diff --git a/.gitignore b/.gitignore
index 8a4f401..074c3f5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,7 @@ node_modules/
 # build output (regenerated by `make install` / `make zip`)
 main.js
 styles.css
+.tailwind.css
 *.zip
 preview/bundle.js
 tests/.entry.ts
diff --git a/README.md b/README.md
index 9933dc9..425f521 100644
--- a/README.md
+++ b/README.md
@@ -38,7 +38,7 @@ Changing settings remounts open panels.
 ```
 bun install
 bun run dev            # css + esbuild watch
-bun run build          # svelte-check + css (minified) + bundle
+bun run build          # svelte-check + css (minified, scoped) + bundle
 bun run test           # vitest (theme rules) + tests/smoke.mjs (jsdom, fake gateway)
 bun run preview        # the panel in a browser, no Obsidian: http://localhost:4174/#<scene>
 make check             # ultracite + svelte-check
@@ -48,6 +48,8 @@ make zip
 
 Preview scenes (`#thread` default, `#switcher`, `#closed`, `#menu`, `#actions`, `#activity`, `#branch`, `#question`, `#deep`, `#empty`, `#offline`, `#stream`; suffix `-light` for the light theme). Width is the window: run headless Chrome with `--window-size=340,720` for the sidedock, `1100,720` for a tab, `390,800` for a phone. Set `VAULT=` or `THEME=` to preview against a community theme; `app.css` is read from the Obsidian install.
 
+`styles.css` is Tailwind output run through `scripts/scope-css.mjs`: every selector gets `:is(.beaver-root, .beaver-root *)` in front. Other Tailwind plugins (beaver-calendar for one) put their utilities into the same `utilities` cascade layer, and without the extra specificity whichever plugin loaded last would win - its `.hidden` over ours and the other way round.
+
 ## Install
 
 `make install VAULT=…` copies `manifest.json`, `main.js`, `styles.css`, `versions.json` into `<vault>/.obsidian/plugins/beaver`; then enable **Beaver** in Settings → Community plugins. On a phone, sync the four files with Obsidian Sync ("Installed community plugins") or any file sync, and point the settings at a URL the phone can reach.
diff --git a/biome.jsonc b/biome.jsonc
index 54b8d05..35c80aa 100644
--- a/biome.jsonc
+++ b/biome.jsonc
@@ -48,7 +48,7 @@
       }
     },
     {
-      "includes": ["tests/**", "preview/**"],
+      "includes": ["tests/**", "preview/**", "scripts/**"],
       "linter": {
         "rules": {
           "performance": {
diff --git a/package.json b/package.json
index 5e72841..36b67df 100644
--- a/package.json
+++ b/package.json
@@ -6,10 +6,10 @@
   "type": "module",
   "main": "main.js",
   "scripts": {
-    "build": "bun run check && bun run css -- --minify && node esbuild.config.mjs production",
+    "build": "bun run check && node scripts/css.mjs --minify && node esbuild.config.mjs production",
     "check": "svelte-check --tsconfig ./tsconfig.json --threshold error",
-    "css": "tailwindcss -i src/tailwind.css -o styles.css",
-    "css:watch": "tailwindcss -i src/tailwind.css -o styles.css --watch",
+    "css": "node scripts/css.mjs",
+    "css:watch": "node scripts/css.mjs --watch",
     "dev": "bun run css && node esbuild.config.mjs",
     "fix": "ultracite fix",
     "lint": "ultracite check",
diff --git a/scripts/css.mjs b/scripts/css.mjs
new file mode 100644
index 0000000..0ded834
--- /dev/null
+++ b/scripts/css.mjs
@@ -0,0 +1,54 @@
+// node scripts/css.mjs [--minify] [--watch]
+//
+// Tailwind writes to a scratch file; the scoped, optionally minified result
+// is what lands in styles.css. See scope-css.mjs for why the extra step.
