diff --git a/data-pipeline/tests/fixtures/annotated.fixture.json b/data-pipeline/tests/fixtures/annotated.fixture.json
new file mode 100644
index 0000000..f941bd0
--- /dev/null
+++ b/data-pipeline/tests/fixtures/annotated.fixture.json
@@ -0,0 +1,170 @@
+[
+  {
+    "_fixture": "noun_with_cefr_vote",
+    "source_id": "ili:i100955",
+    "pos": "noun",
+    "translations": { "en": ["grain"], "de": ["Korn", "Kornbrand"] },
+    "glosses": { "en": ["a cereal grass"], "de": ["ein Getreidegras"] },
+    "examples": {
+      "en": [
+        { "text": "wheat is a grain that is grown in Kansas", "source": "omw" }
+      ]
+    },
+    "votes": { "en": { "grain": { "cefr_source": "B1" } } }
+  },
+  {
+    "_fixture": "verb_no_votes_no_translations",
+    "source_id": "ili:i21779",
+    "pos": "verb",
+    "translations": { "en": ["respire"] },
+    "glosses": {
+      "en": [
+        "undergo the biomedical and metabolic processes of respiration by taking up oxygen and producing carbon monoxide"
+      ]
+    },
+    "examples": {},
+    "votes": {}
+  },
+  {
+    "_fixture": "verb_with_cefr_vote_all_languages",
+    "source_id": "ili:i21778",
+    "pos": "verb",
+    "translations": {
+      "en": ["breathe", "take a breath", "respire", "suspire"],
+      "it": ["respirare"],
+      "es": ["aspirar", "respirar"],
+      "de": ["Luft holen", "hauchen", "Luft bekommen", "Luft kriegen", "atmen"],
+      "fr": ["inspirer", "respirer"]
+    },
+    "glosses": {
+      "en": ["draw air into, and expel out of, the lungs"],
+      "de": ["Luft in die Lunge saugen und aus ihr ausstoßen"]
+    },
+    "examples": {
+      "en": [
+        {
+          "text": "I can breathe better when the air is clean",
+          "source": "omw"
+        },
+        { "text": "The patient is respiring", "source": "omw" }
+      ]
+    },
+    "votes": { "en": { "breathe": { "cefr_source": "A1" } } }
+  },
+  {
+    "_fixture": "adjective_all_languages_multiple_translations",
+    "source_id": "ili:i10007",
+    "pos": "adjective",
+    "translations": {
+      "en": ["possible"],
+      "it": [
+        "attuabile",
+        "effettuabile",
+        "eseguibile",
+        "fattibile",
+        "operabile",
+        "possibile",
+        "producibile",
+        "realizzabile"
+      ],
+      "es": ["posible"],
+      "de": [
+        "möglich",
+        "denkbar",
+        "eventuell",
+        "möglicherweise",
+        "allfällig",
+        "etwaig",
+        "gegebenenfalls",
+        "eventuell"
+      ],
+      "fr": ["possible", "éventuel"]
+    },
+    "glosses": {
+      "en": ["capable of happening or existing"],
+      "de": ["in der Lage, zu geschehen oder zu existieren"]
+    },
+    "examples": {
+      "en": [
+        { "text": "a breakthrough may be possible next year", "source": "omw" },
+        { "text": "anything is possible", "source": "omw" },
+        { "text": "warned of possible consequences", "source": "omw" }
+      ]
+    },
+    "votes": { "en": { "possible": { "cefr_source": "A2" } } }
+  },
+  {
+    "_fixture": "adjective_multiple_de_votes_cefr_examples",
+    "source_id": "ili:i10000",
+    "pos": "adjective",
+    "translations": {
+      "en": ["negative"],
+      "de": [
+        "dürftig",
+        "zu wünschen übrig lassen",
+        "schlecht",
+        "widrig",
+        "ungut",
+        "lausig",
+        "negativ",
+        "von Nachteil",
+        "schädlich",
+        "nachteilig",
+        "ungünstig"
+      ],
+      "fr": ["négatif", "strictement négatif"]
+    },
+    "glosses": { "en": ["less than zero"], "de": ["kleiner als Null"] },
+    "examples": {
+      "en": [{ "text": "a negative number", "source": "omw" }],
