Laravel Auth:attempt() will not persist login

# Laravel Auth Mystery Solved: Why `Auth::attempt()` Fails to Persist Login Across Requests As a senior developer working with the Laravel ecosystem, I frequently encounter subtle but frustrating issues related to session management and authentication persistence. Many developers run into the exact scenario you described: the login succeeds (`Auth::attempt()` returns true), but subsequent requests return `NULL` for the logged-in user, suggesting the session data isn't being carried over correctly. This is rarely a flaw in the core authentication logic itself; instead, it almost always points to a configuration mismatch, particularly when dealing with complex setups like microservices or subdomain architectures (e.g., an AngularJS frontend and a separate Laravel API). Let’s dive into why this happens and how to fix it using the provided context. ## The Anatomy of the Session Persistence Problem Your observation highlights a crucial distinction between successful credential validation and successful session persistence: 1. **`Auth::attempt()` Success:** This function successfully verifies the credentials against the database and, crucially, sets up the necessary session mechanism (usually by placing an identifier into the session store). 2. **Subsequent `Auth::user()` Failure:** If subsequent requests fail to retrieve the user, it means that the session data created during the login is not being correctly read back on the next request. You correctly noted that basic `Session::put()` and `Session::get()` work, which confirms that your underlying session driver (database in your case) is functional. The problem lies in how Laravel's default authentication guard interacts with the session mechanism across separate service boundaries. The suspicion regarding subdomain separation (`app.mydomain.com` vs. `api.mydomain.com`) is highly relevant. When dealing with distinct domains, cookies and sessions become subject to strict cross-origin policies, which can easily break persistence if not explicitly configured. ## Deep Dive into Session Configuration for Subdomains The solution hinges on correctly configuring the session driver settings, especially regarding cookie handling, as this governs how state is transmitted between the client and the server. Reviewing your provided configuration: ```php 'session' => array( // ... other settings 'cookie' => 'laravel_session', 'path' => '/', 'domain' => null, // <-- Potential Issue Area // ... ), ``` When running on separate subdomains, the default behavior might not be sufficient for sharing session state if strict cross-origin security is enforced. ### The Fix: Explicitly Setting the Domain For applications split across subdomains, you often need to explicitly define the domain for cookies so they are shared correctly across the application structure without causing conflicts or being rejected by the browser's security policies. If your frontend and backend share a root domain, setting the `domain` option is vital. While you currently have `'domain' => null`, enabling it (or setting it to your main domain) forces Laravel to manage the session cookie scope correctly for