diff --git a/config/h1n1pdm/auspice_config.json b/config/h1n1pdm/auspice_config.json
index 2c049bef..1b4f1759 100644
--- a/config/h1n1pdm/auspice_config.json
+++ b/config/h1n1pdm/auspice_config.json
@@ -158,5 +158,16 @@
   "metadata_columns": [
     "accession_ha",
     "accession_na"
-  ]
-}
+  ],
+  "extensions": {
+    "nextclade": {
+      "clade_node_attrs": [
+        {
+          "name": "subclade",
+          "displayName": "Subclade",
+          "description": "Experimental fine-grained subclade annotation."
+        }
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/config/h1n1pdm/ha/auspice_config.json b/config/h1n1pdm/ha/auspice_config.json
index fbf545b9..dd58f4d9 100644
--- a/config/h1n1pdm/ha/auspice_config.json
+++ b/config/h1n1pdm/ha/auspice_config.json
@@ -263,5 +263,16 @@
     "gisaid_strain",
     "accession_ha",
     "accession_na"
-  ]
-}
+  ],
+  "extensions": {
+    "nextclade": {
+      "clade_node_attrs": [
+        {
+          "name": "subclade",
+          "displayName": "Subclade",
+          "description": "Experimental fine-grained subclade annotation."
+        }
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/config/h1n1pdm/na/auspice_config.json b/config/h1n1pdm/na/auspice_config.json
index 8eb3865c..90db2a03 100644
--- a/config/h1n1pdm/na/auspice_config.json
+++ b/config/h1n1pdm/na/auspice_config.json
@@ -196,5 +196,16 @@
     "gisaid_strain",
     "accession_ha",
     "accession_na"
-  ]
-}
+  ],
+  "extensions": {
+    "nextclade": {
+      "clade_node_attrs": [
+        {
+          "name": "subclade",
+          "displayName": "Subclade",
+          "description": "Experimental fine-grained subclade annotation."
+        }
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/config/h3n2/auspice_config.json b/config/h3n2/auspice_config.json
index 0f4016f1..83e9e40e 100644
--- a/config/h3n2/auspice_config.json
+++ b/config/h3n2/auspice_config.json
@@ -168,5 +168,16 @@
   "metadata_columns": [
     "accession_ha",
     "accession_na"
-  ]
-}
+  ],
+  "extensions": {
+    "nextclade": {
+      "clade_node_attrs": [
+        {
+          "name": "subclade",
+          "displayName": "Subclade",
+          "description": "Experimental fine-grained subclade annotation."
+        }
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/config/h3n2/ha/auspice_config.json b/config/h3n2/ha/auspice_config.json
index bc473236..93f6d0d5 100644
--- a/config/h3n2/ha/auspice_config.json
+++ b/config/h3n2/ha/auspice_config.json
@@ -253,5 +253,16 @@
     "gisaid_strain",
     "accession_ha",
     "accession_na"
-  ]
-}
+  ],
+  "extensions": {
+    "nextclade": {
+      "clade_node_attrs": [
+        {
+          "name": "subclade",
+          "displayName": "Subclade",
+          "description": "Experimental fine-grained subclade annotation."
+        }
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/config/h3n2/na/auspice_config.json b/config/h3n2/na/auspice_config.json
index 19d164ac..44eb3b1e 100644
--- a/config/h3n2/na/auspice_config.json
+++ b/config/h3n2/na/auspice_config.json
@@ -209,5 +209,16 @@
     "gisaid_strain",
     "accession_ha",
     "accession_na"
-  ]
-}
+  ],
+  "extensions": {
+    "nextclade": {
+      "clade_node_attrs": [
+        {
+          "name": "subclade",
+          "displayName": "Subclade",
+          "description": "Experimental fine-grained subclade annotation."
+        }
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/config/vic/auspice_config.json b/config/vic/auspice_config.json
index f86f95f4..4e01915e 100644
--- a/config/vic/auspice_config.json
+++ b/config/vic/auspice_config.json
@@ -143,5 +143,16 @@
   "metadata_columns": [
     "accession_ha",
     "accession_na"
-  ]
-}
+  ],
+  "extensions": {
+    "nextclade": {
+      "clade_node_attrs": [
+        {
+          "name": "subclade",
+          "displayName": "Subclade",
+          "description": "Experimental fine-grained subclade annotation."
+        }
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/config/vic/ha/auspice_config.json b/config/vic/ha/auspice_config.json
index ff882a89..e49e85c4 100644
--- a/config/vic/ha/auspice_config.json
+++ b/config/vic/ha/auspice_config.json
@@ -228,5 +228,16 @@
     "gisaid_strain",
     "accession_ha",
     "accession_na"
-  ]
-}
+  ],
+  "extensions": {
+    "nextclade": {
+      "clade_node_attrs": [
+        {
+          "name": "subclade",
+          "displayName": "Subclade",
+          "description": "Experimental fine-grained subclade annotation."
+        }
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/config/vic/na/auspice_config.json b/config/vic/na/auspice_config.json
index d31f2844..02636518 100644
--- a/config/vic/na/auspice_config.json
+++ b/config/vic/na/auspice_config.json
@@ -221,5 +221,16 @@
     "gisaid_strain",
     "accession_ha",
     "accession_na"
-  ]
-}
+  ],
+  "extensions": {
+    "nextclade": {
+      "clade_node_attrs": [
+        {
+          "name": "subclade",
+          "displayName": "Subclade",
+          "description": "Experimental fine-grained subclade annotation."
+        }
+      ]
+    }
+  }
+}
\ No newline at end of file
diff --git a/profiles/ci/builds.yaml b/profiles/ci/builds.yaml
index d9abe4fa..0f577c56 100644
--- a/profiles/ci/builds.yaml
+++ b/profiles/ci/builds.yaml
@@ -50,6 +50,7 @@ builds:
       annotation: "config/h3n2/{segment}/genemap.gff"
       tree_exclude_sites: "config/h3n2/{segment}/exclude-sites.txt"
       clades: "config/h3n2/ha/clades.tsv"
+      subclades: "config/h3n2/{segment}/subclades.tsv"
       min_date: "12Y"
       auspice_config: "config/h3n2/auspice_config.json"
       enable_titer_models: true