🪞 GUIHO Mirror

Open source project versioning for Bun, npm, JSR, and Git.

Mirror is a powerful, deterministic CLI for semantic project versioning. It reads a single version source, calculates the next semantic version, builds a transparent release plan, and safely applies it to configured outputs like package.json, jsr.json, and Git tags.

source -> version engine -> plan -> outputs

Mirror ships as a native Bun-compiled CLI binary. Direct installers run the native binary without requiring Node.js or Bun at runtime. Package-manager installs use a small Bun launcher with install-time and on-demand native binary download. Git is required only for Git-based workflows (source: "git", output: ["git"], or commit/tag/push operations).

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🚀 Quick Start

Installation

NPM package: @guiho/mirror

npm install -D @guiho/mirror
# or
bun add -d @guiho/mirror

Direct native binary install on macOS/Linux:

curl -fsSL https://raw.githubusercontent.com/CGuiho/mirror/main/mirror/install.sh | sh

Direct native binary install on Windows:

irm https://raw.githubusercontent.com/CGuiho/mirror/main/mirror/install.ps1 | iex

Initializing

Create a default configuration file for your project type:

mirror init package.json
# or
mirror init jsr.json
# or
mirror init git

Typical Workflow

# See current version
mirror version current

# Preview a patch release
mirror version plan patch

# Apply a minor release and create a Git commit & tag
mirror version apply minor --commit --yes

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📖 Documentation

Mirror's architecture is based on a predictable read-plan-apply lifecycle, making it safe and easy to automate. It is designed to be easily consumed by humans and AI agents.

Project Model

Mirror uses a strict release model:

• Project: The package, repository, application, or directory being versioned.
• Source: The single adapter Mirror reads the current version from.
• Output: The adapters Mirror writes the next version to.
• Plan: The read-only description of all intended changes before any mutation occurs.

Adapters

Adapters connect Mirror to different versioning ecosystems:

• package.json: Reads/writes the version field in a package.json file.
• jsr.json: Reads/writes the version field in a jsr.json file.
• git: Reads versions from Git tags and creates release tags/commits. Requires Git to be installed and accessible in PATH.

CLI Commands

Mirror provides a concise CLI with three main command groups:

mirror init

Creates or reconciles a mirror.config.toml file in the current directory. On an interactive terminal, mirror init asks step-by-step questions (version source, outputs, package path, auxiliary paths, tag template, commit/push) with defaults you accept by pressing Enter. Pass flags to answer non-interactively, and in CI / non-TTY environments it uses flags + defaults without prompting.

• mirror init (interactive wizard, or flags + defaults when non-interactive)
• mirror init package.json / mirror init jsr.json / mirror init git (source shortcut)
• Flags: --source, --output, --package-file, --jsr-file, --auxiliary, --tag-template, --name, --preid, --commit, --push, --non-interactive, --yes

Defaults: source package.json, outputs package.json + git.

mirror config

Validates and inspects configuration.

• mirror config show: Prints the resolved configuration.
• mirror config check: Validates configuration without output.
• mirror config schema: Prints the comprehensive configuration reference. Use --format json to print a JSON Schema for editor autocomplete.

mirror agents

Installs Mirror-aware agent guidance for projects that use AI coding agents.

• mirror agents install local: Synchronizes the bundled guiho-s-mirror skill at .agents/skills/guiho-s-mirror/SKILL.md.
• mirror agents install global: Synchronizes the bundled guiho-s-mirror skill at ~/.agents/skills/guiho-s-mirror/SKILL.md.
• mirror agents instructions: Creates or updates AGENTS.md with the GUIHO Mirror semantic versioning section.

mirror version

Manages the version lifecycle.

• mirror version current: Prints the current project version.
• mirror version next <target>: Prints the next version without side-effects.
• mirror version plan <target>: Builds and prints the release plan.
• mirror version apply <target>: Applies the release plan.

Targets supported: major, premajor, minor, preminor, patch, prepatch, prerelease, or an exact semantic version (e.g., 2.0.0).

Configuration (mirror.config.toml)

Mirror looks for configuration via the --config <path> flag, ./mirror.config.toml, or ./config/mirror.config.toml.

schema = 1

[project]
name = "my-project"                    # Optional. Explicit project name.
name_source = "package.json"           # Optional. "package.json" or "jsr.json"

[version]
scheme = "semver"                      # Required. Only "semver" is supported.
source = "package.json"                # Required. "package.json", "jsr.json", or "git"
output = ["package.json", "git"]       # Required. Adapters to write to.
prerelease_id = "alpha"                # Optional. e.g., creates 1.0.1-alpha.0

[package]
path = "package.json"                  # Optional. Override path to package.json
auxiliary_paths = []                    # Optional. Extra package.json files that mirror the main version

[jsr]
path = "jsr.json"                      # Optional. Override path to jsr.json

[git]
tag_template = "{name}@{version}"      # Optional. Supported: "v{version}", "{name}@{version}", "{name}/v{version}"
commit = false                         # Optional. Create release commits. Default: false.
push = false                           # Optional. Push release refs. Default: false.
allow_dirty = false                    # Optional. Allow dirty Git worktree. Default: false.

[agents]
write_changelog = true                 # Optional. Tell agents changelog edits are allowed. Default: true.
changelog_path = "CHANGELOG.md"         # Optional. Changelog file path for agents. Default: "CHANGELOG.md".
auto_agents_md = true                  # Optional. Insert Mirror guidance into AGENTS.md when present. Default: true.
auto_skill_install = true              # Optional. Install guiho-s-mirror globally when missing or outdated. Default: true.

Agent Automation

Mirror is designed to be safely used by AI agents. Project commands automatically check for AGENTS.md and the guiho-s-mirror skill, then add the Mirror guidance or install the missing, legacy-named, or outdated skill when automation is enabled. Running mirror with no arguments also performs this configured agent setup before showing help.

Set write_changelog = false when agents should skip changelog edits during release preparation. Set changelog_path = "docs/CHANGELOG.md" when the changelog is not at the project root. Set auto_agents_md = false to opt out of automatic guidance insertion, or auto_skill_install = false to opt out of automatic global skill installation.

Safety & Git Automation

By default, mirror version apply prevents accidental mutations:

• Fails on a dirty Git worktree (unless --allow-dirty is used).
• Requires --yes to skip interactive confirmation (non-interactive environments).
• Never pushes release refs automatically unless configured or --push is passed.

When combining file outputs (package.json, jsr.json) with Git tag output, Mirror requires either --commit or --push so that the tag attaches to the release commit containing the updated files. For Git-only outputs, --commit will not create an empty commit; it simply tags HEAD.

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🛠️ Development

Development tasks require Bun. Run from the mirror/ directory:

cd mirror
bun install
bun run typecheck
bun test
bun run build
bun run binary

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🎵 The Origin of the Name

The name Mirror was inspired by the music track "MIRROR" by SleepyThePrince & DJ Dadda, featured on the album "Blackout".

In a deeper sense, the name also fits the purpose of the library perfectly: just as looking in a mirror reflects an exact snapshot of who we are, this library reflects the exact state and version of whatever you are building.