diff --git a/src/hooks/useSpells.test.ts b/src/hooks/useSpells.test.ts
index 9658772..638f2d8 100644
--- a/src/hooks/useSpells.test.ts
+++ b/src/hooks/useSpells.test.ts
@@ -27,13 +27,22 @@ function parsedSpell(overrides: Partial<ParsedSpell>): ParsedSpell {
 
 describe('resolveTimestamp', () => {
   it('resolves a relative duration against now', () => {
-    const now = Math.floor(Date.now() / 1000);
-    expect(resolveTimestamp('7d')).toBeCloseTo(now - 7 * 86400, -1);
+    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 now = Math.floor(Date.now() / 1000);
-    expect(resolveTimestamp('now')).toBeCloseTo(now, -1);
+    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', () => {
@@ -88,6 +97,19 @@ describe('encodeSpellTags / parseSpell round-trip', () => {
   });
 });
 
+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);
diff --git a/src/hooks/useSpells.ts b/src/hooks/useSpells.ts
index e09a458..90d54e8 100644
--- a/src/hooks/useSpells.ts
+++ b/src/hooks/useSpells.ts
@@ -107,7 +107,11 @@ export function encodeSpellTags(input: SpellInput): string[][] {
 }
 
 export function parseSpell(event: NostrEvent): ParsedSpell {
-  const kinds = tagValues(event, 'k').map(Number).filter((n) => Number.isFinite(n));
+  // 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');