sandbox:read-only (macOS Seatbelt)
-- reasoning --
I'm examining the diff for defects, focusing on the new sweep logic in sweep.rs, route registration and timeouts, metrics ordering, config validation, and whether Sweeper::sweep is being called synchronously from an async context, which would block the executor. I'm now tracing how spawn_sweeps in main.rs invokes the app's sweep function.

Regardless of intent, blocking the runtime thread for a filesystem walk across tens of thousands of files is a legitimate performance defect. Both `spawn_sweeps` and the `admin::sweep`/`reclaim` request handler call the synchronous `sweep()` directly rather than offloading via `spawn_blocking`, meaning a request-handling thread can stall other requests for the duration of the walk -- undermining the async model despite the route being marked "untimed." I'm now pinning down the exact file and line locations for these calls, starting with the synchronous sweep invocation inside `run()` in sweep.rs.

I'm also checking whether the `Metrics::values()` ordering matches the `COUNTERS` array ordering, since a mismatch there would misattribute values to the wrong counter names -- I need to look at the full original file to confirm the exact sequence of entries in both.
└ 1297 tok ·  79.3 tok/s · 19K ctx · 4510ms ttft · 16.4s wall
↳ read_file: read pr/services/proxy/src/metrics.rs
└ read_file: read complete
auto-compress is on at 85% but the context window of "anthropic/claude-sonnet-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 spotting a bug: the order returned by `values()` swaps sweep_bytes_reclaimed and sweep_blobs_removed compared to the COUNTERS array order, so the indices don't line up correctly.

This confirms the render will mislabel these two metrics, reporting bytes under the blobs-removed name and vice versa — ironically the exact class of bug the code's own comment warns against. That's a real correctness issue for metrics output.

I should now check the other files — sweep.rs, admin.rs, config.rs, main.rs, routes/mod.rs — for similar issues, starting with sweep.rs's removal condition logic around max_by comparisons.

Looking closer at the sort ordering: unreferenced blobs get removed unconditionally regardless of age, while size-based eviction requires meeting the minimum age threshold, and both selection paths flow through the same sorted candidate list. But I need to double check the sort direction — since it sorts ascending by age and larger age values mean older blobs, ascending order actually puts the newest blobs first and oldest last, which contradicts the comment claiming "oldest first."

This looks like a genuine bug: the sort should be reversed so eviction targets the truly oldest blobs first, not the newest ones.  I want to reread the code once more to make sure I'm not misreading the sort direction before concluding this.
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↳ read_file: read pr/services/proxy/src/sweep.rs
└ read_file: read complete
-- reasoning --
I'm checking potential bugs in the removal logic—confirming that unreferenced blobs get removed correctly regardless of size threshold, and now examining how the `remaining` counter tracks against the `held` value as blobs are processed oldest-first.

Actually, I'm second-guessing the sort order: candidates are sorted ascending by age, but if age means time-since-modified, ascending order would put the newest files first, not the oldest, which seems to contradict the intended "oldest first" behavior described in the comment.

Right, so sorting ascending by age puts newest first, meaning the loop hits young blobs first and skips most of them due to the min_age grace period, cycling through until it reaches genuinely old ones. So functionally it may still end up removing the oldest blobs eventually, but the order is inefficient and conceptually inverted from what the comment claims.

Since removal stops once the remaining size drops below the threshold, the sort order actually determines which blobs get evicted first — and ascending age means the barely-old blobs get evicted while truly ancient ones stick around, backwards from a proper LRU eviction. That confirms the sort key on line 102 needs to be reversed, since larger age values mean older files, not newer ones.

That's the fix needed to sort by age descending instead. The rest of the eviction logic looks sound to me: held size correctly excludes partials, the scanned count conversion is safe, and the removal loop's threshold check works fine, so the sorting order is really the only defect worth flagging.

I'm also scanning for concurrency issues between sweep and purge operations, but there isn't enough context to call that a concrete bug. Checking main.rs, config.rs, and admin.rs next -- nothing stands out there either; cache_min_age of zero being valid and reclaim using the app state both seem fine.

