diff --git a/mobile/app/(tabs)/import.tsx b/mobile/app/(tabs)/import.tsx
index 9e41d04..0c6458e 100644
--- a/mobile/app/(tabs)/import.tsx
+++ b/mobile/app/(tabs)/import.tsx
@@ -4,10 +4,15 @@ import { useSQLiteContext } from 'expo-sqlite';
 import { useState } from 'react';
 import { Alert, Pressable, ScrollView, StyleSheet, Text, View } from 'react-native';
 import { insertActivity } from '@/db/queries';
+import { extractFile } from '@/extraction/extractActivity';
+
+const FIT_EXTENSIONS  = ['.fit', '.fit.gz'];
+const OTHER_EXTENSIONS = ['.gpx', '.tcx', '.gpx.gz', '.tcx.gz'];
+const ALL_NATIVE_EXTENSIONS = [...FIT_EXTENSIONS, ...OTHER_EXTENSIONS];
 
 type ImportState =
   | { status: 'idle' }
-  | { status: 'loading' }
+  | { status: 'loading'; msg: string }
   | { status: 'done'; title: string; id: string }
   | { status: 'error'; message: string };
 
@@ -16,7 +21,7 @@ export default function ImportScreen() {
   const [state, setState] = useState<ImportState>({ status: 'idle' });
 
   async function pickFile() {
-    setState({ status: 'loading' });
+    setState({ status: 'loading', msg: 'Picking file…' });
     try {
       const result = await DocumentPicker.getDocumentAsync({
         type: ['*/*'],
@@ -28,42 +33,35 @@ export default function ImportScreen() {
       }
 
       const asset = result.assets[0];
-      const name = asset.name ?? '';
-      const uri = asset.uri;
+      const name  = asset.name ?? '';
+      const uri   = asset.uri;
       const lower = name.toLowerCase();
 
       if (lower.endsWith('.json')) {
-        await importBasJson(uri, db);
-        const detail = JSON.parse(await FileSystem.readAsStringAsync(uri));
-        setState({ status: 'done', title: detail.title ?? detail.id, id: detail.id });
-      } else if (['.fit', '.gpx', '.tcx', '.fit.gz', '.gpx.gz', '.tcx.gz'].some(ext => lower.endsWith(ext))) {
-        // Phase 1: Pyodide extraction. Placeholder for now.
-        Alert.alert(
-          'Extraction coming in Phase 1',
-          `File "${name}" received. FIT/GPX/TCX extraction via Pyodide will be added in Phase 1. For now, you can import a pre-extracted BAS .json file.`,
-        );
-        setState({ status: 'idle' });
+        await importBasJson(uri, name, db);
+      } else if (ALL_NATIVE_EXTENSIONS.some(ext => lower.endsWith(ext))) {
+        await importNativeFile(uri, name, db);
       } else {
         setState({ status: 'error', message: `Unsupported file type: ${name}` });
       }
     } catch (e: unknown) {
-      setState({ status: 'error', message: e instanceof Error ? e.message : String(e) });
+      const msg = e instanceof Error ? e.message : String(e);
+      setState({ status: 'error', message: msg });
     }
   }
 
-  async function importBasJson(uri: string, dbCtx: typeof db) {
-    const text = await FileSystem.readAsStringAsync(uri);
+  // ── BAS JSON import (no extraction needed) ──────────────────────────────────
+
+  async function importBasJson(uri: string, name: string, dbCtx: typeof db) {
+    setState({ status: 'loading', msg: 'Importing…' });
+    const text   = await FileSystem.readAsStringAsync(uri);
     const detail = JSON.parse(text);
 
     if (!detail.id || !detail.started_at) {
       throw new Error('Not a valid BAS activity JSON (missing id or started_at)');
     }
 
