diff --git a/src/web-server/usage/codex-native-usage-collector.ts b/src/web-server/usage/codex-native-usage-collector.ts
index 9d4c8f4b..160fcfb7 100644
--- a/src/web-server/usage/codex-native-usage-collector.ts
+++ b/src/web-server/usage/codex-native-usage-collector.ts
@@ -1,6 +1,7 @@
 import * as fs from 'fs';
 import * as path from 'path';
 import * as readline from 'readline';
+import { getCcsDir } from '../../utils/config-manager';
 import type { RawUsageEntry } from '../jsonl-parser';
 import { resolveCodexConfigPaths } from '../services/codex-dashboard-service';
 
@@ -8,6 +9,24 @@ interface CodexNativeUsageCollectorOptions {
   env?: NodeJS.ProcessEnv;
   homeDir?: string;
   includeCliproxySessions?: boolean;
+  cacheDir?: string;
+  disableCache?: boolean;
+}
+
+const CODEX_NATIVE_USAGE_CACHE_VERSION = 1;
+
+interface CachedRolloutFile {
+  path: string;
+  size: number;
+  mtimeMs: number;
+  entries: RawUsageEntry[];
+}
+
+interface CodexNativeUsageCache {
+  version: typeof CODEX_NATIVE_USAGE_CACHE_VERSION;
+  includeCliproxySessions: boolean;
+  generatedAt: number;
+  files: Record<string, CachedRolloutFile>;
 }
 
 interface CodexTokenSnapshot {
@@ -82,6 +101,85 @@ async function collectRolloutFiles(dir: string): Promise<string[]> {
   return files.sort();
 }
 
+function getDefaultCacheDir(): string {
+  return path.join(getCcsDir(), 'cache');
+}
+
+function getCacheFilePath(cacheDir: string, includeCliproxySessions: boolean): string {
+  return path.join(
+    cacheDir,
+    includeCliproxySessions
+      ? 'codex-native-usage-with-cliproxy-v1.json'
+      : 'codex-native-usage-v1.json'
+  );
+}
+
+function isCachedRolloutFile(value: unknown): value is CachedRolloutFile {
+  if (!isObject(value)) return false;
+  return (
+    typeof value.path === 'string' &&
+    typeof value.size === 'number' &&
+    typeof value.mtimeMs === 'number' &&
+    Array.isArray(value.entries)
+  );
+}
+
+function isCodexNativeUsageCache(value: unknown): value is CodexNativeUsageCache {
+  if (!isObject(value)) return false;
+  if (value.version !== CODEX_NATIVE_USAGE_CACHE_VERSION) return false;
+  if (typeof value.includeCliproxySessions !== 'boolean') return false;
+  if (typeof value.generatedAt !== 'number') return false;
+  if (!isObject(value.files)) return false;
+  return Object.values(value.files).every(isCachedRolloutFile);
+}
+
+function readUsageCache(
+  cacheDir: string,
+  includeCliproxySessions: boolean
+): CodexNativeUsageCache | null {
+  try {
+    const cachePath = getCacheFilePath(cacheDir, includeCliproxySessions);
+    if (!fs.existsSync(cachePath)) return null;
+
+    const parsed = JSON.parse(fs.readFileSync(cachePath, 'utf8')) as unknown;
+    if (!isCodexNativeUsageCache(parsed)) return null;
+    if (parsed.includeCliproxySessions !== includeCliproxySessions) return null;
+
+    return parsed;
+  } catch {
+    return null;
+  }
+}
+
+function writeUsageCache(cacheDir: string, cache: CodexNativeUsageCache): void {
+  try {
+    fs.mkdirSync(cacheDir, { recursive: true });
+    const cachePath = getCacheFilePath(cacheDir, cache.includeCliproxySessions);
+    const tempPath = `${cachePath}.${process.pid}.tmp`;
+    fs.writeFileSync(tempPath, JSON.stringify(cache), 'utf8');
+    fs.renameSync(tempPath, cachePath);
+  } catch {
+    // Best-effort only.
+  }
+}
+
+function getMtimeMsFingerprint(stats: fs.Stats): number {
+  return stats.mtimeMs;
+}
+
+function hasMatchingFingerprint(
+  cached: CachedRolloutFile | undefined,
+  filePath: string,
+  stats: fs.Stats
+): cached is CachedRolloutFile {
+  return (
+    !!cached &&
+    cached.path === filePath &&
+    cached.size === stats.size &&
+    cached.mtimeMs === getMtimeMsFingerprint(stats)
+  );
+}
+
 async function parseRolloutFile(
   filePath: string,
   includeCliproxySessions: boolean
@@ -183,6 +281,7 @@ async function parseRolloutFile(
 export async function scanCodexNativeUsageEntries(
   options: CodexNativeUsageCollectorOptions = {}
 ): Promise<RawUsageEntry[]> {
+  const includeCliproxySessions = options.includeCliproxySessions === true;
   const { baseDir } = resolveCodexConfigPaths({
     env: options.env,
     homeDir: options.homeDir,
@@ -190,9 +289,42 @@ export async function scanCodexNativeUsageEntries(
   const rolloutFiles = await collectRolloutFiles(path.join(baseDir, 'sessions'));
   const entries: RawUsageEntry[] = [];
 
