diff --git a/src/lib/server/hosts/schema.ts b/src/lib/server/hosts/schema.ts
index 0075062..cb12041 100644
--- a/src/lib/server/hosts/schema.ts
+++ b/src/lib/server/hosts/schema.ts
@@ -29,6 +29,10 @@ export function ensureHostSchema(handle: Database.Database): void {
             UNIQUE(host_id, idempotency_key)
         );
         CREATE INDEX IF NOT EXISTS ec_host_operations_queue ON ec_host_operations(host_id, state, created_at);
+        -- Polling checks cancellations and preparation by kind across retained
+        -- history. The queue index cannot narrow those lookups beyond host_id,
+        -- causing a history scan for every queued command on Node's main thread.
+        CREATE INDEX IF NOT EXISTS ec_host_operations_kind ON ec_host_operations(host_id, kind, created_at);
         CREATE TABLE IF NOT EXISTS ec_host_operation_events (
             id INTEGER PRIMARY KEY AUTOINCREMENT, operation_id TEXT NOT NULL REFERENCES ec_host_operations(id),
             state TEXT NOT NULL, created_at TEXT NOT NULL, error TEXT
diff --git a/tests/unit/native-hosts.test.ts b/tests/unit/native-hosts.test.ts
index bf07be2..e164b98 100644
--- a/tests/unit/native-hosts.test.ts
+++ b/tests/unit/native-hosts.test.ts
@@ -15,6 +15,28 @@ async function enrolled() {
 }
 
 describe('native host enrollment and scoped authentication', () => {
+    it('narrows cancellation lookups by kind instead of scanning completed health history', async () => {
+        const api = await enrolled();
+        api.heartbeat(api.host.id, { ...inventory, capabilities: ['instance.cancel-create', 'operations.health-lane'] });
+        const { db } = await import('../../src/lib/server/db/index.js');
+        const handle = db();
+        const insert = handle.prepare(`INSERT INTO ec_host_operations
+            (id,host_id,kind,payload,state,created_at,updated_at) VALUES(?,?,'instance.inspect','{}','completed',?,?)`);
+        const at = new Date().toISOString();
+        handle.transaction(() => {
+            for (let i = 0; i < 10_000; i++) insert.run(`history-${i}`, api.host.id, at, at);
+        })();
+        const inspect = api.queueHostOperation(api.host.id, 'instance.inspect', {});
+        const prepare = vi.spyOn(handle, 'prepare');
+        expect(api.pendingHostOperations(api.host.id, 'health').map(op => op.id)).toEqual([inspect.id]);
+        const query = prepare.mock.calls.map(([sql]) => sql).find(sql => sql.includes('SELECT * FROM ec_host_operations o'))!;
+        prepare.mockRestore();
+        // Assert the actual poll's access path, avoiding hardware-dependent timing thresholds.
+        const plan = handle.prepare(`EXPLAIN QUERY PLAN ${query}`).all(api.host.id, 1, 1) as { detail: string }[];
+        expect(plan.find(row => row.detail.includes('SEARCH cancellation'))?.detail)
+            .toContain('(host_id=? AND kind=?)');
+    });
+
     it('reserves health delivery while a file backlog is pending and bounds background batches', async () => {
         const api = await enrolled();
         api.heartbeat(api.host.id, { ...inventory, capabilities: ['operations.health-lane'] });