There are very likely raise an error: unable to connect to frontend server Please check it is running - FRONTEND_DEVSERVER_URL='http://localhost:9245'

[L4zy-Sheep]

Mar 16 21:29:42.439 INF Waiting for frontend dev server to start... url=http://localhost:9245
task: [common:install:frontend:deps] npm install
Mar 16 21:29:42.950 INF Retrying...
Mar 16 21:29:43.954 INF Retrying...
Mar 16 21:29:44.958 INF Retrying...
Mar 16 21:29:45.961 INF Retrying...
Mar 16 21:29:46.965 INF Retrying...
Mar 16 21:29:47.467 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

[sciarrk]

same for me with Wails3 and Vite 8.0.1 (same issue with 8.0.0)

Mar 20 00:41:10.745 INF Build Info: Wails=v3.0.0-alpha.74 Compiler=go1.26.1 GOOS=windows GOAMD64=v1 -buildmode=exe -compiler=gc -gcflags="all=-l" DefaultGODEBUG="cryptocustomrand=1,tlssecpmlkem=0,urlstrictcolons=0" CGO_ENABLED=0 GOARCH=amd64
Mar 20 00:41:10.747 INF AssetServer Info: middleware=true handler=true devServerURL=http://localhost:9245
Mar 20 00:41:10.748 INF Waiting for frontend dev server to start... url=http://localhost:9245      
Mar 20 00:41:10.748 INF Platform Info: Go-WebView2Loader=true WebView2=146.0.3856.62 ID=25H2 Name="Windows 10 Enterprise" Version="2009 (Build: 26200)" Branding="Windows 11 Enterprise"
Mar 20 00:41:11.259 INF Retrying...
Mar 20 00:41:12.266 INF Retrying...
Mar 20 00:41:13.272 INF Retrying...
Mar 20 00:41:14.277 INF Retrying...
Mar 20 00:41:15.282 INF Retrying...
Mar 20 00:41:15.783 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
2026/03/20 00:41:15 ERROR Process exited with error exec="wails3 task run" err="exit status 1"

[esemplare]

I had to remove the double dash from the run dev command since I'm using pnpm as example...

dev:frontend:
    summary: Runs the frontend in development mode
    dir: frontend
    deps:
      - task: install:frontend:deps
    cmds:
-      - pnpm run dev -- --port {{.VITE_PORT}} --strictPort
+      - pnpm run dev --port {{.VITE_PORT}} --strictPort

[leaanthony]

This error means Wails started before the frontend dev server was ready. A few things to check:

1. Package manager double-dash issue (pnpm)
As @esemplare noted, pnpm does not need -- before Vite flags. Change your Taskfile.yml:

-  - pnpm run dev -- --port {{.VITE_PORT}} --strictPort
+  - pnpm run dev --port {{.VITE_PORT}} --strictPort

2. Port conflict
If something else is already using port 9245, Vite will fail to start. Try changing VITE_PORT in your Taskfile.yml.

3. Slow install / first run
On first run, npm install can take longer than Wails's connection timeout. Wait for the install to finish before running wails3 dev.

4. Vite version incompatibility
Vite 6+ changed some dev server defaults. If you recently upgraded, try pinning to Vite 5.x or check the v3 release notes for known compatibility notes.

If none of these fix it, please share your full Taskfile.yml and package.json so we can dig deeper.

[jasonbot]

This is hacky, but I changed my build\config.yml to read:

  executes:
    - cmd: wails3 build DEV=true
      type: blocking
    - cmd: wails3 task common:dev:frontend
      type: background
    - cmd: sleep 5
      type: blocking
    - cmd: wails3 task run
      type: primary

The sleep gives the vite server time to get up and running before the run task, which has an aggressively small timeout for waiting for the backend server to be ready.

[Alan3344]

For me, I commented out - task: install:frontend:deps, and it worked normally.

I've modified the frontend configuration to "dev": "vite --host ::",

I'm honestly exasperated. I didn't have this issue with Wails v2, where projects would run immediately after initialization. Now, using the latest version, a freshly downloaded project (wails3 init -n FileTool -t vue) just won't run. First, there's the port occupancy issue caused by Hyper-V(Windows Sandbox), and then wails3 dev fails to start correctly.

I tried this two months ago and it didn't work then either, but then it suddenly started working again the next day for no apparent reason. This code configuration in build\Taskfile.yml can run successfully without being commented out.

Console output

Need documentation? Run: wails3 docs ♥ If Wails is useful to you or your company, please consider sponsoring the project: wails3 sponsor task: [windows:run] bin/MediaViewer.exe Apr 29 00:05:41.758 INF Build Info: Wails=v3.0.0-alpha.74 Compiler=go1.26.1 -compiler=gc -gcflags="all=-l" DefaultGODEBUG="cryptocustomrand=1,tlssecpmlkem=0,urlstrictcolons=0" CGO_ENABLED=0 GOARCH=amd64 GOOS=windows GOAMD64=v1 -buildmode=exe Apr 29 00:05:41.759 INF AssetServer Info: middleware=true handler=true devServerURL=http://localhost:9245 Apr 29 00:05:41.759 INF Platform Info: Go-WebView2Loader=true WebView2=147.0.3912.86 ID=21H2 Name="Windows 10 Enterprise LTSC 2021" Version="2009 (Build: 19044)" Branding="Windows 10 企业版 LTSC" Apr 29 00:05:41.782 INF Waiting for frontend dev server to start... url=http://localhost:9245 Apr 29 00:05:42.297 INF Retrying... task: [common:install:frontend:deps] npm install Apr 29 00:05:43.301 INF Retrying... Apr 29 00:05:44.304 INF Retrying...

up to date, audited 33 packages in 879ms

4 packages are looking for funding
run npm fund for details

4 moderate severity vulnerabilities

To address issues that do not require attention, run:
npm audit fix

To address all issues (including breaking changes), run:
npm audit fix --force

Run npm audit for details.
task: [common:dev:frontend] npm run dev -- --port 9245 --strictPort
Apr 29 00:05:45.308 INF Retrying...

frontend@0.0.0 dev
vite --host :: --port 9245 --strictPort

Apr 29 00:05:46.310 INF Retrying...

VITE v5.4.21 ready in 425 ms

➜ Local: http://localhost:9245/
➜ Network: http://172.31.208.1:9245/
➜ Network: http://192.168.32.1:9245/
➜ Network: http://172.25.240.1:9245/
➜ Network: http://192.168.111.4:9245/
➜ Network: http://192.168.199.1:9245/
➜ Network: http://192.168.52.1:9245/
➜ Network: http://192.168.8.100:9245/
➜ Network: http://172.21.160.1:9245/
➜ Network: http://172.29.128.1:9245/
Apr 29 00:05:46.812 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
2026/04/29 00:05:46 ERROR Process exited with error exec="wails3 task run" err="exit status 1"
2026/04/29 00:05:46 ERROR Could not refresh processes due to execution errors

I've asked Gemini Pro over 30 questions, and it still hasn't been able to solve it.