-  for (const filePath of rolloutFiles) {
-    entries.push(...(await parseRolloutFile(filePath, options.includeCliproxySessions === true)));
+  if (options.disableCache === true) {
+    for (const filePath of rolloutFiles) {
+      entries.push(...(await parseRolloutFile(filePath, includeCliproxySessions)));
+    }
+    return entries;
   }
 
+  const cacheDir = options.cacheDir ?? getDefaultCacheDir();
+  const previousCache = readUsageCache(cacheDir, includeCliproxySessions);
+  const nextCache: CodexNativeUsageCache = {
+    version: CODEX_NATIVE_USAGE_CACHE_VERSION,
+    includeCliproxySessions,
+    generatedAt: Date.now(),
+    files: {},
+  };
+
+  for (const filePath of rolloutFiles) {
+    const stats = await fs.promises.stat(filePath);
+    const cached = previousCache?.files[filePath];
+
+    if (hasMatchingFingerprint(cached, filePath, stats)) {
+      entries.push(...cached.entries);
+      nextCache.files[filePath] = cached;
+      continue;
+    }
+
+    const fileEntries = await parseRolloutFile(filePath, includeCliproxySessions);
+    entries.push(...fileEntries);
+    nextCache.files[filePath] = {
+      path: filePath,
+      size: stats.size,
+      mtimeMs: getMtimeMsFingerprint(stats),
+      entries: fileEntries,
+    };
+  }
+
+  writeUsageCache(cacheDir, nextCache);
   return entries;
 }
diff --git a/tests/unit/web-server/codex-native-usage-collector.test.ts b/tests/unit/web-server/codex-native-usage-collector.test.ts
index aa32db7d..50d68991 100644
--- a/tests/unit/web-server/codex-native-usage-collector.test.ts
+++ b/tests/unit/web-server/codex-native-usage-collector.test.ts
@@ -2,8 +2,18 @@ import { afterEach, beforeEach, describe, expect, it } from 'bun:test';
 import * as fs from 'fs';
 import * as os from 'os';
 import * as path from 'path';
+import { runWithScopedCcsHome } from '../../../src/utils/config-manager';
 import { scanCodexNativeUsageEntries } from '../../../src/web-server/usage/codex-native-usage-collector';
 
+type TestUsageCache = {
+  includeCliproxySessions: boolean;
+  files: Record<string, { mtimeMs: number; entries: unknown[] }>;
+};
+
+function readTestUsageCache(cachePath: string): TestUsageCache {
+  return JSON.parse(fs.readFileSync(cachePath, 'utf8')) as TestUsageCache;
+}
+
 function writeCodexRollout(
   baseDir: string,
   options: {
@@ -12,7 +22,7 @@ function writeCodexRollout(
     model?: string;
     cwd?: string;
   } = {}
-): void {
+): string {
   const sessionId = options.sessionId ?? 'codex-session-1';
   const rolloutDir = path.join(baseDir, 'sessions', '2026', '03', '02');
   const rolloutPath = path.join(rolloutDir, `rollout-${sessionId}.jsonl`);
@@ -124,6 +134,38 @@ function writeCodexRollout(
 
