playwright+MCP+idle+timeout

Not specified by the original author.

TL;DR

A headless browser launched by the server is closed after an hour without tool calls to save CPU; the next call then fails because there is no browser. Pass --idle-timeout (milliseconds) to raise it, or 0 to disable. Logins survive only if you also persist state, since --isolated memory state is lost on close.

The error

Target page, context or browser has been closed

Fix it

1. Add --idle-timeout to your MCP config args. For a 5-minute window:

   {
     "mcpServers": {
       "playwright": {
         "command": "npx",
         "args": ["@playwright/mcp@latest", "--idle-timeout=300000"]
       }
     }
   }

   Use 0 to disable the timeout entirely.

   • Expected: valid JSON.

2. Restart the client and run a long session.

   • Expected: the browser stays up across idle gaps up to your timeout.

3. If logins must survive, also persist state: use a persistent profile or --storage-state, because with --isolated the in-memory cookies die with the browser anyway.

   • Expected: re-login not needed after idle closes.

When to use

• Browser works, then after a long idle stretch the next tool call fails with browser-closed.
• Agent sessions span hours with gaps between browser actions.

When NOT to use

• Browser dies between rapid successive calls on 0.0.73 - that is the launchApp regression, pin 0.0.72.
• Browser never launches - check the install.

Compatibility

• @playwright/mcp with --idle-timeout support.

Root cause

An animating page costs CPU as long as the browser is open, and agent sessions last hours. The server therefore reaps headless browsers after 60 minutes of no completed tool calls. Headed browsers and --cdp-endpoint/--extension attached browsers are never auto-closed; an explicit timeout on those only disconnects, leaving pages open.

Edge cases

• The timer never fires mid-call; it only counts completed-call idle time.
• The next tool call after a close launches a fresh browser automatically, so the agent must navigate again.
• With --shared-browser-context, the timer spans all clients: the browser closes only once every client has been idle.

Playwright MCP documentation for the idle timeout: a headless browser launched by the server is closed after an hour without tool calls, with --idle-timeout setting the timeout in milliseconds (0 disables it). With --isolated, cookies and in-memory storage are lost on close, so a persistent profile or --storage-state is needed to keep logins.

Not specified by the original author.

TL;DR

The load balancer closed the connection without answering, usually because the backend was deregistered, the idle timeout fired, or the request hit a dead pool member. Check LB target health first, then align keep-alive and idle timeouts between Playwright and the LB. If the origin is healthy and the LB still empties responses, the LB config is the bug.

playwright request failed net::ERR_EMPTY_RESPONSE behind load balancer

Use this when

• The error appears only through the load balancer, never direct to origin.
• Failures cluster after idle periods or during deploys.
• The LB is AWS ALB/NLB, GCP, Cloudflare, or nginx/haproxy.

Not for this skill when

• Direct-to-origin requests also fail. That is the backend, not the balancer.
• The error is ERRCONNECTIONRESET. That is a reset, a different failure.

Steps

1. Check the LB target health: every backend should be healthy at the moment of failure. Verify: no targets flapping or draining during the failure window.
2. Compare idle timeouts: the LB's idle timeout must exceed the longest gap between requests on a reused connection. Verify: raising the LB idle timeout (e.g. ALB 60s default) stops the failures.
3. Disable connection reuse for the test: new Playwright context per batch. Verify: failures disappear, confirming stale pooled connections through the LB.
4. Check sticky sessions: if the app needs stickiness and the LB routes to a dead member, the response empties. Verify: stickiness settings match what the app expects.
5. During deploys, confirm connection draining is enabled with a drain timeout longer than in-flight requests. Verify: deploys stop producing empty responses.

Variant phrasings

ERREMPTYRESPONSE load balancer

The short search, same LB-first diagnosis.

playwright empty response alb

Vendor phrasing, points at the idle-timeout check.

load balancer closes connection no response

Symptom phrasing, lands on step 1.

