diff --git a/app-modules/identity/src/Auth/Exceptions/OAuthFlowException.php b/app-modules/identity/src/Auth/Exceptions/OAuthFlowException.php
index 5ea3d836..5aa830ad 100644
--- a/app-modules/identity/src/Auth/Exceptions/OAuthFlowException.php
+++ b/app-modules/identity/src/Auth/Exceptions/OAuthFlowException.php
@@ -33,4 +33,12 @@ public static function tokenExchangeFailed(string $provider, string $error): sel
     {
         return new self(sprintf('Token exchange failed for "%s": %s', $provider, $error));
     }
+
+    public static function emailUnavailable(string $provider): self
+    {
+        return new self(sprintf(
+            'Could not resolve a primary verified email from "%s"; aborting login to avoid forking a duplicate user.',
+            $provider,
+        ));
+    }
 }
diff --git a/app-modules/identity/tests/Feature/Auth/HandleOAuthCallbackActionTest.php b/app-modules/identity/tests/Feature/Auth/HandleOAuthCallbackActionTest.php
new file mode 100644
index 00000000..cd8c6fd6
--- /dev/null
+++ b/app-modules/identity/tests/Feature/Auth/HandleOAuthCallbackActionTest.php
@@ -0,0 +1,172 @@
+<?php
+
+declare(strict_types=1);
+
+use App\Contracts\OAuthClientContract;
+use He4rt\Identity\Auth\Actions\HandleOAuthCallbackAction;
+use He4rt\Identity\Auth\DTOs\OAuthAccessDTO;
+use He4rt\Identity\Auth\DTOs\OAuthStateDTO;
+use He4rt\Identity\Auth\DTOs\OAuthUserDTO;
+use He4rt\Identity\Auth\Enums\OAuthIntent;
+use He4rt\Identity\ExternalIdentity\Enums\IdentityProvider;
+use He4rt\Identity\ExternalIdentity\Models\ExternalIdentity;
+use He4rt\Identity\Tenant\Models\Tenant;
+use He4rt\Identity\User\Models\User;
+use He4rt\IntegrationGithub\OAuth\GitHubOAuthClient;
+
+use function Pest\Laravel\actingAs;
+use function Pest\Laravel\assertDatabaseCount;
+
+function fakeOAuthAccess(): OAuthAccessDTO
+{
+    return new class('gh-access', 'gh-refresh', 3_600) extends OAuthAccessDTO
+    {
+        public static function make(array $payload): self
+        {
+            return new self('gh-access', 'gh-refresh', 3_600);
+        }
+    };
+}
+
+function fakeGithubUser(string $email, string $providerId): OAuthUserDTO
+{
+    return new class(fakeOAuthAccess(), $providerId, IdentityProvider::GitHub, 'octocat', 'Octo Cat', $email, avatarUrl: null) extends OAuthUserDTO
+    {
+        public static function make(OAuthAccessDTO $credentials, array $payload): self
+        {
+            return new self($credentials, '', IdentityProvider::GitHub, '', '', null, null);
+        }
+    };
+}
+
+/**
+ * Bind a stub GitHub client so the orchestrator never hits the network.
+ */
+function bindFakeGithubClient(OAuthUserDTO $githubUser): void
+{
+    app()->instance(GitHubOAuthClient::class, new readonly class($githubUser) implements OAuthClientContract
+    {
+        public function __construct(private OAuthUserDTO $githubUser) {}
+
+        public function redirectUrl(?OAuthStateDTO $state = null): string
+        {
+            return 'https://github.test/oauth';
+        }
+
+        public function auth(string $code): OAuthAccessDTO
+        {
+            return fakeOAuthAccess();
+        }
+
+        public function getAuthenticatedUser(OAuthAccessDTO $credentials): OAuthUserDTO
+        {
+            return $this->githubUser;
+        }
+    });
+}
+
+test('links a second provider to the logged-in user even when the email differs', function (): void {
+    // A user who originally signed up via Discord (discord@discord.com)...
+    $tenant = Tenant::factory()->create();
+    $discordUser = User::factory()->create(['email' => 'discord@discord.com']);
+
+    ExternalIdentity::factory()->create([
+        'tenant_id' => $tenant->id,
+        'model_type' => (new User)->getMorphClass(),
+        'model_id' => $discordUser->id,
+        'connected_by' => $discordUser->id,
+        'provider' => IdentityProvider::Discord,
+        'external_account_id' => 'discord-123',
+    ]);
+
+    actingAs($discordUser);
+
+    // ...now logs in with GitHub, whose account carries a *different* email.
