## Summary
Fixes#17941 — Saving a blank subdomain causes a redirect to
`.website.com`, effectively breaking the workspace.
**Root cause:** Three layers all fail to reject an empty string `""`:
1. **Frontend (`SettingsDomain.tsx`):** `SaveButton` has both
`onClick={onSave}` and `type="submit"`. The `onClick` fires first,
calling `handleSave()` directly without running Zod validation. So
`isDefined("")` returns `true`, the confirmation modal opens, and the
blank subdomain is submitted.
2. **Backend DTO (`update-workspace-input.ts`):** The `subdomain` field
has `@IsString()` + `@IsOptional()` but no pattern validation, so an
empty string passes the DTO layer.
3. **Backend service (`workspace.service.ts:152`):** `if
(payload.subdomain && ...)` — empty string is falsy in JS, so it skips
`validateSubdomainOrThrow()` entirely and writes `subdomain: ""` to the
database.
**The crash:** After save, the redirect logic does
`"myworkspace.website.com".replace("myworkspace", "")` →
`".website.com"`, sending the user to an invalid URL.
## Fix
- **Frontend:** Call `form.trigger()` at the start of `handleSave` to
run Zod validation regardless of whether the function was invoked via
`onClick` or `form.handleSubmit`. Returns early with validation error if
invalid.
- **Backend DTO:** Add `@Matches(/^[a-z0-9][a-z0-9-]{1,28}[a-z0-9]$/)`
to reject invalid subdomains at the request validation layer
(defense-in-depth).
- **Backend service:** Change `if (payload.subdomain && ...)` to `if
(isDefined(payload.subdomain) && ...)` so empty strings route through
`validateSubdomainOrThrow()` instead of being silently skipped.
## Test plan
- [x] Existing `is-subdomain-valid.util.spec.ts` tests pass (36/36)
- [x] TypeScript type checks pass for both `twenty-server` and
`twenty-front`
- [x] oxlint passes on all changed files
- [x] Prettier passes on all changed files
- [ ] Manual: Navigate to Settings > Domains, clear the subdomain field,
click Save — should show validation error, not redirect
---------
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: Charles Bochet <charles@twenty.com>
Co-authored-by: Charles Bochet <charlesBochet@users.noreply.github.com>
