Ultrafast

from browser_use import Agent, ChatOpenAI

agent = Agent('What is the title of https://example.com?', llm=ChatOpenAI('gpt-6-luna'), mode='ultrafast')
print(agent.mode, agent.run_sync().final_result())

mode='ultrafast' gives the agent a bu object next to the usual helpers:

Helper	What it does
`bu.state()`	Prints the page in order: `[id] role "name"` plus values, states, headings and visible text. New ids since the last look are marked.
`bu.click(id)`	Clicks the element.
`bu.type(id, text, enter=False)`	Replaces the field’s text. Also picks a native `<select>` option.

Ids are Chrome backendNodeIds, so they also work in raw CDP DOM commands. After a cell whose bu actions reached the page, the new state is printed automatically, so the agent needs fewer steps. JavaScript alert, confirm, prompt and beforeunload dialogs are accepted automatically and their text is printed.

The model writes bu.click(41). The REPL clicks accessibility-tree id 41 over CDP and prints one line: [ok] click [41] link "Next" -> page changed. Because the cell acted on the page, bu.state() runs after it and prints the page as [id] role "name" lines, with * on new ids. The output returns with the same python call.

Default

Model	Default `mode`
`bu-fast`, `bu-ultrafast`	`'ultrafast'`
everything else	`'default'`

bu-fast and bu-ultrafast are evaluated in this mode. To opt out:

from browser_use import Agent

agent = Agent('What is the title of https://example.com?', llm='bu-ultrafast', mode='default')
print(agent.mode, agent.run_sync().final_result())

For the lowest latency, combine llm='bu-ultrafast' (low reasoning, priority tier) with the default ultrafast mode. See Models.

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