Tier-2 polyglot SDK for AgentBreeder — runtime contract scaffolding + registry client in Go.

Go SDK

Build deployable AgentBreeder agents in Go. The Go SDK is a Tier-2 polyglot SDK: thin and contract-first. It implements Runtime Contract v1 so the same observability, governance, and routing the Python/TypeScript runtimes get applies to Go agents automatically.

Tier‑2 polyglot status

Go is the first polyglot SDK to ship under Track I (#165). Kotlin, Rust, and .NET are tracked as follow-up issues.

Install

go get github.com/agentbreeder/agentbreeder/sdk/go/agentbreeder

Requires Go 1.22+.

Hello world

package main

import (
    "context"
    "log"

    "github.com/agentbreeder/agentbreeder/sdk/go/agentbreeder"
)

func main() {
    invoke := func(ctx context.Context, req agentbreeder.InvokeRequest, resp *agentbreeder.InvokeResponse) error {
        prompt, _ := req.Input.AsString()
        return resp.SetOutput("you said: " + prompt)
    }

    srv := agentbreeder.NewServer(invoke,
        agentbreeder.WithName("my-agent"),
        agentbreeder.WithVersion("0.1.0"),
    )
    if err := srv.ListenAndServe(context.Background(), ":8080"); err != nil {
        log.Fatal(err)
    }
}

NewServer returns an http.Handler that auto-wires:

Endpoint	Purpose
`GET /health`	Liveness/readiness — open
`GET /openapi.json`	Self-describing schema — open
`GET /.well-known/agent.json`	A2A agent card — open
`POST /invoke`	Synchronous run — bearer-auth
`POST /stream`	SSE streaming run — bearer-auth
`POST /resume`	HITL resume (opt-in) — bearer-auth

Bearer-token auth comes from the AGENT_AUTH_TOKEN env var. Disabled when unset (local dev).

Scaffold a project

agentbreeder init --lang go --framework custom my-agent
cd my-agent
go mod tidy
go run .

The scaffolder writes main.go, main_test.go, go.mod, agent.yaml, Dockerfile, .gitignore, .env.example, and README.md.

Streaming (SSE)

stream := func(ctx context.Context, req agentbreeder.InvokeRequest, out chan<- agentbreeder.StreamEvent) error {
    out <- agentbreeder.StreamEvent{Data: agentbreeder.SseTextDelta{Delta: "hello "}}
    out <- agentbreeder.StreamEvent{Data: agentbreeder.SseTextDelta{Delta: "world"}}
    return nil
}

srv := agentbreeder.NewServer(invoke, agentbreeder.WithStream(stream))

The SDK frames each event as either data: {…} (when Name is empty) or event: <name>\ndata: {…}\n\n, and always emits the mandatory data: [DONE] terminator.

Registry client

The Client talks to the central AgentBreeder API:

c := agentbreeder.NewClient("https://api.agentbreeder.io", os.Getenv("AGENTBREEDER_API_KEY"))
agents, err := c.ListAgents(ctx)
_, err = c.RegisterAgent(ctx, agentbreeder.AgentRegistration{
    Name: "my-agent", Version: "0.1.0", Team: "eng", Owner: "a@b.c",
    Language: "go", Framework: "custom",
})
secrets, err := c.ListSecrets(ctx)

The client is intentionally narrow: agents, models, secrets. Wider coverage stays with the Python SDK.

Deploying

The Go runtime builder (engine/runtimes/go/) packages your agent with a multi-stage Dockerfile (golang:1.22-alpine builder → gcr.io/distroless/static final, < 20 MB). Reference your project from agent.yaml with the runtime block:

name: my-agent
version: 0.1.0
team: engineering
owner: alice@company.com

runtime:
  language: go
  framework: custom
  version: "1.22"

model:
  primary: claude-sonnet-4-20250514

deploy:
  cloud: aws

Then run agentbreeder deploy agent.yaml --target aws — the deploy pipeline is identical to Python and Node agents.

Regenerating types

The hand-curated types in types.go are kept in lock-step with engine/schema/runtime-contract-v1.openapi.yaml. To regenerate the raw oapi-codegen package:

go run github.com/oapi-codegen/oapi-codegen/v2/cmd/oapi-codegen@v2.4.1 \
    -generate types,client,server \
    -package gen \
    -o gen/runtime_contract.gen.go \
    ../../../engine/schema/runtime-contract-v1.openapi.yaml

Go SDK

Go SDK

Install

Hello world

Scaffold a project

Streaming (SSE)

Registry client

Deploying

Regenerating types

See also

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