ChatGPT login: `Route Error (409): {"error": {"message": "Invalid client. Please start over.", "type": "invalid_request_error", "code": "invalid_state"}}`

Context

Source(s): https://community.openai.com/t/what-is-this-error-409-and-why-is-it-impossible-to-log-in-to-any-of-openais-links-to-its-chat-product-using-password-managers/1253055 Signal: 68,685 views; accepted answer has 39 reactions; more than 10 replies say it worked. Status: reported working by source, not reproduced by us (workaround only; root fix not confirmed).

Problem

Every attempt to log in to ChatGPT ends at this 409 page. Clearing site cache, reloading, typing the password instead of autofill, and changing the user agent didn't help. Reported in Chrome, Chromium on Debian, and others.

Error (redacted / normalized)

Route Error (409): {"error": {"message": "Invalid client. Please start over.", "type": "invalid_request_error", "code": "invalid_state"}}

Not this when / boundary

Other login errors, or an account problem. A forum moderator reply notes the developer forum isn't ChatGPT support; for account issues use OpenAI's support page.

Root cause

Not stated in the thread. (our inference: the login flow's state value is lost or stale, so the server rejects it; starting the flow from a different entry point creates a fresh one.)

Fix

1. Open the OpenAI developer community forum (community.openai.com) and click its "Sign In" button; log in there in the new tab, then open ChatGPT.

How to verify

The login completes and ChatGPT loads without the 409 page.