AI Systems Atlas

X-05Context Overflow

/context/context-overflow

The window fills mid-task; without a plan, the harness truncates — usually the oldest, often the most important.

Step-by-step walkthrough4 steps
  1. The window is nearly full and the task isn’t done.
  2. A large observation arrives. Something must go.
  3. Default truncation evicts the oldest — the system prompt and the user’s constraint.
  4. “Staging only” is gone. The agent no longer knows it ever existed.
Key insight

Overflow behavior is an architectural decision that most systems make by accident. Decide it before you need it: what gets evicted, what is untouchable.

Failure mode

Oldest-first truncation: the system prompt and the user’s constraints are, by definition, the oldest things in the window.

Further reading
RelatedContext compactionContext budget

Elsewhere in the atlas

Harnesses →Security →Evals →Coding Agents →Tools →Ops →