diff --git a/index.js b/index.js
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+import OpenAI from 'openai';
+
+const TTL_MS = 20 * 60 * 1000;
+const BATCH_MS = 60;
+const BATCH_BYTES = 2048;
+// SNAPSHOT_MIN_MS is no longer needed as we removed throttled saving.
+
+// Heartbeat configuration: run every 4s while streaming to prevent eviction.
+const HB_INTERVAL_MS = 4000;
+const MAX_RUN_MS = 15 * 60 * 1000;
+
+const CORS_HEADERS = {
+  'Access-Control-Allow-Origin': '*',
+  'Access-Control-Allow-Methods': 'GET, OPTIONS',
+  'Access-Control-Allow-Headers': 'Content-Type, Authorization',
+  'Access-Control-Max-Age': '86400',
+};
+
+const withCORS = (resp) => {
+  const headers = new Headers(resp.headers);
+  Object.entries(CORS_HEADERS).forEach(([k, v]) => headers.set(k, v));
+  return new Response(resp.body, { ...resp, headers });
+};
+
+export default {
+  async fetch(req, env) {
+    const url = new URL(req.url);
+    const method = req.method.toUpperCase();
+
+    if (method === 'OPTIONS') {
+      return new Response(null, { status: 204, headers: CORS_HEADERS });
+    }
+
+    if (url.pathname === '/ws') {
+      const isGet = method === 'GET';
+      const isWs = req.headers.get('Upgrade') === 'websocket';
+      if (!isGet && !isWs) {
+        return withCORS(new Response('method not allowed', { status: 405 }));
+      }
+
+      const rawUid = url.searchParams.get('uid') || 'anon';
+      const uid = String(rawUid).slice(0, 64).replace(/[^a-zA-Z0-9_-]/g, '') || 'anon';
+      const id = env.MY_DURABLE_OBJECT.idFromName(uid);
+      const stub = env.MY_DURABLE_OBJECT.get(id);
+      
+      const resp = await stub.fetch(req);
+      return isWs ? resp : withCORS(resp);
+    }
+
+    return withCORS(new Response('not found', { status: 404 }));
+  }
+}
+
+export class MyDurableObject {
+  constructor(state, env) {
+    this.state = state;
+    this.env = env;
+    this.sockets = new Set();
+    this.reset();
+  }
+
+  reset() {
+    this.rid = null;
+    this.buffer = [];
+    this.seq = -1;
+    this.phase = 'idle';
+    this.error = null;
+    this.controller = null;
+    this.oaStream = null;
+    this.pending = '';
+    this.flushTimer = null;
+    this.lastSavedAt = 0;
+    this.lastFlushedAt = 0;
+    this.hbActive = false;
+    this.age = 0;
+  }
+
+  corsJSON(obj, status = 200) {
+    return new Response(JSON.stringify(obj), {
+      status,
+      headers: { 'Content-Type': 'application/json', 'Cache-Control': 'no-store', ...CORS_HEADERS }
+    });
+  }
+
+  send(ws, obj) {
+    try { ws.send(JSON.stringify(obj)); } catch {}
+  }
+
+  bcast(obj) {
+    const message = JSON.stringify(obj);
+    this.sockets.forEach(ws => { try { ws.send(message); } catch {} });
+  }
+
+  async restoreIfCold() {
+    if (this.rid) return;
+    
+    const snap = await this.state.storage.get('run').catch(() => null);
+    if (!snap || (Date.now() - (snap.savedAt || 0) >= TTL_MS)) {
+      if (snap) await this.state.storage.delete('run').catch(() => {});
+      return;
+    }
+
+    this.rid = snap.rid || null;
+    this.buffer = Array.isArray(snap.buffer) ? snap.buffer : [];
+    this.seq = Number.isFinite(+snap.seq) ? +snap.seq : -1;
+    this.age = snap.age || 0;
+    this.phase = snap.phase || 'done';
+    this.error = snap.error || null;
+    this.pending = '';
+
+    if (this.phase === 'running') {
+      this.phase = 'evicted';
+      this.error = 'The run was interrupted due to system eviction.';
+      this.saveSnapshot(); // Persist the final 'evicted' state.
