Site fails to execute functions within a pnpm monorepo

[robations]

Describe the bug A clear and concise description of what the bug is.

Although static assets are served by netlify serve, no functions seem to be working and the index of the site (http://localhost:8888/) returns "404 Not Found".

To Reproduce Steps to reproduce the behavior:

1. Generate a new site npx create-remix@latest --template netlify/remix-template
2. (choosing functions, rather than edge)
3. Test the site working
4. Translocate site as a workspace within a pnpm monorepo:
   a. add missing dependencies (pnpm complains about react and react-dom missing)
   b. I had an issue with netlify-cli trying to run an unrelated workspace package (which also happens to have a netlify.toml file): added build.base: "packages/remix-netlify"
   c. tsconfigPaths was reporting errors in unrelated packages (added root parameter)
   d. Delete package-lock.json and node_modules
   e. Reinstall repo deps with pnpm i
5. Test the site within monorepo working correctly with remix vite:dev
6. netlify serve fails with 404 error at root of site and .netlify/functions-serve is missing (compared with original site)
7. Static client assets are served correctly (favicon.ico and CSS/JS under /assets/...)

Expected behavior A clear and concise description of what you expected to happen.

The site should work within a monorepo, or would expect some simple configuration to make it work.

Screenshots If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: MacOS
• Browser: n/a
• Version: @netlify/remix-adapter: 2.5.1

Smartphone (please complete the following information):

• Device: n/a
• OS: n/a
• Browser n/a
• Version n/a

Additional context Add any other context about the problem here.

Can potentially create a new monorepo for testing if not easily reproducible.

It seems like part of the Netlify code is still mis-identifying a path, but it's not clear what or where.

[robations]

Notable difference:

.netlify within monorepo:

.netlify in isolated site:

[robations]

I've also just noticed that if I add build.base: "packages/remix-netlify" I get a spurious nested directory added within the workspace package:

Whereas without build.base, the netlify CLI gets very confused about paths (tries to build within packages/foo even though it is filtered to packages/remix-netlify).

For context, I have something like 15 other netlify sites working correctly within this repo.

[robations]

If there's any legwork I can do to help with this, let me know.

E.g. additional logs, a reproduction repository

My context is that I created a quick prototype with remix (partly to weigh up remix as a framework) but now I can't easily deploy it so I've had to move on to other jobs.

[robations]

Note that I've run routine upgrades today (including taking @netlify/functions from v2 to v4) and I get pretty much the same behaviour.

Deploying onto Netlify.com itself gives:

Linked function log (from Netlify.com):

ERROR  Uncaught Exception 	{"errorType":"Error","errorMessage":"Cannot find module '/var/task/node_modules/.pnpm/node_modules/react-dom/server' imported from /var/task/node_modules/.pnpm/@netlify+remix-adapter@2.6.1_typescript@5.8.3_vite@5.4.19_@types+node@22.15.27_sass@1.89.0_terser@5.40.0_/node_modules/@netlify/remix-adapter/dist/index.mjs\nDid you mean to import react-dom@15.7.0_react@15.7.0/node_modules/react-dom/server.js?","code":"ERR_MODULE_NOT_FOUND","url":"file:///var/task/node_modules/.pnpm/node_modules/react-dom/server","stack":["Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/var/task/node_modules/.pnpm/node_modules/react-dom/server' imported from /var/task/node_modules/.pnpm/@netlify+remix-adapter@2.6.1_typescript@5.8.3_vite@5.4.19_@types+node@22.15.27_sass@1.89.0_terser@5.40.0_/node_modules/@netlify/remix-adapter/dist/index.mjs","Did you mean to import react-dom@15.7.0_react@15.7.0/node_modules/react-dom/server.js?","    at new NodeError (node:internal/errors:405:5)","    at finalizeResolution (node:internal/modules/esm/resolve:332:11)","    at moduleResolve (node:internal/modules/esm/resolve:1029:10)","    at moduleResolveWithNodePath (node:internal/modules/esm/resolve:876:12)","    at defaultResolve (node:internal/modules/esm/resolve:1255:79)","    at ModuleLoader.defaultResolve (node:internal/modules/esm/loader:404:12)","    at ModuleLoader.resolve (node:internal/modules/esm/loader:373:25)","    at ModuleLoader.getModuleJob (node:internal/modules/esm/loader:250:38)","    at ModuleWrap.<anonymous> (node:internal/modules/esm/module_job:76:39)","    at link (node:internal/modules/esm/module_job:75:36)"]}