diff --git a/tests/test_db.py b/tests/test_db.py
index 5cdf5ac..6514bbf 100644
--- a/tests/test_db.py
+++ b/tests/test_db.py
@@ -1,4 +1,4 @@
-"""Tests for core/db.py — schema and migration (KIN-071)."""
+"""Tests for core/db.py — schema and migration (KIN-071, KIN-073)."""
 
 import sqlite3
 import pytest
@@ -200,3 +200,86 @@ def test_migrate_operations_project_with_null_path():
     assert row["path"] is None
     assert row["project_type"] == "operations"
     conn.close()
+
+
+# ---------------------------------------------------------------------------
+# Schema KIN-073: acceptance_criteria в таблице tasks
+# ---------------------------------------------------------------------------
+
+class TestTasksAcceptanceCriteriaSchema:
+    """Колонка acceptance_criteria присутствует в таблице tasks."""
+
+    def test_schema_has_acceptance_criteria_column(self, conn):
+        assert "acceptance_criteria" in _cols(conn, "tasks")
+
+    def test_acceptance_criteria_defaults_to_null(self, conn):
+        """Создание задачи без acceptance_criteria — поле NULL (nullable)."""
+        conn.execute(
+            "INSERT INTO projects (id, name, path) VALUES ('p1', 'P', '/p')"
+        )
+        conn.execute(
+            "INSERT INTO tasks (id, project_id, title) VALUES ('t1', 'p1', 'My Task')"
+        )
+        conn.commit()
+        row = conn.execute(
+            "SELECT acceptance_criteria FROM tasks WHERE id='t1'"
+        ).fetchone()
+        assert row["acceptance_criteria"] is None
+
+    def test_create_task_with_acceptance_criteria_saves_field(self, conn):
+        """Создание задачи с acceptance_criteria — значение сохраняется в БД."""
+        conn.execute(
+            "INSERT INTO projects (id, name, path) VALUES ('p2', 'P', '/p')"
+        )
+        criteria = "Поле должно сохраняться. GET возвращает значение."
+        conn.execute(
+            "INSERT INTO tasks (id, project_id, title, acceptance_criteria)"
+            " VALUES ('t2', 'p2', 'Task with criteria', ?)",
+            (criteria,),
+        )
+        conn.commit()
+        row = conn.execute(
+            "SELECT acceptance_criteria FROM tasks WHERE id='t2'"
+        ).fetchone()
+        assert row["acceptance_criteria"] == criteria
+
+    def test_get_task_returns_acceptance_criteria(self, conn):
+        """SELECT задачи возвращает acceptance_criteria (критерий приёмки 3)."""
+        conn.execute(
+            "INSERT INTO projects (id, name, path) VALUES ('p3', 'P', '/p')"
+        )
+        conn.execute(
+            "INSERT INTO tasks (id, project_id, title, acceptance_criteria)"
+            " VALUES ('t3', 'p3', 'T', 'AC value')",
+        )
+        conn.commit()
+        row = conn.execute("SELECT * FROM tasks WHERE id='t3'").fetchone()
+        assert row["acceptance_criteria"] == "AC value"
+
+
+# ---------------------------------------------------------------------------
+# Migration KIN-073: _migrate добавляет acceptance_criteria в старую схему
+# ---------------------------------------------------------------------------
+
+def test_migrate_adds_acceptance_criteria_to_old_schema():
+    """_migrate добавляет acceptance_criteria в tasks если колонки нет."""
+    conn = _old_schema_conn()
+    _migrate(conn)
+    assert "acceptance_criteria" in _cols(conn, "tasks")
+    conn.close()
+
+
+def test_migrate_acceptance_criteria_is_nullable_after_migration():
+    """После миграции acceptance_criteria nullable — старые строки не ломаются."""
+    conn = _old_schema_conn()
+    conn.execute(
+        "INSERT INTO projects (id, name, path) VALUES ('pm', 'P', '/p')"
+    )
+    conn.execute(
+        "INSERT INTO tasks (id, project_id, title) VALUES ('tm', 'pm', 'Old Task')"
+    )
+    conn.commit()
+    _migrate(conn)
+    row = conn.execute("SELECT acceptance_criteria FROM tasks WHERE id='tm'").fetchone()
+    assert row["acceptance_criteria"] is None
+    conn.close()