> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fapost.in/llms.txt
> Use this file to discover all available pages before exploring further.

# Tenant-aware execution

> Why tenant context is required and how it is carried.

Tenant is a base coordinate of the runtime. Core code that needs tenant context and
does not have it must **fail fast** rather than continue.

## Not allowed

* Branching on deployment shape inside Core runtime
* `if (isSingleTenant())` and anything shaped like it
* Falling back to a "default tenant" instead of an explicit context
* Direct landlord lookups from domains outside `Tenancy`

## Why no default tenant

A fallback turns a missing-context bug into a data-leak bug. Without it, code that
forgets to establish context throws immediately, in development, on the first run.
With it, the same code silently reads and writes another tenant's rows, and the
failure surfaces much later as data appearing where it should not.

Failing fast is the cheaper failure.

## Why no mode branching

A mode flag means two runtimes sharing one codebase, where only one of them is
exercised by any given test run. The branch that is not taken locally is the branch
that breaks in production. Core has one runtime model: multi-tenant, context
always present.

## Reaching landlord data

A domain that needs platform-level data takes a contract from
`Tenancy/Contracts`. Direct `DB::connection('landlord')` stays inside Tenancy
infrastructure.

This keeps the number of places that know about the landlord connection small
enough to audit, and it means a domain can be tested against a fake rather than a
second live database.

## Switching tenants

Switch through `TenantSwitcher::runForTenant()`, and restore in a `finally`:

```php theme={"theme":"one-dark-pro"}
$switcher->runForTenant($tenantId, function () {
    // work in that tenant's context
});
```

The restore is not optional bookkeeping — a Horizon worker survives the job, so a
context left set becomes the next job's starting state. See
[Long-lived worker safety](/contributing/worker-safety) for the rest of the
constraints that follow from a long-lived process.