diff --git a/__tests__/fullstack-init-next-frontend-branch.test.ts b/__tests__/fullstack-init-next-frontend-branch.test.ts
new file mode 100644
index 0000000..b52fd1c
--- /dev/null
+++ b/__tests__/fullstack-init-next-frontend-branch.test.ts
@@ -0,0 +1,104 @@
+// Test file shares one TypeScript program with the rest of `__tests__/`
+// under ts-jest, so any top-level `const fs = require('fs')` clashes
+// with other files' globals (TS2451). The neighbouring
+// `fullstack-init-next-rename.test.ts` already owns the unprefixed
+// `fs` / `path` names, so this file requires Node's built-ins inside
+// the describe block where their scope is local. See the header
+// comment in `fullstack-init-next-rename.test.ts` for the same
+// rationale around `filesystem` / `patching`.
+
+/**
+ * `--next` defaults the frontend git ref to `nuxt-base-starter#next`.
+ *
+ * The `next` branch on `lenneTech/nuxt-base-starter` ships an auth
+ * `basePath` aligned with `nest-base` (`/api/auth`) instead of the
+ * `nest-server-starter` default (`/iam`). Without this default, the
+ * Better-Auth handshake between the experimental `--next` API and the
+ * cloned frontend lands on a 404 and the user has to discover
+ * `--frontend-branch next` themselves (LLM-test 2026-05-03 friction #5,
+ * blocker).
+ *
+ * Two invariants need to hold:
+ *
+ *   1. When `--next` is set and no explicit `--frontend-branch` is
+ *      supplied, init.ts derives `frontendBranch === 'next'` and
+ *      passes it through to `frontendHelper.setupNuxt`.
+ *   2. An explicit `--frontend-branch <ref>` always wins, including
+ *      under `--next`, so consumers can target a custom branch on
+ *      either the legacy or `next`-derived line.
+ *
+ * Without `--next`, behaviour is unchanged: `frontendBranch` falls
+ * back to `cliFrontendBranch || configFrontendBranch` and is
+ * `undefined` if neither is provided (clones the default branch).
+ *
+ * We assert against the source string (same style as
+ * `fullstack-init-next-rename.test.ts`) — running the full gluegun
+ * command in-process would require mocking out the entire frontend
+ * helper, git, and prompts surface, which adds maintenance cost
+ * without buying meaningful coverage for a one-liner derivation.
+ */
+describe('Fullstack init --next frontend branch default', () => {
+  // Lazy require to avoid colliding with the top-level `fs` / `path`
+  // declarations in other test files (see header comment).
+  // eslint-disable-next-line @typescript-eslint/no-require-imports
+  const nodeFs = require('fs');
+  // eslint-disable-next-line @typescript-eslint/no-require-imports
+  const nodePath = require('path');
+  const initSource: string = nodeFs.readFileSync(
+    nodePath.join(__dirname, '..', 'src', 'commands', 'fullstack', 'init.ts'),
+    'utf8',
+  );
+
+  test('frontendBranch derivation prefers explicit --frontend-branch over the --next default', () => {
+    // The derivation must explicitly check `cliFrontendBranch` first so
+    // an explicit `--frontend-branch <ref>` overrides the experimental
+    // default. We allow either a direct truthy/length check; what we
+    // care about is that `cliFrontendBranch` appears before the
+    // `experimental` ternary that supplies `'next'`.
+    const derivation = initSource.match(/const frontendBranch =[^;]*;/);
+    expect(derivation).not.toBeNull();
+    const expr = derivation![0];
+
+    // Explicit CLI flag is checked first.
+    expect(expr).toMatch(/cliFrontendBranch/);
+    // Experimental default falls through to 'next'.
+    expect(expr).toMatch(/experimental/);
+    expect(expr).toMatch(/'next'/);
+
+    // Sanity: `cliFrontendBranch` is referenced before `'next'` in the
+    // expression, so the explicit value wins.
+    const cliIdx = expr.indexOf('cliFrontendBranch');
+    const nextIdx = expr.indexOf("'next'");
+    expect(cliIdx).toBeGreaterThanOrEqual(0);
+    expect(nextIdx).toBeGreaterThan(cliIdx);
+  });
+
+  test('no --next flag preserves the legacy fallback (cli > config > undefined)', () => {
+    // The legacy `cliFrontendBranch || configFrontendBranch` chain must
+    // remain inside the new derivation so non-experimental users still
+    // get the default branch when neither flag nor config sets one.
+    const derivation = initSource.match(/const frontendBranch =[^;]*;/);
+    expect(derivation).not.toBeNull();
+    expect(derivation![0]).toMatch(/configFrontendBranch/);
+  });
+
+  test('frontendBranch is forwarded into frontendHelper.setupNuxt unchanged', () => {
+    // The single-line derivation only matters if it's the value that
+    // setupNuxt actually receives. Guard against a future refactor
+    // that re-derives a separate branch for the nuxt path and
+    // accidentally drops the experimental default.
+    const setupNuxtCall = initSource.match(/frontendHelper\.setupNuxt\([^)]*,\s*\{[\s\S]*?\}\)/);
+    expect(setupNuxtCall).not.toBeNull();
+    expect(setupNuxtCall![0]).toMatch(/branch:\s*frontendBranch/);
+  });
+
+  test('CLI usage hint mentions that --next implies the nuxt-base-starter next branch', () => {
+    // The non-interactive hint is the only documentation surface
+    // Claude Code / scripted consumers see for `--next`, so it must
+    // surface this implicit default. `--frontend-branch` overriding it
+    // is the well-known precedence rule and doesn't need to be
+    // restated here, but the hint must at least name the implicit
+    // default so users searching for "next branch" find it.
+    expect(initSource).toMatch(/--next[^]*?nuxt-base-starter[^]*?next/);
+  });
+});
diff --git a/src/commands/fullstack/init.ts b/src/commands/fullstack/init.ts
index fb7f8ec..f4385f4 100644
--- a/src/commands/fullstack/init.ts
+++ b/src/commands/fullstack/init.ts
@@ -37,7 +37,7 @@ const NewCommand: GluegunCommand = {
 
