# Enable Nexus and open a Rift

Prerequisite: [world posture](posture.md). Nexus hosts the public room surface.
The two saved setup lessons give a complete activation path and separate the
process-wide Nexus configuration from the configuration consumed by one Rift.

## Configuration is not liveness

The Nexus factory returns a fresh, defaulted configuration. `nexus.activate(config)`
installs and finalizes it. The lesson checks `is_configured` and `is_activated`
separately, including after deactivation.

While Nexus is active its policy stays in force: `configure(...)`, and `activate(...)`
handed a different configuration, raise `RuntimeError` (since 0.2.8210), because live Rifts
were admitted under the installed policy. Call `nexus.deactivate()` first, then install
the new configuration; `nexus.activate()` alone re-enables the installed one.

For a Rift, create a new configuration, choose its space type and name, then pass
it to `create_rift(...)`. That configuration is consumed: a second Rift needs a
second configuration object. Registration and active state are distinct; the
opening lesson explicitly marks the Rift active and inactive.

## Choose the room for the job

Start with a [static room](read-only-rooms.md) for inspection. A newly opened Rift
has no assigned frames. Opening a room and attaching it to an eligible target are
separate operations. The [inspection walkthrough](inspection-walkthrough.md)
connects the setup to a real target.

The Rift owns its room. Give the application ownership of the Rift's lifetime and
clean it up when the inspection session ends.


## The workflow in code

These are the core steps from the saved example. Use its complete linked script for all class definitions and setup.

```{literalinclude} ../downloads/03_advanced/09_opening_a_rift.py
:language: python
:pyobject: main
:linenos:
```


## Runnable examples

- [Opening a rift](../examples/advanced/09-opening-a-rift.md) — Advanced 09
- [Nexus enablement](../examples/advanced/08-nexus-enablement.md) — Advanced 08
- [The room and its fixtures](../examples/advanced/10-the-room-and-its-fixtures.md) — Advanced 10
- [Static vs capability authority](../examples/advanced/11-static-vs-capability-authority.md) — Advanced 11

[All advanced examples](../examples/advanced/index.md) · [Level contents](index.md) · [Full contents](../contents.md)

[Canonical page source](https://github.com/Synaptic724/melder/blob/4b364a338debcb1c010d0f6e9dcbbabb62945ba0/docs/advanced/nexus.md)