switchyard_libsy/algorithms/
passthrough.rs

1// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
2// SPDX-License-Identifier: Apache-2.0
3
4//! Single-target routing for direct model calls and integration diagnostics.
5
6use std::sync::Arc;
7
8use switchyard_protocol::{Category, Request};
9
10use crate::core::algorithm::{Algorithm, Driver};
11use crate::{LibsyError, Result, RoutingOutcome};
12
13/// Routing algorithm that always selects one configured target.
14pub struct Passthrough;
15
16#[async_trait::async_trait]
17impl Algorithm for Passthrough {
18    fn name(&self) -> &str {
19        "passthrough"
20    }
21
22    async fn route(self: Arc<Self>, driver: Driver, request: Request) -> Result<RoutingOutcome> {
23        let models = driver.models_for(&Category::Any).to_vec();
24        // Selected is the first one. The rest are fallbacks.
25        let Some(target) = models.first() else {
26            return Err(LibsyError::NoTargets);
27        };
28        tracing::info!(target = %target, "passthrough selected target");
29        Ok(RoutingOutcome::route_to(
30            target.clone(),
31            models[1..].to_vec(),
32            request,
33        ))
34    }
35}
36
37#[cfg(test)]
38mod tests {
39    use std::sync::Arc;
40
41    use super::Passthrough;
42    use crate::core::algorithm::Algorithm;
43    use crate::core::testing::{category_models, echo, test_drive_with_models};
44    use switchyard_protocol::{Category, Request, completion_text, text_request};
45
46    #[tokio::test]
47    async fn test_passthrough() -> crate::Result<()> {
48        const MODEL_ID: &str = "testing/passthrough";
49        let request = Request {
50            llm_request: text_request(Some("auto".to_string()), "hi"),
51            raw_request: None,
52            metadata: None,
53        };
54        let algorithm: Arc<dyn Algorithm> = Arc::new(Passthrough);
55        let models = category_models(Category::Any, &[MODEL_ID]);
56        let (selected_model, response) =
57            test_drive_with_models(algorithm, request, models, echo()).await?;
58
59        assert_eq!(
60            response
61                .llm_response
62                .as_agg()
63                .map(completion_text)
64                .unwrap_or_default(),
65            MODEL_ID
66        );
67        assert_eq!(selected_model, MODEL_ID);
68        Ok(())
69    }
70}
switchyard_libsy/algorithms/passthrough.rs

switchyard_libsy/algorithms/
passthrough.rs
