EC
TS6400
TypeScriptERRORNotableConfigHIGH confidence

Project 'X' is up to date but needs to update timestamps of output files that...

Production Risk

Build will fail; resolve before shipping.

What this means

A compiler configuration error (TS6400): Project 'X' is up to date but needs to update timestamps of output files that are older than input files. This diagnostic is emitted by the TypeScript compiler when project 'X' is up to date but needs to update timestamps of output files that are older than input files.

Why it happens
  1. 1Incorrect TypeScript syntax or type usage
  2. 2Type mismatch between declared and actual value
How to reproduce

TypeScript compiler reports TS6400 during type checking.

trigger — this will error
trigger — this will error
// Triggers TS6400
// Project 'X' is up to date but needs to update timestamps of output files that are older than input files

expected output

error TS6400: Project 'X' is up to date but needs to update timestamps of output files that are older than input files

Fix

Fix the tsconfig.json option

WHEN When a compiler option is invalid or missing

Fix the tsconfig.json option
// tsconfig.json
{
  "compilerOptions": {
    // Review and correct the flagged option
  }
}
// Run: npx tsc --showConfig to see effective config

Why this works

TypeScript validates tsconfig.json options; check the official tsconfig reference for valid values.

Sources
Official documentation ↗

TypeScript Compiler Diagnostics

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