Two optional features make _ lookups smarter about their surroundings: ambient context (what field are you typing in?) and blank-as-context (what do your live-data blanks currently know?).
Ambient context: the field is the hint
With ambient-context-mode: on (Chrome only, off by default), a lookup also sees the focused field's label, placeholder, and page title. paris _ in an airport-code box answers CDG; the same text in a capital-cities quiz behaves differently. Exactly three sanitized fields are forwarded: the minimal set that benchmarked best, nothing more.
Blank-as-context: your blanks become knowledge
With blank-context-mode (safe by default), a blank that opts in via as-context: exposes its live value as an ambient token. The shipped weather blank binds to your work city, so do i need a jacket _ can answer from current conditions without you typing weather. In safe mode only token names reach the provider; values substitute on your machine.
The structural safety rule
Both features feed text into text: lookup output lands in your draft and nowhere else, so even a hostile page field can only ever influence words you're about to read. See the security model.
Related: Identity context · Inline AI in Chrome · The Hacker News blank · The weather blank · The countries blank · GitHub repo