reclaimed first, then blobs_removed. So the names and values are mismatched! Line 51-57 in COUNTERS: index 4 = sweep_blobs_removed_total, index 5 = sweep_bytes_reclaimed_total. values() index 4 = sweep_bytes_reclaimed, index 5 = sweep_blobs_removed. So `cairn_proxy_sweep_blobs_removed_total` renders bytes, and bytes renders blob count. Real bug! metrics.rs:88-96 vs 51-57. That's a definite mismatch — high severity (operators alert on wrong numbers). Note doc comment says "in the order [`Metrics::values`] reads them" — but they don't match.

Wait — check carefully. COUNTERS entries 5 and 6 (indices 4 and 5):
- index 4: "cairn_proxy_sweep_blobs_removed_total"
- index 5: "cairn_proxy_sweep_bytes_reclaimed_total"

values():
- index 4: sweep_bytes_reclaimed.load
- index 5: sweep_blobs_removed.load

Yes, swapped. Definite bug.

10. **config.rs**: `Duration::from_hours` / `Duration::from_mins` — std::time::Duration has no from_hours/from_mins! Those are humantime or `std::time::Duration::from_secs(3600)`. Actually Rust std Duration added `from_hours`? No — std has from_secs, from_millis, from_micros, from_nanos. There's no from_hours or from_mins in std. Unless they use a crate... config.rs imports? Need to check pr/services/proxy/src/config.rs imports. If std::time::Duration, this won't compile. Let me check.

11. **Validation missing for cache_min_age**: sweep_interval.is_zero checked, cache_max_bytes==0 checked, but cache_min_age has no validation (zero allowed — probably fine).

12. **routes/mod.rs**: comment removed about cache route timeout... they moved it. The sweep route placed in untimed router — fine. But note the TimeoutLayer applies to bounded; merging untimed after... original code did same.

13. **main.rs spawn_sweeps**: `app.sweeper.run()` — run acquires mutex; background loop fine. `tracing::info!(?reclaimed, ...)` fine.

14. **admin sweep route: no timeout and synchronous walk blocking runtime** — as noted.

15. **`forget` removes index entries for blobs removed due to ceiling — including blobs whose index the *database* says are cached?** docs say metadata stays in DB and set cached_at null. Sweep doesn't touch DB — the dashboard "stops claiming they are cached"? In operations doc they previously said set cached_at null manually. Not code defect.

16. **Race between sweep and store writes**: A blob just written (rename into place) but index entry not yet written? Order matters — check store.rs: if blob is renamed into blobs/ then index entry written after, a sweep between the two steps sees an unreferenced blob and deletes it immediately (age ~0, but unreferenced branch has no age check). Then index entry points at nothing. Fetcher then... The store::store function probably writes blob then index. The race window is tiny but real. More importantly, concurrent in-flight fetch: the writer writes to incoming; sweep deletes the partial (bug #2); then writer renames → fails. Also: writer computes digest, renames file into blobs/sha256/<hex>, then writes index entry. If sweep runs between rename and index write, blob gets deleted as unreferenced; subsequent index entry points at missing blob → resolve returns path that doesn't exist → served 404? Need to check store.rs resolve behavior — does it check existence? Let me read store.rs.

Also `forget` deletes index entries pointing at blobs that were removed — but blob removal may have failed (line 126 error is swallowed and blob still counted removed, pushed to gone, index entry deleted even though blob still exists on disk). Then that blob is on disk but unreferenced; next sweep removes it. Minor inconsistency; probably blue.

Also: blobs removed via ceiling branch are counted in `removed` even if removal failed — metrics overstate. Combined into above.

Let me now read store.rs and config.rs and main.rs.
└ 2141 tok · 143.0 tok/s · 18K ctx ·  910ms ttft · 15.0s wall
↳ read_file: read pr/services/proxy/src/store.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/main.rs
└ read_file: read complete
-- reasoning --
Let me analyze the diff for defects.

1. **metrics.rs values order vs COUNTERS**: COUNTERS order: cache_hits, cache_misses, upstream_failures, policy_refusals, sweep_blobs_removed, sweep_bytes_reclaimed. But `values()` returns sweep_bytes_reclaimed (index 4) and sweep_blobs_removed (index 5) — swapped! So `cairn_proxy_sweep_blobs_removed_total` is rendered with the bytes value and vice versa. That's a real bug: metrics.rs:88-96 vs COUNTERS 51-57. Consequence: blobs-removed counter reports bytes, bytes counter reports blob count.

Wait — record_sweep(blobs, bytes) → sweep_blobs_removed.fetch_add(blobs), sweep_bytes_reclaimed.fetch_add(bytes). So the atomics are correct. But values() loads sweep_bytes_reclaimed in position 4 where COUNTERS[4] = sweep_blobs_removed. Yes, swapped. Bug — orange/yellow. Consequence: alerts on `cairn_proxy_sweep_bytes_reclaimed_total` (docs/operations.md tells operators to watch it) get the blob count instead. That's high — orange.

