fix(auto): rate-limit empty-pool AUTO warnings (#10344)

Family resolves like auto/zai with no connected models logged a warn
on every call (about once a minute per poll). Keep the empty-pool
behavior; emit the warn at most once per label per 60s.

Co-authored-by: Ravi Tharuma <RaviTharuma@users.noreply.github.com>
Co-authored-by: diegosouzapw <diegosouza.pw@gmail.com>

changelog.d/fixes/auto-empty-pool-log-once.md

@@ -0,0 +1 @@
+- **fix(auto):** rate-limit `auto/<family> matched no connected models` warnings to once per minute per label (`open-sse/services/autoCombo/virtualFactory.ts`)

open-sse/services/autoCombo/virtualFactory.ts

@@ -44,6 +44,23 @@ export interface AutoComboSpec {
   family?: ModelFamily;
 }
 
+/** Rate-limit empty-pool AUTO warns (same label can be resolved many times/min). */
+const emptyPoolWarnAt = new Map<string, number>();
+export const EMPTY_POOL_WARN_INTERVAL_MS = 60_000;
+
+export function warnEmptyAutoPoolOnce(label: string, message: string, now = Date.now()): boolean {
+  const last = emptyPoolWarnAt.get(label) ?? 0;
+  if (now - last < EMPTY_POOL_WARN_INTERVAL_MS) return false;
+  emptyPoolWarnAt.set(label, now);
+  log.warn("AUTO", message);
+  return true;
+}
+
+/** Test-only: reset the debounce map. */
+export function resetEmptyAutoPoolWarnStateForTests(): void {
+  emptyPoolWarnAt.clear();
+}
+
 /** Minimal connection shape needed for virtual auto-combo factory */
 interface VirtualFactoryConn extends ConnectionFields {
   id: string;
@@ -692,8 +709,8 @@ export async function createVirtualAutoComboFromPrepared(
       // Family combos always degrade to an empty pool when unavailable — a family
       // is a hard identity constraint, not a soft optimization bias, so there is
       // no sensible "fall back to the full pool" behavior for it.
-      log.warn(
-        "AUTO",
+      warnEmptyAutoPoolOnce(
+        label,
         `${label} matched no connected models; returning an empty pool.${spec?.family ? "" : ' Set OMNIROUTE_AUTO_FREE_FALLBACK_TO_FULL_POOL=true to restore the legacy "use full pool" behavior.'}`
       );
       effectivePool = [];

tests/unit/auto-empty-pool-warn-once.test.ts

@@ -0,0 +1,18 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+
+import {
+  EMPTY_POOL_WARN_INTERVAL_MS,
+  resetEmptyAutoPoolWarnStateForTests,
+  warnEmptyAutoPoolOnce,
+} from "../../open-sse/services/autoCombo/virtualFactory.ts";
+
+test("warnEmptyAutoPoolOnce emits at most once per label per interval", () => {
+  resetEmptyAutoPoolWarnStateForTests();
+  const t0 = 1_000_000;
+  assert.equal(warnEmptyAutoPoolOnce("auto/zai", "empty", t0), true);
+  assert.equal(warnEmptyAutoPoolOnce("auto/zai", "empty", t0 + 1), false);
+  assert.equal(warnEmptyAutoPoolOnce("auto/zai", "empty", t0 + EMPTY_POOL_WARN_INTERVAL_MS - 1), false);
+  assert.equal(warnEmptyAutoPoolOnce("auto/other", "empty", t0 + 1), true);
+  assert.equal(warnEmptyAutoPoolOnce("auto/zai", "empty", t0 + EMPTY_POOL_WARN_INTERVAL_MS), true);
+});