feat(libsy): include session id in decision context

crates/libsy/src/algorithms/llm_class.rs

@@ -1388,6 +1388,7 @@ mod tests {
                         call.request.context,
                         json!({
                             "task": expected_task,
+                            "session": "session-1",
                             "candidates": ["a", "b", "c"],
                             "comparison": {"capable": "a", "efficient": "b"},
                             "evidence": settings.evidence,

crates/libsy/src/algorithms/llm_class/decision.rs

@@ -124,6 +124,7 @@ impl Classifier for DecisionClassifier {
             model: None,
             context: json!({
                 "task": self.input.messages(request),
+                "session": request.metadata.as_ref().and_then(|m| m.session_id.as_deref()),
                 "candidates": self.config.candidates.keys().collect::<Vec<_>>(),
                 "comparison": {
                     "capable": self.config.candidate(capable)?,

crates/switchyard-runner/tests/openai_decisions.rs

@@ -5,7 +5,7 @@ use std::sync::{Arc, mpsc};
 
 use serde_json::{Value, json};
 use switchyard_llm_client::RunObservation;
-use switchyard_protocol::{Request, Usage, text_request};
+use switchyard_protocol::{Metadata, Request, Usage, text_request};
 use switchyard_runner::Runner;
 use wiremock::matchers::{body_partial_json, header, method, path};
 use wiremock::{Mock, MockServer, ResponseTemplate};
@@ -84,6 +84,10 @@ evidence = {{ description = "Compare a and b" }}
         .execute(
             Request {
                 llm_request: text_request(None, "Route this request"),
+                metadata: Some(Metadata {
+                    session_id: Some("session-1".into()),
+                    ..Metadata::default()
+                }),
                 ..Request::default()
             },
             Some(Arc::new(move |event| {
@@ -114,6 +118,7 @@ evidence = {{ description = "Compare a and b" }}
         context["evidence"],
         json!({"description": "Compare a and b"})
     );
+    assert_eq!(context["session"], "session-1");
     server.verify().await;
     Ok(())
 }

crates/switchyard-server/CONFIGURATION.md

@@ -67,6 +67,7 @@ evidence = { candidates = { a = "Higher-quality model", b = "Lower-cost model" }
   Supply evidence from your evaluations and choose a cutoff using those results.
 - `decision.instructions` can replace the default relative-advantage instructions.
   It must preserve the meaning of `advantage` and `no_advantage`. Evidence is passed unchanged.
+- The context includes `session`, the request's session ID, or `null` when the request has none.
 - The capable tier is selected only when its advantage score exceeds `cutoff`.
   Client failures and deadlines use the capable tier by default; set `fail_open = false`
   on the route to propagate those errors.