/CHANGELOG.md

Changelog

All notable changes to Go Micro are documented here.

Format follows Keep a Changelog. Go Micro uses calendar-based versions (YYYY.MM) for the AI-native era.

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[Unreleased]

Added

• A2A protocol — both directions — gateway/a2a exposes registered agents over the open Agent2Agent (A2A) protocol so agents on other frameworks can discover and call them: Agent Cards are generated from registry metadata (the same way the MCP gateway derives tools), and incoming tasks are translated to the agent's existing Agent.Chat RPC, with no per-agent code (micro a2a serve). The outbound a2a.Client calls external A2A agents by URL, wired into flow.A2A(url) (a workflow step) and delegate to an http(s) URL (from inside an agent). v1 is the synchronous JSON-RPC binding (message/send, tasks/get, card discovery); streaming and push notifications are advertised as unsupported. (gateway/a2a/, cmd/micro/a2a/)
• Agents (micro.NewAgent) — an agent is a service with an LLM inside: it discovers its assigned services as tools, runs the model's tool loop, registers a Chat RPC endpoint, and is reachable like any service. Ask for programmatic use; micro chat discovers and routes to agents; micro agent list/describe. (agent/)
• Plan & delegate — two built-in agent tools added to every agent: plan (an ordered, store-persisted plan surfaced back in the prompt) and delegate (hand a self-contained subtask to a registered agent over RPC, otherwise to an ephemeral sub-agent). No harness or graph — they're plain tools. (agent/builtin.go, examples/agent-plan-delegate/)
• Agent guardrails — MaxSteps (stop on count), LoopLimit (stop repeated no-progress calls; on by default), and ApproveTool (human-in-the-loop / policy gate before each action), enforced at the one point every tool call passes through. (agent/, guide + blog)
• Pluggable agent memory & custom tools — durable store-backed conversation memory by default, swappable via AgentMemory; register any function as a tool with AgentTool.
• Workflows (micro.NewFlow) — event-driven orchestration that maps to Anthropic's workflow/agent split: an event triggers a deterministic step (or ordered durable steps), or dispatches to an agent with FlowAgent. (flow/)
• x402 payments — opt-in per-call payments for tools via the x402 standard, with a pluggable facilitator and a consumer-side client + budget; the MCP gateway can advertise and require payment per tool. (wrapper/x402/, guide + blog)
• Scoped store state — store.Scope(s, database, table) returns a store handle that confines every operation to a database/table without mutating the shared store (unlike Init(Table(...)), which is process-global and races between co-located components). Services, agents, and flows now each keep their state in their own table (service/{name}, agent/{name}, flow/{name}); the service path replaces the old Init(store.Table(name)) global mutation with a scoped handle.
• Flow discovery & history CLI — running flows now register in the registry as type=flow (and deregister on Stop), so they're discoverable like agents: micro flow list shows running flows, micro flow runs <name> shows a flow's durable run history from the store, and micro agent history <name> shows an agent's stored conversation. Live state comes from the registry; durable history from the scoped store.
• Durable workflows — a flow can now be an ordered list of steps (a task with stages) that is checkpointed before and after each step, so a run survives a crash and resumes where it stopped without re-running completed steps. State carries a typed payload plus a Stage marker; flow-level Retry with a per-step override; runs retained for audit unless DeleteOnSuccess. Step actions: Call (RPC), LLM (model turn), Dispatch (to an agent), or any StepFunc. Durability is a pluggable Checkpoint (store-backed by default; implement the interface for Temporal/Restate). Runnable example: examples/flow-durable/. Blog: "Durable Workflows" (internal/website/blog/24.md).
• Agent tool-execution wrappers — AgentWrapTool registers middleware around an agent's tool calls, the tool-side analogue of client.CallWrapper/server.HandlerWrapper. Use it for logging, metrics, retries, or policy; wrappers compose outermost-first and run outside the built-in guardrails. Includes a runnable example with observe + retry wrappers (examples/agent-wrap-tool/).
• Agent platform showcase — full platform example (Users, Posts, Comments, Mail) mirroring micro/blog, demonstrating how existing microservices become agent-accessible with zero code changes (examples/mcp/platform/).
• Blog post: "Your Microservices Are Already an AI Platform" — walkthrough of agent-service interaction patterns using real-world services (internal/website/blog/7.md).
• Circuit breakers for MCP gateway — per-tool circuit breakers protect downstream services from cascading failures. Configurable max failures, open-state timeout, and half-open probing. Available via Options.CircuitBreaker and --circuit-breaker CLI flag (gateway/mcp/circuitbreaker.go).
• Helm chart for MCP gateway — official Helm chart at deploy/helm/mcp-gateway/ with Deployment, Service, ServiceAccount, HPA, and Ingress templates. Supports Consul/etcd/mDNS registries, JWT auth, rate limiting, audit logging, per-tool scopes, TLS ingress, and auto-scaling.
• MCP gateway benchmarks — comprehensive benchmark suite for tool listing, lookup, auth, rate limiting, and JSON serialization (gateway/mcp/benchmark_test.go)
• Workflow example — cross-service orchestration demo with Inventory, Orders, and Notifications services showing agents chaining multi-step workflows from natural language (examples/mcp/workflow/)
• Docker Compose deployment — production-like setup with Consul registry, standalone MCP gateway, and Jaeger tracing in one docker-compose up (examples/deployment/)