+    bindFakeGithubClient(fakeGithubUser(email: 'github@github.com', providerId: 'gh-999'));
+
+    $state = new OAuthStateDTO(
+        intent: OAuthIntent::Link,
+        provider: IdentityProvider::GitHub,
+        panel: 'app',
+        tenant: $tenant->slug,
+        returnUrl: 'https://he4rt.test/app',
+    );
+
+    $result = resolve(HandleOAuthCallbackAction::class)
+        ->execute($state, IdentityProvider::GitHub, 'auth-code');
+
+    // The flow links to the existing logged-in user — it does not fork a new
+    // one, and the differing email is a non-event (no merge conflict).
+    expect($result->intent)->toBe(OAuthIntent::Link)
+        ->and($result->user->id)->toBe($discordUser->id)
+        ->and($result->mergeConflict)->toBeNull();
+
+    // The current user keeps their original email column untouched.
+    expect($discordUser->fresh()->email)->toBe('discord@discord.com');
+
+    // No user is created from the GitHub email — nothing was forked.
+    expect(User::query()->where('email', 'github@github.com')->exists())->toBeFalse();
+
+    // The GitHub identity is attached to the Discord user, and the GitHub email
+    // lives only in the identity metadata.
+    $githubIdentity = ExternalIdentity::query()
+        ->where('provider', IdentityProvider::GitHub)
+        ->where('external_account_id', 'gh-999')
+        ->first();
+
+    expect($githubIdentity)->not->toBeNull()
+        ->and($githubIdentity->model_id)->toBe($discordUser->id)
+        ->and($githubIdentity->metadata['email'])->toBe('github@github.com');
+});
+
+test('forks a separate account when a logged-out github login has a different email', function (): void {
+    // Same starting point — a Discord user (discord@discord.com).
+    $tenant = Tenant::factory()->create();
+    $discordUser = User::factory()->create(['email' => 'discord@discord.com']);
+
+    ExternalIdentity::factory()->create([
+        'tenant_id' => $tenant->id,
+        'model_type' => (new User)->getMorphClass(),
+        'model_id' => $discordUser->id,
+        'connected_by' => $discordUser->id,
+        'provider' => IdentityProvider::Discord,
+        'external_account_id' => 'discord-123',
+    ]);
+
+    // ...but this time they are LOGGED OUT (no actingAs) and sign in from the
+    // login page with GitHub, intent = Login. With no shared email and no prior
+    // GitHub link, there is nothing to correlate on, so a new account is forked
+    // (Option B: email is the only merge key on the Login path).
+    bindFakeGithubClient(fakeGithubUser(email: 'github@github.com', providerId: 'gh-999'));
+
+    $state = new OAuthStateDTO(
+        intent: OAuthIntent::Login,
+        provider: IdentityProvider::GitHub,
+        panel: 'app',
+        tenant: $tenant->slug,
+        returnUrl: 'https://he4rt.test/app',
+    );
+
+    $result = resolve(HandleOAuthCallbackAction::class)
+        ->execute($state, IdentityProvider::GitHub, 'auth-code');
+
+    // A brand-new user is created — NOT the existing Discord user.
+    expect($result->intent)->toBe(OAuthIntent::Login)
+        ->and($result->user->id)->not->toBe($discordUser->id)
+        ->and($result->user->email)->toBe('github@github.com');
+
+    // The original Discord account is left completely untouched.
+    expect($discordUser->fresh()->email)->toBe('discord@discord.com');
+
+    // The GitHub identity is attached to the new forked user, not the Discord one.
