The useful definition
A local-first companion processes the private conversation path on the user's own machine by default. That changes what must leave the device and what kind of hardware the product needs.
Local-first is not offline-only
Licensing, updates, account access, commerce or optional connected services can still be online. The architectural question is whether the private relationship depends on sending every conversation to a remote model.
Storage matters as much as inference
Running a model locally is only half the privacy story. Private media, profile data, recovery design and logs also need clear boundaries.
The trade-off
The customer gains more local control, but the developer must support a wider range of GPUs, drivers, memory limits and model versions.
