diff --git a/examples/cookbook/translation-backtranslation.ts b/examples/cookbook/translation-backtranslation.ts
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+/**
+ * Translation + Backtranslation Quality Check (Cross-Model)
+ *
+ * Demonstrates:
+ * - Agent A: translate EN -> target language with Claude
+ * - Agent B: back-translate -> EN with a different provider family
+ * - Agent C: compare original vs. backtranslation and flag semantic drift
+ * - Structured output with Zod schemas
+ *
+ * Run:
+ *   npx tsx examples/cookbook/translation-backtranslation.ts
+ *
+ * Prerequisites:
+ *   ANTHROPIC_API_KEY must be set
+ *   and at least one of OPENAI_API_KEY / GEMINI_API_KEY must be set
+ */
+
+import { z } from 'zod'
+import {
+  Agent,
+  AgentPool,
+  ToolRegistry,
+  ToolExecutor,
+  registerBuiltInTools,
+} from '../../src/index.js'
+import type { AgentConfig } from '../../src/types.js'
+
+// ---------------------------------------------------------------------------
+// Inline sample text (3-5 technical paragraphs, per issue requirement)
+// ---------------------------------------------------------------------------
+
+const SAMPLE_TEXT = `
+Modern CI/CD pipelines rely on deterministic builds and reproducible environments.
+A deployment may fail even when the application code is correct if the runtime,
+dependency graph, or container image differs from what engineers tested locally.
+
+Observability should combine logs, metrics, and traces rather than treating them
+as separate debugging tools. Metrics show that something is wrong, logs provide
+local detail, and traces explain how a request moved across services.
+
+Schema validation is especially important in LLM systems. A response may sound
+reasonable to a human reader but still break automation if the JSON structure,
+field names, or enum values do not match the downstream contract.
+
+Cross-model verification can reduce self-confirmation bias. When one model
+produces a translation and a different provider family performs the
+backtranslation, semantic drift becomes easier to detect.
+`.trim()
+
+// ---------------------------------------------------------------------------
+// Zod schemas
+// ---------------------------------------------------------------------------
+
+const ParagraphInput = z.object({
+  index: z.number().int().positive(),
+  original: z.string(),
+})
+type ParagraphInput = z.infer<typeof ParagraphInput>
+
+const TranslationBatch = z.object({
+  target_language: z.string(),
+  items: z.array(
+    z.object({
+      index: z.number().int().positive(),
+      translation: z.string(),
+    }),
+  ),
+})
+type TranslationBatch = z.infer<typeof TranslationBatch>
+
+const BacktranslationBatch = z.object({
+  items: z.array(
+    z.object({
+      index: z.number().int().positive(),
+      backtranslation: z.string(),
+    }),
+  ),
+})
+type BacktranslationBatch = z.infer<typeof BacktranslationBatch>
+
+const DriftRow = z.object({
+  original: z.string(),
+  translation: z.string(),
+  backtranslation: z.string(),
+  drift_severity: z.enum(['none', 'minor', 'major']),
+  notes: z.string(),
+})
+type DriftRow = z.infer<typeof DriftRow>
+
+const DriftTable = z.array(DriftRow)
+type DriftTable = z.infer<typeof DriftTable>
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+function buildAgent(config: AgentConfig): Agent {
+  const registry = new ToolRegistry()
+  registerBuiltInTools(registry)
+  const executor = new ToolExecutor(registry)
+  return new Agent(config, registry, executor)
+}
+
+function splitParagraphs(text: string): ParagraphInput[] {
+  return text
+    .split(/\n\s*\n/)
+    .map((p, i) => ({
+      index: i + 1,
+      original: p.trim(),
+    }))
+    .filter((p) => p.original.length > 0)
+}
+
+// ---------------------------------------------------------------------------
+// Provider selection
+// ---------------------------------------------------------------------------
+
+const hasAnthropic = Boolean(process.env.ANTHROPIC_API_KEY)
+const hasOpenAI = Boolean(process.env.OPENAI_API_KEY)
+const hasGemini = Boolean(process.env.GEMINI_API_KEY)
+
+if (!hasAnthropic || (!hasGemini && !hasOpenAI)) {
+  console.log(
+    '[skip] This example needs ANTHROPIC_API_KEY plus GEMINI_API_KEY or OPENAI_API_KEY.',
+  )
+  process.exit(0)
+}
+
+// Prefer native Gemini when GEMINI_API_KEY is available.
