Function rerank

apps/sim/lib/knowledge/reranker.ts:98–182

(
  query: string,
  items: T[],
  options: {
    model: string
    topN?: number
    workspaceId?: string | null
    /** User-supplied Cohere key from the Knowledge block field. Honored only on self-hosted. */
    apiKey?: string
  }
)

 * Returns the items in descending order of relevance, capped at `topN`.
 */
export async function rerank<T extends RerankItem>(
  query: string,
  items: T[],
  options: {
    model: string
    topN?: number
    workspaceId?: string | null
    /** User-supplied Cohere key from the Knowledge block field. Honored only on self-hosted. */
    apiKey?: string
  }
): Promise<RerankResponse<T>> {
  if (items.length === 0) return { results: [], isBYOK: false }

  if (!isSupportedRerankerModel(options.model)) {
    throw new Error(`Unsupported reranker model: ${options.model}`)
  }

  const { apiKey, isBYOK } = await resolveCohereKey(options.workspaceId, options.apiKey)
  const cappedItems =
    items.length > MAX_DOCUMENTS_PER_RERANK ? items.slice(0, MAX_DOCUMENTS_PER_RERANK) : items
  if (items.length > MAX_DOCUMENTS_PER_RERANK) {
    logger.warn(`Rerank input capped from ${items.length} to ${MAX_DOCUMENTS_PER_RERANK} documents`)
  }
  const documents = cappedItems.map((it) => it.text)

  const response = await retryWithExponentialBackoff(
    async () => {
      const controller = new AbortController()
      const timeout = setTimeout(() => controller.abort(), RERANK_REQUEST_TIMEOUT_MS)

      const res = await fetch('https://api.cohere.com/v2/rerank', {
        method: 'POST',
        headers: {
          Authorization: `Bearer ${apiKey}`,
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({
          model: options.model,
          query,
          documents,
          top_n: options.topN ?? cappedItems.length,
        }),
        signal: controller.signal,
      }).finally(() => clearTimeout(timeout))

      if (!res.ok) {
        const errorText = await res.text()
        throw new RerankAPIError(
          `Cohere rerank failed: ${res.status} ${res.statusText} - ${errorText}`,
          res.status
        )
      }

      return (await res.json()) as CohereRerankResponse
    },
    {
      maxRetries: 3,
      initialDelayMs: 500,