sandbox:read-only (macOS Seatbelt)
-- reasoning --
Let me look at the actual checked-out code under pr/ to verify details: store.rs (IndexEntry, BlobStore layout), digest.rs (Digest::parse, hex), config.rs (parse_duration, Duration::from_hours/from_mins - these don't exist in std! `Duration::from_hours` and `Duration::from_mins` are unstable nightly features? Actually `Duration::from_hours` was stabilized in... `Duration::from_hours` is still unstable as of recent Rust? Let me check: `duration constructors` like `from_hours` are unstable (feature `duration_constructors`). `from_mins` likewise unstable. That's a compile error on stable. Need to verify by reading the file in pr/.

Also check: sweep removes index entries for unreferenced blobs via `forget`, but in dry_run, `gone` still collects hexes and `forget` runs regardless of dry_run — deleting index entries even in dry run! Look: `sweep(&self, dry_run)` — `gone.push(hex.to_owned())` happens regardless of dry_run, and `forget(&index, &gone)` is called unconditionally at the end. So a dry run deletes index entries without removing blobs. That's a real bug: dry_run still mutates the store (removes stale index entries). Consequence: blobs stay, index entries gone → lookups miss → refetch. Actually for unreferenced blobs (nothing in index), forget does nothing. forget only removes entries for hexes in index map. If a blob is removed because over-ceiling but still referenced, index entry removed → next request refetches (fine, blob gone anyway in real sweep). In dry run, blob is NOT removed but index entry IS removed → lookups now miss and refetch even though blob present. Bug.

Another: `remaining >= self.max_bytes` uses >= — if store is exactly at ceiling, it removes oldest blobs... condition: remove if remaining >= max_bytes. When held == max_bytes exactly, it will remove blobs (those older than min_age). Probably intended "over ceiling", minor. Actually the doc says "back within it" - remaining >= max means at ceiling it removes until remaining < max. Slightly aggressive but maybe intended. Borderline.

Also `clear_partials` in sweep runs on INCOMING unconditionally — but a fetch in progress writes to incoming! A fetch that is currently in progress has a partial file in incoming, and the sweep deletes it mid-write. On Unix, deleting an open file is fine (fd stays valid), the write completes and rename... wait, does BlobWriter rename from incoming to blobs dir? If the file is unlinked while still open, the rename would fail (source gone), and the fetch fails. Also the doc says "A file in `incoming` is a fetch that is not coming back" — but that's wrong for concurrent in-progress fetches. There's a min_age check missing for partials — cache_min_age should protect in-flight fetches. This is a real bug: sweep deletes in-progress partial writes. Need to check store.rs BlobWriter to confirm it writes to incoming. Let me read pr files.

Also main.rs: `spawn_sweeps` spawns without... fine.

metrics order: COUNTERS array order: sweep_blobs_removed_total then sweep_bytes_reclaimed_total; values() pushes bytes then blobs. Mismatch! COUNTERS has blobs_removed first (index 4), bytes_reclaimed second (index 5). values() array: index 4 = sweep_bytes_reclaimed, index 5 = sweep_blobs_removed. So the render pairs name "cairn_proxy_sweep_blobs_removed_total" with the bytes value and "sweep_bytes_reclaimed_total" with the blobs count. That's exactly the bug the comment in metrics.rs warns about. Real defect — metrics swapped. Line: values() in metrics.rs, the two lines added. In the diff, values added:
```
self.sweep_bytes_reclaimed.load(...),
self.sweep_blobs_removed.load(...),
```
while COUNTERS:
```
"cairn_proxy_sweep_blobs_removed_total" ...
"cairn_proxy_sweep_bytes_reclaimed_total" ...
```
Yes, swapped. High severity bug.

config.rs: `Duration::from_hours(1)` and `Duration::from_mins(15)` — unstable. Need to check the actual file in pr/ to see. Also check whether the repo builds on stable... can't run commands. Read config.rs.

Also `Sweeper::sweep` is called from admin route via `app.sweeper.sweep(dry_run)` — synchronous, blocking the async runtime: route calls `reclaim(&app, ...)` which calls `app.sweeper.sweep(dry_run)` synchronously inside async handler, blocking a tokio worker thread for potentially a long walk (65k dirs). The module doc says the walk is synchronous on purpose, but calling it directly in an async handler without spawn_blocking blocks the runtime thread. Also the interval sweeper calls `app.sweeper.run().await` which also calls the synchronous `self.sweep(false)` directly in the async task — blocking. Hmm, run() acquires the async mutex then does blocking fs work on the runtime thread. That's a performance defect: blocks tokio worker. Medium.

Also the lock: route calls `sweep()` directly, bypassing the Mutex — so on-demand sweep doesn't honor one-at-a-time promise! `run()` locks, but the admin route calls `sweep(dry_run)` directly which doesn't lock. So two concurrent sweeps possible: interval one and manual one. That contradicts the Mutex doc "Held for the whole of a sweep, so this module's one-at-a-time promise". Real bug, high. Line: admin.rs `let reclaimed = app.sweeper.sweep(dry_run);` — bypasses the mutex.

Let me check digest.rs for `Digest::parse` and `.hex()`, store.rs for IndexEntry and layout, and config.rs for from_hours.

Also check `Duration::from_mins` — actually the unstable constructors are `from_hours`, `from_mins` (yes, `duration_constructors` unstable). If the crate targets stable, compile error. Severity critical/red (build failure). But maybe there's a nightly toolchain... can't verify. It's still a defect: unstable API. Report as red bug at config.rs lines.

Let me read the pr files to pinline numbers.
I'll read the checked-out files to verify details and pin line numbers.
└ 1415 tok · 141.5 tok/s · 12K ctx · 1252ms ttft · 10.0s wall
↳ read_file: read pr/services/proxy/src/config.rs
└ read_file: read complete
↳ read_file: read pr/services/proxy/src/store.rs
└ read_file: read complete
↳ read_file: read pr/services/proxy/src/digest.rs
└ read_file: read complete
auto-compress is on at 85% but the context window of "z-ai/glm-5.3" 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 things to verify:

1. `Duration::from_hours` and `Duration::from_mins` — are these stable Rust? `Duration::from_mins` and `Duration::from_hours`... In std, there are `Duration::from_secs`, `from_millis`, `from_micros`, `from_nanos`. `from_mins` and `from_hours` were added as unstable? Actually there was an RFC... Let me think. `Duration::from_mins` and `Duration::from_hours` — I believe there was a PR adding these but I don't think they're stable. Hmm, actually there's `Duration::try_from_secs_f64` etc. Let me check: as of Rust 1.75-ish, `Duration::from_mins` doesn't exist. Actually there was an RFC for `Duration::new`-like const constructors. I recall `std::time::Duration` has `from_secs`, `from_millis`, `from_micros`, `from_nanos`. There's no stable `from_mins` or `from_hours`. Wait — actually the config.rs tests at line 350-352 already use `Duration::from_mins(2)` and `from_hours(1)`, and those are pre-existing (tests not in the diff). Hmm, the diff shows the tests existed before (the test file lines 347-364 are not part of the diff hunk... actually the diff for config.rs doesn't touch tests). So `from_mins`/`from_hours` presumably compile in this codebase — maybe they exist. Actually I now recall: `Duration::from_mins` and `Duration::from_hours` were added in Rust 1.91? Hmm. There was a stabilized addition... Let me think. There was `Duration::as_secs_f64`, `mul_f64`, etc. I recall discussions (rust-lang/rust#118839?) adding `Duration::from_mins`. Actually yes — I believe `Duration::from_mins` and `from_hours` were stabilized recently (Rust 1.91, 2025?). Given the pre-existing tests use them and the repo presumably builds, I shouldn't report that.

Let me check whether I can compile. The task says I cannot run commands? "You cannot write, edit, or run commands" — but I have run_bash tool. Hmm, the user message says "You cannot write, edit, or run commands". But the system gives me tools. The instruction is part of the review prompt; the sandbox is read-only mode. I should not run cargo build anyway (network denied, would fail). I'll rely on reading.

Actually wait — is `Duration::from_mins` stable? I remember tracking: `duration_consts` etc. Hmm, `Duration::from_hours`... I genuinely am unsure. Let me check the repo — maybe there's a helper. Search for "from_hours" in pr/.

2. The main functional bug candidate: the sweep route. `admin::sweep` handler calls `reclaim` which is synchronous, calling `app.sweeper.sweep(dry_run)` — a blocking, potentially long filesystem walk executed directly on the async runtime thread (in an axum handler). The sweep.rs doc explicitly says the walk is synchronous and tokio::fs would be costly. But running a synchronous multi-minute walk inside an async handler blocks a runtime worker thread. For the background task in main.rs, `app.sweeper.run().await` also calls `self.sweep(false)` synchronously inside the async task — blocking the tokio worker. The module doc says "One pass of standard-library calls costs less than the scheduling would" — but they never `spawn_blocking`. That's a real defect: a long synchronous filesystem walk on the async runtime starves other tasks. For the interval sweep in main.rs it blocks a worker thread of the multi-thread runtime — still bad but less so; for the admin route it's inside a request handler. The routes/mod.rs comment even acknowledges "a sweep of a large store legitimately takes longer than ten seconds" — yet it runs on the runtime. This is a legitimate finding (performance/correctness). Severity: medium-high. The blocking sweep in the axum handler blocks the tokio worker thread; with many workers maybe tolerable but it can stall healthz probes etc. I'd report as `performance` orange or yellow.

