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

# Operating Lerian SLC

> Nuclea's settlement windows and grade horária, ICP-Brasil certificate custody and rotation, contingency and recovery, and the reconciliation grains behind Lerian SLC.

Lerian SLC runs against two operational realities of Nuclea's SLC: rigid daily settlement windows, and regulated ICP-Brasil credentials. It enforces the windows, manages the credentials under client custody, and reconciles at several grains.

## Settlement windows and grade horária

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Nuclea's SLC settles on **two rigid daily cycles** — a morning and an afternoon window. Lerian SLC models each window with a state machine — **PENDING → OPEN → PROCESSING → CLOSED** — and uses it to gate eligibility: an operation submitted outside its window is **rejected** (**ESLC0029**). Lerian SLC raises proactive alerts as a window approaches its cutoff.

## Certificates and custody

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Lerian SLC signs with the client's **ICP-Brasil A1, RSA-2048, exportable** certificate. Custody is selectable per deployment — a software key, a **PKCS#11 HSM**, a **cloud KMS**, or a per-certificate **Vault**.

* **SaaS deployments** use **client-side-wrapped key import** into a cloud KMS: the service never sees the private material, storing only the public certificate and a key reference.
* **Rotation is atomic**, with a **grace period** so in-flight files are not disrupted.
* **Expiry alerts** escalate at **30, 15, 7, and 1 day** before expiry, emitted as `certificate.expiring` events.

## Contingency and recovery

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* **Audited pass-through.** Client-pre-signed artifacts are accepted and forwarded under audit when needed.
* **Dead-letter queue.** Inbound RSFN messages that cannot be processed are parked for review, never dropped.
* **Retransmit and recovery endpoints.** A transmitted file can be retransmitted and recovered.

## Reconciliation

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Lerian SLC reconciles at several grains so state never drifts:

* **Per operation** — each operation is tracked by its NUliquid.
* **Per file** — each file is tracked through its lifecycle and its returns.
* **Per NUliquid** — the settlement identifier is queryable for about **30 days**.
* **Per clearing cycle** — the clearing position is reconciled per cycle, and **D0-versus-D+1** value divergence is detected and alerted.