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What does the underscore trick do?

Q: What does the underscore trick do?

If you saw someone type capital of france _ and watch the underscore turn into Paris, that's OpenCues. The _ is a typed request: place it where you want a response, and the system reads the surrounding text, infers what's being asked, and answers in place. Nothing fires until you type it.

If you saw someone type capital of france _ and watch the underscore turn into Paris, that's OpenCues. The _ is a typed request: place it where you want a response, and the system reads the surrounding text, infers what's being asked, and answers in place. Nothing fires until you type it.

One character, three resolution paths

You never pick a mode; the text around the _ decides, in priority order. Registered keywords win first (volume _ reads your system volume, nvda _ a live stock quote, deterministic and LLM-free). An instruction next to the _ fires a transform (make this more formal _ rewrites the text before it, consuming the instruction). Everything else is a lookup: an LLM segments the question out of your text and writes the answer into the _, leaving everything you typed in place (the total is _ becomes the total is 42).

Why an underscore, of all characters

Two reasons from the Inline Prompting essay. It's typeable everywhere: shift-hyphen on QWERTY, present on every phone keyboard, no menu or plugin, which is what lets the primitive port from terminal to browser. And it's pre-loaded: anyone who ever did a fill-in-the-blank quiz already knows what ___ invites. The deeper design point is that it flips autocomplete: instead of the system choosing when and where to suggest, you choose exactly where the response lands, and the system only has to figure out what to put there.

The properties that make it trustworthy

Visible failure. If nothing can resolve the blank, the _ simply stays. There is no silent tried-and-gave-up state.
Ownership lock. Once resolved, no other suggestion can overwrite the result; editing the word releases it.
Reversible. Navigate to a filled answer and cycle to see alternatives or restore what you typed.
Multiple blanks. One input can carry several _s, each dispatched independently.

Trying it yourself

Install OpenCues, set a provider key, and type 4 * 12 = _ in a supported host. If you write markdown and worry about literal underscores, a spaced trigger mode makes a bare _ inert until a space confirms it.