A build or a deploy failed

A build that fails changes nothing: the release that was serving keeps serving, and the deployment is recorded as failed with its whole output. The command ends with:

Deployment failed: ...

followed by what failed, in the words of the program that failed.

Where to read it

• The build's log: in the console, the application's Deployments tab; open the deployment. From a terminal, noust app deploy-log wrenfield.io.
• The application's own log (what it printed once it ran): noust logs wrenfield.io. It is not the build's.
• A failed health check carries its own evidence, below:

The application did not answer the health check.

followed by every probe that failed and the last lines of the application's journal. They say whether it did not start, did not listen, or answered with an error.

The causes, in the order you meet them

The wrong version of Node.js, Python or PHP

The build fails on syntax or a dependency that needs a newer runtime. Pin the version in the repository: runtime: node@22 in the build: block of noust.yaml, or a .nvmrc, a .python-version, or require.php in composer.json (Runtimes). Or set it for this server only: noust app build set wrenfield.io --runtime node@22.

A variable the build needs is missing

The framework says which (Next.js, Vite and Nuxt read some variables at build time). Add it, for the build only if that is all it is for, and deploy again:

noust env set wrenfield.io --build-only --stdin    # then type NAME=value, and Ctrl+D
noust update wrenfield.io

In the console: the application's Environment page.

The build ran out of memory

FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory

or the build is simply killed. On a small server, add swap and deploy again: noust server swap create --size 2G.

A command uses &&, a pipe or $VARIABLE

A build, start or hook command is one program and its arguments. It never runs in a shell, so npm ci && npm run build passes && to npm as an argument. Commit a script and run it instead: build: ./scripts/build.sh (The build block).

noust.yaml has a key Noust does not know

Unknown key 'pre_deploys' in hooks

The file is read strictly, because a misspelt phase would be a migration that silently never runs. Every refusal names the field. Fix the spelling and push.

The sandbox

Builds run as the unprivileged account noust-build, in a systemd sandbox that cannot read the rest of the machine. A build that writes outside its directory, or expects root, fails there. noust app sandbox status wrenfield.io says whether the sandbox is on, and noust app sandbox test wrenfield.io builds what the next update would build, in the sandbox, without activating it: the failure can be reproduced without touching what serves.

A migration failed

A pre_deploy hook that fails stops the deploy before anything serves the new version, and its output is the error (What a hook failing means). Fix the migration and deploy again.

The framework builds for a platform this server is not

SvelteKit builds for the platform its adapter names, and adapter-auto builds for none this server is.

Use @sveltejs/adapter-node to run it as a server, or @sveltejs/adapter-static to serve files, set it in svelte.config.js and deploy again. The message ends with the command for a build you run some other way (SvelteKit).

The start script is missing

Missing script: "start"

npm found no start script in package.json, so the application never started. Add the script, or tell Noust what to run: noust app build set wrenfield.io --start 'node server.js'.

Start again from nothing

noust update wrenfield.io --no-cache empties the build cache, installs the dependencies again instead of reusing the serving release's, and rebuilds even when the branch has nothing new.