tauri-apps/tauri · error

failed to run `{before_dev}`

Error message

failed to run `{before_dev}`

What it means

Panic in `tauri dev` when SharedChild::spawn fails to launch the configured build > beforeDevCommand. This is a spawn failure (binary cannot be started at all), distinct from the non-zero exit code case which is reported separately above it. Typical cause: the command's binary does not exist or is not executable.

Source

Thrown at crates/tauri-cli/src/dev.rs:207

            "`{before_dev}` with `{}`",
            if cfg!(windows) { "cmd /S /C" } else { "sh -c" }
          ),
          error,
        })?;
        if !status.success() {
          crate::error::bail!(
            "beforeDevCommand `{}` failed with exit code {}",
            before_dev,
            status.code().unwrap_or_default()
          );
        }
      } else {
        command.stdin(Stdio::piped());
        command.stdout(os_pipe::dup_stdout().unwrap());
        command.stderr(os_pipe::dup_stderr().unwrap());

        let child = SharedChild::spawn(&mut command)
          .unwrap_or_else(|_| panic!("failed to run `{before_dev}`"));

        let child = BEFORE_DEV.get_or_init(move || child);
        std::thread::spawn(move || {
          let status = child
            .wait()
            .expect("failed to wait on \"beforeDevCommand\"");
          if !(status.success() || KILL_BEFORE_DEV_FLAG.load(Ordering::SeqCst)) {
            log::error!("The \"beforeDevCommand\" terminated with a non-zero status code.");
            exit(status.code().unwrap_or(1));
          }
        });

        let _ = ctrlc::set_handler(move || {
          kill_before_dev_process();
          exit(130);
        });
      }
    }

View on GitHub (pinned to 52e4b6e71d)

Solutions

1. Run the exact beforeDevCommand manually in the frontend directory; install what it complains about (`npm install`, `corepack enable`)
2. Prefer package-runner form like `npm run dev` / `pnpm dev` instead of raw binary names so local node_modules/.bin is used
3. Fix or clear build > beforeDevCommand in tauri.conf.json if the frontend needs no dev server step

Example fix

// before (tauri.conf.json)
"build": { "beforeDevCommand": "vite", "devUrl": "http://localhost:5173" }

// after
"build": { "beforeDevCommand": "npm run dev", "devUrl": "http://localhost:5173" }

#!/usr/bin/env bash
# verify the beforeDevCommand binary resolves before starting tauri dev
cmd=$(jq -r '.build.beforeDevCommand // ""' src-tauri/tauri.conf.json | awk '{print $1}')
[ -z "$cmd" ] || command -v "$cmd" >/dev/null || { echo "beforeDevCommand binary '$cmd' not found; run npm install"; exit 1; }

When it happens

Trigger: beforeDevCommand set to a package-manager script before dependencies are installed (no node_modules/.bin), referencing a tool that is not on PATH (`vite`, `yarn`, `pnpm`), or a command string whose binary cannot be resolved by the OS.

Common situations: Fresh clone without `npm install`; switching package managers (pnpm-lock but command says yarn); CI images missing Node tooling; Windows needing `.cmd` resolution through `npm run` rather than the raw binary.

Related errors

• beforeDevCommand `{}` failed with exit code {}
• invalid permission {p}
• Couldn't recognize the {} folder as a Tauri project. It must
• No external IP detected.
• failed to read missing addr file {}: {e}

AI-assisted analysis of tauri-apps/tauri@52e4b6e71d (2026-08-20). Data as JSON: /api/errors/238ffa9d2bb42cda. Report an issue: GitHub.