When an action depends on daemon capabilities or other availability checks, never fail silently or hard-fail the whole UI. Instead: (1) gate capability-dependent parameters/requests so missing capabilities degrade gracefully, and (2) treat dependency outcomes as real failures—don’t return “handled/success” if the operation wasn’t actually performed; surface a user-visible toast/message. Practical rules: - Capability gating: Only pass parameters (e.g., `sourceType`) that trigger `requireCapability(...)` if the capability is present; otherwise omit the parameter or use a fallback query. - No false success: If a helper returns `boolean`/status (e.g., `createSideTask()`), check it. On `false`/unavailable, return a failure indicator consistent with the command flow and notify the user. - Keep failure paths actionable: provide a warning/error toast and avoid throwing the entire request when a less-fancy mode is acceptable. Example (combined pattern): ```ts if (directive.toLowerCase() === 'sider') { const ok = createSideTask(); if (!ok) pushToast('warning', t('sideTask.unavailable')); return true; } const listOpts: any = { /* ... */ }; if (hasCapability('session_source_metadata')) { listOpts.sourceType = WEB_SHELL_SESSION_SOURCE_TYPE; } // If capability is missing, omit sourceType to prevent request-wide failure. ```