Wait, I notice the admin route's reclaim function calls the sweeper's sweep method directly instead of going through its run() method, which is the one that acquires the running lock. That means an on-demand sweep from the admin endpoint bypasses the "one active sweep at a time" guarantee that run() is supposed to enforce -- a real bug worth flagging.

Checking the actual `run()` implementation confirms it only locks the mutex and hardcodes a non-dry-run sweep, never accepting a dry_run parameter. That means the admin route's direct call to `sweep(dry_run)` isn't just skipping the lock for convenience -- it's structurally necessary since `run()` can't even express a dry-run request, which means both the dry-run and real on-demand sweeps triggered via the admin endpoint entirely bypass the mutex protecting against the background scheduler.
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↳ read_file: read pr/services/proxy/src/routes/admin.rs
└ read_file: read complete
-- reasoning --
I'm spotting a real bug: the on-demand sweep route calls `sweeper.sweep()` directly instead of going through `run()`, which is what actually acquires the mutex lock guaranteeing only one sweep runs at a time. That means the admin HTTP route can bypass this safety mechanism entirely.

This means a background timer-triggered sweep and an admin-triggered sweep could run concurrently, violating the "one sweep at a time" invariant documented in the code and potentially causing over-deletion if both computations rely on stale totals. I want to confirm this by checking the exact definitions of `sweep` and `run` in sweep.rs.
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↳ read_file: read pr/services/proxy/src/sweep.rs
└ read_file: read complete
-- reasoning --
I found a key bug: the admin sweep route calls the sweeper's sweep function directly instead of going through its run method, so it skips the mutex lock that the scheduled background sweep uses. That means an on-demand admin sweep could run concurrently with the scheduled sweep, since only the scheduled path actually takes the lock.

That's a solid concrete bug to flag: services/proxy/src/routes/admin.rs:76 calls app.sweeper.sweep() directly instead of app.sweeper.run(), bypassing the mutex.

Now checking metrics.rs, I notice the COUNTERS array lists metrics in one order (cache_hits, cache_misses, upstream_failures, policy_refusals, sweep_blobs_removed, sweep_bytes_reclaimed) but the values() function appears to return them with the last two swapped, which would mean blobs_removed_total and bytes_reclaimed_total get their values crossed when zipped together during rendering. I want to verify this by tracing through the exact indices.

Confirming it: values() returns sweep_bytes_reclaimed at index 4 and sweep_blobs_removed at index 5, which is reversed relative to COUNTERS, so this is a genuine high-severity bug in metrics.rs around lines 88-96 -- the two sweep counters are actually mislabeled in the exported metrics, ironically the doc comment even warns about exactly this kind of mismatch. Now I want to move on and check config.rs's default duration function and main.rs for similar issues.

Let me also verify whether `Duration::from_hours` and `from_mins` are actually stable in the Rust version this project targets, since those were only recently stabilized -- I should check Cargo.toml for the edition and minimum supported Rust version.
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↳ read_file: read pr/services/proxy/Cargo.toml
└ read_file: read complete
-- reasoning --
I'm checking the order of items in the COUNTERS array versus what values() returns—it looks like sweep_bytes_reclaimed and sweep_blobs_removed might be swapped, so I want to verify their declared order against the actual definition.

Confirming this: COUNTERS index 4 has the label "sweep_blobs_removed_total" but values()[4] returns sweep_bytes_reclaimed's value, and vice versa for index 5. This is a genuine, provable bug — the metric labels and their corresponding values are swapped when zipped together.

Now I'm checking the sweep candidate sorting logic. The comment claims "oldest first" ordering, but sorting ascending by age (a Duration) puts the smallest duration — meaning most recently modified, i.e. newest — first, which contradicts the stated intent. This looks like it could be another real bug where the sort order is backwards from what's documented.

This actually looks like a real inverted bug: since ascending sort by age puts smallest duration (most recently modified) first, iterating front-to-back hits the newest blobs first, meaning the eviction logic removes newest instead of oldest when over capacity - exactly backwards from the intended LRU policy.

