fix(perf): memoize synced pricing reads

src/lib/pricingSync.ts

@@ -11,7 +11,7 @@
  */
 
 import { getDbInstance } from "./db/core";
-import { invalidateDbCache } from "./db/readCache";
+import { invalidateDbCache, getModelCatalogCacheVersion } from "./db/readCache";
 import { backupDbFile } from "./db/backup";
 
 // ─── Types ───────────────────────────────────────────────
@@ -232,10 +232,27 @@ function toRecord(value: unknown): Record<string, unknown> {
   return value && typeof value === "object" ? (value as Record<string, unknown>) : {};
 }
 
+// getSyncedPricing() re-ran the SELECT + JSON.parse of the pricing_synced
+// blobs on every call — resolveCatalogPricing() calls it per model lookup, so
+// each call rebuilt a fresh object and findInsensitive() (WeakMap keyed by
+// object identity) rebuilt its lowercase index per lookup, emitting hundreds
+// of 'case-insensitive key collision' warnings per second and pinning CPU.
+// Memoized here, invalidated via the same modelCatalogCacheVersion signal
+// saveSyncedPricing/clearSyncedPricing already bump through
+// invalidateDbCache("pricing") — mirrors getModelsDevPricing() in
+// modelsDevSync.ts.
+let pricingMemo: PricingByProvider | null = null;
+let pricingMemoVersion = -1; // -1: never equals a real cacheVersion (starts at 0), guarantees a miss on the first call
+
 /**
  * Read synced pricing from `pricing_synced` namespace.
  */
 export function getSyncedPricing(): PricingByProvider {
+  const currentVersion = getModelCatalogCacheVersion();
+  if (pricingMemo !== null && pricingMemoVersion === currentVersion) {
+    return pricingMemo;
+  }
+
   const db = getDbInstance();
   const rows = db
     .prepare("SELECT key, value FROM key_value WHERE namespace = 'pricing_synced'")
@@ -252,6 +269,8 @@ export function getSyncedPricing(): PricingByProvider {
       console.warn(`[PRICING_SYNC] Corrupted data for provider "${key}", skipping`);
     }
   }
+  pricingMemo = synced;
+  pricingMemoVersion = currentVersion;
   return synced;
 }
 

tests/unit/pricing-sync-memoization.test.ts

@@ -0,0 +1,68 @@
+import assert from "node:assert/strict";
+import { describe, it, before, after, mock } from "node:test";
+import { getDbInstance } from "../../src/lib/db/core.ts";
+import {
+  getSyncedPricing,
+  saveSyncedPricing,
+  clearSyncedPricing,
+} from "../../src/lib/pricingSync.ts";
+
+describe("getSyncedPricing memoization", () => {
+  before(() => {
+    saveSyncedPricing({
+      openai: {
+        "gpt-4o": { input: 2.5, output: 10 },
+      },
+    });
+  });
+
+  after(() => {
+    try {
+      clearSyncedPricing();
+    } catch {
+      // ignore
+    }
+  });
+
+  it("returns the same object reference for repeated reads within the same cache version", () => {
+    const first = getSyncedPricing();
+    const second = getSyncedPricing();
+    const third = getSyncedPricing();
+    // The saturation bug rebuilt a fresh object on every call; resolveCatalogPricing()
+    // calls this per model, so a fresh object per call re-ran the SELECT + JSON.parse
+    // and rebuilt the findInsensitive() lowercase index per lookup (~400 warnings/s).
+    assert.equal(second, first);
+    assert.equal(third, first);
+  });
+
+  it("hits the DB once for repeated reads within the same cache version", () => {
+    const db = getDbInstance();
+    const prepareSpy = mock.method(db, "prepare");
+    const callsBefore = prepareSpy.mock.calls.length;
+
+    getSyncedPricing();
+    getSyncedPricing();
+    getSyncedPricing();
+
+    const callsAfter = prepareSpy.mock.calls.length;
+    prepareSpy.mock.restore();
+
+    // Memoized, 3 calls should cost at most 1 real DB round-trip (0 if a prior
+    // test already warmed the cache at the same version).
+    assert.ok(
+      callsAfter - callsBefore <= 1,
+      `expected at most 1 db.prepare() call across 3 reads, got ${callsAfter - callsBefore}`
+    );
+  });
+
+  it("returns a new reference with fresh data after a pricing write invalidates the cache", () => {
+    const warm = getSyncedPricing(); // warm the memo at the current cache version
+    saveSyncedPricing({
+      anthropic: { "claude-x": { input: 1, output: 2 } },
+    });
+    const pricing = getSyncedPricing();
+    assert.notEqual(pricing, warm, "invalidation must rebuild, not reuse the stale object");
+    assert.ok(pricing.anthropic, "cache should reflect the write, not a stale snapshot");
+    assert.equal(pricing.anthropic["claude-x"].input, 1);
+  });
+});