diff --git a/docs/apps.md b/docs/apps.md
index 18205e8..5bf3981 100644
--- a/docs/apps.md
+++ b/docs/apps.md
@@ -89,7 +89,7 @@ export default function ExampleApp({ setTitle }: AppProps) {
 }
 ```
 
-## The ten apps
+## The eleven apps
 
 | App | `id` | Params | Notes |
 |---|---|---|---|
@@ -100,10 +100,22 @@ export default function ExampleApp({ setTitle }: AppProps) {
 | Bookmarks | `bookmarks` | — | NIP-51 kind 10003 list — bookmarked notes and articles |
 | Web Bookmarks | `web-bookmarks` | — | NIP-B0 kind 39701 — one addressable event per saved URL |
 | Live | `live` | `pubkey?`, `identifier?` | NIP-53 kind 30311 live events + kind 1311 chat |
+| Spells | `spells` | `id?` | Saved/shareable REQ filters — kind 777, a third-party draft NIP |
 | Relays | `relays` | — | Connection state, subscription count, measured latency |
 | Settings | `settings` | — | Theme, relay list, Blossom servers, account, session |
 | About | `about` | — | What this is, the app list, the shortcuts |
 
+### Spells are a third-party kind, adopted for interop
+
+Kind `777` ("Spell") isn't in the official nostr-protocol/nips registry — it comes from
+[Grimoire](https://github.com/purrgrammer/grimoire), a third-party Nostr client that also
+happens to be a tiling-window-manager OS like this one. `src/hooks/useSpells.ts` implements
+its draft NIP as-is (same tag names, same `$me`/`$contacts` runtime variables, same relative
+timestamp grammar) rather than inventing an incompatible shape, so a spell saved here is
+readable by Grimoire and vice versa. Only the "Spell" half (kind `777`, a saved query) is
+implemented; "Spellbook" (kind `30777`, a saved window layout) is not — see the app's
+tracking issue for that as a possible follow-up.
+
 ### Live only links out to playback, it doesn't embed a player
 
 NIP-53's `streaming` tag is typically an HLS (`.m3u8`) URL, which no browser plays natively
diff --git a/src/apps/spells/NewSpellForm.tsx b/src/apps/spells/NewSpellForm.tsx
new file mode 100644
index 0000000..19fba53
--- /dev/null
+++ b/src/apps/spells/NewSpellForm.tsx
@@ -0,0 +1,235 @@
+import { useId, useState } from 'react';
+import { Loader2 } from 'lucide-react';
+import { Button } from '@/components/ui/button';
+import { Input } from '@/components/ui/input';
+import { Textarea } from '@/components/ui/textarea';
+import { useCurrentUser } from '@/hooks/useCurrentUser';
+import { useCreateSpell, type SpellInput } from '@/hooks/useSpells';
+import { useToast } from '@/hooks/useToast';
+import { cn } from '@/lib/utils';
+
+type AuthorsMode = 'anyone' | 'me' | 'contacts' | 'custom';
+
+export function NewSpellForm({ onDone }: { onDone: () => void }) {
+  const { user } = useCurrentUser();
+  const formId = useId();
+  const [name, setName] = useState('');
+  const [description, setDescription] = useState('');
+  const [kinds, setKinds] = useState('1');
+  const [authorsMode, setAuthorsMode] = useState<AuthorsMode>('anyone');
+  const [customAuthors, setCustomAuthors] = useState('');
+  const [tagLetter, setTagLetter] = useState('');
+  const [tagValues, setTagValues] = useState('');
+  const [since, setSince] = useState('');
+  const [limit, setLimit] = useState('50');
+  const [topics, setTopics] = useState('');
+
+  const create = useCreateSpell();
+  const { toast } = useToast();
+
+  const parsedKinds = kinds
+    .split(',')
+    .map((value) => Number(value.trim()))
+    .filter((value) => Number.isInteger(value) && value >= 0);
+
+  const isValid = parsedKinds.length > 0;
+
+  const submit = async () => {
+    if (!isValid) return;
+
+    const authors: string[] | undefined =
+      authorsMode === 'me'
+        ? ['$me']
+        : authorsMode === 'contacts'
+          ? ['$contacts']
+          : authorsMode === 'custom'
+            ? customAuthors
+                .split(',')
+                .map((value) => value.trim())
+                .filter(Boolean)
+            : undefined;
+
+    const input: SpellInput = {
+      name: name.trim() || undefined,
+      description: description.trim() || undefined,
+      kinds: parsedKinds,
+      authors,
+      tagFilter:
+        tagLetter.trim() && tagValues.trim()
+          ? {
+              letter: tagLetter.trim().slice(0, 1),
+              values: tagValues
+                .split(',')
+                .map((value) => value.trim())
+                .filter(Boolean),
+            }
+          : undefined,
+      limit: limit.trim() ? Number(limit.trim()) : undefined,
+      since: since.trim() || undefined,
+      topics: topics
+        .split(',')
+        .map((value) => value.trim())
+        .filter(Boolean),
+    };
+
+    try {
+      await create.mutateAsync(input);
+      toast({ title: 'Spell saved' });
+      onDone();
+    } catch (error) {
+      toast({
+        title: 'Could not save spell',
+        description: error instanceof Error ? error.message : 'No relay accepted it.',
+        variant: 'destructive',
+      });
+    }
+  };
+
+  if (!user) {
+    return (
+      <div className="p-5">
+        <p className="text-sm text-muted-foreground">Sign in to save a spell.</p>
+      </div>
+    );
+  }
+
+  return (
+    <div className="space-y-4 p-5">
+      <div>
+        <h2 className="text-lg font-semibold">New spell</h2>
+        <p className="mt-1 text-sm text-muted-foreground">
+          A spell is a saved Nostr query — kinds, authors, a tag filter and a time window —
+          that you can re-run, share, or come back to later.
