sandbox:read-only (macOS Seatbelt)
-- reasoning --
I'm scanning the PR code for bugs. I spot that the candidate sort uses ascending age order despite the comment claiming "oldest first," which actually removes the newest blobs instead—it should sort by reverse age. I also notice the metrics values() order doesn't match the COUNTERS listing, with sweep_bytes_reclaimed and sweep_blobs_removed swapped.

Continuing the review, the `remaining >= self.max_bytes` condition looks like a minor off-by-one that removes one extra item at the exact ceiling. More concerning is the admin sweep route, which calls the sweeper synchronously without respecting the mutex meant to prevent concurrent sweeps, and does a blocking filesystem walk inside an async handler—both real problems. I'm also checking whether `Duration::from_hours` and `from_mins` are actually stable in the Rust version being targeted, since I recall the duration_constructors feature being unstable for some of these methods.

I found a real high-severity bug: dry-run mode still calls `forget` unconditionally, which actually deletes index entries even though nothing should be mutated during a dry run. There's also a risk that `clear_partials` deletes temp files still being actively written by an in-progress fetch, since unlinking a file mid-write can be problematic.

I also noticed that `Reclaimed.removed` inflates its count when a blob removal fails on the error path, still counting it as removed and reclaiming bytes it never actually freed—which then leads `forget` to delete the index entry for a blob that's actually still present, causing a reference mismatch.

Then there's a more serious race: if `store.rs` writes the blob file before creating its index entry, a sweep running in that window could delete a freshly written blob before it's ever indexed, since unreferenced blob removal doesn't respect `min_age`—that's worth flagging as a real bug. I also want to check that the new sweep route isn't blocking the async runtime, and confirm `main.rs` spawns the sweep task correctly against the shared app state.

I should now go read `store.rs`, `sweep.rs`, `routes/admin.rs`, `metrics.rs`, and `config.rs` directly to verify these suspicions.
I'll start by reading the new sweep module and its neighbours.
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↳ read_file: read pr/services/proxy/src/sweep.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/routes/admin.rs
└ read_file: read complete
↳ read_file: read pr/services/proxy/src/metrics.rs
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auto-compress is on at 85% but the context window of "anthropic/claude-opus-5" on openrouter is unknown, so this run will not compress - set AFI_SOURCE_OPENROUTER_CONTEXT_WINDOW (or pass --context-window) to enable it
-- reasoning --
I'm finding two bugs: metrics.rs has the values() order swapped from COUNTERS, so metrics get rendered under the wrong names, and sweep.rs sorts candidates ascending by age when the comment says "oldest first," meaning it actually evicts the newest blobs first. I'm continuing to look at sweep.rs for more issues.

The `remaining >= self.max_bytes` check is a minor off-by-one, removing one extra blob at the exact ceiling. More importantly, the admin route's sweep handler calls `sweep(dry_run)` directly rather than going through the locked `run()` path, breaking the one-at-a-time guarantee and allowing concurrent sweeps with the background sweeper — a real violation of the documented behavior. I'm also flagging that the synchronous filesystem walk runs directly on the async executor in both `run()` and the admin route without `spawn_blocking`, which can block the runtime thread for a long time.

That blocking call can easily exceed a 10-second timeout, stalling other requests on that worker. More seriously, `clear_partials` deletes files in `incoming` without checking age, which means it can rip out partial files from fetches that are actively downloading — since BlobWriter writes there during a fetch, an in-progress commit rename would then fail with ENOENT and the fetch would break, contradicting the doc's assumption that everything in `incoming` is abandoned. On top of that, `forget()` appears to be called unconditionally even during a dry run, meaning a supposedly non-destructive dry run actually deletes index entries — a genuine bug I need to flag.

Now I'm also noticing the unreferenced-blob removal logic could race with the commit-then-link sequence: a blob could get swept as "unreferenced" right between being committed and having its index entry linked, leading to an index entry pointing to a blob that no longer exists and causing spurious cache misses later.

I'm also checking whether `Duration::from_mins`/`from_hours` used in config.rs are actually stable APIs, trying to recall which Rust version stabilized the duration_constructors_lite feature.

