You want to ask about one function. To be safe, you paste the whole eight-hundred-line file and ask. The agent answers — but it rambles, drags in three unrelated spots, and misses the exact thing you needed. You pasted more and got back less.
That paradox dissolves the moment you change the picture: context isn't a warehouse where more-stacked means safer. It's a budget.
01Every line you add has a price
The price never shows up on an invoice, so it's easy to forget. But it's real, on two fronts.
The visible one: the budget has a ceiling. Pour in eight hundred lines and at some point the most important thing gets pushed off the edge. The subtler, scarier one: buried in the heap you handed over, the core gets diluted. The agent has to guess which part you actually care about — and the more "just in case" you add, the lower its odds of guessing right.
This isn't a tip about saving money (though it does). It's about output quality: for the same question, tight-and-on-point almost always beats much-just-in-case.
02Spend on signal, not on "just in case"
Each time you're about to paste more, ask: is this signal or noise for this exact turn? The function you're editing — signal. The other seven hundred lines — noise, right now. The specific error — signal. The whole log since the session began — noise.
"Just in case" sounds careful, but it really hands the filtering job to the agent — and it filters worse than you, because it doesn't know what matters to you. Filter up front, at the input, and it's cheap and exact. Make it filter through your noise and it's expensive and hit-or-miss.
A tell that you're spending wrong: when you paste a big block and then write "just focus on part X." If only X is signal — hand over only X. The phrase "focus on X" is you admitting the rest is noise, then making the agent carry it on the desk anyway.