So confirming the eviction actually deletes newest-first since it stops once under threshold but sorted ascending by age, contradicting the documented "evict oldest first" policy. This is a genuine high-severity bug: the sort key needs to be reversed so oldest items get evicted first, otherwise freshly-fetched packages get evicted while stale ones stay, causing repeated cache misses on actively-used artifacts.

I'm also noticing the on-demand sweep route calls the sweeper's reclaim function synchronously inside an async handler rather than offloading it to a blocking task, so this I/O-heavy operation could block the async runtime.  The module doc does note this is deliberate for scheduling-cost reasons, so it may be an intentional tradeoff rather than an oversight.  Still worth flagging: spawn_sweeps locks a mutex and calls sweep synchronously without spawn_blocking, blocking a tokio worker thread and delaying other tasks during long directory walks—even if documented as acceptable.  I'm leaning toward not reporting this since it's a deliberate architectural tradeoff on a multi-threaded runtime, though I'll note it as a lower-priority concern.

Now I'm double-checking whether `Duration::from_hours` and `Duration::from_mins` are actually stable in Rust, since these are newer additions that may not have landed in the standard library yet depending on the toolchain version being targeted.

Since MSRV isn't specified, I can't verify compatibility for certain, so I'll leave that as an open question. Separately, I notice `cache_min_age` lacks the zero-check validation that `sweep_interval` has, but a zero value there is actually a legitimate config choice, not a bug.

Query extraction failures already return 400 automatically via Axum before reaching the handler, and authorization ordering in reclaim matches purge's pattern of checking auth before doing work, so both look consistent. Now I want to trace through config.rs's validation logic for cache_min_age more thoroughly and cross-reference store.rs's digest/hex length handling with what admin expects for collection operations, particularly the IndexEntry struct's digest field and Digest::parse.
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↳ search_files: search pr/services/proxy/src/store.rs for blobs/sha256|\"index\"|\"incoming\"|IndexEntry|struct BlobStore
└ search_files: search complete
-- reasoning --
I want to check store.rs to understand the layout, the index resolve function, and how blob paths are constructed from hex hashes with nested directories.
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↳ read_file: read pr/services/proxy/src/store.rs
└ read_file: read complete
-- reasoning --
I'm confirming the blob path structure with two-level hex subdirectories works correctly for the sweeper's recursive walk, since it extracts the filename from the candidate path. Next I want to check the remove() function in store.rs to see if it also updates the index, comparing that behavior with how sweep's forget works.
└ 226 tok ·  38.7 tok/s · 30K ctx · 5391ms ttft ·  5.8s wall
↳ read_file: read pr/services/proxy/src/store.rs
└ read_file: read complete
-- reasoning --
I'm confirming that sweep.rs stores blobs using a two-level nested directory structure based on the sha256 hash, and that collect walks recursively grabbing the hex filename as the candidate. Now I'm digging into a potential bug in the remove logic within sweep, specifically how it checks remaining bytes against max_bytes.

Tracing through this logic, since candidates are sorted oldest-first, removal correctly proceeds until remaining drops below max_bytes, while unreferenced/orphaned blobs get removed unconditionally regardless of the byte threshold - that part matches the intended design. But I'm spotting a real defect: the admin sweep route calls `sweeper.sweep(dry_run)` directly rather than going through `run()`, which is what acquires the mutex enforcing "one sweep at a time." This means the on-demand admin route bypasses that invariant entirely, so a background sweep and an admin-triggered sweep could run concurrently.

This is significant because the module's own documentation explicitly warns against concurrent sweeps corrupting reclaimed totals or racing on the same directory. I want to verify by checking the exact function signatures in sweep.rs to confirm `run()` takes the lock before calling `sweep()` internally.

Now I'm checking a few smaller things: whether dry-run mode correctly simulates quota reduction without actually deleting files (it does, updating the remaining count via saturating subtraction), whether there are any CSRF concerns on the sweep endpoint (not applicable here), and whether the cache_min_age config value is validated against zero.