-    // Simple hash: SHA-256 not available without a library, use content length + id as stand-in.
-    // Phase 1 will use a proper hash.
-    const hash = `${detail.id}-${text.length}`;
-
-    // Copy to permanent storage
+    const hash    = detail.source_hash ?? `${detail.id}-${text.length}`;
     const origDir = `${FileSystem.documentDirectory}originals/`;
     await FileSystem.makeDirectoryAsync(origDir, { intermediates: true });
     const dest = `${origDir}${detail.id}.json`;
@@ -78,6 +76,53 @@ export default function ImportScreen() {
       original_path: dest,
       origin: 'local',
     });
+
+    setState({ status: 'done', title: detail.title ?? detail.id, id: detail.id });
+  }
+
+  // ── FIT / GPX / TCX import via Pyodide extraction ──────────────────────────
+
+  async function importNativeFile(uri: string, name: string, dbCtx: typeof db) {
+    setState({ status: 'loading', msg: 'Reading file…' });
+
+    // Read the original file as base64 so we can (a) pass it to the WebView
+    // and (b) copy it to permanent storage without a second read.
+    const base64 = await FileSystem.readAsStringAsync(uri, {
+      encoding: FileSystem.EncodingType.Base64,
+    });
+
+    // Wheel URL: prefer the configured instance; fall back to bincio.org.
+    const instanceUrl = await getInstanceUrl(dbCtx);
+    const wheelUrl    = await resolveWheelUrl(instanceUrl);
+
+    const result = await extractFile(
+      name,
+      base64,
+      wheelUrl,
+      (msg) => setState({ status: 'loading', msg }),
+    );
+
+    setState({ status: 'loading', msg: 'Saving…' });
+
+    // Copy original file to permanent storage (keeps original bytes for future re-extraction)
+    const ext     = name.includes('.') ? name.slice(name.lastIndexOf('.')) : '';
+    const origDir = `${FileSystem.documentDirectory}originals/`;
+    await FileSystem.makeDirectoryAsync(origDir, { intermediates: true });
+    const dest = `${origDir}${result.id}${ext}`;
+    await FileSystem.copyAsync({ from: uri, to: dest });
+
+    await insertActivity(dbCtx, {
+      id: result.id,
+      source_hash: result.sourceHash,
+      detail_json: JSON.stringify(result.detail),
+      timeseries_json: result.timeseries ? JSON.stringify(result.timeseries) : null,
+      geojson: result.geojson ? JSON.stringify(result.geojson) : null,
+      original_path: dest,
+      origin: 'local',
+    });
+
+    const d = result.detail as Record<string, unknown>;
+    setState({ status: 'done', title: (d.title as string) ?? result.id, id: result.id });
   }
 
   return (
@@ -85,7 +130,7 @@ export default function ImportScreen() {
       <Text style={styles.header}>Import</Text>
 
       <Text style={styles.body}>
-        Import a FIT, GPX, or TCX file to extract and store it locally.
+        Import a FIT, GPX, or TCX file — extracted on your device, nothing uploaded.
         You can also import a pre-extracted BAS <Text style={styles.code}>.json</Text> file directly.
       </Text>
 
@@ -94,10 +139,21 @@ export default function ImportScreen() {
         onPress={state.status !== 'loading' ? pickFile : undefined}
       >
         <Text style={styles.buttonText}>
-          {state.status === 'loading' ? 'Importing…' : '＋ Pick file'}
+          {state.status === 'loading' ? 'Working…' : '＋ Pick file'}
         </Text>
       </Pressable>
 
+      {state.status === 'loading' && (
+        <View style={styles.statusBox}>
+          <Text style={styles.statusMsg}>{state.msg}</Text>
+          {state.msg.startsWith('Load') && (
+            <Text style={styles.statusHint}>
+              First run downloads ~35 MB of the Python runtime. Subsequent runs are instant.
+            </Text>
+          )}
+        </View>
+      )}
+
       {state.status === 'done' && (
         <View style={styles.success}>
           <Text style={styles.successText}>✓ Imported: {state.title}</Text>
@@ -107,18 +163,21 @@ export default function ImportScreen() {
       {state.status === 'error' && (
         <View style={styles.error}>
           <Text style={styles.errorText}>{state.message}</Text>
+          <Pressable onPress={() => setState({ status: 'idle' })}>
+            <Text style={styles.errorRetry}>Try another file</Text>
+          </Pressable>
         </View>
       )}
 
