diff --git a/libs/extractor-api-lib/tests/modality_contract_test.py b/libs/extractor-api-lib/tests/modality_contract_test.py
new file mode 100644
index 00000000..134c5cd4
--- /dev/null
+++ b/libs/extractor-api-lib/tests/modality_contract_test.py
@@ -0,0 +1,84 @@
+"""Contract tests for modality metadata consistency across extraction paths."""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+from typing import Any
+
+import pytest
+
+
+CONTRACT_DIR = Path(__file__).parent / "test_data" / "modality_contract"
+ALLOWED_MODALITIES = {"TEXT", "TABLE", "IMAGE"}
+
+
+def _load_fixture(path: Path) -> dict[str, Any]:
+    with path.open("r", encoding="utf-8") as handle:
+        return json.load(handle)
+
+
+def _validate_piece(piece: dict[str, Any]) -> list[str]:
+    errors: list[str] = []
+
+    modality = piece.get("type")
+    metadata = piece.get("metadata")
+    page_content = piece.get("page_content")
+
+    if modality not in ALLOWED_MODALITIES:
+        errors.append("type must be one of TEXT/TABLE/IMAGE")
+
+    if not isinstance(page_content, str):
+        errors.append("page_content must be a string")
+
+    if not isinstance(metadata, dict):
+        errors.append("metadata must be an object")
+        return errors
+
+    required_common = ("document", "page", "id", "related")
+    for key in required_common:
+        if key not in metadata:
+            errors.append(f'metadata missing required key: "{key}"')
+
+    if "related" in metadata and not isinstance(metadata.get("related"), list):
+        errors.append('metadata["related"] must be a list')
+
+    if modality == "IMAGE":
+        has_legacy = bool(metadata.get("base64_image"))
+        has_image_url = bool(metadata.get("image_url"))
+        has_image_ref = bool(metadata.get("image_ref"))
+        has_reference = has_image_url or has_image_ref
+
+        if not (has_legacy or has_reference):
+            errors.append("IMAGE metadata must contain base64_image or image_url/image_ref")
+
+        if has_reference and not metadata.get("image_mime"):
+            errors.append("IMAGE metadata with image_url/image_ref must include image_mime")
+
+    return errors
+
+
+@pytest.mark.parametrize(
+    "fixture_path",
+    sorted(CONTRACT_DIR.glob("*.json")),
+    ids=lambda p: p.stem,
+)
+def test_modality_contract_fixture(fixture_path: Path):
+    """Validate every contract fixture against the shared modality schema."""
+    fixture = _load_fixture(fixture_path)
+    piece = fixture["piece"]
+    valid = bool(fixture["valid"])
+
+    errors = _validate_piece(piece)
+
+    if valid:
+        assert errors == [], f"Fixture {fixture_path.name} failed contract checks: {errors}"
+    else:
+        assert errors, f"Fixture {fixture_path.name} was expected to fail but passed."
+
+
+def test_modality_contract_fixture_names_are_unique():
+    """Ensure fixture names stay unique for clear test diagnostics."""
+    fixtures = [_load_fixture(path) for path in sorted(CONTRACT_DIR.glob("*.json"))]
+    names = [fixture.get("name") for fixture in fixtures]
+    assert len(names) == len(set(names))
diff --git a/libs/extractor-api-lib/tests/test_data/modality_contract/image_invalid_missing_payload.json b/libs/extractor-api-lib/tests/test_data/modality_contract/image_invalid_missing_payload.json
new file mode 100644
index 00000000..5ce6f42a
--- /dev/null
+++ b/libs/extractor-api-lib/tests/test_data/modality_contract/image_invalid_missing_payload.json
@@ -0,0 +1,14 @@
+{
+  "name": "image_invalid_missing_payload",
+  "valid": false,
+  "piece": {
+    "type": "IMAGE",
+    "page_content": "caption only",
+    "metadata": {
+      "document": "file:image.png",
+      "page": 1,
+      "id": "img-bad-1",
+      "related": []
+    }
+  }
+}
diff --git a/libs/extractor-api-lib/tests/test_data/modality_contract/image_legacy_base64_valid.json b/libs/extractor-api-lib/tests/test_data/modality_contract/image_legacy_base64_valid.json
new file mode 100644
index 00000000..5b0a5fe3
--- /dev/null
+++ b/libs/extractor-api-lib/tests/test_data/modality_contract/image_legacy_base64_valid.json
@@ -0,0 +1,15 @@
+{
+  "name": "image_legacy_base64_valid",
+  "valid": true,
+  "piece": {
+    "type": "IMAGE",
+    "page_content": "diagram describing architecture",
+    "metadata": {
+      "document": "file:diagram.png",
+      "page": 1,
+      "id": "img-legacy-1",
+      "related": [],
+      "base64_image": "iVBORw0KGgoAAAANSUhEUgAA..."
+    }
+  }
+}
diff --git a/libs/extractor-api-lib/tests/test_data/modality_contract/image_reference_valid.json b/libs/extractor-api-lib/tests/test_data/modality_contract/image_reference_valid.json
new file mode 100644
index 00000000..d3524b7f
--- /dev/null
+++ b/libs/extractor-api-lib/tests/test_data/modality_contract/image_reference_valid.json
@@ -0,0 +1,16 @@
+{
+  "name": "image_reference_valid",
+  "valid": true,
+  "piece": {
+    "type": "IMAGE",
+    "page_content": "OCR fallback text",
+    "metadata": {
+      "document": "file:screenshot.jpg",
+      "page": 1,
+      "id": "img-ref-1",
+      "related": [],
+      "image_ref": "s3://documents/screenshot.jpg",
+      "image_mime": "image/jpeg"
+    }
+  }
+}
diff --git a/libs/extractor-api-lib/tests/test_data/modality_contract/table_valid.json b/libs/extractor-api-lib/tests/test_data/modality_contract/table_valid.json
new file mode 100644
index 00000000..f86d0134
--- /dev/null
+++ b/libs/extractor-api-lib/tests/test_data/modality_contract/table_valid.json
@@ -0,0 +1,14 @@
+{
+  "name": "table_valid",
+  "valid": true,
+  "piece": {
+    "type": "TABLE",
+    "page_content": "| A | B |\n| --- | --- |\n| 1 | 2 |",
+    "metadata": {
+      "document": "file:sample.csv",
+      "page": 1,
+      "id": "tbl-123",
+      "related": ["chunk-1"]
+    }
+  }
+}
diff --git a/libs/extractor-api-lib/tests/test_data/modality_contract/text_valid.json b/libs/extractor-api-lib/tests/test_data/modality_contract/text_valid.json
new file mode 100644
index 00000000..510a80b5
--- /dev/null
+++ b/libs/extractor-api-lib/tests/test_data/modality_contract/text_valid.json
@@ -0,0 +1,14 @@
+{
+  "name": "text_valid",
+  "valid": true,
+  "piece": {
+    "type": "TEXT",
+    "page_content": "example body text",
+    "metadata": {
+      "document": "file:sample.txt",
+      "page": 1,
+      "id": "abc123",
+      "related": []
+    }
+  }
+}