bug: --import-alias flag crashes with TypeError when used in CI mode

[bmarianome]

Provide environment information

System:
OS: macOS 26.2
CPU: Unknown
Memory: 122.91 MB / 16.00 GB
Shell: 5.9 - /bin/zsh
Binaries:
Node: 24.4.1 - /opt/homebrew/bin/node
npm: 11.4.2 - /opt/homebrew/bin/npm
pnpm: 10.8.0 - /opt/homebrew/bin/pnpm

Describe the bug

Using the --import-alias (or -i) flag in CI mode causes a TypeError: i.replace is not a function crash after the boilerplate is successfully installed.

The issue is in cli/src/helpers/setImportAlias.ts (line 24-25), where .replace() is called on the importAlias value. Commander parses the --import-alias option with an optional value ([alias]), which can result in the value being true (boolean) instead of a string, causing the crash.

Expected behavior: passing --import-alias "@/" should set the import alias to @/ without errors.

Reproduction repo

No repo needed — this is reproducible with any fresh scaffold using the published CLI.

To reproduce

1. Run the following command:

pnpm dlx create-t3-app@latest my-app --CI --tailwind --appRouter --eslint --import-alias "@/"

2. The CLI scaffolds successfully and installs boilerplate, but then crashes:

Using: pnpm

✔ my-app scaffolded successfully!

Adding boilerplate...
✔ Successfully setup boilerplate for tailwind
✔ Successfully setup boilerplate for envVariables
✔ Successfully setup boilerplate for eslint

Aborting installation...
TypeError: i.replace is not a function

3. The same happens with the short flag -i "@/".

4. Without --import-alias, the command works fine:

pnpm dlx create-t3-app@latest my-app --CI --tailwind --appRouter --eslint

Additional information

[this is AI]

The root cause is in cli/src/cli/index.ts line 147, where the Commander option is defined as:

.option(
  "-i, --import-alias [alias]",
  "Explicitly tell the CLI to use a custom import alias",
  defaultOptions.flags.importAlias
)

The [alias] (optional value) syntax allows Commander to return true instead of the actual string value in some cases. Then in cli/src/helpers/setImportAlias.ts:

const normalizedImportAlias = importAlias
    .replace(/\*/g, "")
    .replace(/[^/]$/, "$&/");

true.replace() throws TypeError.

Possible fixes:

• Change [alias] to <alias> (required value) in the Commander option definition
• Add defensive type checking before calling .replace()

[Ti-03]

Confirmed on the latest published release.

Environment

• create-t3-app@7.40.0 (current npm latest)
• macOS (Darwin 25.5.0), Node 26.0.0, npm 11.12.1

Steps

npx create-t3-app@7.40.0 my-app --CI --tailwind --appRouter --eslint --import-alias "@/"

Outcome — scaffolds, then crashes with TypeError: i.replace is not a function, exactly as reported.

Root cause in 7.40.0: in the published build the flag is registered as a plain boolean — .option("-i, --import-alias", "...", "~/"), with no [alias] value placeholder — so Commander discards the passed "@/" and sets importAlias to true. The guard is if (importAlias !== "~/"), and true !== "~/", so setImportAlias() runs and calls .replace() on a boolean → the crash.

One clarification on the original analysis: in the released build it isn't an optional [alias] resolving to true — there's no value placeholder at all, so the flag never accepts a value. For what it's worth, the current main source does use -i, --import-alias [alias], which would accept the string for this command — but that isn't in 7.40.0.