   fs.mkdirSync(rolloutDir, { recursive: true });
   fs.writeFileSync(rolloutPath, `${lines.join('\n')}\n`, 'utf8');
+  return rolloutPath;
+}
+
+function appendCodexTokenCount(rolloutPath: string): void {
+  fs.appendFileSync(
+    rolloutPath,
+    `${JSON.stringify({
+      timestamp: '2026-03-02T10:15:00.000Z',
+      type: 'event_msg',
+      payload: {
+        type: 'token_count',
+        info: {
+          total_token_usage: {
+            input_tokens: 200,
+            cached_input_tokens: 40,
+            output_tokens: 20,
+            reasoning_output_tokens: 5,
+            total_tokens: 265,
+          },
+          last_token_usage: {
+            input_tokens: 50,
+            cached_input_tokens: 10,
+            output_tokens: 10,
+            reasoning_output_tokens: 2,
+            total_tokens: 72,
+          },
+          model_context_window: 200000,
+        },
+      },
+    })}\n`,
+    'utf8'
+  );
 }
 
 describe('codex native usage collector', () => {
@@ -137,13 +179,21 @@ describe('codex native usage collector', () => {
     fs.rmSync(tempRoot, { recursive: true, force: true });
   });
 
+  function getCacheDir(): string {
+    const cacheDir = path.join(tempRoot, 'ccs-cache');
+    fs.mkdirSync(cacheDir, { recursive: true });
+    return cacheDir;
+  }
+
   it('parses token_count events into raw usage entries and suppresses duplicates', async () => {
     writeCodexRollout(tempRoot);
 
-    const entries = await scanCodexNativeUsageEntries({
-      env: { CODEX_HOME: tempRoot },
-      homeDir: tempRoot,
-    });
+    const entries = await runWithScopedCcsHome(tempRoot, () =>
+      scanCodexNativeUsageEntries({
+        env: { CODEX_HOME: tempRoot },
+        homeDir: tempRoot,
+      })
+    );
 
     expect(entries).toHaveLength(2);
     expect(entries[0]).toMatchObject({
@@ -166,10 +216,12 @@ describe('codex native usage collector', () => {
   it('skips cliproxy-backed codex sessions by default to avoid double counting', async () => {
     writeCodexRollout(tempRoot, { modelProvider: 'cliproxy' });
 
-    const entries = await scanCodexNativeUsageEntries({
-      env: { CODEX_HOME: tempRoot },
-      homeDir: tempRoot,
-    });
+    const entries = await runWithScopedCcsHome(tempRoot, () =>
+      scanCodexNativeUsageEntries({
+        env: { CODEX_HOME: tempRoot },
+        homeDir: tempRoot,
+      })
+    );
 
     expect(entries).toHaveLength(0);
   });
@@ -177,11 +229,121 @@ describe('codex native usage collector', () => {
   it('also skips ccs_runtime-backed codex bridge sessions by default', async () => {
     writeCodexRollout(tempRoot, { modelProvider: 'ccs_runtime' });
 
-    const entries = await scanCodexNativeUsageEntries({
-      env: { CODEX_HOME: tempRoot },
-      homeDir: tempRoot,
-    });
+    const entries = await runWithScopedCcsHome(tempRoot, () =>
+      scanCodexNativeUsageEntries({
+        env: { CODEX_HOME: tempRoot },
+        homeDir: tempRoot,
+      })
+    );
 