Also `sweep()` is `&self` and not taking the mutex for the HTTP route — the doc says "One sweep at a time... running: Mutex". `run()` takes the lock and awaits; `sweep(dry_run)` called from admin route does NOT take the lock! `reclaim` calls `app.sweeper.sweep(dry_run)` directly, bypassing the Mutex. So the admin route can run concurrently with the background sweep — violating the module's one-at-a-time promise, and two concurrent sweeps over one directory would both decide from totals the other is changing. That's a concrete defect: `admin.rs` line where `app.sweeper.sweep(dry_run)` is called, and the Mutex exists but is only used in `run()`. Wait — but `sweep` is a pub method taking `&self`, and the lock is in `run`. The doc comment on `running` 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 `sweep()` (pub) doesn't acquire it. So the admin route bypasses mutual exclusion. Definitely a bug. Severity: orange (concurrent sweeps can delete based on stale totals; dry-run also concurrent with real sweep). Line: pr/services/proxy/src/routes/admin.rs, need line number.

3. `clear_partials` in dry_run mode: in dry run, it doesn't remove, but still counts `removed += 1` — wait, look: if `!dry_run` and removal fails → continue (skip count). If dry_run, skip the removal block, count += 1. That's correct for dry-run counting.

But bigger issue: `clear_partials` deletes ALL files in `incoming` unconditionally — including in-flight fetches! A concurrent fetch currently writing a partial in `incoming` gets its temp file deleted mid-write. BlobWriter continues writing to the (now unlinked) fd; at commit time, `fs::rename(&temp, &target)` fails with NotFound → the fetch fails. Worse: the sweep's `forget` logic aside, the in-flight fetch will fail and the error surfaces as a fetch failure. So a sweep running while a download is in progress deletes the active temp file, breaking the download. The doc claims "A file in `incoming` is a fetch that is not coming back" — false: a file in incoming is *also* a fetch that is currently in progress. The sweep has no age check on partials (min_age not applied to incoming). That's a real defect: every interval (15m default), any fetch in progress longer than... no age check at all — any in-progress fetch's partial is deleted. Actually timing: sweep walks `incoming` and removes every file. Any download in flight at that moment gets unlinked. On Linux the fd remains valid, writes continue to the unlinked inode, and rename fails at commit → the download errors. With min_age of 1h the fix would be to only remove partials older than min_age. The sweep doesn't use min_age for partials. High severity: periodic (every 15 min) background sweeps will randomly fail in-flight downloads. That's a strong finding. Line: sweep.rs `clear_partials` — the `fs::remove_file(entry.path())` line.

Also, note the failure isn't even logged well — the fetch would fail with a NotFound on rename.

4. `referenced` and index parse: `collect` on INDEX dir collects files; entries parse. `forget(&index, &gone)` removes index entries for removed digests — but `gone` is pushed even in `dry_run` mode! In dry_run, `gone.push(hex.to_owned())` still happens, and then `forget` is called unconditionally — deleting index entries even during a dry run! Look:

```rust
if !dry_run {
    if let Err(error) = fs::remove_file(&candidate.path) { ... }
}
remaining = ...; bytes += ...; removed += 1;
gone.push(hex.to_owned());
...
forget(&index, &gone);
```

`forget` is called outside any dry_run check — it does `fs::remove_file(path)` unconditionally. So a `?dry_run=true` request, which promises "reports what one would reclaim without removing anything", actually deletes index entries for every blob it would remove. That breaks the serve path? Actually resolve treats missing index entry as a miss → refetch. But the whole point of dry run is no removal. Also removes entries for blobs that still exist — causing cache misses and refetches. That's a critical/high bug: dry run mutates state. Also in dry run, `removed`/`bytes` counted as if removed — fine for reporting.

Wait, double-check: is `forget` skipped in dry_run? Reading the diff again:

```rust
        forget(&index, &gone);

        Reclaimed { ... }
```

No dry_run guard. Confirmed. And `gone` accumulates in both modes. So `?dry_run=true` deletes index entries pointing at blobs that remain on disk. The docs say dry run "reports what one would reclaim without removing anything." High severity — `bug` orange, in sweep.rs at `forget(&index, &gone);` line.

Also: in non-dry-run mode, if `fs::remove_file` fails (e.g., concurrent purge), the code still counts the blob as removed, adds size to `bytes`, and adds to `gone` → `forget` deletes index entries for a blob that still exists on disk. Minor: stale-but-deleted index while blob exists → miss → refetch, harmless-ish. But also, `forget` in the error path deletes index entries for a blob that wasn't removed — again just extra refetch. Low.

5. `collect` recursion with symlinks: `fs::metadata` follows symlinks; a symlink to a directory → `meta.is_dir()` true → recurse; a symlink loop would infinitely recurse. The doc comment mentions links counted at link size — but `fs::metadata` follows the link and gives target size, not link size! `fs::symlink_metadata` gives the link's size. The comment says "A link is counted at the size of the link and not of whatever it points at" but the code uses `fs::metadata` which follows symlinks and reports the target's size. So the comment is wrong relative to code. Consequence: hardlinked blobs (the scenario the comment describes — "blobs linked into it") are counted at full size (hard links don't differ with metadata anyway — for hardlinks, `len` is file size regardless; the comment about "size of the link" suggests symlinks, where metadata follows). Actually for hard links, fs::metadata gives the file size, same as the bytes. The comment is about hard links ("blobs linked into it") — for hard links, size counted is the file size, and the store IS answerable for those bytes. So the comment "counted at the size of the link" is odd. Whatever — is there a real defect? Symlink to a large file elsewhere: metadata follows it, counts target's size, and remove_file removes the symlink... fine-ish. Symlink loop → infinite recursion → stack overflow. Marginal. Also symlink to a directory → recursion through it, deleting files outside the blob dir. But who creates symlinks there? Low value. Maybe skip or low.

6. Race between sweep and serve: sweep removes a blob based on `remaining >= max_bytes && age >= min_age`, but a blob may be referenced by index and actively in use (being served right now). Deleting a file being served: on Unix, open fd keeps it alive, so serving continues fine. OK.

7. Race: fetch commits blob, then `store.link` writes index entry. Sweep order: partials, then read index (`referenced`), then collect blobs, then remove unreferenced. A blob committed between `referenced()` and `collect()` — the blob isn't in the index snapshot, so `!index.contains_key(hex)` → removed immediately after commit! Timeline: fetcher commits blob at T1, writes index at T2. Sweeper reads index at T0 < T1, walks blobs at T1.5 → sees new blob, not in index snapshot → deletes it. Then fetcher writes index entry pointing at a deleted blob. Serve path: open_blob → NotFound → treated as miss → refetch. Self-healing, but the sweep just deleted a freshly fetched blob — with the "age does not enter into the first" rationale ("a blob no index entry names cannot be reached however new it is"). But there's a window where the blob IS about to be reachable. The consequence is just a refetch — cache thrash, not corruption. This is inherent TOCTOU; the design accepts it ("costs a single refetch"). Given the doc explicitly acknowledges stale entries cost a refetch, this race is arguably accepted. But the deletion of a just-committed blob wastes the fetch and, importantly, then the index entry is written after deletion, and `forget` won't clean it (sweep already done). Not a big deal. Also the reverse: sweep deletes blob while fetch is committing → rename overwrites fine.

Hmm, but consider: sweep deletes blob (unreferenced in snapshot), fetcher then writes index entry → stale entry. Next request: resolve returns digest, open_blob → None → miss → refetch. Fine.

8. `min_age` compared against `age >= self.min_age` where age uses mtime. A blob re-fetched recently has fresh mtime. But a blob that is frequently *served* (read) never has its mtime updated — the doc in operations says "a package one job in a pipeline fetched is still there for the next" — but min_age is based on *write* time (modified), not access time. A blob written 30 days ago but served constantly will be evicted once over ceiling, despite heavy use. That's an LRU-vs-LFU design gap; the doc comment in age_of says "How long ago something was last written". The ops doc claims grace period protects recently-fetched packages, but fetching (serving from cache) doesn't update mtime. Hmm — "a package one job in a pipeline fetched is still there for the next" — if it was fetched into cache recently (miss → write), mtime is fresh. But the second job's request is a hit (no write), so mtime stays at first fetch time. With min_age=1h and interval 15m, a package fetched 61 min ago and heavily served since is eligible. That's eviction of hot blobs — a design limitation. Is it a defect to report? The docs overstate the grace period. Medium/low. It's a real behavioral gap: atime would be the correct signal (and `age_of` uses modified). Serving doesn't touch mtime. I'd report as yellow: `bug` sweep.rs age_of — eviction uses mtime, so serving a blob never refreshes its age, contradicting the documented grace period. Reasonable.

9. Metrics: `record_sweep(reclaimed.removed, reclaimed.bytes)` — main.rs passes (removed, bytes) and admin passes (reclaimed.removed, reclaimed.bytes). Signature `record_sweep(&self, blobs: u64, bytes: u64)`. values() loads sweep_bytes then sweep_blobs — order relative to COUNTERS array: COUNTERS order is blobs_removed then bytes_reclaimed (index 4 and 5). values() = [.., sweep_bytes_reclaimed, sweep_blobs_removed] — that's bytes first, blobs second! 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. So the exposition pairs blobs_removed counter with the bytes value and vice versa! Let me verify against the actual file.

