The plugin protocol

rigsmith has one extension mechanism, used for two kinds of plugin:

1. Ecosystem / language adapters — dotnet, node, go, cargo, the desktop ecosystems tauri and electron, a generic regex adapter, and future python, …
2. Changelog generators — default, keepachangelog, emoji, JSON-for-a-website, …

Both are external commands invoked over a versioned JSON-on-stdin / result-on-stdout contract — the same delegation model the tools already use for git, gh, and the native package managers. A plugin is a stateless one-shot pure function — the ideal shape for a subprocess. (This was chosen deliberately over Go plugin .so, HashiCorp go-plugin (gRPC), and WASM.)

The load-bearing rule: built-ins dogfood the contract

The built-in adapters and the built-in changelog renderer are not a privileged bypass. They implement the very same Go interfaces (plugin.Ecosystem, plugin.ChangelogGenerator) that the subprocess transport mirrors. An external plugin and a built-in are interchangeable.

Why this matters: if our own default can be driven entirely through the request object, the contract is complete. If a golden can't be reproduced from the request alone, the contract is missing a field — and we find out because our own renderer breaks, not because a third party complains.

plugin.Ecosystem (interface)
├── ecosystem/dotnet    ─┐ in-process built-ins
├── ecosystem/node       │  (reference implementations):
├── ecosystem/gomod      │  language adapters, the tauri/electron
├── ecosystem/cargo      │  desktop ecosystems, and a generic
├── ecosystem/tauri      │  regex adapter
├── ecosystem/electron   │
├── ecosystem/regex     ─┘
└── plugin.SubprocessEcosystem  ── external command over JSON

plugin.ChangelogGenerator (interface)
├── planner built-in renderer    ── in-process reference
└── plugin.SubprocessChangelogGenerator ── external command over JSON

Versioning

APIVersion is an integer (currently 1). The engine sends the highest version it speaks; a plugin that doesn't recognize it must exit non-zero rather than guess. Additive fields don't bump the version; removing, renaming, or re-meaning a field does.

Ecosystem adapter contract

Invoked as plugin <method> with a JSON request on stdin and a JSON response on stdout:

Method	Request	Response	Purpose
info	{apiVersion}	EcosystemInfo{id, displayName, capabilities, manifestPatterns}	identity + capabilities
detect	{repoRoot}	{detected: bool}	does this ecosystem apply here?
discover	{repoRoot, sourcePath}	{packages: [Package]}	enumerate releasable packages
set-version	{package, newVersion, dependencyUpdates}	—	stamp a version (format-preserving)
publish	{package, packageSource, access, dryRun}	{published, skipped, message}	publish via the native package manager (idempotent)

Full reference

The complete protocol — every struct, the changelog-generator contract, and the reference Node plugin — is in docs/PLUGIN-PROTOCOL.md.