> ## 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.

# Stability policy

> What Core promises not to break, and what it does not.

An extension is written against a moving platform. This page says which parts of
that platform hold still.

## What is covered

**`fapost/foundation`.** The contracts and DTOs in this package are the public
surface. They are what an extension is built against, and they are what Core
undertakes not to break within a major version.

**`fapost/support`.** Dependency-free primitives, on the same terms.

**Node contracts, by version.** A node's contract is versioned explicitly. A
published flow keeps reaching the handler version it was built against — see
[Versioning and compatibility](/extending/flow-nodes/versioning).

**State namespaces.** The meaning of `system.*`, `flow.*`, `rag.*`, and `module.*`
is fixed, along with who may write each.

## What is not covered

**Everything under `App\…`.** Core's domains, models, services, and jobs are
internal. They are refactored freely, and a `use App\…` in an extension is
expected to break.

<Warning>
  If a contract you need is not in `fapost/foundation`, reaching into `App\…` is
  not the workaround — it is a broken extension with a delayed failure. Propose
  the contract instead.
</Warning>

**The database schema.** Core's tables are an implementation detail of Core's
domains. Read module data through a
[data accessor](/extending/data-accessors), not through a query.

**The compiled front end.** The builder's internal component structure is not a
contract. Configure nodes through schema — see
[Builder UI extensions](/extending/builder-ui).

## Where the line is enforced

This is not an honour system. The dependency direction is checked by PHPat rules
that run in `composer run test:arch`: `foundation` and `support` may not reference
`App\…`, and the boundaries are verified on every run rather than at review time.

## While the platform is pre-1.0

The Solution and Plugin lifecycles are not product-complete. Packages are on `0.x`
versions, where `^0.1` accepts `0.1.*` only and adopting a new minor is a
deliberate constraint bump. Expect the surface to gain contracts rather than lose
them, and read [Development setup](/extending/development-setup) for how version
constraints behave in that range.