3 files changed, 23 insertions, 0 deletions
diff --git a/internal/cache/cache.go b/internal/cache/cache.go
index 2cc07de96..5bfa70ffa 100644
--- a/internal/cache/cache.go
+++ b/internal/cache/cache.go
@@ -96,6 +96,7 @@ func (c *Caches) Init() {
 	c.initFollowRequest()
 	c.initFollowRequestIDs()
 	c.initFollowingTagIDs()
+	c.initHomeAccountIDs()
 	c.initHomeTimelines()
 	c.initInReplyToIDs()
 	c.initInstance()
diff --git a/internal/cache/db.go b/internal/cache/db.go
index 8a8f59539..d5f25516b 100644
--- a/internal/cache/db.go
+++ b/internal/cache/db.go
@@ -145,6 +145,10 @@ type DBCaches struct {
 	//
 	FollowingTagIDs SliceCache[string]
 
+	// HomeAccountIDs provides access to the account IDs present in an account's
+	// home timeline, bearing in mind that some may be part of exclusive lists.
+	HomeAccountIDs SliceCache[string]
+
 	// Instance provides access to the gtsmodel Instance database cache.
 	Instance StructCache[*gtsmodel.Instance]
 
@@ -883,6 +887,17 @@ func (c *Caches) initFollowingTagIDs() {
 	c.DB.FollowingTagIDs.Init(0, cap)
 }
 
+func (c *Caches) initHomeAccountIDs() {
+	// Calculate maximum cache size.
+	cap := calculateSliceCacheMax(
+		config.GetCacheHomeAccountIDsMemRatio(),
+	)
+
+	log.Infof(nil, "cache size = %d", cap)
+
+	c.DB.HomeAccountIDs.Init(0, cap)
+}
+
 func (c *Caches) initInReplyToIDs() {
 	// Calculate maximum cache size.
 	cap := calculateSliceCacheMax(
diff --git a/internal/cache/invalidate.go b/internal/cache/invalidate.go
index c6c25d4eb..58c427050 100644
--- a/internal/cache/invalidate.go
+++ b/internal/cache/invalidate.go
@@ -155,6 +155,9 @@ func (c *Caches) OnInvalidateFollow(follow *gtsmodel.Follow) {
 	// results for them as mute / visibility result requester.
 	if follow.Account == nil || follow.Account.IsLocal() {
 		localAccountIDs = append(localAccountIDs, follow.AccountID)
+
+		// Also invalidate their home account IDs cache.
+		c.DB.HomeAccountIDs.Invalidate(follow.AccountID)
 	}
 
 	// If target is local (or uncertain), also invalidate
@@ -261,6 +264,10 @@ func (c *Caches) OnInvalidateList(list *gtsmodel.List) {
 		// follow IDs in list.
 		"f"+list.ID,
 	)
+
+	// Invalidate user's home account IDs cache,
+	// as list exclusivity flag may have changed.
+	c.DB.HomeAccountIDs.Invalidate(list.AccountID)
 }
 
 func (c *Caches) OnInvalidateMedia(media *gtsmodel.MediaAttachment) {