diff --git a/docs/beta-checklist.md b/docs/beta-checklist.md
index 044365f..47858d9 100644
--- a/docs/beta-checklist.md
+++ b/docs/beta-checklist.md
@@ -56,7 +56,8 @@ This checklist ensures Clinch meets security, quality, and documentation standar
 - [x] Authorization code flow with PKCE support
 - [x] Refresh token rotation
 - [x] Token family tracking (detects replay attacks)
-- [x] All tokens HMAC-SHA256 hashed in database
+- [x] All tokens and authorization codes HMAC-SHA256 hashed in database
+- [x] TOTP secrets AES-256-GCM encrypted at rest (Rails credentials)
 - [x] Configurable token expiry (access, refresh, ID)
 - [x] One-time use authorization codes
 - [x] Pairwise subject identifiers (privacy)
@@ -130,8 +131,7 @@ This checklist ensures Clinch meets security, quality, and documentation standar
 
 ## Code Quality
 
-- [x] **RuboCop** - Code style and linting
-  - Configuration: Rails Omakase
+- [x] **StandardRB** - Code style and linting
   - CI: Runs on every PR and push to main
 
 - [x] **Documentation** - Comprehensive README
diff --git a/test/controllers/oidc_claims_security_test.rb b/test/controllers/oidc_claims_security_test.rb
new file mode 100644
index 0000000..20d9965
--- /dev/null
+++ b/test/controllers/oidc_claims_security_test.rb
@@ -0,0 +1,394 @@
+require "test_helper"
+
+class OidcClaimsSecurityTest < ActionDispatch::IntegrationTest
+  setup do
+    @user = User.create!(email_address: "claims_security_test@example.com", password: "password123")
+    @application = Application.create!(
+      name: "Claims Security Test App",
+      slug: "claims-security-test-app",
+      app_type: "oidc",
+      redirect_uris: ["http://localhost:4000/callback"].to_json,
+      active: true,
+      require_pkce: false
+    )
+
+    # Store the plain text client secret for testing
+    @application.generate_new_client_secret!
+    @plain_client_secret = @application.client_secret
+    @application.save!
+  end
+
+  def teardown
+    # Delete in correct order to avoid foreign key constraints
+    OidcRefreshToken.where(application: @application).delete_all
+    OidcAccessToken.where(application: @application).delete_all
+    OidcAuthorizationCode.where(application: @application).delete_all
+    OidcUserConsent.where(application: @application).delete_all
+    @user.destroy
+    @application.destroy
+  end
+
+  # ====================
+  # CLAIMS PARAMETER ESCALATION ATTACKS
+  # ====================
+
+  test "rejects claims parameter during authorization code exchange" do
+    # Create consent with minimal scopes (no profile, email, or admin access)
+    OidcUserConsent.create!(
+      user: @user,
+      application: @application,
+      scopes_granted: "openid",
+      granted_at: Time.current,
+      sid: "test-sid-123"
+    )
+
+    auth_code = OidcAuthorizationCode.create!(
+      application: @application,
+      user: @user,
+      redirect_uri: "http://localhost:4000/callback",
+      scope: "openid",
+      expires_at: 10.minutes.from_now
+    )
+
+    # ATTEMPT: Inject claims parameter during token exchange (ATTACK!)
+    # The client is trying to request 'admin' claim that they never got consent for
+    post "/oauth/token", params: {
+      grant_type: "authorization_code",
+      code: auth_code.plaintext_code,
+      redirect_uri: "http://localhost:4000/callback",
+      claims: '{"id_token":{"admin":{"essential":true}}}' # ← ATTACK!
