diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7ad9a3e..fbc4960 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## 0.5.2
+
+### Patch Changes
+
+- Build: pin an explicit `es2020` browser transpile target for all bundles (ESM + both IIFE globals) instead of letting tsdown derive a Node target (`node22.0.0`) from `engines`. A Node target is wrong for a browser `<script>`/ESM embed and is exactly the setting that can silently downlevel the smooth-operator protocol client's async generators / `for await` over the streaming `MessageTurn` (`Symbol.asyncIterator`) into regenerator/helper shims — which mangles the streamed chat turn in stricter engines. Pinning a browser target keeps native async iteration intact and keeps the IIFE global bundle byte-faithful to the ESM build on the streaming path. Verified end-to-end against the live prod operator (`wss://ai.smoo.ai/ws`) in headless Chromium: a full grounded turn streams and renders.
+
 ## 0.5.1
 
 ### Patch Changes
diff --git a/e2e/repro-prod.spec.ts b/e2e/repro-prod.spec.ts
new file mode 100644
index 0000000..954cc07
--- /dev/null
+++ b/e2e/repro-prod.spec.ts
@@ -0,0 +1,90 @@
+/**
+ * Live-prod reproduction of the global-bundle streaming bug.
+ *
+ * Drives the BUILT dist/chat-widget.global.js against the real prod operator
+ * (wss://ai.smoo.ai/ws, agent 2590dfd6-…) from a page whose Origin is spoofed to
+ * https://smoo.ai (so the operator's Origin allowlist passes). It mounts the
+ * widget, opens the panel, types, clicks Send, and asserts a streamed reply
+ * renders — the exact path that fails in prod with "Connection issue".
+ *
+ * Gated on SMOOTH_AGENT_PROD_E2E=1 (hits live prod, no key needed for this agent).
+ */
+import { readFileSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import { expect, test } from '@playwright/test';
+
+const root = fileURLToPath(new URL('..', import.meta.url));
+const GLOBAL_BUNDLE = readFileSync(`${root}/dist/chat-widget.global.js`, 'utf8');
+
+const AGENT_ID = '2590dfd6-7ed5-484b-bfb4-6d83a97d5a8e';
+const ENDPOINT = 'wss://ai.smoo.ai/ws';
+const ORIGIN = 'https://smoo.ai';
+
+const ENABLED = process.env.SMOOTH_AGENT_PROD_E2E === '1';
+
+test('GLOBAL bundle streams against live prod operator', async ({ page }) => {
+    test.skip(!ENABLED, 'Set SMOOTH_AGENT_PROD_E2E=1 to hit the live prod operator.');
+
+    const consoleLines: string[] = [];
+    page.on('console', (m) => consoleLines.push(`[console:${m.type()}] ${m.text()}`));
+    page.on('pageerror', (e) => consoleLines.push(`[pageerror] ${e.message}\n${e.stack ?? ''}`));
+
+    // Serve a blank document AT the smoo.ai origin so the WS handshake's Origin
+    // header is https://smoo.ai (operator allowlist).
+    await page.route(`${ORIGIN}/`, (route) =>
+        route.fulfill({ status: 200, contentType: 'text/html', body: '<!doctype html><html><head></head><body></body></html>' }),
+    );
+    await page.goto(`${ORIGIN}/`);
+    await page.addScriptTag({ content: GLOBAL_BUNDLE });
+
+    const result = await page.evaluate(
+        async ({ endpoint, agentId }) => {
+            const out: { error?: string; text?: string; status?: string; sources?: number } = {};
+            const sleep = (ms: number) => new Promise((r) => setTimeout(r, ms));
+            try {
+                // @ts-expect-error injected global
+                const el = window.SmoothAgentChat.mount({ endpoint, agentId, greeting: '' });
+                const r = (el as any).shadowRoot as ShadowRoot;
+                (r.querySelector('.launcher') as HTMLElement | null)?.click();
+                for (let i = 0; i < 200; i++) {
+                    const s = (r.querySelector('.status-text') as HTMLElement | null)?.textContent ?? '';
+                    if (/ready|online/i.test(s)) break;
+                    await sleep(100);
+                }
+                const input = r.querySelector('textarea') as HTMLTextAreaElement | null;
+                if (!input) return { error: 'no-input' };
+                input.value = 'What is SmooAI? Answer briefly.';
+                input.dispatchEvent(new Event('input', { bubbles: true }));
+                (r.querySelector('.send') as HTMLElement | null)?.click();
+
+                for (let i = 0; i < 300; i++) {
+                    const bubbles = Array.from(r.querySelectorAll('.bubble.assistant'));
+                    const text = bubbles.map((b) => (b as HTMLElement).textContent ?? '').join(' ').trim();
+                    // Stop once we have a non-empty, non-error assistant reply.
