> ## Documentation Index > Fetch the complete documentation index at: https://soulforge.proxysoul.com/llms.txt > Use this file to discover all available pages before exploring further. # AST editing > The first AST-native AI editor. Edits by symbol, not string. `ast_edit` is the first AI coding tool to edit TypeScript and JavaScript through the AST instead of text matching. It addresses symbols by kind and name, mutates them structurally, and writes the result back. Micro-edits cost a handful of tokens and never fail on whitespace. You don't invoke `ast_edit` directly. The agent picks it automatically for TypeScript and JavaScript files. This page is a reference for what it can do. ## Origin The AST-first approach comes from my own Master's thesis in Computer Science, [*Typed vs Untyped Programming Languages*](https://www.diva-portal.org/smash/record.jsf?pid=diva2%3A1690910\&dswid=-6127) (co-authored with Artur Matusiak, 2022), and its reference implementation [JS Typer](https://github.com/proxysoul/Javascript-Typer). The thesis demonstrated that programmatic JavaScript-to-TypeScript conversion could be done entirely through ts-morph AST mutations rather than string manipulation. `ast_edit` is the direct descendant of that work, applied to AI coding. ## Examples Change a function's return type: ```ts theme={null} ast_edit({ path: "src/api.ts", action: "set_return_type", target: "function", name: "fetchUser", value: "Promise", }) ``` Make a function async and add a parameter — one atomic batch: ```ts theme={null} ast_edit({ path: "src/api.ts", operations: [ { action: "set_async", target: "function", name: "fetchUser", value: "true" }, { action: "add_parameter", target: "function", name: "fetchUser", value: "cache: boolean" }, { action: "add_named_import", value: "./types", newCode: "User" }, ], }) ``` Rename a class method: ```ts theme={null} ast_edit({ path: "src/store.ts", action: "rename", target: "method", name: "UserStore.fetch", value: "load", }) ``` Replace a whole function body: ```ts theme={null} ast_edit({ path: "src/util.ts", action: "set_body", target: "function", name: "parseInput", newCode: "return JSON.parse(raw);", }) ``` Batch edits are all-or-nothing — if any fails, none are applied. ## Targets | Target | Addressed by | | ------------------------------------------------------------------------ | -------------------------------------- | | `function`, `class`, `interface`, `type`, `enum`, `variable`, `constant` | `name` | | `method`, `property` | `"ClassName.member"` or `"member"` | | `arrow_function` | `name` (targets `const fn = () => {}`) | | `constructor` | `ClassName` | ## Action reference | Action | Effect | | --------------------------------------------------------------------------------------------------------------- | ------------------------------------------- | | `set_type` | Variable/property/parameter type annotation | | `set_return_type` | Function return type | | `set_initializer` / `remove_initializer` | Variable initializer | | `set_value` | Enum member value | | `set_async` / `set_generator` | Toggle `async` / `function*` | | `set_export` / `set_default_export` | Toggle export modifiers | | `set_abstract` / `set_static` / `set_readonly` / `set_scope` / `set_optional` / `set_overrides` / `set_ambient` | Class-member modifiers | | `set_const_enum` / `set_declaration_kind` | Misc modifiers | | `rename` | Declaration-only rename | | `remove` | Delete the declaration | | `add_parameter` / `remove_parameter` | Function/method parameters | | Action | Effect | | ----------------------------------------------------------------------------------------- | ---------------------------- | | `set_body` | Replace function/method body | | `add_statement` / `insert_statement` / `remove_statement` | Statement-level | | `add_property` / `remove_property` | Interface/class properties | | `add_method` / `remove_method` / `add_constructor` / `add_getter` / `add_setter` | Class members | | `add_member` / `remove_member` | Enum / type-literal members | | `add_decorator` / `remove_decorator` | Decorators | | `add_overload` | Function overload signatures | | `set_extends` / `add_extends` / `remove_extends` / `add_implements` / `remove_implements` | Inheritance | | `add_type_parameter` | Generic type parameters | | `add_jsdoc` / `remove_jsdoc` | JSDoc blocks | | `unwrap`, `set_structure`, `extract_interface` | Structural rewrites | | Action | Effect | | ----------------- | -------------------------------------------------- | | `replace` | Replace a whole symbol | | `replace_in_body` | AST-anchored substring replace (unique match only) | | Action | Effect | | ----------------------------------------------------------------------------------------------- | ------------------------------------------------------------------ | | `create_file` | New file (pass `newCode` as content) | | `add_import` / `remove_import` / `add_named_import` / `remove_named_import` | Imports | | `set_module_specifier` | Change import path | | `add_export_declaration` / `add_named_reexport` | Re-exports | | `add_namespace` | Namespace declarations | | `organize_imports` / `fix_missing_imports` / `fix_unused` | Cleanup | | `add_function` / `add_class` / `add_interface` / `add_type_alias` / `add_enum` / `add_variable` | Append top-level declarations | | `insert_text` | Insert at an anchor (`"after-imports"`, `"before-exports"`, index) | ## Supported files `.ts`, `.tsx`, `.js`, `.jsx`, `.mts`, `.cts`, `.mjs`, `.cjs`. For other files the agent falls back to `edit_file` / `multi_edit`. ## Safety * File snapshotted before the edit — rejects if changed on disk mid-flight. * Atomic batches: all or none. * `undo_edit` reverses `ast_edit` the same as `edit_file`. * Pre/post diagnostics — new type errors flow back to the agent immediately.