From 39cde9f9a3d67c7bd8d457e0f4c31294d1c4b78b Mon Sep 17 00:00:00 2001
From: Jake Bailey <5341706+jakebailey@users.noreply.github.com>
Date: Fri, 12 Jun 2026 16:33:13 -0700
Subject: [PATCH] builder: retry cached archive renames on Windows (#5462)

---
 builder/library.go          |  2 +-
 builder/robustio_other.go   |  9 ++++++++
 builder/robustio_windows.go | 44 +++++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 1 deletion(-)
 create mode 100644 builder/robustio_other.go
 create mode 100644 builder/robustio_windows.go

diff --git a/builder/library.go b/builder/library.go
index 73fa2545f..1f8abce96 100644
--- a/builder/library.go
+++ b/builder/library.go
@@ -218,7 +218,7 @@ func (l *Library) load(config *compileopts.Config, tmpdir string) (job *compileJ
 				return err
 			}
 			// Store this archive in the cache.
-			return os.Rename(f.Name(), archiveFilePath)
+			return robustRename(f.Name(), archiveFilePath)
 		},
 	}
 
diff --git a/builder/robustio_other.go b/builder/robustio_other.go
new file mode 100644
index 000000000..fd939bffd
--- /dev/null
+++ b/builder/robustio_other.go
@@ -0,0 +1,9 @@
+//go:build !windows
+
+package builder
+
+import "os"
+
+func robustRename(oldpath, newpath string) error {
+	return os.Rename(oldpath, newpath)
+}
diff --git a/builder/robustio_windows.go b/builder/robustio_windows.go
new file mode 100644
index 000000000..22d5c2bab
--- /dev/null
+++ b/builder/robustio_windows.go
@@ -0,0 +1,44 @@
+package builder
+
+import (
+	"errors"
+	"math/rand"
+	"os"
+	"syscall"
+	"time"
+)
+
+const robustRenameTimeout = 2 * time.Second
+
+func robustRename(oldpath, newpath string) error {
+	var bestErr error
+	start := time.Now()
+	nextSleep := time.Millisecond
+	for {
+		err := os.Rename(oldpath, newpath)
+		if err == nil || !isEphemeralRenameError(err) {
+			return err
+		}
+		if bestErr == nil {
+			bestErr = err
+		}
+		if d := time.Since(start) + nextSleep; d >= robustRenameTimeout {
+			return bestErr
+		}
+		time.Sleep(nextSleep)
+		nextSleep += time.Duration(rand.Int63n(int64(nextSleep)))
+	}
+}
+
+func isEphemeralRenameError(err error) bool {
+	var errno syscall.Errno
+	if errors.As(err, &errno) {
+		switch errno {
+		case syscall.Errno(2), // ERROR_FILE_NOT_FOUND
+			syscall.Errno(5),  // ERROR_ACCESS_DENIED
+			syscall.Errno(32): // ERROR_SHARING_VIOLATION
+			return true
+		}
+	}
+	return false
+}