diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
index e93fd88f..6a4a7660 100644
--- a/.devcontainer/devcontainer.json
+++ b/.devcontainer/devcontainer.json
@@ -28,7 +28,7 @@
         "-AmazonWebServices.aws-toolkit-vscode", // the AWS CLI feature installs this automatically, but it's causing problems in VS Code
         // basic tooling
         // "eamodio.gitlens@15.5.1",
-        "coderabbit.coderabbit-vscode@0.21.9",
+        "coderabbit.coderabbit-vscode@0.23.0",
         "ms-vscode.live-server@0.5.2025051301",
         "MS-vsliveshare.vsliveshare@1.0.5905",
         "anthropic.claude-code@2.1.283",
@@ -71,5 +71,5 @@
   "initializeCommand": "sh .devcontainer/initialize-command.sh",
   "onCreateCommand": "sh .devcontainer/on-create-command.sh",
   "postStartCommand": "sh .devcontainer/post-start-command.sh"
-  // Devcontainer context hash (do not manually edit this, it's managed by a pre-commit hook): 85e48e15 # spellchecker:disable-line
+  // Devcontainer context hash (do not manually edit this, it's managed by a pre-commit hook): 88f0aac3 # spellchecker:disable-line
 }
diff --git a/.devcontainer/on-create-command-boilerplate.sh b/.devcontainer/on-create-command-boilerplate.sh
index 31e70884..3e70922b 100644
--- a/.devcontainer/on-create-command-boilerplate.sh
+++ b/.devcontainer/on-create-command-boilerplate.sh
@@ -7,3 +7,25 @@ git config --global --add --bool push.autoSetupRemote true
 git config --local core.symlinks true
 
 sh .devcontainer/create-aws-profile.sh
+
+# The Biome VS Code extension starts a session per workspace folder and warns when folders nest. The root folder's
+# session already covers the nested ones, so Biome is switched off in their (gitignored) folder settings.
+root_folder_path="."
+for workspace_file in *.code-workspace; do
+    if [ ! -f "$workspace_file" ]; then
+        continue
+    fi
+    folders=$(sed -n 's/^[[:space:]]*"path":[[:space:]]*"\([^"]*\)".*/\1/p' "$workspace_file")
+    if ! echo "$folders" | grep -qxF "$root_folder_path"; then
+        continue
+    fi
+    printf '%s\n' "$folders" | while IFS= read -r folder; do
+        case "$folder" in
+        .. | ../* | /*) continue ;;
+        esac
+        if [ "$folder" != "$root_folder_path" ] && [ -d "$folder" ] && [ ! -e "$folder/.vscode/settings.json" ]; then
+            mkdir -p "$folder/.vscode"
+            echo '{ "biome.enabled": false }' >"$folder/.vscode/settings.json"
+        fi
+    done
+done
diff --git a/template/.devcontainer/devcontainer.json.jinja-base b/template/.devcontainer/devcontainer.json.jinja-base
index b92ef7b1..f2e64b45 100644
--- a/template/.devcontainer/devcontainer.json.jinja-base
+++ b/template/.devcontainer/devcontainer.json.jinja-base
@@ -34,7 +34,7 @@
         "-AmazonWebServices.aws-toolkit-vscode", // the AWS CLI feature installs this automatically, but it's causing problems in VS Code{% endraw %}{% endif %}{% raw %}
         // basic tooling
         // "eamodio.gitlens@15.5.1",
-        "coderabbit.coderabbit-vscode@0.21.9",
+        "coderabbit.coderabbit-vscode@0.23.0",
         "ms-vscode.live-server@0.5.2025051301",
         "MS-vsliveshare.vsliveshare@1.0.5905",{% endraw %}{% if install_claude_cli %}{% raw %}
         "anthropic.claude-code@2.1.283",{% endraw %}{% endif %}{% raw %}{% endraw %}{% if (is_child_of_copier_base_template is defined and is_child_of_copier_base_template is sameas(true)) or (is_child_of_copier_base_template is not defined and template_uses_python is defined and template_uses_python is sameas(true)) %}{% raw %}