diff --git a/app/services/prober.ts b/app/services/prober.ts
index d097b44..a07269d 100644
--- a/app/services/prober.ts
+++ b/app/services/prober.ts
@@ -167,8 +167,17 @@ export class Prober {
       if (want <= 0) return
       // The starting points chosen here: in the query Postgres drew random() once for all slices.
       // Over the claimable ones of this tier only: the rest of the queue isn't settled yet.
+      // Per value of unreadable, each an end of the index: over `unreadable >= false` Postgres walked every waiting
+      // entry of the kind, 2.5 minutes a claim at 28M archive candidates (LOG.md 2026-10-18 (74)).
+      const values = unreadable ? [true] : [false, true]
+      const ends = values
+        .map(() => `SELECT min(id) AS lo, max(id) AS hi FROM probe_candidates WHERE status = 'waiting' AND ready AND kind = ? AND unreadable = ?`)
+        .join(' UNION ALL ')
       const [{ lo, hi }] = (
-        await db.rawQuery(`SELECT min(id) AS lo, max(id) AS hi FROM probe_candidates WHERE status = 'waiting' AND ready AND kind = ? AND unreadable >= ?`, [kind, unreadable])
+        await db.rawQuery(
+          `SELECT min(lo) AS lo, max(hi) AS hi FROM (${ends}) e`,
+          values.flatMap((v) => [kind, v])
+        )
       ).rows
       if (lo === null) continue
       const starts = Array.from({ length: SLICES }, () => Number(lo) + Math.floor(Math.random() * (Number(hi) - Number(lo) + 1)))
diff --git a/tests/functional/prober.spec.ts b/tests/functional/prober.spec.ts
new file mode 100644
index 0000000..70b27b7
--- /dev/null
+++ b/tests/functional/prober.spec.ts
@@ -0,0 +1,26 @@
+import { test } from '@japa/runner'
+import db from '@adonisjs/lucid/services/db'
+import testUtils from '@adonisjs/core/services/test_utils'
+import { Prober } from '#services/prober'
+
+test.group('Prober', (group) => {
+  group.each.setup(() => testUtils.db().withGlobalTransaction())
+
+  test('a claim takes each tier: the readable tiers also take unreadable candidates, a kind with only one of them too', async ({ assert }) => {
+    const [row] = await db
+      .table('releases')
+      .insert({ release_key: 'pb'.padEnd(40, '0'), identity_key: 'pb'.padEnd(40, '0'), name: 'pb', source: 'subject', groups: '[]', files: 3 })
+      .returning('id')
+    const candidate = (kind: string, unreadable: boolean, ready = true) => ({
+      release_id: row.id, kind, message_id: `<${kind}-${unreadable}-${ready}@x>`, file: kind, ready, unreadable,
+    })
+    // One per kind, so each tier's id range is a single id (the slices' starts aren't random then).
+    await db.table('probe_candidates').multiInsert([candidate('lone', true), candidate('par2', true), candidate('archive', false), candidate('7z-tail', false, false)])
+
+    const prober = new Prober() as any
+    await prober.claimTiers()
+    assert.sameMembers(prober.queue.map((c: { kind: string }) => c.kind), ['lone', 'par2', 'archive'])
+    const status = Object.fromEntries((await db.from('probe_candidates').select('kind', 'status')).map((c) => [c.kind, c.status]))
+    assert.deepEqual(status, { 'lone': 'taken', 'par2': 'taken', 'archive': 'taken', '7z-tail': 'waiting' })
+  })
+})