Function maybeTimeBasedMicrocompact

src/services/compact/microCompact.ts:446–530

(
  messages: Message[],
  querySource: QuerySource | undefined,
)

}

function maybeTimeBasedMicrocompact(
  messages: Message[],
  querySource: QuerySource | undefined,
): MicrocompactResult | null {
  const trigger = evaluateTimeBasedTrigger(messages, querySource)
  if (!trigger) {
    return null
  }
  const { gapMinutes, config } = trigger

  const compactableIds = collectCompactableToolIds(messages)

  // Floor at 1: slice(-0) returns the full array (paradoxically keeps
  // everything), and clearing ALL results leaves the model with zero working
  // context. Neither degenerate is sensible — always keep at least the last.
  const keepRecent = Math.max(1, config.keepRecent)
  const keepSet = new Set(compactableIds.slice(-keepRecent))
  const clearSet = new Set(compactableIds.filter(id => !keepSet.has(id)))

  if (clearSet.size === 0) {
    return null
  }

  let tokensSaved = 0
  const result: Message[] = messages.map(message => {
    if (message.type !== 'user' || !Array.isArray(message.message.content)) {
      return message
    }
    let touched = false
    const newContent = message.message.content.map(block => {
      if (
        block.type === 'tool_result' &&
        clearSet.has(block.tool_use_id) &&
        block.content !== TIME_BASED_MC_CLEARED_MESSAGE
      ) {
        tokensSaved += calculateToolResultTokens(block)
        touched = true
        return { ...block, content: TIME_BASED_MC_CLEARED_MESSAGE }
      }
      return block
    })
    if (!touched) return message
    return {
      ...message,
      message: { ...message.message, content: newContent },
    }
  })

  if (tokensSaved === 0) {
    return null
  }

  logEvent('tengu_time_based_microcompact', {
    gapMinutes: Math.round(gapMinutes),
    gapThresholdMinutes: config.gapThresholdMinutes,
    toolsCleared: clearSet.size,
    toolsKept: keepSet.size,
    keepRecent: config.keepRecent,