diff --git a/CLAUDE.md b/CLAUDE.md
index c3f8a3fb..d515a1fd 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -24,6 +24,9 @@ marketplace.
 - **E2E tests**: `go test -tags e2e ./...` (requires Ollama/LM Studio running)
 - **All tests must pass before commit**
 - Coverage tracked but not enforced
+- **TDD required**: All features and bug fixes must follow red/green TDD — write
+  a failing test that demonstrates the bug or specifies the feature first, then
+  make it pass with the implementation.
 
 ### Linting & Errors
 
diff --git a/cmd/search.go b/cmd/search.go
index 1a64f457..b73f807d 100644
--- a/cmd/search.go
+++ b/cmd/search.go
@@ -151,7 +151,11 @@ func runSearch(cmd *cobra.Command, args []string) error {
 	tr.record("path resolution", indexRoot)
 
 	// Span 2: indexer setup
-	idx, err := setupIndexer(&cfg, indexRoot, nil)
+	dbPath := config.DBPathForProject(indexRoot, cfg.Model)
+	if err := os.MkdirAll(filepath.Dir(dbPath), 0o755); err != nil {
+		return fmt.Errorf("create db directory: %w", err)
+	}
+	idx, err := setupIndexer(&cfg, dbPath, nil)
 	if err != nil {
 		return fmt.Errorf("setup indexer: %w", err)
 	}
diff --git a/cmd/search_test.go b/cmd/search_test.go
index a79b6a49..4c319671 100644
--- a/cmd/search_test.go
+++ b/cmd/search_test.go
@@ -2,9 +2,13 @@ package cmd
 
 import (
 	"bytes"
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 	"time"
+
+	"github.com/ory/lumen/internal/config"
 )
 
 func TestTracer_DisabledIsNoop(t *testing.T) {
@@ -108,6 +112,43 @@ func TestSearchCmd_FlagsRegistered(t *testing.T) {
 	}
 }
 
+// TestSetupIndexer_DBPathVsDirectory is a regression test for
+// https://github.com/ory/lumen/issues/72.
+//
+// runSearch previously passed the raw indexRoot directory to setupIndexer
+// instead of the computed DB file path. SQLite cannot open a directory and
+// returns an error containing "PRAGMA journal_mode=WAL".
+//
+// Red: passing the directory directly must fail with a SQLite error.
+// Green: passing config.DBPathForProject(dir, model) must succeed.
+func TestSetupIndexer_DBPathVsDirectory(t *testing.T) {
+	dir := t.TempDir()
+	cfg, err := config.Load()
+	if err != nil {
+		t.Fatalf("load config: %v", err)
+	}
+
+	// RED: directory path → SQLite PRAGMA error (the pre-fix behaviour).
+	_, dirErr := setupIndexer(&cfg, dir, nil)
+	if dirErr == nil {
+		t.Fatal("expected error when passing a directory as the db path, got nil")
+	}
+	if !strings.Contains(dirErr.Error(), "PRAGMA") && !strings.Contains(dirErr.Error(), "unable to open") {
+		t.Fatalf("expected SQLite open error, got: %v", dirErr)
+	}
+
+	// GREEN: proper db file path → no error.
+	dbPath := config.DBPathForProject(dir, cfg.Model)
+	if mkErr := os.MkdirAll(filepath.Dir(dbPath), 0o755); mkErr != nil {
+		t.Fatalf("MkdirAll: %v", mkErr)
+	}
+	idx, err := setupIndexer(&cfg, dbPath, nil)
+	if err != nil {
+		t.Fatalf("setupIndexer with db path failed: %v", err)
+	}
+	_ = idx.Close()
+}
+
 func TestSearchCmd_TraceSpanLabels(t *testing.T) {
 	// Verify the trace span labels that runSearch records match the spec.
 	tr := &tracer{enabled: true}