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wiki/concepts/Minimum-Viable-Harness.md

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+---
+title: "Minimum Viable Harness"
+type: concept
+tags:
+  - "harness-engineering"
+  - "agentic-ai"
+  - "quick-start"
+sources:
+  - "Your-AI-Isn-t-Stupid---It-Just-Needs-a-Better-Harness--Lychee-Technology-Engineering-Blog"
+last_updated: 2026-04-20
+---
+
+## Overview
+Minimum Viable Harness——Day 1 即可构建的 4 个核心组件，使 Agent 能够优雅失败，为后续增加智能赢得权利。
+
+## The 4 Components
+
+### 1. `state.json`
+单一结构化文件跟踪任务状态——如果进程死亡，可以从上次停止的地方继续。
+```json
+{
+  "task_id": "report-001",
+  "steps": {
+    "fetch_competitor_a": "COMPLETED",
+    "fetch_competitor_b": "IN_PROGRESS",
+    "compare": "PENDING"
+  },
+  "last_updated": "2026-04-20T10:30:00Z"
+}
+```
+
+### 2. Retry Wrapper
+每个工具调用包装 try/catch，至少一次自动重试 + 指数退避：
+```python
+def tool_call_with_retry(func, max_attempts=3):
+    for attempt in range(max_attempts):
+        try:
+            return func()
+        except (TimeoutError, APIError) as e:
+            if attempt < max_attempts - 1:
+                sleep(exponential_backoff(attempt))
+            else:
+                raise
+```
+
+### 3. Schema Validator
+每个 LLM 输出在接收前必须通过 JSON Schema 验证。格式不符触发重试，不触发崩溃：
+```python
+def validate_and_retry(llm_output, schema):
+    try:
+        validated = jsonschema.validate(llm_output, schema)
+        return validated
+    except ValidationError:
+        return retry_with_error_feedback(llm_output, schema)
+```
+
+### 4. Tool Output Truncation
+每个工具 payload 硬性上限固定 token 预算——context window 内的静默截断是幻觉最常见原因之一：
+```python
+MAX_TOOL_TOKENS = 3000  # 保守上限
+
+def truncate_tool_output(raw_output, max_tokens=MAX_TOOL_TOKENS):
+    tokens = encode(raw_output)
+    if len(tokens) > max_tokens:
+        return decode(tokens[:max_tokens]) + "\n[TRUNCATED]"
+    return raw_output
+```
+
+## Philosophy
+> 你可以忍受不完美的提示词。你可以忍受天真的工具集成。但是你无法忍受一个失败时破坏自己状态或静默吞噬错误的 Agent。
+
+## Source
+- [[Your-AI-Isn-t-Stupid---It-Just-Needs-a-Better-Harness--Lychee-Technology-Engineering-Blog]]
+
+## See Also
+- [[Harness-Engineering]] — 完整学科框架
+- [[7-Layer-Harness-Stack]] — 完整 7 层实现