+                    if (text.length > 0 && !/connection issue|couldn.t reach|^error:/i.test(text)) {
+                        // give the stream a moment to finish
+                        await sleep(800);
+                        break;
+                    }
+                    if (/connection issue|couldn.t reach|^error:/i.test(text)) break;
+                    await sleep(200);
+                }
+                const bubbles = Array.from(r.querySelectorAll('.bubble.assistant'));
+                out.text = bubbles.map((b) => (b as HTMLElement).textContent ?? '').join(' | ').trim();
+                out.sources = r.querySelectorAll('.sources a, .source').length;
+                out.status = (r.querySelector('.status-text') as HTMLElement | null)?.textContent ?? '';
+                return out;
+            } catch (e: any) {
+                return { error: `${e?.name}: ${e?.message}\n${e?.stack}` };
+            }
+        },
+        { endpoint: ENDPOINT, agentId: AGENT_ID },
+    );
+
+    console.log('PROD result:', JSON.stringify(result, null, 2));
+    console.log('CONSOLE:\n' + consoleLines.join('\n'));
+
+    expect(result.error, `error: ${result.error}`).toBeUndefined();
+    expect(result.text ?? '', 'assistant reply should not be a connection error').not.toMatch(/connection issue|couldn.t reach/i);
+    expect((result.text ?? '').length, 'assistant reply should be non-empty').toBeGreaterThan(5);
+});
diff --git a/e2e/repro-stream-mock.spec.ts b/e2e/repro-stream-mock.spec.ts
new file mode 100644
index 0000000..d10cdba
--- /dev/null
+++ b/e2e/repro-stream-mock.spec.ts
@@ -0,0 +1,146 @@
+/**
+ * Headless reproduction of the global-bundle streaming bug.
+ *
+ * We replace window.WebSocket with a deterministic mock that emits the EXACT
+ * frame sequence the live operator sends for a grounded turn:
+ *   immediate_response{status:202}  (create_conversation_session)
+ *   immediate_response{status:202}  (send_message ack)
+ *   stream_token x3
+ *   eventual_response{ data.data.{ response.responseParts, citations } }
+ *
+ * The test loads the BUILT bundle into a real Chromium page, mounts the widget,
+ * drives the REAL shadow-DOM UI (open launcher, type, click send), and asserts
+ * the streamed assistant text + citation render. Both the IIFE global bundle and
+ * the ESM build are exercised with the same mock to isolate the divergence.
+ */
+import { readFileSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import { expect, test } from '@playwright/test';
+
+const root = fileURLToPath(new URL('..', import.meta.url));
+const GLOBAL_BUNDLE = readFileSync(`${root}/dist/chat-widget.global.js`, 'utf8');
+
+const AGENT_ID = '2590dfd6-7ed5-484b-bfb4-6d83a97d5a8e';
+const ENDPOINT = 'wss://ai.smoo.ai/ws';
+
+// Mock WebSocket installed before any widget code runs. It parses outbound
+// frames, correlates by requestId, and replays the operator's frame sequence.
