⚡ Bolt: Optimize Language Filtering

.jules/bolt.md

@@ -0,0 +1,5 @@
+# Bolt's Performance Journal
+
+## 2026-03-01 - Optimize Language Filtering in MCP Shared Utilities
+**Learning:** In high-concurrency MCP environments, repeatedly scanning full collections using chained high-order array methods (`.filter().slice().map()`) introduces unnecessary CPU usage and temporary garbage collector overhead. By replacing the chains with a single `for-of` loop that exits early once the `limit` threshold is satisfied, we can skip processing the rest of the collection entirely. This avoids redundant string allocations (`toLowerCase`) and substring match checks for matching languages once the target count has been reached.
+**Action:** Avoid chaining array operations when querying or filtering lists with a known limit. Instead, utilize early-terminating loops with `break` statement to process items in a single pass.

packages/mcp/src/shared/language-filter.ts

@@ -12,25 +12,35 @@ const DEFAULT_LIMIT = 5;
  * Filter languages by case-insensitive substring match on name, display_name, or aliases.
  * Returns up to `limit` matches (default 5) with fields needed to choose
  * the exact `get_example` language input.
+ *
+ * Optimized to perform single-pass filtering and mapping with early exit once the limit is met,
+ * and maintains strict short-circuiting of match conditions to maximize execution speed.
  */
 export function filterLanguages(
   languages: Language[],
   query: string,
   limit: number = DEFAULT_LIMIT,
 ): LanguageMatch[] {
   const lowerQuery = query.toLowerCase();
+  const results: LanguageMatch[] = [];
 
-  return languages
-    .filter(
-      (lang) =>
-        lang.name.toLowerCase().includes(lowerQuery) ||
-        lang.display_name.toLowerCase().includes(lowerQuery) ||
-        lang.aliases.some((a) => a.toLowerCase().includes(lowerQuery)),
-    )
-    .slice(0, limit)
-    .map(({ name, display_name, aliases }) => ({
-      name,
-      display_name,
-      aliases,
-    }));
+  for (const lang of languages) {
+    if (results.length >= limit) {
+      break;
+    }
+
+    if (
+      lang.name.toLowerCase().includes(lowerQuery) ||
+      (lang.display_name?.toLowerCase().includes(lowerQuery) ?? false) ||
+      (lang.aliases?.some((a) => a.toLowerCase().includes(lowerQuery)) ?? false)
+    ) {
+      results.push({
+        name: lang.name,
+        display_name: lang.display_name,
+        aliases: lang.aliases,
+      });
+    }
+  }
+
+  return results;
 }

src/services/locked-auth-storage.test.ts

@@ -225,6 +225,7 @@ describe("LockedAuthStorage", () => {
     const storage = new LockedAuthStorage(createMockAuthStorage(), fsWithHome, {
       isOwnerAlive: async () => true,
       lockTimeoutMs: 10,
+      getProcessStartedAt: testProcessStartedAt,
     });
 
     await expect(storage.loadTokens(baseUrl)).resolves.toBeNull();
@@ -234,7 +235,9 @@ describe("LockedAuthStorage", () => {
   it("clearActiveTokensIfUnchanged delegates through the lock", async () => {
     const { fsWithHome } = await createStoragePaths();
     const inner = createMockAuthStorage();
-    const storage = new LockedAuthStorage(inner, fsWithHome);
+    const storage = new LockedAuthStorage(inner, fsWithHome, {
+      getProcessStartedAt: testProcessStartedAt,
+    });
     const token = createValidTokenData();
 
     await storage.clearActiveTokensIfUnchanged(baseUrl, token);
@@ -250,6 +253,7 @@ describe("LockedAuthStorage", () => {
     const inner = createMockAuthStorage();
     const storage = new LockedAuthStorage(inner, fsWithHome, {
       lockTimeoutMs: 100,
+      getProcessStartedAt: testProcessStartedAt,
     });
 
     // Would time out acquiring the lock again if it were not re-entrant.
@@ -265,7 +269,7 @@ describe("LockedAuthStorage", () => {
     const storage = new LockedAuthStorage(
       new AuthStorageImpl(fs, configDir),
       fsWithHome,
-      { lockTimeoutMs: 100 },
+      { lockTimeoutMs: 100, getProcessStartedAt: testProcessStartedAt },
     );
     const token = createValidTokenData({ accessToken: "nested" });
 
@@ -282,13 +286,17 @@ describe("LockedAuthStorage", () => {
       "XDG_CONFIG_HOME",
       join(root, "xdg-a"),
       () =>
-        new LockedAuthStorage(new AuthStorageImpl(fs, configDir), fsWithHome),
+        new LockedAuthStorage(new AuthStorageImpl(fs, configDir), fsWithHome, {
+          getProcessStartedAt: testProcessStartedAt,
+        }),
     );
     const second = await withTestEnvVar(
       "XDG_CONFIG_HOME",
       join(root, "xdg-b"),
       () =>
-        new LockedAuthStorage(new AuthStorageImpl(fs, configDir), fsWithHome),
+        new LockedAuthStorage(new AuthStorageImpl(fs, configDir), fsWithHome, {
+          getProcessStartedAt: testProcessStartedAt,
+        }),
     );
     let active = 0;
     let maxActive = 0;
@@ -321,7 +329,7 @@ describe("LockedAuthStorage", () => {
     const storage = new LockedAuthStorage(
       new AuthStorageImpl(fs, configDir),
       fsWithHome,
-      { lockTimeoutMs: 100 },
+      { lockTimeoutMs: 100, getProcessStartedAt: testProcessStartedAt },
     );
     const token = createValidTokenData({ accessToken: "fresh" });
 
@@ -345,7 +353,11 @@ describe("LockedAuthStorage", () => {
     const storage = new LockedAuthStorage(
       new AuthStorageImpl(fs, configDir),
       fsWithHome,
-      { isOwnerAlive: async () => true, lockTimeoutMs: 100 },
+      {
+        isOwnerAlive: async () => true,
+        lockTimeoutMs: 100,
+        getProcessStartedAt: testProcessStartedAt,
+      },
     );
 
     await expect(