After upgrading to bud 6.0 and following first path from the Bud v6.0.0 released whenever I am trying to use yarn build / dev the error comes up:
/node_modules/dotenv-expand/lib/main.js:20
const keyParts = parts[2].split(':-')
^
TypeError: Cannot read properties of undefined (reading 'split')
at /var/www/html/xxx.xx/bedrock/web/app/themes/xxx/node_modules/dotenv-expand/lib/main.js:20:33
at Array.reduce (<anonymous>)
at _interpolate (/var/www/html/xxx.xx/bedrock/web/app/themes/xxx/node_modules/dotenv-expand/lib/main.js:6:18)
at expand (/var/www/html/xxx.xx/bedrock/web/app/themes/xxx/node_modules/dotenv-expand/lib/main.js:50:32)
at get (file:///var/www/html/xxx.xx/bedrock/web/app/themes/xxx/node_modules/@roots/bud/lib/context/env.js:24:30)
at file:///var/www/html/xxx.xx/bedrock/web/app/themes/xxx/node_modules/@roots/bud/lib/context/env.js:33:13
at Array.reduce (<anonymous>)
at new Env (file:///var/www/html/xxx.xx/bedrock/web/app/themes/xxx/node_modules/@roots/bud/lib/context/env.js:31:34)
at makeContext (file:///var/www/html/xxx.xx/bedrock/web/app/themes/xxx/node_modules/@roots/bud/lib/context/index.js:21:17)
at async bud (file:///var/www/html/xxx.xx/bedrock/web/app/themes/xxx/node_modules/@roots/bud/lib/cli/index.js:58:21)
So escaping $ in variable value should fix the issue:
Well thanks, it worked, but a new error comes in:
Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: No "exports" main defined in /var/www/html/xx/bedrock/web/app/themes/xx/node_modules/@roots/bud-framework/package.json imported from /var/www/html/xx/bedrock/web/app/themes/xx/node_modules/@roots/bud-hooks/lib/service.js
at new NodeError (node:internal/errors:371:5)
at throwExportsNotFound (node:internal/modules/esm/resolve:440:9)
at packageExportsResolve (node:internal/modules/esm/resolve:645:7)
at packageResolve (node:internal/modules/esm/resolve:873:14)
at moduleResolve (node:internal/modules/esm/resolve:929:18)
at defaultResolve (node:internal/modules/esm/resolve:1044:11)
at ESMLoader.resolve (node:internal/modules/esm/loader:422:30)
at ESMLoader.getModuleJob (node:internal/modules/esm/loader:222:40)
at ModuleWrap.<anonymous> (node:internal/modules/esm/module_job:76:40)
at link (node:internal/modules/esm/module_job:75:36) {
code: 'ERR_PACKAGE_PATH_NOT_EXPORTED'
}
This has probably something to do with outdated packages.
Try npm outdated and then update the bud-related packages, one by one.
Well everything is up to date 
So, i’ve found the issue.
Everything is working when i delete salt keys from the .env file.
So basically i’ve generated new ones and everything is working. Keys were generated via WordPress Salts.
These are the faulty ones:
AUTH_KEY='N$d<475]Syb6/|DSA&q7z2l;Li@[hfJx)o?riz-X&s<xXz$7!]?H8nxCDQtwn^RE'
SECURE_AUTH_KEY='#x*B^Vlppd.<`t4IciZ$$UejKC`uB7s;aO$6FC2`jg]^e(|v=CH+]Rk(J2?,OaZg'
LOGGED_IN_KEY='nP$^4oL-%}Ia*l3z9{ki]1QXqW{Cy99{.94(o+0EZMMhAFtPb0H|#T8*`I,Cs0/_'
NONCE_KEY='jZ5;l`RilJM+X)@Ww[hx|MWRX_JCkz4>SiN@BCQppaOR_+QV&|^H`ya4z6}qO.32'
AUTH_SALT='I{gr5LCTf&=j}tjb[d7>q(:fR2RY>`,z7u[A*N;30`[[35>W]wE]g)cSw,1Ww,z9'
SECURE_AUTH_SALT='AzCIP/R`T#&4-Oz<V46L@X@Xqnv+VhDNbt+YuUmeicq,^Mhk9Tthg2>W9RPJ(m`?'
LOGGED_IN_SALT='?wsA|k20xv!VY4KvBk0B{U&F!}IRzxp>r--^F|9(t3vKFWt<`+pnL6{2d6HJmqPS'
NONCE_SALT='$=et66]kTt(+($c:mIRW1oh+B=E[gCQXFJr<VO+8J=a)*?,kOL;?^.5xac41%9pH'
I think it’s the kind of issue @ben should look into and investigate further 
It seems like bud was tripping up on your dotenv. it shouldn’t fail like that.
were the old values quoted? if they weren’t and they contained regexp-like characters, dotenv-expand might have choked on them.
This is because of an unescaped $ being interpolated by bud as variable expansion.
I was able to reproduce the issue exactly and write tests around it. Thanks for bringing it up @fakenso.
The next release of bud will not try to interpolate environment variables that are not sourced from [projectRoot]/.env. You will still need to escape $ in theme .env file but otherwise this shouldn’t be such a mystery in the future.