diff --git a/README.md b/README.md
index 27fa3a8..155551d 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ Auto-detects the report type from CSV headers. Drop one file or a whole zip.
 
 | Report | What you get |
 |---|---|
-| **Metered Usage** | Actions minutes, runner SKU breakdown, Copilot seats, Packages, LFS, storage costs |
+| **Metered Usage** | Actions minutes, runner SKU breakdown, Copilot seats, Packages, LFS, storage costs. Detailed and summarized exports both supported |
 | **Copilot Premium Requests** | Per-user PRU consumption, model breakdown, quota tracking, AI credit costs |
 | **Copilot Token Usage** | Input/output tokens, cache creation/read, per-model cost with token-level granularity |
 | **GHAS Active Committers** | Advanced Security license consumption by user and repository |
@@ -51,9 +51,10 @@ Auto-detects the report type from CSV headers. Drop one file or a whole zip.
 - Falls back to clipboard if URL exceeds 8,000 characters
 
 **Privacy**
-- 100% client-side. No server, no uploads, no telemetry
+- Your CSVs never leave the browser. No server, no uploads, no telemetry
 - Reports cached in IndexedDB across sessions
 - Sample data auto-removed when real data is imported
+- The one outbound request is an avatar lookup to `api.github.com` for names matching a bot pattern (`*[bot]`). Human usernames are never sent anywhere
 
 ## Quick Start
 
@@ -66,7 +67,19 @@ Drop a CSV onto the upload area, or append `?demo=auto` to load sample data inst
 
 ### Where to Get the CSVs
 
-GitHub billing admins can export usage reports from **Settings → Billing → Usage report → Download CSV**. The app auto-detects the report type from headers.
+Each report lives in a different part of GitHub's billing and admin UI. The app auto-detects the type from the headers, so you never have to say which one you're uploading.
+
+| Report | Where to export it |
+|---|---|
+| **Metered Usage** | Billing & Licensing → Usage → Metered Usage → **Get usage report** |
+| **Copilot Premium Requests** | Billing & Licensing → Usage → Premium request analytics → **Get usage report** |
+| **Copilot Token Usage** | Billing & Licensing → Usage → Premium request analytics → **Get usage report** |
+| **GHAS Active Committers** | Licensing → GitHub Advanced Security → **Download CSV Report** |
+| **Copilot Seat Activity** | AI Controls → Copilot → Access Management → **Download CSV report** |
+| **Dormant Users** | Settings → Compliance → **Export** |
+| **Enterprise Members** | Licensing → **Export** (next to GitHub Enterprise) |
+
+Metered usage exports come in two shapes and both work: **detailed** (up to 31 days, includes the user and workflow that incurred the cost) and **summarized** (up to a year, drops those columns). Pick summarized for long-range trends, detailed when you need to attribute spend to a person or workflow.
 
 ## Tech Stack
 
diff --git a/package.json b/package.json
index 4d5d811..50c0faa 100644
--- a/package.json
+++ b/package.json
@@ -7,7 +7,7 @@
     "dev": "vite",
     "build": "tsc -b && vite build",
     "lint": "eslint .",
-    "typecheck": "tsc --noEmit",
+    "typecheck": "tsc -b --noEmit",
     "test": "vitest run",
     "test:watch": "vitest",
     "test:coverage": "vitest run --coverage",
diff --git a/src/context/ReportContext.tsx b/src/context/ReportContext.tsx
index 2d22899..ba1bc44 100644
--- a/src/context/ReportContext.tsx
+++ b/src/context/ReportContext.tsx
@@ -4,7 +4,7 @@ import { ReportContext } from './report-context';
 import type { CombinedGroup, DateRange } from './report-context';
 import { getCachedParsedReports, getCachedRawCSV, setCachedCSV, removeCachedCSV, clearCachedCSVs } from '../lib/local-storage';
 import { readURLFilterState, writeURLFilterState } from '../lib/url-state';
-import { getReportSchema } from '../lib/report-schema';
+import { getReportSchema, resolveGroupByColumn } from '../lib/report-schema';
 import { formatDateRangeCompact } from '../lib/formatters';
 
 /** Fast FNV-1a hash for dedup — not crypto-grade, just collision-resistant enough for CSV content */
@@ -202,7 +202,8 @@ export function ReportProvider({ children }: { children: ReactNode }) {
         reports: nextReports,
         rawCsvs: nextRawCsvs,
         fileHashes: nextHashes,
-        activeReportIndex: prev.reports.length,
+        activeReportIndex: baseReports.length,
+        groupByColumn: resolveGroupByColumn(report, prev.groupByColumn),
         periodKey: 'all',
         dateRange: null,
         searchQuery: '',
diff --git a/src/lib/report-schema.test.ts b/src/lib/report-schema.test.ts
index a8fbcba..faec0e3 100644
--- a/src/lib/report-schema.test.ts
+++ b/src/lib/report-schema.test.ts
@@ -5,6 +5,7 @@ import {
   PAGE_TYPES,
   PAGE_REPORT_TYPES,
   PRODUCT_METRIC_OPTIONS,
+  resolveGroupByColumn,
 } from './report-schema';
 import { REPORT_TYPES } from './types';
 