+      "de": [
+        { "text": "Die Beweise waren dürftig.", "source": "cefr" },
+        { "text": "Das Wetter ist heute schlecht.", "source": "cefr" },
+        {
+          "text": "Trotz widriger Umstände haben sie es geschafft.",
+          "source": "cefr"
+        },
+        {
+          "text": "Er hatte ein ungutes Gefühl bei der Sache.",
+          "source": "cefr"
+        },
+        { "text": "Er hat eine sehr negative Einstellung.", "source": "cefr" },
+        {
+          "text": "Rauchen ist schädlich für die Gesundheit.",
+          "source": "cefr"
+        },
+        {
+          "text": "Diese Entscheidung könnte nachteilig sein.",
+          "source": "cefr"
+        },
+        {
+          "text": "Das Wetter ist heute ungünstig für einen Ausflug.",
+          "source": "cefr"
+        }
+      ]
+    },
+    "votes": {
+      "de": {
+        "dürftig": { "cefr_source": "C1" },
+        "schlecht": { "cefr_source": "A1" },
+        "widrig": { "cefr_source": "C1" },
+        "ungut": { "cefr_source": "B2" },
+        "negativ": { "cefr_source": "A2" },
+        "schädlich": { "cefr_source": "B1" },
+        "nachteilig": { "cefr_source": "B1" },
+        "ungünstig": { "cefr_source": "B2" }
+      }
+    }
+  },
+  {
+    "_fixture": "adverb_no_votes",
+    "source_id": "ili:i18157",
+    "pos": "adverb",
+    "translations": { "en": ["a cappella"], "es": ["a capella"] },
+    "glosses": { "en": ["without musical accompaniment"] },
+    "examples": {
+      "en": [{ "text": "they performed a cappella", "source": "omw" }]
+    },
+    "votes": {}
+  }
+]
diff --git a/data-pipeline/tests/fixtures/conflicts.fixture.json b/data-pipeline/tests/fixtures/conflicts.fixture.json
new file mode 100644
index 0000000..37f5111
--- /dev/null
+++ b/data-pipeline/tests/fixtures/conflicts.fixture.json
@@ -0,0 +1,4 @@
+[
+  { "word": "macht", "pos": "noun", "language": "de", "levels": ["A2", "B1"] },
+  { "word": "bleiche", "pos": "noun", "language": "de", "levels": ["B2", "B1"] }
+]
diff --git a/data-pipeline/tests/validation/stage-1.validation.test.ts b/data-pipeline/tests/validation/stage-1.validation.test.ts
new file mode 100644
index 0000000..287be9e
--- /dev/null
+++ b/data-pipeline/tests/validation/stage-1.validation.test.ts
@@ -0,0 +1,143 @@
+import fs from "node:fs/promises";
+import path from "node:path";
+import { describe, it, expect } from "vitest";
+import { SUPPORTED_POS, SUPPORTED_LANGUAGE_CODES } from "@lila/shared";
+import type { SupportedPos, SupportedLanguageCode } from "@lila/shared";
+
+// ── Types ─────────────────────────────────────────────────────────────────────
+
+type OmwRecord = {
+  source_id: string;
+  pos: SupportedPos;
+  translations: Partial<Record<SupportedLanguageCode, string[]>>;
+  glosses: Partial<Record<SupportedLanguageCode, string[]>>;
+  examples: Partial<Record<SupportedLanguageCode, string[]>>;
+};
+
+// ── Paths ─────────────────────────────────────────────────────────────────────
+
+const OMW_PATH = path.resolve("stage-1-extract/output/omw.json");
+
+// ── Helpers ───────────────────────────────────────────────────────────────────
+
+function isValidSourceId(id: string): boolean {
+  return /^ili:i\d+$/.test(id);
+}
+
+// ── Tests ─────────────────────────────────────────────────────────────────────
+
+describe("stage 1 — omw.json validation", () => {
+  let records: OmwRecord[];
+
+  it("file exists and is valid JSON", async () => {
+    const raw = await fs.readFile(OMW_PATH, "utf-8");
+    records = JSON.parse(raw) as OmwRecord[];
+    expect(records).toBeDefined();
+  });
+
+  it("is a non-empty array", async () => {
+    const raw = await fs.readFile(OMW_PATH, "utf-8");
