diff --git a/packages/lang-core/package.json b/packages/lang-core/package.json
index ee2c87ed0..3e96ed168 100644
--- a/packages/lang-core/package.json
+++ b/packages/lang-core/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@openuidev/lang-core",
-  "version": "0.2.5",
+  "version": "0.2.6",
   "description": "Framework-agnostic core for OpenUI Lang: parser, prompt generation, validation, and type definitions",
   "license": "MIT",
   "type": "module",
diff --git a/packages/openui-cli/package.json b/packages/openui-cli/package.json
index 82cd60bbb..eb35fd1a3 100644
--- a/packages/openui-cli/package.json
+++ b/packages/openui-cli/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@openuidev/cli",
-  "version": "0.0.7",
+  "version": "0.0.8",
   "description": "CLI for OpenUI — scaffold generative UI chat apps and generate LLM system prompts from component libraries",
   "bin": {
     "openui": "dist/index.js"
diff --git a/packages/react-ui/check-css-artifacts.js b/packages/react-ui/check-css-artifacts.js
index 1f972fb88..dfa0001db 100644
--- a/packages/react-ui/check-css-artifacts.js
+++ b/packages/react-ui/check-css-artifacts.js
@@ -55,6 +55,14 @@ for (const name of unlayered) {
   assert(!/^\s*@layer/.test(read(path.join("styles", name))), `styles/${name} must stay unlayered`);
 }
 
+// Unlayered default exports must also be BOM-free. A leading BOM is harmless in
+// an unlayered file (the decoder drops it at byte 0), but cp-css.js strips it,
+// and a regression re-arms the 2026-06 incident the moment these files are ever
+// wrapped. Covers ./components.css and every ./styles/* (incl. openui-defaults).
+for (const rel of ["components/index.css", ...unlayered.map((n) => path.join("styles", n))]) {
+  assert(!read(rel).includes(""), `${rel} contains a BOM (unlayered export must be BOM-free)`);
+}
+
 for (const f of [
   ...layered.map((n) => path.join("layered", "styles", n)),
   "layered/components/index.css",
diff --git a/packages/react-ui/cp-css.js b/packages/react-ui/cp-css.js
index 2c645f860..321559c75 100644
--- a/packages/react-ui/cp-css.js
+++ b/packages/react-ui/cp-css.js
@@ -2,7 +2,7 @@ import fs from "fs";
 import { camelCase } from "lodash-es";
 import path from "path";
 import { fileURLToPath } from "url";
-import { mirrorStylesWithLayer, writeLayeredCopy } from "./css-layer-utils.mjs";
+import { mirrorStylesWithLayer, stripBom, writeLayeredCopy } from "./css-layer-utils.mjs";
 
 const dirname = path.dirname(fileURLToPath(import.meta.url));
 
@@ -33,6 +33,23 @@ function fixScssImportsInJs(dir) {
   });
 }
 
+// Strip Sass's leading UTF-8 BOM (compressed-mode output for non-ASCII) from
+// every *.css under dir, in place — so the unlayered default exports
+// (./components.css, ./styles/*) ship BOM-free. The layered mirror strips it
+// separately via wrapInLayer.
+function stripBomFromCssInDir(dir) {
+  for (const entry of fs.readdirSync(dir)) {
+    const full = path.join(dir, entry);
+    if (fs.statSync(full).isDirectory()) {
+      stripBomFromCssInDir(full);
+    } else if (entry.endsWith(".css")) {
+      const content = fs.readFileSync(full, "utf8");
+      const stripped = stripBom(content);
+      if (stripped !== content) fs.writeFileSync(full, stripped, "utf8");
+    }
+  }
+}
+
 // Copy CSS files from src to dist
 function copyCssFiles() {
   const srcDir = path.join(dirname, "dist", "components");
@@ -41,6 +58,16 @@ function copyCssFiles() {
   // Ensure the dist/styles directory exists
   ensureDirectoryExists(distDir);
 
+  // Strip Sass's leading BOM from the unlayered sass output before copying, so
+  // the default exports (./components.css, ./styles/*) ship BOM-free.
+  stripBomFromCssInDir(srcDir);
+  const defaultsCssSrc = path.join(dirname, "dist", "openui-defaults.css");
+  if (fs.existsSync(defaultsCssSrc)) {
+    const content = fs.readFileSync(defaultsCssSrc, "utf8");
+    const stripped = stripBom(content);
+    if (stripped !== content) fs.writeFileSync(defaultsCssSrc, stripped, "utf8");
+  }
+
   // Read all component directories
   const components = fs.readdirSync(srcDir);
 
diff --git a/packages/react-ui/css-layer-utils.mjs b/packages/react-ui/css-layer-utils.mjs
index a4799c68d..fa4acd912 100644
--- a/packages/react-ui/css-layer-utils.mjs
+++ b/packages/react-ui/css-layer-utils.mjs
@@ -1,14 +1,21 @@
 import fs from "fs";
 import path from "path";
 
+// Strip a leading UTF-8 BOM (U+FEFF). Sass emits one in compressed mode for
+// files with non-ASCII output. A browser drops it at byte 0, but it is noise in
+// shipped artifacts and becomes fatal if the content is ever wrapped \u2014 the BOM
+// would land mid-stylesheet inside a layer block, where U+FEFF parses as an
+// identifier and kills the first rule (e.g. the :root theme tokens; the 2026-06
+// incident). Used for both the unlayered defaults (cp-css.js) and the layered
+// mirror (wrapInLayer below).
+export function stripBom(content) {
+  return content.replace(/^\uFEFF/, "");
+}
+
 // Wrap a CSS file's contents in @layer openui { ... } if not already wrapped.
 // Idempotency check protects watch-mode and back-to-back builds.
 export function wrapInLayer(content) {
-  // Sass emits a UTF-8 BOM for files with non-ASCII output. At byte 0 the
-  // decoder strips it, but wrapping would push it inside the layer block,
-  // where U+FEFF parses as an identifier and kills the first rule
-  // (e.g. the :root theme tokens). Strip it before wrapping.
-  content = content.replace(/^\uFEFF/, "");
+  content = stripBom(content);
   if (content.trim() === "") return content;
   if (/^\s*@layer\s+openui\b/.test(content)) return content;
   return `@layer openui{${content}}`;
diff --git a/packages/react-ui/package.json b/packages/react-ui/package.json
index 570080efa..3dec6c192 100644
--- a/packages/react-ui/package.json
+++ b/packages/react-ui/package.json
@@ -2,7 +2,7 @@
   "type": "module",
   "name": "@openuidev/react-ui",
   "license": "MIT",
-  "version": "0.11.8",
+  "version": "0.11.9",
   "description": "Component library for Generative UI SDK",
   "main": "dist/index.cjs",
   "module": "dist/index.mjs",