fix: calculate cost for Claude Code provider when CLI doesn't provide it

- Use cost_usd from CLI response when available
- Fall back to calculating cost based on token usage and model pricing
- Ensures consistent cost reporting across all providers

src/api/providers/claude-code.ts

@@ -10,6 +10,7 @@ import { ApiStreamUsageChunk, type ApiStream } from "../transform/stream"
 import { runClaudeCode } from "../../integrations/claude-code/run"
 import { ClaudeCodeMessage } from "../../integrations/claude-code/types"
 import { BaseProvider } from "./base-provider"
+import { calculateApiCostAnthropic } from "../../shared/cost"
 
 export class ClaudeCodeHandler extends BaseProvider implements ApiHandler {
 	private options: ApiHandlerOptions
@@ -132,7 +133,20 @@ export class ClaudeCodeHandler extends BaseProvider implements ApiHandler {
 			}
 
 			if (chunk.type === "result" && "result" in chunk) {
-				usage.totalCost = chunk.cost_usd || 0
+				// Use the cost from the CLI if available, otherwise calculate it
+				if (chunk.cost_usd !== undefined && chunk.cost_usd !== null) {
+					usage.totalCost = chunk.cost_usd
+				} else {
+					// Calculate cost based on token usage and model pricing
+					const modelInfo = this.getModel().info
+					usage.totalCost = calculateApiCostAnthropic(
+						modelInfo,
+						usage.inputTokens,
+						usage.outputTokens,
+						usage.cacheWriteTokens,
+						usage.cacheReadTokens,
+					)
+				}
 
 				yield usage
 			}