Agents: safeguard compaction summarization

docs/gateway/configuration.md

@@ -1392,6 +1392,8 @@ See [/concepts/session-pruning](/concepts/session-pruning) for behavior details.
 
 #### `agents.defaults.compaction` (reserve headroom + memory flush)
 
+`agents.defaults.compaction.mode` selects the compaction summarization strategy. Defaults to `default`; set `safeguard` to enable chunked summarization for very long histories. See [/compaction](/compaction).
+
 `agents.defaults.compaction.reserveTokensFloor` enforces a minimum `reserveTokens`
 value for Pi compaction (default: `20000`). Set it to `0` to disable the floor.
 
@@ -1413,6 +1415,7 @@ Example (tuned):
   agents: {
     defaults: {
       compaction: {
+        mode: "safeguard",
         reserveTokensFloor: 24000,
         memoryFlush: {
           enabled: true,