+    }, headers: {
+      "Authorization" => "Basic " + Base64.strict_encode64("#{@application.client_id}:#{@plain_client_secret}")
+    }
+
+    # SHOULD: Reject the claims parameter - it's only allowed in authorization requests
+    assert_response :bad_request
+    error = JSON.parse(response.body)
+    assert_equal "invalid_request", error["error"], "Should reject claims parameter at token endpoint"
+    assert_match(/claims.*not allowed|unsupported parameter/i, error["error_description"], "Error should mention claims parameter not allowed")
+  end
+
+  test "rejects claims parameter during authorization code exchange with profile escalation" do
+    # Create consent with ONLY openid scope (no profile scope)
+    OidcUserConsent.create!(
+      user: @user,
+      application: @application,
+      scopes_granted: "openid",
+      granted_at: Time.current,
+      sid: "test-sid-123"
+    )
+
+    auth_code = OidcAuthorizationCode.create!(
+      application: @application,
+      user: @user,
+      redirect_uri: "http://localhost:4000/callback",
+      scope: "openid",
+      expires_at: 10.minutes.from_now
+    )
+
+    # ATTEMPT: Try to get profile claims via claims parameter without profile scope
+    post "/oauth/token", params: {
+      grant_type: "authorization_code",
+      code: auth_code.plaintext_code,
+      redirect_uri: "http://localhost:4000/callback",
+      claims: '{"id_token":{"name":null,"email":{"essential":true}}}'
+    }, headers: {
+      "Authorization" => "Basic " + Base64.strict_encode64("#{@application.client_id}:#{@plain_client_secret}")
+    }
+
+    # SHOULD: Reject the claims parameter
+    assert_response :bad_request
+    error = JSON.parse(response.body)
+    assert_equal "invalid_request", error["error"]
+  end
+
+  test "rejects claims parameter during refresh token grant" do
+    access_token = OidcAccessToken.create!(
+      application: @application,
+      user: @user,
+      scope: "openid"
+    )
+
+    refresh_token = OidcRefreshToken.create!(
+      application: @application,
+      user: @user,
+      oidc_access_token: access_token,
+      scope: "openid"
+    )
+
+    plaintext_refresh_token = refresh_token.token
+
+    # ATTEMPT: Inject claims parameter during refresh (ATTACK!)
+    # Trying to escalate to admin claims during refresh
+    post "/oauth/token", params: {
+      grant_type: "refresh_token",
+      refresh_token: plaintext_refresh_token,
+      claims: '{"id_token":{"admin":true,"role":{"essential":true}}}' # ← ATTACK!
+    }, headers: {
+      "Authorization" => "Basic " + Base64.strict_encode64("#{@application.client_id}:#{@plain_client_secret}")
+    }
+
+    # SHOULD: Reject the claims parameter
+    assert_response :bad_request
+    error = JSON.parse(response.body)
+    assert_equal "invalid_request", error["error"], "Should reject claims parameter at refresh token endpoint"
+    assert_match(/claims.*not allowed|unsupported parameter/i, error["error_description"])
+  end
+
+  test "rejects claims parameter during refresh token grant with custom claims escalation" do
+    # Setup: User has a custom claim at user level
+    @user.update!(custom_claims: {"role" => "user"})
+
+    access_token = OidcAccessToken.create!(
+      application: @application,
+      user: @user,
+      scope: "openid"
+    )
+
+    refresh_token = OidcRefreshToken.create!(
+      application: @application,
+      user: @user,
+      oidc_access_token: access_token,
+      scope: "openid"
+    )
+
+    plaintext_refresh_token = refresh_token.token
+
+    # ATTEMPT: Try to escalate role to admin via claims parameter
+    post "/oauth/token", params: {
+      grant_type: "refresh_token",
+      refresh_token: plaintext_refresh_token,
+      claims: '{"id_token":{"role":{"value":"admin"}}}' # ← ATTACK! Trying to override role value
+    }, headers: {
+      "Authorization" => "Basic " + Base64.strict_encode64("#{@application.client_id}:#{@plain_client_secret}")
+    }
+
+    # SHOULD: Reject the claims parameter
+    assert_response :bad_request
+    error = JSON.parse(response.body)
+    assert_equal "invalid_request", error["error"]
+  end
+