Beyond that, I'm noting missing validation issues: cache_min_age isn't validated, sweep_interval zero isn't checked, and there's no guarantee cache_max_bytes exceeds max_artifact_bytes. I'm also confirming main.rs correctly clones the shared App via Arc when spawning sweeps, and looking at how Reclaimed.held gets computed from candidates.

Now I'm checking the routes module — the sweep route is registered as a POST under the admin cache path, alongside the purge route, which looks fine. In the sweep loop, remaining is compared against max_bytes using held for unreferenced deletions too, with proper subtraction as items are removed. The recursive collect over the index directory follows symlinks via metadata, which seems acceptable, though I'm flagging that age_of falling back to a default of zero on clock skew would treat an item as newest and inadvertently protect it from cleanup.

I should also verify that sweep properly accounts for held space including incoming partial uploads — that seems like a gap worth checking against config.rs, main.rs, routes/mod.rs, cache.rs, error.rs, and Cargo.toml's rust-version, plus any existing sweep tests.

I'm also examining how the Query extractor for dry_run behaves with malformed input — an invalid value like "yes" instead of "true" would trigger a 400 from the extractor itself rather than the app's structured JSON error, which is a minor inconsistency. I'm also noting that authorization happens after query extraction, so a malformed query short-circuits before auth is checked, though that's not a serious issue.
Now the config, main, router, and cache path.
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↳ read_file: read pr/services/proxy/src/config.rs
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↳ read_file: read pr/services/proxy/src/routes/mod.rs
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↳ read_file: read pr/services/proxy/src/routes/cache.rs
└ read_file: read complete
↳ read_file: read pr/services/proxy/src/main.rs
└ read_file: read complete
↳ read_file: read pr/services/proxy/Cargo.toml
└ read_file: read complete
-- reasoning --
I'm finding a real bug in metrics.rs where the COUNTERS array and the values() function list blobs_removed and bytes_reclaimed in swapped order, so the sweep_blobs_removed metric actually reports bytes instead. Now I'm checking sweep.rs's sort logic, which sorts candidates ascending by age.

Since ascending age puts the youngest blobs first, and the comment claims "oldest first," this inverts the intended eviction order — it skips newest blobs on the min_age check but then evicts the newest eligible blobs before older ones once they cross the threshold, essentially evicting in reverse-LRU order. It should sort descending or use Reverse to fix this. I'm now also noting a possible race condition in the blob-removal check where a blob not yet referenced in the index could be concurrently committed and then wrongly swept.

There's a real race: a blob is renamed into place before the index link is written, so a concurrent sweep could delete it in that gap since the unreferenced-blob path has no min_age grace period at all, unlike the comment implies. This could cause the store to serve a 500 error when a blob committed by an in-flight request goes missing before it can be opened, a legitimate medium/high severity defect worth flagging at the specific unreferenced-removal check.

Beyond that, `clear_partials` removes everything from the `incoming` directory including partial writes for downloads still in progress, and the doc comment's claim that files there are "not coming back" is simply false since active streams write there. On unix the writer keeps its file descriptor so writes still succeed, but the later commit rename fails with ENOENT, meaning any large in-flight download can be killed by a routine sweep -- this is a real high-severity bug affecting every download that happens to overlap a 15-minute sweep cycle.

I'm also noticing that `forget` gets called unconditionally on gone digests even during dry_run, where file removal is supposedly skipped but the index entries get deleted anyway -- that inconsistency needs to be checked further.

Actually thinking through the routing more carefully — since these two routers are merged rather than sharing one path, matchit should prioritize the static "sweep" segment over the "{digest}" wildcard, so no real conflict exists between the DELETE and POST routes.

The bigger issue I'm spotting is that the admin sweep handler calls the sweeper synchronously inside an async handler, doing a full filesystem walk of potentially tens of thousands of directories without spawn_blocking — this would block a runtime worker thread for the entire sweep. The same synchronous call happens again in the background sweeper task.

