Realtime Agent A2A Profile Extension

This repository defines an optional A2A profile for real-time, steerable voice and multimodal conversations. It standardizes the boundary between a media-facing Live layer and a reasoning/workflow Reasoner: transcripts go in; streamed spoken output and structured conversation directives come out.

The profile is additive to core A2A. A compatible client and server negotiate it through the Agent Card and the A2A-Extensions header; peers that do not implement it continue to interoperate through ordinary A2A messages, artifacts, and task states.

Specification

spec.md is the normative v0.1 draft. It defines:

• the extension URI and Agent Card advertisement;
• extension activation and client/server directive capability negotiation;
• mapping of calls to contextId and utterances to A2A tasks;
• streamed text artifacts, control directives, handoffs, interruption, and history backfill; and
• core-A2A fallback behavior.

The v0.1 profile is text-in/text-and-directives-out. ASR, TTS, media transport, and call control remain the Live layer's responsibility.

Supporting artifacts

spec.md is the contract; these artifacts make it machine-checkable, implementable, and governed. Status against the original v0.1 gap list:

Artifact	Status	Location
JSON Schemas	✅ draft	schemas/v0.1/ — versioned, one per payload
Reference fixtures	✅ draft	fixtures/ — valid/invalid + event sequences
Conformance suite	✅ draft	conformance/ — pytest, schema + behavioral
Reference implementation(s)	✅ illustrative	examples/ — Python Live client + Reasoner server
Compatibility matrix	✅ draft	docs/compatibility.md
Security profile	✅ draft	docs/security.md
Error and retry policy	✅ draft	docs/errors.md
Escalation design	✅ draft	docs/escalation.md
Operational profile	✅ draft	docs/operations.md
Governance	✅	GOVERNANCE.md, CHANGELOG.md, LICENSE

Repository layout

spec.md                         # normative profile specification (source of truth)
schemas/v0.1/                   # versioned JSON Schema documents (2020-12)
fixtures/                       # valid/ and invalid/ payloads + sequences/ event flows
conformance/                    # pytest suite enforcing the normative requirements
examples/                       # reference Live client + Reasoner server (Python)
docs/                           # compatibility, security, errors, escalation, operations
GOVERNANCE.md  CHANGELOG.md  CONTRIBUTING.md  DEVELOPING.md  LICENSE

Current open design items

The v0.1 draft still intentionally leaves the following for later versions; they are tracked through GOVERNANCE.md and sketched (non-normatively) in docs/:

• Media-carrying A2A — audio/video bytes across this boundary (spec §11).
• Graceful connection drain, reconnect, and replay — future draining/endOfConnection events and tasks/resubscribe recovery (spec §11; sketch in docs/operations.md).
• Portable escalation routing / transfer-result contract — a neutral design is proposed in docs/escalation.md but is not yet normative in spec.md.
• Pinned A2A SDK names/versions for a production interoperability commitment (see docs/compatibility.md).

The reference implementations under examples/ are illustrative teaching aids, not production code.