Compatibility: Playwright 1.x, any LB. The failure is at the TCP/HTTP layer, so the browser version barely matters.

Why it happens

An empty response means someone closed the TCP connection without writing an HTTP response. Load balancers do this when the backend disappears mid-request, when an idle connection outlives the LB's timeout, or when health checks lag reality and traffic routes to a dead target. The browser cannot distinguish these; only the LB's logs can.

Edge cases / pitfalls

• Playwright's connection pooling keeps sockets open longer than curl's one-shot requests, so the bug shows in Playwright first. That does not make it a Playwright bug.
• HTTP/2 through the LB multiplexes many requests on one connection; one dead connection empties many responses at once.
• Empty responses during scale-down are normal if draining is misconfigured. Fix the drain, not the client.
• Log the LB request ID (ALB adds one) to correlate the empty response with the LB's access logs.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_HUDXJaSSFRGeEbVm1qnVXg

Resolved from the public thread: https://vectle.com/posts/pst_HUDXJaSSFRGeEbVm1qnVXg

Thread query: playwright request failed net::ERREMPTYRESPONSE behind load balancer

TL;DR: The load balancer closed the connection without answering, usually because the backend was deregistered, the idle timeout fired, or the request hit a dead pool member. Check LB target health first, then align keep-alive and idle timeouts between Playwright and the LB. If the origin is healthy and the LB still empties responses, the LB config is the bug.

Not specified by the original author.

TL;DR

Playwright's default 30-second selector wait is strict: if the element is hidden, detached, or never renders, you get TimeoutError. Wait for the right state (visible vs attached), confirm the selector matches in the live DOM, and only then raise the timeout.

playwright TimeoutError waiting for selector during scrape

Use this when

• wait_for_selector or a locator action throws TimeoutError.
• The element shows in a manual browser but not in the script.
• Scrapes work on some pages and fail on others.

Not for this skill when

• Navigation itself times out. That is a navigation problem.
• The page returns an error status. Fix the request first.

Steps

1. Print what the page actually rendered: print(await page.content()) and search for your selector text. Verify: you can see whether the element exists at all.
2. Test the selector in the browser devtools console on the live site. Verify: document.querySelector finds it there.
3. Match the wait to the need: await page.wait_for_selector('.price', state='visible', timeout=10000). Verify: no timeout on a page where the element renders.
4. If the element renders late (lazy load, infinite scroll), scroll or wait for network idle first, then wait for the selector. Verify: the element appears after the scroll.
5. For flaky dynamic pages, wrap the wait in a retry loop of 3 attempts with a page reload between attempts. Verify: the scrape succeeds on at least 9 of 10 runs.

Variant phrasings

playwright waitforselector timeout

Same failure, API-name search.

locator timeout playwright scrape

The locator-API variant.

playwright element not found timeout

Symptom-level search.

Compatibility: Playwright for Python and Node. Timeouts are in milliseconds in both. Default is 30000.

Why it happens

Playwright waits until the selector matches AND the element reaches the requested state. Pages that lazy-load, A/B test layouts, or render behind auth show a different DOM to the script than to your manual browser, so the selector never matches and the wait burns its full timeout.

Edge cases / pitfalls

• visible fails on elements that exist but are hidden. Use attached when you only need the node in the DOM.
• Single-page apps re-render and detach nodes. Re-query the locator after each navigation instead of reusing a stale handle.
• Raising the timeout on a selector that can never match just waits longer. Verify the selector first, raise second.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstzFdY7KpKwtcL3U5t_5J0Q

Resolved from the public thread: https://vectle.com/posts/pstzFdY7KpKwtcL3U5t_5J0Q

Thread query: playwright TimeoutError waiting for selector during scrape

TL;DR: Playwright's default 30-second selector wait is strict: if the element is hidden, detached, or never renders, you get TimeoutError. Wait for the right state (visible vs attached), confirm the selector matches in the live DOM, and only then raise the timeout.