Zero seems like a legitimate value here, meaning any blob would be immediately eligible, so that's not a bug. I'm also noting the docs check for a zero sweep interval but not a zero min age, which isn't necessarily problematic.

Then I turn to the sweep spawning logic in main.rs, specifically the use of MissedTickBehavior::Delay with tokio's interval. I'm recalling that tokio's interval fires its first tick immediately upon creation rather than waiting a full period, which could affect the timing assumptions in how sweeps get scheduled.

Checking tokio's documented semantics confirms the first tick does complete immediately, not after a delay - but the comment in main.rs explicitly states the first tick is "one interval away" to prevent sweeping a freshly-started proxy's not-yet-filled cache. This is a real discrepancy: the code's actual behavior contradicts its own documented intent, since an immediate first tick means the proxy could sweep a cache it just started populating.
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↳ read_file: read pr/services/proxy/src/main.rs
└ read_file: read complete
-- reasoning --
I notice the on-demand sweep route calls the sweeper's sweep function directly rather than through the locked run method, meaning it bypasses the running mutex entirely. This lets it execute concurrently with a background sweep, violating the documented "one sweep at a time" invariant. I want to confirm this by checking the code more closely.

Checking Sweeper::run's signature confirms it only exposes run(&self) with dry_run hardcoded to false, so there's no locked path that supports a dry_run flag — meaning the admin route, needing dry_run, has no choice but to call sweep() directly and skip the mutex entirely. That confirms the concurrency bug, with the exact lines being sweep.rs's run definition and admin.rs's bypassing call site.

Now I want to check something else — whether the metrics counters' ordering in the values() call matches the expected order.

Comparing the counter definitions against the values() output order, I find sweep_bytes_reclaimed and sweep_blobs_removed are swapped at indices 4 and 5 — exactly the failure mode the doc comment warned about, where a counter's value gets attributed to the wrong metric name. This is a real, high-severity bug worth flagging.

Now I'm checking config.rs for validation gaps and confirming whether Duration::from_hours/from_mins are stable in current Rust, since that affects whether the code would even compile.
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↳ read_file: read pr/services/proxy/src/config.rs
└ read_file: read complete
-- reasoning --
I'm trying to recall whether Duration::from_hours and from_mins are actually stabilized in Rust, since I'm not fully certain of their status and want to verify before relying on them.
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↳ search_files: search pr/services/proxy/src/config.rs for from_hours|from_mins|parse_duration
└ search_files: search complete
-- reasoning --
I'm setting aside the from_hours/from_mins stability question since it's not central to the review, and instead digging into the sweep logic's removal order—checking how it decrements remaining bytes oldest-first while comparing against the max_bytes and min_age thresholds.

Looking closer, I suspect a bug: age represents time since last modified, so a larger value means older. But the code sorts candidates ascending by age, which puts the newest files first and the oldest last—the opposite of what the comment claims ("oldest first, so blobs nothing has wanted for longest go first"). That ordering mismatch could mean the sweep removes recently-touched files before truly stale ones.

Actually, tracing through the removal loop more carefully: since newer items (with age below min_age) get skipped by the second condition anyway, the ascending sort order means the loop naturally walks past young items until it reaches ones old enough to qualify, and removes those in the order encountered—so the practical effect may still favor removing older items first, just via the skip logic rather than the sort order itself.

Newer items are already protected by the min_age check regardless of order, but among items old enough to remove, ascending order means the sweep removes the "youngest of the old" ones first and could stop before reaching the truly ancient blobs once it drops under the byte ceiling—violating the intended oldest-first LRU eviction semantics.

I found the concrete bug: the candidates are sorted ascending by age, but the comment right above explicitly says to process oldest first. Since higher age means older, an ascending sort actually puts the newest files first — the fix would be sorting descending (e.g., using Reverse or flipping the comparison), so this is a single clear line-level defect worth reporting.

This is a real, high-severity bug because it defeats the entire LRU eviction mechanism: instead of evicting truly stale blobs, it will repeatedly evict recently-used ones that just crossed the grace threshold while leaving genuinely ancient artifacts in place indefinitely, hurting cache effectiveness and disk reclamation. This definitely undermines the core purpose of the feature and is worth flagging.