+      this.stopHeartbeat().catch(() => {});
+    }
+  }
+
+  saveSnapshot() {
+    this.lastSavedAt = Date.now();
+    const data = {
+      rid: this.rid,
+      buffer: this.buffer,
+      seq: this.seq,
+      age: this.age,
+      phase: this.phase,
+      error: this.error,
+      savedAt: this.lastSavedAt,
+    };
+    this.state.storage.put('run', data).catch(() => {});
+  }
+
+  replay(ws, after) {
+    this.buffer.forEach(it => {
+      if (it.seq > after) this.send(ws, { type: 'delta', seq: it.seq, text: it.text });
+    });
+    
+    if (this.phase === 'done') {
+      this.send(ws, { type: 'done' });
+    } else if (this.phase === 'error' || this.phase === 'evicted') {
+      this.send(ws, { type: 'err', message: this.error || 'The run was terminated unexpectedly.' });
+    }
+  }
+
+  flush(force = false) {
+    if (this.flushTimer) {
+      clearTimeout(this.flushTimer);
+      this.flushTimer = null;
+    }
+    if (this.pending) {
+      this.buffer.push({ seq: ++this.seq, text: this.pending });
+      this.bcast({ type: 'delta', seq: this.seq, text: this.pending });
+      this.pending = '';
+      this.lastFlushedAt = Date.now();
+    }
+    // Only save the snapshot if explicitly forced (i.e., at the end of a run).
+    if (force) this.saveSnapshot();
+  }
+
+  queueDelta(text) {
+    if (!text) return;
+    this.pending += text;
+    if (this.pending.length >= BATCH_BYTES) {
+      this.flush(false);
+    } else if (!this.flushTimer) {
+      this.flushTimer = setTimeout(() => this.flush(false), BATCH_MS);
+    }
+  }
+
+  async fetch(req) {
+    if (req.method === 'OPTIONS') {
+      return new Response(null, { status: 204, headers: CORS_HEADERS });
+    }
+    if (req.headers.get('Upgrade') === 'websocket') {
+      const [client, server] = Object.values(new WebSocketPair());
+      server.accept();
+      this.sockets.add(server);
+      server.addEventListener('close', () => this.sockets.delete(server));
+      server.addEventListener('message', e => this.state.waitUntil(this.onMessage(server, e)));
+      return new Response(null, { status: 101, webSocket: client });
+    }
+    if (req.method === 'GET') {
+      await this.restoreIfCold();
+      const text = this.buffer.map(it => it.text).join('') + this.pending;
+      const isTerminal = ['done', 'error', 'evicted'].includes(this.phase);
+      const isError = ['error', 'evicted'].includes(this.phase);
+
+      return this.corsJSON({
+        rid: this.rid,
+        seq: this.seq,
+        phase: this.phase,
+        done: isTerminal,
+        error: isError ? (this.error || 'The run was terminated unexpectedly.') : null,
+        text,
+      });
+    }
+    return this.corsJSON({ error: 'not allowed' }, 405);
+  }
+
+  async onMessage(ws, evt) {
+    await this.restoreIfCold();
+    let msg;
+    try {
+      msg = JSON.parse(String(evt.data || ''));
+    } catch {
+      return this.send(ws, { type: 'err', message: 'bad_json' });
+    }
+
+    if (msg.type === 'stop') {
+      if (msg.rid && msg.rid === this.rid) this.stop();
+      return;
+    }
+
+    if (msg.type !== 'begin') return this.send(ws, { type: 'err', message: 'bad_type' });
+
+    const { rid, apiKey, or_body, model, messages, after, provider } = msg;
+    const body = or_body || (model && Array.isArray(messages) ? { model, messages, stream: true } : null);
+
+    if (!rid || !apiKey || !body || !Array.isArray(body.messages) || body.messages.length === 0) {
+      return this.send(ws, { type: 'err', message: 'missing_fields' });
+    }
+    if (this.phase === 'running' && rid !== this.rid) {
+      return this.send(ws, { type: 'err', message: 'busy' });
+    }
+    if (rid === this.rid && this.phase !== 'idle') {
+      return this.replay(ws, Number.isFinite(+after) ? +after : -1);
+    }
+
+    this.reset();
+    this.rid = rid;
+    this.phase = 'running';
+    this.controller = new AbortController();
+    this.saveSnapshot(); // Save the initial state of the run.
