fusengine/ts-config

TypeScript Config (TS 6.0)

Agent Workflow (MANDATORY)

Before writing any tsconfig, use TeamCreate to spawn 3 agents:

1. fuse-ai-pilot:explore-codebase - Detect runtime (Bun/Node/bundler), existing tsconfig, package.json type
2. fuse-ai-pilot:research-expert - Confirm current flags on typescriptlang.org release notes + runtime docs
3. mcp__context7__query-docs - /microsoft/typescript for any flag whose behavior is unclear

After writing, run fuse-ai-pilot:sniper for validation.

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Overview

There are exactly two supported config trajectories in 2026. Pick by runtime, never mix.

| Track | Runtime | module | moduleResolution | |-------|---------|----------|--------------------| | Bundler | Bun, Vite, esbuild, webpack | Preserve | bundler | | Node | Pure Node.js (native type stripping) | nodenext | nodenext |

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Critical Rules

1. Never moduleResolution: node / node10 - deprecated in 6.0, removed in 7.0. Use bundler or nodenext.
2. Always verbatimModuleSyntax: true - both tracks. Forces explicit import type, matches Node's type stripping.
3. strict + noUncheckedIndexedAccess - strict is the 6.0 default; add noUncheckedIndexedAccess explicitly.
4. Set types explicitly - 6.0 defaults types to []. Add ["node"], ["bun"], etc. or you lose globals.
5. Set rootDir when sources are nested - 6.0 defaults rootDir to the tsconfig dir, no longer inferred.

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Decision: which track?

Runs on Bun, or bundled by Vite/esbuild/webpack/Parcel?
  → Bundler track  → references/bundler-track.md

Runs directly on `node file.ts` (type stripping), or emits .js for Node?
  → Node track     → references/node-track.md

Migrating an existing 5.x config / seeing deprecation errors?
  → references/deprecations-6.md  (do this first, then pick a track)

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Reference Guide

Concepts

| Topic | Reference | When to Consult | |-------|-----------|-----------------| | Bundler track | bundler-track.md | Load when configuring a Bun or bundler (Vite/esbuild/webpack) project | | Node track | node-track.md | Load when configuring a pure Node.js project with native type stripping | | 6.0 deprecations | deprecations-6.md | Load when migrating from TS 5.x or fixing deprecation errors |

Templates

| Template | When to Use | |----------|-------------| | tsconfig.bundler.md | Complete Bun/bundler tsconfig | | tsconfig.node.md | Complete pure-Node tsconfig |

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Quick Reference

Bundler / Bun

{
  "compilerOptions": {
    "module": "Preserve",
    "moduleResolution": "bundler",
    "verbatimModuleSyntax": true,
    "allowImportingTsExtensions": true,
    "noEmit": true,
    "strict": true,
    "noUncheckedIndexedAccess": true
  }
}

Pure Node.js (native type stripping)

{
  "compilerOptions": {
    "module": "nodenext",
    "rewriteRelativeImportExtensions": true,
    "erasableSyntaxOnly": true,
    "verbatimModuleSyntax": true,
    "noEmit": true, // only if you never emit .js
    "strict": true
  }
}

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Best Practices

DO

• Add "ignoreDeprecations": "6.0" temporarily while migrating, then remove it before adopting TS 7.0
• Use subpath imports "#/*": "./src/*" in package.json imports (supported under nodenext and bundler)
• Fold any baseUrl prefix into each paths entry (baseUrl is deprecated)

DON'T

• Mix module: Preserve with moduleResolution: nodenext (or vice-versa)
• Set esModuleInterop, allowSyntheticDefaultImports, or alwaysStrict to false (no longer allowed)
• Use enum, namespace with runtime code, or parameter properties in files run by Node's type stripping