2. **sweep.rs clear_partials deletes files in `incoming` that are actively being written**. BlobWriter writes to temp files in `incoming/` while a fetch is in progress. clear_partials removes every file in incoming with no age check — it deletes partial writes of in-flight fetches! A sweep at the 15-minute interval will unlink files that active downloads are writing to. The docstring claims "A file in `incoming` is a fetch that is not coming back" — false; an in-flight fetch is in incoming. Consequence: active download's temp file is unlinked; on commit, rename fails (error) — the fetch fails. Under CAIRN_CACHE_MIN_AGE's spirit this is a bug. This is a real defect: sweep.rs:224-239 (or line 230-232). Severity: orange/red? A 200 MiB artifact download takes minutes; a sweep every 15m will kill in-flight fetches. The doc claims CAIRN_CACHE_MIN_AGE protects "a package one job in a pipeline fetched is still there for the next" but partials have no grace. I'd say orange (high).

3. **Sweep route runs blocking I/O on the async runtime thread without spawn_blocking** — the docstring acknowledges the walk is synchronous, and `run()` (background) is in a spawned task, fine-ish. But the admin route `reclaim()` calls `app.sweeper.sweep(dry_run)` synchronously inside the axum handler — blocking the tokio worker thread for the entire walk of potentially 65k files plus JSON reads of the whole index. The route deliberately sits outside the timeout layer, so the whole server's worker threads can be blocked. That's a performance defect: routes/admin.rs:76 (sweep.rs:90). Orange/yellow.

4. **routes/mod.rs timeout comment removal**: bounded routes... the sweep route placed in "untimed" router. Fine.

5. **`forget` removes index entries for blobs removed, but also for blobs the sweep decided to remove in dry_run mode?** No — dry_run: gone is still pushed! Look: in the loop, `if !dry_run { remove_file }` but `gone.push(hex)` happens regardless of dry_run. Then `forget(&index, &gone)` is called unconditionally at line 140 — `forget` does `fs::remove_file(path)` with no dry_run check! So a **dry run deletes the index entries** for every blob it would have removed (and for unreferenced blobs, since unreferenced blobs are removed regardless of dry_run in accounting). That's a serious bug: dry_run=true, documented as "reports what one would reclaim without removing anything", actually deletes index entries from the store. Consequence: next request treats as miss, refetch — loses cached state and corrupts the "dry run" promise. Severity: red/orange. Lines: sweep.rs:137 (gone.push) and 140 (forget call without dry_run guard), and forget at 249.

Also worse: in dry run, blobs that ARE referenced and within ceiling aren't pushed; only ones it "would remove". Still, it deletes index entries. Red.

6. **Unreferenced blobs removed even in dry run?** No, actual removal is guarded.

7. **`remaining >= self.max_bytes`**: held is computed from candidates sum. Removal condition uses `remaining >= max_bytes` — removes while over. OK. But `held` includes only blobs, not partials or index. Fine — doc says "Bytes of blob the store held".

8. **Sweeper::run holds mutex, but `sweep` is public and called directly by the admin route without the lock** — the admin route bypasses the `running` mutex, so the one-at-a-time promise ("this module's one-at-a-time promise is something the type keeps rather than something every caller remembers") is broken: an admin-triggered sweep can run concurrently with a background sweep. admin.rs:76 calls `app.sweeper.sweep(dry_run)` directly instead of `run()`. That's a real bug — the type's invariant is violated by its own route. Orange.

9. **metrics.rs COUNTERS/values mismatch** — covered in #1.

10. **config.rs: no validation that cache_min_age is... fine. What about cache_min_age zero? min_age zero means sweep can remove anything immediately; operator's choice. Not a defect.

11. **Duration::from_mins/from_hours** — std Duration has these as unstable? Actually `Duration::from_hours` and `from_mins` are unstable in std (feature `duration_consts`... actually `Duration::from_hours` is unstable `duration_constants`). But tests in config.rs already use `Duration::from_mins(2)` and the file presumably compiles in their benchmark environment. Not flaggable — pre-existing pattern in unchanged code? Line 83-84 are new, but line 350-351 pre-existing uses the same. So presumably their toolchain supports it. Skip.

12. **`collect` on index dir vs blob dir**: `referenced` uses `collect` which builds Candidates with metadata — fine.

