feat: add session cost in session header

.gitignore

@@ -46,4 +46,4 @@ temp/
 
 
 eslint-fix/
-remotion/*
+remotion/*

src/main/utils/jsonl.ts

@@ -351,47 +351,58 @@ export function calculateMetrics(messages: ParsedMessage[]): SessionMetrics {
     }
   }
 
+  // Calculate cost per-message, then sum (tiered pricing applies per-API-call, not to aggregated totals)
+  let costUsd = 0;
+
   for (const msg of messages) {
     if (msg.usage) {
-      inputTokens += msg.usage.input_tokens ?? 0;
-      outputTokens += msg.usage.output_tokens ?? 0;
-      cacheReadTokens += msg.usage.cache_read_input_tokens ?? 0;
-      cacheCreationTokens += msg.usage.cache_creation_input_tokens ?? 0;
+      const msgInputTokens = msg.usage.input_tokens ?? 0;
+      const msgOutputTokens = msg.usage.output_tokens ?? 0;
+      const msgCacheReadTokens = msg.usage.cache_read_input_tokens ?? 0;
+      const msgCacheCreationTokens = msg.usage.cache_creation_input_tokens ?? 0;
+
+      inputTokens += msgInputTokens;
+      outputTokens += msgOutputTokens;
+      cacheReadTokens += msgCacheReadTokens;
+      cacheCreationTokens += msgCacheCreationTokens;
+
+      // Calculate cost for this message if we have pricing data
+      if (msg.model && !modelName) {
+        modelName = msg.model;
+      }
+
+      if (msg.model) {
+        const pricing = getPricing(msg.model);
+        if (pricing) {
+          const inputCost = calculateTieredCost(
+            msgInputTokens,
+            pricing.input_cost_per_token,
+            pricing.input_cost_per_token_above_200k_tokens
+          );
+          const outputCost = calculateTieredCost(
+            msgOutputTokens,
+            pricing.output_cost_per_token,
+            pricing.output_cost_per_token_above_200k_tokens
+          );
+          const cacheCreationCost = calculateTieredCost(
+            msgCacheCreationTokens,
+            pricing.cache_creation_input_token_cost ?? 0,
+            pricing.cache_creation_input_token_cost_above_200k_tokens
+          );
+          const cacheReadCost = calculateTieredCost(
+            msgCacheReadTokens,
+            pricing.cache_read_input_token_cost ?? 0,
+            pricing.cache_read_input_token_cost_above_200k_tokens
+          );
+          costUsd += inputCost + outputCost + cacheCreationCost + cacheReadCost;
+        }
+      }
     }
     if (!modelName && msg.model) {
       modelName = msg.model;
     }
   }
 
-  // Calculate cost
-  let costUsd = 0;
-  if (modelName) {
-    const pricing = getPricing(modelName);
-    if (pricing) {
-      const inputCost = calculateTieredCost(
-        inputTokens,
-        pricing.input_cost_per_token,
-        pricing.input_cost_per_token_above_200k_tokens
-      );
-      const outputCost = calculateTieredCost(
-        outputTokens,
-        pricing.output_cost_per_token,
-        pricing.output_cost_per_token_above_200k_tokens
-      );
-      const cacheCreationCost = calculateTieredCost(
-        cacheCreationTokens,
-        pricing.cache_creation_input_token_cost ?? 0,
-        pricing.cache_creation_input_token_cost_above_200k_tokens
-      );
-      const cacheReadCost = calculateTieredCost(
-        cacheReadTokens,
-        pricing.cache_read_input_token_cost ?? 0,
-        pricing.cache_read_input_token_cost_above_200k_tokens
-      );
-      costUsd = inputCost + outputCost + cacheCreationCost + cacheReadCost;
-    }
-  }
-
   return {
     durationMs: maxTime - minTime,
     totalTokens: inputTokens + cacheCreationTokens + cacheReadTokens + outputTokens,

src/renderer/components/chat/ChatHistory.tsx

@@ -824,6 +824,7 @@ export const ChatHistory = ({ tabId }: ChatHistoryProps): JSX.Element => {
               onNavigateToTool={handleNavigateToTool}
               onNavigateToUserGroup={handleNavigateToUserGroup}
               totalSessionTokens={lastAiGroupTotalTokens}
+              sessionMetrics={sessionDetail?.metrics}
               phaseInfo={sessionPhaseInfo ?? undefined}
               selectedPhase={selectedContextPhase}
               onPhaseChange={setSelectedContextPhase}

src/renderer/components/chat/SessionContextPanel/components/SessionContextHeader.tsx

