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With experimental settings you can try some of the new features and options that are not stable for now, but capable to improve usage of cli in some way.

Experimental flags are provided in tramvai.json and should be passed separately for server and build configurations.


"$schema": "./node_modules/@tramvai/cli/schema.json",
"projects": {
"app": {
"name": "app",
"root": "src",
"type": "application",
"experiments": {
"minicss": {
"useImportModule": true
"webpack": {
"cacheUnaffected": true
"transpilation": {
"loader": {
"development": "swc",
"production": "babel"

CLI settings


  • serverRunner="process"|"thread" - use different ways to run the server app in development mode. "thread" most of the time is faster, but might lead to some bugs, especially when running cli though nodejs api


  • serverRunner="thread" - if you get any problems, can switch to "process", it is not experimental and can be safely used

Webpack settings

Webpack by itself has a list of experimental flags which might be passed directly to webpack through experiments.webpack.


  • cacheUnaffected=true - should improve build performance in development mode


Flags are specified through experiments.minicss and allows to enable experimental settings for mini-css-extract-plugin

  • useImportModule - enables a special way to compile css modules that should improve build time and decrease memory usage. More details in the official docs


  • useImportModule=true - enabled by default as this improves build time and provides better css related error descriptions


Settings for the js-ts transpilation process

  • loader="babel"|"swc" - use specific transpiler


To use loader="swc" you need to install special integration package:

npx tramvai add --dev @tramvai/swc-integration


  • loader="babel" - babel in not experimental setup and can be safely used


Settings for the minification process

  • minifier="terser"|"swc" - use specific minifier for terser webpack plugin.


  • minifier="terser" - terser is default minifier for terser plugin