@agentproto/adapter-pi

AIP-45 AGENT-CLI adapter for earendil-works/pi (@earendil-works/pi-coding-agent) — an MIT, headless TypeScript coding agent. This adapter drives pi over its persistent JSON-over-stdio RPC mode (pi --mode rpc), spawned as a real child process.

import { pi, piRuntime } from "@agentproto/adapter-pi"

const session = await piRuntime().start()
for await (const evt of session.send({ role: "user", content: "list the files" })) {
  console.log(evt.kind)
}
await session.close()

MCP support — bridged into pi tools

Pi ships no native MCP client — but this adapter closes that gap. When the host injects mcpServers into connect() (the daemon's orchestration gateway, or any scoped toolset), the adapter bridges them into pi by exploiting pi's own TypeScript extension system:

1. At connect(), it enumerates each server's tools (tools/list), writes a per-session config JSON, and spawns pi with -e <mcp-bridge-extension.mjs> plus PI_MCP_BRIDGE_CONFIG.
2. The bundled extension registers one pi tool per MCP tool (namespaced mcp__<server>__<tool>); each tool's execute proxies the call to the MCP server over @modelcontextprotocol/sdk.

Net result: pi gains agentproto's full injected toolset, including agent_start when the daemon injects its gateway (--orchestrator flag), enabling sub-agent orchestration (capabilities.sub_agents: true). When no MCP servers are injected, behavior is unchanged (pi runs only its own built-in file/shell tools). Full mechanism, limitations, and caveats (image/binary-content, cancellation): MCP-BRIDGE.md.

What it is

Because pi has no native ACP/MCP protocol surface, this is a protocol: "proprietary" manifest: createAgentCliRuntime skips the built-in ACP/print subprocess plumbing and instead dynamic-imports this package's createAgentCliClient(definition) factory (see createProprietaryProtocolArm in @agentproto/driver-agent-cli). Unlike @agentproto/adapter-mastracode-inprocess (the in-process proprietary arm), this arm spawns a real child (pi --mode rpc) and translates pi's RPC event stream into the canonical StreamEvent taxonomy.

• Multi-provider — Anthropic, OpenAI, Google (Gemini), Moonshot AI. One provider key minimum. See SECRETS.md.
• Streaming — text + thinking deltas, tool-call/result lifecycle.
• Live duplex — pi's RPC mode supports steer / follow_up / abort mid-turn (capabilities.bidirectional: true).
• Resumable — pi persists sessions; the client captures pi's session id from get_state and reattaches via --session <id> (continuation.default: "native-resume").

Configuration

| Option | Type | Notes | | -------- | ------ | ----- | | model | string | Passed to pi's --model (accepts provider/id, e.g. anthropic/claude-sonnet-4-5, moonshotai/kimi-k2.7-code). | | effort | enum | Thinking level, mapped 1:1 to pi's set_thinking_level: off \| minimal \| low \| medium \| high \| xhigh. |

The pi binary is resolved from definition.bin (pi), overridable via the AGENTPROTO_PI_BIN env var (used by the gated smoke test to point at a local install without a global pi on PATH).

Safety

Pi has no built-in permission system — file, process, network and credential access run with the launching user's permissions, and non-interactive modes (including --mode rpc) show no trust prompt. Treat a pi session as arbitrary code execution. See SANDBOX.md.

Docs in this package

• PI.md — AIP-45 manifest overview.
• PI-RPC.md — the reverse-engineered RPC wire profile + the pi-event → StreamEvent mapping table.
• SECRETS.md — provider env slots.
• SANDBOX.md — no built-in permissions; containerization.

Built against pi 0.80.3. The event/command wire profile was reverse-engineered from pi source (packages/coding-agent/src/modes/rpc/* + core/agent-session.ts); see PI-RPC.md.