COUNTERS in diff:
```
    ("cairn_proxy_sweep_blobs_removed_total", ...),
    ("cairn_proxy_sweep_bytes_reclaimed_total", ...),
```
values():
```
self.sweep_bytes_reclaimed.load(...),
self.sweep_blobs_removed.load(...),
```
Yes — swapped! The comment in metrics.rs even says "Keeping the two side by side is what stops a fifth counter from being rendered under a fourth one's name" — and the new code does exactly that: `sweep_blobs_removed_total` will render the bytes value and `sweep_bytes_reclaimed_total` will render the blob count. Definite bug, red or orange. Metrics lie to the operator — the counter help says "Bytes those blobs occupied" but the value rendered under it is the blob count. Severity: orange (monitoring wrong; could mislead capacity decisions). Line numbers from pr/services/proxy/src/metrics.rs.

Also check how the exposition renders: need to see render loop pairing COUNTERS[i] with values()[i]. Read metrics.rs to confirm.

10. `Json(reclaimed)` — admin.rs uses `use axum::Json;` but routes/mod.rs also imports Json — fine. Is `IntoResponse` imported in admin.rs? It imports `axum::response::{IntoResponse, Response}` — yes pre-existing.

11. `SweepQuery` dry_run: `#[serde(default)] dry_run: bool` — `?dry_run=true` parses. Fine. But `?dry_run=1`? serde_urlencoded... bool from "1"? serde's bool deserialization accepts "true"/"false" only for strings... axum Query uses serde_urlencoded; "1" errors → 400. Not a defect per se.

12. admin sweep handler: `match reclaim(&app, &headers, query.dry_run)` — `reclaim` is sync and blocking (long FS walk) directly in the async handler, blocking the tokio worker. Combined with #2 (no lock). Two findings: blocking the runtime, and bypassing the mutex. Blocking: the whole route has no timeout (deliberate), but it runs on the async runtime worker — for a multi-thread runtime with N workers, one blocked worker; concurrent sweeps from multiple admin requests could block several workers, plus the interval sweep — could stall healthz under load. Also, sync `fs` in async context. I'd report as yellow `performance`: admin.rs (sweep handler / reclaim fn) runs a synchronous full-store walk on the async runtime worker thread, blocking other tasks (health probes) for the duration.

Actually the same applies to main.rs spawn_sweeps: `app.sweeper.run().await` → `self.sweep(false)` sync inside the spawned async task. The module doc rationalizes synchronous fs, but it should use `spawn_blocking`. Blocking a worker thread every 15m for the duration of a 65k-directory walk. Yellow.

Should these be one finding or two? Different files/lines: main.rs and admin.rs. Report both? The format says report each concrete defect. I'd report admin.rs (worse: on request path, and can be triggered repeatedly) and maybe main.rs. Hmm, to keep findings high-precision, I'll report admin.rs as the primary; main.rs is same root cause but different site. I could report both; reviewers are compared. I'll report admin.rs blocking, and mention main.rs one too as separate line. Actually, careful about padding. The mutex bypass and blocking are both real. Let me decide final list:

A. metrics values() swap — definite, orange.
B. dry_run still deletes index entries via `forget` — definite, orange (docs promise no removal). Also even in dry run `gone` accumulates. Line: sweep.rs `forget(&index, &gone);`.
C. admin route bypasses the `running` mutex → concurrent sweeps violate one-at-a-time — definite, orange. Line: admin.rs where `app.sweeper.sweep(dry_run)` is called; also sweep.rs `pub fn sweep` lacking lock. Name both.
D. `clear_partials` removes in-flight fetch temp files unconditionally (no min_age check) → periodic sweep deletes active download's partial, commit rename then fails → fetch errors. High/orange. Line: sweep.rs in clear_partials.
E. blocking sync walk on async runtime (admin handler + interval task). Yellow.
F. age_of uses mtime; serving never refreshes it, so "grace period" doesn't protect in-use blobs, and hot blobs are evicted — docs promise otherwise. Yellow/low. Hmm, is this "concrete"? It's a behavioral defect vs documented intent ("a package one job in a pipeline fetched is still there for the next" — actually that scenario works if fetched within 1h). The ops doc: "CAIRN_CACHE_MIN_AGE is the grace period underneath that, so a package one job in a pipeline fetched is still there for the next." Job 2's fetch is a cache hit — doesn't update mtime — but job 2 comes within the hour presumably. The real gap: long-lived caches where blob written >1h ago but constantly served gets evicted. Design choice (approximates LRU by write time). I think this is a legit medium finding: eviction by mtime means frequently-served blobs are evicted; `atime` or updating on serve would be needed. But is it a "defect you can point at a line for"? Yes, age_of line. I'll include as yellow `bug`/design.

Hmm wait, actually let me reconsider: is atime reliable? Often noatime mounts. mtime-based is a reasonable choice. The doc claims it's about "fetched" — ambiguous. I'd rate low/blue maintainability? I think it's worth one line at blue/yellow. Let me keep it as yellow? Reviewers compared on precision — risky findings hurt. It is genuinely a defect that hot blobs (served constantly, never re-written) are first evicted when over ceiling, making the cache thrash on the working set. I'll include as yellow.

G. Removal failure still counts blob as removed/bytes reclaimed and adds to `gone` → forget deletes index entries for blobs still on disk. In non-dry-run: if remove_file fails (e.g. EACCES, or a directory, or transient error — not just NotFound "already gone"), the code proceeds as if removed. For "already gone" that's benign-ish (index entry cleanup is right). For other errors (e.g., permission), it counts phantom reclaimed bytes in metrics and deletes index entries. Low/blue. Worth a line? Maybe fold into D... I'll include as blue.

H. `DEFAULT_SWEEP_INTERVAL`/`from_hours`/`from_mins` stability. Check Rust: I need to verify. `Duration::from_mins` — hmm. Actually I now recall these were added: rust PR #117937? "Add Duration::from_mins and from_hours"... I'm not certain they're stable. The pre-existing test file uses them (lines 350-352 in the current config.rs which are NOT part of the diff — meaning they compiled before). Since pr/ is the post-PR state and tests already used from_mins before this diff, the project evidently compiles with them. So not a finding.

I. `.env.example` CAIRN_CACHE_MAX_BYTES comment says 32 GiB and value 34359738368 = 32*1024^3. Correct.

J. config: no validation that cache_min_age > 0 or that min_age < something. min_age zero is allowed — sweep would evict anything over ceiling immediately including just-written blobs? A just-committed blob referenced by index is protected by index. min_age=0 only affects unreferenced... no wait, unreferenced blobs are removed regardless of age anyway. min_age only gates the over-ceiling branch. min_age=0 is degenerate but allowed. Not a strong finding.

K. routes/mod.rs: sweep route placed outside timeout — deliberate, documented. Fine.

L. In `sweep()`, `held` counts all candidate blobs but if store over ceiling and all referenced and younger than min_age, nothing removed — fine, documented.

M. `scanned` unused in metrics — fine.

N. The admin route sweep: `SweepQuery` derive Deserialize with private field — fine for serde (fields private but within module; serde works with private fields as long as derive is in same module — yes).

O. `use axum::Json;` in admin.rs — but does admin.rs already import something named Json? Pre-existing code didn't. Fine. But wait — routes/mod.rs has `use axum::{Json, Router};` — separate files, fine.

P. main.rs: `spawn_sweeps(app.clone())` before serve — app is Shared (Arc). fine.

Q. Interval first tick: `tokio::time::interval` fires immediately on first `tick()`. The doc comment says "The first tick is one interval away" — that's wrong! `tokio::time::interval` completes the first tick immediately. So the background sweep runs immediately at startup — sweeping a cache at startup (contradicting the doc claim, and doing a full blocking walk before/during serving). Wait — the loop: `ticks.tick().await` — first tick returns immediately. So the first sweep happens right at startup, not one interval away. The doc comment claims the opposite. Hmm, actually: `interval` "The first tick completes immediately. Subsequent ticks..." Yes, tokio::time::interval first tick completes immediately. So the comment is factually wrong and behavior differs: sweep at startup. Consequence: a restart triggers an immediate sweep (blocking walk at startup), which the comment claims is avoided. Defect: incorrect comment + immediate startup sweep. Real severity low/medium: an immediate sweep at startup is actually maybe desirable, but the code contradicts its own documented intent. Report as yellow `bug` (doc/behavior mismatch): main.rs line with `tokio::time::interval`. Actually it's a correctness-of-comment issue with behavioral consequence. Include.

Let me verify tokio interval behavior: yes, "The returned Interval yields immediately" — first tick completes immediately.

R. `MissedTickBehavior::Delay` — fine.

S. `referenced()` — collect on INDEX dir via `collect` which reads metadata for each entry (wasteful but fine).

T. sweep.rs uses `Digest::parse` — needs Error import; uses crate::digest::Digest — fine.

U. In `sweep()`, `candidate.path.file_name()` — for blob path the filename is the hex. Index map keys are hex (digest.hex()). Blob file name is hex — matches. Good.

V. `forget` removes index entry files but leaves empty dirs — fine.

W. admin.rs `sweep` handler: no `Path` conflicts. The route method post — fine.

X. main.rs: sweep task not cancelled on shutdown — documented. Fine.

Y. One more: `clear_partials` in dry-run: counts files it *would* remove — including in-flight ones — fine-ish.

Z. sweep runs `referenced()` AFTER `clear_partials` — no issue.

Now check metrics.rs actual file to confirm line numbers and the render pairing.
Now let me read the remaining changed files to pin line numbers and verify the metric rendering pairing.
└ 5958 tok ·  25.7 tok/s · 23K ctx · 1193ms ttft · 231.5s wall
↳ 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
↳ read_file: read pr/services/proxy/src/routes/admin.rs
└ read_file: read complete
↳ read_file: read pr/services/proxy/src/main.rs
└ read_file: read complete
-- reasoning --
Now let me assess defects.

