# ACP initialization (initialize, session/new baseline)

## Metadata

| Field | Value |
|---|---|
| Institute | Molodetz Institute — Research & Retrieval Division |
| Subject | cap-protocol |
| Document type | Source Dossier |
| Tier | 1 |
| Source title | ACP Initialization |
| Source URL | https://agentclientprotocol.com/protocol/v1/initialization.md |
| Source type | specification |
| Source date (published) | Unknown, not stated (living docs) |
| Date researched | 2026-10-18 |
| Researched by | tai (agent), model: Muse Spark, on behalf of retoor |
| Research method | direct page fetch, read in full (initialization handshake, version negotiation, client capabilities) plus session-setup page for session/new |
| Confidence | High |
| Status | Active |

## Summary

Connection baseline: `initialize` handshake negotiates client/agent capabilities (prompt content types, fs methods, terminals, elicitation modes, notices, compaction), and all agents MUST support `session/new`, `session/prompt`, `session/cancel`, `session/update`.

## Key findings

- The four-method MUST baseline is the liveness contract tai's ACP driver can rely on for any agent.
- Capability negotiation is where tai declines surface (notices, compaction, URL elicitation) and advertises coding-profile grants (fs, terminals); initialize carries `protocolVersion: 1`, `clientCapabilities`, and `clientInfo`.
- Version negotiation: agent answers with the same version or its latest; tai speaks v1 only and closes on anything else.
- `session/new` takes `{cwd, mcpServers}` and returns `{sessionId}` (see the session-setup dossier).

## Pros / strengths

- Explicit baseline + negotiation keeps a minimal driver compliant by construction.

## Cons / limitations / caveats

- v1 only; v2 migration (method renames) deferred until an agent requires it.
- Auth methods and MCP server passing are out of scope for tai's driver.

## Relevance to tai

Handshake design for the ACP driver: capability set tai advertises and the baseline it requires.

## Changelog

| Date | Change |
|---|---|
| 2026-10-18 | Initial dossier created. |