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tai/research/cap-protocol/cap-rs-a2a-driver.md
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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

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1.5 KiB
Markdown

# CAP reference A2A driver (cap-rs a2a.rs)
## Metadata
| Field | Value |
|---|---|
| Institute | Molodetz Institute — Research & Retrieval Division |
| Subject | cap-protocol |
| Document type | Source Citation Card |
| Tier | 2 |
| Source title | crates/cap-rs/src/driver/a2a.rs |
| Source URL | https://github.com/rsclaw-ai/cap-protocol/blob/main/crates/cap-rs/src/driver/a2a.rs |
| Source type | reference implementation |
| Date researched | 2026-10-18 |
| Researched by | tai (agent), model: Muse Spark, on behalf of retoor |
| Research method | direct raw-file fetch, grepped for endpoint strings, request bodies, and the event-mapping core (not read in full) |
| Confidence | High |
| Status | Active |
## Why it's here
Grepped to settle which A2A spelling the reference driver actually uses: `POST {endpoint}/message/send` with `{message: {role, parts: [{kind: text, text}]}}` and `POST {endpoint}/tasks/cancel` with no body (draft-style), card at `/.well-known/agent-card.json` refused without the `cap-protocol/v1` extension. The event mapper accepts raw `cap.*` JSON, data parts unwrapped via `_meta.cap.kind` (from message, task-status and artifact parts alike), text parts (kind or type `text`, id from messageId/message_id), and failed task states; outbound answers travel as data parts with the `_meta.cap.kind` marker. Control flow around the mapper was not reviewed.
## Changelog
| Date | Change |
|---|---|
| 2026-10-18 | Logged as consulted-but-not-analyzed. |