+
+    this.state.waitUntil(this.startHeartbeat());
+    this.state.waitUntil(this.stream({ apiKey, body, provider: provider || 'openrouter' }));
+  }
+
+  async stream({ apiKey, body, provider }) {
+    try {
+      if (provider === 'openai') {
+        await this.streamOpenAI({ apiKey, body });
+      } else {
+        await this.streamOpenRouter({ apiKey, body });
+      }
+      if (this.phase === 'running') this.stop();
+    } catch (e) {
+      if (this.phase === 'running') {
+        const msg = String(e?.message || 'stream_failed');
+        if (!((e && e.name === 'AbortError') || /abort/i.test(msg))) {
+          this.fail(msg);
+        }
+      }
+    }
+  }
+
+  isMultimodalMessage(m) {
+    if (!m || !Array.isArray(m.content)) return false;
+    return m.content.some(p => p?.type && p.type !== 'text' && p.type !== 'input_text');
+  }
+
+  extractTextFromMessage(m) {
+    if (!m) return '';
+    if (typeof m.content === 'string') return String(m.content);
+    if (!Array.isArray(m.content)) return '';
+    return m.content
+      .filter(p => p && (p.type === 'text' || p.type === 'input_text'))
+      .map(p => String(p.type === 'text' ? (p.text ?? p.content ?? '') : (p.text ?? '')))
+      .join('');
+  }
+
+  mapContentPartToResponses(part) {
+    const type = part?.type || 'text';
+    if (type === 'image_url' || type === 'input_image') {
+      const url = part?.image_url?.url || part?.image_url || '';
+      return url ? { type: 'input_image', image_url: String(url) } : null;
+    }
+    if (type === 'text' || type === 'input_text') {
+      const text = type === 'text' ? (part.text ?? part.content ?? '') : (part.text ?? '');
+      return { type: 'input_text', text: String(text) };
+    }
+    return { type: 'input_text', text: `[${type}:${part?.file?.filename || 'file'}]` };
+  }
+
+  buildInputForResponses(messages) {
+    if (!Array.isArray(messages) || messages.length === 0) return '';
+    const isMulti = messages.some(m => this.isMultimodalMessage(m));
+
+    if (!isMulti) {
+      if (messages.length === 1) return this.extractTextFromMessage(messages[0]);
+      return messages.map(m => ({ role: m.role, content: this.extractTextFromMessage(m) }));
+    }
+    return messages.map(m => {
+      let content = [{ type: 'input_text', text: String(m.content || '') }];
+      if (Array.isArray(m.content)) {
+        content = m.content.map(p => this.mapContentPartToResponses(p)).filter(Boolean);
+      }
+      return { role: m.role, content };
+    });
+  }
+
+  async streamOpenAI({ apiKey, body }) {
+    const client = new OpenAI({ apiKey });
+    const params = {
+      model: body.model,
+      input: this.buildInputForResponses(body.messages || []),
+      temperature: body.temperature,
+      stream: true,
+    };
+    if (Number.isFinite(+body.max_tokens) && +body.max_tokens > 0) {
+      params.max_output_tokens = +body.max_tokens;
+    }
+    if (body.reasoning?.effort) params.reasoning = { effort: body.reasoning.effort };
+    if (body.verbosity) params.verbosity = body.verbosity;
+
+    this.oaStream = await client.responses.stream(params);
+    try {
+      for await (const event of this.oaStream) {
+        if (this.phase !== 'running') break;
+        if (event.type.endsWith('.delta') && event.delta) this.queueDelta(event.delta);
+      }
+    } finally {
+      try { this.oaStream?.controller?.abort(); } catch {}
+      this.oaStream = null;
+    }
+  }
+
+  async streamOpenRouter({ apiKey, body }) {
+    const client = new OpenAI({ apiKey, baseURL: 'https://openrouter.ai/api/v1' });
+    const stream = await client.chat.completions.create(
+      { ...body, stream: true },
+      { signal: this.controller.signal }
+    );
+    for await (const chunk of stream) {
+      if (this.phase !== 'running') break;
+      const delta = chunk?.choices?.[0]?.delta?.content ?? '';
+      if (delta) this.queueDelta(delta);
+    }
+  }
+
+  stop() {
+    if (this.phase !== 'running') return;
+    this.flush(true); // Flush and force a final save.
+    this.phase = 'done';
+    this.error = null;
+    try { this.controller?.abort(); } catch {}
+    try { this.oaStream?.controller?.abort(); } catch {}
+    this.saveSnapshot(); // Explicitly save final 'done' state.
+    this.bcast({ type: 'done' });
+    this.state.waitUntil(this.stopHeartbeat());
+  }
+
+  fail(message) {
+    if (this.phase === 'error') return;
+    this.flush(true); // Flush and force a final save.
+    this.phase = 'error';
+    this.error = String(message || 'stream_failed');
+    try { this.controller?.abort(); } catch {}
+    try { this.oaStream?.controller?.abort(); } catch {}
+    this.saveSnapshot(); // Explicitly save final 'error' state.
+    this.bcast({ type: 'err', message: this.error });
+    this.state.waitUntil(this.stopHeartbeat());
+  }
+
+  async startHeartbeat() {
+    if (this.hbActive || this.phase !== 'running') return;
+    this.hbActive = true;
+    try {
+      await this.state.storage.setAlarm(Date.now() + HB_INTERVAL_MS);
+    } catch {}
+  }
+
+  async stopHeartbeat() {
+    this.hbActive = false;
+    try {
+      await this.state.storage.setAlarm(null);
+    } catch {}
+  }
+
+  async Heart() {
+    if (this.phase !== 'running' || !this.hbActive) return await this.stopHeartbeat();
+    if (++this.age * HB_INTERVAL_MS >= MAX_RUN_MS) return this.fail('Run timed out after 15 minutes.');
+    try { await this.state.storage.setAlarm(Date.now() + HB_INTERVAL_MS); } catch {}
+  }
+
+  async alarm() {
+    await this.restoreIfCold();
+    await this.Heart();
+  }
+}