rohitg00/ai-engineering-from-scratch · error · RuntimeError

{peer.name}: modern discovery omitted resultType

Error message

{peer.name}: modern discovery omitted resultType

What it means

Error "{peer.name}: modern discovery omitted resultType" thrown in rohitg00/ai-engineering-from-scratch.

Source

Thrown at phases/13-tools-and-protocols/08-building-an-mcp-client/code/main.py:346

            transport=transport,
            allow_legacy=allow_legacy,
        )

    @staticmethod
    def _send(
        peer: Peer,
        message: dict[str, Any],
        timeout_ms: int | None = None,
    ) -> dict[str, Any] | None:
        return peer.transport(message, timeout_ms)

    def _mutual_version(self, advertised: list[Any]) -> str | None:
        common = [version for version in advertised if version in self.supported_modern]
        return sorted(common, reverse=True)[0] if common else None

    def _activate_modern(self, peer: Peer, result: dict[str, Any], version: str) -> None:
        if result.get("resultType") != "complete":
            raise RuntimeError(f"{peer.name}: modern discovery omitted resultType")
        peer.era = "modern"
        peer.protocol_version = version
        peer.capabilities = result.get("capabilities", {})
        peer.server_info = result.get("_meta", {}).get(SERVER_INFO_KEY, {})
        peer.available = True

    def _probe_legacy(self, peer: Peer, trigger: str) -> None:
        if not peer.allow_legacy:
            raise RuntimeError(
                f"{peer.name}: {trigger}; legacy compatibility is not allowlisted"
            )
        request_id = self._new_id()
        initialize = legacy_request(
            request_id,
            "initialize",
            {
                "protocolVersion": self.supported_legacy[0],
                "capabilities": self.client_capabilities.copy(),

View on GitHub (pinned to 39ea8a1c6d)

When it happens

Trigger: Thrown at phases/13-tools-and-protocols/08-building-an-mcp-client/code/main.py:346 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of rohitg00/ai-engineering-from-scratch@39ea8a1c6d (2026-08-26). Data as JSON: /api/errors/f142f8c8745972d6. Report an issue: GitHub.