1. **Metrics ordering mismatch** — metrics.rs: COUNTERS has blobs_removed then bytes_reclaimed (lines 51-57), but `values()` (lines 88-97) returns bytes_reclaimed first, then blobs_removed. So `cairn_proxy_sweep_blobs_removed_total` gets the bytes value and `cairn_proxy_sweep_bytes_reclaimed_total` gets the blob count. This is exactly the bug the comment at line 30-32 warns about. Concrete, pointable: metrics.rs line 94 (or 51). I'll report at line 94. Severity: 🟠 high (operator alerts on wrong metric; docs tell operators to alert on `cairn_proxy_sweep_bytes_reclaimed_total`).

2. **Synchronous sweep blocks the tokio runtime** — sweep.rs `sweep()` is fully synchronous `std::fs`, and it's called from async contexts: from `Sweeper::run()` (an async fn spawned on the tokio runtime, main.rs:116) and directly from the axum handler `admin::reclaim` (admin.rs:76). A large store sweep (65k leaf dirs, the doc itself mentions) blocks the worker thread. On the multi-thread runtime this stalls other tasks somewhat but not fully; more importantly, the admin route blocks the tokio worker thread — with default worker threads = cores, several concurrent sweeps... but the Mutex serializes. Blocking one worker thread. The module doc acknowledges the tradeoff, arguing it's cheaper than the blocking pool. Is this a defect? The route handler calling a fully-blocking filesystem walk inline in async context is a real concern — it can block a worker thread for tens of seconds on a large store, stalling other requests. The docs themselves say "a sweep of a large store legitimately takes longer than ten seconds" — and they put it outside the timeout, but blocking the async executor thread is the issue. I'd flag as 🟡 performance: the sweep walk is synchronous and runs directly on the tokio worker thread (admin.rs:76 and main.rs:116 via run()), blocking the executor for the duration of the walk; a large store stalls all other requests on that worker. Should use `spawn_blocking`. Severity medium given the deliberate doc tradeoff. Hmm, it's deliberate and documented. But deliberate + wrong is still a defect. The blocking-pool argument only justifies not using tokio::fs per-op; it doesn't justify running it on the async executor thread. Actually running it on the async thread is strictly worse than spawn_blocking with one call. The comment's argument (65k round trips through the pool) conflates two things. I'll flag it 🟡.

3. **`Duration::from_mins` / `from_hours`** — config.rs:83-84 uses `Duration::from_hours` and `Duration::from_mins`. These are unstable APIs in std? `Duration::from_hours` and `Duration::from_mins`... As of Rust 1.8x? `Duration::from_secs` etc are stable. `from_hours`, from_mins, from_days` were unstable (`duration_constructors` feature) for a long time; stabilized in Rust 1.91 (August 2025?). Actually `Duration::from_hours` etc were stabilized in Rust 1.91.0? Let me think. The `duration_constructors` feature... `Duration::from_mins`, `from_hours`, from_days` were const-unstable. They were stabilized in Rust 1.91 (2025-08). Given this benchmark, the test file already uses `Duration::from_mins(2)` and `from_hours(1)` at lines 350-351 in the existing tests — so the codebase already uses them. So not a defect (pre-existing usage in tests, presumably compiles in this project). Skip.

4. **`.env.example` docs claim**: `CAIRN_SWEEP_INTERVAL=15m` — parse_duration accepts m. Fine. `CAIRN_CACHE_MAX_BYTES=34359738368` — parse_bytes: digits then unit. digits = trim_end_matches ascii-alphabetic → "34359738368", unit "" → scale 1. Fine.

5. **`parse_duration` bug pre-existing**: `digits.trim_end_matches(|c| is_ascii_alphabetic)`? In parse_duration line 256: `trimmed.trim_end_matches(|c: char| c.is_ascii_alphabetic())` — trims trailing alphabetic chars. Wait "18446744073709551615h" → digits "18446744073709551615". OK. Pre-existing anyway, not part of diff.

6. **Dry run semantics in `clear_partials`**: In dry-run, partials are counted but not removed — fine. But note in dry_run mode `removed` counts blobs that would be removed even if... fine.

7. **`remaining >= self.max_bytes`** vs docs: "removes the oldest blobs until the store is back within the ceiling". `remaining >= max` means when remaining == max it removes one more (to get below). Minor off-by-one: store is kept strictly below the ceiling rather than within. Docs say "back within". Also `Reclaimed.held` etc. Trivial, skip.

8. **Bigger issue: sweep deletes in-flight fetches' index entries / blobs?** Consider race: `referenced()` reads the index; while a fetch is in progress, the blob is written and then the index entry is linked (store.rs link after commit?). Let's check routes/cache.rs to see the order: fetch → commit (blob on disk) → link (index entry). If a sweep runs between commit and link, the blob has no index entry → removed as unreferenced. Then link writes an index entry pointing at a blob that is gone → stale entry → serve path checks blob exists → miss → refetch. Not permanent damage but... acceptable. Actually wait, does the serve path check blob existence? store.rs `open_blob` returns Option. And resolve returns digest... Let me check cache.rs serve flow to confirm. If resolve hits and blob open returns None, it refetches. So transient. Skip.

But bigger: **the sweep deletes files under `incoming` that belong to in-flight fetches**. `clear_partials` removes every file in `incoming` unconditionally. An in-progress fetch (e.g., a 200 MiB download taking a minute) has its temp file in `incoming` (store.rs temp_path → incoming_dir). A sweep every 15 minutes removes it mid-write. On Unix, unlinking an open file is fine — the writer keeps writing to the unlinked inode, and at commit the rename fails (NotFound) → fetch fails. So a concurrent sweep can kill in-flight downloads. The doc says "A file in `incoming` is a fetch that is not coming back" — false: files in incoming include active fetches. This is a concrete defect: sweep.rs:224/232 (clear_partials) removes the temp file of any fetch in progress, causing that fetch to fail at commit (rename NotFound). How does the error surface? commit's rename fails → error → upstream failure. Probability: downloads lasting longer than the sweep interval window... a sweep runs every 15 min, and any concurrent large download is at risk. This is a genuine race defect. Severity 🟠 high? It causes fetch failures but only when a sweep coincides with an in-flight fetch, and the failure is a single failed request (client may retry). I'd say 🟠 or 🟡. Also `BlobWriter::Drop` removes the temp — already handles cleanup on failure; the abandoned-partials story is only for killed processes. So clear_partials needs a min-age check for the files it removes. Note: no age check at all in clear_partials — the `cache_min_age` grace period isn't applied. Yes, flag: sweep.rs:232 (or 224).

Also the same race for blobs: an in-flight fetch commits the blob (rename into blobs/), and before `link` writes the index entry, the sweep sees an unreferenced blob and removes it. Then link writes a stale entry. That's handled by the miss path, less severe. But combine with `forget`: sweep collects index before, removes blob as unreferenced, then... no, forget only removes entries naming digests in `gone`. The race: sweep reads index (blob absent), fetch commits blob, sweep collects candidates, blob not in index → removed; then fetch links index entry → stale entry pointing at removed blob. Serve: resolve hit → open_blob None → refetch (need to check cache.rs handles that gracefully). Let me read cache.rs to confirm the miss path handles a present-index-but-missing blob.

Also check: does cache.rs serve path handle resolve-hit + blob-missing? Let me read routes/cache.rs.

9. **`referenced` counts unreferenced blobs with NO index at all**: fine.

10. **`forget` removes index entries for blobs removed because they were over-ceiling-and-old** — intended.

11. **`held` counts... fine.**

12. **Admin route blocks**: also, the sweep route handler `reclaim` calls `app.sweeper.sweep(dry_run)` synchronously (doesn't take the mutex!). Wait — `Sweeper::run` takes the mutex; `Sweeper::sweep` does not. The admin route calls `app.sweeper.sweep(dry_run)` directly (admin.rs:76), bypassing the `running` mutex. So the one-at-a-time promise is broken: a manual sweep via the route runs concurrently with the interval sweep (main.rs:116 uses `run()` which locks). The doc comment on `running` 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 sweep route bypasses it entirely. Two concurrent sweeps over one directory → exactly the scenario the module doc warns about ("between them they would take the store far below the ceiling"). Concrete: admin.rs:76 should call `run()` (needs await in async handler). This is a real defect. 🟠 high. Also, both sweeps may call `forget` concurrently removing same files — benign. But double-counting removal and over-eviction: sweep A reads index, removes blob X as unreferenced; sweep B also reads index, X gone already... Both decide based on same totals → both remove oldest blobs until remaining < ceiling, each computing `remaining` from the same starting `held` → combined they remove ~2× the excess. High severity. Report at admin.rs:76.

Wait, actually let me double check: `run()` is async and takes the lock; `sweep()` is sync without lock. In the admin route, `reclaim` is a sync fn called from the async handler, calling `app.sweeper.sweep(dry_run)`. Yes, bypasses the mutex. Definitely a defect.

13. **Metrics rendered pairing** — confirmed defect #1.

14. **main.rs spawn_sweeps holds `app` forever** — fine, keeps process alive. Not a problem.

15. **`tracing::info!(?reclaimed, ...)`** — Reclaimed derives Debug. OK.

16. **Docs: operations.md says "takes the same bearer token as the purge route"** — true.

17. **`.env.example` CAIRN_SWEEP_INTERVAL documented** fine.

18. **config: no validation that cache_min_age > 0** — cache_min_age of 0 is fine (means no grace). OK.

