Implicit Social Signup Implementation Plan

For agentic workers: REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (- [ ]) syntax for tracking.

Goal: Make every built-in social sign-in create an unknown user automatically while preserving the global signup restriction.

Architecture: Use Better Auth's native implicit-signup behavior by removing the provider-level opt-out. Delete the client-side requestSignUp distinction so every page uses the same social sign-in call, while disableSignUp: env.FLAG_DISABLE_SIGNUPS remains the server-enforced hard stop.

Tech Stack: TypeScript, Better Auth 1.6.26, React 19, Vitest, pnpm

Global Constraints

• Do not add dependencies or new abstractions.
• Apply the behavior to Google, GitHub, and LinkedIn.
• Leave custom OAuth and passkey behavior unchanged.
• Keep FLAG_DISABLE_SIGNUPS authoritative on the server.

File Structure

• packages/auth/src/config.test.ts: Characterizes Reactive Resume's built-in social-provider signup policy.
• packages/auth/src/config.ts: Owns Better Auth provider configuration and the global signup restriction.
• apps/web/src/features/auth/components/social-auth.tsx: Starts social sign-in without page-specific signup intent.
• apps/web/src/features/auth/pages/register.tsx: Uses the shared social-auth component without signup-only props.

Task 1: Use Better Auth's Native Implicit Social Signup

Files:

• Create: packages/auth/src/config.test.ts
• Modify: packages/auth/src/config.ts:196-223
• Modify: apps/web/src/features/auth/components/social-auth.tsx:14-66,115-137
• Modify: apps/web/src/features/auth/pages/register.tsx:245

Interfaces:

• Consumes: auth.options.socialProviders, env.FLAG_DISABLE_SIGNUPS, and authClient.signIn.social({ provider, callbackURL }).

• Produces: One social-auth flow in which existing identities sign in, unknown identities sign up implicitly, and globally disabled signups remain rejected by Better Auth.

• Step 1: Write the failing configuration test

Create packages/auth/src/config.test.ts:

import { describe, expect, it } from "vitest";
import { env } from "@reactive-resume/env/server";
import { auth } from "./config";

describe("social provider signup policy", () => {
	it.each(["google", "github", "linkedin"] as const)(
		"allows implicit signup through %s while honoring the global signup restriction",
		(provider) => {
			const config = auth.options.socialProviders?.[provider];

			expect(config?.disableImplicitSignUp).toBeUndefined();
			expect(config?.disableSignUp).toBe(env.FLAG_DISABLE_SIGNUPS);
		},
	);
});

This test catches a provider being opted out of implicit signup or becoming detached from FLAG_DISABLE_SIGNUPS.

• Step 2: Run the test and verify the expected failure

Run:

pnpm --filter @reactive-resume/auth test -- src/config.test.ts

Expected: FAIL for Google, GitHub, and LinkedIn because disableImplicitSignUp is currently true, not undefined.

• Step 3: Enable native implicit signup and delete client-side signup intent

In packages/auth/src/config.ts, remove only the three disableImplicitSignUp: true properties. Keep each provider's existing line:

disableSignUp: env.FLAG_DISABLE_SIGNUPS,

In apps/web/src/features/auth/components/social-auth.tsx, delete SocialAuthProps, SocialSignInOptions, and getSocialSignInOptions. Change the component signature:

export function SocialAuth() {

Change the loading branch to:

{isLoading ? <SocialAuthSkeleton /> : <SocialAuthButtons providers={providers} />}

Remove requestSignUp from the button props and function parameter:

type SocialAuthButtonsProps = {
	providers: RouterOutput["auth"]["providers"]["list"];
};

function SocialAuthButtons({ providers }: SocialAuthButtonsProps) {

Replace the Google, GitHub, and LinkedIn calls with the native Better Auth input shape:

authClient.signIn.social({ provider: "google", callbackURL: "/dashboard" });
authClient.signIn.social({ provider: "github", callbackURL: "/dashboard" });
authClient.signIn.social({ provider: "linkedin", callbackURL: "/dashboard" });

In apps/web/src/features/auth/pages/register.tsx, change:

<SocialAuth requestSignUp />

to:

<SocialAuth />

Do not modify LoginPage; it already renders <SocialAuth />.

• Step 4: Run the focused test and verify it passes

Run:

pnpm --filter @reactive-resume/auth test -- src/config.test.ts

Expected: PASS for all three providers.

• Step 5: Run focused validation

Run:

pnpm --filter @reactive-resume/auth typecheck
pnpm --filter web typecheck
pnpm exec biome check packages/auth/src/config.test.ts packages/auth/src/config.ts apps/web/src/features/auth/components/social-auth.tsx apps/web/src/features/auth/pages/register.tsx

Expected: all commands exit successfully with no diagnostics and no file changes.

• Step 6: Commit the implementation

git add packages/auth/src/config.test.ts packages/auth/src/config.ts apps/web/src/features/auth/components/social-auth.tsx apps/web/src/features/auth/pages/register.tsx
git commit -m "fix(auth): allow implicit social signup"