From cb593bf5eefa65feac7349360fd7e1278eabb948 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 10 Feb 2026 21:55:26 +0000
Subject: [PATCH 1/2] Initial plan


From 8be344074bf4d90f6ac8da9d4bdd09cb90b66bbf Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 10 Feb 2026 22:04:39 +0000
Subject: [PATCH 2/2] Implement atomic file operations for URL fetching in
 runtime_import.cjs

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>
---
 actions/setup/js/runtime_import.cjs | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/actions/setup/js/runtime_import.cjs b/actions/setup/js/runtime_import.cjs
index ec31047b8c8..f4b4f69fff0 100644
--- a/actions/setup/js/runtime_import.cjs
+++ b/actions/setup/js/runtime_import.cjs
@@ -466,9 +466,30 @@ async function fetchUrlContent(url, cacheDir) {
         });
 
         res.on("end", () => {
-          // Cache the content
-          fs.writeFileSync(cacheFile, data, "utf8");
-          resolve(data);
+          // Use atomic write-then-rename pattern to prevent partial writes
+          // Generate unique temporary filename with process ID and timestamp
+          const tempFile = `${cacheFile}.tmp.${process.pid}.${Date.now()}`;
+
+          try {
+            // Write to temporary file first
+            fs.writeFileSync(tempFile, data, "utf8");
+
+            // Atomic rename (POSIX guarantee) - ensures file is either completely written or not present
+            fs.renameSync(tempFile, cacheFile);
+
+            resolve(data);
+          } catch (error) {
+            // Clean up temporary file on error
+            try {
+              if (fs.existsSync(tempFile)) {
+                fs.unlinkSync(tempFile);
+              }
+            } catch (cleanupError) {
+              // Ignore cleanup errors
+            }
+            const errorMessage = error instanceof Error ? error.message : String(error);
+            reject(new Error(`Failed to cache URL content: ${errorMessage}`));
+          }
         });
       })
       .on("error", err => {