Language servers

The code editor in Argus for Mac gets its diagnostics, hover, go to definition and completion from language servers. They run on the machine that hosts your sessions — so a Mac attached to another Argus over the network gets the same intelligence without installing anything itself.

Argus starts a server the first time you open a file in that language in a session, and stops it after ten minutes with no open files. At most six run at once across all sessions; the one used least recently makes way. Deleting a session stops its servers.

The status bar shows each server's state. Not found means the server isn't installed; Failed means it crashed more than three times in five minutes — click Retry once you've fixed whatever was wrong. A server that needs setup wasn't started on purpose, because its answers would be wrong — hover over it to see why (so far only Swift does this, see Swift).

Which languages, and where the server comes from

Language	Server	Comes from
TypeScript, JavaScript, TSX/JSX	typescript-language-server	Bundled with Argus
JSON, CSS/SCSS/Less, HTML	vscode-json-language-server, -css-, -html- (from VS Code)	Bundled with Argus
YAML	yaml-language-server	Bundled with Argus
Swift	sourcekit-lsp	Xcode
C, C++, Objective-C	clangd	Xcode
Kotlin	kotlin-lsp (JetBrains)	Your PATH — install it first
Python	pyright-langserver (or basedpyright-langserver)	Your PATH — install it first
Go	gopls	Your PATH — install it first
Rust	rust-analyzer	Your PATH — install it first
Ruby	ruby-lsp	Your PATH — install it first

Argus never downloads a language server for you.

Open Quickly (⇧⌘O) and workspace symbol search (⌘T) work without any server: Argus keeps its own index of the definitions in a session's files, and merges in what a running server knows on top.

Bundled servers

These ship inside the app and need nothing from you.

• TypeScript and JavaScript use the typescript package in your project's node_modules when there is one, so diagnostics match your build. Projects without it — or on TypeScript 7, which no longer ships the classic language service — use the TypeScript 6 that Argus bundles.
• JSON validates package.json and tsconfig.json against their public schemas, which it downloads from schemastore.org the first time.
• YAML picks up schemas from schemastore.org for files it recognises, such as GitHub workflows.

Xcode servers

Swift and C-family files use the servers in your active Xcode toolchain (the one xcode-select -p points at), found with xcrun. If you don't have Xcode, Argus also looks for sourcekit-lsp and clangd on your PATH.

clangd reads compile_commands.json at the root of your project when there is one.

Swift

sourcekit-lsp only gives honest answers when it knows how your code is built, so Argus looks at what each Swift file belongs to:

• A Swift package. Files under a Package.swift get a server rooted at that package, so a repository with several packages gets one per package. Diagnostics, completion and go to definition work across the package.
• An Xcode project. Files in a repository with an .xcodeproj or .xcworkspace (outside Pods, DerivedData, node_modules and .build) go through a build server — see below. Once xcode-build-server is installed, the app's local packages go through it too, since Xcode builds them for the app's platform. Without it, a local package still gets its own server unless it lists only iOS-family platforms (it would fail to import UIKit when built for the Mac).
• A lone Swift file, outside any package or project, runs in single-file mode. Several loose files in one folder don't: sourcekit-lsp can't see how they fit together and would report each other's types as missing. The status bar says Swift: limited here.

Swift in Xcode projects

On its own, sourcekit-lsp doesn't know an Xcode project's SDK, targets or modules, so it reports errors like No such module 'UIKit' for code that builds fine. Argus gets those build settings from xcode-build-server, which reads them from your project's Xcode build logs. Until it can, Argus doesn't start sourcekit-lsp for the project at all — highlighting, folding and search keep working, and the status bar says what's missing:

1. Swift: needs a build server — install it, then click Retry:

   brew install xcode-build-server
   

   Argus finds it on your PATH or in Homebrew's usual places.

2. Swift: build once to enable — build the app once in this session, with its run command or in Xcode. xcode-build-server needs a build log for this worktree; a build in another checkout doesn't count. Argus notices the build by itself and starts Swift intelligence a few seconds after it finishes.

Then you get diagnostics, completion, hover, go to definition, references and rename across the app and its local packages. Build again after adding files or changing build settings; xcode-build-server picks up the new log on its own.

To set things up, Argus writes a buildServer.json at the root of the worktree, unless there already is one (or a .bsp folder) — then it uses yours as it is. It keeps the file out of git through the repository's .git/info/exclude, not your .gitignore. The file follows one scheme:

• the one your xcodebuild run command builds (-scheme), when it has one;
• else the shared scheme that builds an app and has the project's name;
• else the first scheme that builds an app, else the first scheme.

A -derivedDataPath in that run command is followed too. When Argus had to pick among several schemes, hovering the status bar item says which. To switch, delete buildServer.json and click Retry, or run xcode-build-server config -scheme <name> in the worktree yourself.

Servers on your PATH

Argus finds these the same way it finds git and your agents: on the PATH your login shell sets up, so anything your terminal can run, Argus can too. Install with your usual tool, then reopen the file (or click Retry):

Language	Install
Python	npm install -g pyright or pipx install basedpyright
Go	go install golang.org/x/tools/gopls@latest (make sure ~/go/bin is on your PATH)
Rust	rustup component add rust-analyzer
Ruby	gem install ruby-lsp
Kotlin	brew install JetBrains/utils/kotlin-lsp (pre-release; heavy on large Gradle projects)

Formatting

Format Document (⇧⌥F) and format on save use the project's own formatter first, the version installed in the worktree with the project's config, run in the worktree. The status bar shows which one applies to the open file next to the indentation, and turns amber with the reason when its last run failed.

Formatter	Files	Used when
Prettier	JS, TS, JSX, TSX, JSON, CSS, SCSS, Less, HTML, Vue, Markdown, YAML, GraphQL	A Prettier config file or a "prettier" key in package.json (a shareable config like "@acme/prettier-config" works), or prettier in the package's dependencies. Argus runs the prettier in the worktree's node_modules, nearest the file first, so monorepo packages get their own; .prettierignore is honoured
SwiftFormat	Swift	A .swiftformat file, with swiftformat installed (brew install swiftformat)
swift-format	Swift	A .swift-format file; uses swift-format on your PATH, else the one in Xcode 16 and later
gofmt	Go	A go.mod, with gofmt on your PATH
Ruff or Black	Python	ruff.toml, .ruff.toml or [tool.ruff] in pyproject.toml (Ruff); [tool.black] (Black)

Anything else falls back to the file's language server. Argus never installs a formatter, and organize imports or eslint --fix on save aren't supported.

Turning servers off

Language servers can be switched off altogether, or per language, in the Mac app's Editor settings. A language that's off never starts a server.