Now I'm checking whether `run()` calls the synchronous `sweep(false)` directly inside an async context while holding a tokio Mutex, since sweep walks the whole directory tree and removes files without using `spawn_blocking`. That could block the async runtime's worker thread, though the sweep.rs doc comment argues the synchronous walk is cheap enough that spawning wouldn't be worth the scheduling overhead.

Even though the docs justify avoiding overhead from repeated blocking-pool round trips, this still means the tokio worker thread is pinned synchronously for the whole sweep duration, potentially stalling other tasks queued on that worker—like health checks or requests—even if the multi-threaded runtime can migrate some work elsewhere. So the documented rationale addresses efficiency but doesn't fully resolve the correctness risk of blocking shared executor threads for large sweeps.

This risks blocking readiness/health endpoints or other requests if it's the only worker thread. The code comment justifies avoiding per-entry async fs scheduling overhead, but that's a different issue than blocking the whole executor for the sweep's duration—the real fix should be wrapping the sweep in spawn_blocking.

ocking whole runtime for potentially tens of thousands of files, which could stall in-flight requests -- worth flagging with moderate confidence.

Checking other issues now: the async `run()` holds a tokio Mutex across a synchronous blocking sweep call, but the deeper issue remains the executor-thread blocking already noted. More significantly, `admin::sweep`'s `reclaim` function is invoked directly by the route handler without going through `run()`, bypassing the `running` mutex that's supposed to prevent concurrent sweeps -- meaning simultaneous route calls or a route call overlapping with a periodic sweep could race.

Confirming this against the module docs, which explicitly state "one sweep at a time" is required to avoid two sweeps double-counting removals and driving the store below the intended ceiling. Looking at admin.rs, the code calls `app.sweeper.sweep(dry_run)` directly rather than through `run()`, confirming this is a real synchronization bug.

The admin handler calls `sweep()` directly without acquiring the mutex, completely bypassing the concurrency guard that `run()` uses. That's the core defect—a race allowing two concurrent sweeps, exactly what the documentation warns breaks the algorithm.

Confirming the admin path calls the sync `sweep(dry_run)` method directly, with zero locking against the periodic sweeper. While a dry-run is relatively harmless since it doesn't mutate anything, a concurrent real sweep triggered by admin alongside the periodic sweep is a genuine race — both would independently walk the directory, compute "remaining" candidates from their own stale snapshot, and remove files until under the ceiling, risking double-removal or over-pruning beyond intended limits.

Checking forget() and index cleanup after sweep looks fine since the index was built before blob removal. Collect() recursion over directories is generic and correct, and the Reclaimed.held semantics match the documented "held before sweep" meaning. Scanned count conversion looks fine too, so I'm moving on to verify the record_sweep signature and its parameters.

I'm tracing that record_sweep calls in main.rs and admin.rs both pass (removed, bytes) matching the (blobs, bytes) parameter order correctly. Now I'm verifying the ordering of the counters array against COUNTERS to make sure the sweep metrics land at the right indices.

But now I'm finding a mismatch: COUNTERS lists blobs_removed before bytes_reclaimed, but the values() function returns them in the opposite order, meaning the exposed metric names will report the wrong values swapped between blobs and bytes.

Confirmed: the two new entries are swapped between the name array and the values() array at lines 94-95, so `sweep_blobs_removed_total` will actually report the bytes-reclaimed value and vice versa. This is a concrete, verifiable defect in metrics.rs.

I'm flagging it 🟠 high since it directly contradicts the monitoring guidance in docs/operations.md, which tells operators to watch `sweep_bytes_reclaimed_total` — but that value will actually be the blob count. Adding this to my defect list as item 1, then moving to check sweep.rs's sort_by_key ordering next.

Also noting a third defect: the on-demand sweep route bypasses the `running` mutex, letting concurrent sweeps occur despite the code's explicit "one sweep at a time" invariant. I'll skip flagging the Duration::from_hours/from_mins usage in config.rs since I'm not certain it's actually unstable in the target Rust version — better to verify the sort_by_key ordering logic more carefully before finalizing.

