microsoft/semantic-kernel · error · AgentExecutionException

Agent Failure - Strategy unable to select next agent: {agent

Error message

Agent Failure - Strategy unable to select next agent: {agent_name}

What it means

The parser returned a name, but no agent in the group has a matching `.name` (`next((a for a in agents if a.name == agent_name), None)` is None). The error interpolates the offending name so you can see exactly what the function returned.

Source

Thrown at python/semantic_kernel/agents/strategies/selection/kernel_function_selection_strategy.py:114

        except Exception as ex:
            logger.error("Kernel Function Selection Strategy next method failed", exc_info=ex)
            raise AgentExecutionException("Agent Failure - Strategy failed to execute function.") from ex

        logger.info(
            f"Kernel Function Selection Strategy next method completed: "
            f"{self.function.plugin_name}, {self.function.name}, result: {result.value if result else None}",
        )

        agent_name = self.result_parser(result)
        if isawaitable(agent_name):
            agent_name = await agent_name

        if agent_name is None:
            raise AgentExecutionException("Agent Failure - Strategy unable to determine next agent.")

        agent_turn = next((agent for agent in agents if agent.name == agent_name), None)
        if agent_turn is None:
            raise AgentExecutionException(f"Agent Failure - Strategy unable to select next agent: {agent_name}")

        return agent_turn

View on GitHub (pinned to c028a0c7dc)

Solutions

1. Ensure every selectable agent is added to the group chat so its .name is in the agents list.
2. Make result_parser normalize the returned name (strip/lowercase) and map synonyms to the exact agent.name values.
3. Update the selection function's prompt/instructions to list only the valid agent names.
4. Log the returned {agent_name} to confirm exactly what the function emitted.

Example fix

// before
def parse(result):
    return result.value.strip()  # may return 'Agent One' but agent.name == 'agent_one'

// after
ALIASES = {"agent one": "agent_one", "agent_two": "agent_two"}
def parse(result):
    key = result.value.strip().lower()
    return ALIASES.get(key, key)

valid_names = {a.name for a in agents}
name = strategy.result_parser(result)
if name not in valid_names:
    raise ValueError(f'parsed name {name!r} not among agents {sorted(valid_names)}')

def is_known_agent(name: str, agents: list) -> bool:
    return name in {a.name for a in agents}

from semantic_kernel.exceptions.agent_exceptions import AgentExecutionException
try:
    agent = await strategy.next(agents, history)
except AgentExecutionException:
    agent = agents[0]  # graceful fallback

When it happens

Trigger: The selection function returns a name that is not among the agents passed to the strategy: a hallucinated name, a casing/whitespace mismatch, or an agent that was never added to the group chat.

Common situations: Agent not registered in the AgentGroupChat; the prompt given to the selection function lists names that differ from agent.name; the LLM returns a slightly different spelling, role label, or extra text; case sensitivity ('Agent1' vs 'agent1').

Related errors

• Agent Failure - Strategy failed to execute function.
• Agent Failure - Strategy unable to determine next agent.
• Agent Failure - No agents present to select.
• No agents to select from
• Unknown participant selected: {response.content}.

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/02b9fbc1b68713a8. Report an issue: GitHub.