Amber CLI

Amber CLI is the standalone command-line companion for Amber V2. CLI 2.0.7 creates the supported Amber 2.0.0-beta.5 ECR web application and includes development, generator, database, and LSP tooling. Its agent tooling also works in plain Crystal apps and shards; see Agent tooling.

Amber V2 is a beta. The release-gated path is a web application on Apple Silicon macOS, x86_64 Linux, or ARM64 Linux. Windows x86-64 passes the complete generated-app smoke in CI, but has no release archive yet. See Generator support before relying on authentication, API-resource, or native output.

Install

Prerequisites: Homebrew 7 or newer and Git. The formula installs Crystal, Minecart, and the native libraries used by the default web app.

Homebrew on macOS or Linux

Run brew trust --tap amberframework/amber_cli, then follow the installation guide to fetch and pin the reviewed tap commit. With that commit checked out, run:

HOMEBREW_NO_AUTO_UPDATE=1 brew install amberframework/amber_cli/amber_cli
amber --version
minecart --version

The single install command brings amber, amber-lsp, Minecart, Crystal, and SQLite/OpenSSL/PostgreSQL/MySQL client libraries. The tap commit fixes formula content and source-archive SHA-256 values. Homebrew-core dependency versions are selected by the installed core catalog, not pinned by this tap.

Direct release archive

The CLI 2.0.7 release has darwin-arm64, linux-x86_64, and linux-arm64 binary archives. A direct archive does not install Minecart or the native dependencies, so Homebrew is the beginner path. Windows x86-64 has no release archive.

version=v2.0.7
platform=darwin-arm64
asset="amber_cli-${platform}.tar.gz"

curl -fLO "https://github.com/amberframework/amber_cli/releases/download/${version}/${asset}"
curl -fLO "https://github.com/amberframework/amber_cli/releases/download/${version}/${asset}.sha256"
shasum -a 256 -c "${asset}.sha256"
tar -xzf "${asset}"
install -m 0755 amber amber-lsp /usr/local/bin/
install -d -m 0755 /usr/local/share/amber_cli/api
install -m 0644 share/amber_cli/api/crystal.yml /usr/local/share/amber_cli/api/
amber --version

On Linux, use sha256sum -c for the checksum. Prefix the install commands with sudo if /usr/local is not writable.

Create and verify a web app

amber new my_app --type web -y
cd my_app
minecart install --frozen --skip-ai-docs
amber assets check
crystal spec
crystal build src/my_app.cr -o bin/my_app
amber watch

amber new runs Minecart by default. It writes exact root dependency pins, a shard.lock with Git tree checksums, .minecart-policy.yml, and .claude/ assistant files, then installs the Claude Code and Codex hooks and prints an amber doctor summary. Commit the generated files. With --no-deps, the first Minecart install and assistant setup are deliberately deferred; run minecart install --strict-pinning --skip-ai-docs and minecart assistant init --skip-ai-docs before frozen installs. Pass --skip-agent-setup to generate the app without the agent files. amber watch recompiles assets before the application whenever an ECR template or a file under app/assets/ changes. Open http://127.0.0.1:3000.

The web template is deliberately small:

• Amber from amberframework/amber, pinned to 2.0.0-beta.5
• ECR views (Slang and Kilt are not supported in Amber V2)
• typed development, test, and production YAML
• branded homepage, controller spec, and fingerprinted CSS, JavaScript, SVG, font, image, and general static-file support
• a browser-native import map with a local JavaScript module entry point
• Grant ORM, Micrate-powered migration commands, and the selected database driver
• SQLite by default, so the first persisted feature needs no database server

The -d pg|mysql|sqlite option selects the generated driver, connection, and development/test URLs. SQLite is the default; PostgreSQL and MySQL expect their respective local servers or a DATABASE_URL.