       <View style={styles.divider} />
 
       <Text style={styles.sectionTitle}>Supported formats</Text>
-      {[
-        ['FIT', 'Garmin, Wahoo, Karoo native format'],
-        ['GPX', 'Most GPS devices and apps'],
-        ['TCX', 'Garmin Training Center'],
-        ['BAS JSON', 'Pre-extracted Bincio format'],
-      ].map(([fmt, desc]) => (
+      {([
+        ['FIT',      'Garmin, Wahoo, Karoo native format'],
+        ['GPX',      'Most GPS devices and apps'],
+        ['TCX',      'Garmin Training Center'],
+        ['BAS JSON', 'Pre-extracted Bincio format (instant)'],
+      ] as [string, string][]).map(([fmt, desc]) => (
         <View key={fmt} style={styles.formatRow}>
           <Text style={styles.formatName}>{fmt}</Text>
           <Text style={styles.formatDesc}>{desc}</Text>
@@ -127,41 +186,71 @@ export default function ImportScreen() {
 
       <View style={styles.notice}>
         <Text style={styles.noticeText}>
-          FIT/GPX/TCX extraction runs entirely on your device via the Bincio
-          extraction engine. No data is uploaded.
+          FIT/GPX/TCX extraction runs entirely on your device.
+          A Bincio instance must be reachable on first run to download the extraction engine (~35 MB, then cached).
         </Text>
       </View>
     </ScrollView>
   );
 }
 
+// ── Helpers ─────────────────────────────────────────────────────────────────
+
+async function getInstanceUrl(db: ReturnType<typeof useSQLiteContext>): Promise<string> {
+  const row = db.getFirstSync<{ value: string }>(
+    'SELECT value FROM settings WHERE key = ?',
+    ['instance_url'],
+  );
+  return (row?.value ?? '').replace(/\/$/, '');
+}
+
+async function resolveWheelUrl(instanceUrl: string): Promise<string> {
+  const base = instanceUrl || 'https://bincio.org';
+  try {
+    const resp = await fetch(`${base}/api/wheel/version`, { signal: AbortSignal.timeout(5000) });
+    if (resp.ok) {
+      const d = await resp.json() as { api_url?: string; url?: string };
+      const path = d.api_url ?? d.url ?? '/api/wheel/download';
+      return path.startsWith('http') ? path : `${base}${path}`;
+    }
+  } catch {}
+  return `${base}/api/wheel/download`;
+}
+
+// ── Styles ───────────────────────────────────────────────────────────────────
+
 const styles = StyleSheet.create({
   container: { flex: 1, backgroundColor: '#09090b' },
-  content: { padding: 16, paddingTop: 60, paddingBottom: 40 },
-  header: { color: '#fff', fontSize: 22, fontWeight: '700', marginBottom: 12 },
-  body: { color: '#a1a1aa', fontSize: 14, lineHeight: 20, marginBottom: 24 },
-  code: { color: '#60a5fa', fontFamily: 'monospace' },
+  content:   { padding: 16, paddingTop: 60, paddingBottom: 40 },
+  header:    { color: '#fff', fontSize: 22, fontWeight: '700', marginBottom: 12 },
+  body:      { color: '#a1a1aa', fontSize: 14, lineHeight: 20, marginBottom: 24 },
+  code:      { color: '#60a5fa', fontFamily: 'monospace' },
   button: {
     backgroundColor: '#2563eb', borderRadius: 10,
     paddingVertical: 14, alignItems: 'center', marginBottom: 16,
   },
   buttonDisabled: { opacity: 0.5 },
-  buttonText: { color: '#fff', fontWeight: '600', fontSize: 16 },
+  buttonText:     { color: '#fff', fontWeight: '600', fontSize: 16 },
+  statusBox: {
+    backgroundColor: '#18181b', borderRadius: 8, borderWidth: 1,
+    borderColor: '#27272a', padding: 14, marginBottom: 16, gap: 6,
+  },
+  statusMsg:  { color: '#60a5fa', fontSize: 14, textAlign: 'center' },
+  statusHint: { color: '#52525b', fontSize: 12, textAlign: 'center', lineHeight: 16 },
   success: {
-    backgroundColor: '#14532d', borderRadius: 8,
-    padding: 12, marginBottom: 16,
+    backgroundColor: '#14532d', borderRadius: 8, padding: 12, marginBottom: 16,
   },
   successText: { color: '#86efac', fontSize: 14 },
   error: {
-    backgroundColor: '#450a0a', borderRadius: 8,
-    padding: 12, marginBottom: 16,
+    backgroundColor: '#450a0a', borderRadius: 8, padding: 12, marginBottom: 16, gap: 8,
   },
-  errorText: { color: '#fca5a5', fontSize: 14 },
-  divider: { height: 1, backgroundColor: '#27272a', marginVertical: 24 },
+  errorText:  { color: '#fca5a5', fontSize: 14 },
+  errorRetry: { color: '#71717a', fontSize: 13, textDecorationLine: 'underline' },
+  divider:      { height: 1, backgroundColor: '#27272a', marginVertical: 24 },
   sectionTitle: { color: '#a1a1aa', fontSize: 12, fontWeight: '600', marginBottom: 12, letterSpacing: 0.5 },
-  formatRow: { flexDirection: 'row', gap: 12, marginBottom: 10 },
-  formatName: { color: '#f4f4f5', fontSize: 13, fontWeight: '600', width: 72 },
-  formatDesc: { color: '#71717a', fontSize: 13, flex: 1 },
+  formatRow:    { flexDirection: 'row', gap: 12, marginBottom: 10 },
+  formatName:   { color: '#f4f4f5', fontSize: 13, fontWeight: '600', width: 72 },
+  formatDesc:   { color: '#71717a', fontSize: 13, flex: 1 },
   notice: {
     marginTop: 8, backgroundColor: '#18181b',
     borderRadius: 8, padding: 12, borderWidth: 1, borderColor: '#27272a',
diff --git a/mobile/app/_layout.tsx b/mobile/app/_layout.tsx
index a2c9de5..45b3f75 100644
--- a/mobile/app/_layout.tsx
+++ b/mobile/app/_layout.tsx
@@ -2,12 +2,18 @@ import { Stack } from 'expo-router';
 import { SQLiteProvider } from 'expo-sqlite';
 import { StatusBar } from 'expo-status-bar';
 import { migrateDb } from '@/db';
+import { PyodideWebView } from '@/extraction/PyodideWebView';
 
