feat(loop): integrate token usage tracking into phases

- Call builder.resetStats() at start of each phase
- Log session summaries after plan, build, and eval phases
- Record token usage and costs in metrics after each operation
- Include phase labels (Plan, Task, Eval) in summary logs
- Track stats for both successful and failed task executions

Signed-off-by: leocavalcante <leo@cavalcante.dev>

Author: leocavalcante

src/loop.ts

@@ -35,6 +35,7 @@ import {
 	recordRetry,
 	recordTaskCompleted,
 	recordTaskFailed,
+	recordTokenUsage,
 	saveMetrics,
 } from "./metrics.ts"
 import { getTasks, getUncompletedTasks, markTaskComplete, validatePlan } from "./plan.ts"
@@ -271,6 +272,9 @@ async function runPlanPhase(
 	config: Config,
 	metrics: Metrics,
 ): Promise<Metrics> {
+	// Reset stats for this phase
+	builder.resetStats()
+
 	let planContent: string
 	let ideaToRemove: { path: string; filename: string } | null = null
 
@@ -398,6 +402,11 @@ async function runPlanPhase(
 	state.totalTasks = tasks.length
 	state.sessionId = builder.getSessionId()
 
+	// Log phase summary and record token usage
+	const stats = builder.getStats()
+	logger.summary(stats, "Plan")
+	metrics = recordTokenUsage(metrics, stats.inputTokens, stats.outputTokens, stats.costUsd)
+
 	return metrics
 }
 
@@ -412,6 +421,9 @@ async function runBuildPhase(
 	config: Config,
 	metrics: Metrics,
 ): Promise<Metrics> {
+	// Reset stats for this task
+	builder.resetStats()
+
 	// Ensure we have an active session (handles resume from saved state)
 	await builder.ensureSession(state.cycle, `Cycle ${state.cycle}`)
 	state.sessionId = builder.getSessionId()
@@ -469,6 +481,11 @@ async function runBuildPhase(
 
 		logger.success(`Task ${state.currentTaskNum}/${tasks.length} complete`)
 
+		// Log task summary and record token usage
+		const stats = builder.getStats()
+		logger.summary(stats, "Task")
+		metrics = recordTokenUsage(metrics, stats.inputTokens, stats.outputTokens, stats.costUsd)
+
 		// Record task completion in metrics
 		metrics = recordTaskCompleted(metrics)
 
@@ -479,7 +496,10 @@ async function runBuildPhase(
 		}
 	} else {
 		logger.logError(`Task failed: ${result.error}`)
-		// Continue to next task or retry logic could go here
+		// Log task summary even on failure
+		const stats = builder.getStats()
+		logger.summary(stats, "Task (failed)")
+		metrics = recordTokenUsage(metrics, stats.inputTokens, stats.outputTokens, stats.costUsd)
 	}
 
 	// Pause between tasks
@@ -501,6 +521,9 @@ async function runEvalPhase(
 	config: Config,
 	metrics: Metrics,
 ): Promise<Metrics> {
+	// Reset stats for this phase
+	builder.resetStats()
+
 	// Read current plan for eval
 	const planContent = await readFileOrNull(paths.currentPlan)
 	if (!planContent) {
@@ -514,6 +537,11 @@ async function runEvalPhase(
 	const result = parseEval(response)
 	const reason = extractEvalReason(response)
 
+	// Log eval summary and record token usage
+	const stats = builder.getStats()
+	logger.summary(stats, "Eval")
+	metrics = recordTokenUsage(metrics, stats.inputTokens, stats.outputTokens, stats.costUsd)
+
 	if (isComplete(result)) {
 		logger.success(`Cycle ${state.cycle} complete!`)
 		if (reason) {

src/metrics.ts

@@ -19,6 +19,9 @@ const DEFAULT_METRICS: Metrics = {
 	ideasProcessed: 0,
 	totalCycleDurationMs: 0,
 	lastActivityTime: "",
+	totalInputTokens: 0,
+	totalOutputTokens: 0,
+	totalCostUsd: 0,
 }
 