Since cache_min_age is a Duration, it's always non-negative, so that's not an issue, though there's no check against sweep_interval which isn't necessarily a bug. Checking the admin routes, the sweep and purge endpoints look properly registered and both seem to use the same authorization logic.

I'm confident in the three defects I've found. The doc comment in sweep.rs confirms the intended oldest-first eviction, which contradicts the actual sort order I found. The impact is significant: sweep will evict blobs that just barely aged past the minimum threshold before removing truly stale ones, meaning recently-used blobs get purged first while ancient cached data lingers—causing unnecessary churn and worse cache hit rates than the LRU design intends.

This directly contradicts the documented behavior in architecture.md and the code's own comments claiming "oldest first" eviction, confirming a genuine high-severity bug that undermines the sweep feature's core purpose and could cause repeated eviction of frequently-used data.

Next I'm flagging the metrics.rs swap issue, where blob removal counts appear to be reported under the wrong metric name, mixing up byte and count values.

Then there's a concurrency bug where admin-triggered sweeps bypass the mutex meant to enforce single sweep execution, risking concurrent sweeps that could push storage far below the intended ceiling—critical severity given the documentation's guarantees around single-sweep execution.

Now I'm pinning down exact line numbers for each issue: the counters block and mismatched values in metrics.rs, and the corresponding locations in admin.rs and sweep.rs.

The atomics themselves store correct values -- the bug is purely that `values()` returns them in the wrong order relative to COUNTERS, since render() zips names with values positionally: index4 expects blobs_removed but gets bytes_reclaimed, and vice versa for index5.
Reviewed `pr/services/proxy/src/sweep.rs`, `pr/services/proxy/src/metrics.rs`, `pr/services/proxy/src/routes/admin.rs`, `pr/services/proxy/src/main.rs`, `pr/services/proxy/src/config.rs`, `pr/services/proxy/src/store.rs`, plus the docs/env changes.

🔴 `bug` services/proxy/src/routes/admin.rs:76: `reclaim` calls `app.sweeper.sweep(dry_run)` directly instead of the async `Sweeper::run` (sweep.rs:82-85), so it never takes the `running` mutex that sweep.rs's own module doc (sweep.rs:11-13) says is required: "Two of them over one directory would each decide what to remove from a total the other is already changing... they would take the store far below the ceiling either was aiming at." A `POST /v1/admin/cache/sweep` that lands while the periodic sweep (main.rs:116, which does use `run()`) is in flight, or two concurrent admin requests, run two unsynchronized sweeps over the same directory concurrently, defeating the exact invariant the code is built around.

🟠 `bug` services/proxy/src/sweep.rs:102: `candidates.sort_by_key(|candidate| candidate.age)` sorts ascending, i.e. newest (smallest age) first, but the comment directly above (lines 100-101) and the documentation added in docs/architecture.md:55 and docs/operations.md both state the sweep "removes the oldest blobs" to reclaim space. Since the loop never breaks and removes for the capacity reason in list order, once several blobs are past `min_age` the sweep evicts the ones that *just* crossed the grace period first and leaves genuinely ancient blobs cached longest - the opposite of the advertised LRU-style eviction, causing needless refetch churn on blobs that are merely old-enough while truly stale blobs sit untouched.

🟠 `bug` services/proxy/src/metrics.rs:94: `values()` returns `sweep_bytes_reclaimed` at index 4 and `sweep_blobs_removed` at index 5, but `COUNTERS` (metrics.rs:50-57) lists `cairn_proxy_sweep_blobs_removed_total` at index 4 and `cairn_proxy_sweep_bytes_reclaimed_total` at index 5. `render()` zips the two arrays positionally, so the exposed Prometheus metrics are swapped: the "blobs removed" metric reports byte counts and the "bytes reclaimed" metric reports blob counts, silently breaking the exact `cairn_proxy_sweep_bytes_reclaimed_total` alerting the PR's own docs/operations.md change tells operators to watch.
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