feat: Core Tooling & Scaffold Consistency Audit

[alton47]

Is your feature request related to a problem? Please describe.

Currently, the create-t3-app scaffolding process is experiencing "configuration drift" where various tool combinations (Biome, Prisma, Tailwind v4, and Oxc) are clashing on initial project generation. This creates immediate git diff churn and CI failures in what should be a "clean" repository state.

Describe the solution you'd like to see

• Artifact Churn: Prisma-generated files (generated/prisma) are being caught in the Prettier/Biome formatting loop, causing persistent git diffs immediately after scaffolding (bug: Prisma generated files under generated/prisma are reformatted by Prettier, causing persistent git diff churn in fresh T3 scaffold #2217).
• Tooling Conflicts: Incompatibilities between Biome’s useSortedClasses and Tailwind v4 resolution (biome useSortedClasses rule is counter intuitive #2126, bug: Tailwind CSS v4.x + Next.js ESM Module Resolution Issue #2127) are leading to linting errors on fresh installs.
• CI Fragility: The --import-alias flag is triggering TypeError crashes in CI environments, indicating a regression in the CLI's argument parsing logic (bug: --import-alias flag crashes with TypeError when used in CI mode #2215).

Describe alternate solutions

Any thoughts?

Additional information

No response

[sxtzz]

Solutions for create-t3-app Configuration Drift

Prisma Artifact Churn (#2217)

Add generated/prisma/ to .prettierignore and .gitignore. Run git rm -r --cached generated/prisma/. Change format scripts to target only source files:

"format:write": "prettier --write \"src/**/*.{ts,tsx,js,jsx,mdx}\""

Biome + Tailwind v4 Conflicts (#2126, #2127)

Adopt Biome as the sole tool. Remove Prettier. Configure biome.jsonc:

{
  "linter": {
    "rules": {
      "correctness": {
        "useSortedClasses": {
          "level": "error",
          "options": {
            "functions": ["cn", "clsx", "twMerge", "twJoin"]
          }
        }
      }
    }
  },
  "css": {
    "parser": {
      "tailwindDirectives": true
    }
  }
}

If retaining both, set useSortedClasses: "off" in Biome and add Tailwind v4 ESM compatibility to next.config.js:

webpack: (config) => {
  config.resolve.extensionAlias = {
    '.js': ['.js', '.ts', '.tsx'],
    '.mjs': ['.mjs', '.mts', '.mtsx']
  };
  return config;
}

--import-alias CI Crash (#2215)

Upgrade ESLint to v9 and use @eslint/compat with fixupPluginRules for Drizzle plugin. Alternatively, omit --import-alias during scaffolding and set paths in tsconfig.json manually:

"paths": { "@/*": ["./src/*"] }

[cschanhniem]

The configuration drift issues outlined in this audit share a common root cause: the template generation logic accumulates packages and their associated config fragments without reconciling them when a package is swapped. Adding Biome alongside Prettier produces two formatters with overlapping useSortedClasses rules, Prisma adds files to the workspace that Prettier then tries to format, and the import-alias flag creates tsconfig paths that ESLint may or may not be configured to resolve.

A structured approach would be to define a config generator per tool package that produces only the config fragments relevant to that package, then merge them with conflict resolution. Currently, the templates in cli/template/extras/config/ are static files overlaid on the scaffold. Making them composable - where each package (Prisma, Drizzle, Tailwind, Biome, ESLint, Prettier) registers its config requirements and the scaffolder resolves overlaps before writing files - would prevent the multi-tool collision problem without manual intervention.

For the specific Biome + Prettier conflict, the simplest resolution is to detect when both are selected and set Biome's useSortedClasses to off while leaving the Tailwind class sorting to Prettier's plugin. The scaffolder already tracks which packages are selected in the pkg tracker, so the conflict detection could live in the config generation step.