This ties to the main.rs comment noting sweeps of a large store can legitimately exceed ten seconds, meaning that worker thread would be stalled that whole time, stalling other concurrent futures like downloads — a genuine availability defect that should use tokio::task::spawn_blocking instead. There's also a separate bug where the admin reclaim route calls sweep directly rather than going through run(), bypassing the running-mutex guard meant to enforce only one sweep at a time, so two concurrent HTTP requests could race.

Beyond that, I'm noting bytes/removed metrics overstate on error since a failed remove_file still gets counted as removed, which is inconsistent with how clear_partials handles errors by skipping them — a minor issue. There's also unnecessary metadata computation for every index entry that's wasteful but not incorrect, and a symlink handling discrepancy where fs::metadata follows symlinks despite a comment claiming links are sized as links rather than as their targets.

This contradiction matters more because it creates an infinite recursion risk: if a symlink points to an ancestor directory, the collector treats it as a directory and follows it endlessly, causing a stack overflow. I'm flagging this at sweep.rs:164, then moving on to check whether Duration::from_hours and from_mins are stabilized Rust APIs.

I'm second-guessing myself on whether these constructors were stabilized — the existing test suite already uses them, but only in test code, so it's unclear if this is pre-existing tech debt or a legitimate stable API as of a recent Rust version.

Cache_min_age lacking validation isn't really a defect since zero is a valid value, and the dry-run documentation contradiction is already captured — I'm now checking whether the dry-run path skips rate limiting when it probably shouldn't.

I'm going through more edge cases: reclaimed partials counted in dry_run, metrics recording after sweeps, the blob sweep threshold not accounting for index/incoming dirs, and index collection logic — all seem fine. I'm now checking the security posture of the admin cache sweep route.

Rechecking the metrics ordering: the counters array and their values() are swapped between bytes-reclaimed and blobs-removed, meaning operators watching the documented bytes-reclaimed metric will actually see blob counts — a real bug worth flagging red/orange. I'm starting to rank severities, starting with dry-run forget deleting index entries as critical since it destroys data during what's documented as a no-op, risking a refetch storm.

Continuing the severity ranking: clear_partials removing in-flight partial writes is critical since every sweep interval could 500 concurrent downloads via an ENOENT-triggered commit error; ascending sort causing newest-first eviction inverts the intended LRU behavior; the swapped metrics and the synchronous walk blocking the async runtime are both notable performance/correctness issues; the admin route bypassing the mutex and the ungraced blob deletion racing the commit-link window round out the medium-severity findings, plus I'm noting fs::metadata's symlink-following behavior against its comment.

I'm also flagging the sweeper's pub method with #[must_use] being callable while ignoring the lock — that maps to the admin.rs:76 finding — plus the fact main.rs spawns sweep tasks before serving and never aborts them at shutdown, which the docs do address. I want to double-check the docs' claim about clearing dead-fetch partials against my actual finding, and also verify what `Reclaimed` derives.

Checking that gets confirmed, so the real gap is around clearing in-flight partial writes: since the blob store's temp path sits under the incoming directory and a writer holds an open file handle during long streaming downloads, a periodic sweep can race with those live writes, and the same race exists for index temp-file writes that get renamed into place — so both code paths are affected. I'm now compiling the full list of file:line references to cite for each finding — dry-run forget calls, live-partial removal, rename failures, sort logic, metrics, blocking admin calls, lock bypass, the unreferenced-race with the cache, and the symlink-following metadata call — before writing this up.
Read the sweep module, its callers, the store it walks, and the config/metrics wiring. Findings:

🔴 `bug` services/proxy/src/sweep.rs:140: `forget(&index, &gone)` runs unconditionally, and `gone` is filled at line 137 even when `dry_run` is true — so `POST /v1/admin/cache/sweep?dry_run=true` deletes every index entry naming a blob the sweep *would* have removed (`fs::remove_file(path)` at line 252 has no dry-run guard). The route documented as "reports what one would reclaim without removing anything" (docs/operations.md, admin.rs:87) silently unlinks the name index, turning the next build's hits into a full refetch storm against upstreams.