Static assets: source versus generated output

Write application-owned files in these directories:

app/assets/
├── stylesheets/  # CSS; starter entry: app.css
├── javascript/   # browser modules; starter entry: app.js
├── images/       # SVG, PNG, JPEG, WebP, AVIF, and icons
├── fonts/        # WOFF, WOFF2, TTF, and OTF
└── files/        # PDFs, web manifests, and other downloads

Run the compiler after an authored asset changes outside watch mode:

amber assets build
amber assets check

The build fingerprints every file into public/assets/, rewrites local CSS and JavaScript references, writes SRI and response metadata to public/assets/manifest.json, and creates deterministic gzip siblings for compressible files. public/assets/ is generated and gitignored; do not edit or commit it. Keep stable root files such as public/robots.txt in public/.

In src/views/layouts/application.ecr, resolve authored logical names through stylesheet_link_tag, javascript_importmap_tag, image_tag, and favicon_tag. In CSS, references are relative to that CSS source file; for example, app/assets/stylesheets/app.css uses url("../images/amber-crystal.svg"). The compiler replaces that reference with the image's fingerprinted URL.

Create the first complete resource and its database table:

amber generate scaffold Pet name:string:required species:string:required adopted:bool
amber database migrate
AMBER_ENV=test amber database migrate
crystal spec
amber watch

The generator writes the Grant model to src/models/pet.cr, the request schema to src/schemas/pet_schema.cr, the controller to src/controllers/pet_controller.cr, ECR views to src/views/pet/, a Micrate SQL migration to db/migrations/, and the resource route to config/routes.cr.

Commands

Command	Status	Purpose
amber new APP --type web	Supported	Create the beta web application
amber watch	Supported	Rebuild and restart during development
amber routes	Supported	Inspect application routes
amber pipelines	Supported	Inspect configured pipelines
amber generate	Mixed	Model, scaffold, migration, and core generators supported; auth and API preview
amber database	Supported	Apply, roll back, inspect, redo, and seed the generated database
amber assets build	Supported	Fingerprint app/assets/ into generated public/assets/ output
amber assets check	Supported	Verify manifest, bytes, integrity, MIME, and compressed output without changing it
amber new APP --type native	Preview	Not part of the beta platform guarantee
amber setup:lsp	Available	Register only the project-local Claude amber-lsp plugin
amber setup:agent (amber agent)	Available	Set up Claude Code and Codex in any Crystal project
amber doctor	Available	Check LSP readiness, hook trust, ignore rules, and API lookup status

Run amber --help or amber COMMAND --help for command syntax. The detailed web-app walkthrough and generator table define what is release-gated.

Update and troubleshoot

HOMEBREW_NO_AUTO_UPDATE=1 brew upgrade amberframework/amber_cli/amber_cli
type -a amber
amber --version

If an older Amber V1 executable appears first, remove or rename it or put the new installation directory earlier in PATH. On macOS, include otool -L "$(command -v amber)" in install bug reports; release binaries must not require the retired openssl@1.1 library.

Report CLI, template, or binary problems at https://github.com/amberframework/amber_cli/issues. Include OS/architecture, crystal --version, amber --version, install method, command, and complete output.

Agent tooling for any Crystal project

amber-lsp and amber setup:agent help Claude Code and Codex write Crystal that compiles the first time. They work in Amber V2 apps, plain Crystal apps, and Crystal shards. From the project root:

amber setup:agent   # install Claude Code and Codex hooks and the amber-lsp plugin
amber doctor        # confirm the setup, binary checksum, and agent trust

The agent then looks up each library method before calling it:

amber-lsp lookup 'Dir.mkdir_p'      # class method
amber-lsp lookup 'String#split'     # instance method
crystal build src/my_app.cr 2>&1 | amber-lsp hint

Lookup answers from the project's own code, every shard in lib/, and the Crystal standard library. In Amber V2 apps, edits are also checked against the Amber rules. amber new runs setup:agent automatically; run it again after upgrading. Commit the generated .amber/, .claude/settings.json, and .codex/hooks.json so clones and worktrees share the setup.

The agent tooling guide covers trust prompts, what each hook does, every amber-lsp command, API cards for library authors, and troubleshooting.

Contributing

minecart install --frozen --skip-ai-docs
crystal-alpha tool format --check src spec
crystal-alpha spec

See CONTRIBUTING.md for the project workflow.