 export default function RootLayout() {
   return (
-    <SQLiteProvider databaseName="bincio.db" onInit={migrateDb}>
-      <StatusBar style="light" />
-      <Stack screenOptions={{ headerShown: false }} />
-    </SQLiteProvider>
+    <>
+      {/* Hidden WebView: starts loading Pyodide immediately so the runtime
+          is warm by the time the user opens the Import tab. */}
+      <PyodideWebView />
+      <SQLiteProvider databaseName="bincio.db" onInit={migrateDb}>
+        <StatusBar style="light" />
+        <Stack screenOptions={{ headerShown: false }} />
+      </SQLiteProvider>
+    </>
   );
 }
diff --git a/mobile/extraction/PyodideWebView.tsx b/mobile/extraction/PyodideWebView.tsx
new file mode 100644
index 0000000..f430e06
--- /dev/null
+++ b/mobile/extraction/PyodideWebView.tsx
@@ -0,0 +1,179 @@
+import { StyleSheet } from 'react-native';
+import WebView from 'react-native-webview';
+import { handleWebViewMessage, pyodideRef } from './extractActivity';
+
+const CDN = 'https://cdn.jsdelivr.net/pyodide/v0.26.4/full/';
+
+// Python snippets embedded as JSON strings to avoid any JS/TS escaping issues.
+const PY_INSTALL_PACKAGES = [
+  'import micropip',
+  'await micropip.install(["fitdecode", "gpxpy"])',
+].join('\n');
+
+const PY_INSTALL_WHEEL = [
+  'import micropip',
+  'await micropip.install(_blobUrl, deps=False)',
+].join('\n');
+
+const PY_EXTRACT = [
+  'import json, shutil',
+  'from pathlib import Path',
+  'from bincio.extract.parsers.factory import parse_file',
+  'from bincio.extract.metrics import compute',
+  'from bincio.extract.writer import make_activity_id, write_activity',
+  '',
+  'outdir = Path("/tmp/bincio_out")',
+  'if outdir.exists(): shutil.rmtree(outdir)',
+  'outdir.mkdir()',
+  '',
+  'activity = parse_file(Path("/tmp/" + _filename))',
+  'metrics  = compute(activity)',
+  'write_activity(activity, metrics, outdir, privacy="public", rdp_epsilon=0.0001)',
+  'act_id = make_activity_id(activity)',
+  '',
+  'detail_path  = outdir / "activities" / (act_id + ".json")',
+  'ts_path      = outdir / "activities" / (act_id + ".timeseries.json")',
+  'geojson_path = outdir / "activities" / (act_id + ".geojson")',
+  '',
+  'json.dumps({',
+  '  "id": act_id,',
+  '  "detail": json.loads(detail_path.read_text()),',
+  '  "timeseries": json.loads(ts_path.read_text()) if ts_path.exists() else None,',
+  '  "geojson": json.loads(geojson_path.read_text()) if geojson_path.exists() else None,',
+  '})',
+].join('\n');
+
+// JSON.stringify gives us safely-quoted JS string literals for embedding in HTML.
+const PYODIDE_HTML = `<!DOCTYPE html>
+<html><head><meta charset="utf-8"></head>
+<body>
+<script>
+var _PY_INSTALL_PACKAGES = ${JSON.stringify(PY_INSTALL_PACKAGES)};
+var _PY_INSTALL_WHEEL    = ${JSON.stringify(PY_INSTALL_WHEEL)};
+var _PY_EXTRACT          = ${JSON.stringify(PY_EXTRACT)};
+var _CDN = ${JSON.stringify(CDN)};
+
+function _post(m) { window.ReactNativeWebView.postMessage(JSON.stringify(m)); }
+
+var pyodide       = null;
+var packagesReady = false;
+var wheelReady    = false;
+var initError     = null;
+
+(async function init() {
+  try {
+    _post({ type: 'progress', msg: 'Loading Python runtime…' });