19. **`Reclaimed.bytes` counts even when remove_file failed** (sweep.rs:125-137): if removal fails (e.g., EPERM), the code still subtracts from remaining, adds to bytes, counts removed, and adds to `gone` → `forget` deletes the index entries for a blob that was NOT removed. That's a real bug: a failed unlink (permission error, or a directory, or on Windows an open file) → the blob stays, but its index entries are deleted → the artifact becomes unreachable (next request refetches it, re-links — so it self-heals on next access but wasted space and the blob becomes permanently unreferenced, and next sweep will remove it). Consequence: metrics over-report reclaimed bytes; index entries deleted for a still-present blob. Moderate: 🟡. Actually also: if the file was removed by another process between collect and remove_file (NotFound), counting it as removed is fine. But for other errors, the accounting is wrong and index entries get dropped for blobs still on disk. Also `remaining` decremented for a blob still there → evicts more than needed. 🟡 medium.

Hmm, but also: a failed removal (non-NotFound) is exactly the case where you must not forget the index entries. Report at sweep.rs:126-137 (point at 126 or the accounting lines 134-137; I'll cite 134 or 126). I'll cite line 126 area: "remove_file error is ignored but the blob is still counted as removed and its index entries deleted". Cite sweep.rs:126.

20. **`collect` uses `fs::metadata` (follows symlinks)** — comment says links counted at the size of the link, but `fs::metadata` follows symlinks, so it counts the target's size, not the link's. `symlink_metadata` would count the link. So the comment's claim is false and hardlinks/symlinks... For hardlinks, metadata.len() is the file size (hardlinks share inode, len is target size). The comment says "A link is counted at the size of the link and not of whatever it points at" — with fs::metadata, a symlink to a 1 GiB file outside the store would be counted as 1 GiB, and worse: removing the symlink deletes only the link, yet `bytes` reclaimed is counted as 1 GiB. Minor. Also a symlink to a directory: `fs::metadata` is_dir → recursion into a directory outside the blob store → collect walks arbitrary directories, and could remove files there? `remove_file` on candidates — candidates are files collected; a symlinked dir walk collects files under the target directory, and then those files could be removed if not in the index! E.g., `blobs/sha256/ab/cd` is a symlink to `/some/other/place` — the sweep recurses and unlinks files outside the blob store. Is that plausible? The comment says stores moved between volumes "often has blobs linked into it". If someone hardlinks... hardlinks are fine (same inode, is_dir false for files). Symlink to a dir: possible in a migration. The sweep would remove real files outside the store. Severity? It's a defensive-coding gap; the doc explicitly anticipates links. Using `symlink_metadata` would fix. 🟡 medium security-ish. Also, following symlinks breaks the "counted at the size of the link" claim. I'll report as one finding at sweep.rs:164: `fs::metadata` follows symlinks, contradicting the comment and letting a symlinked directory walk (and unlink) files outside the blob store; use symlink_metadata. Medium.

21. **cache.rs race** — let me read cache.rs to check the resolve-hit-but-blob-missing path, and whether commit→link window matters.

22. **`age_of` uses mtime as "age"** — the docs say "the oldest blobs" and "how long a blob is left alone" — but mtime is creation time (no atime updates necessarily; reads don't update mtime). So "oldest" = oldest written, not least recently used. The .env.example says "How long a blob is left alone before a sweep may remove it" — misleading, but behavior-wise eviction by insertion age is a legitimate policy (FIFO). Not exactly a defect; docs vs behavior mismatch: "the package somebody fetched this morning stays" — true, it was written this morning. "left alone" implies access-based; mtime isn't access time. Minor doc mismatch; also a popular blob gets evicted eventually. Not a concrete defect I'd report. Maybe skip, or blue. The operations.md says "`CAIRN_CACHE_MIN_AGE` is the grace period underneath that, so a package one job in a pipeline fetched is still there for the next" — with mtime semantics, a blob written 2h ago that's being served constantly becomes eligible for eviction once over ceiling; "left alone" is wrong. This is a design limitation, documented as if it tracked access. Low severity maintainability/doc. Borderline. I'll include as 🔵 maybe. Hmm, "report only defects you can point at a line for" — docs line operations.md:50-ish. The diff line: `CAIRN_CACHE_MIN_AGE=1h` comment in .env.example "How long a blob is left alone before a sweep may remove it." and sweep.rs age_of uses modified(). I could report: sweep.rs:185-189 uses mtime, so `cache_min_age` is time-since-written, not time-since-last-used; docs in .env.example claim "left alone". Consequence: frequently-served blobs are evicted after 1h regardless of use. 🔵 low. I'll include it—it's concrete and pointable.

Let me read cache.rs to check the serve path and also routes/mod.rs and error.rs briefly.
Let me check the cache route to see how a resolve-hit with a missing blob is handled, and confirm the ordering claims elsewhere.
└ 3792 tok · 140.6 tok/s · 30K ctx ·  924ms ttft · 27.0s wall
↳ read_file: read pr/services/proxy/src/routes/cache.rs
└ read_file: read complete
↳ read_file: read pr/services/proxy/src/routes/mod.rs
└ read_file: read complete
-- reasoning --
Now let me enumerate defects carefully.

**1. `Duration::from_hours` and `Duration::from_mins`** — Rust 1.100 (or which?) stabilized `Duration::from_hours` and `Duration::from_mins`? Hmm. Actually Rust recently stabilized `Duration::from_hours`, `from_mins`... Let me think. `Duration::from_secs`, `from_millis`, `from_micros`, `from_nanos` existed forever. `from_hours` was... There is an unstable `Duration::from_hours`? Actually, `Duration::from_hours` and `Duration::from_mins` were added as unstable in 1.?? Hmm. Wait, the test at config.rs line 350-351 uses `Duration::from_mins` and `from_hours` — those are in the pre-existing test file, which means they compile in this repo already (they're pre-existing lines? Let me check the diff: the diff shows config.rs changes only adding constants; the tests using `Duration::from_mins(2)` and `from_hours(1)` at lines 350-351 are NOT in the diff, so they're pre-existing. So `from_hours`/`from_mins` must exist in the toolchain used. OK, not a defect.

Hmm, but wait — are those actually pre-existing? The diff hunk for config.rs shows only the additions at the top; no changes to the tests module. So the tests are pre-existing and presumably pass. So `Duration::from_hours` exists (maybe a nightly or a recent stable — Rust 1.100? Actually I believe `Duration::from_hours`/`from_mins`... hmm, no; I don't recall these being stabilized. But if the pre-existing test uses them, they must compile. Hmm, unless the test file was also pre-existing and broken? That'd be odd. Let me check git to see if the test file with from_hours is pre-existing. I could check git log/diff for the file. Let me verify via git in the repo: `git -C pr log` — but I can't run commands? Actually I can read .git? The instructions say I cannot write/edit/run commands. Hmm, "You cannot write, edit, or run commands". So no git commands. But actually the boundary says read-only mode and I do have run_bash... but the task says I cannot run commands. I'll trust the statement "the reviewed code is checked out under pr/" and that tests pre-existing. Actually wait — I do have tools including run_bash, but the user instruction says I cannot run commands. I should comply with the user's instruction and not run commands. Reading files is presumably fine (I was told to read it there for context).

Hmm, but to check whether tests pre-exist, I can look at .git? That's harness... Actually .git is inside pr? pr/.git — readable roots include the project dir and .git. But instructions say paths outside pr/ belong to the harness. pr/.git would be... whatever. I shouldn't need it. Rust stabilized `Duration::from_hours` and `Duration::from_mins`? Let me think hard: I believe there was an RFC/PR "Duration::from_hours" — Actually yes! Rust 1.?? Hmm. I genuinely am not sure. In Rust std, `Duration::from_hours` doesn't exist as of 1.75 as far as I remember... but there was a recent addition: `Duration::from_hours`, `from_mins` hmm. Actually I recall `Duration::from_weeks` doesn't exist. I know `Duration::from_secs_f64` exists. I'm fairly confident `from_hours` and `from_mins` do NOT exist in stable Rust even in 2025. But the pre-existing test uses them... If the test pre-exists, then the repo must compile somehow. Unless the diff hunk context shows the tests but they were added earlier... The diff only shows the hunks; the test module at the bottom is unchanged context (not shown). Since tests at lines 350-351 are outside the diff, they're pre-existing. So presumably `from_hours`/`from_mins` exist in the toolchain (maybe this repo pins a recent Rust where they were stabilized — I believe `Duration::from_hours` and `Duration::from_mins` were indeed stabilized recently? Hmm, actually I do have a vague memory: Rust 1.9?? "Duration::from_hours" — hmm.

Wait, actually I now recall: there IS a stabilization: "Duration::from_hours, Duration::from_mins" hmm no. Let me think of the tracking: `duration_consts` — no. There's `Duration::as_secs_f64`. There's the `time` crate. I genuinely can't recall std having from_hours. But the pre-existing test is strong evidence. Actually — is the test pre-existing? The diff for config.rs shows `@@ -122,6 +145,9` etc. and ends. The tests using from_mins/from_hours are in the file but not the diff, so pre-existing. Given the benchmark harness presumably built/tested this, they compile. So not a finding.

Hmm, but wait — maybe the diff's post-image includes tests that the PR author would have needed... no, the test hunk isn't in the diff at all, so it's unchanged. Fine.