+  test "allows token exchange without claims parameter" do
+    # Create consent
+    OidcUserConsent.create!(
+      user: @user,
+      application: @application,
+      scopes_granted: "openid profile",
+      granted_at: Time.current,
+      sid: "test-sid-123"
+    )
+
+    auth_code = OidcAuthorizationCode.create!(
+      application: @application,
+      user: @user,
+      redirect_uri: "http://localhost:4000/callback",
+      scope: "openid profile",
+      expires_at: 10.minutes.from_now
+    )
+
+    # Normal token exchange WITHOUT claims parameter should work fine
+    post "/oauth/token", params: {
+      grant_type: "authorization_code",
+      code: auth_code.plaintext_code,
+      redirect_uri: "http://localhost:4000/callback"
+    }, headers: {
+      "Authorization" => "Basic " + Base64.strict_encode64("#{@application.client_id}:#{@plain_client_secret}")
+    }
+
+    assert_response :success
+    response_body = JSON.parse(response.body)
+    assert response_body.key?("access_token")
+    assert response_body.key?("id_token")
+  end
+
+  test "allows refresh without claims parameter" do
+    # Create consent for this application
+    OidcUserConsent.create!(
+      user: @user,
+      application: @application,
+      scopes_granted: "openid profile",
+      granted_at: Time.current,
+      sid: "test-sid-refresh-456"
+    )
+
+    access_token = OidcAccessToken.create!(
+      application: @application,
+      user: @user,
+      scope: "openid profile"
+    )
+
+    refresh_token = OidcRefreshToken.create!(
+      application: @application,
+      user: @user,
+      oidc_access_token: access_token,
+      scope: "openid profile"
+    )
+
+    plaintext_refresh_token = refresh_token.token
+
+    # Normal refresh WITHOUT claims parameter should work fine
+    post "/oauth/token", params: {
+      grant_type: "refresh_token",
+      refresh_token: plaintext_refresh_token
+    }, headers: {
+      "Authorization" => "Basic " + Base64.strict_encode64("#{@application.client_id}:#{@plain_client_secret}")
+    }
+
+    assert_response :success
+    response_body = JSON.parse(response.body)
+    assert response_body.key?("access_token")
+    assert response_body.key?("id_token")
+  end
+
+  # ====================
+  # CLAIMS PARAMETER IS AUTHORIZATION-ONLY
+  # ====================
+
+  test "claims parameter is only valid in authorization request per OIDC spec" do
+    # Per OIDC Core spec section 18.2.1, claims parameter usage location is "Authorization Request"
+    # This test verifies that claims parameter cannot be used at token endpoint
+
+    OidcUserConsent.create!(
+      user: @user,
+      application: @application,
+      scopes_granted: "openid",
+      granted_at: Time.current,
+      sid: "test-sid-123"
+    )
+
+    auth_code = OidcAuthorizationCode.create!(
+      application: @application,
+      user: @user,
+      redirect_uri: "http://localhost:4000/callback",
+      scope: "openid",
+      expires_at: 10.minutes.from_now
+    )
+
+    # Test various attempts to inject claims parameter
+    malicious_claims = [
+      '{"id_token":{"admin":true}}',
+      '{"id_token":{"email":{"essential":true}}}',
+      '{"userinfo":{"groups":{"values":["admin"]}}}',
+      '{"id_token":{"custom_claim":"custom_value"}}',
+      'invalid-json'
+    ]
+
+    malicious_claims.each do |claims_value|
+      post "/oauth/token", params: {
+        grant_type: "authorization_code",
+        code: auth_code.plaintext_code,
+        redirect_uri: "http://localhost:4000/callback",
+        claims: claims_value
+      }, headers: {
+        "Authorization" => "Basic " + Base64.strict_encode64("#{@application.client_id}:#{@plain_client_secret}")
+      }
+
+      # All should be rejected
+      assert_response :bad_request, "Claims parameter '#{claims_value}' should be rejected"
+      error = JSON.parse(response.body)
+      assert_equal "invalid_request", error["error"]
+    end
+  end
+
+  # ====================
+  # VERIFY CONSENT-BASED ACCESS IS ENFORCED
+  # ====================
+
+  test "token endpoint respects scopes granted during authorization" do
+    # Create consent with ONLY openid scope (no email, profile, etc.)