+    await new Promise(function(res, rej) {
+      var s = document.createElement('script');
+      s.src = _CDN + 'pyodide.js';
+      s.onload = res; s.onerror = rej;
+      document.head.appendChild(s);
+    });
+
+    pyodide = await loadPyodide({ indexURL: _CDN });
+
+    _post({ type: 'progress', msg: 'Loading packages…' });
+    await pyodide.loadPackage(['lxml', 'pyyaml', 'micropip']);
+
+    _post({ type: 'progress', msg: 'Installing fitdecode, gpxpy…' });
+    await pyodide.runPythonAsync(_PY_INSTALL_PACKAGES);
+
+    packagesReady = true;
+    _post({ type: 'pyodide_ready' });
+  } catch(e) {
+    initError = String(e);
+    _post({ type: 'init_error', message: initError });
+  }
+})();
+
+window._bincioExtract = async function(params) {
+  var reqId    = params.reqId;
+  var filename = params.filename;
+  var base64   = params.base64;
+  var wheelUrl = params.wheelUrl;
+
+  function post(m) { _post(Object.assign({}, m, { reqId: reqId })); }
+
+  try {
+    // Wait for base packages if still loading
+    if (!packagesReady && !initError) {
+      await new Promise(function(res, rej) {
+        var n = 0;
+        var id = setInterval(function() {
+          if (packagesReady)  { clearInterval(id); res(undefined); }
+          else if (initError) { clearInterval(id); rej(new Error(initError)); }
+          else if (++n > 300) { clearInterval(id); rej(new Error('Pyodide init timed out')); }
+        }, 200);
+      });
+    }
+    if (initError) throw new Error(initError);
+
+    // Install bincio wheel on first extraction (lazy: keeps startup fast)
+    if (!wheelReady) {
+      post({ type: 'progress', msg: 'Loading Bincio…' });
+      var resp = await fetch(wheelUrl);
+      if (!resp.ok) throw new Error('Failed to fetch Bincio wheel (' + resp.status + ')');
+      var wheelBlob = new Blob([await resp.arrayBuffer()]);
+      var blobUrl   = URL.createObjectURL(wheelBlob);
+      pyodide.globals.set('_blobUrl', blobUrl);
+      await pyodide.runPythonAsync(_PY_INSTALL_WHEEL);
+      URL.revokeObjectURL(blobUrl);
+      wheelReady = true;
+    }
+
+    post({ type: 'progress', msg: 'Extracting…' });
+
+    // Decode base64 file bytes and write to Pyodide's virtual filesystem
+    var bytes = Uint8Array.from(atob(base64), function(c) { return c.charCodeAt(0); });
+    pyodide.FS.writeFile('/tmp/' + filename, bytes);
+
+    // SHA-256 of original file bytes (replaces the stub source_hash)
+    var hashBuf    = await crypto.subtle.digest('SHA-256', bytes.buffer);
+    var sourceHash = Array.from(new Uint8Array(hashBuf))
+      .map(function(b) { return b.toString(16).padStart(2, '0'); })
+      .join('');
+
+    // Run the bincio extraction pipeline
+    pyodide.globals.set('_filename', filename);
+    var resultJson = await pyodide.runPythonAsync(_PY_EXTRACT);
+    var result     = JSON.parse(resultJson);
+
+    _post({
+      type: 'result',
+      reqId: reqId,
+      id: result.id,
+      detail: result.detail,
+      timeseries: result.timeseries,
+      geojson: result.geojson,
+      sourceHash: sourceHash,
+    });
+  } catch(e) {
+    _post({ type: 'error', reqId: reqId, message: e.message || String(e) });
