Progressive Summarisation Risk

Definition

The failure mode where repeatedly summarising already-summarised context compounds detail loss, so each round strips more information and important facts silently disappear.

Key points

• Progressive summarisation compounds detail loss — summarising a summary each turn erodes fidelity.
• Mitigation (playbook): preserve the full verbatim message history for the active, unresolved issue; only summarise earlier, resolved turns into a narrative block.
• Prefer external durable memory — the Scratchpad Pattern (a dense structured file) — over re-summarising raw history.
• Interacts with Lost In The Middle: lossy summaries pushed to mid-context are recalled even less reliably.

Why it matters for the exam

• Tests recognising when not to summarise: keep verbatim what's still active; summarise only what's resolved. A common distractor in long-session design questions.

Common gotchas

• "Summarise everything to save tokens" is usually wrong — it loses the active issue's detail.
• Distinct from Server-side Compaction done well; the risk is naive re-summarisation, not compaction itself.

See also

• Server-side Compaction
• Lost In The Middle
• Scratchpad Pattern
• Context Rot

Sources

• netlight-study-guide
• architects-playbook