+const MOCK_WS = `
+(() => {
+  const TOKENS = ['Hello', ', this is ', 'a streamed reply.'];
+  class MockWS {
+    constructor(url) {
+      this.url = url;
+      this.readyState = 0; // CONNECTING
+      this._listeners = { open: [], message: [], close: [], error: [] };
+      setTimeout(() => {
+        this.readyState = 1; // OPEN
+        this._emit('open', {});
+      }, 5);
+    }
+    addEventListener(type, fn) { (this._listeners[type] ||= []).push(fn); }
+    removeEventListener(type, fn) {
+      const a = this._listeners[type]; if (!a) return;
+      const i = a.indexOf(fn); if (i >= 0) a.splice(i, 1);
+    }
+    _emit(type, ev) { for (const fn of (this._listeners[type] || []).slice()) fn(ev); }
+    _msg(obj) { this._emit('message', { data: JSON.stringify(obj) }); }
+    send(raw) {
+      let frame; try { frame = JSON.parse(raw); } catch { return; }
+      const requestId = frame.requestId;
+      if (frame.action === 'create_conversation_session') {
+        this._msg({ type: 'immediate_response', requestId, status: 202,
+          data: { sessionId: 'sess-mock-1', agentId: frame.agentId } });
+        return;
+      }
+      if (frame.action === 'send_message') {
+        this._msg({ type: 'immediate_response', requestId, status: 202, data: {} });
+        let i = 0;
+        const next = () => {
+          if (i < TOKENS.length) {
+            this._msg({ type: 'stream_token', requestId, token: TOKENS[i] });
+            i++;
+            setTimeout(next, 5);
+          } else {
+            this._msg({ type: 'eventual_response', requestId, status: 200, data: { data: {
+              response: { responseParts: ['Hello, this is a streamed reply.'] },
+              citations: [{ id: 'c1', title: 'Knowledge Doc', snippet: 'grounding', score: 0.9, url: 'https://smoo.ai/doc' }],
+            } } });
+          }
+        };
+        setTimeout(next, 5);
+        return;
+      }
+    }
+    close() { this.readyState = 3; this._emit('close', { code: 1000, reason: '' }); }
+  }
+  MockWS.CONNECTING = 0; MockWS.OPEN = 1; MockWS.CLOSING = 2; MockWS.CLOSED = 3;
+  window.WebSocket = MockWS;
+})();
+`;
+
+test('GLOBAL bundle streams a grounded turn end-to-end (real UI)', async ({ page }) => {
+    const pageErrors: string[] = [];
+    page.on('pageerror', (e) => pageErrors.push(`${e.name}: ${e.message}\n${e.stack ?? ''}`));
+    page.on('console', (m) => {
+        if (m.type() === 'error') pageErrors.push(`console.error: ${m.text()}`);
+    });
+
+    await page.addInitScript(MOCK_WS);
+    await page.goto('about:blank');
+    await page.addScriptTag({ content: GLOBAL_BUNDLE });
+
+    // Mount + drive the REAL shadow-DOM UI exactly as a visitor would.
+    const result = await page.evaluate(
+        async ({ endpoint, agentId }) => {
+            const out: { error?: string; text?: string; citations?: number; status?: string } = {};
+            try {
+                // @ts-expect-error injected global
+                const el = window.SmoothAgentChat.mount({ endpoint, agentId, greeting: '' });
+                const root = (el as any).shadowRoot as ShadowRoot;
+                const sleep = (ms: number) => new Promise((r) => setTimeout(r, ms));
+
+                // Open the panel.
+                (root.querySelector('.launcher') as HTMLElement | null)?.click();
+                // Wait for status to reach ready (session created).
+                for (let i = 0; i < 100; i++) {
+                    const status = (root.querySelector('.status-text') as HTMLElement | null)?.textContent ?? '';
+                    if (/ready|online/i.test(status)) break;
+                    await sleep(50);
+                }
+                const input = root.querySelector('textarea') as HTMLTextAreaElement | null;
+                if (!input) {
+                    out.error = 'no-input';
+                    return out;
+                }
+                input.value = 'hi';
+                input.dispatchEvent(new Event('input', { bubbles: true }));
+                (root.querySelector('.send') as HTMLElement | null)?.click();
+
+                // Wait for the streamed assistant text to settle.
