feat: deliver v1.8.0 harness reliability and parity updates

scripts/hooks/cost-tracker.js

@@ -0,0 +1,78 @@
+#!/usr/bin/env node
+/**
+ * Cost Tracker Hook
+ *
+ * Appends lightweight session usage metrics to ~/.claude/metrics/costs.jsonl.
+ */
+
+'use strict';
+
+const path = require('path');
+const {
+  ensureDir,
+  appendFile,
+  getClaudeDir,
+} = require('../lib/utils');
+
+const MAX_STDIN = 1024 * 1024;
+let raw = '';
+
+function toNumber(value) {
+  const n = Number(value);
+  return Number.isFinite(n) ? n : 0;
+}
+
+function estimateCost(model, inputTokens, outputTokens) {
+  // Approximate per-1M-token blended rates. Conservative defaults.
+  const table = {
+    'haiku': { in: 0.8, out: 4.0 },
+    'sonnet': { in: 3.0, out: 15.0 },
+    'opus': { in: 15.0, out: 75.0 },
+  };
+
+  const normalized = String(model || '').toLowerCase();
+  let rates = table.sonnet;
+  if (normalized.includes('haiku')) rates = table.haiku;
+  if (normalized.includes('opus')) rates = table.opus;
+
+  const cost = (inputTokens / 1_000_000) * rates.in + (outputTokens / 1_000_000) * rates.out;
+  return Math.round(cost * 1e6) / 1e6;
+}
+
+process.stdin.setEncoding('utf8');
+process.stdin.on('data', chunk => {
+  if (raw.length < MAX_STDIN) {
+    const remaining = MAX_STDIN - raw.length;
+    raw += chunk.substring(0, remaining);
+  }
+});
+
+process.stdin.on('end', () => {
+  try {
+    const input = raw.trim() ? JSON.parse(raw) : {};
+    const usage = input.usage || input.token_usage || {};
+    const inputTokens = toNumber(usage.input_tokens || usage.prompt_tokens || 0);
+    const outputTokens = toNumber(usage.output_tokens || usage.completion_tokens || 0);
+
+    const model = String(input.model || input._cursor?.model || process.env.CLAUDE_MODEL || 'unknown');
+    const sessionId = String(process.env.CLAUDE_SESSION_ID || 'default');
+
+    const metricsDir = path.join(getClaudeDir(), 'metrics');
+    ensureDir(metricsDir);
+
+    const row = {
+      timestamp: new Date().toISOString(),
+      session_id: sessionId,
+      model,
+      input_tokens: inputTokens,
+      output_tokens: outputTokens,
+      estimated_cost_usd: estimateCost(model, inputTokens, outputTokens),
+    };
+
+    appendFile(path.join(metricsDir, 'costs.jsonl'), `${JSON.stringify(row)}\n`);
+  } catch {
+    // Keep hook non-blocking.
+  }
+
+  process.stdout.write(raw);
+});