Moon Guide

Moon Build System Guidelines

Requirements

• Moon ≥ 2.0, Node.js for JavaScript/TypeScript projects.
• Migration from v1: Run moon migrate v2 to automate configuration updates.

Essentials

• Task configuration - Define in .moon/tasks/*.yml for auto-inheritance, see references/task-configuration.md, references/task-inheritance.md
• Tags - Use for categorization, filtering, boundaries, inheritance, see references/tag-based-filtering.md
• Execution - project:task, #tag:task, :task (all), --query, --affected
• Querying - Query projects/tasks by tags, language, or query language, see references/query-language.md
• Configuration - Projects use moon.yml, workspace uses .moon/workspace.yml
• Toolchains - Moon manages language toolchains, configured in .moon/toolchains.yml (plural in v2)
• Caching - Built-in task caching with output definitions, see references/task-configuration.md

Moon 2.0 Key Changes

• command vs script - Use script: for shell features (pipes, redirects, chaining); command: for simple executables only
• Shell by default - Tasks run in shell by default (bash on Unix, pwsh on Windows)
• Deep merging - Configs merge sequentially (not shallow), fileGroups combine instead of replace
• Renamed settings - platform → toolchains, type → layer, toolchain.yml → toolchains.yml
• Env var syntax - $VAR substitutes empty string (not syntax fallback); use ${VAR:-default} for defaults

Gotchas

• Task inheritance flows from .moon/tasks/*.yml (by tag/language) → project moon.yml: overriding requires the same task key in the project file
• Implicit task dependencies via deps: are project-scoped: cross-project deps need <project>:<task> syntax
• moon ci skips persistent server tasks (preset: 'server') and any task with options.runInCI: false, never gate CI-only checks behind a non-CI task
• Project tags drive task inheritance; misspelling a tag silently disables the inherited tasks for that project

Progressive disclosure

• Read references/task-configuration.md - Load when defining or modifying task configurations
• Read references/tag-based-filtering.md - Load when filtering projects or tasks by tags
• Read references/query-language.md - Load when using advanced query syntax
• Read references/task-inheritance.md - Load when setting up task inheritance patterns
• Read references/project-constraints.md - Load when enforcing project boundaries
• Read references/migration-v2.md - Load when migrating from moon v1 to v2
• Read references/docker-multistage.md - Load when building Docker images with moon scaffold