+    $githubIdentity = ExternalIdentity::query()
+        ->where('provider', IdentityProvider::GitHub)
+        ->where('external_account_id', 'gh-999')
+        ->first();
+
+    expect($githubIdentity)->not->toBeNull()
+        ->and($githubIdentity->model_id)->toBe($result->user->id)
+        ->and($githubIdentity->model_id)->not->toBe($discordUser->id);
+
+    assertDatabaseCount(User::class, 3);
+});
diff --git a/app-modules/integration-github/src/OAuth/GitHubOAuthClient.php b/app-modules/integration-github/src/OAuth/GitHubOAuthClient.php
index 8c8986bc..67659331 100644
--- a/app-modules/integration-github/src/OAuth/GitHubOAuthClient.php
+++ b/app-modules/integration-github/src/OAuth/GitHubOAuthClient.php
@@ -14,6 +14,7 @@
 use He4rt\IntegrationGithub\Transport\GitHubOAuthConnector;
 use He4rt\IntegrationGithub\Transport\Requests\OAuth\ExchangeCodeForToken;
 use He4rt\IntegrationGithub\Transport\Requests\Users\GetCurrentUser;
+use He4rt\IntegrationGithub\Transport\Requests\Users\GetUserEmails;
 
 final readonly class GitHubOAuthClient implements OAuthClientContract
 {
@@ -61,9 +62,39 @@ public function getAuthenticatedUser(OAuthAccessDTO $credentials): GitHubOAuthUs
         /** @var array<string, mixed> $userPayload */
         $userPayload = $response->json();
 
+        // GitHub's /user only exposes a *public* email, so it is null when the
+        // user keeps their address private. Recover the primary verified email
+        // from /user/emails (granted by the user:email scope); otherwise login
+        // can't match an existing account by email and forks a duplicate user.
+        // When even the fallback can't yield a primary+verified address there is
+        // nothing trustworthy to correlate on, so hard-fail instead of forking.
+        if (($userPayload['email'] ?? null) === null) {
+            $userPayload['email'] = $this->resolvePrimaryEmail($credentials->accessToken)
+                ?? throw OAuthFlowException::emailUnavailable('github');
+        }
+
         return GitHubOAuthUserDTO::make($credentials, $userPayload);
     }
 
+    private function resolvePrimaryEmail(string $accessToken): ?string
+    {
+        $response = $this->apiConnector->send(new GetUserEmails(
+            accessToken: $accessToken,
+        ));
+
+        if (!$response->ok()) {
+            return null;
+        }
+
+        // Only the single primary + verified address identifies the account. A
+        // GitHub user often has several verified emails (work, school, noreply),
+        // so "any verified" could match the wrong one — require both flags.
+        return $response->collect()
+            ->where('primary', operator: true)
+            ->where('verified', operator: true)
+            ->value('email');
+    }
+
     private function callbackUrl(): string
     {
         return mb_rtrim(config('app.url'), '/').'/auth/oauth/github';
diff --git a/app-modules/integration-github/src/Transport/Requests/Users/GetUserEmails.php b/app-modules/integration-github/src/Transport/Requests/Users/GetUserEmails.php
new file mode 100644
index 00000000..fb245e38
--- /dev/null
+++ b/app-modules/integration-github/src/Transport/Requests/Users/GetUserEmails.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace He4rt\IntegrationGithub\Transport\Requests\Users;
+
+use Saloon\Enums\Method;
+use Saloon\Http\Auth\TokenAuthenticator;
+use Saloon\Http\Request;
+
+final class GetUserEmails extends Request
+{
+    protected Method $method = Method::GET;
+
+    public function __construct(
+        private readonly string $accessToken,
+    ) {}
+
+    public function resolveEndpoint(): string
+    {
+        return '/user/emails';
+    }
+
+    protected function defaultAuth(): TokenAuthenticator
+    {
+        return new TokenAuthenticator($this->accessToken);
+    }
+}
diff --git a/app-modules/integration-github/tests/Feature/GitHubOAuthClientTest.php b/app-modules/integration-github/tests/Feature/GitHubOAuthClientTest.php
new file mode 100644
index 00000000..35f2b5b3
--- /dev/null
+++ b/app-modules/integration-github/tests/Feature/GitHubOAuthClientTest.php
@@ -0,0 +1,100 @@
+<?php
+
+declare(strict_types=1);
+
