---
title: Editing conflict
editUrl: https://github.com/Cratis/Arc/edit/main/Documentation/backend/csharp/chronicle/consistency/scenarios/editing-conflict.md
description: Reject a change when the document changed after the editor loaded it, with an explicit scope that carries the revision the client saw.
lastUpdated: 2026-10-15T00:00:00.000Z
---


Use this when the client loaded a document, someone else may have changed it, and a save must not overwrite that change.

| | |
| --- | --- |
| Rule | A rename is rejected if the document changed after the editor loaded it |
| Mechanism | An explicit scope built from the revision the client sent, returned with `EventsWithConcurrencyScopes` |
| Alternatives | A read model parameter when the conflict only matters within one request |
| Not | `concurrency: true` alone: it reads the tail after `Handle()`, so it cannot carry the revision the user saw |

```csharp
using Cratis.Arc.Commands.ModelBound;
using Cratis.Chronicle.Events;
using Cratis.Chronicle.EventSequences;
using Cratis.Chronicle.EventSequences.Concurrency;

public record DocumentId(string Value) : EventSourceId(Value);

[EventType]
public record DocumentTitleChanged(string Title);

[Command]
public record RenameDocument(DocumentId Document, string Title, ulong ExpectedRevision)
{
    public EventsWithConcurrencyScopes Handle() => new(
        [new(Document, new DocumentTitleChanged(Title))],
        [new(Document, new ConcurrencyScope(
            new EventSequenceNumber(ExpectedRevision),
            EventSourceId: Document,
            EventTypes: [typeof(DocumentTitleChanged).GetEventType()]))]);
}
```

```text
guard document: types=[DocumentTitleChanged], after <ExpectedRevision>
```

The scope fails the append if any `DocumentTitleChanged` for this document has a sequence number above `ExpectedRevision`. How the client learns the revision is part of your read model and query.

## Under read protection

If the command also reads a model of the same document, the scope must cover what the read watches and must not have been captured after it. Otherwise the command is refused with `ExplicitScopeDoesNotCoverReads`. The scope above covers a read of `DocumentTitleChanged` events. A read model that folds more types than the scope names needs a wider scope. [ARCCHR0036](/arc/backend/csharp/chronicle/code-analysis/arcchr0036/) reports it at build time.

## Related

- [Concurrency](/arc/backend/csharp/chronicle/commands/concurrency/#carrying-the-revision-used-by-the-decision)
- [Chronicle: explicit scopes](/chronicle/events/concurrency/)