# appcore-provider
[Minimal example](examples/basic.en.md) |
[Intermediate example](examples/intermediate.en.md)
**Responsibility:** implementation-neutral provider factories, registry,
deployment plans, coordination/job contracts and secret resolution.
**Internal dependencies:** `appcore-contracts`.
**Primary API:** `ProviderRole`, `ProviderContext`, `ProviderFactory`,
`ProviderRegistry`, `DeploymentProviderPlan`, provider errors/results,
zeroizing `ResolvedSecret` and `SecretProvider`; coordination schema V2,
in-memory/file coordination stores; shared-resource leases with fencing;
generic job spec/lease/completion/provider.
Filesystem leases use a per-resource lock file, an atomically replaced
versioned state file and a versioned epoch high-water sidecar. The sidecar is
persisted before publishing an active lease and survives release, restart and
interrupted acquisition, so an epoch is never reused. The epoch is a fencing token only
for writers that check it before writing. Shared filesystems that do not
provide reliable lock, rename, directory sync or cache-coherence semantics
cannot provide strong split-brain protection through this adapter alone.
Use it to compose explicit deployment providers. Do not register silent
fallbacks or put provider-specific SDK code in this crate.
**Maturity:** stable composition RC surface; distributed jobs remain outside the
first 1.0 operational profile.