This gets windows without WSL to work: fix: wrap binary path resolution with fileURLToPath by jderochervlk · Pull Request #1177 · rescript-lang/rescript-vscode · GitHub
With WSL I am seeing this logged out from the extension.
Did not find rewatch/rescript lockfile in project root, assuming bsb
Could not figure out call args. Maybe build.ninja does not exist yet?
It seems like another path issue.