Formatters

CoStrict automatically formats files after writing or editing them, keeping generated code consistent with your project's style.

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Built-in Formatters

CoStrict includes formatters for most popular languages. A formatter activates automatically when its requirements are met:

Formatter	Supported Extensions	Requirement
prettier	.js .jsx .ts .tsx .html .css .md .json .yaml and more	prettier in package.json
biome	.js .jsx .ts .tsx .html .css .md .json .yaml and more	biome.json(c) config file present
gofmt	.go	gofmt command available
rustfmt	.rs	rustfmt command available
cargofmt	.rs	cargo fmt command available
ruff	.py .pyi	ruff command available with config
uv	.py .pyi	uv command available
shfmt	.sh .bash	shfmt command available
clang-format	.c .cpp .h .hpp .ino and more	.clang-format config file present
dart	.dart	dart command available
ktlint	.kt .kts	ktlint command available
terraform	.tf .tfvars	terraform command available
zig	.zig .zon	zig command available
rubocop	.rb .rake .gemspec .ru	rubocop command available
standardrb	.rb .rake .gemspec .ru	standardrb command available
pint	.php	laravel/pint in composer.json
mix	.ex .exs .eex .heex and more	mix command available
ocamlformat	.ml .mli	ocamlformat available with config file
ormolu	.hs	ormolu command available
cljfmt	.clj .cljs .cljc .edn	cljfmt command available
gleam	.gleam	gleam command available
nixfmt	.nix	nixfmt command available
dfmt	.d	dfmt command available
air	.R	air command available
htmlbeautifier	.erb .html.erb	htmlbeautifier command available

For example, if your project's package.json includes prettier, CoStrict will automatically use it for formatting.

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How It Works

When CoStrict writes or edits a file, it:

1. Matches the file extension against all enabled formatters
2. Runs the matching format command
3. Applies the result automatically

The entire process runs in the background — no manual steps required.

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Configuration

Customize formatters via the formatter option in costrict.json:

costrict.json

{
  "$schema": "https://opencode.ai/config.json",
  "formatter": {}
}

Each formatter entry supports:

Property	Type	Description
disabled	boolean	Set to true to disable this formatter
command	string[]	Command to run ($FILE is replaced with the file path)
environment	object	Environment variables to set when running the formatter
extensions	string[]	File extensions this formatter handles

---

Disable All Formatters

costrict.json

{
  "$schema": "https://opencode.ai/config.json",
  "formatter": false
}

Disable a Specific Formatter

costrict.json

{
  "$schema": "https://opencode.ai/config.json",
  "formatter": {
    "prettier": {
      "disabled": true
    }
  }
}

Custom Formatter

Override a built-in formatter or add a new one:

costrict.json

{
  "$schema": "https://opencode.ai/config.json",
  "formatter": {
    "prettier": {
      "command": ["npx", "prettier", "--write", "$FILE"],
      "environment": {
        "NODE_ENV": "development"
      },
      "extensions": [".js", ".ts", ".jsx", ".tsx"]
    },
    "custom-markdown-formatter": {
      "command": ["deno", "fmt", "$FILE"],
      "extensions": [".md"]
    }
  }
}

The $FILE placeholder in the command is replaced with the actual file path.