13. **Symlink handling**: `fs::metadata` follows symlinks; comment says links counted at link size — but `fs::metadata` follows symlinks and returns target size! `fs::symlink_metadata` gives link size. The comment at sweep.rs:160-163 claims "A link is counted at the size of the link and not of whatever it points at", but `fs::metadata` follows the link, so a symlink counts at the target's size. So the comment is wrong and a symlinked store counts target sizes — actually that might be desirable, but the code contradicts its own comment; also `meta.is_dir()` on symlink to dir would recurse. Is this a defect? The stated behavior doesn't hold. Low/medium — could cause the ceiling to be miscounted if a symlink points outside the store (counting bytes not on the volume). Also could loop on symlink cycles (fs::metadata on a symlink loop errors → skipped). Directory symlink cycle: metadata follows → is_dir true → collect recurses infinitely on a cycle. Low. I'd report as blue/yellow: code doesn't match comment; use symlink_metadata. Given it's a claimed behavior that doesn't hold — yellow.

14. **`held` and eviction loop `remaining >= self.max_bytes`**: if max_bytes... fine.

15. **`age_of` flattening future timestamps to 0 age**: a blob with a future mtime gets age 0 → it's the newest, kept. Fine.

16. **`scanned` vs removed blobs also removed in clear_partials not counted in bytes.** Fine.

17. **`forget` deletes index entries for blobs that were purged concurrently** — no.

18. **The `gone` list in dry run also feeds forget — main bug #5.**

19. **routes/mod.rs: sweep route in `untimed` merged into bounded which has TraceLayer and request-id middleware — fine. But note `bounded` routers merged... `bounded.merge(untimed)` — the timeout layer applies to `bounded` before merge? Let me check routes/mod.rs around line 106-140.

Let me read routes/mod.rs fully to check the merge order and whether the timeout applies.
└ 1834 tok · 122.7 tok/s · 29K ctx · 1329ms ttft · 14.9s wall
↳ read_file: read pr/services/proxy/src/routes/mod.rs
└ read_file: read complete
-- reasoning --
Now let me analyze defects.

Key candidates:

1. **`forget` removes index entries for blobs removed only because they're over the ceiling / unreferenced.** Wait — `forget` removes index entries for all `gone` digests, including blobs removed because `remaining >= max_bytes && age >= min_age` (LRU eviction). That's intended per docs: "removing blobs no index entry points at" — the sweep drops stale entries. But there's a race: a blob referenced by index gets removed (LRU), and index entries deleted. Meanwhile a serve in flight: resolve reads index, gets digest, opens blob. Sweep removes blob between resolve and open → open_blob returns None → miss → refetch. OK.

But bigger issue: `forget` removes index entries even when the blob was *not* actually removed! In the non-dry-run path, if `fs::remove_file` fails (line 126), the code still pushes `hex` to `gone` (line 137) and `forget` then deletes index entries pointing at a blob that still exists. Consequence: index entries removed while the blob is still on disk → resolve misses → refetch writes same blob; minor. But more seriously, `removed`/`bytes` counters count blobs that were not removed — inflated metrics, and `remaining` computed wrong. Actually the failure case comment says "usually already gone". But on permission error, index entries get deleted for a live blob. Medium.

2. **Concurrency: `sweep` is called synchronously on the async runtime (blocking I/O) — acknowledged in docs deliberately. Also the on-demand route `reclaim` calls `app.sweeper.sweep(dry_run)` directly, NOT `run()`.** Wait — the Mutex protects one-at-a-time, but `reclaim` in admin.rs:76 calls `app.sweeper.sweep(dry_run)` — the synchronous method that does NOT take the lock! The doc in sweep.rs 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 route calls `sweep()`, bypassing the lock. So a scheduled sweep (via `run()`, which locks) and an on-demand sweep (via `sweep()`, unlocked) can run concurrently, and two on-demand sweeps concurrently. That defeats the mutex. Also a dry-run racing a real sweep is fine-ish, but a real on-demand sweep racing the background one is exactly the documented hazard ("Two of them over one directory would each decide what to remove from a total the other is already changing, and between them they would take the store far below the ceiling either was aiming at"). Also on-demand and background sweeps would each double-count metrics? No, background counts via run, on-demand counts in reclaim.

So: 🔴/🟠 bug at admin.rs:76 — `sweep()` bypasses the `running` mutex; should call `run()` (with a dry-run variant). Definitely a real defect.

3. **Blocking the async runtime**: `sweep()` does synchronous fs walking potentially over 65k dirs + reads; called directly in the async handler `reclaim` on a tokio worker thread. The module doc acknowledges sync walk is a deliberate choice vs tokio::fs, but running it inline in a request handler blocks the executor for the duration of the sweep (could be many seconds/minutes on a large store). The background task also runs it on a worker. This is deliberate per comments... The route being untimed suggests they know it's long. Still blocking the reactor workers starves all requests. It's a known trade-off they documented; maybe not report, or 🟡. Given the review should report defects with a line — the handler blocking the runtime thread while the doc claims only "sweep legitimately takes longer than ten seconds" — I'd call it 🟡 performance. Hmm, it's deliberate design ("The walk is synchronous"). They chose std fs. But running it inside an axum handler without `spawn_blocking` still blocks a worker thread. I'll report as 🟡 performance.

