Update nexus wiki content

wiki/concepts/State-Externalization.md

@@ -0,0 +1,53 @@
+---
+title: "State Externalization"
+type: concept
+tags:
+  - "harness-engineering"
+  - "agentic-ai"
+  - "memory"
+sources:
+  - "Your-AI-Isn-t-Stupid---It-Just-Needs-a-Better-Harness--Lychee-Technology-Engineering-Blog"
+last_updated: 2026-04-20
+---
+
+## Overview
+State Externalization——将任务状态（pending/in-progress/completed）写入磁盘文件而非仅保存在 context window 的工程实践，是 [[Harness-Engineering]] 第二原则的具体实现。
+
+## Core Principle
+> 如果一条信息对任务连续性重要——已完成什么、待处理什么、什么失败了——它必须存在于 context window 之外。
+>
+> Context window 是易失的。磁盘文件是持久的。
+
+## Two-Tier Memory Model
+
+### Working Memory (Short-term)
+当前步骤所需的即时对话和 context window。
+
+### Persistent State (Long-term)
+结构化文件（如 `state.json`）追踪精确的子任务状态：
+```json
+{
+  "task_id": "market-research-report",
+  "steps": {
+    "fetch_competitor_a": "COMPLETED",
+    "fetch_competitor_b": "COMPLETED",
+    "fetch_competitor_c": "FAILED",
+    "compare": "PENDING"
+  },
+  "last_updated": "2026-04-20T10:30:00Z"
+}
+```
+
+## Why It Matters
+- Context window 在每次新 LLM 调用时重置
+- 状态不外部化 → 每次重置都丢失进度
+- 进程崩溃 → 整个任务从头开始
+
+## [[Context-Reset]] Integration
+State Externalization 是 [[Context-Reset]] 的前提——必须先有可写磁盘的状态文件，才能实现有意义的 Context Reset。
+
+## [[Memory-Consolidation]] Integration
+State Externalization 写入的是原始状态，[[Memory-Consolidation]] 定期压缩这些状态防止膨胀。
+
+## Source
+- [[Your-AI-Isn-t-Stupid---It-Just-Needs-a-Better-Harness--Lychee-Technology-Engineering-Blog]]