feat(desktop): searchable timezone dropdown in Settings → Chat

The timezone field was a free-text input with no guidance on format.
Users had to know the exact IANA identifier (e.g. America/New_York)
to configure it. Replace it with a searchable combobox built on
Popover + cmdk Command — the same stack as Shadcn's Combobox.

Backend:
- Add `_timezone_options()` to web_server.py (cached at import time,
  returns sorted zoneinfo.available_timezones() — ~598 identifiers)
- Add `"timezone"` to `_SCHEMA_OVERRIDES` with `type: "select"`,
  `options`, and `searchable: true`

Frontend:
- New `SearchableSelect` component (Popover + cmdk Command)
  — closed-world filterable dropdown for large option lists
- `ConfigField` routes to `SearchableSelect` when
  `schema.searchable === true` (explicit opt-in, no threshold)
- Add `searchable?: boolean` to `ConfigFieldSchema` type
- Add i18n keys: `searchPlaceholder`, `noResults`

The `searchable` flag is deterministic — no existing field is
affected unless explicitly opted in. Future large-list fields
can adopt the same pattern by adding `searchable: true` to their
schema override.

apps/desktop/src/app/settings/config-field.tsx

@@ -13,6 +13,7 @@ import { CONTROL_TEXT, EMPTY_SELECT_VALUE, FIELD_DESCRIPTIONS, FIELD_LABELS, FRE
 import { FallbackModelsField } from './fallback-models-field'
 import { fieldCopyForSchemaKey } from './field-copy'
 import { ListRow } from './primitives'
+import { SearchableSelect } from './searchable-select'
 
 /**
  * One generic config row: label + description resolved from the i18n field
@@ -93,6 +94,22 @@ export function ConfigField({
 
   const selectOptions = enumOptions ?? (schema.type === 'select' ? (schema.options ?? []).map(String) : undefined)
 
+  // Large closed-world lists (e.g. ~590 IANA timezones) get a searchable
+  // Popover + cmdk combobox instead of a closed Select dropdown.  The schema
+  // opt-in via `searchable: true` keeps this deterministic — no field
+  // accidentally triggers based on dynamic option count.
+  if (selectOptions && schema.searchable) {
+    return row(
+      <SearchableSelect
+        emptyMessage={c.noResults}
+        onChange={next => onChange(next)}
+        options={selectOptions.filter(o => o !== '')}
+        placeholder={c.searchPlaceholder}
+        value={String(value ?? '')}
+      />
+    )
+  }
+
   // Voice/model name fields are open-world (custom voice IDs, cloned voices,
   // brand-new model names) — render a free-input combobox where the known
   // options are datalist suggestions instead of a closed Select gate.

apps/desktop/src/app/settings/constants.ts

@@ -564,7 +564,7 @@ export const FIELD_DESCRIPTIONS: Record<string, string> = defineFieldCopy({
     repoScanRoots: 'Folders to scan. Leave empty to scan your home directory.',
     repoScanExcludePaths: 'Folders and their descendants to skip during repository discovery.'
   },
-  timezone: 'Used when Hermes needs local time context. Blank uses the system timezone.',
+  timezone: 'IANA timezone identifier. Blank uses the system timezone.',
   agent: {
     imageInputMode: 'Controls how image attachments are sent to the model.',
     maxTurns: 'Upper bound for tool-calling turns before Hermes stops a run.'