@@ -12,6 +12,7 @@ import {
   COLOR_TEXT_MUTED,
   COLOR_TEXT_SECONDARY,
 } from '@renderer/constants/cssVariables';
+import { formatCostUsd } from '@shared/utils/costFormatting';
 import { ArrowDownWideNarrow, FileText, LayoutList, X } from 'lucide-react';
 
 import { formatTokens } from '../utils/formatting';
@@ -19,12 +20,14 @@ import { formatTokens } from '../utils/formatting';
 import { SessionContextHelpTooltip } from './SessionContextHelpTooltip';
 
 import type { ContextViewMode } from '../types';
+import type { SessionMetrics } from '@main/types';
 import type { ContextPhaseInfo } from '@renderer/types/contextInjection';
 
 interface SessionContextHeaderProps {
   injectionCount: number;
   totalTokens: number;
   totalSessionTokens?: number;
+  sessionMetrics?: SessionMetrics;
   onClose?: () => void;
   phaseInfo?: ContextPhaseInfo;
   selectedPhase: number | null;
@@ -37,6 +40,7 @@ export const SessionContextHeader = ({
   injectionCount,
   totalTokens,
   totalSessionTokens,
+  sessionMetrics,
   onClose,
   phaseInfo,
   selectedPhase,
@@ -115,6 +119,24 @@ export const SessionContextHeader = ({
         )}
       </div>
 
+      {/* Session Metrics Breakdown */}
+      {sessionMetrics && (
+        <div
+          className="mt-2 grid grid-cols-2 gap-x-4 gap-y-1 pt-2 text-[10px]"
+          style={{ borderTop: `1px solid ${COLOR_BORDER_SUBTLE}` }}
+        >
+          {/* Cost */}
+          {sessionMetrics.costUsd !== undefined && sessionMetrics.costUsd > 0 && (
+            <div className="col-span-2">
+              <span style={{ color: COLOR_TEXT_MUTED }}>Session Cost: </span>
+              <span className="font-medium tabular-nums" style={{ color: COLOR_TEXT_SECONDARY }}>
+                {formatCostUsd(sessionMetrics.costUsd)}
+              </span>
+            </div>
+          )}
+        </div>
+      )}
+
       {/* Phase selector - only shown when compactions exist */}
       {phaseInfo && phaseInfo.phases.length > 1 && (
         <div

src/renderer/components/chat/SessionContextPanel/index.tsx

@@ -48,6 +48,7 @@ export const SessionContextPanel = ({
   onNavigateToTool,
   onNavigateToUserGroup,
   totalSessionTokens,
+  sessionMetrics,
   phaseInfo,
   selectedPhase,
   onPhaseChange,
@@ -190,6 +191,7 @@ export const SessionContextPanel = ({
         injectionCount={injections.length}
         totalTokens={totalTokens}
         totalSessionTokens={totalSessionTokens}
+        sessionMetrics={sessionMetrics}
         onClose={onClose}
         phaseInfo={phaseInfo}
         selectedPhase={selectedPhase}

src/renderer/components/chat/SessionContextPanel/types.ts

@@ -2,12 +2,12 @@
  * Type definitions for SessionContextPanel components.
  */
 
-import type { ClaudeMdSource } from '@renderer/types/claudeMd';
-import type { ContextInjection, ContextPhaseInfo } from '@renderer/types/contextInjection';
-
 // =============================================================================
 // Props Interface
 // =============================================================================
+import type { SessionMetrics } from '@main/types';
+import type { ClaudeMdSource } from '@renderer/types/claudeMd';
+import type { ContextInjection, ContextPhaseInfo } from '@renderer/types/contextInjection';
 
 export interface SessionContextPanelProps {
   /** All accumulated context injections */
@@ -24,6 +24,8 @@ export interface SessionContextPanelProps {
   onNavigateToUserGroup?: (turnIndex: number) => void;
   /** Total session tokens (input + output + cache) for comparison */
   totalSessionTokens?: number;
+  /** Full session metrics (input, output, cache tokens, cost) */
+  sessionMetrics?: SessionMetrics;
   /** Phase information for phase selector */
   phaseInfo?: ContextPhaseInfo;
   /** Currently selected phase (null = current/latest) */

test/main/utils/costCalculation.test.ts

@@ -317,7 +317,7 @@ describe('Cost Calculation', () => {
       expect(metrics.costUsd).toBeCloseTo(0.0315, 6);
     });
 
