feat: add --base-path flag to configure UI URL prefix

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

2 files changed, 37 insertions, 3 deletions

diff --git a/internal/api/server.go b/internal/api/server.go
index ffa8cd4..fe883bb 100644
--- a/internal/api/server.go
+++ b/internal/api/server.go
@@ -1,9 +1,11 @@
 package api
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"fmt"
+	"io/fs"
 	"log/slog"
 	"net/http"
 	"os"
@@ -62,6 +64,7 @@ type Server struct {
 	dropsDir         string
 	llm              *llm.Client
 	budget           budgetReporter // optional; per-provider spend headroom for GET /api/budget
+	basePath         string // URL prefix the UI is mounted at, e.g. "/claudomator-oss"
 }
 
 // SetAPIToken configures a bearer token that must be supplied to access the API.
@@ -91,6 +94,11 @@ func (s *Server) SetWorkspaceRoot(path string) {
 	s.workspaceRoot = path
 }
 
+// SetBasePath sets the URL prefix the UI is served under (e.g. "/claudomator-oss").
+func (s *Server) SetBasePath(p string) {
+	s.basePath = p
+}
+
 // Pool returns the executor pool, for graceful shutdown by the caller.
 func (s *Server) Pool() *executor.Pool { return s.pool }
 
@@ -199,7 +207,7 @@ func (s *Server) routes() {
 	s.mux.Handle("POST /chatbot/mcp", chatbotHandler)
 	s.mux.Handle("GET /chatbot/mcp", chatbotHandler)
 	s.mux.Handle("DELETE /chatbot/mcp", chatbotHandler)
-	s.mux.Handle("GET /", http.FileServerFS(webui.Files))
+	s.mux.HandleFunc("GET /", s.handleStaticFiles)
 }
 
 // forwardResults listens on the executor pool's result and started channels and broadcasts via WebSocket.
@@ -695,6 +703,29 @@ func (s *Server) handleGetExecution(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, exec)
 }
 
+func (s *Server) handleStaticFiles(w http.ResponseWriter, r *http.Request) {
+	if r.URL.Path == "/" || r.URL.Path == "/index.html" {
+		raw, err := fs.ReadFile(webui.Files, "index.html")
+		if err != nil {
+			http.Error(w, "not found", http.StatusNotFound)
+			return
+		}
+		basePath := s.basePath
+		if basePath == "" {
+			basePath = "/claudomator"
+		}
+		rewritten := bytes.ReplaceAll(raw,
+			[]byte(`content="/claudomator"`),
+			[]byte(`content="`+basePath+`"`),
+		)
+		w.Header().Set("Content-Type", "text/html; charset=utf-8")
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write(rewritten)
+		return
+	}
+	http.FileServerFS(webui.Files).ServeHTTP(w, r)
+}
+
 func writeJSON(w http.ResponseWriter, status int, v interface{}) {
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(status)
diff --git a/internal/cli/serve.go b/internal/cli/serve.go
index 9aa765b..fe0ba8e 100644
--- a/internal/cli/serve.go
+++ b/internal/cli/serve.go
@@ -23,6 +23,7 @@ import (
 func newServeCmd() *cobra.Command {
 	var addr string
 	var workspaceRoot string
+	var basePath string
 
 	cmd := &cobra.Command{
 		Use:   "serve",
@@ -31,11 +32,12 @@ func newServeCmd() *cobra.Command {
 			if cmd.Flags().Changed("workspace-root") {
 				cfg.WorkspaceRoot = workspaceRoot
 			}
-			return serve(addr)
+			return serve(addr, basePath)
 		},
 	}
 
 	cmd.Flags().StringVar(&addr, "addr", "127.0.0.1:8484", "listen address (loopback by default; set external_bind_allowed=true in config to bind externally)")
+	cmd.Flags().StringVar(&basePath, "base-path", "/claudomator", "URL prefix the UI is served under (e.g. /claudomator-oss)")
 	cmd.Flags().StringVar(&workspaceRoot, "workspace-root", "/workspace", "root directory for listing workspaces")
 	cmd.Flags().StringVar(&cfg.ClaudeImage, "claude-image", cfg.ClaudeImage, "docker image for claude agents")
 	cmd.Flags().StringVar(&cfg.GeminiImage, "gemini-image", cfg.GeminiImage, "docker image for gemini agents")
@@ -43,7 +45,7 @@ func newServeCmd() *cobra.Command {
 	return cmd
 }
 
-func serve(addr string) error {
+func serve(addr, basePath string) error {
 	if err := config.ValidateBindAddr(addr, cfg.ExternalBindAllowed); err != nil {
 		return err
 	}
@@ -175,6 +177,7 @@ func serve(addr string) error {
 	pool.RecoverStaleBlocked()
 
 	srv := api.NewServer(store, pool, agentRegistry, logger, cfg.ClaudeBinaryPath, cfg.GeminiBinaryPath)
+	srv.SetBasePath(basePath)
 	if accountant != nil {
 		srv.SetBudget(accountant)
 	}