Stuff it vs edit it

after an original for the agent engineering lesson

One window, two ways to fill it same task, same 200K

one questionone repo · 2.1M tokens40 turns of history12 turns of work

they part company here — what gets assembled

Paste it all

a bigger window will fix it

everything▸concatenate▸send
  • system + tool defs8%
  • three PDFs, whole10%
  • the question2%
  • what the run read72%
  • left for the work8%
left for the work8%
evictions6
re-reads6

6 evictions in: the run is now paying to read files it already read.

Edit it

the window is the budget

everything▸select▸compress▸reserve▸send
  • system + tool defs8%
  • the standing rules2%
  • the passages that matter12%
  • history, as conclusions6%
  • the question2%
  • what the run read24%
  • left for the work46%
left for the work46%
compactions2
re-reads0

2 compactions: transcript dropped, conclusions kept, nothing re-read.

Both designs fill up; only one can afford to choose what it loses. A window that starts at 88% has no compaction strategy available to it, only eviction — and eviction is how a run ends up paying twice for the same file.

turn 12 / 12