adcp 10: a server's adcp_version pin doesn't set the version handlers receive; they always get the packaged 3.3-beta.0 #1685

Observed (adcp 10.0.0b0)

A server pinned to AdCP 3.2 still hands its handlers requests upgraded to the packaged 3.3-beta.0:

import asyncio
from typing import Any

from adcp.server import ADCPHandler
from adcp.server.mcp_tools import create_tool_caller


class Seller(ADCPHandler[Any]):
    _adcp_version = "3.2"

    async def get_products(self, params, context=None):
        print("handler sees adcp_version:", params.get("adcp_version") if isinstance(params, dict) else getattr(params, "adcp_version", None))
        return {"products": []}


call = create_tool_caller(Seller(), "get_products", supported_versions=["3.2"])
asyncio.run(call({"adcp_version": "3.2", "buying_mode": "brief", "brief": "shoes"}))

handler sees adcp_version: 3.3-beta.0

Cause: adcp/server/mcp_tools.py computes application_version = resolve_adcp_version(None), the packaged default, and converts every request from the wire version up to it. The handler's adcp_version pin and the server's supported_versions aren't consulted.

Why this is a bug, not just behaviour

MIGRATION_v9_to_v10.md says both things:

• "Pin adcp_version="3.2" on a client or server that must keep a 3.2 contract."
• "A PlatformHandler or create_adcp_server_from_platform(...) with supported_versions=["3.2"] and no adcp_version serves 3.2."

and also:

• "Handlers receive requests upgraded to 3.3-beta.0."

A seller that must keep a 3.2 contract can't, through any setting: its handler code and models see 3.3 payloads, and responses are converted down afterwards. A seller can't stay on a stable contract while the SDK's default is a pre-release.

Expected

The server's pinned (or newest supported) release is the application version requests are converted to, and responses are converted from. A 3.2-pinned seller's handlers then see 3.2. If that's not intended, the migration guide should say that a server pin governs only the wire, and that handler code always runs on the SDK's packaged release.

Impact

Found while exploring the Embedded Sales Agent on adcp 10 (draft scope3data/embedded-sales-agent#1042). ESA serves AdCP 3.2 natively. Its request hook had to treat an incoming adcp_version: "3.3-beta.0" (written by the SDK's upgrade) as its native 3.2. Its handlers now run on 3.3-beta models, so a pre-release protocol can change behaviour in a production seller.