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

switchyard_libsy/algorithms/
passthrough.rs
