Sokel Plugin SDK

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Write a Sokel plugin in Go, Python or TypeScript. Declare what your operations take and return; the SDK handles registration, transport, credentials, file transfer, heartbeats and reconnects.

OnIssuesList(p, func(ctx sokel.Ctx, in *IssuesListIn) (*IssuesListOut, error) {
    issues, err := client.ListIssues(ctx, in.Project, in.State)
    if err != nil {
        return nil, err
    }
    return &IssuesListOut{Issues: issues, Count: len(issues)}, nil
})

That handler signature is generated from your declaration. There is no map[string]any anywhere in your code, and no second copy of the contract to keep in sync by hand.

The same is true in the other two languages — the declaration just lives in a language-neutral manifest.yml instead of a Go package:

async def issues_list(ctx: Ctx, in_: IssuesListIn) -> IssuesListOut:
    issues = await client.list_issues(in_.project, in_.state)
    return IssuesListOut(issues=issues, count=len(issues))

onIssuesList(p, async (ctx, in_) => {
  const issues = await client.listIssues(in_.project, in_.state);
  return { issues, count: issues.length };
});

Why plugins dial out

A plugin connects to the platform, not the other way round. No inbound port, no public IP, no firewall hole. A plugin running on a NAS in your basement is callable from the platform just like one running in the cloud — which is also why something inherently local, like a coding agent on your own laptop, can be a plugin at all.

Which SDK

Language	Install	Declare the contract in	Getting started
Go	go get github.com/sokel-dev/sokel-plugin-sdk	a schema/ package (Go builders)	below
Python	pip install sokel-plugin-sdk	manifest.yml	sdk-python/README.md
TypeScript	npm install @sokel-dev/plugin-sdk	manifest.yml	sdk-node/README.md

All three speak the same JSON-over-NATS wire protocol and report the same contract JSON; a reference plugin (examples/kitchen-sink) is implemented twice and asserted against one golden file, so the SDKs cannot drift apart in how they read the protocol.

Install

The library:

go get github.com/sokel-dev/sokel-plugin-sdk

The sokel-gen CLI — scaffolds plugins and generates the typed code from your declarations:

go install github.com/sokel-dev/sokel-plugin-sdk/cmd/sokel-gen@latest

Requires Go 1.23 or newer. You can skip the install and use go run github.com/sokel-dev/sokel-plugin-sdk/cmd/sokel-gen instead — that is the form used in //go:generate lines, so the version is pinned by your go.mod rather than by whatever you last installed.

How it works

Four steps, always in this order: declare → generate → implement → connect.

Start from a working skeleton rather than an empty directory:

sokel-gen init ./my-plugin
cd my-plugin && go mod tidy && sokel-gen && go build ./...

That scaffolds schema/, main.go, an embedded user-facing doc and both README files, with one real operation already wired end to end. The rest of this section is what init gave you — change it into your own plugin.

1. Declare the contract in a schema/ package — inputs, outputs, events, credential fields:

package schema

import (
	"github.com/sokel-dev/sokel-plugin-sdk/contract"
	"github.com/sokel-dev/sokel-plugin-sdk/contract/field"
)

type IssuesList struct{}

func (IssuesList) Meta() contract.Meta {
	return contract.Meta{ID: "issues_list", Label: "List issues"}
}

func (IssuesList) Inputs() []contract.FieldSpec {
	return []contract.FieldSpec{
		field.String("project").Label("Project"),
		field.Enum("state",
			field.Opt("opened", "Open"),
			field.Opt("closed", "Closed")).Default("opened"),
	}
}

func (IssuesList) Outputs() []contract.FieldSpec {
	return []contract.FieldSpec{
		field.Array("issues", []Issue{}).Label("Issues"),
		field.Int("count").Label("Count"),
	}
}

2. Generate the typed Go from that declaration:

//go:generate go run github.com/sokel-dev/sokel-plugin-sdk/cmd/sokel-gen

go generate ./...

This writes zz_types.go (the In/Out structs) and zz_register.go (an OnXxx function per operation). Don't hand-edit them.

The contract is produced at compile time, not by runtime reflection. A mistake in the declaration fails the build instead of surfacing on some later call. sokel-gen check verifies the generated files are current — wire it into CI, because forgetting to regenerate is the classic way codegen goes wrong.

3. Implement the handlers — the signatures are fully concrete, so the compiler checks your work.

4. Connect back to the platform:

p := sokel.New(sokel.Config{
	Endpoint: sokel.Env("ENDPOINT"),
	Token:    sokel.Env("TOKEN"),
	Name:     "my-plugin",
})
OnIssuesList(p, handleIssuesList)
log.Fatal(p.Run())

Configuration

The SDK reads everything from SOKEL_-prefixed environment variables:

Variable	Required	Meaning
SOKEL_ENDPOINT	yes	nats://broker:4222, or an https:// platform URL to discover the broker from
SOKEL_TOKEN	yes	Access-group token (skp_…) identifying plugin + workspace
SOKEL_NATS_TOKEN	no	Broker-level auth, if the broker requires it
SOKEL_NATS_CA	no	Custom CA bundle for tls:// brokers
SOKEL_INSTANCE_ID	no	Pin a replica identity across restarts
SOKEL_REGION	no	Region label for the replica

Credentials are never stored by the plugin. The platform injects the resolved fields with each call; read them typed with sokel.CredentialAs[T].