+        </p>
+      </div>
+
+      <Field id={`${formId}-name`} label="Name (optional)">
+        <Input
+          id={`${formId}-name`}
+          value={name}
+          onChange={(event) => setName(event.target.value)}
+          placeholder="Bitcoin from contacts"
+        />
+      </Field>
+
+      <Field id={`${formId}-description`} label="Description (optional)">
+        <Textarea
+          id={`${formId}-description`}
+          value={description}
+          onChange={(event) => setDescription(event.target.value)}
+          rows={2}
+          className="min-h-14 resize-none text-[14px]"
+        />
+      </Field>
+
+      <Field id={`${formId}-kinds`} label="Kinds (comma separated)">
+        <Input
+          id={`${formId}-kinds`}
+          value={kinds}
+          onChange={(event) => setKinds(event.target.value)}
+          placeholder="1, 30023"
+        />
+      </Field>
+
+      <fieldset className="space-y-1.5">
+        <legend className="text-xs font-medium text-muted-foreground">Authors</legend>
+        <div className="flex flex-wrap gap-1.5">
+          {(
+            [
+              ['anyone', 'Anyone'],
+              ['me', 'Me'],
+              ['contacts', 'My contacts'],
+              ['custom', 'Custom'],
+            ] as const
+          ).map(([mode, label]) => (
+            <button
+              key={mode}
+              type="button"
+              onClick={() => setAuthorsMode(mode)}
+              aria-pressed={authorsMode === mode}
+              className={cn(
+                'rounded-full px-3 py-1 text-xs font-medium transition-colors',
+                authorsMode === mode ? 'bg-primary text-primary-foreground' : 'bg-muted text-muted-foreground hover:bg-muted/70',
+              )}
+            >
+              {label}
+            </button>
+          ))}
+        </div>
+        {authorsMode === 'custom' && (
+          <Input
+            value={customAuthors}
+            onChange={(event) => setCustomAuthors(event.target.value)}
+            placeholder="hex pubkeys, comma separated"
+            aria-label="Custom author pubkeys, comma separated"
+            className="mt-2"
+          />
+        )}
+      </fieldset>
+
+      <div className="grid grid-cols-2 gap-3">
+        <Field id={`${formId}-tag-letter`} label="Tag filter letter">
+          <Input
+            id={`${formId}-tag-letter`}
+            value={tagLetter}
+            onChange={(event) => setTagLetter(event.target.value)}
+            placeholder="t"
+            maxLength={1}
+          />
+        </Field>
+        <Field id={`${formId}-tag-values`} label="Tag values">
+          <Input
+            id={`${formId}-tag-values`}
+            value={tagValues}
+            onChange={(event) => setTagValues(event.target.value)}
+            placeholder="bitcoin, nostr"
+          />
+        </Field>
+      </div>
+
+      <div className="grid grid-cols-2 gap-3">
+        <Field id={`${formId}-since`} label="Since (e.g. 7d, now, or blank)">
+          <Input id={`${formId}-since`} value={since} onChange={(event) => setSince(event.target.value)} placeholder="7d" />
+        </Field>
+        <Field id={`${formId}-limit`} label="Limit">
+          <Input
+            id={`${formId}-limit`}
+            value={limit}
+            onChange={(event) => setLimit(event.target.value)}
+            inputMode="numeric"
+          />
+        </Field>
+      </div>
+
+      <Field id={`${formId}-topics`} label="Topics (comma separated, for discovery)">
+        <Input
+          id={`${formId}-topics`}
+          value={topics}
+          onChange={(event) => setTopics(event.target.value)}
+          placeholder="bitcoin, social"
+        />
+      </Field>
+
+      <div className="flex justify-end gap-2 pt-2">
+        <Button variant="ghost" size="sm" onClick={onDone}>
+          Cancel
+        </Button>
+        <Button size="sm" onClick={submit} disabled={!isValid || create.isPending} className="gap-1.5">
+          {create.isPending && <Loader2 className="size-3.5 animate-spin" aria-hidden />}
+          Save spell
+        </Button>
+      </div>
+    </div>
+  );
+}
+
+function Field({ id, label, children }: { id: string; label: string; children: React.ReactNode }) {
+  return (
+    <div className="space-y-1.5">
+      <label htmlFor={id} className="block text-xs font-medium text-muted-foreground">
+        {label}
+      </label>
+      {children}
+    </div>
+  );
+}
diff --git a/src/apps/spells/index.tsx b/src/apps/spells/index.tsx
new file mode 100644
index 0000000..9db9249
--- /dev/null
+++ b/src/apps/spells/index.tsx
@@ -0,0 +1,380 @@
+import { useEffect, useMemo, useState } from 'react';
+import type { NostrEvent } from '@nostrify/nostrify';
+import { ChevronLeft, Globe, Loader2, Plus, Sparkles, User as UserIcon } from 'lucide-react';
+import {
+  AppBody,
+  AppLayout,
+  AppSectionTitle,
+  AppSidebar,
+  AppSplit,
+  AppToolbar,
+  EmptyState,
+} from '@/components/os/AppChrome';
+import { AuthorLine } from '@/components/nostr/AuthorLine';
+import { NoteCard } from '@/components/nostr/NoteCard';
+import { Badge } from '@/components/ui/badge';
+import { Button } from '@/components/ui/button';
+import { Skeleton } from '@/components/ui/skeleton';
+import { useCurrentUser } from '@/hooks/useCurrentUser';
+import { useIsMobile } from '@/hooks/useIsMobile';
+import {
+  isValidTagLetter,
+  parseSpell,
+  resolveSpellFilter,
+  useDiscoverSpells,
+  useMySpells,
+  useRunSpell,
+  useSpellContext,
+} from '@/hooks/useSpells';
+import { relativeTime } from '@/lib/nostrUtils';
+import { cn } from '@/lib/utils';
+import { NewSpellForm } from './NewSpellForm';
+import type { AppProps } from '@/os/types';
+
+type Scope = 'mine' | 'discover';
+
+export default function SpellsApp({ params, setTitle, setParams }: AppProps) {
+  const { user } = useCurrentUser();
+  const isMobile = useIsMobile();
+  const [requestedScope, setRequestedScope] = useState<Scope>('mine');
+  const [formOpen, setFormOpen] = useState(false);
+
+  // Signing out mid-session must not leave "My Spells" showing the previous
+  // user's (still-cached) spells — same reasoning as the Feed app's scope.