+  }
+};
+</script>
+</body></html>`;
+
+export function PyodideWebView() {
+  return (
+    <WebView
+      ref={pyodideRef}
+      source={{ html: PYODIDE_HTML, baseUrl: '' }}
+      style={styles.hidden}
+      onMessage={handleWebViewMessage}
+      javaScriptEnabled
+      originWhitelist={['*']}
+    />
+  );
+}
+
+const styles = StyleSheet.create({
+  // Off-screen but still rendered — display:none / opacity:0 can suppress JS on some platforms.
+  hidden: {
+    position: 'absolute',
+    top: -2000,
+    left: 0,
+    width: 1,
+    height: 1,
+  },
+});
diff --git a/mobile/extraction/extractActivity.ts b/mobile/extraction/extractActivity.ts
new file mode 100644
index 0000000..5207f4d
--- /dev/null
+++ b/mobile/extraction/extractActivity.ts
@@ -0,0 +1,80 @@
+import { createRef } from 'react';
+import type WebView from 'react-native-webview';
+import type { WebViewMessageEvent } from 'react-native-webview';
+
+export type ExtractionResult = {
+  id: string;
+  detail: object;
+  timeseries: object | null;
+  geojson: object | null;
+  sourceHash: string;
+};
+
+type Pending = {
+  resolve: (r: ExtractionResult) => void;
+  reject: (e: Error) => void;
+  onStatus: (msg: string) => void;
+};
+
+export const pyodideRef = createRef<WebView>();
+
+const pending = new Map<string, Pending>();
+let reqCounter = 0;
+let isExtracting = false;
+
+export function handleWebViewMessage(e: WebViewMessageEvent): void {
+  let msg: Record<string, unknown>;
+  try { msg = JSON.parse(e.nativeEvent.data); } catch { return; }
+
+  const reqId = msg.reqId as string | undefined;
+  const p = reqId ? pending.get(reqId) : undefined;
+
+  switch (msg.type) {
+    case 'result':
+      if (p) {
+        pending.delete(reqId!);
+        p.resolve({
+          id: msg.id as string,
+          detail: msg.detail as object,
+          timeseries: (msg.timeseries as object | null) ?? null,
+          geojson: (msg.geojson as object | null) ?? null,
+          sourceHash: msg.sourceHash as string,
+        });
+      }
+      break;
+    case 'error':
+      if (p) {
+        pending.delete(reqId!);
+        p.reject(new Error(msg.message as string));
+      }
+      break;
+    case 'progress':
+      p?.onStatus(msg.msg as string);
+      break;
+  }
+}
+
+export function extractFile(
+  filename: string,
+  base64: string,
+  wheelUrl: string,
+  onStatus: (msg: string) => void = () => {},
+): Promise<ExtractionResult> {
+  if (isExtracting) return Promise.reject(new Error('Another extraction is already in progress'));
+
+  const webview = pyodideRef.current;
+  if (!webview) return Promise.reject(new Error('Extraction engine not ready — restart the app'));
+
+  isExtracting = true;
+  const reqId = String(++reqCounter);
+  const args = JSON.stringify({ reqId, filename, base64, wheelUrl });
+
+  return new Promise<ExtractionResult>((resolve, reject) => {
+    pending.set(reqId, {
+      resolve: (r) => { isExtracting = false; resolve(r); },
+      reject: (e) => { isExtracting = false; reject(e); },
+      onStatus,
+    });
+    webview.injectJavaScript(`window._bincioExtract(${args}); true;`);
+  });
+}