+    records = JSON.parse(raw) as OmwRecord[];
+    expect(Array.isArray(records)).toBe(true);
+    expect(records.length).toBeGreaterThan(0);
+  });
+
+  it("every record has required fields", async () => {
+    const raw = await fs.readFile(OMW_PATH, "utf-8");
+    records = JSON.parse(raw) as OmwRecord[];
+
+    const errors: string[] = [];
+
+    for (const record of records) {
+      if (!record.source_id) {
+        errors.push(`missing source_id`);
+        continue;
+      }
+      if (!record.pos) errors.push(`${record.source_id}: missing pos`);
+      if (!record.translations)
+        errors.push(`${record.source_id}: missing translations`);
+      if (!record.glosses) errors.push(`${record.source_id}: missing glosses`);
+      if (!record.examples)
+        errors.push(`${record.source_id}: missing examples`);
+    }
+
+    expect(errors, `\n${errors.join("\n")}`).toHaveLength(0);
+  });
+
+  it("every source_id matches ili:i{number} pattern", async () => {
+    const raw = await fs.readFile(OMW_PATH, "utf-8");
+    records = JSON.parse(raw) as OmwRecord[];
+
+    const errors: string[] = [];
+
+    for (const record of records) {
+      if (!isValidSourceId(record.source_id)) {
+        errors.push(`invalid source_id: ${record.source_id}`);
+      }
+    }
+
+    expect(errors, `\n${errors.join("\n")}`).toHaveLength(0);
+  });
+
+  it("every source_id is unique", async () => {
+    const raw = await fs.readFile(OMW_PATH, "utf-8");
+    records = JSON.parse(raw) as OmwRecord[];
+
+    const seen = new Set<string>();
+    const errors: string[] = [];
+
+    for (const record of records) {
+      if (seen.has(record.source_id)) {
+        errors.push(`duplicate source_id: ${record.source_id}`);
+      }
+      seen.add(record.source_id);
+    }
+
+    expect(errors, `\n${errors.join("\n")}`).toHaveLength(0);
+  });
+
+  it("every pos is a valid supported value", async () => {
+    const raw = await fs.readFile(OMW_PATH, "utf-8");
+    records = JSON.parse(raw) as OmwRecord[];
+
+    const errors: string[] = [];
+    const validPos = new Set(SUPPORTED_POS);
+
+    for (const record of records) {
+      if (!validPos.has(record.pos)) {
+        errors.push(`${record.source_id}: invalid pos "${record.pos}"`);
+      }
+    }
+
+    expect(errors, `\n${errors.join("\n")}`).toHaveLength(0);
+  });
+
+  it("every record has at least one translation in at least one language", async () => {
+    const raw = await fs.readFile(OMW_PATH, "utf-8");
+    records = JSON.parse(raw) as OmwRecord[];
+
+    const errors: string[] = [];
+    const validLangs = new Set(SUPPORTED_LANGUAGE_CODES);
+
+    for (const record of records) {
+      const langs = Object.keys(record.translations) as SupportedLanguageCode[];
+
+      if (langs.length === 0) {
+        errors.push(`${record.source_id}: no translations`);
+        continue;
+      }
+
+      for (const lang of langs) {
+        if (!validLangs.has(lang)) {
+          errors.push(`${record.source_id}: unsupported language "${lang}"`);
+        }
+        const words = record.translations[lang] ?? [];
+        if (words.length === 0) {
+          errors.push(`${record.source_id}: empty translations for "${lang}"`);
+        }
+      }
+    }
+
+    expect(errors, `\n${errors.join("\n")}`).toHaveLength(0);
+  });
+});
diff --git a/data-pipeline/tests/validation/stage-2.validation.test.ts b/data-pipeline/tests/validation/stage-2.validation.test.ts
new file mode 100644
index 0000000..b50fcf5
--- /dev/null
+++ b/data-pipeline/tests/validation/stage-2.validation.test.ts
@@ -0,0 +1,218 @@
+import fs from "node:fs/promises";
+import path from "node:path";
+import { describe, it, expect, beforeAll } from "vitest";
