fix(knowledge): bill rerank on every successful API call and fix MDX docs literal

Author: waleedlatif1

apps/docs/content/docs/en/tools/knowledge.mdx

@@ -48,7 +48,7 @@ Search for similar content in a knowledge base using vector similarity
 | `tagName` | string | No | No description |
 | `tagValue` | string | No | No description |
 | `rerankerEnabled` | boolean | No | Whether to apply Cohere reranking to vector search results |
-| `rerankerModel` | string | No | Cohere rerank model to use \(one of: $\{SUPPORTED_RERANKER_MODELS.join\(', '\)\}\) |
+| `rerankerModel` | string | No | Cohere rerank model to use \(one of: rerank-v4.0-pro, rerank-v4.0-fast, rerank-v3.5\) |
 | `tagFilters` | string | No | No description |
 
 #### Output

apps/sim/app/api/knowledge/search/route.ts

@@ -365,6 +365,9 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
 
       // Optional Cohere rerank pass on top of vector results.
       const rerankedScores = new Map<string, number>()
+      // `rerankBilled` = Cohere was successfully called (even with 0 results) and we owe the search unit.
+      // `rerankApplied` = result ordering was actually replaced by the reranker output.
+      let rerankBilled = false
       let rerankApplied = false
       if (useReranker && rerankerModel && results.length > 0) {
         const candidateCount = results.length
@@ -374,6 +377,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
             results.map((r) => ({ id: r.id, text: r.content })),
             { model: rerankerModel, topN: validatedData.topK, workspaceId }
           )
+          rerankBilled = true
           if (ranked.length === 0) {
             logger.warn(
               `[${requestId}] Reranker returned 0 results; falling back to vector ordering`,
@@ -419,9 +423,10 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
         }
       }
 
-      // Add Cohere rerank cost (1 search unit per call, since we cap candidates ≤100).
+      // Add Cohere rerank cost (1 search unit per successful call, since we cap candidates ≤100).
+      // Bill on every successful API response — Cohere charges even when 0 results are returned.
       let rerankerCost = 0
-      if (rerankApplied && rerankerModel) {
+      if (rerankBilled && rerankerModel) {
         const pricing = getRerankModelPricing(rerankerModel)
         if (pricing) {
           rerankerCost = pricing.perSearchUnit
@@ -535,7 +540,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
                   },
                   model: queryEmbeddingModel,
                   pricing: cost.pricing,
-                  ...(rerankApplied ? { rerankerCost, rerankerModel, rerankerSearchUnits: 1 } : {}),
+                  ...(rerankBilled ? { rerankerCost, rerankerModel, rerankerSearchUnits: 1 } : {}),
                 },
               }
             : {}),