-    it('should use first model found when calculating aggregated cost', () => {
+    it("should calculate cost per-message using each message's model", () => {
       const messages: ParsedMessage[] = [
         {
           type: 'assistant',
@@ -351,10 +351,11 @@ describe('Cost Calculation', () => {
 
       const metrics = calculateMetrics(messages);
 
-      // Uses first model (sonnet) pricing for all tokens
-      // Total tokens: 2000 input, 1000 output
-      // Cost: (2000 * 0.000003) + (1000 * 0.000015) = 0.006 + 0.015 = 0.021
-      expect(metrics.costUsd).toBeCloseTo(0.021, 6);
+      // Each message uses its own model's pricing
+      // Message 1 (sonnet): (1000 * 0.000003) + (500 * 0.000015) = 0.003 + 0.0075 = 0.0105
+      // Message 2 (opus): (1000 * 0.000015) + (500 * 0.000075) = 0.015 + 0.0375 = 0.0525
+      // Total cost: 0.0105 + 0.0525 = 0.063
+      expect(metrics.costUsd).toBeCloseTo(0.063, 6);
     });
   });
 
@@ -494,6 +495,76 @@ describe('Cost Calculation', () => {
     });
   });
 
+  describe('Per-Message Tiering', () => {
+    it('should apply tiered pricing per-message, not to aggregated totals', () => {
+      // Scenario: Many messages each with cache_read tokens < 200k,
+      // but aggregated total > 200k
+      // Each message should use base rates, not tiered rates
+      const messages: ParsedMessage[] = [];
+
+      // Create 10 messages, each with 50k cache_read tokens (500k total)
+      for (let i = 0; i < 10; i++) {
+        messages.push({
+          type: 'assistant',
+          uuid: `msg-${i}`,
+          timestamp: new Date(),
+          content: [],
+          model: 'claude-3-5-sonnet-20241022',
+          usage: {
+            input_tokens: 0,
+            output_tokens: 0,
+            cache_read_input_tokens: 50000,
+          },
+          toolCalls: [],
+          toolResults: [],
+          isSidechain: false,
+        });
+      }
+
+      const metrics = calculateMetrics(messages);
+
+      // Per-message tiering: Each message uses base rate (< 200k threshold)
+      // Each message: 50,000 * 0.0000003 = $0.015
+      // Total: 10 * $0.015 = $0.15
+      const expectedCost = 10 * 50000 * 0.0000003;
+      expect(metrics.costUsd).toBeCloseTo(expectedCost, 6);
+
+      // Verify this is NOT using tiered rate on aggregated total
+      // If incorrectly aggregated: (200k * 0.0000003) + (300k * 0.0000006) = $0.24
+      const incorrectAggregatedCost = 0.24;
+      expect(metrics.costUsd).not.toBeCloseTo(incorrectAggregatedCost, 2);
+    });
+
+    it('should apply tiered rates when individual messages exceed 200k', () => {
+      const messages: ParsedMessage[] = [
+        {
+          type: 'assistant',
+          uuid: 'msg-1',
+          timestamp: new Date(),
+          content: [],
+          model: 'claude-3-5-sonnet-20241022',
+          usage: {
+            input_tokens: 0,
+            output_tokens: 0,
+            cache_read_input_tokens: 300000, // Exceeds 200k threshold
+          },
+          toolCalls: [],
+          toolResults: [],
+          isSidechain: false,
+        },
+      ];
+
+      const metrics = calculateMetrics(messages);
+
+      // Single message with 300k cache_read tokens
+      // First 200k: 200,000 * 0.0000003 = $0.06
+      // Remaining 100k: 100,000 * 0.0000006 = $0.06
+      // Total: $0.12
+      const expectedCost = 200000 * 0.0000003 + 100000 * 0.0000006;
+      expect(metrics.costUsd).toBeCloseTo(expectedCost, 6);
+    });
+  });
+
   describe('Integration with Other Metrics', () => {
     it('should include cost alongside other session metrics', () => {
       const messages: ParsedMessage[] = [

