TS2349: This expression is not callable - in CI

By Kaveh Alemi·Latchkey

You invoked a value that the compiler does not consider a function.

What this error means

Type-checking fails with TS2349 stating the type has no call signatures, often on a union or a default-import mishap.

src/run.ts(14,3): error TS2349: This expression is not callable. Type 'Number' has no call signatures.

Diagnose it: which tsconfig and which compiler?

A TypeScript error that appears only in CI usually means the runner is compiling with a different config or a different compiler version than your editor. Your editor uses the workspace TypeScript and the nearest tsconfig.json; CI uses whatever the lockfile resolved and whatever config the build script names.

# what CI will actually use
npx tsc --version
npx tsc --showConfig | head -40

# which files are in the program (a missing include is a common cause)
npx tsc --listFiles | wc -l

# type-check only, no emit, same as most CI gates
npx tsc --noEmit

Common causes

How to fix it

Call the right value

1. Narrow a union so only the callable member is invoked
2. For interop modules, enable esModuleInterop or import * as

{
  "compilerOptions": { "esModuleInterop": true }
}

Fix the type if it is wrong

1. Correct the declaration so the value has a call signature

Pin the compiler so unrelated updates cannot break the gate

TypeScript adds errors in minor releases. An unpinned compiler turns a routine dependency update into a red build on code nobody touched, which is the most common false alarm in a TypeScript CI pipeline.

// package.json
{
  "devDependencies": {
    "typescript": "5.6.3"   // exact, not ^5.6.3
  }
}

How to prevent it

• Enable esModuleInterop for CommonJS interop and narrow unions before calling.

Frequently asked questions

Related guides

References

• Node.js documentation
• npm CLI documentation
• GitHub Actions documentation