Bit.Bcrdt 11.0.0-pre-10

Bit.Bcrdt

Real-time collaborative editing for .NET and Blazor, written natively in C#: a CRDT engine, a synchronization protocol, presence, offline-first persistence, selective undo and Blazor components. There is no JavaScript CRDT library underneath and no port of one - the engine, the wire format and the merge algorithm are all C#, and none of it needs JavaScript interop, so it runs the same in Blazor WebAssembly, Server and Hybrid, in a worker or in a console app.

Quick start

dotnet add package Bit.Bcrdt

using Bit.Bcrdt;

builder.Services.AddBitBcrdtServices(collaboration => collaboration
    .UseTransport(new BcrdtWebSocketTransportFactory("https://example.com/ws/bcrdt/{documentId}"))
    .UseStore(new BcrdtFileSystemDocumentStore("./documents")));

BcrdtCollaborativeDocument document = await collaboration.OpenAsync("design-review");

using (var transaction = document.BeginTransaction())
{
    document.Map.Set("title", "Q3 planning");
    document.Array("attendees").Push("Ada", "Grace");
    document.Text("notes").Insert(0, "Agenda:\n");
}

Two people running that against the same document identifier both end up with the same document, whether they were online at the time or not. For the SignalR transport add Bit.Bcrdt.SignalR; for the relay a server maps, add Bit.Bcrdt.Server.

Blazor

@using Bit.Bcrdt
@using Bit.Bcrdt.Blazor

<BcrdtCollaborationScope DocumentId="notes-42" User="_me" Context="document">
    <BcrdtPresenceView Presence="document.Presence" />
    <BcrdtTextArea Text="@document.Text("body")" Presence="document.Presence" />
</BcrdtCollaborationScope>

@code {
    private readonly BcrdtCollaboratorInfo _me = new("u-1", "Ada", BcrdtPresenceService.SuggestColor("u-1"));
}

That is a working collaborative editor with live presence, automatic reconnection and offline support.

• BcrdtCollaborationScope opens a document for its content, cascades it, and closes it again.
• BcrdtTextArea edits a BcrdtText: what the user types becomes the minimal CRDT edit, remote edits arrive without moving the caret or overwriting keystrokes still in flight, and the caret is published through presence.
• BcrdtPresenceView lists the people on a document.
• BcrdtComponentBase marshals change notifications onto the renderer and coalesces them onto a frame budget, and disposes its subscriptions with the component - the base for your own collaborative components.

No stylesheet to reference and no script to add: the one small module BcrdtTextArea needs is imported on demand. Works in Blazor WebAssembly, Server, Web App (including prerendering) and Hybrid.

Features

• A YATA-family sequence CRDT with run-length-encoded blocks: BcrdtText (with rich-text marks), BcrdtArray, BcrdtMap and BcrdtSet, nestable inside each other.
• Incremental binary updates that merge without a document, and a symmetric, loss-, duplication- and reorder-tolerant sync protocol with jittered reconnection - offline work flows both ways on reconnect, deletions included.
• Presence: who is here, colours, and carets and selections anchored to content rather than to indices.
• Append-only, checksummed persistence with compaction; in-memory and file-system stores.
• Selective undo that reverses your own edits and leaves everyone else's alone.
• Snapshots that restore any point in a document's history.
• BcrdtTextSynchronizer and BcrdtTextInputBinding, which turn an input's whole new value into the minimal edit.
• In-memory and WebSocket client transports; every seam - transport, store, client identity - is an interface.
• .NET 8, 9 and 10; trim- and AOT-safe for the collaborative value model.

For AI agents

The demo site hosts an MCP server at https://bcrdt.bitplatform.dev/mcp (also served through https://bitplatform.dev/mcp) that answers from the shipped library: its API, its guide, the demo's working pages, and a merge inspector that runs the real engine.

Documentation

The full guide - choosing a data type, documents and transactions, input bindings, presence, offline and reconnection, persistence, undo, hosting models, transports and relays, extending the library and the architecture - is in the Bcrdt README. See it running at bcrdt.bitplatform.dev.