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Browser Engines

Webrain drives four engines through one CDP backend. Picking the right one is the difference between a 12-second page load and a 2-second one — or between a working click and a silent no-op.
Golden rule: don’t guess the browser. webrain_navigate returns a challenge field — read it, then pick the browser for the next hop.

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Engine capability matrix

What still requires real Chrome: interactive Material/Google widgets (dropdowns, calendars, segmented controls), interactive anti-bot challenges, and rendering edge cases beyond Obscura v0.2.0’s parity. Obscura render builds (default) now screenshot + PDF natively; no-render builds and lightpanda have no paint engine (lightpanda’s screenshot is a silent placeholder), and webrain_scrape is a plain HTTP GET. Authenticated / protected workflows also need a persistent profile + session on real Chrome — see Browser Profiles and Browser Sessions. Fallbacks to expect: webrain_batch auto-detects lightpanda’s single context and runs URLs sequentially on one reused tab (same tool call, same schema — just no intra-call parallelism). Obscura’s AX map has no option arm, so role="option" resolves as generic — drop the role filter and use filter on the label. If an a11y tree comes back empty, the page never rendered (consent/challenge gate) — check challenge and try real Chrome.

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Getting each engine

To route a specific batch to real Chrome (e.g. for interactive SPAs), pass the CDP endpoint directly:

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lightpanda vs obscura for batches

  • obscura opens N parallel tabs — concurrency is real overlap.
  • lightpanda serve holds ONE browser context; a 2nd Target.createTarget errors TargetAlreadyLoaded, so webrain_batch detects it and runs all URLs sequentially on one reused tab. Same tool call, same schema — just no intra-call parallelism. Pick obscura for large parallel crawls, lightpanda for footprint/velocity per page.

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a11y notes

Google/Material widgets are often not button: dropdowns are combobox, menu items option, segmented controls radio/tab. If role=<x> returns [], drop the role filter and filter on the visible label text instead (filter matches name, value, or css_path, case-insensitive). If the whole tree is empty, the page never rendered — check challenge/consent.