BoundaryML/baml · error

Unsupported strategy provider: {}. Available ones are: {}

Error message

Unsupported strategy provider: {}. Available ones are: {}

What it means

Strategy-client construction error from the ClientProperty TryFrom impl: the provider kind is a Strategy variant this runtime does not implement. Unlike its sibling error, this message also lists the strategy providers that ARE available (round-robin, fallback), which helps when a baml config uses a strategy name introduced in a different baml version.

Source

Thrown at engine/baml-runtime/src/internal/llm_client/strategy/mod.rs:74

    }
}

impl TryFrom<(&ClientProperty, &RuntimeContext)> for LLMStrategyProvider {
    type Error = anyhow::Error;

    fn try_from((client, ctx): (&ClientProperty, &RuntimeContext)) -> Result<Self> {
        match &client.provider {
            ClientProvider::Strategy(strategy) => match strategy {
                StrategyClientProvider::RoundRobin => RoundRobinStrategy::try_from((client, ctx))
                    .map(Arc::new)
                    .map(LLMStrategyProvider::RoundRobin),
                StrategyClientProvider::Fallback => {
                    FallbackStrategy::try_from((client, ctx)).map(LLMStrategyProvider::Fallback)
                }
            },
            other => {
                let options = ["round-robin", "fallback"];
                anyhow::bail!(
                    "Unsupported strategy provider: {}. Available ones are: {}",
                    other,
                    options.join(", ")
                )
            }
        }
    }
}

impl WithRetryPolicy for LLMStrategyProvider {
    fn retry_policy_name(&self) -> Option<&str> {
        match self {
            LLMStrategyProvider::RoundRobin(strategy) => strategy.retry_policy.as_deref(),
            LLMStrategyProvider::Fallback(strategy) => strategy.retry_policy.as_deref(),
        }
    }
}

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Set provider to one of `round-robin` or `fallback` as listed in the error.
2. Fix typos in the strategy client's provider field.
3. If migrating configs, rename deprecated strategy provider values to the two supported ones.
4. Regenerate client code after editing the .baml file.

Example fix

// before
client<Strategy> S { provider sequential strategy { A B } }

// after
client<Strategy> S { provider round-robin strategy { A B } }

const ALLOWED = ['round-robin', 'fallback'];
if (!ALLOWED.includes(strategyClient.provider)) {
  throw new Error(`invalid strategy provider ${strategyClient.provider}; available: ${ALLOWED.join(', ')}`);
}

function isStrategyProvider(p) { return p === 'round-robin' || p === 'fallback'; }

try { loadStrategy(cfg); } catch (e) { if (String(e).includes('Available ones are')) console.error(e.message); }

When it happens

Trigger: Same as 1013: an unrecognized `provider` value in a strategy client block hits the `other =>` match arm during strategy construction.

Common situations: Typoed provider names, using `sequential`/`retry`-style names or model provider names in strategy clients, and stale configs from older BAML versions with different strategy names.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• Unsupported strategy provider: {}
• Invalid client property. Should have been a fallback propert
• Invalid client property. Should have been a round-robin prop
• unsupported: {message}
• Unsupported {} `{}`: {}

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/5e5b5386e6f1dccc. Report an issue: GitHub.