microcompact method

List<Message> microcompact(List<Message> messages, { int keepRecent = 5, })

Lightweight pre-API clearing of old tool results.

Keeps the last keepRecent tool-result-bearing messages intact and replaces older compactable tool results with clearedMessage. This is a cheap way to reclaim tokens without an API round-trip.

Implementation

List<Message> microcompact(List<Message> messages, {int keepRecent = 5}) {
  final result = List<Message>.from(messages);
  final toolResultIndices = <int>[];

  for (int i = 0; i < result.length; i++) {
    final msg = result[i];
    if (msg.role != MessageRole.user) continue;
    for (final block in msg.content) {
      if (block is ToolResultBlock) {
        toolResultIndices.add(i);
        break;
      }
    }
  }

  if (toolResultIndices.length <= keepRecent) return result;

  final toClear = toolResultIndices.sublist(
    0,
    toolResultIndices.length - keepRecent,
  );

  for (final idx in toClear) {
    final msg = result[idx];
    final clearedContent =
        msg.content.map((block) {
          if (block is ToolResultBlock && _isCompactable(block)) {
            return ToolResultBlock(
              toolUseId: block.toolUseId,
              content: clearedMessage,
              isError: block.isError,
            );
          }
          return block;
        }).toList();

    result[idx] = Message(
      id: msg.id,
      role: msg.role,
      content: clearedContent,
      stopReason: msg.stopReason,
      usage: msg.usage,
    );
  }

  return result;
}