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

probe timeouts must be positive

Error message

probe timeouts must be positive

What it means

Error "probe timeouts must be positive" thrown in rohitg00/ai-engineering-from-scratch.

Source

Thrown at phases/13-tools-and-protocols/08-building-an-mcp-client/code/main.py:303

    peer_name: str
    local_name: str
    description: str


class MultiServerClient:
    def __init__(
        self,
        *,
        supported_modern: tuple[str, ...] = (PROTOCOL_VERSION,),
        supported_legacy: tuple[str, ...] = (LEGACY_VERSION,),
        probe_version: str | None = None,
        discovery_timeout_ms: int = 1_000,
        legacy_probe_timeout_ms: int = 1_000,
    ) -> None:
        if not supported_modern or not supported_legacy:
            raise ValueError("at least one modern and legacy version must be configured")
        if discovery_timeout_ms <= 0 or legacy_probe_timeout_ms <= 0:
            raise ValueError("probe timeouts must be positive")
        self.supported_modern = supported_modern
        self.supported_legacy = supported_legacy
        self.probe_version = probe_version or supported_modern[0]
        self.discovery_timeout_ms = discovery_timeout_ms
        self.legacy_probe_timeout_ms = legacy_probe_timeout_ms
        self.client_capabilities = CLIENT_CAPABILITIES.copy()
        self.peers: dict[str, Peer] = {}
        self.registry: dict[str, MergedTool] = {}
        self._next_request_id = 1

    def _new_id(self) -> int:
        request_id = self._next_request_id
        self._next_request_id += 1
        return request_id

    def add_server(
        self,
        name: str,

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:303 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

• Timeouts: ETIMEDOUT, deadlines, and hung requests — what actually expires when a request times out.

AI-assisted analysis of rohitg00/ai-engineering-from-scratch@39ea8a1c6d (2026-08-26). Data as JSON: /api/errors/9e927e6541894386. Report an issue: GitHub.