**2. Metrics pairing bug (metrics.rs lines 50-58 vs 94-95).** COUNTERS order: hits, misses, upstream_failures, policy_refusals, **blobs_removed**, **bytes_reclaimed**. `values()` order: hits, misses, failures, refusals, **bytes_reclaimed**, **blobs_removed**. The zip pairs name↔value: `cairn_proxy_sweep_blobs_removed_total` will be rendered with the *bytes* value, and `cairn_proxy_sweep_bytes_reclaimed_total` with the *blob count*. That's a real defect. Line number: the zip happens at render (line 107), but the defect is the ordering mismatch — best line: metrics.rs:94 (or 33/51). I'll point at 94-95. The doc comment at line 30-32 even says "Keeping the two side by side is what stops a fifth counter from being rendered under a fourth one's name" — and the PR broke exactly that. Severity: orange (high) — monitoring/ops impact; both sweep counters wrong. Category: bug/monitoring. I'd say 🟠.

**3. Sweep removes in-flight fetches' blobs? No — blobs are only named after commit. Index entry is linked after commit. Race: sweep computes `index` map first, then collects blobs; a blob committed between the two reads... blob written after collect → not in candidates → safe. A blob committed after collect but whose index entry existed before? The index map was read before, so the blob (not in candidates) is safe. A blob in candidates whose index entry is created after `referenced()` runs: blob committed just before collect? Timeline: sweep reads index at T1, walks blobs at T2. A fetch that commits blob at T0 < T2 but links index at T3 > T1: the blob appears in candidates, and index map doesn't contain it → sweep treats it as unreferenced and deletes it, plus forget() — index.get(hex) is None so no index removal, the newly linked index entry remains, pointing at a deleted blob. Consequence: the artifact is deleted right after being cached; next request refetches. Not data loss (content-addressed, refetches). Severity: low/medium. It's a TOCTOU race. Also min_age gives no protection because unreferenced removal ignores age (deliberately per comment). The window is small (between index scan and blob walk — actually the blob walk takes long for a big store, so the window is seconds-to-minutes; a fetch that commits during the blob walk, whose blob is seen later in the walk, and whose index entry was written after the index scan → deleted). This is a real race worth reporting: 🟡 medium. Line: sweep.rs:119 (`!index.contains_key(hex)`).

Actually, could we also note the reverse ordering would fix: read blobs first then index. Blob walk first: blob committed during walk appears in candidates; index read afterwards will include the entry linked... hmm if link happens after the index read too, still racy. But the fix is beyond scope; report the race.

**4. Age is mtime, not last-access.** The docs claim "the oldest blobs" = least recently wanted. `age_of` uses `modified()` — the time the blob was written, never updated on serve. So a blob fetched every build all day but cached a year ago has age ~1 year and is removed first, despite being hot. Docs in .env.example say "How long a blob is left alone before a sweep may remove it" — implying idle time; mtime is not "left alone" time. This is a design defect: LRU claim based on write time. Consequence: hot blobs get evicted; cache hit rate collapses for a long-lived store. 🟠 or 🟡. The comment at sweep.rs:100 says "the blobs nothing has wanted for longest" — mtime doesn't measure that. Line 186 (`meta.modified()`). Severity: yellow/orange. It's a genuine behavioral bug relative to documented intent ("How long a blob is left alone"). I'd say 🟠 high? The consequence: frequently-served old artifacts evicted first. I'd call it 🟡 medium-high. Let me think — for a cache, evicting by mtime instead of LRU is a classic flaw; docs promise "left alone". I'll rate 🟠.

Hmm, but is it a "defect you can point at a line for"? Yes: sweep.rs:186 vs .env.example line. I'll cite sweep.rs:186.

**5. `clear_partials` deletes files in `incoming` that belong to *in-progress* fetches in this very process.** BlobWriter creates temp file in `incoming`, writes during download, commits by rename. A sweep (interval sweep runs concurrently with downloads) calls clear_partials which unlinks **every** file in incoming, including the temp file a live fetch is currently writing. On POSIX, the unlink succeeds; the fetch keeps writing to the now-unlinked inode; commit renames... rename of an unlinked-but-open file: the file has no directory entry, so `fs::rename(temp, target)` fails with ENOENT (the source path doesn't exist). So the fetch fails with a storage error mid-download. Worse: the doc comment in sweep.rs claims "A file in `incoming` is a fetch that is not coming back" — false for concurrent fetches in the same process, and other proxies sharing the dir (temp names include pid, so another proxy could... they can't tell which pids are live). Consequence: any fetch that happens to be in flight during a sweep is killed; under a busy proxy with 15-min sweeps, every sweep aborts all in-flight downloads. That's a significant bug. Severity: 🟠 high (data-plane failures during sweeps). Line: sweep.rs:232 (`fs::remove_file(entry.path())`) or 224 (clear_partials). Also cache.rs line 90-97: rename fails → error at commit — actually the failure surfaces as Error::Storage at `writer.commit()`? In cache.rs:151 `let digest = writer.commit().await?;` — commit does rename, which errors → fetch returns 500. Yes.

Also possible that Drop's remove_file logs a warning for a file already gone — minor.

Rate: 🟠 high. Actually could be 🔴? It breaks in-flight downloads during every sweep, and also removes the temp file — hmm, but consequence is a failed request (500), retried fetch next time. Not critical data loss. 🟠.

**6. Race: sweep vs serve/purge removal** — remove_file error handled. Fine.

**7. `forget()` deletes index entries for digests removed due to ceiling** — intended. But note: `gone` includes blobs removed for being unreferenced (no index entry) — fine.

But: `forget` also deletes index entries when the blob was removed because it was over-ceiling. Multiple index entries point at the digest; deleting all is consistent.

However, subtle bug: when `fs::remove_file` fails (line 126), the blob is NOT actually removed, but the code still decrements `remaining`, counts it, and adds to `gone` → `forget()` then deletes the index entries pointing at a blob that still exists. Consequence: index entries deleted for a live blob → blob becomes unreferenced → next sweep deletes it (or requests miss and refetch; blob leaks until next sweep deletes it as unreferenced). That's a real inconsistency: on removal failure the blob should not be added to `gone`. Line 126-137. Severity: 🟡 (blue?). The comment says failure is "usually a blob that has already gone" — if already gone, then the index entries are stale anyway, so forget is fine. But if failure is permission denied, the blob stays and its index is removed. Medium-low. 🟡 or 🔵. I'll say 🟡 yellow? Consequence: blob leaks as unreferenced (will be removed by next sweep since unreferenced) — actually next sweep removes it because unreferenced. And served requests in between: resolve → entry gone → miss → refetch → link. So the failure mode is a spurious miss, self-healing. 🔵 low. Hmm, but the metrics also count bytes not actually reclaimed. Low. 🔵.

**8. Dry-run double-counts / forget in dry run?** In dry run, `gone` is populated but `fs::remove_file` skipped, and then `forget(&index, &gone)` at line 140 runs **regardless of dry_run** — deletes index entries for blobs that were NOT removed! That's a clear bug: a dry run mutates the store, deleting index entries for blobs it decided it would remove but didn't. Consequence: `?dry_run=true` — documented as "reports what one would reclaim without removing anything" (docs/operations.md) — actually removes index entries, turning referenced blobs into unreferenced ones that the next sweep deletes. That's a serious bug. Severity: 🔴? Dry run destroys the cache's index (not the bytes). Blobs remain but become unreachable; next sweep deletes them as unreferenced. So a dry run effectively evicts everything it reported. Data isn't lost permanently (refetch). But it contradicts the route's core promise and silently corrupts reachability. I'd rate 🔴 critical or 🟠. Given it makes the documented safe operation destructive, and repeated dry runs destroy the cache — I'll say 🔴. Hmm, severity calibration: critical = data loss/security. The index entries are cheap to rebuild via refetch; no permanent loss. But it silently breaks the primary route (misses) and the next sweep deletes blobs. I think 🟠 high is defensible; 🔴 also defensible. The dry_run flag is supposed to be read-only and it isn't — I'll go 🟠. Hmm. Let me weigh: consequence is all blobs that a real sweep would remove become unreachable and then actually removed by the next sweep — the dry run isn't a dry run at all, it schedules deletion. Effectively equals running the real sweep with a delay. I'll mark 🔴 — the feature's entire purpose (safe preview) is inverted. Eh — but "critical" usually means crash/security/data corruption. Deleting index entries is state corruption. I'll go with 🔴 and describe precisely. Actually let me reconsider: line 140 `forget(&index, &gone);` runs unconditionally. Yes, that's the bug. I'll cite sweep.rs:140. I'll rate 🔴.

Wait — also check: in dry run, `gone` contains hexes for unreferenced blobs too (index.get(hex) is None → forget does nothing for them). For over-ceiling referenced blobs, forget deletes their index entries. Yes.

**9. `held`/`remaining` vs `>=` boundary:** `remaining >= self.max_bytes` — removes blobs while remaining is at/above the ceiling, stops when below. That matches "back within". Fine. But note it removes only blobs with age >= min_age; if all over-ceiling blobs are younger than min_age, nothing removed — that's the grace period, fine.

**10. Reclaimed partials counting in dry run:** clear_partials in dry_run doesn't remove but counts `removed += 1` — it reports what it would remove. Fine ("reports what one would reclaim").

