Kotlin — LSP setup

• Builtin server: kotlin-ls — kotlin-lsp
• Extensions: .kt .kts
• Install hint: https://github.com/Kotlin/kotlin-lsp

Install

The official JetBrains Kotlin LSP is pre-release. Download a build from the Kotlin/kotlin-lsp releases and put the kotlin-lsp launcher on PATH.

• macOS: Download the release archive, extract, then symlink the launcher: ln -s /path/to/kotlin-lsp/kotlin-lsp.sh /usr/local/bin/kotlin-lsp
• Linux: Same as macOS — extract the release and place/symlink kotlin-lsp on PATH.
• Windows: Extract the release and add the directory containing kotlin-lsp.bat to PATH (invoke as kotlin-lsp).

Requires a JDK on the machine to run the server.

Confirm it resolves:

command -v kotlin-lsp

Configure

Builtin — usually NO config needed (auto-resolved by extension). Configure only to set priority, init options, override extensions, or disable. Same JSON shape in .codex/lsp-client.json (Codex) AND .opencode/lsp.json (OpenCode/omo):

{ "lsp": { "kotlin-ls": { "priority": 100 } } }

For builtin ids in a PROJECT config, command is supplied automatically — only set priority/initialization/extensions/disabled/env. A fully custom (non-builtin) server with its own command must go in the USER config (~/.codex/lsp-client.json).

Initialization options (only if commonly needed)

None commonly required. If kotlin-lsp cannot find a Java runtime, set JAVA_HOME:

{ "lsp": { "kotlin-ls": { "env": { "JAVA_HOME": "/Library/Java/JavaVirtualMachines/temurin-17.jdk/Contents/Home" } } } }

The server resolves classpath from Gradle/Maven; keep the build descriptor importable.

Alternatives

• fwcd/kotlin-language-server — older community server (not builtin). Still usable but less actively maintained than the official JetBrains one.

Troubleshooting

• PATH: kotlin-lsp on PATH; reopen shell after install.
• Pre-release churn: the JetBrains server is early; pin a known-good release and expect occasional breakage.
• No JDK: server fails to start — install a JDK and/or set JAVA_HOME.
• Slow first import: Gradle resolution on first open can be slow on large projects; let it complete.
• .kts scripts: build/script files resolve more slowly than .kt sources; this is expected.

Verify

bun ../../scripts/verify-lsp.ts path/to/File.kt