Building a Golem Application with golem build

Both golem and golem-cli can be used — all commands below work with either binary.

Usage

golem build --yes

Run this from the application root directory (where the root golem.yaml is located). It builds all components defined in the project. Always pass --yes to avoid interactive prompts.

What golem build Does

The build is a multi-step pipeline:

1. Check — verifies that required build tools are installed (e.g., cargo for Rust, npm/node for TypeScript).
2. Build — executes the build commands defined in golem.yaml for each component. These commands are language-specific:
   • Rust: runs cargo build --target wasm32-wasip2 (or with --release for the release preset).
   • TypeScript: runs a multi-stage pipeline — tsc for type checking, golem-typegen for metadata extraction, rollup for bundling, then injects the bundle into a prebuilt QuickJS WASM and optionally preinitializes it.
   • Scala: runs Scala.js compilation, JavaScript linking, QuickJS WASM injection, agent wrapper generation, and WASM composition.
3. Add Metadata — embeds component name and version into the output WASM binary.
4. Generate Bridge — generates bridge SDK code if the project uses inter-component communication.

Up-to-date Checks

golem build tracks file hashes of sources and targets. If nothing changed since the last build, steps are skipped automatically. Use --force-build to bypass this.

Build Output

The final WASM artifact is placed in golem-temp/agents/ under the application root:

• Rust (debug preset): golem-temp/agents/<component_name_snake_case>_debug.wasm
• Rust (release preset): golem-temp/agents/<component_name_snake_case>_release.wasm
• TypeScript: golem-temp/agents/<component_name_snake_case>.wasm
• Scala: golem-temp/agents/<component_name_snake_case>.wasm

The component name in snake_case is derived from the component name in golem.yaml. For example, a component named my-app:rust-main produces my_app_rust_main_debug.wasm.

Available Options

Build Configuration in golem.yaml

Build commands are defined per component template and preset in golem.yaml:

componentTemplates:
  rust:
    presets:
      debug:
        default: true
        build:
        - command: cargo build --target wasm32-wasip2
        componentWasm: "target/wasm32-wasip2/debug/<name>.wasm"
        outputWasm: "golem-temp/agents/<name>_debug.wasm"

The build section is a list of steps. Each step can be:

• command: — a shell command to execute
• injectToPrebuiltQuickjs: — injects a JS bundle into a QuickJS WASM (TypeScript/Scala only)
• preinitializeJs: — preinitializes the JS runtime in the WASM (TypeScript/Scala only)

Each step can specify sources and targets for incremental builds, dir for the working directory, and env for environment variables.

Cleaning Build Artifacts

golem clean

This removes golem-temp/ and any other directories listed in the clean section of each preset.

Common Build Errors

• Missing wasm32-wasip2 target (Rust): run rustup target add wasm32-wasip2
• Missing npm packages (TypeScript): golem build automatically runs npm install if package.json is present but node_modules is missing
• Type errors (TypeScript): fix the errors in .ts source files; the tsc step runs with --noEmit false --emitDeclarationOnly