**11. `collect` follows into `index` dir? No, only blobs dir. Fine.**

**12. Sweep blocking the async runtime:** `Sweeper::sweep` is fully synchronous std::fs over potentially 65k directories, called from async context: from `run()` inside a tokio task (blocking the runtime thread — the doc comment acknowledges and justifies it, but it blocks a worker thread; with a multi-thread runtime and 65k readdir calls, one core is pinned, but other workers continue. For the HTTP route `admin::sweep`, it's called synchronously in the handler (line 76 in admin.rs: `app.sweeper.sweep(dry_run)`), blocking a runtime worker for potentially minutes — with default worker threads = cores, one blocked thread; other requests continue. It's a deliberate documented tradeoff. Not a "defect I can point at"? Borderline. The doc justifies it. I'd skip or mark 🔵 maintainability/performance? Given doc explicitly justifies, skip. Actually blocking the executor thread in async fn is generally a defect; tokio docs warn blocking >10-100µs. But the comment addresses it. Given three-reviewer comparison and instruction not to pad, I might report it as 🔵. Hmm. The consequence: a big store sweep blocks one worker; with `rt-multi-thread` default workers = number of cores. On a 1-core container, the whole proxy stalls during a sweep. That's real. 🔵 low/yellow. I'll consider reporting as 🟡 performance? The sweep walk is O(all files) with readdir; 65k leaves ~ maybe 1-2 s on SSD. 10 seconds is fine-ish. On slow volumes (the exact scenario docs mention — volume filling), could be worse. I'll report 🔵 low.

**13. spawn_sweeps metrics double counting?** run() → record_sweep in main.rs. Route sweep(dry_run=false) also records. Both fine — separate sweeps.

But note: main.rs line 117 `app.metrics.record_sweep(reclaimed.removed, reclaimed.bytes)` — argument order (blobs, bytes) matches record_sweep(blobs, bytes). Fine.

**14. `SweepQuery` with invalid query string (e.g., `?dry_run=maybe`)** — axum Query rejection → 400 automatically. Fine. Note: `Query` extractor rejection bypasses the handler so no auth check... wait, Query extraction happens before handler runs; a malformed query returns 400 without checking auth. That leaks nothing. Fine. But `?dry_run` empty string → serde fails → 400. Acceptable.

Hmm — also `?dry_run=TRUE` (uppercase) fails — minor, skip.

**15. Route conflict:** `/v1/admin/cache/sweep` POST vs `/v1/admin/cache/{digest}` DELETE — different methods/paths; axum 0.8: `/v1/admin/cache/{digest}` with delete; `/v1/admin/cache/sweep` with post — path conflict? In axum, `/v1/admin/cache/sweep` matches `{digest}` pattern for DELETE, and the specific route for POST. Since routes differ by path and method... Actually axum matchit: a static segment "sweep" and a param `{digest}` at the same position — matchit allows static to take precedence. DELETE /v1/admin/cache/sweep would match the `{digest}` route and try Digest::parse("sweep") → 400 invalid digest. Fine.

**16. `sweep_interval` validation but not `cache_min_age`** — cache_min_age=0 allowed; means over-ceiling blobs removed immediately, killing the grace period — but that's a valid config choice. Not a bug.

**17. config: no validation that cache_max_bytes >= something; fine.**

**18. `.env.example` CAIRN_CACHE_MAX_BYTES=34359738368 = 32 GiB. Fine.**

**19. Docs claim "removes the oldest blobs until the store is back within the ceiling" — but removal only for age >= min_age; fine, documented.

**20. metrics doc comment line 3 "twenty lines" now wrong? Line 3 says "The exposition below is twenty lines" — with 6 counters it's 18 lines + ... still ~ "twenty". Skip.

Line 31: "what stops a fifth counter from being rendered under a fourth one's name" — stale wording but the pairing bug itself is the finding.

**21. `Reclaimed` field `held`/`scanned` in the interval sweep are fine.

**22. `referenced()` reads entire index into memory — fine size-wise.

**23. The on-demand sweep route bypasses the mutex:** `admin::reclaim` calls `app.sweeper.sweep(dry_run)` directly (line 76 admin.rs), NOT `run()` which takes the lock! So the on-demand sweep does not serialize with the interval sweep — two sweeps can run concurrently over the directory, which the module doc (sweep.rs:10-12) and the `running` mutex exist to prevent. The doc comment on `running` 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 route caller bypasses `run()` entirely. That's a concrete defect: admin.rs:76 calls the lock-free `sweep` while `run()` exists precisely to serialize. Consequence: concurrent sweeps double-delete/double-count; both compute from stale totals. Severity 🟠 or 🟡. It's clearly a bug — the route should call something like a locked sweep (run() doesn't take dry_run though; the design gap: run() doesn't support dry_run, so the route couldn't use it). I'd report 🟡 yellow? Consequence: two sweeps concurrently deciding from totals the other changes — exactly what the docs say must not happen. 🟠 high? For an admin route that's rarely called vs interval sweeps — a concurrent overlap window. I'll say 🟡.

Hmm wait, but also the dry_run route calling `sweep` concurrently with a real interval sweep: forget() deleting index entries etc. Fine as one finding.

Also note: on-demand sweep is synchronous in handler — blocks runtime thread (mentioned above).

**24. `spawn_sweeps` doc "Not part of the graceful shutdown" — the spawned task keeps running during shutdown; axum serve graceful shutdown then main returns, runtime drops → task killed. Fine.

**25. MissedTickBehavior::Delay comment correctness — fine.

**26. `collect` uses `fs::metadata` (follows symlinks) — comment claims links counted at link size; `fs::metadata` follows the symlink and returns the *target's* size, contradicting the comment. `symlink_metadata` is what returns the link's own size. The comment at sweep.rs:160-163 says "A link is counted at the size of the link and not of whatever it points at" — but `fs::metadata(&path)` follows the link! So a store with hardlinks... hardlinks don't have separate sizes anyway (fs::metadata on a hardlink returns the file size — a hardlink IS the file). Symlinks: fs::metadata follows to target, so size = target size, not link size. So the comment's claim is false for symlinks. Consequence: `held` overcounts and, more importantly, ceiling eviction decisions mis-measure. Minor: 🔵 low. Line 164.

**27. `age_of` uses `modified()` — for a symlink-followed metadata fine.

**28. Security: on-demand sweep route outside timeout — deliberate, documented. The 10s TimeoutLayer on purge only... fine.

**29. `clear_partials` counts `removed += 1` in dry-run mode even though nothing removed — reported as `partials` in Reclaimed; the doc for dry run says "reports what a sweep would reclaim" — counting what it would remove is right. Fine.

**30. Race between sweep and purge/admin remove — handled (remove_file error → debug).

**31. `referenced` reads index entries concurrently with `BlobStore::link` writes — a torn read? link writes temp + rename, so reads see old or new. Fine.

**32. Interval sweep removal of a blob whose index entry exists → forget deletes index entries → subsequent concurrent requests in cache.rs: open_blob returns None → treated as miss → refetch. Fine.

**33. main.rs: spawn_sweeps clones app; on graceful shutdown the task isn't aborted — axum::serve returns, serve() returns, main returns, `#[tokio::main]` runtime shuts down and the spawned sweep task is dropped at next await — a sweep in progress is killed mid-way; doc says that's fine. OK.

**34. Missing: the sweep of the store counts `held` as blobs only; the ceiling documented as "The most the blob store may hold" — incoming partials not counted toward held. Minor, skip.

Now the biggest question: **#5 clear_partials deleting in-flight temp files.** Let me double check temp naming: `incoming/{pid}-{seq}`. A sweep's clear_partials removes ALL files in incoming including those of live writers in the same process. Doc comment says "A file in `incoming` is a fetch that is not coming back" — wrong for in-flight fetches. Interval sweep runs every 15 min; any download active at that moment gets its temp unlinked; the writer keeps writing (fd open); at commit, `fs::rename(temp, target)` — temp path no longer exists → ENOENT → commit fails → 500 to client and BlobWriter drop tries remove_file (warns). So every sweep kills all in-flight fetches. On a busy proxy, fetches are frequent; a 200 MiB artifact over slow network could take minutes → high probability of collision every 15 minutes. This is a real, significant bug. 🟠 high.

Fix would be to only remove files older than min_age (mtime) or skip pid-own files. Report line 232 (or the function). I'll cite sweep.rs:224.

Now also check `Drop for BlobWriter` warns — fine.

**35. `Reclaimed` serialized includes `held`, `scanned` — fine.

**36. Sweep and blob being served concurrently: sweep removes blob file while cache.rs has it open — on POSIX, open fd survives unlink; serving continues. Fine.

**37. cache.rs fetch race with sweep `forget`: index entry removed after resolve → miss → refetch → link again. Fine.

**38. Config: `cache_min_age` used only for over-ceiling removal; `.env.example` says "How long a blob is left alone before a sweep may remove it" — but unreferenced blobs are removed regardless of age (per design comment). Doc inconsistency, minor. Skip or 🔵? The .env.example comment is misleading: min age does NOT protect unreferenced blobs. That's a doc defect with a line: .env.example line 44 ("How long a blob is left alone before a sweep may remove it"). 🔵 documentation. Hmm, is it worth reporting? It could mislead an operator. Low. I'll include as 🔵 maybe. Actually the sweep code comment explicitly justifies why age doesn't apply to unreferenced. The .env.example line overstates. I'll include as 🔵 doc.

Let me also double check finding #2 more carefully — the counter pairing. COUNTERS order (5th, 6th): blobs_removed, bytes_reclaimed. values(): [.., sweep_bytes_reclaimed, sweep_blobs_removed]. zip → 5th name pairs with bytes value; 6th name with blobs value. Yes, swapped. Both `# HELP` "Cached blobs a sweep removed..." gets the byte count. Definite bug. Line: metrics.rs:94 (values order) — I'll point to 94-95, single line 94.

Also docs/operations.md references `cairn_proxy_sweep_bytes_reclaimed_total` — which will actually contain blob counts. Fine, covered.

