Files

T

retoor cc1c130b51 CAP protocol both directions: agent speak plus orchestrator drivers (1.39.0)

- Agent side: --cap-manifest plus --cap-speak stream-json binding with
  transcript-diff frames, diff/transcript artifacts, session config
- Orchestrator: PTY driver (settle heuristics on PtyProc/TuiVtScreen),
  stream-json, ACP-stdio (permission/elicit/fs/terminal serving) and
  A2A drivers (dual draft/current spelling, SSE mapping)
- Sessions, fleets: worktrees, master plans, mediated routing,
  budget refusal, audit log, research auto-answerer, --cap CLI
- cap.md contract with drift tests; research/cap-protocol archive
- Suites 1119 + 16 green

2026-10-18 13:17:35 +02:00

2.8 KiB

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A2A protocol specification (current)

Metadata

Field	Value
Institute	Molodetz Institute — Research & Retrieval Division
Subject	cap-protocol
Document type	Source Dossier
Tier	1
Source title	Agent2Agent (A2A) Protocol Specification
Source URL	https://github.com/a2aproject/A2A/blob/main/docs/specification.md
Source type	specification
Source date (published)	Unknown, not stated (living LF doc)
Date researched	2026-10-18
Researched by	tai (agent), model: Muse Spark, on behalf of retoor
Research method	direct raw-file fetch, read selectively: full outline, §3.1 ops, §5.3 method mapping, §5.4 errors, discovery sections via grep
Confidence	High
Status	Active

Summary

Current A2A: JSON-RPC PascalCase methods (SendMessage, SendStreamingMessage, CancelTask...) or colon-REST equivalents (POST /message:send), AgentCard at /.well-known/agent-card.json, cursor-paginated task listing, extension declarations with required flags. Critically, its method names do NOT match what CAP v1 cites (message/send, tasks/cancel).

Key findings

Method mapping (§5.3): JSON-RPC SendMessage / REST POST /message:send; streaming SendStreamingMessage / POST /message:stream; cancel CancelTask / POST /tasks/{id}:cancel. CAP's slash-forms match the pre-1.0 A2A draft, not current A2A.
Stream patterns: message-only (exactly one Message then close) or task-lifecycle (Task first, then status/artifact updates, close at terminal state).
Terminal states: completed/failed/canceled/rejected; interrupted: input-required (6), auth-required (8).
AgentCard discovery via well-known URI; extensions carry uri/description/required/params, matching CAP's cap-protocol/v1 extension check.
A2A error codes (-32001..-32009) collide numerically with CAP's registry but with different meanings; bindings must not mix the two registries.

Pros / strengths

Normative LF spec with explicit binding-equivalence rules, giving tai a stable target for the A2A driver and expose-server.
The extension mechanism is exactly what CAP's compatibility check needs.

Cons / limitations / caveats

Markdown tables are template-generated (proto_to_table), so the .md alone omits field shapes; the .proto file is the real schema.
Large surface (push notifications, OAuth flows, mTLS) far beyond what CAP's binding needs; tai implements the message/stream/cancel/card subset only.
Read selectively (operations, mappings, discovery); auth and push sections not read.

Relevance to tai

Forces the dual-spelling decision in the naming-drift conclusion: tai's A2A driver must speak CAP-literal draft endpoints to CAP peers and current endpoints to real A2A agents.

Changelog

Date	Change
2026-10-18	Initial dossier created.

2.8 KiB Raw Blame History