From 9942dbfc3bae0fb2e699bc58359cb0753e0c51e1 Mon Sep 17 00:00:00 2001
From: "homeboy-ci[bot]" <266378653+homeboy-ci[bot]@users.noreply.github.com>
Date: Tue, 25 Aug 2026 14:42:18 +0000
Subject: [PATCH] fix: serialize readonly mount cache retention

---
 .../runtime-playground/src/mount-materialization.ts    |  2 +-
 tests/playground-readonly-mounts.test.ts               | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/packages/runtime-playground/src/mount-materialization.ts b/packages/runtime-playground/src/mount-materialization.ts
index 154626ad..4fbc253b 100644
--- a/packages/runtime-playground/src/mount-materialization.ts
+++ b/packages/runtime-playground/src/mount-materialization.ts
@@ -128,7 +128,7 @@ async function prepareReadonlyDirectory(mount: MountSpec, mountIndex: number, so
   await mkdir(cacheRoot, { recursive: true, mode: 0o700 })
 
   let mode: ReadonlyMountPreparation["mode"] = "cache-hit"
-  await withPlaygroundArchiveCacheLock(cacheRoot, `readonly-mount-${generation.fingerprint}`, async () => {
+  await withPlaygroundArchiveCacheLock(cacheRoot, "readonly-mount-cache", async () => {
     for (let attempt = 0; attempt < 2; attempt++) {
       if (!await directoryExists(cachePath)) {
         mode = "cache-miss"
diff --git a/tests/playground-readonly-mounts.test.ts b/tests/playground-readonly-mounts.test.ts
index 0c75d338..24e9083b 100644
--- a/tests/playground-readonly-mounts.test.ts
+++ b/tests/playground-readonly-mounts.test.ts
@@ -171,6 +171,16 @@ try {
   assert.ok((await Promise.all(concurrent.map(async (entry) => await readFile(join(entry.mounts[0].source, "value.txt"), "utf8") === "concurrent"))).every(Boolean), "concurrent snapshots are complete")
   await Promise.all(concurrent.map((entry) => entry[Symbol.asyncDispose]()))
 
+  const parallelSources = await Promise.all(Array.from({ length: 12 }, async (_, index) => {
+    const source = join(root, `parallel-source-${index}`)
+    await mkdir(source)
+    await writeFile(join(source, "value.txt"), `parallel-${index}`)
+    return source
+  }))
+  const parallel = await stageReadonlyPlaygroundMounts(parallelSources.map((source, index) => ({ source, target: `/parallel-${index}`, mode: "readonly" })))
+  assert.ok((await Promise.all(parallel.mounts.map(async (mount, index) => await readFile(join(mount.source, "value.txt"), "utf8") === `parallel-${index}`))).every(Boolean), "parallel unique snapshots survive cache retention")
+  await parallel[Symbol.asyncDispose]()
+
   const nestedParent = join(root, "nested-parent")
   const nestedOverlay = join(root, "nested-overlay")
   await mkdir(nestedParent)