[dolho]

Summary

• With no email provider configured, which is the default on a localhost install that skipped the Resend key, the sender falls back to console mode: the code goes to the backend log and the send reports success. The Login page said "We sent a 6-digit code", and the person waited for an email that never came.
• GET /api/auth/mode now carries email_delivery_available. It's an install-level flag, like ent#849's email_code_login_enabled, computed by EmailService.can_deliver():
  • false for console, an unknown provider, resend without a key (Settings or env), smtp without host/user/password, or sendgrid without a key;
  • true if the config can't be read, so the page then behaves exactly as today.
• When it's false, step 2 says instead:
  • no email was sent;
  • if the address may sign in here, its code is in the backend log, readable with docker compose logs backend;
  • an admin can use Admin Login (there's a button) and add a provider under Settings → Integrations.
• The "if" wording is deliberate: POST /api/auth/email/request answers the same for every address (SEC: User and Agent Enumeration via differential API responses #186), so the page can't claim a code exists. That endpoint never consults the flag (pinned by an AST test). The code itself is never rendered.
• New FAQ entry: "I requested a login code on localhost and nothing arrived — am I locked out?"

Changes

• src/backend/services/email_service.py: can_deliver().
• src/backend/routers/auth.py: email_delivery_available on /api/auth/mode.
• src/frontend/src/stores/auth.js: emailDeliveryAvailable (null or an older backend reads as "delivers").
• src/frontend/src/views/Login.vue: the notice, using status-warning tokens and BaseButton, and a useAdminLogin handler.
• Tests:
  • tests/unit/test_3655_email_delivery_flag.py: providers and keys, unreadable config, the mode flag, and the request handler never reading it. 8 fail and 2 error without the fix.
  • loginNoEmailProvider.spec.js: the copy, no six-digit number rendered, the Admin Login button, unchanged behaviour when email is delivered, and the store reading the flag.
• docs/user-docs/faq/getting-started.md.

Tested against a local instance

Provider console, no Resend key. This branch's four files were hot-swapped into the running stack and restored afterwards. A signed-out browser requested a code for a non-whitelisted address:

• Before: "📧 We sent a 6-digit code to nobody-3655@example.com".
• After: /api/auth/mode returns email_delivery_available: false, and the notice shows in both light and dark.

Screenshots were shared with the reviewer separately (not committed).

Test Plan

• test_3655_email_delivery_flag.py + test_ent849_email_code_policy.py + test_verification_email.py: 58 passed.
• Login specs + rawColorRatchet.spec.js: 29 passed. The colour ratchet holds: no raw palette classes added.
• With a Resend key saved in Settings, the page reads "We sent a 6-digit code" as before.

Fixes #3655

🤖 Generated with Claude Code

[vybe]

merge-train: batch validated on train PR #3781 (all Tier 1 + Tier 2 checks green).