+  const scope: Scope = user ? requestedScope : 'discover';
+
+  const mine = useMySpells();
+  const discover = useDiscoverSpells();
+  const query = scope === 'mine' ? mine : discover;
+
+  const selectedId = params.id;
+  const selected = query.data?.find((event) => event.id === selectedId);
+
+  useEffect(() => setTitle('Spells'), [setTitle]);
+
+  const select = (id: string | null) => setParams(id ? { id } : {});
+
+  const listPane = (
+    <SpellList
+      query={query}
+      scope={scope}
+      selectedId={selectedId}
+      onSelect={(event) => select(event.id)}
+    />
+  );
+
+  const detailPane = formOpen ? (
+    <NewSpellForm onDone={() => setFormOpen(false)} />
+  ) : selected ? (
+    <SpellDetail event={selected} />
+  ) : (
+    <EmptyState
+      title="Pick a spell"
+      hint="Choose a saved query from the list, or cast a new one."
+      action={
+        <Button size="sm" onClick={() => setFormOpen(true)} className="gap-1.5">
+          <Sparkles className="size-3.5" aria-hidden />
+          New spell
+        </Button>
+      }
+    />
+  );
+
+  const toolbarTabs = (
+    <>
+      <ScopeTab
+        active={scope === 'mine'}
+        disabled={!user}
+        onClick={() => setRequestedScope('mine')}
+        icon={<UserIcon className="size-3.5" aria-hidden />}
+        label="My Spells"
+      />
+      <ScopeTab
+        active={scope === 'discover'}
+        onClick={() => setRequestedScope('discover')}
+        icon={<Globe className="size-3.5" aria-hidden />}
+        label="Discover"
+      />
+    </>
+  );
+
+  if (isMobile) {
+    const showingDetail = formOpen || Boolean(selected);
+    return (
+      <AppLayout>
+        <AppToolbar className="gap-1">
+          {showingDetail ? (
+            <button
+              type="button"
+              onClick={() => {
+                setFormOpen(false);
+                select(null);
+              }}
+              className="-ml-1 flex items-center gap-1 rounded px-1 py-0.5 text-[13px] font-medium focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-ring"
+            >
+              <ChevronLeft className="size-4" aria-hidden />
+              Spells
+            </button>
+          ) : (
+            toolbarTabs
+          )}
+          {!showingDetail && (
+            <Button
+              variant="ghost"
+              size="sm"
+              className="ml-auto h-7 gap-1.5 px-2 text-xs"
+              onClick={() => setFormOpen(true)}
+            >
+              <Plus className="size-3.5" aria-hidden />
+              New
+            </Button>
+          )}
+        </AppToolbar>
+        <AppBody>{showingDetail ? detailPane : listPane}</AppBody>
+      </AppLayout>
+    );
+  }
+
+  return (
+    <AppLayout>
+      <AppToolbar className="gap-1">
+        {toolbarTabs}
+        <Button
+          variant="ghost"
+          size="sm"
+          className="ml-auto h-7 gap-1.5 px-2 text-xs"
+          onClick={() => setFormOpen(true)}
+        >
+          <Plus className="size-3.5" aria-hidden />
+          New spell
+        </Button>
+      </AppToolbar>
+      <AppSplit>
+        <AppSidebar className="p-0">{listPane}</AppSidebar>
+        <AppBody>{detailPane}</AppBody>
+      </AppSplit>
+    </AppLayout>
+  );
+}
+
+function ScopeTab({
+  active,
+  disabled,
+  onClick,
+  icon,
+  label,
+}: {
+  active: boolean;
+  disabled?: boolean;
+  onClick: () => void;
+  icon: React.ReactNode;
+  label: string;
+}) {
+  return (
+    <button
+      type="button"
+      onClick={onClick}
+      disabled={disabled}
+      aria-pressed={active}
+      className={cn(
+        'flex items-center gap-1.5 rounded-md px-2.5 py-1 text-[13px] font-medium transition-colors',
+        'focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-ring',
+        'disabled:cursor-not-allowed disabled:opacity-40',
+        active ? 'bg-secondary text-foreground' : 'text-muted-foreground hover:bg-muted',
+      )}
+    >
+      {icon}
+      {label}
+    </button>
+  );
+}
+
+function SpellList({
+  query,
+  scope,
+  selectedId,
+  onSelect,
+}: {
+  query: { isLoading: boolean; data: NostrEvent[] | undefined };
+  scope: Scope;