4. **`age_of` flattening**: if `modified()` fails or time is in the future, age = 0 → the blob becomes the oldest candidate, sorted first, and never satisfies `age >= min_age`... wait, age 0 < min_age so it's protected from LRU removal actually — that keeps it, safe. But age 0 means it's sorted first in removal order — combined with the "unreferenced" reason it doesn't matter. For LRU, age 0 protects it. Fine. Actually wait — flatten to zero means a blob whose mtime is in the future (clock skew) is treated as brand-new → protected from eviction, and prioritized... no, it's protected since 0 < min_age. Fine, not a bug.

5. **`clear_partials` deletes files that are actively being written by an in-flight fetch!** `BlobWriter` writes to `incoming/<pid>-<seq>` while the download is in progress. A sweep's `clear_partials` removes *every* file in `incoming` — including temps of fetches currently in flight. The comment claims "A file in `incoming` is a fetch that is not coming back" — false: a fetch in progress has an open temp file there. Removing it: the writer holds the file handle; on Unix, writes continue to the unlinked inode; at commit, `fs::rename(&temp, &target)` will fail with ENOENT → the fetch fails with an error. So a 15-minute sweep kills any in-flight download longer than the sweep's timing... actually any in-flight download at sweep time. Consequence: concurrent downloads fail. Also the writer's Drop tries to remove temp (already gone, logs warn). So this is a real bug: 🔴 or 🟠. There's no min-age check on partials, no pid exclusion (own pid files are in-flight). 🔴 bug at sweep.rs:232 (clear_partials removes in-flight writes). Severity: high — concurrent fetch failure. I'd say 🟠 or 🔴. Given proxy's whole job is downloads and every download in flight gets broken, but they do fail gracefully (client gets error, refetches) — 🟠.

6. **`Reclaimed.bytes` counts sizes of files whose removal failed** — same as #1. Also `remaining` accounting: when removal fails, the code still decrements `remaining`, so the sweep may under-remove. Part of #1.

7. **The `hex` taken from `file_name()`**: for blobs under `blobs/sha256/`, file names are digests. But `collect` on BLOBS only collects files — fine. In `index` the `referenced` collect reads files. But `forget`'s index paths come from index dir. Fine.

However: in `sweep`, `candidate.path.file_name()` for a blob path — could a blob file name not be a hex digest? E.g., stray files. If not in index, it's removed — deleting an arbitrary file under blobs/sha256 that isn't a digest... that's intended cleanup I guess.

8. **The LRU eviction condition `remaining >= self.max_bytes`**: if `max_bytes` config equals... fine. But note: blobs that fail the min-age test are skipped but the loop continues to newer ones (also younger, so all skip). Fine. But `remaining >= max_bytes` means a store exactly at ceiling: remaining == max_bytes triggers removal — ok.

9. **Metrics counter mismatch**: COUNTERS order is blobs_removed then bytes_reclaimed (entries at index 4,5: blobs_removed first, then bytes), but `values()` returns bytes then blobs (lines 94-95: sweep_bytes_reclaimed first, then sweep_blobs_removed). So the rendered names/values are swapped: `cairn_proxy_sweep_blobs_removed_total` gets the byte count and vice versa. That's a definite bug! metrics.rs:88-97 vs COUNTERS order 51-57. 🔴 (metrics corruption — alerts on wrong values). Line: values() at 94-95. Report at metrics.rs:94.

10. **`record_sweep` in admin counts even on error?** no.

11. **On-demand sweep also counts metrics but with `dry_run` guard — but the background task also records; the on-demand one double counts? No, it's an actual sweep, correct to count.

12. **`held` counts only blobs; index files and partials not counted toward ceiling — fine, doc says "Bytes of blob".

13. **`duration_since` with future mtime → age 0; combined with `forget`... no.

14. **`scanned` includes index? No, only blob candidates. Fine.

15. **`SweepQuery.dry_run` uses `#[serde(default)] bool`** — `?dry_run=true` works, `?dry_run=false` works. Fine.

16. **`sweep` route outside timeout but also `run()` lock: an on-demand sweep during a long background sweep — since on-demand doesn't lock, they run concurrently (defect #2).

17. **`forget` also removes index entries for blobs removed due to LRU while a *concurrent fetch* just wrote the index entry after `referenced` snapshot** — TOCTOU: fetch completes: blob committed, index linked (both after sweep's referenced() snapshot). Sweep sees blob not in index → removes blob AND forget removes the fresh index entry → cache entry lost; next request refetches. Only a wasted refetch, plus for a concurrently-downloading artifact... acceptable-ish. But combined with the in-flight partial deletion (#5), sweep is hostile to concurrent fetches generally. The index-entry race is minor.

