Critters

Critters brings the core safety behaviour of vscode-gremlins to Zed.

It scans open files for invisible, misleading, and high-risk Unicode characters, then reports them through Zed diagnostics, hover, and quick fixes.

What v0.1 ships

• suspicious Unicode detection in supported languages
• built-in rules for zero-width characters, bidi controls, non-breaking spaces, soft hyphens, and a conservative typography set
• configurable rules keyed by hexadecimal code point or range
• language-specific overrides keyed by LSP languageId
• one diagnostic per contiguous suspicious run
• hover details with code points, classes, and severity
• Zed extension wrapper in editors/zed that launches a configured or locally installed critters-lsp binary
• quick fixes that remove invisible controls or replace safe cases such as no-break spaces and curly quotes with ASCII

What it does not promise yet

• arbitrary inline decorations
• custom gutter icons
• overview ruler styling
• semantic token styling

Those are current parity gaps against vscode-gremlins, and they are documented rather than hand-waved.

Configuration

Add settings under lsp.critters-lsp.settings in ~/.config/zed/settings.json.

{
  "lsp": {
    "critters-lsp": {
      "settings": {
        "max_diagnostics_per_document": 250,
        "rules": {
          "0080-00FF": {
            "description": "LATIN-1 SUPPLEMENT",
            "severity": "error",
            "class": "latin-1",
            "zero_width": false
          }
        },
        "language_overrides": {
          "markdown": {
            "rules": {
              "00A0": {
                "severity": "none"
              }
            }
          }
        }
      }
    }
  }
}

Repository layout

• crates/critters-core contains reusable configuration, rules, and scanner logic.
• crates/critters-lsp contains the standalone language server binary.
• editors/zed contains the thin Zed extension wrapper.

Local development

1. Enter the optional dev shell, or use your host Rust toolchain.
2. Build the server.
3. Build the Zed extension WebAssembly module.
4. Install editors/zed as the dev extension in Zed.
5. Point Zed at the locally built binary, or put critters-lsp on your PATH.

nix develop
cargo build --package critters-lsp
rustup target add wasm32-wasip2
cargo build --package critters-zed --target wasm32-wasip2

The release CI builds critters-lsp archives for Windows, macOS, and Linux from bare semver tags such as 0.1.0. Critters is not published to the upstream Zed extension marketplace yet.

Example local binary override:

{
  "lsp": {
    "critters-lsp": {
      "binary": {
        "path": "/absolute/path/to/critters/target/debug/critters-lsp"
      }
    }
  }
}

Documentation

• Configuration
• Parity matrix
• Limitations