Formatters

Successful native write, edit and apply_patch calls format every written file before LSP diagnostics and the next model call. Moved files use their destination; deleted files are skipped. Clean formatting adds no transcript copy. Failures append a bounded Formatting: section to the existing tool result in chat and History; the original edit remains successful. Cancellation stops the formatter process group and subsequent commands.

A project without .mendcode/formatter.json pays one failed file read per written file and starts no process. A configured formatter always finishes, or is killed at its limit and reported under Formatting:, before the tool result is returned: the file never changes after the model was told the write succeeded.

Project configuration is .mendcode/formatter.json. Omit it or use false to disable formatting, true to enable builtins, or an object to enable builtins with overrides. Configuration is read on each invocation; changes apply without restarting.

{
  "prettier": { "environment": { "PRETTIER_LOG_LEVEL": "warn" } },
  "oxfmt": { "disabled": true },
  "biome": { "disabled": true },
  "custom": {
    "command": ["project-fmt", "--write", "$FILE"],
    "extensions": [".custom"],
    "environment": { "FORMAT_MODE": "strict" }
  }
}

command is an argv array, never implicitly a shell. $FILE is replaced with the absolute filename in every argument. environment (or the v2 alias env) extends only the child environment. Builtin overrides retain extensions and BUN_BE_BUN=1 unless replaced. Custom entries require command and extensions; disabled removes an entry. An explicit builtin command bypasses its project/experimental gate. Invalid entries are reported and never executed.

Prettier/Biome match JS/TS families, HTML, CSS/SCSS/Sass/Less, Vue/Svelte, JSON/JSONC, YAML, TOML, XML, Markdown/MDX and GraphQL. Oxfmt matches JS/TS families. Actual syntax support depends on the installed version/plugins, as in v1.

Resolution prefers the nearest project node_modules/.bin, then ancestors through the enclosing Git worktree, then PATH. Commands run in the session project directory, sequentially in registry order; all matching enabled formatters run. UTF-8 BOMs are preserved. A file has a four-second formatter budget; at the limit the formatter's process group is killed and the result says timed out. Diagnostics after the write have their own, much shorter wait (lsp.md). Same-file invocations are serialized. Formatter stdout/stderr and environment values are never included in replies.

Protocol: formatter.status { directory } and formatter.file { directory, path }; typed helpers: client.formatterStatus(directory) and client.formatFile(directory, path). Status returns name/extensions/enabled/reason and config issues. File returns structured formatter outcomes. Neither command is permitted to read-only peers. No new TUI page or slash command is needed.

Other stacks (B14)

Every preset needs an installed executable. Project gates search up to the enclosing worktree; Pint's executable remains relative to the session directory, as in v1. Disabling ruff or uv disables both backends. An explicit command bypasses builtin gates and help probes; extensions and child environment are configurable. Probes share the file's formatter budget and cancellation, and status probes stop with the manager. Only safe failure reasons reach chat/History or clients.

No formatter is installed or downloaded automatically. Real-tool validation requires installed binaries; local fake executables prove configuration, process lifecycle and daemon/client/engine integration only.