Actually worse: sequence — fetch downloads blob (committed), sweep's collect happens before blob appears; then link writes index. Not an issue since blob not in candidates.

Reverse race: sweep decides to remove blob X (unreferenced), fetch (serve path miss) starts refetching X, commits new blob at same path, then sweep's remove_file deletes the just-committed blob, then... next request misses. Wasted work only.

18. **`config`: `cache_min_age` has no validation of zero** — min_age zero means LRU can evict immediately, which is a legit config choice. Not a bug.

19. **`.env.example` CAIRN_CACHE_MAX_BYTES=34359738368 = 32 GiB ✓.

20. **Duration::from_hours/from_mins** — these exist in std? `Duration::from_hours` and `Duration::from_mins` are unstable (`duration_consts`? actually `Duration::from_hours` is nightly `duration_constants` feature). Hmm — in stable Rust, `Duration::from_hours` doesn't exist as a const... Actually there is `Duration::from_hours` unstable since 1.83? Let me think: `Duration::from_secs_f32`... `Duration::from_hours` — I recall `duration_constants` feature providing `from_hours`, `from_mins` etc., still unstable. But the existing test at config.rs:350 uses `Duration::from_mins(2)` in the pre-existing code? The test file exists already (test code referenced in diff context is pre-existing? The tests section — is it pre-existing? The diff doesn't show config tests being added, but `Duration::from_mins` appears in the test at line 350 which is presumably pre-existing (test not in diff). So from_mins/from_hours presumably available in this codebase's toolchain (maybe nightly or newer stable stabilized). Can't verify; skip.

21. **`routes/mod.rs`: removed the comment about cache route timeout but kept behavior — fine.

22. **Sweep route doesn't require the token? It calls authorise — fine. But wait: `bounded` router has TimeoutLayer, sweep is in untimed — intended.

23. **`admin.rs` sweep: `reclaim` is sync fn calling blocking sweep inside async handler — #3.

24. **`main.rs` spawn_sweeps: task not part of shutdown — documented deliberate.

25. **`metrics.rs` doc comment "Keeping the two side by side" — fine.

26. In sweep `remove` decision: blobs referenced by index but store over ceiling with age >= min_age are removed, and then `forget` deletes their index entries. Good.

But unreferenced blobs removal ignores min_age entirely — including a blob that was just fetched by a *concurrent* request whose index link hasn't been written yet (link happens after commit). Sweep: referenced() snapshot → collect → decide. A blob committed milliseconds before, index link written milliseconds after `referenced()` ran → treated unreferenced → deleted immediately, and its (fresh) index entry then deleted by `forget`. So a just-cached artifact is evicted while the next pipeline step asks for it, defeating the very grace period CAIRN_CACHE_MIN_AGE promises ("a package one job in a pipeline fetched is still there for the next"). This is the TOCTOU between commit and link. The min_age grace exists precisely for that, and the unreferenced path bypasses it by design (comment acknowledges: "Age does not enter into the first"). But the design assumption "a blob no index entry names cannot be reached" is wrong during the commit→link window: the blob IS about to be reachable. Combined with the in-flight partial deletion, sweeps break concurrent fetches. I'd report the commit/link TOCTOU as 🟠 (window is small: between commit and link — actually link happens right after commit in the serve path, window is milliseconds, but sweep reading index happens after collect... order: clear_partials, referenced, collect. A blob committed after referenced() snapshot but before its link → in candidates, not in index → removed. Window = time between collect and link. Small but real under load). Maybe 🟡.

Actually wait — worse: sweep order is clear_partials → referenced → collect(blobs). A fetch in flight: temp file in incoming deleted (#5) → rename fails → fetch errors. So #5 covers the in-flight case. The commit→link window is ms. I'll report it 🟡 maybe. Hmm, be careful not to pad. The clear_partials bug (#5) is the big one.

27. **`forget` deletes index entries for digests that failed to be removed (remove_file error)** — as noted in #1. Report as one bug: sweep.rs:126-137: on remove failure the blob is still counted as removed and its index entries deleted. Also affects dry_run? In dry_run no removal attempted, entries "gone" not removed... wait, `forget(&index, &gone)` is called even in dry_run! In dry_run, nothing was removed, but `gone` contains all the candidates that *would* be removed, and `forget` deletes their index entries unconditionally — `fs::remove_file(path)` in forget has no dry_run guard! So **a dry run actually deletes index entries** for blobs it claims it would reclaim. That's a real bug: the doc says "?dry_run=true reports what one would reclaim without removing anything" — but it removes index files. Consequence: next request for those coordinates misses and refetches (blob still there → refetch renames over). So dry run mutates state, contradicting the promise. 🔴/🟠 at sweep.rs:140 (or 249). Definitely report: 🟠 bug sweep.rs:140: `forget` runs on dry runs, deleting index entries.

