Function countMessagesTokensWithAPI

src/services/tokenEstimation.ts:147–213

(
  messages: Anthropic.Beta.Messages.BetaMessageParam[],
  tools: Anthropic.Beta.Messages.BetaToolUnion[],
)

}

export async function countMessagesTokensWithAPI(
  messages: Anthropic.Beta.Messages.BetaMessageParam[],
  tools: Anthropic.Beta.Messages.BetaToolUnion[],
): Promise<number | null> {
  return withTokenCountVCR(messages, tools, async () => {
    try {
      const provider = getAPIProvider()
      if (provider === 'gemini') {
        return roughTokenCountEstimationForAPIRequest(messages, tools)
      }

      const model = getMainLoopModel()
      const betas = getModelBetas(model)
      const containsThinking = hasThinkingBlocks(messages)

      if (provider === 'bedrock') {
        // @anthropic-sdk/bedrock-sdk doesn't support countTokens currently
        return countTokensWithBedrock({
          model: normalizeModelStringForAPI(model),
          messages,
          tools,
          betas,
          containsThinking,
        })
      }

      const anthropic = await getAnthropicClient({
        maxRetries: 1,
        model,
        source: 'count_tokens',
      })

      const filteredBetas =
        getAPIProvider() === 'vertex'
          ? betas.filter(b => VERTEX_COUNT_TOKENS_ALLOWED_BETAS.has(b))
          : betas

      const response = await anthropic.beta.messages.countTokens({
        model: normalizeModelStringForAPI(model),
        messages:
          // When we pass tools and no messages, we need to pass a dummy message
          // to get an accurate tool token count.
          messages.length > 0 ? messages : [{ role: 'user', content: 'foo' }],
        tools,
        ...(filteredBetas.length > 0 && { betas: filteredBetas }),
        // Enable thinking if messages contain thinking blocks
        ...(containsThinking && {
          thinking: {
            type: 'enabled',
            budget_tokens: TOKEN_COUNT_THINKING_BUDGET,
          },
        }),
      })

      if (typeof response.input_tokens !== 'number') {
        // Vertex client throws
        // Bedrock client succeeds with { Output: { __type: 'com.amazon.coral.service#UnknownOperationException' }, Version: '1.0' }
        return null