+    OidcUserConsent.create!(
+      user: @user,
+      application: @application,
+      scopes_granted: "openid",
+      granted_at: Time.current,
+      sid: "test-sid-123"
+    )
+
+    auth_code = OidcAuthorizationCode.create!(
+      application: @application,
+      user: @user,
+      redirect_uri: "http://localhost:4000/callback",
+      scope: "openid",
+      expires_at: 10.minutes.from_now
+    )
+
+    # Exchange code for tokens
+    post "/oauth/token", params: {
+      grant_type: "authorization_code",
+      code: auth_code.plaintext_code,
+      redirect_uri: "http://localhost:4000/callback"
+    }, headers: {
+      "Authorization" => "Basic " + Base64.strict_encode64("#{@application.client_id}:#{@plain_client_secret}")
+    }
+
+    assert_response :success
+    response_body = JSON.parse(response.body)
+    id_token = response_body["id_token"]
+
+    # Decode ID token to check claims
+    decoded = JWT.decode(id_token, nil, false).first
+
+    # Should only have required claims, not email/profile
+    assert_includes decoded.keys, "iss"
+    assert_includes decoded.keys, "sub"
+    assert_includes decoded.keys, "aud"
+    assert_includes decoded.keys, "exp"
+    assert_includes decoded.keys, "iat"
+
+    # Should NOT have claims that weren't consented to
+    refute_includes decoded.keys, "email", "Should not include email without email scope"
+    refute_includes decoded.keys, "email_verified", "Should not include email_verified without email scope"
+    refute_includes decoded.keys, "name", "Should not include name without profile scope"
+    refute_includes decoded.keys, "preferred_username", "Should not include preferred_username without profile scope"
+  end
+
+  test "refresh token preserves original scopes granted during authorization" do
+    # Create consent with specific scopes
+    OidcUserConsent.create!(
+      user: @user,
+      application: @application,
+      scopes_granted: "openid email",
+      granted_at: Time.current,
+      sid: "test-sid-refresh-123"
+    )
+
+    access_token = OidcAccessToken.create!(
+      application: @application,
+      user: @user,
+      scope: "openid email"
+    )
+
+    refresh_token = OidcRefreshToken.create!(
+      application: @application,
+      user: @user,
+      oidc_access_token: access_token,
+      scope: "openid email"
+    )
+
+    plaintext_refresh_token = refresh_token.token
+
+    # Refresh the token
+    post "/oauth/token", params: {
+      grant_type: "refresh_token",
+      refresh_token: plaintext_refresh_token
+    }, headers: {
+      "Authorization" => "Basic " + Base64.strict_encode64("#{@application.client_id}:#{@plain_client_secret}")
+    }
+
+    assert_response :success
+    response_body = JSON.parse(response.body)
+    id_token = response_body["id_token"]
+
+    # Decode ID token to verify scopes are preserved
+    decoded = JWT.decode(id_token, nil, false).first
+
+    # Should have email claims (from original consent)
+    assert_includes decoded.keys, "email", "Should preserve email scope from original consent"
+    assert_includes decoded.keys, "email_verified", "Should preserve email_verified scope from original consent"
+
+    # Should NOT have profile claims (not in original consent)
+    refute_includes decoded.keys, "name", "Should not add profile claims that weren't consented to"
+    refute_includes decoded.keys, "preferred_username", "Should not add preferred_username that wasn't consented to"
+  end
+end
diff --git a/test/controllers/oidc_prompt_login_test.rb b/test/controllers/oidc_prompt_login_test.rb
new file mode 100644
index 0000000..58ad427
--- /dev/null
+++ b/test/controllers/oidc_prompt_login_test.rb
@@ -0,0 +1,236 @@
+require "test_helper"
+
+class OidcPromptLoginTest < ActionDispatch::IntegrationTest
+  setup do
+    @user = users(:alice)
+    @application = applications(:kavita_app)
+    @client_secret = SecureRandom.urlsafe_base64(48)
+    @application.client_secret = @client_secret
+    @application.save!
+
+    # Pre-authorize the application so we skip consent screen
+    consent = OidcUserConsent.find_or_initialize_by(
+      user: @user,
+      application: @application
+    )
+    consent.scopes_granted ||= "openid profile email"
+    consent.save!
+  end
+
+  teardown do
+    # Clean up
+    OidcAccessToken.where(user: @user, application: @application).destroy_all
+    OidcAuthorizationCode.where(user: @user, application: @application).destroy_all
+  end
+
+  test "max_age requires re-authentication when session is too old" do
+    # Sign in to create a session
+    post "/signin", params: {
+      email_address: @user.email_address,
+      password: "password"
+    }
+
+    assert_response :redirect
+    follow_redirect!