+  selectedId: string | undefined;
+  onSelect: (event: NostrEvent) => void;
+}) {
+  if (query.isLoading) {
+    return (
+      <div className="space-y-3 p-3">
+        {Array.from({ length: 5 }).map((_, index) => (
+          <Skeleton key={index} className="h-10 w-full" />
+        ))}
+      </div>
+    );
+  }
+
+  if (!query.data || query.data.length === 0) {
+    return (
+      <p className="px-3 py-6 text-center text-xs text-muted-foreground">
+        {scope === 'mine' ? 'You haven’t saved any spells yet.' : 'No spells found on your relays.'}
+      </p>
+    );
+  }
+
+  return (
+    <>
+      <AppSectionTitle>{scope === 'mine' ? 'My Spells' : 'Discover'}</AppSectionTitle>
+      <ul className="pb-2">
+        {query.data.map((event) => (
+          <li key={event.id}>
+            <SpellListItem event={event} active={event.id === selectedId} onSelect={() => onSelect(event)} />
+          </li>
+        ))}
+      </ul>
+    </>
+  );
+}
+
+function SpellListItem({
+  event,
+  active,
+  onSelect,
+}: {
+  event: NostrEvent;
+  active: boolean;
+  onSelect: () => void;
+}) {
+  const spell = useMemo(() => parseSpell(event), [event]);
+  const label = spell.name || spell.description || `${spell.kinds.join(', ') || 'empty'} query`;
+
+  return (
+    <button
+      type="button"
+      onClick={onSelect}
+      className={cn(
+        'w-full px-3 py-2 text-left transition-colors',
+        'focus-visible:outline-2 focus-visible:-outline-offset-2 focus-visible:outline-ring',
+        active ? 'bg-accent text-accent-foreground' : 'hover:bg-muted',
+      )}
+    >
+      <span className="line-clamp-1 block text-[13px] font-medium leading-snug">{label}</span>
+      <span className="mt-0.5 block truncate text-[11px] text-muted-foreground">
+        kinds {spell.kinds.join(', ') || '—'} · {relativeTime(event.created_at)}
+      </span>
+    </button>
+  );
+}
+
+function SpellDetail({ event }: { event: NostrEvent }) {
+  const spell = useMemo(() => parseSpell(event), [event]);
+  const context = useSpellContext();
+  const filter = useMemo(() => resolveSpellFilter(spell, context), [spell, context]);
+  const run = useRunSpell(filter);
+
+  return (
+    <div className="p-5">
+      <div className="mb-4 flex items-start justify-between gap-3">
+        <div>
+          <h1 className="text-lg font-semibold leading-tight">
+            {spell.name || spell.description || 'Untitled spell'}
+          </h1>
+          {spell.name && spell.description && (
+            <p className="mt-1 text-sm text-muted-foreground">{spell.description}</p>
+          )}
+        </div>
+        <Button size="sm" onClick={() => run.mutate()} disabled={!filter || run.isPending} className="shrink-0 gap-1.5">
+          {run.isPending && <Loader2 className="size-3.5 animate-spin" aria-hidden />}
+          Run
+        </Button>
+      </div>
+
+      <AuthorLine pubkey={event.pubkey} createdAt={event.created_at} size="sm" />
+
+      <div className="mt-3 flex flex-wrap items-center gap-1.5">
+        {spell.kinds.map((kind) => (
+          <Badge key={kind} variant="secondary" className="text-[11px]">
+            kind {kind}
+          </Badge>
+        ))}
+        {spell.authors.length > 0 && (
+          <Badge variant="outline" className="text-[11px]">
+            authors: {spell.authors.join(', ')}
+          </Badge>
+        )}
+        {spell.tagFilter && isValidTagLetter(spell.tagFilter.letter) && spell.tagFilter.values.length > 0 && (
+          <Badge variant="outline" className="text-[11px]">
+            #{spell.tagFilter.letter}: {spell.tagFilter.values.join(', ')}
+          </Badge>
+        )}
+        {spell.since && (
+          <Badge variant="outline" className="text-[11px]">
+            since {spell.since}
+          </Badge>
+        )}
+        {spell.topics.map((topic) => (
+          <Badge key={topic} variant="outline" className="text-[11px]">
+            {topic}
+          </Badge>
+        ))}
+      </div>
+
+      {!filter && (
+        <p className="mt-4 text-xs text-muted-foreground">
+          {spell.authors.includes('$me') && !context.me
+            ? 'This spell needs $me — sign in to run it.'
