Update cost calculations (#152)

* Fix cost calculations by removing duplicate multiplier application

The CSV data already includes model multipliers in requestsUsed values.
Fixed excessCost calculation in getModelUsageSummary and getExpectedExcessCost
to not multiply by the multiplier again. Updated tests to reflect correct behavior.
The multiplier is still displayed in the UI for informational purposes.

Agent-Logs-Url: https://github.com/RHSplinter/github-copilot-premium-reqs-usage/sessions/7777403e-d7c3-4c8b-8f8e-ff51db24c81e

Co-authored-by: RHSplinter <60773832+RHSplinter@users.noreply.github.com>

* Remove notes

* Ensure excess costs for default models are always 0

Default models (with multiplier = 0) are free and should never incur
excess costs, even when exceeding quota. Added check to ensure
excessCost is 0 for models with multiplier = 0. Updated test to
reflect this correct behavior.

Agent-Logs-Url: https://github.com/RHSplinter/github-copilot-premium-reqs-usage/sessions/4b7fec75-998c-4d97-980b-8190a0d0b13c

Co-authored-by: RHSplinter <60773832+RHSplinter@users.noreply.github.com>

* Remove notes

* Added GPT-5 mini to default models

---------

Co-authored-by: anthropic-code-agent[bot] <242468646+Claude@users.noreply.github.com>
Co-authored-by: Rob Bos <rajbos@users.noreply.github.com>

Author: 3 people

src/lib/utils.ts

@@ -251,7 +251,12 @@ export function getModelUsageSummary(data: CopilotUsageData[]): ModelUsageSummar
     }
 
     // Calculate excess cost
-    groupedSummary[key].excessCost = groupedSummary[key].exceedingRequests * groupedSummary[key].multiplier * EXCESS_REQUEST_COST;
+    // Free models (multiplier = 0) have no excess cost
+    if (groupedSummary[key].multiplier === 0) {
+      groupedSummary[key].excessCost = 0;
+    } else {
+      groupedSummary[key].excessCost = groupedSummary[key].exceedingRequests * EXCESS_REQUEST_COST;
+    }
   });
 
   // Convert to array and sort by total requests (descending)
@@ -396,7 +401,7 @@ export const MODEL_MULTIPLIERS: Record<string, number> = {
 };
 
 // Default models that should be grouped
-export const DEFAULT_MODELS = ['GPT-4o', 'GPT-4.1', 'gpt-4o-2024-11-20', 'gpt-4.1-2025-04-14'];
+export const DEFAULT_MODELS = ['GPT-4o', 'GPT-4.1', 'GPT-5 mini', 'gpt-4o-2024-11-20', 'gpt-4.1-2025-04-14'];
 
 function normalizeModelName(model: string): string {
   return model.replace(/^Auto:\s*/, '').trim();
@@ -952,13 +957,13 @@ export function getExpectedExcessCost(data: CopilotUsageData[], plan: string = C
 
     const numDays = datesForAverage.length;
 
-    // Project extra requests per model over remaining days and apply cost multiplier
+    // Project extra requests per model over remaining days
     Object.entries(modelTotals).forEach(([model, total]) => {
       const multiplier = getModelMultiplier(model);
       if (multiplier === 0) return; // Free models have no cost
       const dailyAvg = total / numDays;
       const projectedExtra = dailyAvg * remainingDays;
-      totalExpectedCost += projectedExtra * multiplier * EXCESS_REQUEST_COST;
+      totalExpectedCost += projectedExtra * EXCESS_REQUEST_COST;
     });
   });
 

src/test/model-info-limits.test.ts

@@ -98,14 +98,15 @@ describe('Model Info and Limits Feature', () => {
     expect(defaultGroup).toBeDefined();
 
     if (defaultGroup) {
-      // 50 exceeding requests * 0x multiplier * $0.04 = $0.00
-      expect(defaultGroup.excessCost).toBe(50 * 0 * EXCESS_REQUEST_COST);
+      // Default models are free (multiplier = 0), so excess cost is always $0.00
+      // even if there are exceeding requests
+      expect(defaultGroup.excessCost).toBe(0);
     }
-    
+
     const o3Model = result.find(item => item.model === 'o3-mini-2025-01-31');
     if (o3Model) {
-      // 10 exceeding requests * 0.33x multiplier * $0.04 = $0.132
-      expect(o3Model.excessCost).toBe(10 * 0.33 * EXCESS_REQUEST_COST);
+      // 10 exceeding requests * $0.04 = $0.40
+      expect(o3Model.excessCost).toBe(10 * EXCESS_REQUEST_COST);
     }
   });