Order these context elements from first to evict to never evict when the budget tightens

When the assembled prompt is about to overflow the model's context window, the budget has to give somewhere. A documented eviction order tells the system what to drop first. The principle is to evict in inverse order of load-bearingness. Anything the model has already consumed, anything that is duplicated by a higher-level abstraction, anything optional, those go first. Things that are sacred to the current call go last or never. The canonical order from first to evict to never-evict: 1. **Stale tool results that have already been consumed.** A previous turn used the result to answer a question and the answer is now in the conversation history. The raw result is dead weight. 2. **Optional retrieved chunks below the top 3.** Top-3 is usually where the signal lives; the rest is dilution. 3. **Older level-1 summaries that have a level-2 covering them.** The level-2 already contains what level-1 said; keeping both is duplicate. 4. **Rolling summary of older turns.** The summary is a compressed view; if budget is desperate, drop it before dropping the originals. 5. **Recent verbatim user-assistant turns.** Recency matters; only evict when truly out of options. 6. **Current user turn.** The question itself. Never evict. 7. **System prompt.** Persona, safety, tool definitions. Never evict. The order above is a documented policy, not a heuristic that fires per call. Documented means the team can answer 'why did the agent forget X?' with 'because the budget tightened and X was below this line in the eviction policy.'

**Eviction order is a documented policy, not an improvised compromise.** The order encodes which content is most expendable and which is sacred. From first to evict to never-evict: ### 1. Stale tool results that have been consumed A tool result is consumed when its substantive content has been written into the conversation (the assistant has answered a question using it and the answer is now in the turn history). The raw result is now redundant, the answer carries the relevant information forward. Stale tool outputs are pure overhead. Drop them first. ### 2. Optional retrieved chunks below the top 3 For RAG calls, the top 3 chunks (after rerank) usually contain the signal. Chunks 4 through k are dilution: they were retrieved because the recall safety margin asked for them, not because they were needed. When budget tightens, drop chunks k-3 down to 3. This also helps with lost-in-the-middle effects since the kept chunks are stronger signal. ### 3. Older level-1 summaries that have a level-2 covering them In a hierarchical summary scheme, level-1 (recent abstract) is rolled up into level-2 (older condensed) as conversation grows. Once a stretch of conversation is covered at level-2, the level-1 summary for that stretch is duplicate. Drop it. ### 4. Rolling summary of older turns If the budget is still tight after the above, drop the rolling summary itself. The summary is a lossy compression of recent history; keeping the verbatim recent turns is more valuable than keeping a lossy abstraction of older turns. ### 5. Recent verbatim user-assistant turns Only evict here when truly out of options. Recent turns carry context the user expects the agent to remember; evicting them produces visible 'goldfish' behavior. Trim oldest-first within the recent block. ### 6. Current user turn The question itself. Never evict. If you cannot fit the user's literal question, the request must be rejected with a clear error, not silently truncated. ### 7.