# ADR-007: Command/Result Pattern

## Status
Accepted

## Context
We need a clear way to express intent to change state, execute business operations, and handle failures without exceptions.

## Decision
Use Command/Result pattern:

- **Command**: Plain object (DTO) containing all data needed to execute
- **Handler**: Contains orchestration logic, calls domain factories
- **Result**: Explicit success/failure, no exceptions for business errors

```
CreateMissionCommand
  ↓
CreateMissionHandler
  ↓
Result<MissionCreatedResult>
```

## Consequences

### Positive
- Clear intent: commands are named after use cases
- Testable: handlers are pure functions with injected repositories
- No exceptions for business logic
- Audit trail: commands can be logged
- Async-friendly

### Negative
- More boilerplate than direct service calls
- Need to handle Result type at every call site

## Related
- ADR-006: In-Memory Adapters for Testing