+            : 'This spell has no runnable filter.'}
+        </p>
+      )}
+
+      <div className="mt-6">
+        {run.isPending ? (
+          <div className="space-y-3">
+            {Array.from({ length: 3 }).map((_, index) => (
+              <Skeleton key={index} className="h-12 w-full" />
+            ))}
+          </div>
+        ) : run.isError ? (
+          <p className="text-sm text-destructive">
+            {run.error instanceof Error ? run.error.message : 'The query failed.'}
+          </p>
+        ) : run.isSuccess ? (
+          <SpellResults events={run.data} />
+        ) : null}
+      </div>
+    </div>
+  );
+}
+
+function SpellResults({ events }: { events: NostrEvent[] }) {
+  if (events.length === 0) {
+    return <p className="text-sm text-muted-foreground">No events matched.</p>;
+  }
+
+  return (
+    <div className="-mx-5 border-t border-border">
+      <p className="px-5 py-2 text-xs text-muted-foreground">
+        {events.length} {events.length === 1 ? 'result' : 'results'}
+      </p>
+      {events.map((event) =>
+        event.kind === 1 ? (
+          <NoteCard key={event.id} event={event} compact />
+        ) : (
+          <GenericResultRow key={event.id} event={event} />
+        ),
+      )}
+    </div>
+  );
+}
+
+function GenericResultRow({ event }: { event: NostrEvent }) {
+  return (
+    <div className="border-b border-border px-5 py-3 last:border-b-0">
+      <div className="flex items-center justify-between gap-2">
+        <AuthorLine pubkey={event.pubkey} createdAt={event.created_at} size="sm" />
+        <Badge variant="secondary" className="shrink-0 text-[11px]">
+          kind {event.kind}
+        </Badge>
+      </div>
+      {event.content && (
+        <p className="mt-1.5 line-clamp-3 text-[13px] text-muted-foreground">{event.content}</p>
+      )}
+    </div>
+  );
+}
diff --git a/src/hooks/useSpells.test.ts b/src/hooks/useSpells.test.ts
new file mode 100644
index 0000000..638f2d8
--- /dev/null
+++ b/src/hooks/useSpells.test.ts
@@ -0,0 +1,175 @@
+import { describe, expect, it } from 'vitest';
+import type { NostrEvent } from '@nostrify/nostrify';
+import {
+  encodeSpellTags,
+  isValidTagLetter,
+  parseSpell,
+  resolveSpellFilter,
+  resolveTimestamp,
+  type ParsedSpell,
+} from './useSpells';
+
+function spellEvent(tags: string[][], content = ''): NostrEvent {
+  return { id: 'x', pubkey: 'author', created_at: 0, kind: 777, tags, content, sig: '' };
+}
+
+/** A ParsedSpell as if it came straight off a relay — encodeSpellTags always produces well-formed data, so malformed cases are built by hand. */
+function parsedSpell(overrides: Partial<ParsedSpell>): ParsedSpell {
+  return {
+    description: '',
+    kinds: [1],
+    authors: [],
+    topics: [],
+    event: spellEvent([]),
+    ...overrides,
+  };
+}
+
+describe('resolveTimestamp', () => {
+  it('resolves a relative duration against now', () => {
+    const before = Math.floor(Date.now() / 1000) - 7 * 86400;
+    const result = resolveTimestamp('7d');
+    const after = Math.floor(Date.now() / 1000) - 7 * 86400;
+    // A range, not toBeCloseTo against a single captured `now` — a slow test
+    // runner or wall-clock skew between the two Date.now() calls could
+    // otherwise make this flaky.
+    expect(result).toBeGreaterThanOrEqual(before);
+    expect(result).toBeLessThanOrEqual(after);
+  });
+
+  it('resolves "now"', () => {
+    const before = Math.floor(Date.now() / 1000);
+    const result = resolveTimestamp('now');
+    const after = Math.floor(Date.now() / 1000);
+    expect(result).toBeGreaterThanOrEqual(before);
+    expect(result).toBeLessThanOrEqual(after);
+  });
+
+  it('resolves an absolute unix timestamp', () => {
+    expect(resolveTimestamp('1700000000')).toBe(1700000000);
+  });
+
+  it('is undefined for blank input', () => {
+    expect(resolveTimestamp('')).toBeUndefined();
+    expect(resolveTimestamp('   ')).toBeUndefined();
+  });
+});
+
+describe('encodeSpellTags / parseSpell round-trip', () => {
+  it('round-trips a spell with authors, a tag filter, since and topics', () => {
+    const tags = encodeSpellTags({
+      name: 'Bitcoin from contacts',
+      description: 'Notes about Bitcoin from my contacts',
+      kinds: [1],
+      authors: ['$contacts'],
+      tagFilter: { letter: 't', values: ['bitcoin'] },
+      since: '7d',
+      limit: 50,
+      topics: ['bitcoin', 'social'],
+    });
+    const event = spellEvent(tags, 'Notes about Bitcoin from my contacts');
+    const parsed = parseSpell(event);
+
+    expect(parsed.name).toBe('Bitcoin from contacts');
+    expect(parsed.kinds).toEqual([1]);
+    expect(parsed.authors).toEqual(['$contacts']);
+    expect(parsed.tagFilter).toEqual({ letter: 't', values: ['bitcoin'] });
+    expect(parsed.since).toBe('7d');
+    expect(parsed.limit).toBe(50);
+    expect(parsed.topics).toEqual(['bitcoin', 'social']);
+  });
+
