microsoft/semantic-kernel · error · ValueError

Unsupported service: {service}. Supported services are: {',

Error message

Unsupported service: {service}. Supported services are: {', '.join([s.value for s in Services])}

What it means

Raised by document_generator's CustomAgentBase.get_service() when the supplied service does not match a supported Services enum member. The method uses match/case over Services.AZURE_OPENAI and Services.OPENAI only; any other value (including a future enum member not yet wired up) falls to the default arm and raises ValueError listing the supported services.

Source

Thrown at python/samples/demos/document_generator/agents/custom_agent_base.py:75

        Returns:
            ChatCompletionClientBase: The AI service instance.

        """

        match service:
            case Services.AZURE_OPENAI:
                from azure.identity import AzureCliCredential

                from semantic_kernel.connectors.ai.open_ai import AzureChatCompletion

                return AzureChatCompletion(instruction_role=instruction_role, credential=AzureCliCredential())
            case Services.OPENAI:
                from semantic_kernel.connectors.ai.open_ai import OpenAIChatCompletion

                return OpenAIChatCompletion(instruction_role=instruction_role)
            case _:
                raise ValueError(
                    f"Unsupported service: {service}. Supported services are: {', '.join([s.value for s in Services])}"
                )

    @override
    async def invoke(
        self,
        *,
        messages: str | ChatMessageContent | list[str | ChatMessageContent] | None = None,
        thread: "AgentThread | None" = None,
        on_intermediate_message: Callable[[ChatMessageContent], Awaitable[None]] | None = None,
        arguments: KernelArguments | None = None,
        kernel: "Kernel | None" = None,
        additional_user_message: str | None = None,
        **kwargs: Any,
    ) -> AsyncIterable["AgentResponseItem[ChatMessageContent]"]:
        normalized_messages = self._normalize_messages(messages)

        if additional_user_message:

View on GitHub (pinned to c028a0c7dc)

Solutions

Use one of the supported Services members: Services.AZURE_OPENAI or Services.OPENAI when constructing the agent.
If you genuinely need a new service, add a case Services.<YOUR_SERVICE> branch returning a ChatCompletion base before the default arm.
Validate the service argument at the call site against the supported set before passing it in.
Check for typos / ensure you imported Services from the correct module.

Example fix

// before
agent = MyAgent(service='azure')  # string, not enum

// after
from .custom_agent_base import Services
agent = MyAgent(service=Services.AZURE_OPENAI)

Defensive patterns

Strategy: validation

Validate before calling

from .custom_agent_base import Services, CustomAgentBase
SUPPORTED = {Services.AZURE_OPENAI, Services.OPENAI}
if service not in SUPPORTED:
    raise ValueError(f'service must be one of {[s.value for s in SUPPORTED]}')
agent = MyAgent(service=service)

Type guard

from enum import Enum
from .custom_agent_base import Services

def is_supported_service(s) -> bool:
    return isinstance(s, Services) and s in {Services.AZURE_OPENAI, Services.OPENAI}

Prevention

Centralize the supported-set check in a factory function.
When extending the Services enum, add a failing test that requires a new case branch.
Never pass strings; always pass the enum member.

When it happens

Trigger: Instantiating a custom agent subclass with service=Services.<UNSUPPORTED>, or passing a service value not in {AZURE_OPENAI, OPENAI}; adding a new enum member to Services without adding a corresponding case branch.

Common situations: Extending the Services enum with a new backend (e.g. OLLAMA, ANTHROPIC) but forgetting to add the case; passing a string instead of the enum; downgrading/upgrade of semantic-kernel where enum members change.

Related errors

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/6be444c3dd402a2e. Report an issue: GitHub.