fix: move frontend off port 3000 and silence reverse-proxy panic logs (#568)

Dockerfile

@@ -118,4 +118,4 @@ EXPOSE 8080
 
 # tini as PID 1 for signal handling; entrypoint handles privilege drop
 ENTRYPOINT ["tini", "--", "docker-entrypoint.sh"]
-CMD ["kandev", "start", "--backend-port", "8080", "--web-port", "3000", "--verbose"]
+CMD ["kandev", "start", "--backend-port", "8080", "--web-port", "37429", "--verbose"]

Makefile

@@ -55,7 +55,7 @@ help:
 	@echo "Development Commands:"
 	@echo "  dev              Run backend + web via CLI (auto ports)"
 	@echo "  dev-backend      Run backend in development mode (port 8080)"
-	@echo "  dev-web          Run web app in development mode (port 3000)"
+	@echo "  dev-web          Run web app in development mode (port 37429)"
 	@echo "  dev              Note: Uses apps/cli launcher (auto ports)"
 	@echo ""
 	@echo "Production Commands:"
@@ -121,8 +121,8 @@ dev-backend:
 
 .PHONY: dev-web
 dev-web:
-	@echo "Starting web app on http://localhost:3000"
-	@cd $(APPS_DIR) && $(PNPM) --filter @kandev/web dev
+	@echo "Starting web app on http://localhost:37429"
+	@cd $(APPS_DIR) && PORT=37429 $(PNPM) --filter @kandev/web dev
 
 #
 # Build

README.md

@@ -144,7 +144,7 @@ make dev
 
 # Or run separately
 make dev-backend    # Backend on :8080
-make dev-web        # Frontend on :3000
+make dev-web        # Frontend on :37429
 ```
 
 ### Testing & Linting

apps/backend/cmd/kandev/helpers.go

@@ -468,10 +468,9 @@ func registerRoutes(p routeParams) {
 		} else {
 			proxy := httputil.NewSingleHostReverseProxy(target)
 			proxy.FlushInterval = -1
-			// Custom error handler to prevent the default behavior of panicking
-			// with http.ErrAbortHandler when the upstream connection fails or the
-			// client disconnects. Without this, Gin's recovery middleware catches
-			// the panic and logs a full (harmless but noisy) stack trace.
+			// ErrorHandler catches upstream failures (e.g., connection refused)
+			// that occur before any response headers are written, returning a
+			// clean 502 instead of letting the default handler log an error.
 			proxy.ErrorHandler = func(w http.ResponseWriter, _ *http.Request, err error) {
 				p.log.Debug("Web proxy error", zap.Error(err))
 				w.WriteHeader(http.StatusBadGateway)
@@ -482,6 +481,19 @@ func registerRoutes(p routeParams) {
 					c.AbortWithStatus(http.StatusNotFound)
 					return
 				}
+				// httputil.ReverseProxy panics with http.ErrAbortHandler as an
+				// intentional stdlib signal when a streaming response is aborted
+				// (e.g., the client disconnects mid-body, or the upstream dies
+				// after response headers were already written). net/http.Server
+				// understands this sentinel panic and closes the connection
+				// quietly, but Gin's recovery middleware catches it first and
+				// logs a noisy stack trace. Swallow that specific panic here
+				// while letting any other panic bubble up to Gin's recovery.
+				defer func() {
+					if r := recover(); r != nil && r != http.ErrAbortHandler {
+						panic(r)
+					}
+				}()
 				proxy.ServeHTTP(c.Writer, c.Request)
 			})
 			p.log.Info("Web reverse proxy enabled", zap.String("target", p.webInternalURL))

apps/cli/src/constants.ts

@@ -3,7 +3,7 @@ import path from "node:path";
 
 // Default service ports (will auto-fallback if busy).
 export const DEFAULT_BACKEND_PORT = 8080;
-export const DEFAULT_WEB_PORT = 3000;
+export const DEFAULT_WEB_PORT = 37429;
 export const DEFAULT_AGENTCTL_PORT = 9999;
 export const DEFAULT_MCP_PORT = 9090;
 

apps/cli/src/run.test.ts

@@ -14,7 +14,7 @@ vi.mock("./constants", () => ({
   },
   DATA_DIR: "/tmp/kandev-test-data",
   DEFAULT_BACKEND_PORT: 8080,
-  DEFAULT_WEB_PORT: 3000,
+  DEFAULT_WEB_PORT: 37429,
   DEFAULT_AGENTCTL_PORT: 9999,
   HEALTH_TIMEOUT_MS_RELEASE: 15000,
   RANDOM_PORT_MIN: 10000,

apps/cli/src/shared.ts

@@ -96,7 +96,7 @@ export function buildWebEnv(options: WebEnvOptions): NodeJS.ProcessEnv {
     ...process.env,
     // Server-side: full localhost URL for SSR fetches (Next.js SSR → Go backend)
     KANDEV_API_BASE_URL: ports.backendUrl,
-    // Client-side: port injection for dev mode (browser on :3000, API on :8080).
+    // Client-side: port injection for dev mode (browser on web port, API on backend port).
     // In production, the backend reverse-proxies Next.js so the client uses same-origin.
     NEXT_PUBLIC_KANDEV_API_PORT: String(ports.backendPort),
     PORT: String(ports.webPort),

apps/web/next.config.ts

@@ -2,7 +2,7 @@ import type { NextConfig } from "next";
 
 const defaultDevOrigins = [
   "localhost",
-  "localhost:3000",
+  "localhost:37429",
   "192.168.1.116", // Maintainer dev server
   "100.105.155.17", // Maintainer dev server (Tailscale)
 ];

docs/cli.md

@@ -50,7 +50,7 @@ npm install -g kandev
 # Run the latest release (recommended for users)
 npx kandev
 
-# Opens the app at http://localhost:3000 (or next available port)
+# Opens the app at http://localhost:37429 (or next available port)
 ```
 