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[2026.03] - March 2026

Added

Developer Experience

• micro new MCP templates — micro new myservice generates MCP-enabled services with doc comments, @example tags, and WithMCP() wired in. Use --no-mcp to opt out.
• micro.New("name") unified API — single way to create services: micro.New("greeter") or micro.New("greeter", micro.Address(":8080")). Replaces micro.NewService() + service.New() dual API.
• service.Handle() simplified registration — register handlers with service.Handle(new(Greeter)) instead of manual server.NewHandler + server.Handle.
• micro.NewGroup() modular monoliths — run multiple services in one binary with shared lifecycle: micro.NewGroup(users, orders).Run().
• mcp.WithMCP() one-liner — add MCP to any service with a single option: micro.New("name", mcp.WithMCP(":3001")).
• CRUD example — contact book service with 6 operations, rich agent docs, and validation patterns (examples/mcp/crud/).

MCP Gateway

• WebSocket transport — bidirectional JSON-RPC 2.0 streaming over WebSocket for real-time agent communication (gateway/mcp/websocket.go).
• OpenTelemetry integration — full span instrumentation across HTTP, stdio, and WebSocket transports with W3C trace context propagation (gateway/mcp/otel.go).
• Standalone gateway binary — micro-mcp-gateway with Docker support for running the MCP gateway independently of services.
• Per-tool auth scopes — service-level (server.WithEndpointScopes()) and gateway-level (Options.Scopes) scope enforcement with bearer token auth.
• Rate limiting — per-tool token bucket rate limiting (Options.RateLimit).
• Audit logging — immutable audit records per tool call with trace ID, account, scopes, duration, and errors (Options.AuditFunc).

AI Model Package

• model.Model interface — unified AI provider abstraction with Generate() and Stream() methods.
• Anthropic Claude provider — model/anthropic with tool execution and auto-calling.
• OpenAI GPT provider — model/openai with provider auto-detection from base URL.

Agent SDKs

• LangChain SDK — contrib/langchain-go-micro/ Python package with auto-discovery, tool generation, and multi-agent workflow examples.
• LlamaIndex SDK — contrib/go-micro-llamaindex/ Python package with RAG integration examples.

Documentation

• AI-native services guide — building services for AI agents from scratch
• MCP security guide — auth, scopes, and audit logging
• Tool descriptions guide — writing doc comments that improve agent performance
• Agent patterns guide — architecture patterns for agent integration
• Error handling guide — writing agent-friendly error responses with typed errors
• Troubleshooting guide — common MCP issues and solutions
• Migration guide — add MCP to existing services in 5 minutes

CLI

• micro mcp serve — start MCP server (stdio for Claude Code, HTTP for web agents)
• micro mcp list — list available tools (human-readable or JSON)
• micro mcp test — test tools with JSON input
• micro mcp docs — generate tool documentation
• micro mcp export — export to LangChain, OpenAPI, or JSON formats

Agent Playground

• Chat-focused UI — redesigned playground with collapsible tool calls, real-time status, and thinking indicators
• Provider settings — configurable OpenAI/Anthropic provider, model, and API key

Changed

• Service interface moved to service.Service with micro.Service as a type alias for backward compatibility.
• service.New() returns service.Service interface (was *ServiceImpl).
• service.NewGroup() accepts service.Service interface (was *ServiceImpl).
• go.mod template in micro new updated to Go 1.22.

Fixed

• Handler Handle() method accepts variadic server.HandlerOption for scopes and metadata.
• Store initialization uses service name as table automatically.
• Service Stop() properly aggregates errors from lifecycle hooks.

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[2026.02] - February 2026

Added

• MCP gateway library — gateway/mcp/ with HTTP/SSE and stdio transports, service discovery, tool generation, and JSON schema generation from Go types (2,500+ lines).
• CLI integration — micro run --mcp-address flag to start MCP alongside services.
• Documentation extraction — auto-extract tool descriptions from Go doc comments with @example tag and struct tag parsing.
• Blog post — "Making Microservices AI-Native with MCP"
• MCP examples — examples/mcp/hello/ and examples/mcp/documented/

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[2026.01] - January 2026

Added

• micro deploy — deploy services to any Linux server via SSH + systemd with micro deploy user@server.
• micro build — build Go binaries and Docker images with micro build --docker.
• Blog post — "Introducing micro deploy"

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For earlier changes, see the git log.