+use He4rt\Identity\Auth\Exceptions\OAuthFlowException;
+use He4rt\Identity\ExternalIdentity\Enums\IdentityProvider;
+use He4rt\IntegrationGithub\OAuth\DTO\GitHubOAuthAccessDTO;
+use He4rt\IntegrationGithub\OAuth\GitHubOAuthClient;
+use He4rt\IntegrationGithub\Transport\GitHubApiConnector;
+use He4rt\IntegrationGithub\Transport\GitHubOAuthConnector;
+use He4rt\IntegrationGithub\Transport\Requests\Users\GetCurrentUser;
+use He4rt\IntegrationGithub\Transport\Requests\Users\GetUserEmails;
+use Saloon\Http\Faking\MockClient;
+use Saloon\Http\Faking\MockResponse;
+
+/**
+ * @param  array<class-string, MockResponse>  $responses
+ */
+function githubOAuthClient(array $responses): GitHubOAuthClient
+{
+    $api = tap(
+        new GitHubApiConnector(),
+        fn (GitHubApiConnector $connector) => $connector->withMockClient(new MockClient($responses)),
+    );
+
+    return new GitHubOAuthClient(
+        oauthConnector: new GitHubOAuthConnector(clientId: 'cid', clientSecret: 'secret'),
+        apiConnector: $api,
+    );
+}
+
+/**
+ * @param  array<string, mixed>  $overrides
+ */
+function githubUser(array $overrides = []): MockResponse
+{
+    return MockResponse::make([
+        'id' => 48_625_433,
+        'login' => 'gvieira18',
+        'name' => 'Gabriel Vieira',
+        'email' => null,
+        'avatar_url' => 'https://avatars.githubusercontent.com/u/48625433',
+        ...$overrides,
+    ]);
+}
+
+test('uses the public /user email when GitHub exposes one', function (): void {
+    $user = githubOAuthClient([
+        GetCurrentUser::class => githubUser(['email' => 'public@example.com']),
+    ])->getAuthenticatedUser(GitHubOAuthAccessDTO::make(['access_token' => 'tok']));
+
+    expect($user->email)->toBe('public@example.com')
+        ->and($user->provider)->toBe(IdentityProvider::GitHub)
+        ->and($user->providerId)->toBe('48625433');
+});
+
+test('falls back to the primary verified email when /user email is private', function (): void {
+    $user = githubOAuthClient([
+        GetCurrentUser::class => githubUser(['email' => null]),
+        GetUserEmails::class => MockResponse::make([
+            ['email' => 'secondary@example.com', 'primary' => false, 'verified' => true],
+            ['email' => 'primary@example.com', 'primary' => true, 'verified' => true],
+            ['email' => 'unverified@example.com', 'primary' => false, 'verified' => false],
+        ]),
+    ])->getAuthenticatedUser(GitHubOAuthAccessDTO::make(['access_token' => 'tok']));
+
+    expect($user->email)->toBe('primary@example.com');
+});
+
+test('hard-fails when no email is primary', function (): void {
+    // Several verified addresses (work, school, noreply) but none primary —
+    // none can be picked, so login must abort instead of forking a duplicate.
+    expect(fn () => githubOAuthClient([
+        GetCurrentUser::class => githubUser(['email' => null]),
+        GetUserEmails::class => MockResponse::make([
+            ['email' => 'noreply@example.com', 'primary' => false, 'verified' => true],
+            ['email' => 'school@example.com', 'primary' => false, 'verified' => true],
+        ]),
+    ])->getAuthenticatedUser(GitHubOAuthAccessDTO::make(['access_token' => 'tok'])))
+        ->toThrow(OAuthFlowException::class);
+});
+
+test('hard-fails when the primary email is not verified', function (): void {
+    expect(fn () => githubOAuthClient([
+        GetCurrentUser::class => githubUser(['email' => null]),
+        GetUserEmails::class => MockResponse::make([
+            ['email' => 'primary-unverified@example.com', 'primary' => true, 'verified' => false],
+            ['email' => 'verified@example.com', 'primary' => false, 'verified' => true],
+        ]),
+    ])->getAuthenticatedUser(GitHubOAuthAccessDTO::make(['access_token' => 'tok'])))
+        ->toThrow(OAuthFlowException::class);
+});
+
+test('hard-fails when /user/emails is empty', function (): void {
+    expect(fn () => githubOAuthClient([
+        GetCurrentUser::class => githubUser(['email' => null]),
+        GetUserEmails::class => MockResponse::make([]),
+    ])->getAuthenticatedUser(GitHubOAuthAccessDTO::make(['access_token' => 'tok'])))
+        ->toThrow(OAuthFlowException::class);
+});