onboarding agent stuck when headless login failed after session cookie expired

Fix onboarding agent stuck when headless login fails after session cookie expires

TL;DR

The login fails because the agent reuses a stale session cookie instead of logging in fresh. Detect the expired session, clear the cookie, and run the full login flow again. Stale sessions are not logins.

The error

Browser automation failed
Headless login failed after session cookie expired. Onboarding agent stuck.

Use this skill

Agent? Search Vectle for this error:

curl -s "https://vectle.com/api/v1/search?q=onboarding agent stuck when headless login failed after session cookie expired"

Fix it

Step 1: Detect the expired session

Check for the login page or an auth redirect instead of assuming the session is valid.

Expected: The agent knows the session is dead.

Step 2: Clear the stale cookies

Wipe the browser context's cookies for the site.

Expected: No stale state lingers.

Step 3: Run the full login flow

Execute the complete login with fresh credentials.

Expected: A new valid session is established.

Step 4: Validate the session before work

After login, confirm an authenticated state before proceeding.

Expected: The agent never works on a dead session.

Step 5: Verify onboarding completes

Run the full onboarding flow.

Expected: It finishes without session stalls.

When this applies

• Agents stall on expired session cookies
• Headless logins fail intermittently
• You are building long-running browser agents

When it doesn't

• The credentials are wrong (fix those)
• The login page changed (fix the selectors)
• Sessions expire mid-run constantly (shorten the run or refresh)

Compatibility

Headless browsers: Playwright, Puppeteer. Cookie-based sessions.

Variant phrasings

headless login session expired

Same stall. Detect, clear, and re-login.

agent stuck expired cookie login

Stuck means the agent never noticed the expiry. Check session validity explicitly.

browser session cookie expired automation

Cookies expire on the site's schedule, not yours. Plan for it.

Why it happens

Session cookies have lifetimes, and agents that assume a persistent login break when the cookie dies. The agent keeps acting as if authenticated, every action fails or redirects, and it stalls. Explicit session validation plus re-login handles the lifecycle.

Edge cases

• Some sites expire sessions aggressively on IP or fingerprint change; headed mode can help
• Storing session cookies across runs needs secure handling
• Refresh endpoints beat full re-logins where the site offers them

If it still fails

• Run headed once and watch; the failure is usually visible within seconds.
• Capture a screenshot and the console output at the failure point on every run.
• Check whether the site offers an API for the task; UI automation is the fragile path.
• Test with a fresh browser profile to rule out cookie or cache state.
• If the site added bot protection, stop and use the sanctioned path. Do not work around it.

Prevention

• Prefer APIs over browser automation wherever the site offers one.
• Screenshot on every failure so flakes are diagnosable.
• Use resilient selectors and re-validate them on a schedule.
• Keep automation accounts' sessions and auth factors maintained.
• Rate-limit automation traffic so it never looks like an attack.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_NzhHBp-jCsLc9A3CWWZO7A