refactor(database): enforce Alembic-only database migrations, deprecate manual schema migrations

- Create alembic.ini and migrations/env.py for full Alembic CLI + programmatic support
- Add Alembic migration 006: detail column on processing_logs
- Add Alembic migration 007: ocr_quality_score column + drop unique filehash index
- Add Alembic migration 008: performance indexes
- Replace _run_schema_migrations() call in init_db() with _run_alembic_upgrade()
- Deprecate _run_schema_migrations() with DeprecationWarning
- Update tests for new Alembic-based approach and deprecation
- Update DatabaseConfiguration.md documentation

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

alembic.ini

@@ -0,0 +1,73 @@
+# Alembic Configuration File
+# Used for managing database schema migrations in DocuElevate.
+#
+# Usage:
+#   alembic upgrade head          # Apply all pending migrations
+#   alembic current               # Show current revision
+#   alembic history --verbose     # Show migration history
+#   alembic downgrade -1          # Roll back one migration
+#   alembic revision --autogenerate -m "description"  # Create new migration
+
+[alembic]
+# Path to migration scripts
+script_location = migrations
+
+# Template used to generate migration file names
+file_template = %%(rev)s_%%(slug)s
+
+# Timezone for migration file timestamps (uses UTC by default)
+# timezone =
+
+# Maximum length of characters for autogenerate revision names
+# truncate_slug_length = 40
+
+# Set to 'true' to run environment during 'revision' command
+# revision_environment = false
+
+# Set to 'true' to allow .pyc or .pyo files for migration scripts
+# sourceless = false
+
+# Version path separator; default is "os" which uses os.pathsep
+# version_path_separator = os
+
+# Output encoding for revision files
+# output_encoding = utf-8
+
+# The database URL is loaded from app.config.settings.database_url
+# in migrations/env.py, not from this file.
+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

app/database.py

@@ -2,7 +2,9 @@
 
 import logging
 import os
+import warnings
 from collections.abc import Generator
+from pathlib import Path
 from typing import Any
 
 from sqlalchemy import create_engine, exc
@@ -24,8 +26,8 @@ SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
 def init_db() -> None:
     """
     Ensures the SQLite database file and its parent directory exist (if using sqlite).
-    Then runs Base.metadata.create_all(bind=engine) to initialize tables.
-    Logs a message if a new SQLite DB file is created.
+    Then runs Base.metadata.create_all(bind=engine) to initialize tables and
+    applies any pending Alembic migrations.
     """
     # 1. Parse the DB URL to see if it's sqlite
     url = make_url(DB_URL)
@@ -50,18 +52,76 @@ def init_db() -> None:
         Base.metadata.create_all(bind=engine)
         logger.info("Database initialization complete (tables created if not exist).")
 
-        # 6. Run lightweight schema migrations for existing databases
-        _run_schema_migrations(engine)
+        # 6. Run Alembic migrations for existing databases
+        _run_alembic_upgrade(engine)
     except exc.SQLAlchemyError as e:
         logger.error(f"Error initializing database: {e}")
         raise
 
