cost calculation fix

Author: shirleyai-co

frontend/packages/agent/src/index.ts

@@ -163,6 +163,8 @@ app.post("/api/v1/projects/:projectId/sessions/:sessionId/messages", async (c) =
     // Accumulate token usage across all message_end events (tool-use loops)
     let totalInputTokens = 0;
     let totalOutputTokens = 0;
+    let totalCacheReadTokens = 0;
+    let totalCacheWriteTokens = 0;
     let totalCost = 0;
     let responseModel: string | undefined;
     let responseProvider: string | undefined;
@@ -200,6 +202,8 @@ app.post("/api/v1/projects/:projectId/sessions/:sessionId/messages", async (c) =
             if (usage) {
               totalInputTokens += usage.input ?? usage.inputTokens ?? 0;
               totalOutputTokens += usage.output ?? usage.outputTokens ?? 0;
+              totalCacheReadTokens += usage.cacheRead ?? 0;
+              totalCacheWriteTokens += usage.cacheWrite ?? 0;
               totalCost += usage.cost?.total ?? 0;
             }
             if (msg?.model) responseModel = msg.model;
@@ -237,7 +241,13 @@ app.post("/api/v1/projects/:projectId/sessions/:sessionId/messages", async (c) =
               totalCost > 0
                 ? totalCost
                 : responseModel
-                  ? calculateModelCost(responseModel, totalInputTokens, totalOutputTokens)
+                  ? calculateModelCost(
+                      responseModel,
+                      totalInputTokens,
+                      totalOutputTokens,
+                      totalCacheReadTokens,
+                      totalCacheWriteTokens,
+                    )
                   : 0;
             const tokenUsage = responseModel
               ? {

frontend/packages/core/src/llm-providers.ts

@@ -52,27 +52,40 @@ export interface LLMModelDef {
 }
 
 /** Pricing table for system models (USD per 1M tokens) */
-export const MODEL_PRICING: Record<string, { input: number; output: number }> = {
-  "claude-opus-4-6": { input: 15, output: 75 },
-  "claude-sonnet-4-6": { input: 3, output: 15 },
-  "claude-opus-4-5": { input: 15, output: 75 },
-  "claude-sonnet-4-5": { input: 3, output: 15 },
-  "claude-haiku-4-5": { input: 0.8, output: 4 },
-  "gpt-5": { input: 2, output: 10 },
-  "gpt-5-mini": { input: 0.4, output: 1.6 },
-  o3: { input: 2, output: 10 },
-  "o4-mini": { input: 1.1, output: 4.4 },
+export const MODEL_PRICING: Record<
+  string,
+  { input: number; output: number; cacheRead: number; cacheWrite: number }
+> = {
+  // Anthropic: cacheRead = 10% of input, cacheWrite = 125% of input
+  "claude-opus-4-6": { input: 15, output: 75, cacheRead: 1.5, cacheWrite: 18.75 },
+  "claude-sonnet-4-6": { input: 3, output: 15, cacheRead: 0.3, cacheWrite: 3.75 },
+  "claude-opus-4-5": { input: 15, output: 75, cacheRead: 1.5, cacheWrite: 18.75 },
+  "claude-sonnet-4-5": { input: 3, output: 15, cacheRead: 0.3, cacheWrite: 3.75 },
+  "claude-haiku-4-5": { input: 0.8, output: 4, cacheRead: 0.08, cacheWrite: 1 },
+  // OpenAI: cacheRead = 50% of input, no cacheWrite
+  "gpt-5": { input: 2, output: 10, cacheRead: 1, cacheWrite: 2 },
+  "gpt-5-mini": { input: 0.4, output: 1.6, cacheRead: 0.2, cacheWrite: 0.4 },
+  o3: { input: 2, output: 10, cacheRead: 1, cacheWrite: 2 },
+  "o4-mini": { input: 1.1, output: 4.4, cacheRead: 0.55, cacheWrite: 1.1 },
 };
 
 /** Calculate cost in USD given model ID and token counts */
 export function calculateModelCost(
   modelId: string,
   inputTokens: number,
   outputTokens: number,
+  cacheReadTokens: number = 0,
+  cacheWriteTokens: number = 0,
 ): number {
   const pricing = MODEL_PRICING[modelId];
   if (!pricing) return 0;
-  return (inputTokens * pricing.input + outputTokens * pricing.output) / 1_000_000;
+  return (
+    (inputTokens * pricing.input +
+      outputTokens * pricing.output +
+      cacheReadTokens * pricing.cacheRead +
+      cacheWriteTokens * pricing.cacheWrite) /
+    1_000_000
+  );
 }
 
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