+// Fall back to OpenAI otherwise.
+const backProvider: 'gemini' | 'openai' = hasGemini ? 'gemini' : 'openai'
+
+const backModel =
+  backProvider === 'gemini'
+    ? 'gemini-2.5-pro'
+    : (process.env.OPENAI_MODEL || 'gpt-5.4')
+    
+// ---------------------------------------------------------------------------
+// Agent configs
+// ---------------------------------------------------------------------------
+
+// Agent A ---------------------------------------------------------------
+// 用 Claude 做 “英文 -> 目标语言” 翻译
+const translatorConfig: AgentConfig = {
+  name: 'translator',
+  provider: 'anthropic',
+  model: 'claude-sonnet-4-6',
+  systemPrompt: `You are Agent A, a technical translator.
+
+Translate English paragraphs into Simplified Chinese.
+Preserve meaning, terminology, paragraph boundaries, and index numbers.
+Do not merge paragraphs.
+Return JSON only, matching the schema exactly.`,
+  maxTurns: 1,
+  temperature: 0,
+  outputSchema: TranslationBatch,
+}
+
+// Agent B ---------------------------------------------------------------
+// 用不同 provider 家族做 “目标语言 -> 英文” 回译
+const backtranslatorConfig: AgentConfig = {
+  name: 'backtranslator',
+  provider: backProvider,
+  model: backModel,
+  baseURL: backProvider === 'openai' ? process.env.OPENAI_BASE_URL : undefined,
+  systemPrompt: `You are Agent B, a back-translation specialist.
+
+Back-translate the provided Simplified Chinese paragraphs into English.
+Preserve meaning as literally as possible.
+Do not merge paragraphs.
+Keep the same index numbers.
+Return JSON only, matching the schema exactly.`,
+  maxTurns: 1,
+  temperature: 0,
+  outputSchema: BacktranslationBatch,
+}
+// Agent C ---------------------------------------------------------------
+// 比较原文和回译文，判断语义漂移
+const reviewerConfig: AgentConfig = {
+  name: 'reviewer',
+  provider: 'anthropic',
+  model: 'claude-sonnet-4-6',
+  systemPrompt: `You are Agent C, a semantic drift reviewer.
+
+You will receive:
+- the original English paragraph
+- the translated paragraph
+- the backtranslated English paragraph
+
+For each paragraph, judge drift_severity using only:
+- none: meaning preserved
+- minor: slight wording drift, but no important meaning change
+- major: material semantic change, omission, contradiction, or mistranslation
+
+Return JSON only.
+The final output must be an array where each item contains:
+original, translation, backtranslation, drift_severity, notes.`,
+  maxTurns: 1,
+  temperature: 0,
+  outputSchema: DriftTable,
+}
+
+// ---------------------------------------------------------------------------
+// Build agents
+// ---------------------------------------------------------------------------
+
+const translator = buildAgent(translatorConfig)
+const backtranslator = buildAgent(backtranslatorConfig)
+const reviewer = buildAgent(reviewerConfig)
+
+const pool = new AgentPool(1)
+pool.add(translator)
+pool.add(backtranslator)
+pool.add(reviewer)
+
+// ---------------------------------------------------------------------------
+// Run pipeline
+// ---------------------------------------------------------------------------
+
+const paragraphs = splitParagraphs(SAMPLE_TEXT)
+
+console.log('Translation + Backtranslation Quality Check')
+console.log('='.repeat(60))
+console.log(`Paragraphs: ${paragraphs.length}`)
+console.log(`Translator provider: anthropic (claude-sonnet-4-6)`)
+console.log(`Backtranslator provider: ${backProvider} (${backModel})`)
+console.log()
+
+// Step 1: Agent A translates
+console.log('[1/3] Agent A translating EN -> zh-CN...\n')
+
+const translationPrompt = `Target language: Simplified Chinese
+
+Translate the following paragraphs.