+import {
+  SUPPORTED_POS,
+  SUPPORTED_LANGUAGE_CODES,
+  CEFR_LEVELS,
+} from "@lila/shared";
+import type { SupportedPos, SupportedLanguageCode } from "@lila/shared";
+
+// ── Types ─────────────────────────────────────────────────────────────────────
+
+type Example = { text: string; source: "omw" | "cefr" };
+
+type AnnotatedRecord = {
+  source_id: string;
+  pos: SupportedPos;
+  translations: Partial<Record<SupportedLanguageCode, string[]>>;
+  glosses: Partial<Record<SupportedLanguageCode, string[]>>;
+  examples: Partial<Record<SupportedLanguageCode, Example[]>>;
+  votes: Partial<
+    Record<SupportedLanguageCode, Record<string, { cefr_source: string }>>
+  >;
+};
+
+type ConflictEntry = {
+  word: string;
+  pos: string;
+  language: SupportedLanguageCode;
+  levels: string[];
+};
+
+// ── Paths ─────────────────────────────────────────────────────────────────────
+
+const OUTPUT_DIR = path.resolve("stage-2-annotate/output");
+
+// ── Tests ─────────────────────────────────────────────────────────────────────
+
+describe("stage 2 — annotated output validation", () => {
+  const recordsByLang = new Map<SupportedLanguageCode, AnnotatedRecord[]>();
+  let conflicts: ConflictEntry[] = [];
+
+  beforeAll(async () => {
+    for (const lang of SUPPORTED_LANGUAGE_CODES) {
+      const raw = await fs.readFile(
+        path.join(OUTPUT_DIR, `${lang}.json`),
+        "utf-8",
+      );
+      recordsByLang.set(lang, JSON.parse(raw) as AnnotatedRecord[]);
+    }
+    const raw = await fs.readFile(
+      path.join(OUTPUT_DIR, "conflicts.json"),
+      "utf-8",
+    );
+    conflicts = JSON.parse(raw) as ConflictEntry[];
+  }, 60_000);
+
+  it("all five language files exist", async () => {
+    const errors: string[] = [];
+
+    for (const lang of SUPPORTED_LANGUAGE_CODES) {
+      const filePath = path.join(OUTPUT_DIR, `${lang}.json`);
+      try {
+        await fs.access(filePath);
+      } catch {
+        errors.push(`missing file: ${lang}.json`);
+      }
+    }
+
+    expect(errors, `\n${errors.join("\n")}`).toHaveLength(0);
+  });
+
+  it("conflicts.json exists", async () => {
+    const filePath = path.join(OUTPUT_DIR, "conflicts.json");
+    await expect(fs.access(filePath)).resolves.toBeUndefined();
+  });
+
+  it("every language file is a non-empty array", () => {
+    const errors: string[] = [];
+
+    for (const lang of SUPPORTED_LANGUAGE_CODES) {
+      const records = recordsByLang.get(lang)!;
+      if (!Array.isArray(records)) {
+        errors.push(`${lang}.json: not an array`);
+      } else if (records.length === 0) {
+        errors.push(`${lang}.json: empty array`);
+      }
+    }
+
+    expect(errors, `\n${errors.join("\n")}`).toHaveLength(0);
+  });
+
+  it("every record has required fields", () => {
+    const errors: string[] = [];
+
+    for (const lang of SUPPORTED_LANGUAGE_CODES) {
+      const records = recordsByLang.get(lang)!;
+
+      for (const record of records) {
+        if (!record.source_id) {
+          errors.push(`${lang}: record missing source_id`);
+          continue;
+        }
+        if (!record.pos)
+          errors.push(`${lang} ${record.source_id}: missing pos`);
+        if (!record.translations)
+          errors.push(`${lang} ${record.source_id}: missing translations`);
+        if (!record.glosses)
+          errors.push(`${lang} ${record.source_id}: missing glosses`);
+        if (record.examples === undefined)
+          errors.push(`${lang} ${record.source_id}: missing examples`);
+        if (record.votes === undefined)
+          errors.push(`${lang} ${record.source_id}: missing votes`);
+      }
+    }
+
+    expect(errors, `\n${errors.join("\n")}`).toHaveLength(0);
+  });
+