+    assert_response :success
+
+    # Get first auth_time
+    get "/oauth/authorize", params: {
+      client_id: @application.client_id,
+      redirect_uri: @application.parsed_redirect_uris.first,
+      response_type: "code",
+      scope: "openid",
+      state: "first-state",
+      nonce: "first-nonce"
+    }
+
+    assert_response :redirect
+    first_redirect_url = response.location
+    first_code = CGI.parse(URI(first_redirect_url).query)["code"].first
+
+    # Exchange for tokens and extract auth_time
+    post "/oauth/token", params: {
+      grant_type: "authorization_code",
+      code: first_code,
+      redirect_uri: @application.parsed_redirect_uris.first,
+      client_id: @application.client_id,
+      client_secret: @client_secret
+    }
+
+    assert_response :success
+    first_tokens = JSON.parse(response.body)
+    first_id_token = OidcJwtService.decode_id_token(first_tokens["id_token"])
+    first_auth_time = first_id_token[0]["auth_time"]
+
+    # Wait a bit (simulate time passing - in real scenario this would be actual seconds)
+    # Then request with max_age=0 (means session must be brand new)
+    get "/oauth/authorize", params: {
+      client_id: @application.client_id,
+      redirect_uri: @application.parsed_redirect_uris.first,
+      response_type: "code",
+      scope: "openid",
+      state: "second-state",
+      nonce: "second-nonce",
+      max_age: "0"  # Requires session to be 0 seconds old (i.e., brand new)
+    }
+
+    # Should redirect to sign in because session is too old
+    assert_response :redirect
+    assert_redirected_to /signin/
+
+    # Sign in again
+    post "/signin", params: {
+      email_address: @user.email_address,
+      password: "password"
+    }
+
+    assert_response :redirect
+    follow_redirect!
+
+    # Should receive authorization code
+    assert_response :redirect
+    second_redirect_url = response.location
+    second_code = CGI.parse(URI(second_redirect_url).query)["code"].first
+
+    assert second_code.present?, "Should receive authorization code after re-authentication"
+
+    # Exchange second authorization code for tokens
+    post "/oauth/token", params: {
+      grant_type: "authorization_code",
+      code: second_code,
+      redirect_uri: @application.parsed_redirect_uris.first,
+      client_id: @application.client_id,
+      client_secret: @client_secret
+    }
+
+    assert_response :success
+    second_tokens = JSON.parse(response.body)
+    second_id_token = OidcJwtService.decode_id_token(second_tokens["id_token"])
+    second_auth_time = second_id_token[0]["auth_time"]
+
+    # The second auth_time should be >= the first (re-authentication occurred)
+    # Note: May be equal if both occur in the same second (test timing edge case)
+    assert second_auth_time >= first_auth_time,
+      "max_age=0 should result in a re-authentication. " \
+      "First: #{first_auth_time}, Second: #{second_auth_time}"
+  end
+
+  test "prompt=none returns login_required error when not authenticated" do
+    # Don't sign in - user is not authenticated
+
+    # Request authorization with prompt=none
+    get "/oauth/authorize", params: {
+      client_id: @application.client_id,
+      redirect_uri: @application.parsed_redirect_uris.first,
+      response_type: "code",
+      scope: "openid",
+      state: "test-state",
+      prompt: "none"
+    }
+
+    # Should redirect with error=login_required (NOT to sign-in page)
+    assert_response :redirect
+    redirect_url = response.location
+
+    # Parse the redirect URL
+    uri = URI.parse(redirect_url)
+    query_params = uri.query ? CGI.parse(uri.query) : {}
+
+    assert_equal "login_required", query_params["error"]&.first,
+      "Should return login_required error for prompt=none when not authenticated"
+    assert_equal "test-state", query_params["state"]&.first,
+      "Should return state parameter"
+  end
+
+  test "prompt=login forces re-authentication with new auth_time" do
+    # First authentication
+    post "/signin", params: {
+      email_address: @user.email_address,
+      password: "password"
+    }
+
+    assert_response :redirect
+    follow_redirect!
