feat(agentlayer): add resilient context compaction

agents/codelayer/src/agent.ts

@@ -350,6 +350,7 @@ function mergeHooks(base: ReturnType<typeof createAgentFilesystemHooks>, hooks?:
 		preToolUse: [...base.preToolUse, ...(hooks?.preToolUse ?? [])],
 		postToolUse: [...saneDefaultOutputTruncationHooks, ...fileStatePostHooks, ...(hooks?.postToolUse ?? [])],
 		preRequest: [...base.preRequest, ...(hooks?.preRequest ?? [])],
+		compaction: [...base.compaction, ...(hooks?.compaction ?? [])],
 	}
 }
 

agents/codelayer/src/coding-subagent-tool.ts

@@ -173,6 +173,7 @@ function mergeHooks(
 		preToolUse: [...base.preToolUse, ...(hooks?.preToolUse ?? [])],
 		postToolUse: [...saneDefaultOutputTruncationHooks, ...fileStatePostHooks, ...(hooks?.postToolUse ?? [])],
 		preRequest: [...base.preRequest, ...(hooks?.preRequest ?? [])],
+		compaction: [...base.compaction, ...(hooks?.compaction ?? [])],
 	}
 }
 

packages/agentlayer-core/src/agent-run.ts

@@ -1,8 +1,9 @@
 import type { ModelMessage } from 'ai'
 import type { RunResult } from './agent'
+import type { CompactionTrigger } from './compaction'
 import type { ApprovalRequest } from './hooks'
 import type { ApprovalDecision } from './state'
-import type { TokenUsageEvent } from './token-usage'
+import type { ModelTokenUsage, TokenUsageEvent } from './token-usage'
 
 // ── AgentEvent — discriminated union for the async iterator ──────────────────
 
@@ -85,6 +86,17 @@ export type AgentEvent =
 			stepIndex: number
 			finishReason?: string
 	  } & AgentEventMeta)
+	| ({
+			type: 'compaction'
+			trigger: CompactionTrigger
+			priorContextWindowTokens?: number
+			replacedMessageCount: number
+			retainedMessageCount: number
+			summaryUsage: {
+				model: string
+				usage: Omit<ModelTokenUsage, 'estimatedCostUsd'>
+			}
+	  } & AgentEventMeta)
 
 export class AgentRun implements AsyncIterable<AgentEvent> {
 	private state: { type: 'pending' } | { type: 'resolved'; value: RunResult } = { type: 'pending' }