+  it('drops an invalid tag-filter letter instead of publishing a spell that can never run', () => {
+    const tags = encodeSpellTags({ kinds: [1], tagFilter: { letter: '', values: ['x'] } });
+    expect(tags.some(([name]) => name === 'tag')).toBe(false);
+  });
+
+  it('drops a non-positive or non-integer limit instead of publishing one resolveSpellFilter will ignore', () => {
+    expect(encodeSpellTags({ kinds: [1], limit: 0 }).some(([name]) => name === 'limit')).toBe(false);
+    expect(encodeSpellTags({ kinds: [1], limit: -5 }).some(([name]) => name === 'limit')).toBe(false);
+    expect(encodeSpellTags({ kinds: [1], limit: 1.5 }).some(([name]) => name === 'limit')).toBe(false);
+  });
+
+  it('keeps a valid limit and tag filter', () => {
+    const tags = encodeSpellTags({ kinds: [1], limit: 50, tagFilter: { letter: 't', values: ['x'] } });
+    expect(tags).toContainEqual(['limit', '50']);
+    expect(tags).toContainEqual(['tag', 't', 'x']);
+  });
+});
+
+describe('parseSpell', () => {
+  it('drops non-integer and negative k tags — kinds are non-negative integers', () => {
+    const event = spellEvent([
+      ['cmd', 'REQ'],
+      ['k', '1'],
+      ['k', '1.5'],
+      ['k', '-1'],
+      ['k', 'not-a-number'],
+    ]);
+    expect(parseSpell(event).kinds).toEqual([1]);
+  });
+});
+
+describe('isValidTagLetter', () => {
+  it('accepts a single letter', () => {
+    expect(isValidTagLetter('t')).toBe(true);
+    expect(isValidTagLetter('P')).toBe(true);
+  });
+
+  it('rejects empty, multi-character, and non-letter values', () => {
+    expect(isValidTagLetter('')).toBe(false);
+    expect(isValidTagLetter('tt')).toBe(false);
+    expect(isValidTagLetter('1')).toBe(false);
+  });
+});
+
+describe('resolveSpellFilter', () => {
+  it('resolves $me and $contacts into real pubkeys', () => {
+    const event = spellEvent(encodeSpellTags({ kinds: [1], authors: ['$me', '$contacts'] }));
+    const filter = resolveSpellFilter(parseSpell(event), { me: 'abc', contacts: ['def', 'ghi'] });
+    expect(filter?.authors).toEqual(['abc', 'def', 'ghi']);
+  });
+
+  it('returns null when $me is required but nobody is signed in', () => {
+    const event = spellEvent(encodeSpellTags({ kinds: [1], authors: ['$me'] }));
+    const filter = resolveSpellFilter(parseSpell(event), { me: undefined, contacts: [] });
+    expect(filter).toBeNull();
+  });
+
+  it('returns null when there are no kinds', () => {
+    const event = spellEvent(encodeSpellTags({ kinds: [] }));
+    const filter = resolveSpellFilter(parseSpell(event), { me: undefined, contacts: [] });
+    expect(filter).toBeNull();
+  });
+
+  it('turns a tag filter into a #<letter> filter field', () => {
+    const event = spellEvent(
+      encodeSpellTags({ kinds: [1], tagFilter: { letter: 't', values: ['bitcoin', 'nostr'] } }),
+    );
+    const filter = resolveSpellFilter(parseSpell(event), { me: undefined, contacts: [] });
+    expect(filter?.['#t']).toEqual(['bitcoin', 'nostr']);
+  });
+
+  it('ignores a malformed (non-single-letter) tag filter instead of producing "#undefined"', () => {
+    const spell = parsedSpell({ tagFilter: { letter: '', values: ['x'] } });
+    const filter = resolveSpellFilter(spell, { me: undefined, contacts: [] });
+    expect(Object.keys(filter ?? {}).some((key) => key.startsWith('#'))).toBe(false);
+  });
+
+  it('clamps an excessive limit to the maximum', () => {
+    const spell = parsedSpell({ limit: 1_000_000 });
+    const filter = resolveSpellFilter(spell, { me: undefined, contacts: [] });
+    expect(filter?.limit).toBe(500);
+  });
+
+  it('drops a zero or NaN limit rather than sending a degenerate query', () => {
+    expect(resolveSpellFilter(parsedSpell({ limit: 0 }), { me: undefined, contacts: [] })?.limit).toBeUndefined();
+    expect(resolveSpellFilter(parsedSpell({ limit: NaN }), { me: undefined, contacts: [] })?.limit).toBeUndefined();
+  });
+
+  it('keeps a normal, in-range limit as-is', () => {
+    const spell = parsedSpell({ limit: 50 });
+    const filter = resolveSpellFilter(spell, { me: undefined, contacts: [] });
+    expect(filter?.limit).toBe(50);
+  });
+});
diff --git a/src/hooks/useSpells.ts b/src/hooks/useSpells.ts
new file mode 100644
index 0000000..90d54e8
--- /dev/null
+++ b/src/hooks/useSpells.ts
@@ -0,0 +1,243 @@
+import { useNostr } from '@nostrify/react';
+import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
+import type { NostrEvent, NostrFilter } from '@nostrify/nostrify';
+import { useCurrentUser } from './useCurrentUser';
+import { useMyFollows } from './useFollows';
+import { useNostrPublish } from './useNostrPublish';
+import { tagValue, tagValues } from '@/lib/nostrUtils';
+
+/**
+ * A third-party draft NIP (not in the official nostr-protocol/nips registry)
+ * from the Grimoire client (github.com/purrgrammer/grimoire): kind 777
+ * "Spell" events encode a REQ filter as portable, shareable tags, with
+ * `$me`/`$contacts` runtime variables and relative timestamps ("7d", "now").
