A browser agent that runs in its own cloud browser often cannot use the largest sites. Amazon and some account pages show an error page or a bot check, so the agent cannot shop, check a price or cancel a subscription there. The same agent works on smaller sites.
Testers report that Amazon changed its site rules to keep out shopping agents from OpenAI and Google. Agents that run in a remote browser also look like new, unknown devices to login and fraud checks.
Plan for the block. Ask the agent to try each big site once and report, not retry in a loop. For blocked sites, have the agent give you the direct link and the exact steps, and do that part yourself. An agent that runs in your own logged-in browser, such as Claude in Chrome, may get further, but you still sign in yourself and approve each action. Never ask an agent to get around a CAPTCHA. Anthropic lists that as a prohibited use.
The writer says ChatGPT agent hit a 503 error page on Amazon on every attempt and then said network restrictions made Amazon impossible. He says the same purchase at PetSmart went through the full checkout flow without trouble.
The writer says the agent cancelled Peacock, Disney+ and Netflix after she typed her own logins. She did not try those sites herself, but writes that some, such as Amazon Prime and Google One, may block the agent or flag it as suspicious, and that it handles Spotify but not Amazon.
The author says the agent often failed on logins, unsupported browser states and dynamic single-page sites, and that some tasks were faster to do by hand.