The A2A gateway's push-notification flow (tasks/pushNotificationConfig/set
→ deliverPush) POSTed task state to a caller-supplied URL via the default
HTTP client, so an untrusted A2A caller could aim the gateway at internal
addresses (loopback, link-local cloud metadata, RFC1918) it would
otherwise never reach — a server-side request forgery vector (#4129).
Add a default SSRF-safe policy: only http/https callbacks whose host does
not resolve to a loopback, private, link-local, multicast, or unspecified
address. It's enforced when the config is set (caller gets a clear
rejection, nothing stored) and again at delivery, and the delivery client
re-checks the resolved IP at dial time so a name that passes validation
can't be rebound to an internal address before connect.
Operators that need a trusted in-cluster receiver set Options.AllowPushURL
(gateway) or a2a.WithPushURLPolicy (embedded handlers) to own the policy;
that path skips the built-in private-IP dial guard by design.
Tests cover blocked/allowed URLs, the dial-time guard, set-time rejection,
default-deny delivery, and the operator override.
Claude-Session: https://claude.ai/code/session_01CmdEY7pYmV5zzwCjNJ4ykL
Co-authored-by: Claude <noreply@anthropic.com>
Refactor the A2A handler into a reusable dispatcher + Invoke seam and
expose NewAgentHandler(card, invoke) + Card(). An agent now serves its
own A2A endpoint with AgentA2A(addr) / WithA2A — handling tasks
in-process (no RPC hop, no separate gateway). The gateway and embedded
agent share the same handler; the only difference is RPC vs in-process
invocation. Docs, README, and changelog cover both deployment modes.
Co-authored-by: Claude <noreply@anthropic.com>
* feat(a2a): Agent2Agent protocol gateway
Add gateway/a2a — exposes registered agents over the open 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 from service endpoints); incoming A2A tasks translate to the
agent's existing Agent.Chat RPC, so there's no per-agent code.
v1 is the synchronous JSON-RPC binding: message/send returns a completed
Task, tasks/get retrieves it, and Agent Cards are served for discovery;
streaming and push notifications are advertised as unsupported. Run with
'micro a2a serve' (cmd/micro/a2a). Tests cover card generation,
message/send, tasks/get, listing, and unknown-method errors.
* docs: A2A guide, README contents + A2A section, universe A2A check
- Add a Contents table of contents at the top of the README and an A2A
subsection under Building Agents.
- Add the Agent2Agent (A2A) guide and register it in the docs nav.
- Exercise the A2A gateway in the universe harness: the concierge agent
is reached over A2A (message/send -> Agent.Chat -> completed task).
* feat(a2a): outbound client — call external A2A agents
Add a2a.Client (Send/Card) so a Go Micro agent or flow can call an agent
on any framework by URL — the outbound counterpart to the gateway. Wired
in two places: flow.A2A(url) as a workflow step (the cross-framework
Dispatch), and agent delegate to an http(s) URL routes over A2A. The
universe harness now drives the gateway through the client, exercising
both directions. Tests cover client send/card and the round trip.
* docs: A2A both-directions — guide, README, changelog, blog #26
---------
Co-authored-by: Claude <noreply@anthropic.com>
Asim Aslam