apps/desktop/src/app/settings/searchable-select.tsx

@@ -0,0 +1,109 @@
+import { useCallback, useRef, useState } from 'react'
+
+import { Command, CommandEmpty, CommandGroup, CommandInput, CommandItem, CommandList } from '@/components/ui/command'
+import { Popover, PopoverContent, PopoverTrigger } from '@/components/ui/popover'
+import { Codicon } from '@/components/ui/codicon'
+import { controlVariants } from '@/components/ui/control'
+import { cn } from '@/lib/utils'
+
+/**
+ * Searchable select for large option lists (e.g. ~590 IANA timezones).
+ * Built on Popover + cmdk Command — the same stack as Shadcn's Combobox.
+ *
+ * The trigger renders like the existing closed `<Select>` but opens into a
+ * searchable Command palette. Closed-world only: the user must pick from the
+ * list; arbitrary text entry is not supported.
+ *
+ * `ConfigField` routes here when `schema.searchable === true`.
+ */
+export function SearchableSelect({
+  value,
+  onChange,
+  options,
+  placeholder = 'Search…',
+  emptyMessage = 'No results found.'
+}: {
+  value: string
+  onChange: (value: string) => void
+  options: string[]
+  placeholder?: string
+  emptyMessage?: string
+}) {
+  const [open, setOpen] = useState(false)
+  const triggerRef = useRef<HTMLButtonElement>(null)
+
+  const handleSelect = useCallback(
+    (selected: string) => {
+      onChange(selected === value ? '' : selected)
+      setOpen(false)
+    },
+    [onChange, value]
+  )
+
+  const displayValue = value || placeholder
+
+  return (
+    <Popover onOpenChange={setOpen} open={open}>
+      <PopoverTrigger asChild>
+        <button
+          className={cn(
+            controlVariants(),
+            'flex items-center justify-between gap-2 whitespace-nowrap',
+            !value && 'text-muted-foreground'
+          )}
+          data-slot="searchable-select-trigger"
+          ref={triggerRef}
+          role="combobox"
+          type="button"
+          aria-expanded={open}
+        >
+          <span className="truncate">{displayValue}</span>
+          <Codicon className="shrink-0 opacity-60" name={open ? 'chevron-up' : 'chevron-down'} size="1rem" />
+        </button>
+      </PopoverTrigger>
+      <PopoverContent
+        align="start"
+        className="w-[var(--radix-popover-trigger-width)] p-0"
+        onOpenAutoFocus={e => {
+          // Let cmdk's CommandInput own focus, not the popover container.
+          e.preventDefault()
+        }}
+      >
+        <Command
+          filter={(value, search) => {
+            // cmdk's default filter is case-insensitive substring match on
+            // the item's value. For timezone-like values we also want to
+            // match segments after "/" so "york" matches "America/New_York".
+            const lower = search.toLowerCase()
+            const itemLower = value.toLowerCase()
+            if (itemLower.includes(lower)) return 1
+            // Match the segment after the last "/" (city name).
+            const slash = itemLower.lastIndexOf('/')
+            if (slash !== -1 && itemLower.slice(slash + 1).includes(lower)) return 1
+            return 0
+          }}
+        >
+          <CommandInput placeholder={placeholder} />
+          <CommandList>
+            <CommandEmpty>{emptyMessage}</CommandEmpty>
+            <CommandGroup>
+              {options.map(option => (
+                <CommandItem
+                  key={option}
+                  onSelect={() => handleSelect(option)}
+                  value={option}
+                >
+                  <Codicon
+                    className={cn('mr-2 size-4', option === value ? 'opacity-100' : 'opacity-0')}
+                    name="check"
+                  />
+                  {option}
+                </CommandItem>
+              ))}
+            </CommandGroup>
+          </CommandList>
+        </Command>
+      </PopoverContent>
+    </Popover>
+  )
+}

apps/desktop/src/i18n/en.ts

@@ -538,6 +538,8 @@ export const en: Translations = {
       builtinOnly: 'Built-in only',
       notSet: 'Not set',
       commaSeparated: 'comma-separated values',
+      searchPlaceholder: 'Search…',
+      noResults: 'No results found',
       loading: 'Loading Hermes configuration...',
       emptyTitle: 'Nothing to configure',
       emptyDesc: 'This section has no adjustable settings.',

apps/desktop/src/i18n/types.ts

@@ -445,6 +445,8 @@ export interface Translations {
       builtinOnly: string
       notSet: string
       commaSeparated: string
+      searchPlaceholder: string
+      noResults: string
       loading: string
       emptyTitle: string
       emptyDesc: string

apps/desktop/src/i18n/zh.ts

@@ -748,6 +748,8 @@ export const zh: Translations = {
       builtinOnly: '仅内置',
       notSet: '未设置',
       commaSeparated: '逗号分隔的值',
+      searchPlaceholder: '搜索…',
+      noResults: '未找到结果',
       loading: '正在加载 Hermes 配置...',
       emptyTitle: '无可配置项',
       emptyDesc: '此分区没有可调整的设置。',

apps/desktop/src/types/hermes.ts

@@ -2,6 +2,9 @@ export interface ConfigFieldSchema {
   category?: string
   description?: string
   options?: unknown[]
+  /** When true, renders a SearchableSelect (Popover + cmdk) instead of the
+   *  closed `<Select>` dropdown. For large option lists like IANA timezones. */
+  searchable?: boolean
   type?: 'boolean' | 'list' | 'number' | 'select' | 'string' | 'text'
 }
 

hermes_cli/web_server.py

@@ -799,7 +799,22 @@ def _memory_provider_options() -> List[str]:
     return list(dict.fromkeys(options))
 
 
+def _timezone_options() -> List[str]:
+    """Return sorted IANA timezone identifiers, cached at import time."""
+    try:
+        import zoneinfo
+        return sorted(zoneinfo.available_timezones())
+    except Exception:  # pragma: no cover
+        return ["UTC"]
+
+
 _SCHEMA_OVERRIDES: Dict[str, Dict[str, Any]] = {
+    "timezone": {
+        "type": "select",
+        "description": "IANA timezone (e.g. America/New_York). Blank uses the system timezone.",
+        "options": _timezone_options(),
+        "searchable": True,
+    },
     "memory.provider": {
         "type": "select",
         "description": "Memory provider plugin",