What it can see right now

Think of it when a long session starts to forget rules it followed an hour ago.

In everyday life

It is like a small desk: each new page you open pushes an older page off the edge or into a one-line note. You can work only from what is on the desk now.

One case

At the start of a session you tell an agent that a ride-sharing app stores fares in cents. Then it reads a 9,000-line log and runs the full test suiteAll of a project’s automated tests, run together with one command. three times, and the outputs fill its window. The tool squeezes the older messages into a short summary, and the summary drops your rule. At the next edit the agent saves a $25.50 fare as 25.5 instead of 2550.

The rule fell out of the window before the edit
The case, cell by cell1 cell = 1 step
Rule you gave
centscentscentscentscentscents
Rule the agent still sees
centscentscentscentsgonegone
Saved for $25.50
25.5
Log lines read
9,000
The summary made during the third test run left the rule out.

Every case

The window holds everything the agent works from, and everything competes for it: instructions, files, command output. Raw output is the usual thief: one long log can take as much space as an hour of talk. When space runs out, details drop, and the tool does not always tell you which ones. A crowded window can also lower the agent’s quality before it is full.

The word

Engineers call this

context windowEverything the agent can see at one moment: your messages, the files it read, the output of the commands it ran. It has a fixed size. When it fills up, most tools cut older material or squeeze it into a short summary, and details can be lost.

Guard the window. Send bulk reading to a helper that returns a summary, keep standing rules in a file, and start a fresh session with written notes when the old one gets long.

Where this idea leads

Skills that encode it

  • principle-guard-the-context-window pstackRoute bulk to subagents and keep summaries, not raw payloads, in the main thread.
  • handoff Matt PocockCompacts the conversation into a document a fresh agent can pick up, so the old session can end.
  • writing-for-agents Matt PocockEvery always-loaded line spends context load on every turn, whether or not it fires.