+import { spawn, spawnSync } from "node:child_process";
+import { readFileSync, watch, writeFileSync } from "node:fs";
+import { join } from "node:path";
+import { scopeCss } from "./scope-css.mjs";
+
+const root = new URL("..", import.meta.url).pathname;
+const args = new Set(process.argv.slice(2));
+const minify = args.has("--minify");
+const watching = args.has("--watch");
+
+const input = join(root, "src/tailwind.css");
+const scratch = join(root, ".tailwind.css");
+const output = join(root, "styles.css");
+const cli = join(root, "node_modules/.bin/tailwindcss");
+
+function finish() {
+  const built = readFileSync(scratch, "utf8");
+  writeFileSync(output, scopeCss(built, { minify }));
+  console.log(`css: wrote styles.css (${minify ? "minified, " : ""}scoped)`);
+}
+
+if (watching) {
+  writeFileSync(scratch, "");
+  const child = spawn(cli, ["-i", input, "-o", scratch, "--watch"], {
+    stdio: "inherit",
+  });
+  let timer = null;
+  watch(scratch, () => {
+    if (timer) {
+      clearTimeout(timer);
+    }
+    timer = setTimeout(() => {
+      timer = null;
+      try {
+        finish();
+      } catch (error) {
+        console.error("css:", error);
+      }
+    }, 60);
+  });
+  child.on("exit", (code) => process.exit(code ?? 0));
+} else {
+  const run = spawnSync(cli, ["-i", input, "-o", scratch], {
+    stdio: "inherit",
+  });
+  if (run.status !== 0) {
+    process.exit(run.status ?? 1);
+  }
+  finish();
+}
diff --git a/scripts/scope-css.mjs b/scripts/scope-css.mjs
new file mode 100644
index 0000000..fb2fcf7
--- /dev/null
+++ b/scripts/scope-css.mjs
@@ -0,0 +1,81 @@
+import { transform } from "lightningcss";
+
+/**
+ * Obsidian loads every plugin's stylesheet into one document, and Tailwind
+ * puts its utilities into a cascade layer called `utilities` in each of them.
+ * Layers with the same name merge, so another Tailwind plugin's
+ * `.hidden{display:none!important}` and this plugin's
+ * `@container … .\@min-\[30rem\]\:inline-block{…!important}` end up in the
+ * same layer with the same specificity, and whichever plugin loaded last
+ * wins. Prefixing every selector with `:is(.beaver-root, .beaver-root *)` adds a
+ * class of specificity that no unscoped utility can match, whatever the load
+ * order, while still reaching the view root itself and the portal layer,
+ * both of which carry `.beaver-root`.
+ *
+ * Theme variables move from `:root, :host` onto `.beaver-root` for the same
+ * reason: a later `:root{--spacing:…}` from someone else must not resize us.
+ */
+
+const ROOT = "beaver-root";
+
+const SCOPE = {
+  kind: "is",
+  selectors: [
+    [{ name: ROOT, type: "class" }],
+    [
+      { name: ROOT, type: "class" },
+      { type: "combinator", value: "descendant" },
+      { type: "universal" },
+    ],
+  ],
+  type: "pseudo-class",
+};
+
+function isPseudo(selector, kind) {
+  return (
+    selector.length === 1 &&
+    selector[0].type === "pseudo-class" &&
+    selector[0].kind === kind
+  );
+}
+
+function mentions(selector, name) {
+  for (const part of selector) {
+    if (part.type === "class" && part.name === name) {
+      return true;
+    }
+    if (part.selectors?.some((inner) => mentions(inner, name))) {
+      return true;
+    }
+  }
+  return false;
+}
+
+function scopeSelector(selector) {
+  if (isPseudo(selector, "root")) {
+    return [{ name: ROOT, type: "class" }];
+  }
+  // `:root, :host` is one rule; the root alone carries it, so :host goes.
+  if (isPseudo(selector, "host")) {
+    return [];
+  }
+  if (mentions(selector, ROOT)) {
+    return selector;
+  }
+  // `*` has to open a compound, and :is() takes that place now.