@@ -77,3 +78,36 @@ describe('product metric options', () => {
     expect(actions.some(o => o.label === 'Minutes')).toBe(true);
   });
 });
+
+describe('resolveGroupByColumn', () => {
+  const report = (type: string, rows: Array<Record<string, unknown>>) =>
+    ({ type, rows, fileName: 'f.csv', rowCount: rows.length, dateRange: { start: '', end: '' } }) as never;
+
+  it('keeps the current column when the report has data for it', () => {
+    const r = report(REPORT_TYPES.USAGE_REPORT, [{ username: 'ana-reyes', sku: 'actions_linux' }]);
+    expect(resolveGroupByColumn(r, 'username')).toBe('username');
+  });
+
+  it('falls back to the schema default when the column is blank for every row', () => {
+    const rows = Array.from({ length: 50 }, () => ({ username: '', sku: 'actions_linux' }));
+    expect(resolveGroupByColumn(report(REPORT_TYPES.USAGE_REPORT, rows), 'username')).toBe('sku');
+  });
+
+  it('falls back when the column is missing entirely, as in summarized exports', () => {
+    const rows = Array.from({ length: 50 }, () => ({ sku: 'actions_linux' }));
+    expect(resolveGroupByColumn(report(REPORT_TYPES.USAGE_REPORT, rows), 'username')).toBe('sku');
+  });
+
+  it('keeps a column that is blank early but populated later', () => {
+    const rows = Array.from({ length: 500 }, (_, i) => ({ username: i < 400 ? '' : 'kai-nakamura' }));
+    expect(resolveGroupByColumn(report(REPORT_TYPES.USAGE_REPORT, rows), 'username')).toBe('username');
+  });
+
+  it('uses the schema default when there is no current column', () => {
+    expect(resolveGroupByColumn(report(REPORT_TYPES.ENTERPRISE_MEMBERS, []), '')).toBe('licenseType');
+  });
+
+  it('falls back for an empty report rather than keeping an unusable column', () => {
+    expect(resolveGroupByColumn(report(REPORT_TYPES.DORMANT_USERS, []), 'username')).toBe('role');
+  });
+});
diff --git a/src/lib/report-schema.ts b/src/lib/report-schema.ts
index 8d12dbc..024f5aa 100644
--- a/src/lib/report-schema.ts
+++ b/src/lib/report-schema.ts
@@ -1,5 +1,5 @@
 import type { ComponentType } from 'react';
-import type { ReportType } from './types';
+import type { ParsedReport, ReportType } from './types';
 import { REPORT_TYPES } from './types';
 import {
   CopilotIcon,
@@ -347,6 +347,37 @@ export function getAllSchemas(): ReportSchema[] {
   return Object.values(SCHEMA_REGISTRY);
 }
 
