Same issue here when I run genkit start after initializing Genkit with a brand new Next.js project:

Error: Error in app process: spawn C:\Users\Ariel\AppData\Roaming\npm\node_modules\genkit\node_modules\@genkit-ai\tools-common\node_modules\.bin\tsx ENOENT

Note: I noticed that ...\genkit\node_modules\@genkit-ai\tools-common\node_modules weren't installed, so I installed them manually with npm install, and verified that ...\genkit\node_modules\@genkit-ai\tools-common\node_modules\.bin\tsx is now installed in that location; however, I still get the same ENOENT error as if it can't find tsx.

OS: Windows 11 Home
Version node: 20.12.2
Version npm/npx: 10.8.0
Version tsx: 4.15.7

I'm not sure if this has any relation to my previous observation about the ...\tools-common\node-modules, but if I delete the genkit-tools.conf.js that gets generated by genkit init then the above ENOENT error goes away.

Here are the contents of that file on my system:

module.exports = { runner: { mode: 'harness', files: ['./src/app/*.ts'], }, };

Note that I still get the above ENOENT error even when there is an index.ts or generate.ts file present in the app directory to be compiled.

The Next.js docs don't mention running npm install which is probably needed in some situations, e.g if you clone a repo and just try to run genkit start you'll likely run into a "module not found" error. I'll start a thread in the Genkit discord server about making the docs clearer there.

I haven't been able to reproduce the error by cloning the repo @dario-digregorio provided. I'll try with a new Next.js project.

EDIT: I've reproduced this by following the docs in a brand new Next.js project

Ah the problem is something doesn't have executable permissions. Doing chmod +x to the tsx path referenced fixed this for me i think.

Actually when i do a fresh install of Genkit globally, the node_modules for the tools package doesn't exist at all now, weird.

Seems relevant, I think this is part of the problem:

https://github.com/firebase/genkit/blob/main/genkit-tools/common/src/runner/runner.ts#L180