Agents: summarize dropped messages during compaction safeguard pruning (#2418)

src/config/types.agent-defaults.ts

@@ -244,6 +244,8 @@ export type AgentCompactionConfig = {
   mode?: AgentCompactionMode;
   /** Minimum reserve tokens enforced for Pi compaction (0 disables the floor). */
   reserveTokensFloor?: number;
+  /** Max share of context window for history during safeguard pruning (0.1–0.9, default 0.5). */
+  maxHistoryShare?: number;
   /** Pre-compaction memory flush (agentic turn). Default: enabled. */
   memoryFlush?: AgentCompactionMemoryFlushConfig;
 };

src/config/zod-schema.agent-defaults.ts

@@ -90,6 +90,7 @@ export const AgentDefaultsSchema = z
       .object({
         mode: z.union([z.literal("default"), z.literal("safeguard")]).optional(),
         reserveTokensFloor: z.number().int().nonnegative().optional(),
+        maxHistoryShare: z.number().min(0.1).max(0.9).optional(),
         memoryFlush: z
           .object({
             enabled: z.boolean().optional(),