+  const rest = selector[0]?.type === "universal" ? selector.slice(1) : selector;
+  return [SCOPE, ...rest];
+}
+
+/** Rewrites a built stylesheet so its rules only reach the plugin's own DOM. */
+export function scopeCss(code, { minify = false } = {}) {
+  // The selector visitor, not the rule one: handing a whole rule back makes
+  // lightningcss re-read its declarations, and some of Tailwind's it cannot.
+  const result = transform({
+    code: Buffer.from(code),
+    filename: "styles.css",
+    minify,
+    visitor: { Selector: scopeSelector },
+  });
+  return result.code.toString();
+}
diff --git a/tests/scope-css.test.ts b/tests/scope-css.test.ts
new file mode 100644
index 0000000..ced7083
--- /dev/null
+++ b/tests/scope-css.test.ts
@@ -0,0 +1,67 @@
+import { describe, expect, it } from "vitest";
+import { scopeCss } from "../scripts/scope-css.mjs";
+
+const one = (css: string) => scopeCss(css).replace(/\s+/gu, " ").trim();
+
+describe("scoping the built stylesheet", () => {
+  it("prefixes a utility with the view root, keeping the root itself in reach", () => {
+    expect(one(".flex{display:flex!important}")).toBe(
+      ":is(.beaver-root, .beaver-root *).flex { display: flex !important; }"
+    );
+  });
+
+  it("outranks the same utility from another plugin's Tailwind", () => {
+    // Class specificity: theirs is (0,1,0); ours must be (0,2,0).
+    const out = one(".hidden{display:none!important}");
+    expect(out.startsWith(":is(.beaver-root, .beaver-root *).hidden")).toBe(
+      true
+    );
+  });
+
+  it("keeps pseudo-elements at the end where they are valid", () => {
+    expect(one(".x::placeholder{color:red}")).toBe(
+      ":is(.beaver-root, .beaver-root *).x::placeholder { color: red; }"
+    );
+    expect(one(".y::first-letter{t:1}")).toContain(".y:first-letter");
+  });
+
+  it("scopes rules nested in container queries and layers", () => {
+    const out = one(
+      "@layer utilities{@container (min-width:30rem){.a{display:inline-block!important}}}"
+    );
+    // lightningcss rewrites the query into range syntax; Obsidian's Chromium
+    // has understood that inside @container since container queries landed.
+    expect(out).toContain("@container (width >= 30rem)");
+    expect(out).toContain(":is(.beaver-root, .beaver-root *).a");
+  });
+
+  it("drops a leading universal selector instead of producing `:is()*`", () => {
+    const out = one("*,:before,::backdrop{--tw-a:initial}");
+    expect(out).toContain(":is(.beaver-root, .beaver-root *),");
+    expect(out).toContain(":is(.beaver-root, .beaver-root *):before");
+    expect(out).not.toContain("*)*");
+  });
+
+  it("moves theme variables from :root onto the view root", () => {
+    expect(one(":root,:host{--spacing:.25rem}")).toBe(
+      ".beaver-root { --spacing: .25rem; }"
+    );
+  });
+
+  it("leaves rules that already name the root alone", () => {
+    const reset = ".beaver-root.beaver-root button{cursor:pointer}";
+    expect(one(reset)).toBe(
+      ".beaver-root.beaver-root button { cursor: pointer; }"
+    );
+    expect(one(".theme-dark .beaver-root{--note:red}")).toBe(
+      ".theme-dark .beaver-root { --note: red; }"
+    );
+  });
+
+  it("scopes variant selectors without breaking their inner :where()", () => {
+    const out = one(".dark\\:bg-x:where(.theme-dark,.theme-dark *){b:1}");
+    expect(out).toBe(
+      ":is(.beaver-root, .beaver-root *).dark\\:bg-x:where(.theme-dark, .theme-dark *) { b: 1; }"
+    );
+  });
+});