Also, dry-run's `removed`/`bytes` get recorded? No, metrics skipped. But log says "swept". Fine.

28. **`referenced` uses `collect` which uses `fs::metadata` (follows symlinks) — fine.

29. **BLOBS const "blobs/sha256" joined — fine.

30. **`held` vs ceiling: index files size not counted, fine.

31. **`values()` order bug — confirmed.

Let me double check metrics bug: COUNTERS[4] = "cairn_proxy_sweep_blobs_removed_total", COUNTERS[5] = "cairn_proxy_sweep_bytes_reclaimed_total". values()[4] = sweep_bytes_reclaimed, values()[5] = sweep_blobs_removed. zip pairs: index 4 name (blobs_removed) with value bytes → yes swapped. Definite bug. Severity: 🟠 (wrong metrics, alerts fire on wrong signal).

32. **`admin.rs` `sweep` handler: `Query<SweepQuery>` with private field `dry_run` — Deserialize works with private fields? serde derives work on private fields, yes.

33. **On-demand sweep bypasses lock (defect #2).** admin.rs:76 calls `app.sweeper.sweep(dry_run)` instead of a locked variant. Two concurrent POSTs, or POST + timer, run concurrently → both compute from same `held`, each removes → store driven far below ceiling; also double counting bytes in metrics. 🔴 or 🟠. The mutex exists precisely for this; the route ignores it. 🟠/🔴. I'll say 🟠.

Actually, wait — should the route call `run()`? `run()` is non-dry. They'd need a dry-run-aware locked method. Either way, current code races. Report at admin.rs:76.

34. **Blocking async runtime (#3)**: sweep.rs is sync by design, but calling it directly in the handler thread blocks a tokio worker for the whole walk (potentially minutes over 65k dirs + reading every index file). `run()` from the spawned task also blocks a worker. The module doc justifies sync walk but doesn't mention spawn_blocking. This starves other requests including cache serves. 🟡 performance. Line: admin.rs:76 or sweep.rs:90. I'll report 🟡 at sweep.rs:90 / admin.rs:76. Hmm — maybe fold into #33? They're distinct: one is correctness of mutual exclusion, the other is blocking. I'll report blocking at admin.rs:76 too... One line each.

Actually for the background task in main.rs:116 `app.sweeper.run().await` — run() is async but sweep() inside is fully synchronous blocking — so the "await" on the mutex is async but the sweep blocks the worker thread. Worth a 🟡.

35. **`clear_partials` also removes `BlobWriter` temp files of the *current* proxy's own in-flight fetches** — that's #5. Also note: delete fails on Windows if open, but on Unix succeeds. The platform is likely Linux. Report.

36. **`config` min_age has no sanity check but fine.

37. **`main.rs` spawn_sweeps first tick fires immediately!** tokio::interval: "An interval will tick indefinitely. At any time, the Interval value can be dropped. ... The first tick completes immediately". Yes! `tokio::time::interval` first tick completes *immediately*, not after the period. The doc comment in main.rs claims "The first tick is one interval away" — that's wrong. So a sweep runs immediately at startup. Consequence: contradicts stated intent ("keeps a proxy that has only just started from sweeping a cache it has not begun to fill") — actually sweeping an empty cache is harmless... but with the clear_partials bug, a sweep right at startup still deletes in-flight fetches? At startup nothing in flight. But combined with interval behavior: first sweep at t=0, then every interval. The real consequence: the doc's claim is false and the sweep races with the first fetches on a restarting proxy — a proxy that just started with a populated store will immediately delete unreferenced blobs (fine) — hmm and in-flight fetches from... at startup there are none yet, but clients may immediately hit it. Actually restart with clients hammering: startup sweep + concurrent fetch → partial deletion bug triggers. So the immediate tick makes the clear_partials race much more likely. Report 🟡 bug main.rs:108: first tick of `interval` fires immediately, contradicting the documented intent.

Wait, verify: tokio docs for `interval`: "The first tick completes immediately". Yes, confirmed — well-known. So it's a real behavioral defect vs documented intent. Severity 🟡 (or 🟠 combined). I'll say 🟡.

38. **`Reclaimed.held` sums candidates including... fine.

39. **`forget` in dry run — main bug #27.

40. **Docs: operations.md mentions `cairn_proxy_sweep_bytes_reclaimed_total` — matches. architecture.md says sweep removes "blobs nothing points at and then the oldest" — code removes unreferenced AND oldest-over-ceiling in one pass; fine.

41. **`.env.example` CAIRN_CACHE_MIN_AGE etc fine.