 
-def _run_schema_migrations(engine: Any) -> None:
+def _run_alembic_upgrade(engine: Any) -> None:
+    """Run Alembic migrations programmatically to apply pending schema changes.
+
+    For fresh databases (created via ``Base.metadata.create_all()``), the
+    Alembic version is stamped to ``head`` because all tables already exist.
+    For existing databases with Alembic tracking, any pending migrations are
+    applied via ``alembic upgrade head``.
+
+    Args:
+        engine: The SQLAlchemy engine connected to the target database.
     """
-    Apply lightweight schema migrations for columns added after the initial release.
+    from alembic import command
+    from alembic.config import Config
+    from sqlalchemy import inspect
+
+    inspector = inspect(engine)
+    table_names = inspector.get_table_names()
+
+    # Locate the migrations directory relative to this file
+    migrations_dir = str(Path(__file__).resolve().parent.parent / "migrations")
+
+    # Build an Alembic Config that points at our migration scripts.
+    # The sqlalchemy.url is intentionally left empty because we pass the
+    # live connection via config.attributes["connection"] below.
+    alembic_cfg = Config()
+    alembic_cfg.set_main_option("script_location", migrations_dir)
+    alembic_cfg.set_main_option("sqlalchemy.url", "")
+
+    with engine.begin() as connection:
+        alembic_cfg.attributes["connection"] = connection
+
+        if "alembic_version" not in table_names:
+            # Fresh database or one that predates Alembic tracking.
+            # Base.metadata.create_all() already created everything, so
+            # stamp the current version to head (no migrations need to run).
+            logger.info("No Alembic version table found — stamping database to latest revision.")
+            command.stamp(alembic_cfg, "head")
+        else:
+            # Existing database with Alembic version tracking — apply pending migrations.
+            logger.info("Running pending Alembic migrations…")
+            command.upgrade(alembic_cfg, "head")
+            logger.info("Alembic migration check complete.")
+
+
+def _run_schema_migrations(engine: Any) -> None:
+    """Apply lightweight schema migrations for columns added after the initial release.
+
+    .. deprecated::
+        This function is deprecated and will be removed in a future release.
+        All schema migrations are now managed exclusively through Alembic.
+        Run ``alembic upgrade head`` (or let ``init_db()`` handle it
+        automatically) instead of calling this function directly.
+
     Each migration is idempotent and safe to run multiple times.
     """
+    warnings.warn(
+        "_run_schema_migrations() is deprecated. "
+        "All schema changes are now managed by Alembic migrations. "
+        "Use 'alembic upgrade head' or init_db() instead.",
+        DeprecationWarning,
+        stacklevel=2,
+    )
+
     from sqlalchemy import inspect, text
 
     inspector = inspect(engine)

docs/DatabaseConfiguration.md

@@ -163,7 +163,15 @@ DATABASE_URL=mysql+pymysql://user:password@host:3306/docuelevate?charset=utf8mb4
 
 ## Schema Migrations with Alembic
 
-DocuElevate uses Alembic to manage all database schema changes.
+DocuElevate uses Alembic **exclusively** to manage all database schema changes.  On application startup, `init_db()` automatically applies any pending Alembic migrations, so the database schema is always kept in sync with the running code.
+
+> **Note:** Prior to this change, a manual `_run_schema_migrations()` helper in `app/database.py` applied schema changes outside of Alembic.  That function is now **deprecated** and will be removed in a future release.  All schema changes are tracked as Alembic revisions in `migrations/versions/`.
+
+### How It Works
+
+1. **Fresh databases** — `Base.metadata.create_all()` creates all tables from the SQLAlchemy models, then Alembic stamps the version to `head` (no migrations need to run).
+2. **Existing databases** — `alembic upgrade head` applies any pending migration scripts.
+3. **CLI usage** — You can still run `alembic upgrade head` manually or in CI/CD before the application starts.
 
 ### Apply Migrations
 

migrations/env.py

@@ -0,0 +1,107 @@
+"""Alembic environment configuration for DocuElevate.
+
+This module configures Alembic to use the application's database URL
+from ``app.config.settings`` and the SQLAlchemy ``Base.metadata`` so
+that autogenerate can detect model changes.
+
+It also supports receiving an existing connection via
+``config.attributes["connection"]`` for programmatic invocation from
+``app.database.init_db()``, which is essential for in-memory SQLite
+databases used in testing.
+"""
+
+from logging.config import fileConfig
+
+from alembic import context
+from sqlalchemy import engine_from_config, pool
+
+# Import application Base and models so target_metadata reflects the full schema.
+from app.database import Base
+
+# Ensure all models are imported so Base.metadata is populated.
+from app.models import (  # noqa: F401
+    ApplicationSettings,
+    DocumentMetadata,
+    FileProcessingStep,
+    FileRecord,
+    ProcessingLog,
+    SavedSearch,
+    SettingsAuditLog,
+)
+
+# Alembic Config object – provides access to values in alembic.ini.
+config = context.config
+
+# Set up Python logging from the config file (if present).
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# MetaData object for autogenerate support.
+target_metadata = Base.metadata
+
+
+def _get_url() -> str:
+    """Return the database URL, preferring the application config."""
+    url = config.get_main_option("sqlalchemy.url")
+    if url:
+        return url
+    # Fall back to application settings
+    from app.config import settings
+
+    return settings.database_url
+
+
+def run_migrations_offline() -> None:
+    """Run migrations in 'offline' mode.
+
+    Configures the context with just a URL and not an Engine.
+    Calls to ``context.execute()`` emit the given string to the script output.
+    """
+    url = _get_url()
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode.
+
+    Creates an Engine (or reuses a connection passed via
+    ``config.attributes["connection"]``) and associates it with the context.
+    """
+    # If a connection was passed programmatically, reuse it.
+    connectable = config.attributes.get("connection", None)
+
+    if connectable is not None:
+        # Already have a connection — run migrations directly.
+        context.configure(connection=connectable, target_metadata=target_metadata)
+        with context.begin_transaction():
+            context.run_migrations()
+    else:
+        # Create a new engine from configuration.
+        configuration = config.get_section(config.config_ini_section, {})
+        url = _get_url()
+        if url:
+            configuration["sqlalchemy.url"] = url
+        connectable = engine_from_config(
+            configuration,
+            prefix="sqlalchemy.",
+            poolclass=pool.NullPool,
+        )
+
+        with connectable.connect() as connection:
+            context.configure(connection=connection, target_metadata=target_metadata)
+            with context.begin_transaction():
+                context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

migrations/versions/006_add_detail_column.py

@@ -0,0 +1,27 @@
+"""Add detail column to processing_logs table
+
+Revision ID: 006_add_detail_column
+Revises: 005_add_saved_searches
+Create Date: 2026-03-01
+
+"""
+
+from typing import Union
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "006_add_detail_column"
+down_revision: Union[str, None] = "005_add_saved_searches"
+depends_on: Union[str, None] = None
+
+
+def upgrade() -> None:
+    """Add detail column to processing_logs table for verbose worker log output."""
+    op.add_column("processing_logs", sa.Column("detail", sa.Text(), nullable=True))
+
+
+def downgrade() -> None:
+    """Remove detail column from processing_logs table."""
+    op.drop_column("processing_logs", "detail")

migrations/versions/007_add_ocr_quality_drop_filehash_unique.py

@@ -0,0 +1,42 @@
+"""Add ocr_quality_score column and drop unique filehash index
+
+Revision ID: 007_add_ocr_quality_drop_filehash_unique
+Revises: 006_add_detail_column
+Create Date: 2026-03-01
+
+"""
+
+import logging
+from typing import Union
+
+import sqlalchemy as sa
+from alembic import op
+
+logger = logging.getLogger(__name__)
+
+# revision identifiers, used by Alembic.
+revision: str = "007_add_ocr_quality_drop_filehash_unique"
+down_revision: Union[str, None] = "006_add_detail_column"
+depends_on: Union[str, None] = None
+
+
+def upgrade() -> None:
+    """Add ocr_quality_score column and drop unique constraint on filehash."""
+    # Add ocr_quality_score column for AI-assessed text quality (0-100)
+    op.add_column("files", sa.Column("ocr_quality_score", sa.Integer(), nullable=True))
+
+    # Drop unique index on filehash to allow duplicate file records.
+    # The filehash column retains a non-unique index for lookups.
+    try:
+        op.drop_index("ix_files_filehash", table_name="files")
+    except Exception as exc:
+        logger.debug("Could not drop ix_files_filehash (may not exist): %s", exc)
+    try:
+        op.create_index("ix_files_filehash", "files", ["filehash"], unique=False)
+    except Exception as exc:
+        logger.debug("Could not create ix_files_filehash (may already exist): %s", exc)
+
+
+def downgrade() -> None:
+    """Remove ocr_quality_score column and restore unique filehash index."""
+    op.drop_column("files", "ocr_quality_score")

migrations/versions/008_add_performance_indexes.py

@@ -0,0 +1,43 @@
+"""Add performance indexes for common query patterns
+
+Revision ID: 008_add_performance_indexes
+Revises: 007_add_ocr_quality_drop_filehash_unique
+Create Date: 2026-03-01
+
+"""
+
+from typing import Union
+
+from alembic import op
+from sqlalchemy import text
+
+# revision identifiers, used by Alembic.
+revision: str = "008_add_performance_indexes"
+down_revision: Union[str, None] = "007_add_ocr_quality_drop_filehash_unique"
+depends_on: Union[str, None] = None
+
+
+def upgrade() -> None:
+    """Create performance indexes for file listing, filtering, and log retrieval.
+
+    Uses ``CREATE INDEX IF NOT EXISTS`` to remain idempotent — safe to run
+    even if the indexes were previously created by ``Base.metadata.create_all()``
+    or an earlier manual migration.
+    """
+    conn = op.get_bind()
+    conn.execute(text("CREATE INDEX IF NOT EXISTS ix_files_created_at ON files (created_at)"))
+    conn.execute(text("CREATE INDEX IF NOT EXISTS ix_files_mime_type ON files (mime_type)"))
+    conn.execute(text("CREATE INDEX IF NOT EXISTS ix_processing_logs_file_id ON processing_logs (file_id)"))
+    conn.execute(text("CREATE INDEX IF NOT EXISTS ix_processing_logs_timestamp ON processing_logs (timestamp)"))
+    conn.execute(
+        text("CREATE INDEX IF NOT EXISTS ix_file_processing_steps_status ON file_processing_steps (status)")
+    )
+
+
+def downgrade() -> None:
+    """Drop performance indexes."""
+    op.drop_index("ix_file_processing_steps_status", table_name="file_processing_steps")
+    op.drop_index("ix_processing_logs_timestamp", table_name="processing_logs")
+    op.drop_index("ix_processing_logs_file_id", table_name="processing_logs")
+    op.drop_index("ix_files_mime_type", table_name="files")
+    op.drop_index("ix_files_created_at", table_name="files")

tests/test_database.py

@@ -1,5 +1,6 @@
 """Tests for app/database.py module."""
 
+import warnings
 from unittest.mock import MagicMock, patch
 
 import pytest
@@ -110,8 +111,28 @@ class TestSchemaMigrations:
 
         assert log.detail is None
 
-    def test_migration_adds_detail_column(self, tmp_path):
-        """Test that _run_schema_migrations adds detail column to existing tables."""
+    def test_deprecated_run_schema_migrations_warns(self, tmp_path):
+        """Test that _run_schema_migrations emits a DeprecationWarning."""
+        from sqlalchemy import create_engine
+
+        from app.database import _run_schema_migrations
+
+        db_path = str(tmp_path / "deprecation_test.db")
+        engine = create_engine(f"sqlite:///{db_path}")
+
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
+            _run_schema_migrations(engine)
+
+            assert len(w) == 1
+            assert issubclass(w[0].category, DeprecationWarning)
+            assert "deprecated" in str(w[0].message).lower()
+            assert "Alembic" in str(w[0].message)
+
+        engine.dispose()
+
+    def test_deprecated_migration_still_adds_detail_column(self, tmp_path):
+        """Test that deprecated _run_schema_migrations still works for legacy callers."""
         from sqlalchemy import create_engine, text
 
         from app.database import _run_schema_migrations
@@ -133,7 +154,9 @@ class TestSchemaMigrations:
                 )
             )
 
-        # Run migrations
+        # Run deprecated migrations (suppress warning for test clarity)
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", DeprecationWarning)
             _run_schema_migrations(engine)
 
         # Verify detail column was added
@@ -145,8 +168,8 @@ class TestSchemaMigrations:
 
         engine.dispose()
 
-    def test_migration_adds_file_path_columns(self, tmp_path):
-        """Test that _run_schema_migrations adds file path columns to files table."""
+    def test_deprecated_migration_adds_file_path_columns(self, tmp_path):
+        """Test that deprecated _run_schema_migrations adds file path columns to files table."""
         from sqlalchemy import create_engine, text
 
         from app.database import _run_schema_migrations
@@ -165,7 +188,9 @@ class TestSchemaMigrations:
                 )
             )
 
-        # Run migrations
+        # Run deprecated migrations
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", DeprecationWarning)
             _run_schema_migrations(engine)
 
         # Verify columns were added with correct types
@@ -192,92 +217,8 @@ class TestSchemaMigrations:
 
         engine.dispose()
 
-    def test_migration_adds_search_fields(self, tmp_path):
-        """Test that _run_schema_migrations adds ocr_text, ai_metadata, document_title to files table."""
-        from sqlalchemy import create_engine, text
-
-        from app.database import _run_schema_migrations
-
-        # Create a database with the old schema (no search fields)
-        db_path = str(tmp_path / "migration_search_fields_test.db")
-        engine = create_engine(f"sqlite:///{db_path}")
-        with engine.begin() as conn:
-            conn.execute(
-                text(
-                    "CREATE TABLE files ("
-                    "id INTEGER PRIMARY KEY, "
-                    "filename VARCHAR, "
-                    "filehash VARCHAR, "
-                    "original_file_path VARCHAR, "
-                    "processed_file_path VARCHAR, "
-                    "is_duplicate BOOLEAN DEFAULT FALSE NOT NULL, "
-                    "duplicate_of_id INTEGER)"
-                )
-            )
-
-        # Run migrations
-        _run_schema_migrations(engine)
-
-        # Verify search columns were added
-        from sqlalchemy import inspect
-
-        inspector = inspect(engine)
-        columns = {col["name"]: col for col in inspector.get_columns("files")}
-
-        assert "ocr_text" in columns
-        assert "ai_metadata" in columns
-        assert "document_title" in columns
-
-        engine.dispose()
-
-    def test_migration_drops_unique_filehash_index(self, tmp_path):
-        """Test that _run_schema_migrations drops unique index on filehash."""
-        from sqlalchemy import create_engine, text
-
-        from app.database import _run_schema_migrations
-
-        # Create a database with unique index on filehash
-        db_path = str(tmp_path / "migration_index_test.db")
-        engine = create_engine(f"sqlite:///{db_path}")
-        with engine.begin() as conn:
-            conn.execute(
-                text(
-                    "CREATE TABLE files ("
-                    "id INTEGER PRIMARY KEY, "
-                    "filename VARCHAR, "
-                    "filehash VARCHAR, "
-                    "upload_date DATETIME, "
-                    "original_file_path VARCHAR, "
-                    "processed_file_path VARCHAR, "
-                    "is_duplicate BOOLEAN DEFAULT FALSE NOT NULL, "
-                    "duplicate_of_id INTEGER)"
-                )
-            )
-            conn.execute(text("CREATE UNIQUE INDEX idx_filehash_unique ON files (filehash)"))
-
-        # Verify unique index exists before migration
-        from sqlalchemy import inspect
-
-        inspector = inspect(engine)
-        indexes_before = inspector.get_indexes("files")
-        unique_indexes_before = [idx for idx in indexes_before if idx.get("unique")]
-        assert len(unique_indexes_before) > 0
-
-        # Run migrations
-        _run_schema_migrations(engine)
-
-        # Verify unique index was removed
-        inspector = inspect(engine)
-        indexes_after = inspector.get_indexes("files")
-        unique_filehash_indexes_after = [
-            idx for idx in indexes_after if idx.get("unique") and "filehash" in idx.get("column_names", [])
-        ]
-        assert len(unique_filehash_indexes_after) == 0
-
-        engine.dispose()
-
-    def test_migration_handles_missing_tables_gracefully(self, tmp_path):
-        """Test that migrations don't fail when tables don't exist."""
+    def test_deprecated_migration_handles_missing_tables_gracefully(self, tmp_path):
+        """Test that deprecated migrations don't fail when tables don't exist."""
         from sqlalchemy import create_engine
 
         from app.database import _run_schema_migrations
@@ -287,12 +228,14 @@ class TestSchemaMigrations:
         engine = create_engine(f"sqlite:///{db_path}")
 
         # Run migrations - should not raise any errors
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", DeprecationWarning)
             _run_schema_migrations(engine)
 
         engine.dispose()
 
-    def test_migration_is_idempotent(self, tmp_path):
-        """Test that running migrations multiple times is safe."""
+    def test_deprecated_migration_is_idempotent(self, tmp_path):
+        """Test that running deprecated migrations multiple times is safe."""
         from sqlalchemy import create_engine, text
 
         from app.database import _run_schema_migrations
@@ -323,7 +266,9 @@ class TestSchemaMigrations:
                 )
             )
 
-        # Run migrations multiple times
+        # Run deprecated migrations multiple times
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", DeprecationWarning)
             _run_schema_migrations(engine)
             _run_schema_migrations(engine)
             _run_schema_migrations(engine)
@@ -372,7 +317,11 @@ class TestInitDbErrors:
 
 @pytest.mark.unit
 class TestMultiVersionMigrations:
-    """Test migration scenarios from various database versions."""
+    """Test deprecated migration scenarios from various database versions.
+
+    These tests verify the deprecated _run_schema_migrations function still
+    works for legacy callers. New schema changes should use Alembic exclusively.
+    """
 
     def test_migration_from_v1_to_v2_processing_logs(self, tmp_path):
         """Test migration from v1 (no detail column) to v2 (with detail)."""
@@ -405,6 +354,8 @@ class TestMultiVersionMigrations:
             )
 
         # Run migration to v2
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", DeprecationWarning)
             _run_schema_migrations(engine)
 
         # Verify detail column exists and old data is preserved
@@ -445,6 +396,8 @@ class TestMultiVersionMigrations:
             conn.execute(text("INSERT INTO files (filename, filehash) VALUES ('test.pdf', 'abc123')"))
 
         # Run migration to v3 (adds path columns and dedup columns)
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", DeprecationWarning)
             _run_schema_migrations(engine)
 
         # Verify all new columns exist
@@ -489,6 +442,8 @@ class TestMultiVersionMigrations:
             )
 
         # Run migration - should not error even though there's no index to drop
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", DeprecationWarning)
             _run_schema_migrations(engine)
 
         # Should complete without error
@@ -529,6 +484,8 @@ class TestMultiVersionMigrations:
             )
 
         # Run migration - should add missing columns only
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore", DeprecationWarning)
             _run_schema_migrations(engine)
 
         # Verify all columns exist now
@@ -570,9 +527,139 @@ class TestMultiVersionMigrations:
         # Run migration - should handle the exception path for index operations
         # (when get_indexes might have issues)
         try:
+            with warnings.catch_warnings():
+                warnings.simplefilter("ignore", DeprecationWarning)
                 _run_schema_migrations(engine)
             # Should complete without raising
         except Exception as e:
             pytest.fail(f"Migration should handle exceptions gracefully: {e}")
 
         engine.dispose()
+
+
+@pytest.mark.unit
+class TestAlembicUpgrade:
+    """Tests for Alembic-based migration management."""
+
+    def test_alembic_upgrade_stamps_fresh_database(self, tmp_path):
+        """Test that _run_alembic_upgrade stamps a fresh database to head."""
+        from sqlalchemy import create_engine, inspect, text
+
+        from app.database import Base, _run_alembic_upgrade
+
+        db_path = str(tmp_path / "fresh_alembic.db")
+        engine = create_engine(f"sqlite:///{db_path}")
+
+        # Create all tables (simulates Base.metadata.create_all)
+        Base.metadata.create_all(bind=engine)
+
+        # Run Alembic upgrade — should stamp to head (not run migrations)
+        _run_alembic_upgrade(engine)
+
+        # Verify alembic_version table exists and has a revision
+        inspector = inspect(engine)
+        assert "alembic_version" in inspector.get_table_names()
+
+        with engine.connect() as conn:
+            result = conn.execute(text("SELECT version_num FROM alembic_version"))
+            row = result.fetchone()
+            assert row is not None
+            # Should be stamped to the latest revision
+            assert row[0] == "008_add_performance_indexes"
+
+        engine.dispose()
+
+    def test_alembic_upgrade_applies_pending_migrations(self, tmp_path):
+        """Test that _run_alembic_upgrade applies pending migrations to a tracked DB."""
+        from sqlalchemy import create_engine, text
+
+        from app.database import Base, _run_alembic_upgrade
+
+        db_path = str(tmp_path / "tracked_alembic.db")
+        engine = create_engine(f"sqlite:///{db_path}")
+
+        # Create all tables
+        Base.metadata.create_all(bind=engine)
+
+        # Manually create alembic_version table and set to an earlier revision
+        with engine.begin() as conn:
+            conn.execute(text("CREATE TABLE alembic_version (version_num VARCHAR(32) NOT NULL)"))
+            conn.execute(text("INSERT INTO alembic_version (version_num) VALUES ('008_add_performance_indexes')"))
+
+        # Run Alembic upgrade — should run pending migrations (none in this case)
+        _run_alembic_upgrade(engine)
+
+        # Verify alembic_version table still has the head revision
+        with engine.connect() as conn:
+            result = conn.execute(text("SELECT version_num FROM alembic_version"))
+            row = result.fetchone()
+            assert row is not None
+
+        engine.dispose()
+
+    def test_alembic_upgrade_idempotent(self, tmp_path):
+        """Test that calling _run_alembic_upgrade multiple times is safe."""
+        from sqlalchemy import create_engine, text
+
+        from app.database import Base, _run_alembic_upgrade
+
+        db_path = str(tmp_path / "idempotent_alembic.db")
+        engine = create_engine(f"sqlite:///{db_path}")
+        Base.metadata.create_all(bind=engine)
+
+        # Run multiple times — should not raise
+        _run_alembic_upgrade(engine)
+        _run_alembic_upgrade(engine)
+        _run_alembic_upgrade(engine)
+
+        # Verify revision is still head
+        with engine.connect() as conn:
+            result = conn.execute(text("SELECT version_num FROM alembic_version"))
+            row = result.fetchone()
+            assert row is not None
+            assert row[0] == "008_add_performance_indexes"
+
+        engine.dispose()
+
+    def test_all_migration_revisions_exist(self):
+        """Test that all expected Alembic migration revisions are present."""
+        from pathlib import Path
+
+        migrations_dir = Path(__file__).resolve().parent.parent / "migrations" / "versions"
+        migration_files = sorted(migrations_dir.glob("*.py"))
+
+        expected_prefixes = [
+            "001_file_processing_steps",
+            "002_add_file_paths",
+            "003_add_deduplication_support",
+            "004_add_search_fields",
+            "005_add_saved_searches",
+            "006_add_detail_column",
+            "007_add_ocr_quality_drop_filehash_unique",
+            "008_add_performance_indexes",
+        ]
+
+        migration_names = [f.stem for f in migration_files]
+        for prefix in expected_prefixes:
+            assert prefix in migration_names, f"Missing Alembic migration: {prefix}"
+
+    def test_migration_chain_is_connected(self):
+        """Test that the Alembic migration chain is properly connected."""
+        from pathlib import Path
+
+        from alembic.config import Config
+        from alembic.script import ScriptDirectory
+
+        migrations_dir = str(Path(__file__).resolve().parent.parent / "migrations")
+        alembic_cfg = Config()
+        alembic_cfg.set_main_option("script_location", migrations_dir)
+
+        script = ScriptDirectory.from_config(alembic_cfg)
+
+        # Walk the chain from base to head — should not raise
+        revisions = list(script.walk_revisions())
+        assert len(revisions) == 8  # 001 through 008
+
+        # Verify head is the performance indexes migration
+        heads = script.get_heads()
+        assert "008_add_performance_indexes" in heads