     expect(entries).toHaveLength(0);
   });
+
+  it('reuses cached rollout entries when file size and mtime are unchanged', async () => {
+    const rolloutPath = writeCodexRollout(tempRoot);
+    const cacheDir = getCacheDir();
+    const stableMtime = new Date('2026-03-02T10:20:00.000Z');
+    fs.utimesSync(rolloutPath, stableMtime, stableMtime);
+
+    const firstEntries = await scanCodexNativeUsageEntries({
+      env: { CODEX_HOME: tempRoot },
+      homeDir: tempRoot,
+      cacheDir,
+    });
+
+    const cachePath = path.join(cacheDir, 'codex-native-usage-v1.json');
+    const originalStats = fs.statSync(rolloutPath);
+    const originalCache = readTestUsageCache(cachePath);
+    const originalCachedRollout = originalCache.files[rolloutPath];
+    expect(originalCachedRollout?.mtimeMs).toBe(originalStats.mtimeMs);
+
+    const originalContent = fs.readFileSync(rolloutPath, 'utf8');
+    fs.writeFileSync(rolloutPath, '#'.repeat(originalContent.length), 'utf8');
+    fs.utimesSync(rolloutPath, stableMtime, stableMtime);
+
+    const secondEntries = await scanCodexNativeUsageEntries({
+      env: { CODEX_HOME: tempRoot },
+      homeDir: tempRoot,
+      cacheDir,
+    });
+
+    expect(secondEntries).toEqual(firstEntries);
+  });
+
+  it('reparses a rollout file after its size changes', async () => {
+    const rolloutPath = writeCodexRollout(tempRoot);
+    const cacheDir = getCacheDir();
+
+    const firstEntries = await scanCodexNativeUsageEntries({
+      env: { CODEX_HOME: tempRoot },
+      homeDir: tempRoot,
+      cacheDir,
+    });
+
+    appendCodexTokenCount(rolloutPath);
+
+    const secondEntries = await scanCodexNativeUsageEntries({
+      env: { CODEX_HOME: tempRoot },
+      homeDir: tempRoot,
+      cacheDir,
+    });
+
+    expect(firstEntries).toHaveLength(2);
+    expect(secondEntries).toHaveLength(3);
+    expect(secondEntries[2]).toMatchObject({
+      inputTokens: 50,
+      cacheReadTokens: 10,
+      outputTokens: 12,
+    });
+  });
+
+  it('falls back to parsing rollout files when the cache file is corrupt', async () => {
+    writeCodexRollout(tempRoot);
+    const cacheDir = getCacheDir();
+    fs.writeFileSync(path.join(cacheDir, 'codex-native-usage-v1.json'), '{not-json', 'utf8');
+
+    const entries = await scanCodexNativeUsageEntries({
+      env: { CODEX_HOME: tempRoot },
+      homeDir: tempRoot,
+      cacheDir,
+    });
+
+    expect(entries).toHaveLength(2);
+  });
+
+  it('keeps default and include-cliproxy cache entries separate', async () => {
+    writeCodexRollout(tempRoot, { modelProvider: 'cliproxy' });
+    const cacheDir = getCacheDir();
+
+    const defaultEntries = await scanCodexNativeUsageEntries({
+      env: { CODEX_HOME: tempRoot },
+      homeDir: tempRoot,
+      cacheDir,
+    });
+
+    const includedEntries = await scanCodexNativeUsageEntries({
+      env: { CODEX_HOME: tempRoot },
+      homeDir: tempRoot,
+      includeCliproxySessions: true,
+      cacheDir,
+    });
+
+    expect(defaultEntries).toHaveLength(0);
+    expect(includedEntries).toHaveLength(2);
+
+    const defaultCachePath = path.join(cacheDir, 'codex-native-usage-v1.json');
+    const includeCachePath = path.join(cacheDir, 'codex-native-usage-with-cliproxy-v1.json');
+    expect(fs.existsSync(defaultCachePath)).toBe(true);
+    expect(fs.existsSync(includeCachePath)).toBe(true);
+
+    const defaultCache = readTestUsageCache(defaultCachePath);
+    const includeCache = readTestUsageCache(includeCachePath);
+    const defaultCachedRollout = defaultCache.files[Object.keys(defaultCache.files)[0] ?? ''];
+    const includeCachedRollout = includeCache.files[Object.keys(includeCache.files)[0] ?? ''];
+
+    expect(defaultCache.includeCliproxySessions).toBe(false);
+    expect(defaultCachedRollout?.entries).toHaveLength(0);
+    expect(includeCache.includeCliproxySessions).toBe(true);
+    expect(includeCachedRollout?.entries).toHaveLength(2);
+  });
 });