42. One more: `sweep` counts `bytes += candidate.size` even when remove_file failed (#1). Fold into one finding? The index-deletion-on-failed-removal is the sharp edge. Let me phrase: sweep.rs:126-137: when `fs::remove_file` fails, the blob is still counted in `removed`/`bytes` and passed to `forget`, which deletes index entries pointing at a blob that still exists → future resolves miss and refetch (duplicate work), and metrics overstate reclamation. 🟡.

Also the dry-run `forget` bug overlaps: in dry run nothing fails, forget deletes entries for all would-be-removed. Both stem from `forget` being unguarded. Maybe report dry-run one and the failed-removal one separately — different lines (140 vs 126-137).

43. **`routes/mod.rs` line 131: sweep route in untimed router — but also merge: bounded has TimeoutLayer applied at its layer; merging routers... In axum, `bounded.merge(untimed)` — layers applied to `bounded` before merge only apply to routes in bounded. Correct pattern. Fine.

44. **admin.rs `sweep` handler does not check that the store/root exists — fine.

45. **`Sweeper::new(&cfg)` — fine.

46. `#[must_use]` on sweep — fine.

47. **Query `dry_run` parsing: `?dry_run=true` — serde bool parses "true". Fine.

Also check: does the sweep route get a request timeout... intentional.

48. **`referenced` collect on INDEX dir: index entry files include any file; but index dir also may contain... fine.

49. **`collect` follows symlinked dirs (fs::metadata follows symlinks; is_dir true for symlink-to-dir) → potential infinite recursion on a cyclic symlink? "A store moved between volumes often has blobs linked into it" — symlink cycles would recurse infinitely → stack overflow / hang. Hmm, the comment mentions links; `fs::metadata` follows symlinks, so a symlinked directory loop = infinite recursion. Edge case; maybe 🔵. The comment says blobs "linked into it rather than copied" — hard links probably (counted at size of the link — actually for hard links meta.len() is the full size, not link size; comment is confused). Eh, skip or 🔵. I'll skip to avoid padding; actually symlink cycle → stack overflow crash of the sweep task (panics the background task? recursion overflow aborts process). It's a real hazard given they explicitly support linked stores. I'll include as 🔵 at sweep.rs:167.

Hmm, careful about padding. The instruction: report concrete defects. The symlink cycle is concrete but speculative. I'll include as 🔵.

50. `age_of` flatten to 0: a blob with future mtime gets age 0 → protected from LRU eviction, fine; but sorted oldest-first → for unreferenced removal, order doesn't matter. Not a bug.

51. `scanned` u64::try_from unwrap_or(u64::MAX) fine.

52. `held` doesn't include partials in ceiling check — fine, partials get deleted anyway.

53. **`spawn_sweeps` task: `app.metrics.record_sweep` after run — includes dry? no, run is non-dry. fine.

54. **On-demand sweep via route does not hold the mutex but ALSO — the background loop holds the mutex during sweep; since sweep is blocking-sync, mutex is held across blocking code; an on-demand POST doesn't wait at all (#33). Consistent.

Now also check `error.rs` for into_response_with — not needed.

Let me also verify `RequestId` extractor and `Shared` import exist in routes/mod.rs — line 23 imports `RequestId, Shared` from routes; mod.rs defines them presumably. Fine.

Check Cargo.toml: tokio "sync" and "time" added — needed for Mutex and interval. Fine.

One more: `main.rs` doc says sweep "Not part of the graceful shutdown" — fine.

Check `.env.example` value 34359738368 = 32*2^30 ✓.

Severity assignment:
- 🔴 metrics name/value mismatch (metrics.rs:94-95): wrong data on the wire, operator alerts on wrong counter. Critical? It silently corrupts monitoring. I'd say 🟠 honestly — high. The format's critical = e.g. data loss/security. Metrics swap → every alert/dashboard wrong from day one. I'll go 🟠.
- 🔴 clear_partials deletes in-flight temp files → every concurrent download fails. 🟠 or 🔴. Breaking every in-flight download on each sweep = high impact, but recoverable (client retries). 🟠.
- 🟠 dry-run deletes index entries (sweep.rs:140 / forget at 249-257 missing dry_run guard). Violates documented dry-run promise. 🟠.
- 🟠 admin.rs:76 bypasses mutex → concurrent sweeps drive store far below ceiling, double-counted metrics. 🟠.
- 🟡 sweep.rs:126-137: failed removal still counted and index entries deleted for live blob.
- 🟡 main.rs:108: interval first tick immediate, contradicts doc.
- 🟡 blocking the runtime: admin.rs:76 / sweep.rs:90 — synchronous multi-minute walk on a tokio worker inside a request handler stalls all other requests. 🟡.
- 🔵 collect symlink cycle recursion.

