Backend API

Backend API Development Guide

Extension API: @podman-desktop/api

The backend runs as a Podman Desktop extension in Node.js. All host interactions go through @podman-desktop/api, which is provided by the Podman Desktop runtime (not bundled — it's an external dependency).

import * as extensionApi from '@podman-desktop/api';

Check API

API signatures change across versions. Read the installed types directly:

1. Full API types: Read node_modules/@podman-desktop/api/index.d.ts
2. Current RPC contract: Read packages/shared/src/BootcAPI.ts
3. Current models: Read files in packages/shared/src/models/
4. Current messages: Read packages/shared/src/messages/Messages.ts
5. See existing usage: grep -r "extensionApi\." packages/backend/src/

Always verify method signatures against the actual type definitions before using them.

RPC Architecture

Frontend ↔ Backend communication uses a typed RPC proxy over webview postMessage.

Adding a New API Method

Step 1: Define in shared contract (packages/shared/src/BootcAPI.ts):

export abstract class BootcApi {
  // ... existing methods
  abstract myNewMethod(param: string): Promise<ResultType>;
}

Step 2: Implement in backend (packages/backend/src/api-impl.ts):

export class BootcApiImpl extends BootcApi {
  async myNewMethod(param: string): Promise<ResultType> {
    const result = await extensionApi.containerEngine.listImages();
    return transformResult(result);
  }
}

Step 3: Call from frontend (automatic — RPC proxy exposes all methods):

import { bootcClient } from '/@/api/client';
const result = await bootcClient.myNewMethod('value');

RPC Timeout

Default timeout is 5 seconds per RPC call. For long-running operations, add the method name to the no-timeout list:

cat packages/shared/src/messages/NoTimeoutChannels.ts

Sending Notifications (Backend → Frontend)

Push data to the frontend via message IDs. See the current messages:

cat packages/shared/src/messages/Messages.ts

Send from backend:

this.panel.webview.postMessage({ id: Messages.MSG_HISTORY_UPDATE, body: data });

Frontend subscribes via RPC:

import { rpcBrowser } from '/@/api/client';
rpcBrowser.subscribe(Messages.MSG_NAVIGATE_BUILD, (path: string) => {
  router.goto(`/disk-images/build/${path}`);
});

Discovering APIs

APIs change across versions. Always read the source rather than relying on memory.

@podman-desktop/api

# Full API surface — the single source of truth
cat node_modules/@podman-desktop/api/index.d.ts

# Find how specific APIs are already used in this codebase
grep -rn "extensionApi\.\(containerEngine\|window\|provider\|navigation\|configuration\|process\|env\)" packages/backend/src/

Internal helpers

# Key backend modules — read these to find available helpers
ls packages/backend/src/*.ts
ls packages/shared/src/models/

Checklist: Adding a New Backend Feature

1. Add abstract method to packages/shared/src/BootcAPI.ts
2. Implement in packages/backend/src/api-impl.ts
3. If long-running (>5s), add to NoTimeoutChannels.ts
4. If it pushes data to frontend, add a message to Messages.ts
5. Add types/models in packages/shared/src/models/ if needed
6. Add telemetry for usage and errors
7. Write unit tests mocking @podman-desktop/api
8. Frontend can call via bootcClient.myNewMethod() — no wiring needed