Three Windows-only bugs in the web-dashboard build path. Each is small,
scoped, and verified end-to-end on Windows 11 — including under a stock
cmd.exe / PowerShell console with its default cp1252 encoding.
1. `sync-assets` shells out to Unix-only commands
web/package.json hard-codes `rm -rf … && cp -r …`. Neither exists on
Windows cmd.exe. `hermes_cli/main.py::_build_web_ui` runs npm via
subprocess (which on Windows defaults to cmd.exe), so the prebuild
hook crashed before Vite ever ran and the dashboard never built.
Fix: web/scripts/sync-assets.mjs — ~20 lines of Node using fs.rmSync
+ fs.cpSync (stdlib, Node >= 16.7). No new deps, identical behavior
on POSIX and Windows.
2. Build failures were silent
_build_web_ui ran both subprocess calls with capture_output=True and
never relayed the captured buffers on failure. Users saw 'Web UI
build failed' and nothing else — no stdout, no stderr, no hint that
the real problem was 'rm is not recognized'.
Fix: inner _relay() helper that decodes and prints stdout + stderr
(utf-8, errors='replace') whenever a step returns non-zero. Replaces
the existing stderr_tail-only relay on the build path; success path
is unchanged. (stderr_tail is preserved for the stale-dist fallback
branch added by #23817.)
Salvaged from #13368 by @johnisag onto current main. Conflict
resolution preserves main's improvements:
- _run_npm_install_deterministic() (replaces bare subprocess.run for
npm install)
- npm-build retry-after-sleep for Windows boot-time races (#23817)
- stale-dist fallback for non-interactive callers (#23817)
Closes#25073, #13368.
