Wails3 dev cannot connect to frontend server that is already running

[Mrkouhadi]

DESCRIPTION

When running wails3 dev on a freshly created Wails v3 project, the application fails to start. Despite the frontend being live and reachable, Wails it cannot connect to the frontend server.
I believe it's related to ESBUILD

SYSTEM HEALTH

wails3 doctor
Wails (v3.0.0-alpha.62)  Wails Doctor

# System

┌─────────────────────────────────────────────────┐
| Name          | MacOS                           |
| Version       | 14.7.4                          |
| ID            | 23H420                          |
| Branding      | Sonoma                          |
| Platform      | darwin                          |
| Architecture  | arm64                           |
| Apple Silicon | true                            |
| CPU           | Apple M1                        |
| CPU 1         | Apple M1                        |
| CPU 2         | Apple M1                        |
| GPU           | 8 cores, Metal Support: Metal 3 |
| Memory        | 16 GB                           |
└─────────────────────────────────────────────────┘

# Build Environment

┌────────────────────────────────┐
| Wails CLI    | v3.0.0-alpha.62 |
| Go Version   | go1.25.4        |
| -buildmode   | exe             |
| -compiler    | gc              |
| CGO_CFLAGS   |                 |
| CGO_CPPFLAGS |                 |
| CGO_CXXFLAGS |                 |
| CGO_ENABLED  | 1               |
| CGO_LDFLAGS  |                 |
| GOARCH       | arm64           |
| GOARM64      | v8.0            |
| GOOS         | darwin          |
└────────────────────────────────┘

# Dependencies

┌──────────────────────────────────────────────────────────────────────────────┐
| Xcode cli tools | 2408                                                       |
| npm             | 10.2.3                                                     |
| *NSIS           | v3.11                                                      |
| docker          | *Docker version 27.4.0, build bde2b89 (daemon not running) |
|                                                                              |
└────────────────────────── * - Optional Dependency ───────────────────────────┘

# Checking for issues

 SUCCESS  No issues found

# Diagnosis

 SUCCESS  Your system is ready for Wails development!

Need documentation? Run: wails3 docs
 ♥   If Wails is useful to you or your company, please consider sponsoring the project: wails3 sponsor

---

ERROR LOG

4:21PM INF Build Info: Wails=v3.0.0-alpha.62 Compiler=go1.25.4 -gcflags="all=-l" CGO_ENABLED=1 CGO_CPPFLAGS="" CGO_CXXFLAGS="" GOARCH=arm64 -buildmode=exe CGO_CFLAGS="-mmacosx-version-min=10.15" CGO_LDFLAGS="-mmacosx-version-min=10.15" GOOS=darwin GOARM64=v8.0 -compiler=gc
4:21PM INF Platform Info: ID=23H420 Name=MacOS Version=14.7.4 Branding=Sonoma
4:21PM INF AssetServer Info: middleware=true handler=true devServerURL=http://localhost:9245
4:21PM INF Waiting for frontend dev server to start... url=http://localhost:9245
task: [common:install:frontend:deps] npm install
4:21PM INF Retrying... reify:@esbuild/aix-ppc64: timing reifyNode:node_modules/
4:21PM INF Retrying... reify:@esbuild/aix-ppc64: timing reifyNode:node_modules/
4:21PM INF Retrying... reify:@esbuild/aix-ppc64: timing reifyNode:node_modules/
4:21PM INF Retrying... reify:@esbuild/aix-ppc64: timing reifyNode:node_modules/
4:21PM INF Retrying... reify:@esbuild/aix-ppc64: timing reifyNode:node_modules/
4:21PM ERR ########) ⠋ reify:@esbuild/aix-ppc64: timing reifyNode:node_modules/

******************************** FATAL *********************************
*      There has been a catastrophic failure in your application.      *
**************************** Error Details *****************************
unable to connect to frontend server. Please check it is running - FRONTEND_DEVSERVER_URL='http://localhost:9245'
************************************************************************

ERROR task: Failed to run task "run": exit status 1
2026/01/25 16:21:17 ERROR Could not refresh processes due to execution errors
task: [common:dev:frontend] npm run dev -- --port 9245 --strictPort

[leaanthony]

Thanks for reporting this issue! To help diagnose the problem, could you provide some additional information?