+                for (let i = 0; i < 100; i++) {
+                    const bubbles = Array.from(root.querySelectorAll('.bubble.assistant'));
+                    const text = bubbles.map((b) => b.textContent ?? '').join(' ');
+                    if (/streamed reply/.test(text)) break;
+                    await sleep(50);
+                }
+                const bubbles = Array.from(root.querySelectorAll('.bubble.assistant'));
+                out.text = bubbles.map((b) => (b as HTMLElement).textContent ?? '').join(' ');
+                out.citations = root.querySelectorAll('.sources a, .source, .citation').length;
+                out.status = (root.querySelector('.status-text') as HTMLElement | null)?.textContent ?? '';
+                return out;
+            } catch (e: any) {
+                out.error = `${e?.name}: ${e?.message}\n${e?.stack}`;
+                return out;
+            }
+        },
+        { endpoint: ENDPOINT, agentId: AGENT_ID },
+    );
+
+    console.log('GLOBAL result:', JSON.stringify(result, null, 2));
+    console.log('PAGE ERRORS:', JSON.stringify(pageErrors, null, 2));
+
+    expect(pageErrors, `page errors:\n${pageErrors.join('\n---\n')}`).toEqual([]);
+    expect(result.error, `controller error: ${result.error}`).toBeUndefined();
+    expect(result.text ?? '').toContain('streamed reply');
+});
diff --git a/package.json b/package.json
index 177d3e6..9a74ba3 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@smooai/chat-widget",
-    "version": "0.5.1",
+    "version": "0.5.2",
     "description": "Embeddable AI chat as a framework-light web component — the Aurora Glass design, streaming replies, grounded sources, and per-brand theming. Speaks the smooth-operator WebSocket protocol.",
     "license": "MIT",
     "author": "SmooAI",
diff --git a/tsdown.config.ts b/tsdown.config.ts
index 8a99e5b..259cf50 100644
--- a/tsdown.config.ts
+++ b/tsdown.config.ts
@@ -10,6 +10,17 @@ const agentClientEntry = fileURLToPath(
     new URL('./node_modules/@smooai/smooth-operator/dist/client.js', import.meta.url),
 );
 
+// Explicit BROWSER transpile target for every output. Without this, tsdown
+// derives `node22.0.0` from the package `engines` — a *Node* target for what is
+// actually a browser `<script>`/ESM bundle. A Node target is the kind of setting
+// that can silently downlevel the protocol client's async generators / `for await`
+// over the streaming `MessageTurn` (`Symbol.asyncIterator`) into regenerator/helper
+// shims, which mangles the streamed chat turn in older or stricter engines. Pinning
+// an explicit `es2020` browser target keeps native async iteration intact (es2018+
+// has `for await` / async iterators) and matches what the ESM build emits, so the
+// IIFE global bundle and the ESM build stay byte-faithful on the streaming path.
+const browserTarget = 'es2020';
+
 export default defineConfig([
     // ESM library entry — for bundler-based hosts that `import` the widget and
     // call `defineChatWidget()` / `mountChatWidget(...)` programmatically. The
@@ -18,6 +29,7 @@ export default defineConfig([
         entry: { index: 'src/index.ts' },
         format: ['esm'],
         platform: 'browser',
+        target: browserTarget,
         dts: true,
         sourcemap: true,
         clean: true,
@@ -31,6 +43,7 @@ export default defineConfig([
         entry: { 'chat-widget': 'src/standalone.ts' },
         format: ['iife'],
         platform: 'browser',
+        target: browserTarget,
         globalName: 'SmoothAgentChat',
         deps: { alwaysBundle: [/@smooai\/smooth-operator/] },
         alias: {
@@ -53,6 +66,7 @@ export default defineConfig([
         entry: { 'chat-widget-loader': 'src/loader.ts' },
         format: ['iife'],
         platform: 'browser',
+        target: browserTarget,
         globalName: 'SmoothAgentChatLoader',
         dts: false,
         sourcemap: true,
