祝融说。

[Summary]
Goal: Refactor module A's interface
Constraints: Maintain backward compatibility
Progress: Interface extraction complete, tests passing
Key Decisions: Abandoned generics approach; using trait objects instead
Next Steps: Implement module B's interface in new token

[File Tracking]
Read: src/mod.rs, src/interface.rs
Modified: src/interface.rs, tests/interface_test.rs

fn compact_tier1(messages: &mut Vec<Message>) -> usize {
    let mut freed_tokens = 0;

    for message in messages.iter_mut() {
        // 1. Discard Reasoning tokens
        let reasoning_count = message.items.iter()
            .filter(|item| matches!(item, MessageItem::Reasoning(_)))
            .count();
        message.items.retain(|item| !matches!(item, MessageItem::Reasoning(_)));
        freed_tokens += reasoning_count * AVG_TOKEN_PER_REASONING;

        // 2. Placeholder-ize old ToolResult bodies
        // Only keep the most recent N ToolResults in full
        let recent_count = 10;  // Keep the 10 most recent
        let tool_results: Vec<_> = message.items.iter_mut()
            .filter_map(|item| {
                if let MessageItem::ToolResult(tr) = item {
                    Some(tr)
                } else {
                    None
                }
            })
            .collect();

        let total = tool_results.len();
        for (i, tr) in tool_results.iter_mut().enumerate() {
            if i < total.saturating_sub(recent_count) {
                // Placeholder-ize: replace content with summary
                let summary = tr.content.iter()
                    .map(|c| match c {
                        ContentItem::Text(s) => s.chars().take(200).collect::<String>(),
                        _ => "[binary]".to_string(),
                    })
                    .collect::<Vec<_>>()
                    .join(" ");
                tr.content = vec![ContentItem::Text(format!(
                    "[TRUNCATED: {} bytes, {} chars]",
                    tr.original_size, summary.len()
                ))];
                freed_tokens += tr.original_size / AVG_BYTES_PER_TOKEN;
            }
        }
    }

    freed_tokens
}

fn compact_tier2(messages: &mut Vec<Message>, context: &Context) -> Result<usize> {
    // 1. Find the earliest segment (contiguous message block eligible for compaction)
    let span = find_compressible_span(messages)?;

    // 2. Call the LLM to generate a structured summary
    let summary = summarize_span(&span, context)?;

    // 3. Replace the segment with the summary
    let summary_tokens = estimate_tokens(&summary);
    let original_tokens = span.iter().map(|m| m.tokens).sum::<usize>();

    replace_span_with_summary(messages, &span, &summary);

    Ok(original_tokens - summary_tokens)
}

fn summarize_span(span: &[Message], context: &Context) -> Result<String> {
    let prompt = format!(
        "Please summarize the following conversation segment into a structured format.\
         \nFields: Goal, Constraints, Progress, Key Decisions, Next Steps.\
         \n\nConversation content:\n{}",
        format_messages(span)
    );
    context.llm_complete(&prompt)
}

[Summary]
Goal: Refactor module A's interface, extract into an independent trait
Constraints: Maintain backward compatibility, do not modify module B
Progress: Interface extraction complete, 3 test cases written
Key Decisions: Using trait objects rather than generics (to avoid impacting module B's compile time)
Next Steps: Begin module B's interface adaptation

[File Tracking]
Read: src/mod.rs, src/interface.rs, tests/interface_test.rs
Modified: src/interface.rs, tests/interface_test.rs

fn merge_summaries(old: &Summary, new: &Summary) -> Summary {
    Summary {
        goal: if new.goal.is_empty() { old.goal.clone() } else { new.goal.clone() },
        constraints: merge_items(&old.constraints, &new.constraints),
        progress: merge_items(&old.progress, &new.progress),
        key_decisions: merge_items(&old.key_decisions, &new.key_decisions),
        next_steps: new.next_steps.clone(), // Keep only the latest next steps
        file_tracking: merge_file_tracking(&old.file_tracking, &new.file_tracking),
    }
}

{
  "schema_version": 5,
  "session_id": "cc-session-20260715-a3b2c1",
  "created_at": "2026-07-15T10:00:00Z",
  "messages": [
    {
      "role": "user",
      "items": [{"type": "text", "text": "Refactor module A for me"}],
      "id": 1
    },
    {
      "role": "assistant",
      "items": [
        {"type": "text", "text": "Sure, let me analyze it"},
        {"type": "tool_call", "id": "call_1", "name": "read_file", "args": {"path": "src/mod.rs"}}
      ],
      "id": 2
    },
    {
      "role": "tool",
      "tool_call_id": "call_1",
      "items": [{"type": "tool_result", "content": "// module A ..."}],
      "id": 3
    }
  ]
}

fn migrate_session(session: &mut Session) -> Result<()> {
    match session.schema_version {
        1 => migrate_v1_to_v2(session),
        2 => migrate_v2_to_v3(session),
        3 => migrate_v3_to_v4(session),
        4 => migrate_v4_to_v5(session),
        5 => Ok(()),  // Current version
        _ => Err("unknown schema version"),
    }
}

fn decompress(compacted: &mut Session, full_records: &Session) -> Result<()> {
    for message in compacted.messages.iter_mut() {
        for item in message.items.iter_mut() {
            if let MessageItem::ToolResult(tr) = item {
                if tr.content.iter().any(|c| matches!(c, ContentItem::Text(t) if t.starts_with("[TRUNCATED:"))) {
                    // Restore from the full record
                    if let Some(original) = find_original(tr.tool_call_id, full_records) {
                        *tr = original.clone();
                    }
                }
            }
        }
    }
    Ok(())
}