Always verify execution context (server vs client) before running client-specific operations in SSR applications. Many hydration errors and unexpected behaviors stem from client-only code executing during server-side rendering. Key practices: - Use `import.meta.client` checks before client-specific operations like polling, timers, or browser APIs - Ensure context availability before using composables that depend on client state - Be aware that some operations like `useHead()` may not work properly in server components without proper context Example from polling implementation: ```ts const startPolling = () => { if (import.meta.client && options.pollEvery && !pollTimer) { // Client-only polling logic } } ``` This prevents server-side execution of client-specific code and reduces hydration mismatches that can break SSR applications.