buildToolAgentScratchpad function

List<ChatMessage> buildToolAgentScratchpad(List<AgentStep> intermediateSteps)

Builds the ordered chat transcript for tool-agent intermediate steps.

Parallel actions from one planning iteration contain the same assistant AgentAction.messageLog. When their logs match, this helper emits that log once followed by every tool result. Steps without an AgentStep.iteration, or custom steps with inconsistent logs, retain the legacy per-step layout.

Implementation

List<ChatMessage> buildToolAgentScratchpad(
  final List<AgentStep> intermediateSteps,
) {
  final messages = <ChatMessage>[];
  var index = 0;
  while (index < intermediateSteps.length) {
    final step = intermediateSteps[index];
    final iteration = step.iteration;
    if (iteration == null) {
      _appendLegacyStep(messages, step);
      index += 1;
      continue;
    }

    var end = index + 1;
    while (end < intermediateSteps.length &&
        intermediateSteps[end].iteration == iteration) {
      end += 1;
    }
    final group = intermediateSteps.sublist(index, end);
    const equality = DeepCollectionEquality();
    final sharedLog = group.first.action.messageLog;
    final logsMatch = group.every(
      (candidate) => equality.equals(candidate.action.messageLog, sharedLog),
    );

    if (logsMatch) {
      messages
        ..addAll(sharedLog)
        ..addAll(group.map(_toolResultMessage));
    } else {
      for (final candidate in group) {
        _appendLegacyStep(messages, candidate);
      }
    }
    index = end;
  }
  return messages;
}