+ * Kind numbers are adopted as-is for interop with that client.
+ */
+export const SPELL_KIND = 777;
+
+const RELATIVE_TIME_RE = /^(\d+)(s|m|h|d|w|mo|y)$/;
+const UNIT_SECONDS: Record<string, number> = {
+  s: 1,
+  m: 60,
+  h: 3600,
+  d: 86400,
+  w: 604800,
+  mo: 2_592_000,
+  y: 31_536_000,
+};
+
+/** A single NIP-01 tag-filter letter, e.g. the `t` in `#t`. */
+const TAG_LETTER_RE = /^[a-zA-Z]$/;
+/** Caps a relay-sourced spell's `limit` so Run can't be tricked into a huge query. */
+const MAX_SPELL_LIMIT = 500;
+
+/** A valid NIP-01 tag-filter letter — the only kind `resolveSpellFilter` will act on. */
+export function isValidTagLetter(letter: string): boolean {
+  return TAG_LETTER_RE.test(letter);
+}
+
+/** Resolves `now`, `<n><unit>` (e.g. `7d`) or a literal unix timestamp string. */
+export function resolveTimestamp(value: string): number | undefined {
+  const trimmed = value.trim();
+  if (!trimmed) return undefined;
+  if (trimmed === 'now') return Math.floor(Date.now() / 1000);
+  const relative = RELATIVE_TIME_RE.exec(trimmed);
+  if (relative) {
+    const [, amount, unit] = relative;
+    return Math.floor(Date.now() / 1000) - Number(amount) * UNIT_SECONDS[unit];
+  }
+  const absolute = Number(trimmed);
+  return Number.isFinite(absolute) && absolute > 0 ? Math.floor(absolute) : undefined;
+}
+
+export interface SpellInput {
+  name?: string;
+  description?: string;
+  kinds: number[];
+  /** `$me`, `$contacts`, or a literal list of pubkeys (hex). */
+  authors?: string[];
+  /** A single `#<letter>` tag filter, e.g. `{ letter: 't', values: ['bitcoin'] }`. */
+  tagFilter?: { letter: string; values: string[] };
+  limit?: number;
+  since?: string;
+  until?: string;
+  search?: string;
+  topics?: string[];
+}
+
+export interface ParsedSpell {
+  name?: string;
+  description: string;
+  kinds: number[];
+  authors: string[];
+  tagFilter?: { letter: string; values: string[] };
+  limit?: number;
+  since?: string;
+  until?: string;
+  search?: string;
+  topics: string[];
+  event: NostrEvent;
+}
+
+/**
+ * Builds the tag set for a spell event per the draft NIP. Validates the tag
+ * filter's letter and the limit before writing them — an invalid `letter`
+ * or a non-positive/non-integer `limit` is dropped rather than published,
+ * since `resolveSpellFilter` would silently ignore it on Run anyway and a
+ * saved-but-inert filter is worse than one that never made it into the
+ * event at all.
+ */
+export function encodeSpellTags(input: SpellInput): string[][] {
+  const tags: string[][] = [['cmd', 'REQ']];
+  for (const kind of input.kinds) tags.push(['k', String(kind)]);
+  if (input.authors?.length) tags.push(['authors', ...input.authors]);
+  if (input.tagFilter?.values.length && isValidTagLetter(input.tagFilter.letter)) {
+    tags.push(['tag', input.tagFilter.letter, ...input.tagFilter.values]);
+  }
+  if (input.limit !== undefined && Number.isInteger(input.limit) && input.limit > 0) {
+    tags.push(['limit', String(input.limit)]);
+  }
+  if (input.since?.trim()) tags.push(['since', input.since.trim()]);
+  if (input.until?.trim()) tags.push(['until', input.until.trim()]);
+  if (input.search?.trim()) tags.push(['search', input.search.trim()]);
+  if (input.name?.trim()) tags.push(['name', input.name.trim()]);
+  tags.push(['alt', `Spell: ${input.description || input.name || 'a saved Nostr query'}`]);
+  for (const topic of input.topics ?? []) if (topic.trim()) tags.push(['t', topic.trim()]);
+  return tags;
+}
+
+export function parseSpell(event: NostrEvent): ParsedSpell {
+  // Nostr kinds are non-negative integers — a relay-sourced spell claiming
+  // e.g. "1.5" or "-1" would otherwise pass through into a malformed filter.
+  const kinds = tagValues(event, 'k')
+    .map(Number)
+    .filter((n) => Number.isInteger(n) && n >= 0);
+  const authorsTag = event.tags.find(([name]) => name === 'authors');
+  const tagFilterTag = event.tags.find(([name]) => name === 'tag');
+  const limitValue = tagValue(event, 'limit');
+
+  return {
+    name: tagValue(event, 'name'),
+    description: event.content,
+    kinds,
+    authors: authorsTag ? authorsTag.slice(1) : [],
+    tagFilter: tagFilterTag ? { letter: tagFilterTag[1], values: tagFilterTag.slice(2) } : undefined,
+    limit: limitValue ? Number(limitValue) : undefined,
+    since: tagValue(event, 'since'),
+    until: tagValue(event, 'until'),
+    search: tagValue(event, 'search'),
+    topics: tagValues(event, 't'),
+    event,
+  };
+}
+
+/** Resolves a parsed spell's `$me`/`$contacts` and relative timestamps into a real filter. */
+export function resolveSpellFilter(
+  spell: ParsedSpell,
+  context: { me: string | undefined; contacts: string[] },
+): NostrFilter | null {
+  if (spell.kinds.length === 0) return null;
+
+  const filter: NostrFilter = { kinds: spell.kinds };
+
+  if (spell.authors.length > 0) {
+    const resolved = spell.authors.flatMap((author) => {
+      if (author === '$me') return context.me ? [context.me] : [];
+      if (author === '$contacts') return context.contacts;
+      return [author];
+    });
+    if (resolved.length === 0) return null;
+    filter.authors = resolved;
+  }
+
+  // Relay-provided events are untrusted: a malformed spell must not produce
+  // a filter key like "#undefined", or a limit that is 0/NaN/huge enough to
+  // lock up the UI on Run.
