Protocol intelligence / Agent coordination

Agent2Agent Protocol

A standard for communication and task coordination between agents.

Specification state: livePrimary evidence available

StewardA2A project / Linux Foundation community

Stack layerAgent coordination

Version1.0.1 repository release / 1.0.0 specification banner — scope unresolved

Last evidence check28 September 2026

Merchant answer / Evidence review pending

A standard for communication and task coordination between agents. Defines agent capabilities, messages, tasks and cooperation. Does not itself supply a merchant catalog, checkout or payment settlement. Individual merchant eligibility and deployed configuration require confirmation. Map this role to your existing stack and confirm the exact version, access conditions and implementation scope before making a merchant decision.

What this establishes
The documented role and version scope in the source ledger.

What it cannot establish
An unresolved dependency remains. Treat affected claims as provisional. Live merchant deployment, private account eligibility, purchase completion or guaranteed AI selection.

Claim-to-source mapping

description: A standard for communication and task coordination between agents. · verified · Checked 2026-09-28 · Sources: a2a-spec
Scope: Public documentation; not an authenticated merchant test
role: Defines agent capabilities, messages, tasks and cooperation. · verified · Checked 2026-09-28 · Sources: a2a-spec
Scope: Public documentation; not an authenticated merchant test
version: 1.0.0 · verified · Checked 2026-09-28 · Sources: a2a-spec
Scope: Public documentation; not an authenticated merchant test
version: 1.0.1 repository release / 1.0.0 specification banner — scope unresolved · conflict · Checked 2026-09-28 · Sources: v11-a2a-releases, v11-a2a-spec
Scope: Official repository release

Evidence dates and document versions remain attached to the ledger below. Editorial presentation reviewed 30 September 2026; this is not a new source verification.

Version-aware protocol intelligence

Current version. Clear scope.

Current version1.0.1

Current statusreleased; source scope conflict

Published date2026-05-28

First observed / last verified2026-09-28 / 2026-09-28

GitHub release published_at; distinct from the date encoded in a version tag.

Scope: Official repository release · Layer: Agent coordination · Steward: A2A project / Linux Foundation community

Merchant impact

Repository patch includes HTTP media-type, transcoding and task-status corrections. The latest spec page still identifies 1.0.0.

Confirm the exact protocol schema and SDK alignment; agent coordination does not prove merchant adoption.

Unresolved source difference: repository v1.0.1; latest specification banner 1.0.0. These are retained separately, without silently choosing one scope for every implementation.

Public implementation evidence: Released spec; merchant integrations Unknown

Merchant action today: Publish accurate capabilities for your agent.

Unknowns: Your enabled version, provider rollout, plan and region require merchant-side confirmation.

A2A maintainers version source ↗A2A maintainers version source ↗

Source capture hashes

v11-a2a-releases: SHA-256 2e1ba7bba863623bca20520c60644cb11dc020783b0d0a5eb89e0cc4aea474e3

v11-a2a-spec: SHA-256 4805254c10d8cbde59a82f6767598c37b051d7c3cdf9d5ce636dba287cd6ab2b

Previous versions

Retrospective source research, first observed by us in September 2026. This is a reviewed subset, not a claim of complete upstream release history.

1.0.0 historical release

Published 2026-03-12 · First observed 2026-09-28

1.0 protocol release includes breaking interface and naming changes.

Merchant impact: Confirm the exact protocol schema and SDK alignment; agent coordination does not prove merchant adoption.

GitHub release published_at; distinct from the date encoded in a version tag.

Version source ↗

0.3.0 historical release

Published 2025-07-30 · First observed 2026-09-28

0.3 release includes agent-card discovery and security changes.

Merchant impact: Confirm the exact protocol schema and SDK alignment; agent coordination does not prove merchant adoption.

GitHub release published_at; distinct from the date encoded in a version tag.

Version source ↗

Documented role

What it helps with

Defines agent capabilities, messages, tasks and cooperation.

Keep the scope clear

What it does not solve

Does not itself supply a merchant catalog, checkout or payment settlement.

The merchant work

Publish accurate capabilities for your agent.
Define task lifecycle and failure handoff.
Separate coordination permissions from purchase authority.

Individual merchant eligibility and deployed configuration require confirmation.

Version	1.0.1 repository release / 1.0.0 specification banner — scope unresolved conflict · 2026-09-28
Discovery	Agent cards and capabilities verified · 2026-09-28
Checkout	Application-level responsibility verified · 2026-09-28
Payment	Application-level responsibility verified · 2026-09-28
Authorization	Security schemes, not blanket purchase authorization verified · 2026-09-28
Transport	JSON-RPC, HTTP+JSON and gRPC bindings verified · 2026-09-28
Adoption	Released spec; merchant integrations Unknown verified · 2026-09-28

Compare protocols ↗

Append-only history

What we observed, and when.

First house observation: 28 September 2026. Earlier dates, where known, are effective dates researched retrospectively.

2026-05-28T11:34:36Z

Effective date

Conflict discovered

1.0.1 repository release / 1.0.0 specification banner — scope unresolved; 3 scoped version record(s) now linked.

Before / previous scope

V1 record: 1.0.0; no structured prior-version timeline.

Observed evidence

1.0.1 repository release / 1.0.0 specification banner — scope unresolved; 3 scoped version record(s) now linked.

Merchant impact: Confirm the exact protocol schema and SDK alignment; agent coordination does not prove merchant adoption.

First captured by us: 2026-09-28. Earlier effective dates are researched retrospectively.

A2A maintainers source ↗A2A maintainers source ↗View entity →

Open the September baseline →

Evidence ledger

Go to the source.

Primary documentation records what is publicly stated. It does not independently prove outcomes or your account’s eligibility.

Agent2Agent specification
A2A project · official primary · Checked 2026-09-28
Claim scope: Agent coordination
Latest released version shown as 1.0.0. Agent card app version is a different field.
Source ID: a2a-spec · Published: Not stated
A2A Releases — V1.1 source capture
A2A maintainers · official primary · Checked 2026-09-28
Claim scope: Version metadata and documented changes only; not merchant adoption.
SHA-256 of retrieved source response: 2e1ba7bba863623bca20520c60644cb11dc020783b0d0a5eb89e0cc4aea474e3
Source ID: v11-a2a-releases · Published: Not stated
A2A Spec — V1.1 source capture
A2A maintainers · official primary · Checked 2026-09-28
Claim scope: Version metadata and documented changes only; not merchant adoption.
SHA-256 of retrieved source response: 4805254c10d8cbde59a82f6767598c37b051d7c3cdf9d5ce636dba287cd6ab2b
Source ID: v11-a2a-spec · Published: Not stated

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