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When you build multiple independent apps in your organization, they often need to talk to each other. A storefront that notifies a separately owned accounting product. A commerce app that requests shipments from a fulfillment system. A CRM that creates invoices when a deal closes. Before you wire cross-app calls, confirm the products should actually be separate. Audience- or device-specific experiences inside one product usually belong in Surfaces. Use When to Create a Separate App first; this page is the mechanism once that decision is yes. Cross-app communication lets your apps call each other through the Stardeck platform. You don’t need to manage URLs, secrets, or authentication between apps — the platform handles all of that.

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How It Works

Apps call each other by name, not by URL. The platform sits in the middle and handles routing, authentication, and permissions. Your apps never talk to each other directly. On every call, the platform checks permissions, authenticates the request, routes to the right deployment, and logs the call. Your apps never need to know each other’s URLs or secrets. When an app deploys, the platform automatically detects its API endpoints and makes them discoverable to other apps and agents. On every call, the platform checks permissions, authenticates the request, routes to the right deployment, and logs everything. Here’s an example of what that looks like in practice — a storefront notifying an independently owned accounting product, with accounting acknowledging the posted entry: This gives you:
  • Stable connections — apps find each other by project slug, so redeploying doesn’t break anything
  • No shared secrets — the platform authenticates every call on behalf of both apps
  • Permission control — you decide which apps can talk to each other
  • Call logs — every cross-app call is logged so you can see what’s happening

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Getting Started

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1. Set Up the APIs

Open the project chat for the app you want to make callable and ask the agent to expose APIs. You don’t need to specify routes or technical details:
The agent designs the endpoints, handles the documentation, and the platform automatically detects them.

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2. Grant Access

Go to the app’s Settings tab and open the Cross-App section. You have two options:
  • Allow all apps — any app in the org can read data from this app (quick for getting started)
  • Explicit grant — grant a specific app access, with control over whether it can read, write, or both
See Permissions & Grants for details.

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3. Connect the Apps

Open the project chat for the app that needs to call the other, and tell the agent what should happen:
The agent wires up the cross-app call in your code.

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4. Test It

You can test from the project chat:
Or ask Starcat from the org dashboard to coordinate across both apps.

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Agent Calling

You don’t have to set up cross-app calls through code at all. Starcat can discover endpoints, call APIs, and orchestrate data flows across your apps through conversation. Ask Starcat things like:
  • “What can I call on the invoicing app?”
  • “Get the latest orders from the storefront app”
  • “Check inventory on the warehouse app and update the storefront if anything is out of stock”
For Starcat to operate an app, that app needs Allow agent access turned on in its Cross-App settings. See Agent Cross-App Calling for the full guide.

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Next Steps

When to Create a Separate App

Confirm independence before choosing a cross-app mechanism

Permissions & Grants

Control which apps can talk to each other

Agent Calling

Let the AI agent make cross-app calls for you

Calls vs Shared Data Stores

Pick the right mechanism for independent apps