fix(compression): correctness findings from compression audit#2803
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ValentaTomas
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The alignment check in WriteAtWithoutLock only verifies that the write is at least one block long but does not ensure the total length is a multiple of the block size, which could lead to a panic when slicing the buffer for the final block; the condition should be updated to require that len(b) is an exact multiple of c.blockSize.
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Cursor Bugbot has reviewed your changes and found 1 potential issue.
Autofix Details
Bugbot Autofix prepared a fix for the issue found in the latest run.
- ✅ Fixed: Idle timer not reset after successful Read completion
- Added timer.Reset(r.idle) after successful reads to give consumers the full idle budget between reads instead of reducing it by the read duration.
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Preview (f40a25dca8)
diff --git a/packages/shared/pkg/storage/storage_google.go b/packages/shared/pkg/storage/storage_google.go
--- a/packages/shared/pkg/storage/storage_google.go
+++ b/packages/shared/pkg/storage/storage_google.go
@@ -303,6 +303,8 @@
n, err := r.ReadCloser.Read(p)
if err != nil {
r.timer.Stop()
+ } else {
+ r.timer.Reset(r.idle)
}
return n, err
}You can send follow-ups to the cloud agent here.
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Cursor Bugbot has reviewed your changes and found 1 potential issue.
Autofix Details
Bugbot Autofix prepared a fix for the issue found in the latest run.
- ✅ Fixed: GCS ErrObjectNotExist check never matches in peerSeekable
- Added error translation in openRangeReader to wrap cloud library ErrObjectNotExist with local package sentinel, matching the pattern used in Size() and WriteTo() methods.
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Preview (3750f3cd4c)
diff --git a/packages/shared/pkg/storage/storage_google.go b/packages/shared/pkg/storage/storage_google.go
--- a/packages/shared/pkg/storage/storage_google.go
+++ b/packages/shared/pkg/storage/storage_google.go
@@ -274,6 +274,10 @@
if err != nil {
cancel()
+ if errors.Is(err, storage.ErrObjectNotExist) {
+ return nil, fmt.Errorf("failed to create GCS range reader for %q at %d+%d: %w", o.path, off, length, ErrObjectNotExist)
+ }
+
return nil, fmt.Errorf("failed to create GCS range reader for %q at %d+%d: %w", o.path, off, length, err)
}You can send follow-ups to the cloud agent here.
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Reviewed commit: ef6431c76c
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Cursor Bugbot has reviewed your changes and found 1 potential issue.
Autofix Details
Bugbot Autofix prepared a fix for the issue found in the latest run.
- ✅ Fixed: Concurrent reads lose transition retry
- Removed the conditional CAS check so all concurrent goroutines in the retry window receive PeerTransitionedError and can retry after header swap.
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@cursor push 2c923d7144
Preview (2c923d7144)
diff --git a/packages/orchestrator/pkg/sandbox/template/peerclient/seekable.go b/packages/orchestrator/pkg/sandbox/template/peerclient/seekable.go
--- a/packages/orchestrator/pkg/sandbox/template/peerclient/seekable.go
+++ b/packages/orchestrator/pkg/sandbox/template/peerclient/seekable.go
@@ -145,9 +145,8 @@
if errors.Is(err, storage.ErrObjectNotExist) {
at := s.transitionAt.Load()
if at != 0 && time.Since(time.Unix(0, at)) < postTransitionRetryWindow {
- if s.transitionAt.CompareAndSwap(at, 0) {
- return nil, &storage.PeerTransitionedError{}
- }
+ s.transitionAt.CompareAndSwap(at, 0)
+ return nil, &storage.PeerTransitionedError{}
}
}You can send follow-ups to the cloud agent here.
jakubno
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May 25, 2026
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Reviewed commit: 27eeb26591
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- Mark a draft as ready
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Cursor Bugbot has reviewed your changes and found 1 potential issue.
Bugbot Autofix prepared a fix for the issue found in the latest run.
- ✅ Fixed: Stat failure deletes valid cache
- Modified logic to only remove cached files on confirmed size mismatch, treating Stat failures as transient errors that fall through to cache miss without deletion.
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@cursor push 93e492f915
Preview (93e492f915)
diff --git a/packages/shared/pkg/storage/storage_cache_seekable_compressed.go b/packages/shared/pkg/storage/storage_cache_seekable_compressed.go
--- a/packages/shared/pkg/storage/storage_cache_seekable_compressed.go
+++ b/packages/shared/pkg/storage/storage_cache_seekable_compressed.go
@@ -32,23 +32,29 @@
// Cache hit: open compressed frame from NFS, validate size, wrap with decompressor.
// On size mismatch the file is corrupt (truncated write, disk full), drop it.
if f, err := os.Open(path); err == nil {
- if fi, statErr := f.Stat(); statErr == nil && fi.Size() == int64(r.Length) {
- recordCacheRead(ctx, true, int64(r.Length), cacheTypeSeekable, cacheOpOpenRangeReader)
- timer.Success(ctx, int64(r.Length))
+ if fi, statErr := f.Stat(); statErr == nil {
+ if fi.Size() == int64(r.Length) {
+ recordCacheRead(ctx, true, int64(r.Length), cacheTypeSeekable, cacheOpOpenRangeReader)
+ timer.Success(ctx, int64(r.Length))
- decompressed, err := newDecompressingReadCloser(f, frameTable.CompressionType())
- if err != nil {
- f.Close()
+ decompressed, err := newDecompressingReadCloser(f, frameTable.CompressionType())
+ if err != nil {
+ f.Close()
- return nil, fmt.Errorf("decompress cached frame: %w", err)
+ return nil, fmt.Errorf("decompress cached frame: %w", err)
+ }
+
+ return withNFSGauge(ctx, decompressed), nil
}
-
- return withNFSGauge(ctx, decompressed), nil
+ f.Close()
+ _ = os.Remove(path)
+ recordCacheReadError(ctx, cacheTypeSeekable, cacheOpOpenRangeReader,
+ fmt.Errorf("cached frame %s size mismatch", path))
+ } else {
+ f.Close()
+ recordCacheReadError(ctx, cacheTypeSeekable, cacheOpOpenRangeReader,
+ fmt.Errorf("cached frame %s stat failed: %w", path, statErr))
}
- f.Close()
- _ = os.Remove(path)
- recordCacheReadError(ctx, cacheTypeSeekable, cacheOpOpenRangeReader,
- fmt.Errorf("cached frame %s invalid", path))
} else if !os.IsNotExist(err) {
recordCacheReadError(ctx, cacheTypeSeekable, cacheOpOpenRangeReader, err)
}You can send follow-ups to the cloud agent here.
Reviewed by Cursor Bugbot for commit 393ddbe. Configure here.
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jakubno
reviewed
May 25, 2026
jakubno
approved these changes
May 25, 2026
- reject misaligned writes in Cache.WriteAtWithoutLock to avoid OOB slice - cap V4 header LZ4 decompression at the size prefix - drop corrupt compressed cache entries on size mismatch - retry GCS 404 within post-transition window with backoff - use per-Read idle timeout on GCS range reads
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The API takes ~20s after starting to listen before its readiness gate clears (cluster init), so the default 30s polling window can lose the race and report 'API failed to become healthy in time' on slower runners. Bump just the API leg to 60s.
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Compression-audit correctness fixes:
Cache.WriteAtWithoutLock