Also TOCTOU commit→link window evicting just-fetched blob — arguably part of design (comment explicitly argues age doesn't matter for unreferenced). The window between BlobWriter::commit and store.link is where the blob is unreferenced; a sweep in that window deletes the fresh blob and then `forget`... wait, forget only deletes entries in the snapshot index — the fresh link wasn't in the snapshot, so its entry survives, pointing at a deleted blob → stale entry, one refetch. So consequence is a wasted refetch; window milliseconds. Skip.

Order by severity: 🟠 items first? Policy doesn't specify ordering but sensible to order by severity.

Line numbers:
- metrics.rs:94 (values() order) — could also point at 33. Use 94.
- sweep.rs:232 (clear_partials remove) — the defect is clear_partials removing all files regardless of age/ownership; line 232 or 224. Use 232.
- sweep.rs:140 (forget call without dry_run guard) or forget at 249. The fix is at 140 (skip forget when dry_run) or in forget. Point at 140.
- admin.rs:76 (sweep bypasses lock).
- sweep.rs:137 (gone.push even on failure) — point at 126 area; use 137.
- main.rs:108 (interval first tick).
- admin.rs:76 blocking — same line as mutex bug; use sweep.rs:90 for blocking (sweep is sync, called from async context). Point sweep.rs:90.
- sweep.rs:167-168 symlink recursion 🔵.

Write-up format: one line each, exact form.
Reviewing the diff against the checked-out code. The sweep feature touches `sweep.rs`, `admin.rs`, `metrics.rs`, `main.rs`, `config.rs`, and the router; I read all of them plus `store.rs` (the layout and writer lifecycle the sweep depends on). Findings:

🟠 `bug` services/proxy/src/metrics.rs:94: `values()` returns `sweep_bytes_reclaimed` before `sweep_blobs_removed`, but `COUNTERS` (lines 51-57) lists `cairn_proxy_sweep_blobs_removed_total` first — `render()` zips them in order, so every scrape publishes the byte count under the blobs-removed name and vice versa; any alert or dashboard built on the documented counter names reads the wrong quantity.

🟠 `bug` services/proxy/src/sweep.rs:232: `clear_partials` unlinks every file in `incoming` with no age or ownership check, but `BlobStore::writer` (store.rs:171-180) puts the temp file of every *in-flight* fetch there — a sweep concurrent with any active download unlinks its temp, so the fetch's `commit` rename fails (store.rs:259) and the download errors out; the "a file in `incoming` is a fetch that is not coming back" premise is false for live writers, and `CAIRN_CACHE_MIN_AGE` is not honoured here either.

🟠 `bug` services/proxy/src/sweep.rs:140: `forget(&index, &gone)` runs unconditionally, including on a dry run — nothing in `sweep` removes blobs during a dry run, yet `gone` holds every candidate that *would* be removed, so `?dry_run=true` (documented as reporting "without removing anything") actually deletes the index entries naming those blobs, turning a read-only query into a destructive one.

🟠 `bug` services/proxy/src/routes/admin.rs:76: the on-demand route calls `app.sweeper.sweep(dry_run)` directly, which does not take the `running` mutex (sweep.rs:83) that exists precisely so two sweeps cannot each compute from a total the other is changing — a `POST /v1/admin/cache/sweep` racing the interval sweep (or a second POST) makes both evict against the same `held`, driving the store far below the ceiling and double-counting `removed`/`bytes` in the metrics.

🟡 `bug` services/proxy/src/sweep.rs:137: when `fs::remove_file` fails (line 126), the blob is still pushed to `gone` and counted in `removed`/`bytes`, so `forget` deletes index entries pointing at a blob that still exists (next resolve misses and refetches) and the sweep metrics overstate what was reclaimed.

🟡 `bug` services/proxy/src/main.rs:108: the doc comment claims "the first tick is one interval away", but `tokio::time::interval`'s first tick completes immediately, so a sweep runs at startup — harmless on an empty store, but on a restart with a populated store and clients already hitting it, it makes the in-flight-partial deletion and the commit→link eviction window in `sweep.rs` fire on the very first requests rather than one interval in.

🟡 `bug` services/proxy/src/routes/admin.rs:76: `sweep()` is fully synchronous (the module doc at sweep.rs:14-18 commits to stdlib `fs`), and the handler runs it inline on a tokio worker thread — a walk over tens of thousands of directories plus a read of every index entry can block a worker for minutes, starving the very cache serves the untimed route exists to protect; it needs `spawn_blocking`.

🔵 `bug` services/proxy/src/sweep.rs:168: `collect` recurses through symlinked directories (`fs::metadata` follows symlinks, `is_dir()` is true for a dir symlink) with no cycle check, despite the comment at lines 160-163 explicitly contemplating a store populated by links — a symlink loop under `blobs/` recurses until the stack overflows, taking down the process.
└ 6877 tok · 116.0 tok/s · 30K ctx · 1320ms ttft · 59.3s wall