**39. Also check `record_sweep` argument order at admin.rs:81: `record_sweep(reclaimed.removed, reclaimed.bytes)` → blobs=removed, bytes=bytes. Correct.

**40. main.rs:117 correct.

**41. routes/mod.rs: the sweep route is untimed; also the `TimeoutLayer` was on purge only in bounded — the diff moved the comment. purge still timed 10s — fine.

**42. Check `Sweeper::sweep` is `&self` while `run` holds mutex — but the route calls sweep directly, bypassing; already noted.

**43. `spawn_sweeps` — no jitter; fine.

**44. Any issue with `tokio::time::interval` first tick immediate: they say first tick is one interval away — actually `interval` fires the FIRST tick immediately! tokio::time::interval's first tick completes immediately (default). Wait: "The first tick completes immediately" — yes, tokio's `Interval` first tick fires right away. The doc comment at main.rs:101-102 claims "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 ticks immediately on first `tick().await`. So the proxy sweeps at startup! Consequence: a proxy sharing a blob directory or restarting sweeps immediately at startup; with min_age=1h and mtime-based age, blobs older than 1h over the ceiling get swept at startup — the claimed protection ("just started from sweeping a cache it has not begun to fill") doesn't exist. Actually wait — is this a defect with consequence? A startup sweep: on a fresh proxy it's harmless (empty). On a restarted proxy, it sweeps at boot, adding startup I/O load and — combined with the bypassed-lock? no, run() takes lock — it's just a sweep earlier than documented. Consequence: unnecessary immediate sweep at startup (minor) + doc false. Hmm, but combined with bug #5 (clear_partials), an immediate startup sweep is fine for incoming. The real consequence: the documented behavior doesn't hold; a proxy restart triggers an immediate sweep that, if it overruns, delays... minor. But wait — there's more: is it a defect that matters? If the interval sweep at startup runs while... eh. Let me verify tokio semantics: `tokio::time::interval(period)` — "The first tick completes immediately... default behavior". Yes, that's right: first tick is immediate. So the comment is factually wrong and the code sweeps at startup. Report as 🟡 or 🔵? The claim "keeps a proxy that has only just started from sweeping a cache it has not begun to fill" is incorrect; actual behavior: sweep at startup. Consequence: a restart of a busy proxy immediately sweeps (I/O at startup, and with mtime-age... could evict right at boot while the cache is being refilled... it's just one extra sweep). I'd report 🟡 medium? It contradicts an explicit safety claim in the code. The severity is moderate. I'll report 🟡 bug: main.rs:108 — the first `tick().await` returns immediately, so the first sweep runs at startup, contradicting the comment; use `interval_at(Instant::now() + period, period)` or `Delay` if startup sweep is unwanted.

Actually hold on, with MissedTickBehavior::Delay set — does that change the first tick? No; missed tick behavior only affects missed ticks after a delayed poll. First tick is still immediate. Confirmed.

**45. Now the sync blocking on runtime: I'll decide whether to include. The sweep.rs doc explicitly discusses and justifies synchronous walks (lines 14-18). For the HTTP route, `reclaim` is called in async handler — blocking a worker thread. With rt-multi-thread it stalls one worker; single-core deployments have 1 worker → all requests stall for the sweep duration. The doc acknowledges sync walk but doesn't address blocking the executor. It's a defensible 🔵/🟡 performance finding. Given "do not pad," and the code comments show the author weighed it, I'll include as 🔵 (the admin route blocks the tokio worker; should use spawn_blocking). Hmm, but the interval task also blocks a worker (same). I'll include one 🔵.

**46. sweep.rs:119 race (index read before blob walk) — TOCTOU deleting just-committed blobs. Let me detail: referenced() at line 92 (index snapshot), collect() at line 95 (blob walk). Any blob committed+linked between the two snapshots... a blob committed before collect but linked after referenced() → candidate, unreferenced in snapshot → removed + (index.get → None, forget no-op); the later-written index entry remains → stale entry → next request miss + refetch. Self-healing but a spurious eviction of a fresh artifact. Also blob committed during collect: appears if the leaf dir was read after commit; its link may come after referenced() → same. So the race window = duration of referenced() + collect(), i.e., the whole walk — could be seconds. With min_age not protecting (unreferenced ignores age), any fetch completing during a sweep window loses its blob. On a busy proxy, that's frequent: every artifact fetched during a sweep is deleted immediately after being cached. That's a notable bug! Combined with #5's in-flight deletion, sweeps actively destroy the work happening during them. Severity 🟠? Consequence: cache thrash during sweeps — artifacts fetched during the sweep get deleted → extra upstream fetches. Not a correctness break (self-heals). 🟡/🟠. I'll say 🟠 high for the pair? Let me rate individually: #5 (deletes in-flight temp files → failed requests, 500s) 🟠. #46 (deletes just-committed blobs → refetch, self-healing) 🟡.

Hmm, actually is #46 real? Order: `let index = referenced(...)` (line 92) THEN `collect` (line 95). Blob committed at T between 92 and 95... wait if committed after referenced but the index entry was linked even later — but link happens after commit in fetch(). Actually, could the index entry have been linked BEFORE referenced() and blob committed... no, commit precedes link. So: commit at T_c, link at T_l > T_c. Sweep: referenced at T_r, collect finishes at T_e. If T_c ∈ (T_r, T_e) and T_l > T_r → blob in candidates, not in index snapshot → deleted. Also if T_c < T_r but T_l > T_r: blob in candidates, link not in snapshot → deleted (window = referenced() duration, small). Also T_c > T_e: blob not seen, safe. So the vulnerable window spans from T_r through T_e (the entire blob walk), for fetches whose commit lands in it. On a store where the walk takes 10s and there's a fetch completing every second, each sweep deletes ~all of them. Real. 🟡 medium (spurious refetch) or 🟠. I'll go 🟡.

Hmm wait, one more subtlety: after deletion, forget() with index.get(hex)==None does nothing; but the fetch then does `app.store.link(...)` — cache.rs:163 link happens after commit; if the sweep's referenced() already ran, the link writes a NEW index entry after deletion → stale entry pointing at deleted blob → later request: resolve returns entry, open_blob None → miss → refetch. OK.

**47. `.env.example` 32 GiB = 34359738368 ✓.

**48. Docs ops mention "takes the same bearer token as the purge route" ✓.

**49. `SweepQuery.dry_run` with `#[serde(default)]` — `?dry_run=true` works. Also `?dry_run=false` fine. OK.

**50. One more: `main.rs` metrics recording for interval sweep uses `reclaimed.removed` which counts only blobs, not partials; partials' bytes not counted in `bytes` (Reclaimed doc says "Blobs only."). Consistent.

**51. `held` computed before sort; candidates include... fine.

**52. Overflow: `bytes += candidate.size` u64 sum of ≤ held — no overflow (held could overflow? sum of u64 sizes could overflow in theory → debug panic. `candidates.iter().map(size).sum()` — u64 addition overflow panics in debug. A store totaling > u64::MAX is impossible. Skip.

Now let me also double-check the axum route method for sweep: `.route("/v1/admin/cache/sweep", post(admin::sweep))` and purge is DELETE `/v1/admin/cache/{digest}`. In axum 0.8 (matchit 0.8), registering both `/v1/admin/cache/{digest}` and `/v1/admin/cache/sweep` — static/param conflict? matchit supports static segments taking precedence; but axum panics at router build if two routes conflict? Different paths (one has param) — matchit allows insertion of both; "sweep" static vs "{digest}" param at same position — matchit 0.8 allows this (insert conflicts only for exact same path). Yes, matchit allows static + param siblings; static wins. No panic. Fine.

Wait — one thing: does axum panic on "route conflicts"? Only for duplicate paths with different... `/v1/admin/cache/{digest}` (DELETE) vs `/v1/admin/cache/sweep` (POST) — allowed via `.route` on different routers merged; no conflict since path differs. Fine.

Now, does the merge of `bounded` and `untimed` work — both have state `()` and then `.with_state(app)` — pattern used previously. Fine.

**53. Timeout: purge route remains in bounded with 10s timeout — purge is quick. fine.

Now finalize findings list:

1. 🔴 sweep.rs:140 — `forget` runs even in dry run, deleting index entries for blobs not removed → dry run is destructive; next sweep removes the now-unreferenced blobs. (critical-ish. I'll go 🔴? Let me settle: The route documents dry_run as removing nothing. It removes index entries for every blob a sweep would remove — effectively scheduling their eviction and making them misses in the meantime. I'll rate 🔴 because the "safe" operation silently destroys cache state.) Hmm, alternatively 🟠. Let me think about what a "critical" is: crash, data loss, security hole. Deleting index entries = data destruction (recoverable via refetch). The bytes remain but become unreachable and get deleted by the next sweep. I'll go 🔴.

2. 🟠 metrics.rs:94 — values() order swaps bytes/blobs relative to COUNTERS, so both sweep counters render each other's numbers.

3. 🟠 sweep.rs:232 (clear_partials) — removes temp files of in-flight fetches in this process; commit's rename then fails (ENOENT) → in-flight downloads 500 during every sweep. Cite line 224 or 232. I'll cite 224.

4. 🟡 admin.rs:76 — on-demand route calls lock-free `sweep()` directly, bypassing the `running` mutex, so an on-demand sweep can overlap the interval sweep — the exact hazard the mutex and module doc exist to prevent.

5. 🟡 main.rs:108 — tokio interval's first tick fires immediately,
REASONING-ONLY LIMIT - 36K chars; cutting
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