🔴 `bug` services/proxy/src/sweep.rs:232: `clear_partials` unlinks *every* file in `incoming` with no age or liveness test, but that directory holds the in-flight temporary of each running fetch (`BlobStore::temp_path`, store.rs:204) and of each index write (store.rs:147). A sweep — automatic every `CAIRN_SWEEP_INTERVAL`, 15m by default — deletes the temp of a download that is proceeding fine; the writer's `fs::rename(&temp, &target)` at store.rs:259 then fails with ENOENT and the client gets a 500 on a perfectly good artifact. The doc comment's premise ("a fetch that is not coming back") is untrue for anything currently streaming.

🟠 `bug` services/proxy/src/sweep.rs:102: `sort_by_key(|candidate| candidate.age)` sorts *ascending*, i.e. newest first, the opposite of the comment above it and of the eviction policy documented in config.rs:63. Combined with the `age >= min_age` gate at line 120, the sweep removes the youngest blobs that have just cleared the grace period and keeps the oldest, so the cache evicts exactly what a pipeline is still using. Needs `sort_by_key(|c| std::cmp::Reverse(c.age))`.

🟠 `bug` services/proxy/src/metrics.rs:94: `values()` returns `sweep_bytes_reclaimed` in slot 4 and `sweep_blobs_removed` in slot 5, but `COUNTERS` (lines 50-57) names slot 4 `cairn_proxy_sweep_blobs_removed_total` and slot 5 `..._bytes_reclaimed_total`. The two sweep counters are exported under each other's names, so the metric docs/operations.md tells operators to alert on reports a blob count, not bytes. Swap the two loads.

🟠 `performance` services/proxy/src/routes/admin.rs:76: `reclaim` calls the synchronous `Sweeper::sweep` directly on the runtime thread, as does `Sweeper::run` at sweep.rs:84 inside the spawned task. The module doc (sweep.rs:14-18) deliberately uses blocking `std::fs`, and routes/mod.rs:125 admits a sweep "legitimately takes longer than ten seconds" — that is a tokio worker blocked for the whole walk, stalling every download futures scheduled on it. Both call sites need `tokio::task::spawn_blocking`.

🟠 `bug` services/proxy/src/routes/admin.rs:76: the HTTP route bypasses the `running` mutex by calling `sweep()` instead of `run()`, so the "one sweep at a time" invariant the lock exists to keep (sweep.rs:10-12, 65-67) does not hold for the on-demand route. Two concurrent admin sweeps, or one racing the interval sweep, each compute `remaining` from a total the other is already shrinking and together take the store far below the ceiling.

🟡 `bug` services/proxy/src/sweep.rs:119: an unreferenced blob is removed with no grace period at all, but a miss commits the blob (cache.rs:151) before it writes the index entry (cache.rs:163) — during that window nothing points at it. A sweep landing there deletes the blob the request just stored; if it lands between the commit and `open_blob` (cache.rs:90) the request fails with the "already missing from the store" 500. The unreferenced branch should still respect `min_age`.

🟡 `bug` services/proxy/src/sweep.rs:164: `fs::metadata` follows symlinks, contradicting the comment directly above it (a symlink is counted at its target's size, not the link's) and, worse, making `collect` recurse into symlinked directories — a link pointing at an ancestor inside `CAIRN_BLOB_DIR` recurses until the stack overflows. Use `fs::symlink_metadata`.

🔵 `bug` services/proxy/src/sweep.rs:134: a failed `fs::remove_file` at line 126 only logs, then falls through to count the blob in `removed`/`bytes` and push it into `gone`. Space that was never reclaimed is reported to the operator and added to `cairn_proxy_sweep_bytes_reclaimed_total`, and its index entries are dropped though the blob is still there — `clear_partials` gets this right with its `continue` at line 234.

🔵 `bug` services/proxy/src/sweep.rs:120: `remaining >= self.max_bytes` evicts when the store is exactly at the ceiling, though `cache_max_bytes` is documented as "the most the blob store may hold" (config.rs:63); should be `>`.
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