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        let decision: Decision = Decision::new(
36            self.target.clone(),
37            Some(format!("passthrough selected target '{}'", self.target)),
38            true,
39        );
40        driver.decide(decision.clone()).await?;
41        driver.call_model(request, decision).await
42    }
43}
44
45#[cfg(test)]
46mod tests {
47    use std::sync::Arc;
48
49    use super::Passthrough;
50    use crate::core::algorithm::Algorithm;
51    use crate::core::testing::{echo, test_drive};
52    use switchyard_protocol::{Request, completion_text, text_request};
53
54    #[tokio::test]
55    async fn test_passthrough() -> crate::Result<()> {
56        const MODEL_ID: &str = "testing/passthrough";
57        let request = Request {
58            llm_request: text_request(Some("auto".to_string()), "hi"),
59            raw_request: None,
60            metadata: None,
61        };
62        let algorithm: Arc<dyn Algorithm> = Arc::new(Passthrough::new(MODEL_ID));
63        let (trace, response) = test_drive(algorithm, request, echo()).await?;
64
65        assert_eq!(
66            response
67                .llm_response
68                .as_agg()
69                .map(completion_text)
70                .unwrap_or_default(),
71            MODEL_ID
72        );
73        assert_eq!(trace.len(), 1);
74        assert_eq!(trace[0].selected_model_id(), MODEL_ID);
75        assert!(trace[0].is_answer_call());
76        Ok(())
77    }
78}
switchyard_libsy/algorithms/passthrough.rs

switchyard_libsy/algorithms/
passthrough.rs