+    assert_response :success
+
+    # Get first authorization code
+    get "/oauth/authorize", params: {
+      client_id: @application.client_id,
+      redirect_uri: @application.parsed_redirect_uris.first,
+      response_type: "code",
+      scope: "openid",
+      state: "first-state",
+      nonce: "first-nonce"
+    }
+
+    assert_response :redirect
+    first_redirect_url = response.location
+    first_code = CGI.parse(URI(first_redirect_url).query)["code"].first
+
+    # Exchange for tokens and extract auth_time from ID token
+    post "/oauth/token", params: {
+      grant_type: "authorization_code",
+      code: first_code,
+      redirect_uri: @application.parsed_redirect_uris.first,
+      client_id: @application.client_id,
+      client_secret: @client_secret
+    }
+
+    assert_response :success
+    first_tokens = JSON.parse(response.body)
+    first_id_token = OidcJwtService.decode_id_token(first_tokens["id_token"])
+    first_auth_time = first_id_token[0]["auth_time"]
+
+    # Now request authorization again with prompt=login
+    get "/oauth/authorize", params: {
+      client_id: @application.client_id,
+      redirect_uri: @application.parsed_redirect_uris.first,
+      response_type: "code",
+      scope: "openid",
+      state: "second-state",
+      nonce: "second-nonce",
+      prompt: "login"
+    }
+
+    # Should redirect to sign in
+    assert_response :redirect
+    assert_redirected_to /signin/
+
+    # Sign in again (simulating user re-authentication)
+    post "/signin", params: {
+      email_address: @user.email_address,
+      password: "password"
+    }
+
+    assert_response :redirect
+    # Follow redirect to after_authentication_url (which is /oauth/authorize without prompt=login)
+    follow_redirect!
+
+    # Should receive authorization code redirect
+    assert_response :redirect
+    second_redirect_url = response.location
+    second_code = CGI.parse(URI(second_redirect_url).query)["code"].first
+
+    assert second_code.present?, "Should receive authorization code after re-authentication"
+
+    # Exchange second authorization code for tokens
+    post "/oauth/token", params: {
+      grant_type: "authorization_code",
+      code: second_code,
+      redirect_uri: @application.parsed_redirect_uris.first,
+      client_id: @application.client_id,
+      client_secret: @client_secret
+    }
+
+    assert_response :success
+    second_tokens = JSON.parse(response.body)
+    second_id_token = OidcJwtService.decode_id_token(second_tokens["id_token"])
+    second_auth_time = second_id_token[0]["auth_time"]
+
+    # The second auth_time should be >= the first (re-authentication occurred)
+    # Note: May be equal if both occur in the same second (test timing edge case)
+    assert second_auth_time >= first_auth_time,
+      "prompt=login should result in a later auth_time. " \
+      "First: #{first_auth_time}, Second: #{second_auth_time}"
+  end
+end
diff --git a/test/lib/duration_parser_test.rb b/test/lib/duration_parser_test.rb
new file mode 100644
index 0000000..6099f5e
--- /dev/null
+++ b/test/lib/duration_parser_test.rb
@@ -0,0 +1,136 @@
+require "test_helper"
+
+class DurationParserTest < ActiveSupport::TestCase
+  # Valid formats
+  test "parses seconds" do
+    assert_equal 1, DurationParser.parse("1s")
+    assert_equal 30, DurationParser.parse("30s")
+    assert_equal 3600, DurationParser.parse("3600s")
+  end
+
+  test "parses minutes" do
+    assert_equal 60, DurationParser.parse("1m")
+    assert_equal 300, DurationParser.parse("5m")
+    assert_equal 1800, DurationParser.parse("30m")
+  end
+
+  test "parses hours" do
+    assert_equal 3600, DurationParser.parse("1h")
+    assert_equal 7200, DurationParser.parse("2h")
