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

# Adapters

# Adapters

***

## Reference · Adapters

> **Reference purpose** — Create provider seams that preserve framework lifecycle while isolating vendor protocol and credentials.

Adapters with narrow capabilities, explicit cleanup, and replaceable test doubles.

### Key concepts

<Columns cols={3}>
  <Card title="Capability" icon="sparkles">
    Small interface
  </Card>

  <Card title="Lifecycle" icon="shield-check">
    Open and close
  </Card>

  <Card title="Failure" icon="gauge-high">
    Translated category
  </Card>
</Columns>

### Reference model

```mermaid placement="top-right" theme={null}
flowchart LR
    contract[Application capability] --> adapter[Adapter] --> provider[Vendor API]
    adapter --> cleanup[Cleanup and timeout]
    adapter --> metrics[Provider metrics]
```

### Contract summary

| Property   | Definition          | Review question                                     |
| ---------- | ------------------- | --------------------------------------------------- |
| Capability | Small interface     | Avoid vendor-shaped application code.               |
| Lifecycle  | Open and close      | Prevent leaked handles.                             |
| Failure    | Translated category | Keep provider detail observable but not contagious. |

### Interpretation

An adapter is valuable when it makes provider choice reversible without weakening the application contract.

> **Reference note**
>
> The best adapter is boring at the call site and precise at the boundary.

### Implementation notes

| Engineering move        | Guidance                                                                     |
| ----------------------- | ---------------------------------------------------------------------------- |
| **Name the capability** | Describe what the application needs, not what one vendor happens to call it. |
| **Define lifecycle**    | Specify initialization, timeout, cancellation, close, and health behavior.   |
| **Map errors**          | Translate provider failures into stable application categories.              |
| **Prove replacement**   | Use a fake or second implementation to test the seam.                        |

### Decision lens

| Mode         | Practical emphasis                                    |
| ------------ | ----------------------------------------------------- |
| **Database** | Queries, transactions, pool, and migration ownership. |
| **Model**    | Generation, streaming, usage, and safety policy.      |
| **Storage**  | Upload, read, retention, authorization, and deletion. |

## Related topics

<Columns cols={3}>
  * [plug · **Register integrations**](/jeston/jeston/reference/integrations) — Read the focused guide for this boundary.
  * [database · **Apply a database adapter**](/jeston/jeston/platform/sql) — Read the focused guide for this boundary.
  * [diagram-project · **Review ownership**](/jeston/jeston/core/architecture) — Read the focused guide for this boundary.
</Columns>

## References

[1]: https://github.com/jeffersoncampos12p-dev/jeston "Jeston source repository"

[2]: https://www.npmjs.com/package/@kvantjs/jeston "Jeston package on npm"

[3]: https://nodejs.org/api/http.html "Node.js HTTP API"

[4]: https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal "AbortSignal Web API"

[5]: https://react.dev/reference/react-dom/server "React server rendering APIs"

[6]: https://www.typescriptlang.org/docs/handbook/intro.html "TypeScript handbook"