diff --git a/src/main/telemetry/validator-warn-cache.test.ts b/src/main/telemetry/validator-warn-cache.test.ts
new file mode 100644
index 000000000..2bc1cbcd7
--- /dev/null
+++ b/src/main/telemetry/validator-warn-cache.test.ts
@@ -0,0 +1,37 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import {
+  _getValidatorWarnCacheSizeForTests,
+  _resetValidatorWarnCacheForTests,
+  validate
+} from './validator'
+
+describe('telemetry validator warn cache', () => {
+  beforeEach(() => {
+    _resetValidatorWarnCacheForTests()
+    vi.spyOn(console, 'warn').mockImplementation(() => {})
+  })
+
+  afterEach(() => {
+    vi.restoreAllMocks()
+  })
+
+  it('bounds warn rate-limit entries for unique invalid event names', () => {
+    for (let i = 0; i < 300; i++) {
+      validate(`not_a_real_event_${i}` as never, {})
+    }
+
+    expect(_getValidatorWarnCacheSizeForTests()).toBeLessThanOrEqual(256)
+  })
+
+  it('prunes expired warn rate-limit entries', () => {
+    vi.spyOn(Date, 'now').mockReturnValue(0)
+    validate('not_a_real_event' as never, {})
+
+    expect(_getValidatorWarnCacheSizeForTests()).toBe(1)
+
+    vi.spyOn(Date, 'now').mockReturnValue(60_000)
+    validate('another_fake_event' as never, {})
+
+    expect(_getValidatorWarnCacheSizeForTests()).toBe(1)
+  })
+})
diff --git a/src/main/telemetry/validator.ts b/src/main/telemetry/validator.ts
index 253af32e9..7d7785897 100644
--- a/src/main/telemetry/validator.ts
+++ b/src/main/telemetry/validator.ts
@@ -34,15 +34,36 @@ export type ValidationResult<N extends EventName> =
   | { ok: false; reason: string }
 
 const WARN_WINDOW_MS = 60_000
+const WARN_CACHE_MAX_ENTRIES = 256
 const lastWarnAt = new Map<string, number>()
 
+function pruneWarnCache(now: number): void {
+  for (const [key, at] of lastWarnAt) {
+    if (now - at >= WARN_WINDOW_MS) {
+      lastWarnAt.delete(key)
+    }
+  }
+  while (lastWarnAt.size > WARN_CACHE_MAX_ENTRIES) {
+    const oldest = lastWarnAt.keys().next()
+    if (oldest.done) {
+      break
+    }
+    lastWarnAt.delete(oldest.value)
+  }
+}
+
 function warnRateLimited(key: string, message: string): void {
   const now = Date.now()
-  const prev = lastWarnAt.get(key) ?? 0
-  if (now - prev < WARN_WINDOW_MS) {
+  pruneWarnCache(now)
+  const prev = lastWarnAt.get(key)
+  if (prev !== undefined && now - prev < WARN_WINDOW_MS) {
     return
   }
+  // Why: renderer-originated event names are untrusted; keep the rate-limit
+  // table bounded even if a bad caller sends unique invalid names forever.
+  lastWarnAt.delete(key)
   lastWarnAt.set(key, now)
+  pruneWarnCache(now)
   console.warn(`[telemetry] ${message}`)
 }
 
@@ -76,6 +97,10 @@ export function _resetValidatorWarnCacheForTests(): void {
   lastWarnAt.clear()
 }
 
+export function _getValidatorWarnCacheSizeForTests(): number {
+  return lastWarnAt.size
+}
+
 // Re-exported so `client.ts` can re-validate the merged outgoing payload
 // without reaching into `src/shared/telemetry-events.ts` directly. Keeps the
 // validator as the single surface the client depends on.