`tsonic.json` reference

The project file is a strict JSON object. Unknown fields are rejected. It is not a tsconfig.json, and fields such as compilerOptions, baseUrl, paths, tsconfig, extends, and references are deliberately unsupported.

Project fields

Field	Required	Type	Default	Contract
`$schema`	No	string	none	Editor metadata; accepted but not semantic input
`entryPoint`	Yes	nonempty string	none	Final `.ts` or `.mts` source below `rootDir`; declaration files are rejected
`rootFiles`	No	nonempty distinct string array	`[entryPoint]`	Additional final `.ts`/`.mts` roots; must include `entryPoint` after resolution
`rootDir`	No	nonempty string	project-file directory	Root for source resolution
`outDir`	No	nonempty string	`dist/tsonic`	Compiler-owned publication root
`cacheDir`	No	nonempty string	`.tsonic/cache`	Disposable compiler and target-tool cache; must not overlap `outDir`
`targets`	Yes	nonempty target array	none	One entry per unique target id

Every resolved root file must remain strictly inside the resolved project root. cacheDir is resolved from the project-file directory. Tsonic and target packs write cache data beneath it instead of modifying installed packages. It must be disjoint from outDir so atomic publication never includes or deletes cache state.

Target fields

Field	Required	Type	Contract
`id`	Yes	string	Lowercase ASCII id with single hyphen-separated segments
`surfaces`	No	distinct string array	Explicit source-surface ids; an empty array is valid
`options`	No	object	Validated strictly by the selected target pack

packages is not a target field. Install a capability package through npm instead.

Complete example

{
  "entryPoint": "index.ts",
  "rootFiles": ["index.ts", "startup.ts"],
  "rootDir": "src",
  "outDir": "out",
  "targets": [
    {
      "id": "csharp",
      "surfaces": ["js"],
      "options": {
        "namespace": "Example.Generated",
        "outputType": "Exe"
      }
    },
    {
      "id": "rust",
      "surfaces": ["js"],
      "options": {
        "crateName": "example_generated",
        "outputType": "bin"
      }
    }
  ]
}

$schema is accepted so editors can associate a schema chosen by the user or workspace. Tsonic does not currently publish a canonical schema URL, so the example deliberately omits one.

See the exact C# options and Rust options.

tsonic.json reference

Project fields

Target fields

Complete example

`tsonic.json` reference