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fix(daemon): retry WS handshake up to 3× with 5s back-off before raising #384

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fix(daemon): retry WS handshake up to 3× with 5s back-off before raising #384

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29 changes: 23 additions & 6 deletions src/browser_harness/daemon.py
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Original file line number Diff line number Diff line change
Expand Up @@ -117,7 +117,7 @@ def get_ws_url():
except (OSError, KeyError, ValueError):
time.sleep(1)
raise RuntimeError(
f"Chrome's remote-debugging page is open, but DevTools is not live yet on 127.0.0.1:{port} — if Chrome opened a profile picker, choose your normal profile first, then tick the checkbox and click Allow if shown"
f"Chrome's remote-debugging page is open, but DevTools is not live yet on 127.0.0.1:{port} (profile: {base}) — if Chrome opened a profile picker, choose your normal profile first, then tick the checkbox and click Allow if shown"
)
for probe_port in (9222, 9223):
try:
Expand Down Expand Up @@ -185,16 +185,33 @@ async def start(self):
url = get_ws_url()
log(f"connecting to {url}")
self.cdp = CDPClient(url)
try:
await self.cdp.start()
except Exception as e:
_ATTEMPTS = 3
_RETRY_DELAY = 5 # seconds between WS handshake retries
last_exc = None
for attempt in range(_ATTEMPTS):
if attempt > 0:
await asyncio.sleep(_RETRY_DELAY)
try:
url = get_ws_url()
except Exception:
pass # reuse previous URL if refresh fails
log(f"retry {attempt}: connecting to {url}")
self.cdp = CDPClient(url)
try:
await self.cdp.start()
break
except Exception as e:
last_exc = e
if attempt < _ATTEMPTS - 1:
log(f"handshake attempt {attempt + 1} failed ({e}); retrying in {_RETRY_DELAY}s")
else:
if os.environ.get("BU_CDP_WS"):
raise RuntimeError(
f"CDP WS handshake failed: {e} -- remote browser WebSocket connection failed. "
f"CDP WS handshake failed: {last_exc} -- remote browser WebSocket connection failed. "
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@cubic-dev-ai cubic-dev-ai Bot May 22, 2026 •
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P2: Remote handshake error branch omits the WS URL, leaving the error-context guarantee only partially implemented. The local branch includes ({url}) but the remote branch does not, despite the PR stating WS URL should be included on all raise paths.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At src/browser_harness/daemon.py, line 210:

<comment>Remote handshake error branch omits the WS URL, leaving the error-context guarantee only partially implemented. The local branch includes `({url})` but the remote branch does not, despite the PR stating WS URL should be included on all raise paths.</comment>

<file context>
@@ -185,16 +185,33 @@ async def start(self):
             if os.environ.get("BU_CDP_WS"):
                 raise RuntimeError(
-                    f"CDP WS handshake failed: {e} -- remote browser WebSocket connection failed. "
+                    f"CDP WS handshake failed: {last_exc} -- remote browser WebSocket connection failed. "
                     "This can happen when network policy blocks the connection, the WS URL is wrong or expired, or the remote endpoint is down. "
                     "If you use Browser Use cloud, verify BROWSER_USE_API_KEY and get a fresh URL via start_remote_daemon()."
</file context>
Suggested change
f"CDP WS handshake failed: {last_exc} -- remote browser WebSocket connection failed. "
f"CDP WS handshake failed ({url}): {last_exc} -- remote browser WebSocket connection failed. "
Fix with Cubic

"This can happen when network policy blocks the connection, the WS URL is wrong or expired, or the remote endpoint is down. "
"If you use Browser Use cloud, verify BROWSER_USE_API_KEY and get a fresh URL via start_remote_daemon()."
)
raise RuntimeError(f"CDP WS handshake failed: {e} -- click Allow in Chrome if prompted, then retry")
raise RuntimeError(f"CDP WS handshake failed ({url}): {last_exc} -- click Allow in Chrome if prompted, then retry")
await self.attach_first_page()
orig = self.cdp._event_registry.handle_event
mark_js = "if(!document.title.startsWith('\U0001F7E2'))document.title='\U0001F7E2 '+document.title"
Expand Down