# Handle failures without flattening them

This recipe shows the dispositions an application keeps separate from domain
fault through distributed execution and recovery.

The Rust and JSON APIs below are illustrative end-product examples.

## 1. Match the complete result

```rust,ignore
match client.orders().place(request).await {
    OperationResult::Succeeded(order) => show_order(order),
    OperationResult::Rejected(fault) => show_domain_fault(fault),
    OperationResult::Denied(denial) => request_access(denial),
    OperationResult::Cancelled(cancel) => show_cancelled(cancel),
    OperationResult::OutcomeUnknown(effect) => offer_reconciliation(effect),
    OperationResult::Unsupported(requirement) => explain_unsupported(requirement),
    OperationResult::Unsatisfied(proof) => explain_missing_realization(proof),
    OperationResult::Incompatible(details) => require_upgrade(details),
    OperationResult::Defect(defect) => report_defect(defect),
    OperationResult::Failed(failure) => show_recovery(failure),
}
```

## 2. Preserve nested causes

```json
{
  "kind": "failed",
  "stage": "communication",
  "fault": "deadline_exceeded",
  "cause": {
    "kind": "provider_failure",
    "provider": "acme_carrier.provider#AcmeShipmentCreate@1",
    "attempt": "provider-attempt:sha256:32a1…"
  },
  "effect": {
    "state": "outcome_unknown",
    "reference": "effect:sha256:77c2…"
  }
}
```

A communication timeout cannot erase that an external effect may have been
accepted.

## 3. Aggregate partial results honestly

```rust,ignore
let report = BatchResult {
    succeeded: vec![order_1, order_2],
    rejected: vec![(order_3, invalid_address)],
    unknown: vec![(order_4, effect_ref)],
    cancelled: vec![order_5],
};
```

One failed member does not rewrite completed members, and a summary count does
not replace per-item evidence.

## 4. Test negative paths

```console
one test --root OrdersApi --scenario authority-revoked-after-check
one test --root OrdersApi --scenario cancellation-after-dispatch
one test --root OrdersApi --scenario provider-response-lost
one test --root OrdersApi --scenario stale-evidence
one test --root OrdersApi --scenario unsupported-target
one test --root OrdersApi --scenario bounded-batch-partial-failure
```

See the [failure model](/one/reference/failure-model) and
[recovery and continuity](/one/lifecycle/recovery).