diff --git a/coverage_boost_test.go b/coverage_boost_test.go
new file mode 100644
index 0000000..3fb6f2b
--- /dev/null
+++ b/coverage_boost_test.go
@@ -0,0 +1,161 @@
+package olapsql_test
+
+// coverage_boost_test.go — Phase 3 coverage boost
+// Targets: Clients.SetLogger, Clients.BuildSQL, Manager.SetLogger, Manager.BuildSQL,
+//          NewTranslator (direct-SQL path), FileAdapter.GetMetricsBySource/GetDimensionsBySource,
+//          database.getDialect unsupported-type error path.
+
+import (
+	"testing"
+
+	olapsql "github.com/awatercolorpen/olap-sql"
+	"github.com/awatercolorpen/olap-sql/api/types"
+	"github.com/stretchr/testify/assert"
+	"gorm.io/gorm/logger"
+)
+
+// ---------------------------------------------------------------------------
+// Clients.SetLogger
+// ---------------------------------------------------------------------------
+
+func TestClients_SetLogger(t *testing.T) {
+	clients, err := newClients(t.TempDir())
+	assert.NoError(t, err)
+
+	// SetLogger should not panic; pass a no-op logger.
+	clients.SetLogger(logger.Discard)
+}
+
+// ---------------------------------------------------------------------------
+// Clients.BuildSQL
+// ---------------------------------------------------------------------------
+
+func TestClients_BuildSQL(t *testing.T) {
+	// BuildSQL uses DryRun mode, so no data loading is required.
+	m, err := newManager(t)
+	assert.NoError(t, err)
+
+	query := MockQuery1()
+
+	dictionary, err := m.GetDictionary()
+	assert.NoError(t, err)
+
+	clause, err := dictionary.Translate(query)
+	assert.NoError(t, err)
+
+	clients, err := m.GetClients()
+	assert.NoError(t, err)
+
+	sqlStr, err := clients.BuildSQL(clause)
+	assert.NoError(t, err)
+	assert.NotEmpty(t, sqlStr)
+}
+
+// ---------------------------------------------------------------------------
+// Manager.SetLogger
+// ---------------------------------------------------------------------------
+
+func TestManager_SetLogger(t *testing.T) {
+	m, err := newManager(t)
+	assert.NoError(t, err)
+
+	// Should silently succeed (logs go to Discard).
+	m.SetLogger(logger.Discard)
+}
+
+// ---------------------------------------------------------------------------
+// Manager.BuildSQL
+// ---------------------------------------------------------------------------
+
+func TestManager_BuildSQL(t *testing.T) {
+	m, err := newManager(t)
+	assert.NoError(t, err)
+	assert.NoError(t, MockLoad(m))
+
+	query := MockQuery1()
+	sql, err := m.BuildSQL(query)
+	assert.NoError(t, err)
+	assert.NotEmpty(t, sql)
+}
+
+// ---------------------------------------------------------------------------
+// NewTranslator — direct-SQL path (query.Sql != "")
+// ---------------------------------------------------------------------------
+
+func TestNewTranslator_DirectSQL(t *testing.T) {
+	dict, err := newDictionary()
+	assert.NoError(t, err)
+
+	query := &types.Query{
+		DataSetName: mockWikiStatDataSet,
+		Sql:         "SELECT 1",
+	}
+
+	clause, err := dict.Translate(query)
+	assert.NoError(t, err)
+	assert.NotNil(t, clause)
+
+	// Verify the direct-SQL path preserved the raw SQL string.
+	sqlClause, ok := clause.(*types.SqlClause)
+	assert.True(t, ok, "expected clause to be *types.SqlClause")
+	assert.Equal(t, "SELECT 1", sqlClause.Sql)
+}
+
+// ---------------------------------------------------------------------------
+// FileAdapter.GetMetricsBySource / GetDimensionsBySource
+// ---------------------------------------------------------------------------
+
+func TestFileAdapter_GetMetricsBySource(t *testing.T) {
+	adapter, err := newFileAdapter()
+	assert.NoError(t, err)
+
+	// "wikistat" is a known source in the test dictionary.
+	metrics := adapter.GetMetricsBySource("wikistat")
+	assert.NotEmpty(t, metrics, "expected at least one metric for source 'wikistat'")
+
+	// Non-existent source should return empty slice (not an error).
+	none := adapter.GetMetricsBySource("__nonexistent__")
+	assert.Empty(t, none)
+}
+
+func TestFileAdapter_GetDimensionsBySource(t *testing.T) {
+	adapter, err := newFileAdapter()
+	assert.NoError(t, err)
+
+	dims := adapter.GetDimensionsBySource("wikistat")
+	assert.NotEmpty(t, dims, "expected at least one dimension for source 'wikistat'")
+
+	none := adapter.GetDimensionsBySource("__nonexistent__")
+	assert.Empty(t, none)
+}
+
+// ---------------------------------------------------------------------------
+// DBOption.NewDB — unsupported type returns error
+// ---------------------------------------------------------------------------
+
+func TestDBOption_NewDB_UnsupportedType(t *testing.T) {
+	opt := &olapsql.DBOption{
+		DSN:  "whatever",
+		Type: types.DBType("__unknown__"),
+	}
+	_, err := opt.NewDB()
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "unsupported db type")
+}
+
+// ---------------------------------------------------------------------------
+// helpers
+// ---------------------------------------------------------------------------
+
+func newDictionary() (*olapsql.Dictionary, error) {
+	do := getDictionaryOption()
+	return olapsql.NewDictionary(do)
+}
+
+func newFileAdapter() (olapsql.IAdapter, error) {
+	opt := &olapsql.AdapterOption{
+		Type: olapsql.FILEAdapter,
+		Dsn:  "test/dictionary.sqlite.toml",
+	}
+	return olapsql.NewAdapter(opt)
+}