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

# qxctl knowledge engines: Bind, Doctor, Migrate Registry

> Manage Symphony's protected user-scope engine binding profile with list, inspect, doctor, bind, unbind, and digest-bound migrate through qxctl.

The `qxctl knowledge engines ...` grammar manages the protected user-scope `default` binding profile for Symphony's vector engines. It binds selected content for later reconciliation. It does not install, invoke, activate, dock, authenticate, authorize, or apply an engine.

## Commands

```bash Engines grammar theme={null}
qxctl knowledge engines list
qxctl knowledge engines inspect
qxctl knowledge engines doctor
qxctl knowledge engines bind    --expected-registry-digest absent|DIGEST ...
qxctl knowledge engines unbind  --expected-registry-digest DIGEST ...
qxctl knowledge engines migrate --expected-registry-digest DIGEST ...
```

Supply `absent` for the first v2 registry mutation or the exact digest reported by `list` for later mutations. Every mutation is compare-and-swap against that digest.

## v1 to v2 migration

<Warning>
  Valid v1 registry state remains readable. Migration to v2 is a separate exact compare-and-swap and is never a version-selection operation. Do not treat migration as an upgrade path for engine selection.
</Warning>

* `list` and `inspect` continue to work on v1 evidence.
* `migrate` produces a linked v2 generation without discarding v1 truth.
* After migration, use v2 digests for future mutations.

## What a bind is

A bind selects exact content for later reconciliation by the coordinator. It:

* Does not install an engine
* Does not invoke or activate an engine
* Does not dock an engine with Maestro
* Does not authenticate a caller
* Does not authorize apply

## Related surfaces

<CardGroup cols={2}>
  <Card title="qxctl reconcile" icon="arrows-rotate" href="/symphony/symphony/qxctl/reconcile">
    Reconcile bound content with a coordinator.
  </Card>

  <Card title="qxctl lifecycle" icon="rotate" href="/symphony/symphony/qxctl/lifecycle">
    Lifecycle plans that use bound engines.
  </Card>

  <Card title="Maestro" icon="chalkboard-user" href="/symphony/symphony/governance/maestro">
    Presence authority that records docking, not bindings.
  </Card>

  <Card title="Engines overview" icon="cube" href="/symphony/symphony/engines/overview">
    Independently installable vector engines.
  </Card>
</CardGroup>


## Related topics

- [qxctl knowledge: Cross-Vector Lifecycle Administration](/symphony/symphony/qxctl/knowledge.md)
- [qxctl: Symphony Agentic Administrative Command Line](/symphony/symphony/qxctl/overview.md)
- [SSFV: Symphony Semantic Feature Vector and Registry](/symphony/symphony/skv/ssfv.md)
- [SEV: Symphony Evolution Vector for Planned Changes](/symphony/symphony/skv/sev.md)
- [qxctl maestro: Read Symphony Receptor Presence Inventory](/symphony/symphony/qxctl/maestro.md)