CRDTMap

A map of named CRDT values. Each key holds an independent CRDT that syncs automatically.

A CRDTMap is a collaborative map where each key holds its own independent CRDT (GCounter, PNCounter, ORSet, LwwRegister, or Presence). The type of each key is fixed at first write. Merge is performed per-key — keys are independent and never conflict with each other.

Use this when you need a structured document with multiple independent fields, each with their own conflict resolution semantics.

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Basic usage

const doc = client.crdtmap("doc:homepage");

// Each key has its own CRDT type
doc.lwwSet("title", "My Page");
doc.incrementCounter("views");

doc.onChange(value => {
  console.log("title:", value.title);
  console.log("views:", value.views);
});

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Per-key CRDT types

Each key is permanently bound to its CRDT type at first write. Sending an operation of the wrong type to an existing key is rejected by the server.

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LWW-Register key

doc.lwwSet("title", "Hello World");
// value.title → { value: "Hello World", updatedAtMs: ..., author: ... }

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GCounter key

doc.incrementCounter("views");
doc.incrementCounter("views", 5);
// value.views → { total: 6, counts: { "1": 6 } }

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PNCounter key

doc.incrementPNCounter("score", 10);
doc.decrementPNCounter("score", 3);
// value.score → { value: 7, pos: { "1": 10 }, neg: { "1": 3 } }

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ORSet key

import { randomUUID } from "crypto";

const tag = new Uint8Array(Buffer.from(randomUUID().replace(/-/g, ""), "hex"));
doc.orsetAdd("tags", "typescript", tag);
// value.tags → { elements: ["typescript"] }

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API

Method	Description
value()	Returns snapshot of the full map Record<string, unknown>
get(key)	Returns the current value at key, or undefined
onChange(fn)	Subscribe to any change — returns unsubscribe function
stream()	Returns an Effect Stream<CrdtMapValue> that emits on every change
lwwSet(key, value)	Write a LWW-Register value
incrementCounter(key, amount?)	Increment a GCounter key (default 1)
incrementPNCounter(key, amount?)	Increment a PNCounter key (default 1)
decrementPNCounter(key, amount?)	Decrement a PNCounter key (default 1)
orsetAdd(key, element, tag)	Add an element to an ORSet key
orsetRemove(key, element, knownTags)	Remove an element from an ORSet key

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Merge semantics

Each key is merged independently using its inner CRDT’s lattice join. Two replicas that each update different keys will converge without conflict. Two replicas that update the same key converge using that key’s CRDT semantics (e.g. LWW-Register: higher HLC wins; GCounter: max per client).

Keys are permanent — once created they cannot be deleted.