analysis_claude_code/docs/zh/s06-context-compact.md
2026-02-27 01:11:57 +08:00

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# s06: Context Compact (上下文压缩)
`s01 > s02 > s03 > s04 > s05 > [ s06 ] | s07 > s08 > s09 > s10 > s11 > s12`
> *"Strategic forgetting"* -- 有策略地遗忘, 换来无限会话。
## 问题
上下文窗口是有限的。读一个 1000 行的文件就吃掉 ~4000 token; 读 30 个文件、跑 20 条命令, 轻松突破 100k token。不压缩, 智能体根本没法在大项目里干活。
## 解决方案
三层压缩, 激进程度递增:
```
Every turn:
+------------------+
| Tool call result |
+------------------+
|
v
[Layer 1: micro_compact] (silent, every turn)
Replace tool_result > 3 turns old
with "[Previous: used {tool_name}]"
|
v
[Check: tokens > 50000?]
| |
no yes
| |
v v
continue [Layer 2: auto_compact]
Save transcript to .transcripts/
LLM summarizes conversation.
Replace all messages with [summary].
|
v
[Layer 3: compact tool]
Model calls compact explicitly.
Same summarization as auto_compact.
```
## 工作原理
1. **第一层 -- micro_compact**: 每次 LLM 调用前, 将旧的 tool result 替换为占位符。
```python
def micro_compact(messages: list) -> list:
tool_results = []
for i, msg in enumerate(messages):
if msg["role"] == "user" and isinstance(msg.get("content"), list):
for j, part in enumerate(msg["content"]):
if isinstance(part, dict) and part.get("type") == "tool_result":
tool_results.append((i, j, part))
if len(tool_results) <= KEEP_RECENT:
return messages
for _, _, part in tool_results[:-KEEP_RECENT]:
if len(part.get("content", "")) > 100:
part["content"] = f"[Previous: used {tool_name}]"
return messages
```
2. **第二层 -- auto_compact**: token 超过阈值时, 保存完整对话到磁盘, 让 LLM 做摘要。
```python
def auto_compact(messages: list) -> list:
# Save transcript for recovery
transcript_path = TRANSCRIPT_DIR / f"transcript_{int(time.time())}.jsonl"
with open(transcript_path, "w") as f:
for msg in messages:
f.write(json.dumps(msg, default=str) + "\n")
# LLM summarizes
response = client.messages.create(
model=MODEL,
messages=[{"role": "user", "content":
"Summarize this conversation for continuity..."
+ json.dumps(messages, default=str)[:80000]}],
max_tokens=2000,
)
return [
{"role": "user", "content": f"[Compressed]\n\n{response.content[0].text}"},
{"role": "assistant", "content": "Understood. Continuing."},
]
```
3. **第三层 -- manual compact**: `compact` 工具按需触发同样的摘要机制。
4. 循环整合三层:
```python
def agent_loop(messages: list):
while True:
micro_compact(messages) # Layer 1
if estimate_tokens(messages) > THRESHOLD:
messages[:] = auto_compact(messages) # Layer 2
response = client.messages.create(...)
# ... tool execution ...
if manual_compact:
messages[:] = auto_compact(messages) # Layer 3
```
完整历史通过 transcript 保存在磁盘上。信息没有真正丢失, 只是移出了活跃上下文。
## 相对 s05 的变更
| 组件 | 之前 (s05) | 之后 (s06) |
|----------------|------------------|--------------------------------|
| Tools | 5 | 5 (基础 + compact) |
| 上下文管理 | 无 | 三层压缩 |
| Micro-compact | 无 | 旧结果 -> 占位符 |
| Auto-compact | 无 | token 阈值触发 |
| Transcripts | 无 | 保存到 .transcripts/ |
## 试一试
```sh
cd learn-claude-code
python agents/s06_context_compact.py
```
试试这些 prompt (英文 prompt 对 LLM 效果更好, 也可以用中文):
1. `Read every Python file in the agents/ directory one by one` (观察 micro-compact 替换旧结果)
2. `Keep reading files until compression triggers automatically`
3. `Use the compact tool to manually compress the conversation`