1. Exact esbuild version: What version of esbuild is being installed? You can check with npm list esbuild in your project directory.

2. Node modules state: Does the issue persist if you delete node_modules and reinstall? (rm -rf node_modules && npm install)

3. Network/proxy: Are you behind a corporate proxy or firewall that might be interfering with npm package downloads?

4. Full log output: Could you share the complete output from wails3 dev with the --loglevel debug flag?

The error suggests the frontend dev server is trying to start but esbuild package installation is hanging during the "reify" phase. This is typically a network or npm cache issue rather than a Wails issue, but let's confirm.

[Mrkouhadi]

could you provide some additional information?

After the update, the error has not occurred.
Before, i used to downgrade Vite to V5 or V6. Now all's seem good.

[KiddoV]

@leaanthony I got the same error. I just use the starter app from...
wails3 init -n myapp -t react-ts
Then run wails3 dev
And I got the error:

Run `npm audit` for details.
task: [common:dev:frontend] npm run dev -- --port 9245 --strictPort
Apr 22 12:31:17.672 INF Retrying...
Apr 22 12:31:18.174 ERR 

******************************** FATAL *********************************
*      There has been a catastrophic failure in your application.      *
**************************** Error Details *****************************
unable to connect to frontend server. Please check it is running - FRONTEND_DEVSERVER_URL='http://localhost:9245'************************************************************************

  ERROR   task: Failed to run task "run": exit status 1
2026/04/22 12:31:18 ERROR Process exited with error exec="wails3 task run" err="exit status 1"
2026/04/22 12:31:18 ERROR Could not refresh processes due to execution errors

But openning it in browser works tho.

A work around would be to start the server first in frontend

cd frontend
npm run dev -- --port 9245 --strictPort

Then start wails

wails dev

Updated...
After failed I exited and used command wails3 task run, and the app is running, but I lost dev feature like hot-reload.

Updated...
I have to modify this part in build\config.yml and it working normally now.

dev_mode:
  root_path: .
  log_level: warn
  debounce: 1000
  ignore:
    dir:
      - .git
      - node_modules
      - frontend
      - bin
    file:
      - .DS_Store
      - .gitignore
      - .gitkeep
    watched_extension:
      - "*.go"
      - "*.js" # Watch for changes to JS/TS files included using the //wails:include directive.
      - "*.ts" # The frontend directory will be excluded entirely by the setting above.
    git_ignore: true
  executes:
    - cmd: wails3 task common:dev:frontend # <-  ⚠ This should be ran first, it was second
      type: background
    - cmd: wails3 build DEV=true
      type: blocking
    - cmd: wails3 task run
      type: primary

[alessandro-ooo]

@KiddoV I fixed it by forcing vite on the port 9245 inside the vite.config.ts

export default defineConfig({
  plugins: [react(), tailwindcss()],
  server: {
    port: 9245,
  },

But I believe it needs a better fix because sometimes you need different ports. In my case it worked though.

[fkdp06]

I have the same issue:

[common:frontend:dev:yarn] yarn dev --port 9245 --strictPort
yarn run v1.22.22
$ vite --port 9245 --strictPort
Aug 18 21:04:57.843 INF Retrying...
Aug 18 21:04:58.864 INF Retrying...
Aug 18 21:04:59.875 INF Retrying...
Aug 18 21:05:00.897 INF Retrying...
Aug 18 21:05:01.413 ERR

******************************** FATAL *********************************
*      There has been a catastrophic failure in your application.      *
**************************** Error Details *****************************
unable to connect to frontend server. Please check it is running - FRONTEND_DEVSERVER_URL='http://localhost:9245'************************************************************************

  ERROR   task: Failed to run task "run": exit status 1
21:05:01 [vite] (client) Re-optimizing dependencies because lockfile has changed

  VITE v7.1.9  ready in 6399 ms

  ➜  Local:   http://localhost:9245/ 

This is a startup race condition, not a port or configuration problem.