+  if (spell.tagFilter && isValidTagLetter(spell.tagFilter.letter) && spell.tagFilter.values.length > 0) {
+    filter[`#${spell.tagFilter.letter}`] = spell.tagFilter.values;
+  }
+
+  if (spell.limit !== undefined && Number.isFinite(spell.limit) && spell.limit > 0) {
+    filter.limit = Math.min(spell.limit, MAX_SPELL_LIMIT);
+  }
+  if (spell.since) {
+    const since = resolveTimestamp(spell.since);
+    if (since !== undefined) filter.since = since;
+  }
+  if (spell.until) {
+    const until = resolveTimestamp(spell.until);
+    if (until !== undefined) filter.until = until;
+  }
+  if (spell.search) filter.search = spell.search;
+
+  return filter;
+}
+
+/** `$me`/`$contacts` for the signed-in user, ready to hand to `resolveSpellFilter`. */
+export function useSpellContext() {
+  const { user } = useCurrentUser();
+  const { data: contacts } = useMyFollows();
+  return { me: user?.pubkey, contacts: contacts ?? [] };
+}
+
+export function useMySpells() {
+  const { nostr } = useNostr();
+  const { user } = useCurrentUser();
+
+  return useQuery<NostrEvent[]>({
+    queryKey: ['nostr', 'spells', 'mine', user?.pubkey ?? ''],
+    enabled: Boolean(user),
+    queryFn: async ({ signal }) => {
+      const events = await nostr.query(
+        [{ kinds: [SPELL_KIND], authors: [user!.pubkey], limit: 100 }],
+        { signal: AbortSignal.any([signal, AbortSignal.timeout(6000)]) },
+      );
+      return events.sort((a, b) => b.created_at - a.created_at);
+    },
+    staleTime: 30_000,
+  });
+}
+
+export function useDiscoverSpells() {
+  const { nostr } = useNostr();
+
+  return useQuery<NostrEvent[]>({
+    queryKey: ['nostr', 'spells', 'discover'],
+    queryFn: async ({ signal }) => {
+      const events = await nostr.query([{ kinds: [SPELL_KIND], limit: 100 }], {
+        signal: AbortSignal.any([signal, AbortSignal.timeout(6000)]),
+      });
+      return events.sort((a, b) => b.created_at - a.created_at);
+    },
+    staleTime: 60_000,
+  });
+}
+
+export function useCreateSpell() {
+  const publish = useNostrPublish();
+  const queryClient = useQueryClient();
+  const { user } = useCurrentUser();
+
+  return useMutation({
+    mutationFn: async (input: SpellInput) => {
+      if (!user) throw new Error('Sign in to save a spell');
+      return publish.mutateAsync({ kind: SPELL_KIND, content: input.description ?? '', tags: encodeSpellTags(input) });
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['nostr', 'spells', 'mine', user?.pubkey ?? ''] });
+      queryClient.invalidateQueries({ queryKey: ['nostr', 'spells', 'discover'] });
+    },
+  });
+}
+
+/** Runs a spell's resolved filter on demand — a spell is a saved query, not a subscription. */
+export function useRunSpell(filter: NostrFilter | null) {
+  const { nostr } = useNostr();
+
+  return useMutation({
+    mutationFn: async () => {
+      if (!filter) throw new Error('This spell has no runnable filter');
+      return nostr.query([filter], { signal: AbortSignal.timeout(8000) });
+    },
+  });
+}
diff --git a/src/os/registry.ts b/src/os/registry.ts
index 5ce1d09..2379edb 100644
--- a/src/os/registry.ts
+++ b/src/os/registry.ts
@@ -1,5 +1,5 @@
 import { lazy } from 'react';
-import { Activity, Bookmark, BookOpen, FileText, Info, Link2, Radio, Rss, Settings, User } from 'lucide-react';
+import { Activity, Bookmark, BookOpen, FileText, Info, Link2, Radio, Rss, Settings, Sparkles, User } from 'lucide-react';
 import type { AppDefinition } from './types';
 
 /**
@@ -79,6 +79,16 @@ export const APPS: AppDefinition[] = [
     defaultSize: { width: 780, height: 720 },
     minSize: { width: 360, height: 320 },
   },
+  {
+    id: 'spells',
+    title: 'Spells',
+    description: 'Saved, shareable Nostr queries you can re-run any time',
+    icon: Sparkles,
+    category: 'tools',
+    component: lazy(() => import('@/apps/spells')),
+    defaultSize: { width: 760, height: 700 },
+    minSize: { width: 380, height: 320 },
+  },
   {
     id: 'relays',
     title: 'Relays',