api: make workspace root configurable instead of hardcoded /workspace

- Add workspaceRoot field (default "/workspace") to Server struct
- Add SetWorkspaceRoot method on Server
- Update handleListWorkspaces to use s.workspaceRoot
- Add WorkspaceRoot field to Config with default "/workspace"
- Wire cfg.WorkspaceRoot into server in serve.go
- Expose --workspace-root flag on the serve command
- Add TestListWorkspaces_UsesConfiguredRoot integration test

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

2 files changed, 53 insertions, 2 deletions

diff --git a/internal/api/server.go b/internal/api/server.go
index 1d87b3f..0868295 100644
--- a/internal/api/server.go
+++ b/internal/api/server.go
@@ -42,6 +42,7 @@ type Server struct {
 	validateCmdPath  string         // overrides claudeBinPath for validate; used in tests
 	scripts          ScriptRegistry // optional; maps endpoint name → script path
 	workDir          string         // working directory injected into elaborate system prompt
+	workspaceRoot    string         // root directory for listing workspaces; defaults to "/workspace"
 	notifier         notify.Notifier
 	apiToken         string         // if non-empty, required for WebSocket (and REST) connections
 	elaborateLimiter *ipRateLimiter // per-IP rate limiter for elaborate/validate endpoints
@@ -57,6 +58,11 @@ func (s *Server) SetNotifier(n notify.Notifier) {
 	s.notifier = n
 }
 
+// SetWorkspaceRoot configures the root directory used by handleListWorkspaces.
+func (s *Server) SetWorkspaceRoot(path string) {
+	s.workspaceRoot = path
+}
+
 func NewServer(store *storage.DB, pool *executor.Pool, logger *slog.Logger, claudeBinPath, geminiBinPath string) *Server {
 	wd, _ := os.Getwd()
 	s := &Server{
@@ -71,6 +77,7 @@ func NewServer(store *storage.DB, pool *executor.Pool, logger *slog.Logger, clau
 		claudeBinPath: claudeBinPath,
 		geminiBinPath: geminiBinPath,
 		workDir:       wd,
+		workspaceRoot: "/workspace",
 	}
 	s.routes()
 	return s
@@ -321,7 +328,7 @@ func (s *Server) handleListWorkspaces(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
-	entries, err := os.ReadDir("/workspace")
+	entries, err := os.ReadDir(s.workspaceRoot)
 	if err != nil {
 		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "failed to list workspaces"})
 		return
@@ -329,7 +336,7 @@ func (s *Server) handleListWorkspaces(w http.ResponseWriter, r *http.Request) {
 	var dirs []string
 	for _, e := range entries {
 		if e.IsDir() {
-			dirs = append(dirs, "/workspace/"+e.Name())
+			dirs = append(dirs, s.workspaceRoot+"/"+e.Name())
 		}
 	}
 	writeJSON(w, http.StatusOK, dirs)
diff --git a/internal/api/server_test.go b/internal/api/server_test.go
index 8484e02..765b813 100644
--- a/internal/api/server_test.go
+++ b/internal/api/server_test.go
@@ -99,6 +99,50 @@ func (m *mockRunner) Run(_ context.Context, _ *task.Task, _ *storage.Execution)
 	return nil
 }
 
+func TestListWorkspaces_UsesConfiguredRoot(t *testing.T) {
+	srv, _ := testServer(t)
+
+	root := t.TempDir()
+	for _, name := range []string{"alpha", "beta", "gamma"} {
+		if err := os.Mkdir(filepath.Join(root, name), 0755); err != nil {
+			t.Fatal(err)
+		}
+	}
+	// Also create a file (should be excluded from results).
+	f, err := os.Create(filepath.Join(root, "notadir.txt"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	f.Close()
+
+	srv.SetWorkspaceRoot(root)
+
+	req := httptest.NewRequest("GET", "/api/workspaces", nil)
+	w := httptest.NewRecorder()
+	srv.Handler().ServeHTTP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("status: want 200, got %d", w.Code)
+	}
+	var dirs []string
+	if err := json.NewDecoder(w.Body).Decode(&dirs); err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+	want := map[string]bool{
+		root + "/alpha": true,
+		root + "/beta":  true,
+		root + "/gamma": true,
+	}
+	if len(dirs) != len(want) {
+		t.Fatalf("want %d dirs, got %d: %v", len(want), len(dirs), dirs)
+	}
+	for _, d := range dirs {
+		if !want[d] {
+			t.Errorf("unexpected dir in response: %s", d)
+		}
+	}
+}
+
 func TestHealthEndpoint(t *testing.T) {
 	srv, _ := testServer(t)
 	req := httptest.NewRequest("GET", "/api/health", nil)