test/shared/utils/costFormatting.test.ts

@@ -0,0 +1,228 @@
+/**
+ * Tests for cost formatting utilities
+ */
+
+import { describe, it, expect } from 'vitest';
+import { formatCostUsd, formatCostCompact } from '@shared/utils/costFormatting';
+
+describe('Cost Formatting', () => {
+  describe('formatCostUsd', () => {
+    describe('Zero values', () => {
+      it('should format zero as $0.00', () => {
+        expect(formatCostUsd(0)).toBe('$0.00');
+      });
+
+      it('should format negative zero as $0.00', () => {
+        expect(formatCostUsd(-0)).toBe('$0.00');
+      });
+    });
+
+    describe('Standard amounts (>= $0.01)', () => {
+      it('should format 1 cent with 2 decimal places', () => {
+        expect(formatCostUsd(0.01)).toBe('$0.01');
+      });
+
+      it('should format 1 dollar with 2 decimal places', () => {
+        expect(formatCostUsd(1.0)).toBe('$1.00');
+      });
+
+      it('should format dollars and cents', () => {
+        expect(formatCostUsd(1.23)).toBe('$1.23');
+      });
+
+      it('should format large amounts', () => {
+        expect(formatCostUsd(999.99)).toBe('$999.99');
+        expect(formatCostUsd(1234.56)).toBe('$1234.56');
+      });
+
+      it('should round to 2 decimal places for amounts >= 1 cent', () => {
+        expect(formatCostUsd(1.234)).toBe('$1.23');
+        expect(formatCostUsd(1.235)).toBe('$1.24'); // Rounds up
+        expect(formatCostUsd(1.999)).toBe('$2.00');
+      });
+    });
+
+    describe('Sub-cent amounts ($0.001 - $0.01)', () => {
+      it('should format 1 tenth of a cent with 3 decimal places', () => {
+        expect(formatCostUsd(0.001)).toBe('$0.001');
+      });
+
+      it('should format sub-cent amounts with 3 decimal places', () => {
+        expect(formatCostUsd(0.005)).toBe('$0.005');
+        expect(formatCostUsd(0.009)).toBe('$0.009');
+      });
+
+      it('should round to 3 decimal places for sub-cent amounts', () => {
+        expect(formatCostUsd(0.0012)).toBe('$0.001');
+        expect(formatCostUsd(0.0015)).toBe('$0.002'); // Rounds up
+        expect(formatCostUsd(0.0099)).toBe('$0.010');
+      });
+    });
+
+    describe('Very small amounts (< $0.001)', () => {
+      it('should format tiny amounts with 4 decimal places', () => {
+        expect(formatCostUsd(0.0001)).toBe('$0.0001');
+        expect(formatCostUsd(0.0005)).toBe('$0.0005');
+        expect(formatCostUsd(0.0009)).toBe('$0.0009');
+      });
+
+      it('should round to 4 decimal places for tiny amounts', () => {
+        expect(formatCostUsd(0.00012)).toBe('$0.0001');
+        expect(formatCostUsd(0.00016)).toBe('$0.0002'); // Rounds up
+        expect(formatCostUsd(0.00099)).toBe('$0.0010');
+      });
+
+      it('should handle very tiny amounts', () => {
+        expect(formatCostUsd(0.000001)).toBe('$0.0000');
+      });
+    });
+
+    describe('Edge cases', () => {
+      it('should handle negative amounts with 4 decimal places', () => {
+        // Negative numbers don't match >= comparisons, so they use 4 decimals
+        expect(formatCostUsd(-1.23)).toBe('$-1.2300');
+        expect(formatCostUsd(-0.001)).toBe('$-0.0010');
+        expect(formatCostUsd(-0.0001)).toBe('$-0.0001');
+      });
+
+      it('should handle very large amounts', () => {
+        expect(formatCostUsd(1000000)).toBe('$1000000.00');
+      });
+
+      it('should handle precision boundaries', () => {
+        // Boundary between 2 and 3 decimal places
+        expect(formatCostUsd(0.01)).toBe('$0.01');
+        expect(formatCostUsd(0.00999)).toBe('$0.010'); // Just below threshold, uses 3 decimals
+
+        // Boundary between 3 and 4 decimal places
+        expect(formatCostUsd(0.001)).toBe('$0.001');
+        expect(formatCostUsd(0.00099)).toBe('$0.0010'); // Just below threshold, uses 4 decimals
+      });
+    });
+
+    describe('Real-world API cost examples', () => {
+      it('should format typical Claude API costs', () => {
+        // 1M input tokens at $3.00/M
+        expect(formatCostUsd(3.0)).toBe('$3.00');
+
+        // 100k input tokens at $3.00/M
+        expect(formatCostUsd(0.3)).toBe('$0.30');
+
+        // 10k cache read tokens at $0.30/M