+Return exactly one translated item per paragraph.
+
+Input:
+${JSON.stringify(paragraphs, null, 2)}`
+const translationResult = await pool.run('translator', translationPrompt)
+
+if (!translationResult.success || !translationResult.structured) {
+  console.error('Agent A failed:', translationResult.output)
+  process.exit(1)
+}
+
+const translated = translationResult.structured as TranslationBatch
+
+// Step 2: Agent B back-translates
+console.log('[2/3] Agent B back-translating zh-CN -> EN...\n')
+
+const backtranslationPrompt = `Back-translate the following paragraphs into English.
+Keep the same indexes.
+
+Input:
+${JSON.stringify(translated.items, null, 2)}`
+const backtranslationResult = await pool.run('backtranslator', backtranslationPrompt)
+
+if (!backtranslationResult.success || !backtranslationResult.structured) {
+  console.error('Agent B failed:', backtranslationResult.output)
+  process.exit(1)
+}
+
+const backtranslated = backtranslationResult.structured as BacktranslationBatch
+
+// Step 3: Agent C reviews semantic drift
+console.log('[3/3] Agent C reviewing semantic drift...\n')
+
+const mergedInput = paragraphs.map((p) => ({
+  index: p.index,
+  original: p.original,
+  translation: translated.items.find((x) => x.index === p.index)?.translation ?? '',
+  backtranslation:
+    backtranslated.items.find((x) => x.index === p.index)?.backtranslation ?? '',
+}))
+
+const reviewPrompt = `Compare the original English against the backtranslated English.
+
+Important:
+- Evaluate semantic drift paragraph by paragraph
+- Do not judge style differences as major unless meaning changed
+- Return only the final JSON array
+
+Input:
+${JSON.stringify(mergedInput, null, 2)}`
+const reviewResult = await pool.run('reviewer', reviewPrompt)
+
+if (!reviewResult.success || !reviewResult.structured) {
+  console.error('Agent C failed:', reviewResult.output)
+  process.exit(1)
+}
+
+const driftTable = reviewResult.structured as DriftTable
+
+// ---------------------------------------------------------------------------
+// Final output
+// ---------------------------------------------------------------------------
+
+console.log('='.repeat(60))
+console.log('FINAL DRIFT TABLE')
+console.log('='.repeat(60))
+console.log(JSON.stringify(driftTable, null, 2))
+console.log()
+
+console.log('Token Usage Summary')
+console.log('-'.repeat(60))
+console.log(
+  `Agent A (translator)    — input: ${translationResult.tokenUsage.input_tokens}, output: ${translationResult.tokenUsage.output_tokens}`,
+)
+console.log(
+  `Agent B (backtranslator) — input: ${backtranslationResult.tokenUsage.input_tokens}, output: ${backtranslationResult.tokenUsage.output_tokens}`,
+)
+console.log(
+  `Agent C (reviewer)      — input: ${reviewResult.tokenUsage.input_tokens}, output: ${reviewResult.tokenUsage.output_tokens}`,
+)
+
+const totalInput =
+  translationResult.tokenUsage.input_tokens +
+  backtranslationResult.tokenUsage.input_tokens +
+  reviewResult.tokenUsage.input_tokens
+
+const totalOutput =
+  translationResult.tokenUsage.output_tokens +
+  backtranslationResult.tokenUsage.output_tokens +
+  reviewResult.tokenUsage.output_tokens
+
+console.log('-'.repeat(60))
+console.log(`TOTAL                   — input: ${totalInput}, output: ${totalOutput}`)
+console.log('\nDone.')
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