+    assert_equal 86400, DurationParser.parse("24h")
+  end
+
+  test "parses days" do
+    assert_equal 86400, DurationParser.parse("1d")
+    assert_equal 172800, DurationParser.parse("2d")
+    assert_equal 2592000, DurationParser.parse("30d")
+  end
+
+  test "parses weeks" do
+    assert_equal 604800, DurationParser.parse("1w")
+    assert_equal 1209600, DurationParser.parse("2w")
+  end
+
+  test "parses months (30 days)" do
+    assert_equal 2592000, DurationParser.parse("1M")
+    assert_equal 5184000, DurationParser.parse("2M")
+  end
+
+  test "parses years (365 days)" do
+    assert_equal 31536000, DurationParser.parse("1y")
+    assert_equal 63072000, DurationParser.parse("2y")
+  end
+
+  # Plain numbers
+  test "parses plain integer as seconds" do
+    assert_equal 3600, DurationParser.parse(3600)
+    assert_equal 300, DurationParser.parse(300)
+    assert_equal 0, DurationParser.parse(0)
+  end
+
+  test "parses plain numeric string as seconds" do
+    assert_equal 3600, DurationParser.parse("3600")
+    assert_equal 300, DurationParser.parse("300")
+    assert_equal 0, DurationParser.parse("0")
+  end
+
+  # Whitespace handling
+  test "handles leading and trailing whitespace" do
+    assert_equal 3600, DurationParser.parse(" 1h ")
+    assert_equal 300, DurationParser.parse("  5m  ")
+    assert_equal 86400, DurationParser.parse("\t1d\n")
+  end
+
+  test "handles space between number and unit" do
+    assert_equal 3600, DurationParser.parse("1 h")
+    assert_equal 300, DurationParser.parse("5 m")
+    assert_equal 86400, DurationParser.parse("1 d")
+  end
+
+  # Case sensitivity - only lowercase units work (except M for months)
+  test "lowercase units work" do
+    assert_equal 1, DurationParser.parse("1s")
+    assert_equal 60, DurationParser.parse("1m")  # minute (lowercase)
+    assert_equal 3600, DurationParser.parse("1h")
+    assert_equal 86400, DurationParser.parse("1d")
+    assert_equal 604800, DurationParser.parse("1w")
+    assert_equal 31536000, DurationParser.parse("1y")
+  end
+
+  test "uppercase M for months works" do
+    assert_equal 2592000, DurationParser.parse("1M")  # month (uppercase)
+  end
+
+  test "returns nil for wrong case" do
+    assert_nil DurationParser.parse("1S")  # Should be 1s
+    assert_nil DurationParser.parse("1H")  # Should be 1h
+    assert_nil DurationParser.parse("1D")  # Should be 1d
+    assert_nil DurationParser.parse("1W")  # Should be 1w
+    assert_nil DurationParser.parse("1Y")  # Should be 1y
+  end
+
+  # Edge cases
+  test "handles zero duration" do
+    assert_equal 0, DurationParser.parse("0s")
+    assert_equal 0, DurationParser.parse("0m")
+    assert_equal 0, DurationParser.parse("0h")
+  end
+
+  test "handles large numbers" do
+    assert_equal 86400000, DurationParser.parse("1000d")
+    assert_equal 360000, DurationParser.parse("100h")
+  end
+
+  # Invalid formats - should return nil (not raise)
+  test "returns nil for invalid format" do
+    assert_nil DurationParser.parse("invalid")
+    assert_nil DurationParser.parse("1x")
+    assert_nil DurationParser.parse("abc")
+    assert_nil DurationParser.parse("1.5h")  # No decimals
+    assert_nil DurationParser.parse("-1h")    # No negatives
+    assert_nil DurationParser.parse("h1")     # Wrong order
+  end
+
+  test "returns nil for blank input" do
+    assert_nil DurationParser.parse("")
+    assert_nil DurationParser.parse(nil)
+    assert_nil DurationParser.parse("   ")
+  end
+
+  test "returns nil for multiple units" do
+    assert_nil DurationParser.parse("1h30m")  # Keep it simple, don't support this
+    assert_nil DurationParser.parse("1d2h")
+  end
+
+  # String coercion
+  test "handles string input" do
+    assert_equal 3600, DurationParser.parse("1h")