 ## Commands
@@ -113,7 +113,7 @@ npx kandev start
 |--------|-------------|---------|
 | `--version <tag>` | Use a specific release version | `--version v0.1.0` |
 | `--backend-port <port>` | Override backend port | `--backend-port 8080` |
-| `--web-port <port>` | Override web port | `--web-port 3000` |
+| `--web-port <port>` | Override web port | `--web-port 37429` |
 | `--help`, `-h` | Show help | `--help` |
 
 ### Examples
@@ -126,7 +126,7 @@ npx kandev --version v0.1.0
 npx kandev --backend-port 18080 --web-port 13000
 
 # Dev mode with custom ports
-npx kandev dev --backend-port 8080 --web-port 3000
+npx kandev dev --backend-port 8080 --web-port 13000
 ```
 
 ## Port Selection
@@ -136,9 +136,9 @@ By default, the CLI automatically finds available ports:
 | Service | Default Port | Fallback |
 |---------|--------------|----------|
 | Backend | 8080 | Auto-selects from 10000-60000 |
-| Web | 3000 | Auto-selects from 10000-60000 |
-| AgentCtl | 8081 | Auto-selects from 10000-60000 |
-| MCP Server | 8082 | Auto-selects from 10000-60000 |
+| Web | 37429 | Auto-selects from 10000-60000 |
+| AgentCtl | 9999 | Auto-selects from 10000-60000 |
+| MCP Server | 9090 | Auto-selects from 10000-60000 |
 
 If the default port is in use, the CLI finds the next available port automatically.
 
@@ -186,7 +186,7 @@ See `make help` for all available commands.
 The CLI automatically finds available ports. If you need a specific port:
 
 ```bash
-npx kandev --backend-port 8080 --web-port 3000
+npx kandev --backend-port 8080 --web-port 37429
 ```
 
 ### Backend Takes Too Long to Start