+  it("every pos is a valid supported value", () => {
+    const errors: string[] = [];
+    const validPos = new Set(SUPPORTED_POS);
+
+    for (const lang of SUPPORTED_LANGUAGE_CODES) {
+      const records = recordsByLang.get(lang)!;
+
+      for (const record of records) {
+        if (!validPos.has(record.pos)) {
+          errors.push(
+            `${lang} ${record.source_id}: invalid pos "${record.pos}"`,
+          );
+        }
+      }
+    }
+
+    expect(errors, `\n${errors.join("\n")}`).toHaveLength(0);
+  });
+
+  it("every example has text and a valid source", () => {
+    const errors: string[] = [];
+    const validSources = new Set(["omw", "cefr"]);
+
+    for (const lang of SUPPORTED_LANGUAGE_CODES) {
+      const records = recordsByLang.get(lang)!;
+
+      for (const record of records) {
+        for (const [l, examples] of Object.entries(record.examples)) {
+          for (const example of examples) {
+            if (!example.text) {
+              errors.push(
+                `${lang} ${record.source_id} (${l}): example missing text`,
+              );
+            }
+            if (!validSources.has(example.source)) {
+              errors.push(
+                `${lang} ${record.source_id} (${l}): invalid example source "${example.source}"`,
+              );
+            }
+          }
+        }
+      }
+    }
+
+    expect(errors, `\n${errors.join("\n")}`).toHaveLength(0);
+  });
+
+  it("every cefr_source vote is a valid CEFR level", () => {
+    const errors: string[] = [];
+    const validLevels = new Set(CEFR_LEVELS);
+
+    for (const lang of SUPPORTED_LANGUAGE_CODES) {
+      const records = recordsByLang.get(lang)!;
+
+      for (const record of records) {
+        for (const [l, langVotes] of Object.entries(record.votes)) {
+          for (const [word, vote] of Object.entries(langVotes ?? {})) {
+            if (
+              !validLevels.has(vote.cefr_source as (typeof CEFR_LEVELS)[number])
+            ) {
+              errors.push(
+                `${lang} ${record.source_id} (${l} — "${word}"): invalid cefr_source "${vote.cefr_source}"`,
+              );
+            }
+          }
+        }
+      }
+    }
+
+    expect(errors, `\n${errors.join("\n")}`).toHaveLength(0);
+  });
+
+  it("conflicts.json entries have required fields and valid CEFR levels", () => {
+    const errors: string[] = [];
+    const validLevels = new Set(CEFR_LEVELS);
+    const validLangs = new Set(SUPPORTED_LANGUAGE_CODES);
+
+    for (const entry of conflicts) {
+      if (!entry.word) errors.push(`conflict missing word`);
+      if (!entry.pos) errors.push(`conflict missing pos`);
+      if (!entry.language) {
+        errors.push(`conflict missing language`);
+      } else if (!validLangs.has(entry.language)) {
+        errors.push(`conflict invalid language "${entry.language}"`);
+      }
+      if (!Array.isArray(entry.levels) || entry.levels.length < 2) {
+        errors.push(`${entry.word}: levels must have at least 2 entries`);
+      } else {
+        for (const level of entry.levels) {
+          if (!validLevels.has(level as (typeof CEFR_LEVELS)[number])) {
+            errors.push(`${entry.word}: invalid level "${level}"`);
+          }
+        }
+      }
+    }
+
+    expect(errors, `\n${errors.join("\n")}`).toHaveLength(0);
+  });
+});
diff --git a/data-pipeline/vitest.config.ts b/data-pipeline/vitest.config.ts
index bdc68ba..cafc658 100644
--- a/data-pipeline/vitest.config.ts
+++ b/data-pipeline/vitest.config.ts
@@ -6,5 +6,6 @@ export default defineConfig({
     globals: true,
     include: ["tests/**/*.test.ts"],
     exclude: ["**/dist/**", "**/node_modules/**"],
+    testTimeout: 60_000,
   },
 });