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::{ModelId, Request, Response};
9
10use crate::Result;
11use crate::core::algorithm::{Algorithm, Driver};
12use switchyard_protocol::Decision;
13
14/// Routing algorithm that always calls one configured target.
15pub struct Passthrough {
16    target: ModelId,
17}
18
19impl Passthrough {
20    /// Creates an algorithm that always calls `target`.
21    pub fn new(target: impl Into<ModelId>) -> Self {
22        Passthrough {
23            target: target.into(),
24        }
25    }
26}
27
28#[async_trait::async_trait]
29impl Algorithm for Passthrough {
30    fn name(&self) -> &str {
31        "passthrough"
32    }
33
34    async fn route(self: Arc<Self>, driver: Driver, request: Request) -> Result<Response> {
35        tracing::info!(target = %self.target, "passthrough selected target");
36        let decision: Decision = Decision::new(self.target.clone(), true);
37        driver.decide(decision.clone()).await?;
38        driver.call_model(request, decision).await
39    }
40}
41
42#[cfg(test)]
43mod tests {
44    use std::sync::Arc;
45
46    use super::Passthrough;
47    use crate::core::algorithm::Algorithm;
48    use crate::core::testing::{echo, test_drive};
49    use switchyard_protocol::{Request, completion_text, text_request};
50
51    #[tokio::test]
52    async fn test_passthrough() -> crate::Result<()> {
53        const MODEL_ID: &str = "testing/passthrough";
54        let request = Request {
55            llm_request: text_request(Some("auto".to_string()), "hi"),
56            raw_request: None,
57            metadata: None,
58        };
59        let algorithm: Arc<dyn Algorithm> = Arc::new(Passthrough::new(MODEL_ID));
60        let (trace, response) = test_drive(algorithm, request, echo()).await?;
61
62        assert_eq!(
63            response
64                .llm_response
65                .as_agg()
66                .map(completion_text)
67                .unwrap_or_default(),
68            MODEL_ID
69        );
70        assert_eq!(trace.len(), 1);
71        assert_eq!(trace[0].selected_model_id(), MODEL_ID);
72        assert!(trace[0].is_answer_call());
73        Ok(())
74    }
75}
switchyard_libsy/algorithms/passthrough.rs

switchyard_libsy/algorithms/
passthrough.rs
