diff --git a/.gitignore b/.gitignore
index 4a5091a..06d2c93 100644
--- a/.gitignore
+++ b/.gitignore
@@ -42,13 +42,14 @@ yarn-error.log*
 extension/*.xpi
 extension/web-ext-artifacts/
 
-# Runtime volumes (must never be tracked)
-images/
-import/
-downloads/
-models/
-postgres_data/
-redis_data/
+# Runtime volumes (must never be tracked) — anchored to repo root so they
+# don't accidentally match Python package dirs like backend/app/models/
+/images/
+/import/
+/downloads/
+/models/
+/postgres_data/
+/redis_data/
 
 # IDE / OS
 .vscode/
diff --git a/alembic.ini b/alembic.ini
new file mode 100644
index 0000000..8b17767
--- /dev/null
+++ b/alembic.ini
@@ -0,0 +1,40 @@
+[alembic]
+script_location = alembic
+prepend_sys_path = .
+file_template = %%(rev)s_%%(slug)s
+version_path_separator = os
+sqlalchemy.url =
+
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S
diff --git a/alembic/env.py b/alembic/env.py
new file mode 100644
index 0000000..9cabe10
--- /dev/null
+++ b/alembic/env.py
@@ -0,0 +1,53 @@
+"""Alembic environment — reads DATABASE_URL from app config."""
+
+from logging.config import fileConfig
+
+from alembic import context
+from sqlalchemy import engine_from_config, pool
+
+from backend.app.config import get_config
+from backend.app.models import Base
+
+config = context.config
+
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+config.set_main_option("sqlalchemy.url", get_config().database_url_sync)
+
+target_metadata = Base.metadata
+
+
+def run_migrations_offline() -> None:
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+        compare_type=True,
+    )
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+            compare_type=True,
+        )
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()
diff --git a/alembic/script.py.mako b/alembic/script.py.mako
new file mode 100644
index 0000000..17dcba0
--- /dev/null
+++ b/alembic/script.py.mako
@@ -0,0 +1,25 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    ${downgrades if downgrades else "pass"}
diff --git a/alembic/versions/.gitkeep b/alembic/versions/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/backend/app/models/__init__.py b/backend/app/models/__init__.py
new file mode 100644
index 0000000..f420c81
--- /dev/null
+++ b/backend/app/models/__init__.py
@@ -0,0 +1,7 @@
+"""All ORM models. Import this module to make every model visible to Alembic."""
+
+from .base import Base
+
+# Concrete models land in Task 6 and re-export here.
+
+__all__ = ["Base"]
diff --git a/backend/app/models/base.py b/backend/app/models/base.py
new file mode 100644
index 0000000..9fd456b
--- /dev/null
+++ b/backend/app/models/base.py
@@ -0,0 +1,17 @@
+"""SQLAlchemy declarative base with standardized constraint naming."""
+
+from sqlalchemy import MetaData
+from sqlalchemy.orm import DeclarativeBase
+
+# Stable constraint names so Alembic autogeneration produces clean diffs.
+NAMING_CONVENTION = {
+    "ix": "ix_%(column_0_label)s",
+    "uq": "uq_%(table_name)s_%(column_0_name)s",
+    "ck": "ck_%(table_name)s_%(constraint_name)s",
+    "fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
+    "pk": "pk_%(table_name)s",
+}
+
+
+class Base(DeclarativeBase):
+    metadata = MetaData(naming_convention=NAMING_CONVENTION)