1. wails3 dev reads build/config.yml, which starts the Go app (primary) and the Vite dev server (background) concurrently.
2. The Go binary's preRun() (in vendored application_dev.go:14-40) reads FRONTEND_DEVSERVER_URL and waits for the frontend server, retrying only 10 × 500ms = ~5 seconds before calling fatal().
3. The Vite dev server took 6.4s (see the terminal log above) to become ready because it logged Re-optimizing dependencies because lockfile has changed (cold/stale dep cache), and the reason is Vue component imports auto-imported by unplugin-vue-components with UI framework resolver.
4. The 5s window expired → FATAL exit → no desktop window was created.

I have temporarily fixed it by changing the vendor (wails) application_dev.go file: Increased the retry window from 10 to 60 retries (500ms each → ~30s) in ./vendor/github.com/wailsapp/wails/v3/pkg/application/application_dev.go:25.

Wails v3.0.0-beta.9 › Wails Doctor

System

┌─────────────────────────────────────────────────────────────┐
| Name | Windows 10 Home |
| Version | 2009 (Build: 26100) |
| ID | 24H2 |
| Branding | Windows 11 Home |
| Platform | windows |
| Architecture | amd64 |
| Go WebView2Loader | true |
| WebView2 Version | 148.0.3967.54 |
| CPU | Intel(R) Core(TM) i3-8100 CPU @ 3.60GHz |
| GPU | NVIDIA GeForce GT 1030 (NVIDIA) |
| Memory | 24GB |
└─────────────────────────────────────────────────────────────┘

Build Environment

┌──────────────────────────────────────────────────────────────────────┐
| Wails CLI | v3.0.0-beta.9 |
| Go Version | go1.26.5 |
| -buildmode | exe |
| -compiler | gc |
| CGO_CFLAGS | |
| CGO_CPPFLAGS | |
| CGO_CXXFLAGS | |
| CGO_ENABLED | 1 |
| CGO_LDFLAGS | |
| DefaultGODEBUG | cryptocustomrand=1,tlssecpmlkem=0,urlstrictcolons=0 |
| GOAMD64 | v1 |
| GOARCH | amd64 |
| GOOS | windows |
└──────────────────────────────────────────────────────────────────────┘

Dependencies

┌──────────────────────────────────────────────────────────────────────────────────────┐
| *Android NDK | Not found. Install with: sdkmanager 'ndk;26.3.11579264' |
| *Android SDK | C:\Users\Admin\AppData\Local\Android\Sdk |
| *Android platform-tools | Installed |
| *Java (Android) | openjdk version "25.0.1" 2025-10-21 LTS |
| MSIX Packaging Tool | Not Installed |
| MakeAppx.exe (Windows SDK) | Not Installed |
| NSIS | Not Installed |
| SignTool.exe (Windows SDK) | Not Installed |
| npm | 11.18.0 |
| docker | *Not installed (optional - for cross-compilation) |
| |
└────────────────────────────── * - Optional Dependency ───────────────────────────────┘

Signing

┌────────────────────────────────────────┐
| macOS Signing | Not configured |
| Windows Signing | Not configured |
| Linux Signing | Not configured (GPG) |
└────────────────────────────────────────┘

Checking for issues

SUCCESS No issues found

Diagnosis

SUCCESS Your system is ready for Wails development!

[taliesin-ai]

Reopened from current beta evidence: the 2026-08-19 morning window includes a Wails v3.0.0-beta.9 Windows reproduction where Vite dependency re-optimization took 6.4 seconds, exceeding the runtime’s roughly five-second readiness window and terminating wails3 dev before the frontend became healthy. Existing PR #5828 is the non-duplicate fix and is green, but still depends on unpublished refresh behavior and needs review/integration evidence before this can close.