## What & why
During onboarding the workspace subdomain was auto-generated at sign-up
and only editable later in Settings. This adds a subdomain picker to the
workspace-creation flow, with **live availability checking** and
**name-driven auto-fill**.
The subdomain is chosen **on the central sign-up domain, before the
redirect onto the workspace subdomain** — so there's no mid-onboarding
domain switch (which would otherwise force a re-auth, like the Settings
"this logs everyone out" flow). It works uniformly for credentials and
SSO, since workspace creation is a post-auth mutation.
## Flow
Authenticate → **Create a workspace** → new step (workspace name +
address with live availability + auto-fill, seeded from the work email)
→ workspace is created with the chosen subdomain → the single redirect
lands on the final subdomain → onboarding modal (name pre-filled).
## Changes
**twenty-shared**
- `getSubdomainSlugFromDisplayName` — friendly slug from a display name,
built on the existing `transliteration` package (also transliterates
non-Latin names, e.g. 日本語 → `ri-ben-yu`).
**twenty-server**
- `checkWorkspaceSubdomainAvailability(subdomain)` query
(workspace-agnostic, `UserAuthGuard`) → `{ isValid, available,
suggestedSubdomain }`.
- `SubdomainManagerService`: availability + suggestion logic with
friendly numbered suffixes (`acme`, `acme-2`, …) instead of random hex;
`generateSubdomain` reuses it.
- `signUpInNewWorkspace` accepts an optional `{ displayName, subdomain
}` input (validated; falls back to auto-generation when omitted —
backward compatible, so existing callers are unaffected). Concurrent
same-subdomain sign-ups return a clear "already taken" error instead of
a generic DB error.
**twenty-front**
- New `SignInUpStep.WorkspaceCreation` step +
`useWorkspaceSubdomainField` hook (debounced, stale-response-safe;
auto-fills from the name until the user edits it, with a one-click "use
suggested" when taken; ignores Enter during IME composition; surfaces a
clear error if the availability check fails).
- Onboarding modal name pre-filled from the chosen name.
## Testing
- Unit tests: shared slug util, the `useWorkspaceSubdomainField` hook
(real auto-fill/availability flows via `MockedProvider`), and the
workspace-creation component; existing sign-up tests still pass.
- Typecheck, lint, and format green across twenty-shared / twenty-server
/ twenty-front.
## Notes / out of scope
- No DB migration — the `subdomain` column already existed.
- Self-hosted single-workspace sign-up is unchanged; the step is gated
to multi-workspace (global scope).
- Low-priority follow-ups: length bounds on the subdomain / displayName
inputs, and an integration test for the availability query.
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Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Félix Malfait
eeed998c9e