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The Battery Health Panel is the first first-party extension on the new plugin host. It is a GCS-only plugin that reads the host’s normalized battery telemetry, runs an anomaly engine, and emits notifications when a rule fires. Source lives at altnautica/ADOSExtensions/extensions/battery-health-panel. This page walks through the parts that matter for plugin authors.

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Manifest

plugin:
  id: com.altnautica.battery-health-panel
  name: "ADOS Battery Health Panel"
  version: "1.0.0"
  license: "GPL-3.0-or-later"

compatibility:
  ados_version: ">=0.10.0"
  gcs_version: ">=0.5.0"
  profiles: ["drone"]

gcs:
  bundle: "gcs/plugin.bundle.js"
  isolation: "iframe-sandbox"
  permissions:
    - ui.slot.fc-tab
    - ui.slot.notification
    - telemetry.subscribe.battery
    - telemetry.subscribe.mavlink
    - recording.write
  contributes:
    panels:
      - id: battery-health-tab
        slot: fc.tab
        title: "Battery Health"
        order: 30
Six permissions, three contributes blocks, no agent half. Risk band: low (no vehicle.command, no host file system, no network).

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Entry point

import { definePlugin } from "@altnautica/plugin-sdk";
import { createBatteryStore } from "./batteryStore";
import type { BatterySample } from "./types";

const store = createBatteryStore();

definePlugin({
  id: "com.altnautica.battery-health-panel",
  version: "1.0.0",
  async mount(ctx) {
    await ctx.telemetry.subscribe<BatterySample>(
      "battery",
      (sample) => store.ingest(sample),
    );
    store.onAnomaly(async (fired) => {
      for (const event of fired) {
        await ctx.notifications.publish({
          channelId: "battery-anomaly",
          severity: event.severity,
          title: event.title,
          body: event.body,
        });
        await ctx.recording.mark({ label: event.title });
      }
    });
  },
});
definePlugin is the only SDK call. Everything else is plain TypeScript: a store, a rule engine, a render loop. The SDK gets out of the way.

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Anomaly rule

const ruleCellLow: Rule = ({ curr, config }) => {
  const min = minDefined(curr.cellVoltagesV);
  if (min === null || min >= config.lowCellVoltageV) return null;
  if (min < config.criticalCellVoltageV) return null;
  return mk("cell_low", curr, "warning", "Cell low", `${min.toFixed(2)} V`);
};
A rule is a pure function from (prev, curr, config) to AnomalyEvent | null. The store calls every rule on every new sample. Hysteresis is the store’s job: an anomaly stays in the live list until the underlying condition has been clear for at least 5 seconds.

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Testing without a host

The SDK ships a synthetic-host harness: 
import { createPluginHarness } from "@altnautica/plugin-sdk/harness";

const harness = createPluginHarness({
  grantedCapabilities: [
    "telemetry.subscribe.battery",
    "ui.slot.notification",
    "recording.write",
  ],
  mount: async (ctx) => {
    await ctx.telemetry.subscribe("battery", (s) => store.ingest(s));
    store.onAnomaly(async (fired) => {
      for (const e of fired) {
        await ctx.notifications.publish({ ... });
      }
    });
  },
});

await harness.start();
harness.pushTelemetry("battery", { cellVoltagesV: [3.9, 3.4, 3.9, 3.9], ... });
expect(harness.notifications).toHaveLength(1);
expect(harness.notifications[0]).toMatchObject({ severity: "warning" });
await harness.teardown();
The harness lets a single Vitest run validate the whole plugin without spinning up Mission Control or a real drone.

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Packing and installing

pnpm test
pnpm build
./scripts/pack.sh battery-health-panel
Drag dist/com.altnautica.battery-health-panel-1.0.0.adosplug into Mission Control -> Settings -> Plugins -> Install plugin. Approve the six declared permissions. The panel mounts under the FC tab.

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What is next