Because applying an edit needs the exact state ID and an exact match of path and edits, an assistant cannot quietly widen a change between the preview you read and the write that lands. The expiry is short by default, which is a security property rather than an annoyance: if you walked away, the approval is gone and the edit has to be re-proposed.
A TypeScript MCP server for making exact, line-based edits to text files. An edit names a line range and either a literal string or a regex to match within it, so replacements preserve the surrounding formatting and indentation rather than rewriting whole lines. Every edit can run as a dry run that returns a unified diff and a state ID; nothing touches the file until that state ID is approved.
- Line-based edits by literal match or regex, across single or multiple lines, several edits at once, previewable before they apply — `edit_file_lines`
- A two-step commit: the dry run returns a diff plus a state ID, and applying requires that ID and an exact match of file path and edits — `approve_edit`
- Specific lines read back with surrounding context, to verify content before and after an edit — `get_file_lines`
- Search that hands you the line numbers to edit: text or regex, case sensitivity, whole-word matching, configurable context, with defaults of 2 context lines, 100 maximum matches and a 10-line context cap — `search_file`
- Whitespace handled deliberately: literal matches are whitespace-normalised, original indentation is preserved in replacements, and `strMatch` and `regexMatch` cannot be combined in one edit
- Guardrails that fail loudly: overlapping regex patterns are rejected, and so is a line affected by multiple edits
No account and no key. Build from a clone with `npm install` and `npm run build`. The server must be started with one or more allowed directories — `node build/index.js <allowed-directory> [additional-directories...]` — and every file operation is restricted to them, with symlink escapes and parent-directory traversal rejected. `MCP_EDIT_STATE_TTL` sets how long an edit state stays approvable, in milliseconds, defaulting to 60000; an expired or unknown state ID returns an error rather than applying anything. The package is `edit-file-lines` 0.1.0.