Packages

Package	What it is
sokel	The runtime: register, dispatch, emit results, files, events, webhooks
contract	The contract types — field specs, metadata, credential and event shapes
contract/field	Builders for declaring fields (field.String, field.Enum, …)
sokelgen	The code generator behind sokel-gen
cmd/sokel-gen	The CLI — see below
pluginenv	Reads the SOKEL_ environment variables

The sokel-gen CLI

Command	What it does
sokel-gen	Generate for the current directory — the form used in //go:generate
sokel-gen init <dir>	Scaffold a new plugin that builds and runs as-is (-lang go｜python｜ts)
sokel-gen generate [dir...]	Generate; a directory holding many plugins is walked automatically
sokel-gen check [dir...]	Verify the generated files are current, write nothing — for CI
sokel-gen export <json|yaml|ts|python> [dir]	Print the contract in another form
sokel-gen migrate [dir]	Turn an old struct+tag plugin into a schema/ declaration
sokel-gen docs [topic]	Print the manifest.yml format guide / JSON Schema / reference declaration
sokel-gen example [lang]	Print the reference plugin: declaration, Python impl, TypeScript impl

generate and check take -schema <name> when the declaration package isn't called schema.

Plugins are found by looking for a schema/ directory or a manifest.yml, not by reading //go:generate lines. That distinction matters: go generate ./... silently skips a plugin whose directive someone forgot to write, and a skipped plugin's contract drifts with nothing going red. Four first-party plugins were in exactly that state before this was checked.

sokel-gen check ./plugins        # every plugin under ./plugins, one command

Docs in the binary

The format guide, the JSON Schema and a reference declaration covering every contract shape are embedded in the sokel-gen binary — no checkout, no network:

sokel-gen docs        # how to write manifest.yml
sokel-gen example     # a real declaration using every shape; copy and edit

That is mostly for agents: pointing an LLM at four commands (docs → example → init -lang python|ts → generate) is enough for it to write a working plugin, and generate reports every problem in the declaration at once.

check runs every plugin before reporting, so CI shows you all the stale ones at once instead of one per run.

Examples

Example	What it shows
examples/sysinfo	A complete Go plugin: two operations, a file input, an embedded user-facing doc
examples/kitchen-sink	Every contract shape at once — declared once, implemented in Python and TypeScript, both asserted against one golden contract

cd examples/sysinfo
SOKEL_ENDPOINT=nats://localhost:4222 SOKEL_TOKEN=skp_xxx go run .

One declaration, many targets

A contract can be declared from either entry point, and both produce the same intermediate representation:

schema/ package (Go builders) ──┐
                                ├──▶ IR ──┬──▶ typed Go     zz_types.go / zz_register.go
manifest.yml (language-neutral) ──┘         ├──▶ typed Python sokel_gen.py (pydantic models)
                                          ├──▶ typed TS     sokel.gen.ts (interfaces)
                                          ├──▶ export json  the contract itself
                                          └──▶ export yaml  a manifest.yml, from a Go declaration

Go plugins use the schema/ package: the contract is executable Go, a misspelled method is a compile error, and existing Go types can be reused directly. Python and TypeScript plugins use manifest.yml — declaring a few fields should not start with "learn a Go builder API".

sokel-gen init -lang python ./my-plugin   # or -lang ts
sokel-gen generate ./my-plugin            # manifest.yml → typed models + registration
sokel-gen export yaml ./plugins/gitlab    # the reverse: Go declaration → manifest.yml

The format is documented in docs/manifest.md. YAML and JSON are the same format (parsed through one path), and unknown keys are an error rather than a silently dropped field.

The exported JSON deliberately omits Go type names — it carries the contract, not the Go implementation detail. This matters because the wire protocol is JSON over NATS with base64 bytes: no gob, no protobuf, nothing Go-specific. This SDK is one implementation of that protocol, not the definition of it. A Rust SDK is the remaining target, and adding one is a renderer over the existing IR plus a runtime, not a second parser.

Releasing

One tag ships all three SDKs at the same version — Go from the tag itself, Python and TypeScript through .github/workflows/release.yml. The procedure and the one-time registry setup are in RELEASING.md.

# bump sdk-node/package.json + sdk-python/pyproject.toml, then
git tag v0.3.0 && git push origin main --tags

Every gate in that pipeline exists because of a failure that only shows up after publishing: version drift between the tag and the packages, stale generated files, a package whose build step was skipped and therefore ships empty.

Status

The Sokel platform itself is not open source yet. Until it is, this SDK is useful for reading the plugin model and preparing a plugin — but a plugin needs a running Sokel instance to dial into.

License

Apache-2.0. See LICENSE.