diff --git a/CHANGELOG.md b/CHANGELOG.md
index dc19eba..01b2c2b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,10 @@ Format based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## [Unreleased]
 
+### Added
+
+- **Peer dependency**: `@behindthemusictree/brand` (`^12.0.0`) is now declared as an optional peer dependency, making the existing reliance on its CSS variables explicit. The README lists the variables read.
+
 ## [0.1.0] - 2026-08-14
 
 ### Added
diff --git a/README.md b/README.md
index 85df6c8..a193d2b 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,9 @@ on this package rather than the other way around.
 Components are styled with Tailwind utility classes referencing CSS custom properties
 (`--color-*`, `--space-*`, `--radius-*`). **Consumers must also load
 `@behindthemusictree/brand`'s `tokens/theme.css`** — this package does not ship or import it.
+`brand` is an optional peer dependency (`^12.0.0`): the app installs and owns its version. Outside
+BTMT, define the variables yourself instead; the ones currently read are `--color-primary`,
+`--color-neutral-{100,200,300,700}`, `--color-red-{600,700}` and `--color-green-600`.
 
 ## Development
 
diff --git a/packages/ui/package.json b/packages/ui/package.json
index 56fa166..59c9353 100644
--- a/packages/ui/package.json
+++ b/packages/ui/package.json
@@ -31,7 +31,13 @@
   },
   "peerDependencies": {
     "react": ">=18.0.0",
-    "react-dom": ">=18.0.0"
+    "react-dom": ">=18.0.0",
+    "@behindthemusictree/brand": "^12.0.0"
+  },
+  "peerDependenciesMeta": {
+    "@behindthemusictree/brand": {
+      "optional": true
+    }
   },
   "dependencies": {
     "class-variance-authority": "^0.7.1",
@@ -41,6 +47,7 @@
     "tailwind-merge": "^3.2.0"
   },
   "devDependencies": {
+    "@behindthemusictree/brand": "^12.0.0",
     "@types/react": "^18.2.0",
     "@types/react-dom": "^18.2.0",
     "react": "^18.2.0",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index a1ad81c..4163c9d 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -70,6 +70,9 @@ importers:
         specifier: ^3.2.0
         version: 3.6.0
     devDependencies:
+      '@behindthemusictree/brand':
+        specifier: ^12.0.0
+        version: 12.0.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
       '@types/react':
         specifier: ^18.2.0
         version: 18.3.31
@@ -178,6 +181,12 @@ packages:
     resolution: {integrity: sha512-Vj1jF3cPfxg7OAfoI7QnVKLoILlm2JF9pnVHrX8qx7AHMiYWT+NDAA7jChlNgRS4WTLc/fD1lXLmPixluj+3Gg==}
     engines: {node: '>=6.9.0'}
 
+  '@behindthemusictree/brand@12.0.0':
+    resolution: {integrity: sha512-9PrERlo0lHyB3dtSQJYg4XvrM1Pm8sZ6MO0zV/lO/8UBLMNtm3QDTnuWwNW5z8dQhPD3h0Hx8N0W373C69CzDQ==, tarball: https://npm.pkg.github.com/download/@behindthemusictree/brand/12.0.0/aeba06e0b62328472fafecd16f9c1938af05e00f}
+    peerDependencies:
+      react: '>=18.0.0'
+      react-dom: '>=18.0.0'
+
   '@esbuild/aix-ppc64@0.21.5':
     resolution: {integrity: sha512-1SDgH6ZSPTlggy1yI6+Dbkiz8xzpHJEVAlF/AM1tHPLsf5STom9rwtjE4hKAF20FfXXNTFqEYXyJNWh1GiZedQ==}
     engines: {node: '>=12'}
@@ -1370,6 +1379,11 @@ snapshots:
       '@babel/helper-string-parser': 7.29.7
       '@babel/helper-validator-identifier': 7.29.7
 
+  '@behindthemusictree/brand@12.0.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)':
+    dependencies:
+      react: 18.3.1
+      react-dom: 18.3.1(react@18.3.1)
+
   '@esbuild/aix-ppc64@0.21.5':
     optional: true