From 54807dc4ac76118468ae592711b83069f422b94e Mon Sep 17 00:00:00 2001
From: edalzell <erin@silentz.co>
Date: Wed, 28 Oct 2026 11:48:14 -0700
Subject: [PATCH 1/2] Add test for index usage lost between parallel warm
 processes

---
 tests/Stache/StoreTest.php | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/tests/Stache/StoreTest.php b/tests/Stache/StoreTest.php
index 9e22f0494ba..503b5b08c05 100644
--- a/tests/Stache/StoreTest.php
+++ b/tests/Stache/StoreTest.php
@@ -107,6 +107,24 @@ public function it_gets_the_paths_from_the_cache_again_after_memoized_state_is_r
         $this->assertEquals($expected, $store->paths());
         $this->assertEquals(2, $cacheHits);
     }
+
+    #[Test]
+    public function index_usage_cached_by_another_process_is_kept()
+    {
+        // Two instances of the same store stand in for two processes warming
+        // the Stache in parallel. Each memoizes its own usage list, so the
+        // second write must merge with the cache instead of replacing it.
+        $cacheKey = "stache::indexes::{$this->store->key()}::_indexes";
+        $other = new TestStore;
+
+        $this->store->cacheIndexUsage('path');
+        $other->cacheIndexUsage('path');
+
+        $this->store->cacheIndexUsage('site');
+        $other->cacheIndexUsage('uri');
+
+        $this->assertEquals(['path', 'site', 'uri'], Cache::get($cacheKey));
+    }
 }
 
 class TestStore extends Store

From 023ef7ef2c7b32a29422c18a86196440ef1dc137 Mon Sep 17 00:00:00 2001
From: edalzell <erin@silentz.co>
Date: Wed, 28 Oct 2026 11:54:07 -0700
Subject: [PATCH 2/2] Merge cached index usage instead of overwriting it

---
 src/Stache/Stores/Store.php | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/Stache/Stores/Store.php b/src/Stache/Stores/Store.php
index b9b067a76a6..8216807079a 100644
--- a/src/Stache/Stores/Store.php
+++ b/src/Stache/Stores/Store.php
@@ -121,9 +121,13 @@ public function cacheIndexUsage($index)
 
         $indexes->push($index);
 
-        $this->usedIndexes = $indexes;
+        // Another process may have recorded usages since this one memoized its
+        // list (e.g. parallel warming), so merge with the cache rather than replace it.
+        $cached = collect(Stache::cacheStore()->get($key = $this->indexUsageCacheKey(), []));
 
-        Stache::cacheStore()->put($this->indexUsageCacheKey(), $indexes->all());
+        $this->usedIndexes = $cached->merge($indexes)->unique()->sort()->values();
+
+        Stache::cacheStore()->put($key, $this->usedIndexes->all());
     }
 
     protected function indexUsageCacheKey()