+    assert_equal 3600, DurationParser.parse(:"1h")  # Symbol
+  end
+
+  # Boundary validation (not parser's job, but good to know)
+  test "parses values outside typical TTL ranges without error" do
+    assert_equal 1, DurationParser.parse("1s")      # Below min access_token_ttl
+    assert_equal 315360000, DurationParser.parse("10y") # Above max refresh_token_ttl
+  end
+end
diff --git a/test/models/application_duration_parser_test.rb b/test/models/application_duration_parser_test.rb
new file mode 100644
index 0000000..4312895
--- /dev/null
+++ b/test/models/application_duration_parser_test.rb
@@ -0,0 +1,109 @@
+require "test_helper"
+
+class ApplicationDurationParserTest < ActiveSupport::TestCase
+  test "access_token_ttl accepts human-friendly durations" do
+    app = Application.new(access_token_ttl: "1h")
+    assert_equal 3600, app.access_token_ttl
+
+    app.access_token_ttl = "30m"
+    assert_equal 1800, app.access_token_ttl
+
+    app.access_token_ttl = "5m"
+    assert_equal 300, app.access_token_ttl
+  end
+
+  test "refresh_token_ttl accepts human-friendly durations" do
+    app = Application.new(refresh_token_ttl: "30d")
+    assert_equal 2592000, app.refresh_token_ttl
+
+    app.refresh_token_ttl = "1M"
+    assert_equal 2592000, app.refresh_token_ttl
+
+    app.refresh_token_ttl = "7d"
+    assert_equal 604800, app.refresh_token_ttl
+  end
+
+  test "id_token_ttl accepts human-friendly durations" do
+    app = Application.new(id_token_ttl: "1h")
+    assert_equal 3600, app.id_token_ttl
+
+    app.id_token_ttl = "2h"
+    assert_equal 7200, app.id_token_ttl
+  end
+
+  test "TTL fields still accept plain numbers" do
+    app = Application.new(
+      access_token_ttl: 3600,
+      refresh_token_ttl: 2592000,
+      id_token_ttl: 3600
+    )
+
+    assert_equal 3600, app.access_token_ttl
+    assert_equal 2592000, app.refresh_token_ttl
+    assert_equal 3600, app.id_token_ttl
+  end
+
+  test "TTL fields accept plain number strings" do
+    app = Application.new(
+      access_token_ttl: "3600",
+      refresh_token_ttl: "2592000",
+      id_token_ttl: "3600"
+    )
+
+    assert_equal 3600, app.access_token_ttl
+    assert_equal 2592000, app.refresh_token_ttl
+    assert_equal 3600, app.id_token_ttl
+  end
+
+  test "invalid TTL values are set to nil" do
+    app = Application.new(
+      access_token_ttl: "invalid",
+      refresh_token_ttl: "bad",
+      id_token_ttl: "nope"
+    )
+
+    assert_nil app.access_token_ttl
+    assert_nil app.refresh_token_ttl
+    assert_nil app.id_token_ttl
+  end
+
+  test "validation still works with parsed values" do
+    app = Application.new(
+      name: "Test",
+      slug: "test",
+      app_type: "oidc",
+      redirect_uris: "https://example.com/callback"
+    )
+
+    # Too short (below 5 minutes)
+    app.access_token_ttl = "1m"
+    assert_not app.valid?
+    assert_includes app.errors[:access_token_ttl], "must be greater than or equal to 300"
+
+    # Too long (above 24 hours for access token)
+    app.access_token_ttl = "2d"
+    assert_not app.valid?
+    assert_includes app.errors[:access_token_ttl], "must be less than or equal to 86400"
+
+    # Just right
+    app.access_token_ttl = "1h"
+    app.valid?  # Revalidate
+    assert app.errors[:access_token_ttl].blank?
+  end
+
+  test "can create OIDC app with human-friendly TTL values" do
+    app = Application.create!(
+      name: "Test App",
+      slug: "test-app",
+      app_type: "oidc",
+      redirect_uris: "https://example.com/callback",
+      access_token_ttl: "1h",
+      refresh_token_ttl: "30d",
+      id_token_ttl: "2h"
+    )
+
+    assert_equal 3600, app.access_token_ttl
+    assert_equal 2592000, app.refresh_token_ttl
+    assert_equal 7200, app.id_token_ttl
+  end
+end