     // Hint for non-interactive callers (e.g. Claude Code)
     toolbox.tools.nonInteractiveHint(
-      'lt fullstack init --name <name> --frontend <nuxt|angular> --api-mode <Rest|GraphQL|Both> --framework-mode <npm|vendor> [--framework-upstream-branch <ref>] [--next] [--dry-run] --noConfirm',
+      'lt fullstack init --name <name> --frontend <nuxt|angular> --api-mode <Rest|GraphQL|Both> --framework-mode <npm|vendor> [--framework-upstream-branch <ref>] [--next: implies nuxt-base-starter#next unless --frontend-branch overrides] [--dry-run] --noConfirm',
     );
 
     // Check git
@@ -297,7 +297,12 @@ const NewCommand: GluegunCommand = {
 
     // Determine branches and copy/link paths with priority: CLI > config
     const apiBranch = cliApiBranch || configApiBranch;
-    const frontendBranch = cliFrontendBranch || configFrontendBranch;
+    // Under `--next`, default the nuxt-base-starter ref to the `next`
+    // branch — that branch ships an auth basePath (`/api/auth`) that
+    // matches the experimental nest-base API. Explicit
+    // `--frontend-branch` (or lt.config) still wins so consumers can
+    // target a custom branch on either line.
+    const frontendBranch = cliFrontendBranch || configFrontendBranch || (experimental ? 'next' : undefined);
     const apiCopy = cliApiCopy || configApiCopy;
     const apiLink = cliApiLink || configApiLink;
     const frontendCopy = cliFrontendCopy || configFrontendCopy;