diff --git a/ml/serving/tests/test_schemas_and_consumer.py b/ml/serving/tests/test_schemas_and_consumer.py
new file mode 100644
index 0000000..3a06415
--- /dev/null
+++ b/ml/serving/tests/test_schemas_and_consumer.py
@@ -0,0 +1,169 @@
+"""
+Tests for schemas.py and nats_consumer._handle.
+"""
+import json
+import pytest
+import tempfile
+from pathlib import Path
+from pydantic import ValidationError
+from unittest.mock import AsyncMock
+
+from schemas import (
+    TaskSyncedPayload,
+    TipServedPayload,
+    TipFeedbackPayload,
+    TipRewardFailedPayload,
+    IntegrationTokenExpiredPayload,
+)
+from nats_consumer import _handle, _sync_meta_path
+
+
+# ── Schema validation ─────────────────────────────────────────────────────────
+
+class TestTaskSyncedPayload:
+    def test_valid(self):
+        p = TaskSyncedPayload.model_validate(
+            {"userId": "u1", "source": "todoist", "count": 5, "syncedAt": "2026-04-25T10:00:00Z"}
+        )
+        assert p.userId == "u1"
+        assert p.count == 5
+
+    def test_missing_field_raises(self):
+        with pytest.raises(ValidationError):
+            TaskSyncedPayload.model_validate({"userId": "u1", "source": "todoist"})
+
+    def test_wrong_type_raises(self):
+        with pytest.raises(ValidationError):
+            TaskSyncedPayload.model_validate(
+                {"userId": "u1", "source": "todoist", "count": "not-an-int", "syncedAt": "2026-04-25T10:00:00Z"}
+            )
+
+
+class TestTipFeedbackPayload:
+    def test_valid_without_dwell(self):
+        p = TipFeedbackPayload.model_validate(
+            {"userId": "u1", "tipId": "t1", "action": "done", "reward": 1.0, "createdAt": "2026-04-25T10:00:00Z"}
+        )
+        assert p.dwellMs is None
+
+    def test_valid_with_dwell(self):
+        p = TipFeedbackPayload.model_validate(
+            {"userId": "u1", "tipId": "t1", "action": "helpful", "reward": 0.5,
+             "dwellMs": 3200, "createdAt": "2026-04-25T10:00:00Z"}
+        )
+        assert p.dwellMs == 3200
+
+    def test_invalid_action_raises(self):
+        with pytest.raises(ValidationError):
+            TipFeedbackPayload.model_validate(
+                {"userId": "u1", "tipId": "t1", "action": "like", "reward": 1.0, "createdAt": "2026-04-25T10:00:00Z"}
+            )
+
+    def test_all_valid_actions(self):
+        for action in ("done", "dismiss", "snooze", "helpful", "not_helpful"):
+            p = TipFeedbackPayload.model_validate(
+                {"userId": "u1", "tipId": "t1", "action": action, "reward": 0.0, "createdAt": "2026-04-25T10:00:00Z"}
+            )
+            assert p.action == action
+
+
+class TestOtherPayloads:
+    def test_tip_served(self):
+        p = TipServedPayload.model_validate(
+            {"userId": "u1", "tipId": "t1", "policy": "egreedy-v2", "servedAt": "2026-04-25T10:00:00Z"}
+        )
+        assert p.policy == "egreedy-v2"
+
+    def test_tip_reward_failed(self):
+        p = TipRewardFailedPayload.model_validate(
+            {"userId": "u1", "tipId": "t1", "reward": 1.0, "attempts": 3,
+             "error": "timeout", "failedAt": "2026-04-25T10:00:00Z"}
+        )
+        assert p.attempts == 3
+
+    def test_integration_token_expired(self):
+        p = IntegrationTokenExpiredPayload.model_validate(
+            {"userId": "u1", "provider": "todoist", "detectedAt": "2026-04-25T10:00:00Z"}
+        )
+        assert p.provider == "todoist"
+
+
+# ── _handle behaviour ─────────────────────────────────────────────────────────
+
+TASK_SYNCED = {
+    "userId": "user-abc",
+    "source": "todoist",
+    "count": 7,
+    "syncedAt": "2026-04-25T10:00:00Z",
+}
+
+TIP_FEEDBACK = {
+    "userId": "user-abc",
+    "tipId": "tip-xyz",
+    "action": "done",
+    "reward": 1.0,
+    "dwellMs": 4200,
+    "createdAt": "2026-04-25T10:00:00Z",
+}
+
+
+class TestHandle:
+    @pytest.mark.asyncio
+    async def test_task_synced_writes_meta_file(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            state_dir = Path(tmp)
+            await _handle("signals.task.synced", TASK_SYNCED, state_dir)
+            meta_path = _sync_meta_path(state_dir, "user-abc")
+            assert meta_path.exists()
+            data = json.loads(meta_path.read_text())
+            assert data["task_count"] == 7
+            assert data["last_sync_ts"] == "2026-04-25T10:00:00Z"
+
+    @pytest.mark.asyncio
+    async def test_task_synced_bad_payload_raises(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            with pytest.raises(ValidationError):
+                await _handle("signals.task.synced", {"userId": "u1"}, Path(tmp))
+
+    @pytest.mark.asyncio
+    async def test_tip_feedback_valid_does_not_raise(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            # should log and return cleanly
+            await _handle("signals.tip.feedback", TIP_FEEDBACK, Path(tmp))
+
+    @pytest.mark.asyncio
+    async def test_tip_feedback_bad_action_raises(self):
+        bad = {**TIP_FEEDBACK, "action": "unknown"}
+        with tempfile.TemporaryDirectory() as tmp:
+            with pytest.raises(ValidationError):
+                await _handle("signals.tip.feedback", bad, Path(tmp))
+
+    @pytest.mark.asyncio
+    async def test_unhandled_subject_is_ignored(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            # should not raise for unknown subjects
+            await _handle("signals.something.new", {"any": "data"}, Path(tmp))
+
+    @pytest.mark.asyncio
+    async def test_make_handler_acks_on_success(self):
+        from nats_consumer import _make_handler
+        with tempfile.TemporaryDirectory() as tmp:
+            handler = _make_handler("signals", Path(tmp))
+            msg = AsyncMock()
+            msg.subject = "signals.task.synced"
+            msg.data = json.dumps(TASK_SYNCED).encode()
+            await handler(msg)
+            msg.ack.assert_awaited_once()
+            msg.nak.assert_not_awaited()
+
+    @pytest.mark.asyncio
+    async def test_make_handler_naks_on_validation_error(self):
+        from nats_consumer import _make_handler
+        with tempfile.TemporaryDirectory() as tmp:
+            handler = _make_handler("signals", Path(tmp))
+            msg = AsyncMock()
+            msg.subject = "signals.task.synced"
+            msg.data = json.dumps({"userId": "u1"}).encode()  # missing fields
+            await handler(msg)
+            msg.nak.assert_awaited_once()
+            msg.ack.assert_not_awaited()