diff --git a/workspace-server/internal/bundle/importer_test.go b/workspace-server/internal/bundle/importer_test.go
new file mode 100644
index 00000000..9cb33362
--- /dev/null
+++ b/workspace-server/internal/bundle/importer_test.go
@@ -0,0 +1,157 @@
+package bundle
+
+import (
+	"testing"
+)
+
+func TestBuildBundleConfigFiles_emptyBundle(t *testing.T) {
+	b := &Bundle{}
+	files := buildBundleConfigFiles(b)
+	if len(files) != 0 {
+		t.Errorf("expected empty map for empty bundle, got %d entries", len(files))
+	}
+}
+
+func TestBuildBundleConfigFiles_systemPrompt(t *testing.T) {
+	b := &Bundle{SystemPrompt: "You are a helpful assistant."}
+	files := buildBundleConfigFiles(b)
+	if len(files) != 1 {
+		t.Fatalf("expected 1 file, got %d", len(files))
+	}
+	if string(files["system-prompt.md"]) != "You are a helpful assistant." {
+		t.Errorf("unexpected system prompt content: %q", files["system-prompt.md"])
+	}
+}
+
+func TestBuildBundleConfigFiles_configYaml(t *testing.T) {
+	b := &Bundle{Prompts: map[string]string{
+		"config.yaml": "runtime: langgraph\nmodel: claude-sonnet-4-20250514\n",
+	}}
+	files := buildBundleConfigFiles(b)
+	if len(files) != 1 {
+		t.Fatalf("expected 1 file, got %d", len(files))
+	}
+	if string(files["config.yaml"]) != "runtime: langgraph\nmodel: claude-sonnet-4-20250514\n" {
+		t.Errorf("unexpected config.yaml content: %q", files["config.yaml"])
+	}
+}
+
+func TestBuildBundleConfigFiles_systemPromptAndConfigYaml(t *testing.T) {
+	b := &Bundle{
+		SystemPrompt: "# System",
+		Prompts:     map[string]string{"config.yaml": "runtime: langgraph"},
+	}
+	files := buildBundleConfigFiles(b)
+	if len(files) != 2 {
+		t.Fatalf("expected 2 files, got %d", len(files))
+	}
+	if _, ok := files["system-prompt.md"]; !ok {
+		t.Error("missing system-prompt.md")
+	}
+	if _, ok := files["config.yaml"]; !ok {
+		t.Error("missing config.yaml")
+	}
+}
+
+func TestBuildBundleConfigFiles_skills(t *testing.T) {
+	b := &Bundle{
+		Skills: []BundleSkill{
+			{
+				ID:          "web-search",
+				Name:        "Web Search",
+				Description: "Search the web",
+				Files:       map[string]string{"readme.md": "# Web Search"},
+			},
+			{
+				ID:          "code-runner",
+				Name:        "Code Runner",
+				Description: "Execute code",
+				Files:       map[string]string{"handler.py": "print('hello')"},
+			},
+		},
+	}
+	files := buildBundleConfigFiles(b)
+	if len(files) != 2 {
+		t.Fatalf("expected 2 skill files, got %d", len(files))
+	}
+
+	if content, ok := files["skills/web-search/readme.md"]; !ok {
+		t.Error("missing skills/web-search/readme.md")
+	} else if string(content) != "# Web Search" {
+		t.Errorf("unexpected readme.md: %q", content)
+	}
+
+	if _, ok := files["skills/code-runner/handler.py"]; !ok {
+		t.Error("missing skills/code-runner/handler.py")
+	}
+}
+
+func TestBuildBundleConfigFiles_skillsWithSubPaths(t *testing.T) {
+	b := &Bundle{
+		Skills: []BundleSkill{
+			{
+				ID:    "nested-skill",
+				Files: map[string]string{"src/main.py": "def main(): pass", "pyproject.toml": "[tool.foo]"},
+			},
+		},
+	}
+	files := buildBundleConfigFiles(b)
+	if len(files) != 2 {
+		t.Fatalf("expected 2 files, got %d", len(files))
+	}
+	if _, ok := files["skills/nested-skill/src/main.py"]; !ok {
+		t.Error("missing skills/nested-skill/src/main.py")
+	}
+	if _, ok := files["skills/nested-skill/pyproject.toml"]; !ok {
+		t.Error("missing skills/nested-skill/pyproject.toml")
+	}
+}
+
+func TestBuildBundleConfigFiles_skipsEmptyPrompts(t *testing.T) {
+	b := &Bundle{Prompts: map[string]string{}}
+	files := buildBundleConfigFiles(b)
+	if len(files) != 0 {
+		t.Errorf("expected 0 files for empty prompts map, got %d", len(files))
+	}
+}
+
+func TestBuildBundleConfigFiles_skipsMissingConfigYaml(t *testing.T) {
+	b := &Bundle{
+		SystemPrompt: "# My Prompt",
+		Prompts:      map[string]string{"other.yaml": "something: else"},
+	}
+	files := buildBundleConfigFiles(b)
+	if len(files) != 1 {
+		t.Fatalf("expected 1 file (system-prompt only), got %d", len(files))
+	}
+	if _, ok := files["config.yaml"]; ok {
+		t.Error("config.yaml should not be written when not in Prompts")
+	}
+}
+
+func TestNilIfEmpty_emptyString(t *testing.T) {
+	result := nilIfEmpty("")
+	if result != nil {
+		t.Errorf("expected nil for empty string, got %v", result)
+	}
+}
+
+func TestNilIfEmpty_nonEmptyString(t *testing.T) {
+	result := nilIfEmpty("hello")
+	if result == nil {
+		t.Fatal("expected non-nil result for non-empty string")
+	}
+	if result != "hello" {
+		t.Errorf("expected hello, got %q", result)
+	}
+}
+
+func TestNilIfEmpty_whitespaceString(t *testing.T) {
+	// Whitespace is not empty — nilIfEmpty only checks for zero-length
+	result := nilIfEmpty("   ")
+	if result == nil {
+		t.Error("expected non-nil for whitespace string")
+	} else if result != "   " {
+		t.Errorf("expected '   ', got %q", result)
+	}
+}