Function buildMessageHistory

agents/e2e/context-pruning-threshold.e2e.test.ts:176–222

(targetApproxTokens: number)

}

function buildMessageHistory(targetApproxTokens: number): Message[] {
  const messages: Message[] = []
  const roundsNeeded = Math.max(1, Math.ceil(targetApproxTokens / TOKENS_PER_ROUND))
  const now = Date.now()

  console.log(
    `  Building ${roundsNeeded} rounds for ~${targetApproxTokens} tokens ` +
    `(est ${TOKENS_PER_ROUND} tokens/round)`,
  )

  for (let i = 0; i < roundsNeeded; i++) {
    // Add sentAt timestamps so context-pruner's cache-miss detection works correctly.
    // Space messages 30s apart so no cache-miss (>5min gap) is triggered inadvertently.
    const sentAt = now - (roundsNeeded - i) * 30_000

    // User message with diverse word content (~4 chars/token)
    const userMsg = createMessage(
      'user',
      makeLargeContent(`Round ${i + 1}: `, LARGE_CONTENT_SIZE),
    )
    userMsg.sentAt = sentAt
    messages.push(userMsg)

    // Assistant response with diverse word content
    const assistantMsg = createMessage(
      'assistant',
      makeLargeContent(`Response ${i + 1}: `, LARGE_CONTENT_SIZE),
    )
    assistantMsg.sentAt = sentAt + 10_000
    messages.push(assistantMsg)

    // Add a tool call pair every other round for realism
    if (i % 2 === 0) {
      const callId = `call-${i}`
      messages.push(
        createToolCallMessage(callId, 'read_files', { paths: [`file-${i}.ts`] }),
      )
      messages.push(
        createToolResultMessage(callId, 'read_files', {
          content: makeLargeContent('', LARGE_CONTENT_SIZE / 2),
        }),
      )
    }
  }

  return messages
}

/**
 * Detects whether context pruning occurred by checking for: