diff --git a/.changeset/shiny-planes-shop.md b/.changeset/shiny-planes-shop.md
new file mode 100644
index 0000000..7659f2e
--- /dev/null
+++ b/.changeset/shiny-planes-shop.md
@@ -0,0 +1,5 @@
+---
+"@plexus-ms/config": minor
+---
+
+Initial release: shared tool configurations as subpath exports, starting with Biome — `"extends": ["@plexus-ms/config/biome"]`.
diff --git a/biome.json b/biome.json
index 57b2238..66e5934 100644
--- a/biome.json
+++ b/biome.json
@@ -1,30 +1,4 @@
 {
   "$schema": "https://biomejs.dev/schemas/2.5.1/schema.json",
-  "vcs": {
-    "enabled": true,
-    "clientKind": "git",
-    "useIgnoreFile": true
-  },
-  "formatter": {
-    "indentStyle": "space",
-    "indentWidth": 2,
-    "lineEnding": "lf",
-    "lineWidth": 120
-  },
-  "javascript": {
-    "formatter": {
-      "quoteStyle": "single"
-    }
-  },
-  "css": {
-    "parser": {
-      "tailwindDirectives": true
-    }
-  },
-  "assist": {
-    "enabled": true,
-    "actions": {
-      "recommended": true
-    }
-  }
+  "extends": ["@plexus-ms/config/biome"]
 }
diff --git a/package.json b/package.json
index 8e2368a..2353a97 100644
--- a/package.json
+++ b/package.json
@@ -1,4 +1,7 @@
 {
   "name": "packages",
-  "private": true
+  "private": true,
+  "devDependencies": {
+    "@plexus-ms/config": "workspace:*"
+  }
 }
diff --git a/packages/config/biome.json b/packages/config/biome.json
new file mode 100644
index 0000000..2b10d31
--- /dev/null
+++ b/packages/config/biome.json
@@ -0,0 +1,31 @@
+{
+  "$schema": "https://biomejs.dev/schemas/2.5.1/schema.json",
+  "root": false,
+  "vcs": {
+    "enabled": true,
+    "clientKind": "git",
+    "useIgnoreFile": true
+  },
+  "formatter": {
+    "indentStyle": "space",
+    "indentWidth": 2,
+    "lineEnding": "lf",
+    "lineWidth": 120
+  },
+  "javascript": {
+    "formatter": {
+      "quoteStyle": "single"
+    }
+  },
+  "css": {
+    "parser": {
+      "tailwindDirectives": true
+    }
+  },
+  "assist": {
+    "enabled": true,
+    "actions": {
+      "recommended": true
+    }
+  }
+}
diff --git a/packages/config/package.json b/packages/config/package.json
new file mode 100644
index 0000000..5f9dd41
--- /dev/null
+++ b/packages/config/package.json
@@ -0,0 +1,21 @@
+{
+  "name": "@plexus-ms/config",
+  "version": "0.0.0",
+  "description": "Shared tool configurations for Plexus repos — each an extend-in-one-line subpath export (§ 9 PLX).",
+  "license": "GPL-3.0-or-later",
+  "files": [
+    "biome.json"
+  ],
+  "exports": {
+    "./biome": "./biome.json"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/plexus-ms/packages.git",
+    "directory": "packages/config"
+  },
+  "publishConfig": {
+    "registry": "https://registry.npmjs.org",
+    "access": "public"
+  }
+}
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 308671a..2ff26ca 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -12,7 +12,13 @@ catalogs:
 
 importers:
 
-  .: {}
+  .:
+    devDependencies:
+      '@plexus-ms/config':
+        specifier: workspace:*
+        version: link:packages/config
+
+  packages/config: {}
 
   packages/std:
     dependencies: