diff --git a/internal/server/operation.go b/internal/server/operation.go
index 73491fb8..85a8b70d 100644
--- a/internal/server/operation.go
+++ b/internal/server/operation.go
@@ -137,6 +137,22 @@ func (r *RepoOperation) migration() (err error) {
 		}
 	}
 
+	if version < 5 {
+		// Strip legacy .json.gz and .json suffixes from filenames
+		_, err = r.db.Exec(`
+			UPDATE operations SET filename = REPLACE(filename, '.json.gz', '') WHERE filename LIKE '%.json.gz';
+			UPDATE operations SET filename = REPLACE(filename, '.json', '') WHERE filename LIKE '%.json';
+		`)
+		if err != nil {
+			return fmt.Errorf("merge db to v5 failed (normalize filenames): %w", err)
+		}
+
+		_, err = r.db.Exec(`INSERT INTO version (db) VALUES (5)`)
+		if err != nil {
+			return fmt.Errorf("failed to increase version 5: %w", err)
+		}
+	}
+
 	return nil
 }
 
@@ -387,3 +403,4 @@ func (r *RepoOperation) UpdateMissionDuration(ctx context.Context, id int64, dur
 		`UPDATE operations SET mission_duration = ? WHERE id = ?`, duration, id)
 	return err
 }
+
diff --git a/internal/server/operation_test.go b/internal/server/operation_test.go
index 5601c401..a9207133 100644
--- a/internal/server/operation_test.go
+++ b/internal/server/operation_test.go
@@ -9,6 +9,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestMigration(t *testing.T) {
@@ -35,6 +36,54 @@ func TestMigrationV3StorageFormat(t *testing.T) {
 	assert.ErrorIs(t, err, sql.ErrNoRows)
 }
 
+func TestMigrationV5NormalizeFilenames(t *testing.T) {
+	dir := t.TempDir()
+	pathDB := filepath.Join(dir, "test.db")
+
+	// Create DB manually with legacy filenames (pre-v5)
+	db, err := sql.Open("sqlite3", pathDB)
+	require.NoError(t, err)
+
+	_, err = db.Exec(`
+		CREATE TABLE version (id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, db INTEGER);
+		CREATE TABLE operations (
+			id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
+			world_name TEXT NOT NULL, mission_name TEXT NOT NULL, mission_duration INTEGER NOT NULL,
+			filename TEXT NOT NULL, date TEXT NOT NULL, tag TEXT NOT NULL DEFAULT '',
+			storage_format TEXT DEFAULT 'json', conversion_status TEXT DEFAULT 'completed',
+			schema_version INTEGER DEFAULT 1
+		);
+		INSERT INTO version (db) VALUES (4);
+		INSERT INTO operations (world_name, mission_name, mission_duration, filename, date)
+			VALUES ('altis', 'M1', 3600, 'mission_one.json', '2026-01-01');
+		INSERT INTO operations (world_name, mission_name, mission_duration, filename, date)
+			VALUES ('altis', 'M2', 3600, 'mission_two.json.gz', '2026-01-02');
+		INSERT INTO operations (world_name, mission_name, mission_duration, filename, date)
+			VALUES ('altis', 'M3', 3600, 'mission_clean', '2026-01-03');
+	`)
+	require.NoError(t, err)
+	db.Close()
+
+	// Open via NewRepoOperation which runs migrations
+	repo, err := NewRepoOperation(pathDB)
+	require.NoError(t, err)
+	defer repo.db.Close()
+
+	ctx := context.Background()
+	ops, err := repo.Select(ctx, Filter{Older: "2099-12-31", Newer: "2000-01-01"})
+	require.NoError(t, err)
+	require.Len(t, ops, 3)
+
+	// All filenames should be normalized (newest first by default)
+	filenames := map[string]bool{}
+	for _, op := range ops {
+		filenames[op.Filename] = true
+	}
+	assert.True(t, filenames["mission_one"])
+	assert.True(t, filenames["mission_two"])
+	assert.True(t, filenames["mission_clean"])
+}
+
 func TestOperationStorageFormat(t *testing.T) {
 	dir := t.TempDir()
 	pathDB := filepath.Join(dir, "test.db")
@@ -387,7 +436,7 @@ func TestMigrationRerun(t *testing.T) {
 	var version int
 	err = repo2.db.QueryRow("SELECT db FROM version ORDER BY db DESC LIMIT 1").Scan(&version)
 	assert.NoError(t, err)
-	assert.Equal(t, 4, version)
+	assert.Equal(t, 5, version)
 }
 
 func TestGetTypesEmpty(t *testing.T) {