+const GROUP_BY_SAMPLE_SIZE = 200;
+
+/**
+ * Pick a group-by column that the report actually has data for.
+ *
+ * Reports of the same type don't always carry the same columns — the
+ * summarized metered usage export drops `username` and `workflow_path`, and
+ * org-level seat activity has no `organization`. Keeping a column that is
+ * blank for every row renders an empty chart, so fall back to the schema
+ * default. Rows are sampled with a stride rather than from the head, since
+ * columns like `username` are legitimately blank for leading storage rows.
+ */
+export function resolveGroupByColumn(
+  report: ParsedReport,
+  currentColumn: string,
+): string {
+  const schema = getReportSchema(report.type);
+  if (!currentColumn) return schema.defaultGroupBy;
+
+  const readColumn = (row: unknown): unknown =>
+    (row as Record<string, unknown> | undefined)?.[currentColumn];
+
+  const rows: readonly unknown[] = report.rows;
+  const stride = Math.max(1, Math.floor(rows.length / GROUP_BY_SAMPLE_SIZE));
+  for (let i = 0; i < rows.length; i += stride) {
+    const value = readColumn(rows[i]);
+    if (value !== undefined && value !== null && value !== '') return currentColumn;
+  }
+  return schema.defaultGroupBy;
+}
+
 /** Sidebar nav page identifiers derived from report types */
 export const PAGE_TYPES = {
   COPILOT: 'copilot',
diff --git a/src/lib/sample-data.ts b/src/lib/sample-data.ts
index c580c23..92b48f2 100644
--- a/src/lib/sample-data.ts
+++ b/src/lib/sample-data.ts
@@ -1,28 +1,34 @@
+import usageReportUrl from '../../examples/usageReport_1_7f2ed6006ee54fb8af73f5cbb7ac1f1d.csv?url';
+import premiumRequestUrl from '../../examples/premiumRequestUsageReport_1_c6fca30f0acd458098a95808eaf43399.csv?url';
+import tokenUsageUrl from '../../examples/Token.Usage.Report.csv?url';
+import seatActivityUrl from '../../examples/octodemo-seat-activity-1774680875.csv?url';
+import ghasCommittersUrl from '../../examples/ghas_active_committers_octodemo_2026-03-27T1521.csv?url';
+import dormantUsersUrl from '../../examples/export-octodemo-1774679438.csv?url';
+import enterpriseMembersUrl from '../../examples/export-octodemo-1774709193.csv?url';
+
+const SAMPLES = [
+  { name: 'usageReport.csv', url: usageReportUrl },
+  { name: 'premiumRequestUsageReport.csv', url: premiumRequestUrl },
+  { name: 'Token.Usage.Report.csv', url: tokenUsageUrl },
+  { name: 'seat-activity.csv', url: seatActivityUrl },
+  { name: 'ghas-active-committers.csv', url: ghasCommittersUrl },
+  { name: 'dormant-users.csv', url: dormantUsersUrl },
+  { name: 'enterprise-members.csv', url: enterpriseMembersUrl },
+] as const;
+
 /**
- * Lazily load example CSV files. These are code-split by Vite
- * and only fetched when explicitly requested (e.g. from the tour prompt).
- * Zero impact on normal users' bundle size.
+ * Load the example CSVs. These are emitted as static assets rather than
+ * imported with `?raw`, which would inline all 15 MB of them into a JS chunk
+ * the browser must download and parse as source before it can be a string.
  */
 export async function loadSampleData(): Promise<Array<{ name: string; content: string }>> {
-  const samples = await Promise.all([
-    import('../../examples/usageReport_1_7f2ed6006ee54fb8af73f5cbb7ac1f1d.csv?raw').then(
-      (m) => ({ name: 'usageReport.csv', content: m.default }),
-    ),
-    import('../../examples/premiumRequestUsageReport_1_c6fca30f0acd458098a95808eaf43399.csv?raw').then(
-      (m) => ({ name: 'premiumRequestUsageReport.csv', content: m.default }),
-    ),
-    import('../../examples/Token.Usage.Report.csv?raw').then(
-      (m) => ({ name: 'Token.Usage.Report.csv', content: m.default }),
-    ),
-    import('../../examples/octodemo-seat-activity-1774680875.csv?raw').then(
-      (m) => ({ name: 'seat-activity.csv', content: m.default }),
-    ),
-    import('../../examples/ghas_active_committers_octodemo_2026-03-27T1521.csv?raw').then(
-      (m) => ({ name: 'ghas-active-committers.csv', content: m.default }),
-    ),
-    import('../../examples/export-octodemo-1774679438.csv?raw').then(
-      (m) => ({ name: 'enterprise-members.csv', content: m.default }),
-    ),
-  ]);
-  return samples;
+  return Promise.all(
+    SAMPLES.map(async ({ name, url }) => {
+      const response = await fetch(url);
+      if (!response.ok) {
+        throw new Error(`Failed to load sample ${name}: ${response.status} ${response.statusText}`);
+      }
+      return { name, content: await response.text() };
+    }),
+  );
 }
diff --git a/src/lib/share-state.test.ts b/src/lib/share-state.test.ts
index 36ad771..10d0fe6 100644
--- a/src/lib/share-state.test.ts
+++ b/src/lib/share-state.test.ts
@@ -8,7 +8,7 @@ describe('share URL round-trip', () => {
   it('buildShareURL → readShareData preserves filter state and CSV data', async () => {
     const { buildShareURL, readShareData } = await import('./share-state');
     Object.defineProperty(window, 'location', {
-      value: { origin: 'http://localhost:5174', pathname: '/tbb/' },
+      value: { origin: 'http://localhost:5174', pathname: '/github-actions-usage-report/' },
       writable: true,
     });
 
@@ -37,7 +37,7 @@ describe('share URL round-trip', () => {
   it('returns null for oversized payloads', async () => {
     const { buildShareURL } = await import('./share-state');
     Object.defineProperty(window, 'location', {
-      value: { origin: 'http://localhost:5174', pathname: '/tbb/' },
+      value: { origin: 'http://localhost:5174', pathname: '/github-actions-usage-report/' },
       writable: true,
     });
 
@@ -62,16 +62,16 @@ describe('clearShareHash', () => {
 
   it('strips share hash and preserves search params', () => {
     Object.defineProperty(window, 'location', {
-      value: { hash: '#data=xyz', pathname: '/tbb/', search: '?tab=table' },
+      value: { hash: '#data=xyz', pathname: '/github-actions-usage-report/', search: '?tab=table' },
       writable: true,
     });
     clearShareHash();
-    expect(replaceStateSpy).toHaveBeenCalledWith(null, '', '/tbb/?tab=table');
+    expect(replaceStateSpy).toHaveBeenCalledWith(null, '', '/github-actions-usage-report/?tab=table');
   });
 
   it('ignores non-share hashes', () => {
     Object.defineProperty(window, 'location', {
-      value: { hash: '#section', pathname: '/tbb/', search: '' },
+      value: { hash: '#section', pathname: '/github-actions-usage-report/', search: '' },
       writable: true,
     });
     clearShareHash();