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::{Request, Response};
9
10use crate::Result;
11use crate::core::algorithm::{Algorithm, Driver, LlmTarget};
12use switchyard_protocol::{Context, Decision};
13
14/// Routing algorithm that always calls one configured target.
15pub struct Passthrough {
16    target: LlmTarget,
17}
18
19impl Passthrough {
20    /// Creates an algorithm that always calls `target`.
21    pub fn new(target: LlmTarget) -> Self {
22        Passthrough { target }
23    }
24}
25
26/// Decision emitted before [`Passthrough`] calls its configured target.
27pub struct PassthroughDecision {
28    model_id: String,
29}
30
31impl Decision for PassthroughDecision {
32    fn selected_model(&self) -> &str {
33        &self.model_id
34    }
35    fn reasoning(&self) -> Option<&str> {
36        // There is no decision to take, so no reasoning
37        None
38    }
39    fn as_any(&self) -> &dyn std::any::Any {
40        self
41    }
42}
43
44#[async_trait::async_trait]
45impl Algorithm for Passthrough {
46    fn name(&self) -> &str {
47        "passthrough"
48    }
49
50    async fn create_run_task(
51        self: Arc<Self>,
52        ctx: Context,
53        driver: Driver,
54        request: Request,
55    ) -> Result<Response> {
56        let decision: Arc<dyn Decision> = Arc::new(PassthroughDecision {
57            model_id: self.target.semantic_name.clone(),
58        });
59        driver.info(ctx.clone(), decision.clone()).await?;
60        driver
61            .call_llm_target(ctx, &self.target, request, decision)
62            .await
63    }
64}
65
66#[cfg(test)]
67mod tests {
68    use std::sync::Arc;
69
70    use super::Passthrough;
71    use crate::core::algorithm::{Algorithm, LlmTarget};
72    use switchyard_protocol::{
73        Context, Decision, LlmResponse, Request, Response, RoutedLlmClient, completion_text,
74        text_request, text_response,
75    };
76
77    /// Echoes the selected target so tests can inspect which target was called.
78    /// TODO: Duplicated from rand.rs
79    struct EchoClient;
80
81    #[async_trait::async_trait]
82    impl RoutedLlmClient for EchoClient {
83        async fn call(
84            &self,
85            _ctx: Context,
86            _request: Request,
87            decision: Arc<dyn Decision>,
88        ) -> std::result::Result<Response, switchyard_protocol::LlmClientError> {
89            Ok(Response {
90                llm_response: LlmResponse::Agg(text_response(None, decision.selected_model())),
91                metadata: None,
92            })
93        }
94    }
95
96    #[tokio::test]
97    async fn test_passthrough() -> crate::Result<()> {
98        const MODEL_ID: &str = "testing/passthrough";
99        let request = Request {
100            llm_request: text_request(Some("auto".to_string()), "hi"),
101            raw_request: None,
102            metadata: None,
103        };
104        let algorithm: Arc<dyn Algorithm> = Arc::new(Passthrough::new(LlmTarget {
105            semantic_name: MODEL_ID.to_string(),
106            llm_client: Some(Arc::new(EchoClient)),
107        }));
108        let (trace, response) = algorithm.run(Context::default(), request).await?;
109
110        assert_eq!(
111            response
112                .llm_response
113                .as_agg()
114                .map(completion_text)
115                .unwrap_or_default(),
116            MODEL_ID
117        );
118        assert_eq!(trace.len(), 1);
119        assert_eq!(trace[0].selected_model(), MODEL_ID);
120        Ok(())
121    }
122}
switchyard_libsy/algorithms/passthrough.rs

switchyard_libsy/algorithms/
passthrough.rs
