diff --git a/seaweed-volume/src/remote_storage/s3_tier.rs b/seaweed-volume/src/remote_storage/s3_tier.rs
index be88adcf8..9d3281634 100644
--- a/seaweed-volume/src/remote_storage/s3_tier.rs
+++ b/seaweed-volume/src/remote_storage/s3_tier.rs
@@ -486,6 +486,11 @@ impl S3TierRegistry {
         self.backends.keys().cloned().collect()
     }
 
+    /// Remove a backend by name.
+    pub fn remove(&mut self, name: &str) {
+        self.backends.remove(name);
+    }
+
     pub fn clear(&mut self) {
         self.backends.clear();
     }
diff --git a/seaweed-volume/src/server/grpc_server.rs b/seaweed-volume/src/server/grpc_server.rs
index e0d204fad..ecdee7894 100644
--- a/seaweed-volume/src/server/grpc_server.rs
+++ b/seaweed-volume/src/server/grpc_server.rs
@@ -4311,7 +4311,9 @@ mod tests {
         std::fs::remove_file(&dat_path).unwrap();
 
         let (endpoint, shutdown_tx) = spawn_fake_s3_server(dat_bytes.clone());
-        global_s3_tier_registry().write().unwrap().clear();
+        // Use a test-specific backend_id to avoid racing with other tests
+        // that share the global registry.  Never call clear() — only
+        // register/remove our own entries.
         let tier_config = S3TierConfig {
             access_key: "access".to_string(),
             secret_key: "secret".to_string(),
@@ -4323,14 +4325,16 @@ mod tests {
         };
         {
             let mut registry = global_s3_tier_registry().write().unwrap();
-            registry.register("s3.default".to_string(), S3TierBackend::new(&tier_config));
-            registry.register("s3".to_string(), S3TierBackend::new(&tier_config));
+            registry.register(
+                "s3.incr_copy_test".to_string(),
+                S3TierBackend::new(&tier_config),
+            );
         }
 
         let vif = crate::storage::volume::VifVolumeInfo {
             files: vec![crate::storage::volume::VifRemoteFile {
                 backend_type: "s3".to_string(),
-                backend_id: "default".to_string(),
+                backend_id: "incr_copy_test".to_string(),
                 key: "remote-key".to_string(),
                 offset: 0,
                 file_size: dat_bytes.len() as u64,
@@ -4539,7 +4543,10 @@ mod tests {
         assert_eq!(copied, dat_bytes[super_block_size as usize..]);
 
         let _ = shutdown_tx.send(());
-        global_s3_tier_registry().write().unwrap().clear();
+        global_s3_tier_registry()
+            .write()
+            .unwrap()
+            .remove("s3.incr_copy_test");
     }
 
     #[tokio::test]
diff --git a/seaweed-volume/src/server/heartbeat.rs b/seaweed-volume/src/server/heartbeat.rs
index 6fcfd523c..434e841cf 100644
--- a/seaweed-volume/src/server/heartbeat.rs
+++ b/seaweed-volume/src/server/heartbeat.rs
@@ -1408,10 +1408,8 @@ mod tests {
     #[test]
     fn test_apply_storage_backends_registers_s3_default_aliases() {
         let state = test_state_with_store(Store::new(NeedleMapKind::InMemory));
-        crate::remote_storage::s3_tier::global_s3_tier_registry()
-            .write()
-            .unwrap()
-            .clear();
+        // Do not call clear() on the global registry — other tests may be
+        // running concurrently.  Just register our entries and verify them.
 
         apply_storage_backends(
             &state,
@@ -1443,10 +1441,8 @@ mod tests {
     #[test]
     fn test_apply_storage_backends_ignores_unsupported_types() {
         let state = test_state_with_store(Store::new(NeedleMapKind::InMemory));
-        crate::remote_storage::s3_tier::global_s3_tier_registry()
-            .write()
-            .unwrap()
-            .clear();
+        // Do not call clear() on the global registry — other tests may be
+        // running concurrently.
 
         apply_storage_backends(
             &state,
@@ -1457,12 +1453,17 @@ mod tests {
             }],
         );
 
+        // The per-state registry is freshly created and should have no entries
+        // since "rclone" is unsupported.
         let registry = state.s3_tier_registry.read().unwrap();
         assert!(registry.names().is_empty());
+        // Only check that the unsupported type was not added to the global
+        // registry.  Other tests may have their own entries present.
         let global_registry = crate::remote_storage::s3_tier::global_s3_tier_registry()
             .read()
             .unwrap();
-        assert!(global_registry.names().is_empty());
+        assert!(global_registry.get("rclone.default").is_none());
+        assert!(global_registry.get("rclone").is_none());
     }
 
     #[test]
diff --git a/seaweed-volume/src/storage/volume.rs b/seaweed-volume/src/storage/volume.rs
index 5e4688115..2ee94b5b2 100644
--- a/seaweed-volume/src/storage/volume.rs
+++ b/seaweed-volume/src/storage/volume.rs
@@ -3917,6 +3917,11 @@ mod tests {
             .unwrap();
         assert!(deleted_size.0 > 0);
         assert_eq!(v.dat_file_size().unwrap(), dat_size_before_reload);
+
+        crate::remote_storage::s3_tier::global_s3_tier_registry()
+            .write()
+            .unwrap()
+            .remove("s3.vif_rw_test");
     }
 
     #[test]
@@ -4079,10 +4084,9 @@ mod tests {
         std::fs::remove_file(&dat_path).unwrap();
 
         let (endpoint, shutdown_tx) = spawn_fake_s3_server(dat_bytes.clone());
-        crate::remote_storage::s3_tier::global_s3_tier_registry()
-            .write()
-            .unwrap()
-            .clear();
+        // Use a test-specific backend_id to avoid racing with other tests
+        // that share the global registry.  Never call clear() — only
+        // register/remove our own entries.
         let tier_config = crate::remote_storage::s3_tier::S3TierConfig {
             access_key: "access".to_string(),
             secret_key: "secret".to_string(),
@@ -4097,11 +4101,7 @@ mod tests {
                 .write()
                 .unwrap();
             registry.register(
-                "s3.default".to_string(),
-                crate::remote_storage::s3_tier::S3TierBackend::new(&tier_config),
-            );
-            registry.register(
-                "s3".to_string(),
+                "s3.remote_only_rw".to_string(),
                 crate::remote_storage::s3_tier::S3TierBackend::new(&tier_config),
             );
         }
@@ -4109,7 +4109,7 @@ mod tests {
         let vif = VifVolumeInfo {
             files: vec![VifRemoteFile {
                 backend_type: "s3".to_string(),
-                backend_id: "default".to_string(),
+                backend_id: "remote_only_rw".to_string(),
                 key: "remote-key".to_string(),
                 offset: 0,
                 file_size: dat_bytes.len() as u64,
@@ -4166,6 +4166,10 @@ mod tests {
         assert_eq!(meta.data_size, 11);
 
         let _ = shutdown_tx.send(());
+        crate::remote_storage::s3_tier::global_s3_tier_registry()
+            .write()
+            .unwrap()
+            .remove("s3.remote_only_rw");
     }
 
     /// Volume destroy removes .vif alongside the primary data files.