+        expect(formatCostUsd(0.003)).toBe('$0.003');
+
+        // 1k cache read tokens at $0.30/M
+        expect(formatCostUsd(0.0003)).toBe('$0.0003');
+      });
+
+      it('should format session totals', () => {
+        // Small session
+        expect(formatCostUsd(0.15)).toBe('$0.15');
+
+        // Medium session
+        expect(formatCostUsd(5.67)).toBe('$5.67');
+
+        // Large session
+        expect(formatCostUsd(29.57)).toBe('$29.57');
+      });
+    });
+  });
+
+  describe('formatCostCompact', () => {
+    describe('Zero values', () => {
+      it('should format zero as 0.00', () => {
+        expect(formatCostCompact(0)).toBe('0.00');
+      });
+
+      it('should format negative zero as 0.00', () => {
+        expect(formatCostCompact(-0)).toBe('0.00');
+      });
+    });
+
+    describe('Standard amounts (>= $0.01)', () => {
+      it('should format amounts without $ prefix', () => {
+        expect(formatCostCompact(0.01)).toBe('0.01');
+        expect(formatCostCompact(1.0)).toBe('1.00');
+        expect(formatCostCompact(1.23)).toBe('1.23');
+      });
+
+      it('should format large amounts', () => {
+        expect(formatCostCompact(999.99)).toBe('999.99');
+        expect(formatCostCompact(1234.56)).toBe('1234.56');
+      });
+
+      it('should round to 2 decimal places', () => {
+        expect(formatCostCompact(1.234)).toBe('1.23');
+        expect(formatCostCompact(1.235)).toBe('1.24'); // Rounds up
+        expect(formatCostCompact(1.999)).toBe('2.00');
+      });
+    });
+
+    describe('Sub-cent amounts ($0.001 - $0.01)', () => {
+      it('should format sub-cent amounts with 3 decimal places', () => {
+        expect(formatCostCompact(0.001)).toBe('0.001');
+        expect(formatCostCompact(0.005)).toBe('0.005');
+        expect(formatCostCompact(0.009)).toBe('0.009');
+      });
+
+      it('should round to 3 decimal places', () => {
+        expect(formatCostCompact(0.0012)).toBe('0.001');
+        expect(formatCostCompact(0.0015)).toBe('0.002'); // Rounds up
+        expect(formatCostCompact(0.0099)).toBe('0.010');
+      });
+    });
+
+    describe('Very small amounts (< $0.001)', () => {
+      it('should format tiny amounts with 4 decimal places', () => {
+        expect(formatCostCompact(0.0001)).toBe('0.0001');
+        expect(formatCostCompact(0.0005)).toBe('0.0005');
+        expect(formatCostCompact(0.0009)).toBe('0.0009');
+      });
+
+      it('should round to 4 decimal places', () => {
+        expect(formatCostCompact(0.00012)).toBe('0.0001');
+        expect(formatCostCompact(0.00016)).toBe('0.0002'); // Rounds up
+        expect(formatCostCompact(0.00099)).toBe('0.0010');
+      });
+    });
+
+    describe('Edge cases', () => {
+      it('should handle negative amounts with 4 decimal places', () => {
+        // Negative numbers don't match >= comparisons, so they use 4 decimals
+        expect(formatCostCompact(-1.23)).toBe('-1.2300');
+        expect(formatCostCompact(-0.001)).toBe('-0.0010');
+        expect(formatCostCompact(-0.0001)).toBe('-0.0001');
+      });
+
+      it('should handle very large amounts', () => {
+        expect(formatCostCompact(1000000)).toBe('1000000.00');
+      });
+    });
+
+    describe('Comparison with formatCostUsd', () => {
+      it('should match formatCostUsd except for $ prefix', () => {
+        const testCases = [0, 0.0001, 0.001, 0.01, 1.23, 999.99];
+
+        testCases.forEach((cost) => {
+          const withPrefix = formatCostUsd(cost);
+          const compact = formatCostCompact(cost);
+
+          // Compact should equal the USD format without the $
+          expect(compact).toBe(withPrefix.substring(1));
+        });
+      });
+    });
+
+    describe('Badge display use cases', () => {
+      it('should format for badge display', () => {
+        // Small per-message costs
+        expect(formatCostCompact(0.0015)).toBe('0.002');
+        expect(formatCostCompact(0.01)).toBe('0.01');
+
+        // Session totals in badges
+        expect(formatCostCompact(2.5)).toBe('2.50');
+        expect(formatCostCompact(15.0)).toBe('15.00');
+      });
+    });
+  });
+});