Badge count accurately reflects number of unread or active items

A badge count that drifts from reality undermines the entire notification contract. When bulk-delete actions, crash-interrupted decrements, or missed code paths leave the counter stale, users open the popup expecting unread items and find none — or worse, miss real items because the badge showed zero. ISO 25010:2011 functional-suitability.functional-correctness applies directly: the badge's job is accurate representation of state, and independent increment/decrement counters are structurally incapable of guaranteeing that.

Derive the badge count from a single source of truth on every update rather than maintaining a separate counter. Tie badge updates to chrome.storage.onChanged so any write to the underlying data automatically recalculates the displayed count.

async function updateBadge() {
  const { items } = await chrome.storage.local.get(['items']);
  const unread = (items ?? []).filter(item => !item.read).length;
  chrome.action.setBadgeText({
    text: unread > 0 ? String(unread) : ''
  });
}

chrome.storage.onChanged.addListener(() => updateBadge());

Never increment or decrement a counter variable directly — every code path that modifies items must go through storage, and onChanged handles the badge automatically.