# symtether > Broken URLs 404. Broken code references don't. #sym: verifies markdown references against the code itself, and fails CI when they break. Links like `[x](path/file.ts#sym:Class.method)` point at a symbol in that file; `npx symtether check` fails CI when a reference is broken. Tethered Docs. Real Code. Zero Hallucinations. ## Table of Contents ### Docs - [Guide](https://symtether.dev/guide.md) - [Adding a language](https://symtether.dev/adding-a-language.md) - [The `#sym:` reference syntax (SPEC v1)](https://symtether.dev/spec.md)