Share context between your apps

You will declare one purpose, ask for the person's consent, send a setting to a peer app and check what flowed. It takes about 10 minutes. Nothing leaves the machine unless you declare a sink.

You need

• Two MainSDK apps of one owner on the same machine, mutual peers (apps.registry: on).

1. Declare the purpose

context:
  group: acme-learning
  identity: first-party
  purposes:
    personalise:
      description: "Use the same language and theme in every Acme app"
      attributes: [locale, theme]
      retention: 30d
      share-with: [prj_01JD8X]

2. Ask, then share

import { app } from "mainsdk";

const ctx = app().sharedContext;
const user = { id: "u_123" };
await ctx.consent.set(user, "personalise", true);
await ctx.shared.put({ purpose: "personalise", attributes: { locale: "hi-IN" } }, { user });

A peer without its own yes drops the message and answers held.

Check it worked

mainsdk context

It prints the group, each purpose with its share-with, and how many people consented and how many flows went out and came in. --json gives the same for a tool. It never shows a context id, a user id or a value.