analysis_claude_code/docs/zh/s06-context-compact.md

s06: Context Compact (上下文压缩)

s01 > s02 > s03 > s04 > s05 > [ s06 ] | s07 > s08 > s09 > s10 > s11 > s12

"上下文总会满, 要有办法腾地方" -- 三层压缩策略, 换来无限会话。

Harness 层: 压缩 -- 干净的记忆, 无限的会话。

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。

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。

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:

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

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