 /**
@@ -48,6 +51,9 @@ export async function loadMetrics(metricsFile: string): Promise<Metrics> {
 			totalCycleDurationMs: parsed.totalCycleDurationMs ?? DEFAULT_METRICS.totalCycleDurationMs,
 			firstRunTime: parsed.firstRunTime,
 			lastActivityTime: parsed.lastActivityTime ?? getISOTimestamp(),
+			totalInputTokens: parsed.totalInputTokens ?? DEFAULT_METRICS.totalInputTokens,
+			totalOutputTokens: parsed.totalOutputTokens ?? DEFAULT_METRICS.totalOutputTokens,
+			totalCostUsd: parsed.totalCostUsd ?? DEFAULT_METRICS.totalCostUsd,
 		}
 	} catch {
 		// Invalid JSON, return defaults
@@ -161,6 +167,28 @@ export function recordIdeaProcessed(metrics: Metrics): Metrics {
 	}
 }
 
+/**
+ * Record token usage and cost for an operation.
+ * @param metrics - Current metrics
+ * @param inputTokens - Number of input tokens used
+ * @param outputTokens - Number of output tokens used
+ * @param costUsd - Estimated cost in USD
+ * @returns Updated metrics
+ */
+export function recordTokenUsage(
+	metrics: Metrics,
+	inputTokens: number,
+	outputTokens: number,
+	costUsd: number,
+): Metrics {
+	return {
+		...metrics,
+		totalInputTokens: metrics.totalInputTokens + inputTokens,
+		totalOutputTokens: metrics.totalOutputTokens + outputTokens,
+		totalCostUsd: metrics.totalCostUsd + costUsd,
+	}
+}
+
 /**
  * Get average cycle duration in milliseconds.
  * @param metrics - Current metrics
@@ -202,6 +230,8 @@ export function formatMetricsSummary(metrics: Metrics): string {
 		`Retries: ${metrics.totalRetries} total`,
 		`Ideas: ${metrics.ideasProcessed} processed`,
 		`Avg cycle duration: ${avgDurationStr}`,
+		`Tokens: ${formatTokenCount(metrics.totalInputTokens)} in, ${formatTokenCount(metrics.totalOutputTokens)} out`,
+		`Estimated cost: ${formatCost(metrics.totalCostUsd)}`,
 	]
 
 	if (metrics.firstRunTime) {
@@ -211,6 +241,33 @@ export function formatMetricsSummary(metrics: Metrics): string {
 	return lines.join("\n")
 }
 
+/**
+ * Format token count in a human-readable way.
+ * @param tokens - Number of tokens
+ * @returns Formatted string (e.g., "1.2M", "500K", "1,234")
+ */
+export function formatTokenCount(tokens: number): string {
+	if (tokens >= 1_000_000) {
+		return `${(tokens / 1_000_000).toFixed(1)}M`
+	}
+	if (tokens >= 1_000) {
+		return `${(tokens / 1_000).toFixed(1)}K`
+	}
+	return tokens.toLocaleString()
+}
+
+/**
+ * Format cost in USD.
+ * @param cost - Cost in USD
+ * @returns Formatted string (e.g., "$1.23", "$0.05")
+ */
+export function formatCost(cost: number): string {
+	if (cost < 0.01) {
+		return `$${cost.toFixed(4)}`
+	}
+	return `$${cost.toFixed(2)}`
+}
+
 /**
  * Format duration in milliseconds to human-readable string.
  * @param ms - Duration in milliseconds
@@ -243,5 +300,8 @@ export function resetMetrics(): Metrics {
 		...DEFAULT_METRICS,
 		firstRunTime: getISOTimestamp(),
 		lastActivityTime: getISOTimestamp(),
+		totalInputTokens: 0,
+		totalOutputTokens: 0,
+		totalCostUsd: 0,
 	}
 }