diff --git a/crates/libsy-llm-client/tests/observability.rs b/crates/libsy-llm-client/tests/observability.rs
index 8ae0a551e..bd0bc7033 100644
--- a/crates/libsy-llm-client/tests/observability.rs
+++ b/crates/libsy-llm-client/tests/observability.rs
@@ -795,7 +795,10 @@ async fn successful_run_records_metrics_spans_and_outcome_metadata() -> switchya
         Some(json!({
             "source": "llm-classifier", "score": 0.9, "threshold": 0.5,
             "verdict": "continue", "trigger": "turn", "reason_code": "test",
-            "confidence": "wrong type", "unknown": LEAKED_CONTENT,
+            "confidence": "algorithm-defined", "custom": {
+                "candidates": ["fast", "quality"], "accepted": true, "optional": null,
+                "note": "quoted \"value\"\nnext line",
+            },
         })),
     );
     let algorithm = Arc::new(SingleCallAlgo {
@@ -879,22 +882,22 @@ async fn successful_run_records_metrics_spans_and_outcome_metadata() -> switchya
             .count(),
         1
     );
-    for (field, expected) in [
-        ("outcome_id", metadata.outcome_id()),
-        ("evidence.source", "llm-classifier"),
-        ("evidence.score", "0.9"),
-        ("evidence.threshold", "0.5"),
-        ("evidence.verdict", "continue"),
-        ("evidence.trigger", "turn"),
-        ("evidence.reason_code", "test"),
-    ] {
-        assert_eq!(
-            run_span.fields.get(field).map(String::as_str),
-            Some(expected),
-            "{field}"
-        );
-    }
-    assert!(!run_span.fields.contains_key("evidence.confidence"));
+    assert_eq!(
+        run_span.fields.get("outcome_id").map(String::as_str),
+        Some(metadata.outcome_id())
+    );
+    let evidence = metadata.evidence.as_ref().expect("outcome evidence");
+    assert_eq!(
+        serde_json::from_str::<serde_json::Value>(&run_span.fields["evidence"])
+            .expect("JSON evidence"),
+        *evidence
+    );
+    assert!(
+        !run_span
+            .fields
+            .keys()
+            .any(|key| key.starts_with("evidence."))
+    );
     assert!(!format!("{run_span:?}").contains(LEAKED_CONTENT));
     let exported = span_exporter.get_finished_spans().expect("exported spans");
     let exported_run = exported
@@ -906,8 +909,14 @@ async fn successful_run_records_metrics_spans_and_outcome_metadata() -> switchya
         })
         .expect("outcome span exported");
     assert_eq!(
-        otel_attribute(exported_run, "evidence.score"),
-        Some(&OtelValue::F64(0.9))
+        otel_attribute(exported_run, "evidence"),
+        Some(&OtelValue::String(evidence.to_string().into()))
+    );
+    assert!(
+        !exported_run
+            .attributes
+            .iter()
+            .any(|attr| attr.key.as_str().starts_with("evidence."))
     );
     assert_eq!(
         otel_attribute(exported_run, "selected_model_ids"),
@@ -1213,6 +1222,11 @@ async fn streamed_usage_updates_the_client_call_span() -> switchyard_libsy::Resu
 
     let spans = store.spans();
     let client_span = find_span(&spans, "libsy.client_call", "selected_model", MODEL);
+    assert!(
+        !find_span(&spans, "libsy.run", "algorithm", ALGO)
+            .fields
+            .contains_key("evidence")
+    );
     for (field, value) in [
         ("otel.name", "chat obs-stream-model"),
         ("gen_ai.request.stream", "true"),
diff --git a/crates/libsy/src/core/algorithm.rs b/crates/libsy/src/core/algorithm.rs
index 6e01c20c7..44a38a350 100644
--- a/crates/libsy/src/core/algorithm.rs
+++ b/crates/libsy/src/core/algorithm.rs
@@ -386,9 +386,8 @@ impl RoutingIdentity {
 /// [`OutcomeMetadata::outcome_id`](crate::OutcomeMetadata::outcome_id) on `libsy.run`,
 /// alongside `selected_model_ids` (an ordered OpenTelemetry string array).
 /// `algorithm` and `switchyard.algorithm` retain the run's [`Algorithm::name`].
-/// Optional `evidence.source`, `evidence.verdict`, `evidence.trigger`, and
-/// `evidence.reason_code` are strings; `evidence.score`, `evidence.confidence`, and
-/// `evidence.threshold` are numbers. Unknown evidence fields are not exported.
+/// Optional `evidence` is the full JSON serialized as a string for consumers to parse.
+/// Keep it small and free of private data; nothing is filtered or redacted.
 /// These fields are span attributes, never metric labels.
 ///
 /// The run/call observability helpers retain `outcome` status and operational metrics,
diff --git a/crates/libsy/src/observability.rs b/crates/libsy/src/observability.rs
index 69c6d9295..269f3bf9b 100644
--- a/crates/libsy/src/observability.rs
+++ b/crates/libsy/src/observability.rs
@@ -71,13 +71,7 @@ pub(crate) fn run_span(algorithm: &str, request: &Request) -> Span {
         "libsy.run",
         algorithm,
         outcome_id = tracing::field::Empty,
-        evidence.source = tracing::field::Empty,
-        evidence.score = tracing::field::Empty,
-        evidence.confidence = tracing::field::Empty,
-        evidence.threshold = tracing::field::Empty,
-        evidence.verdict = tracing::field::Empty,
-        evidence.trigger = tracing::field::Empty,
-        evidence.reason_code = tracing::field::Empty,
+        evidence = tracing::field::Empty,
         switchyard.algorithm = algorithm,
         openinference.span.kind = "CHAIN",
         switchyard.route = tracing::field::Empty,
@@ -114,8 +108,7 @@ pub(crate) fn run_span(algorithm: &str, request: &Request) -> Span {
 }
 
 /// Projects a successful outcome onto the existing run span. Model IDs are an
-/// ordered OpenTelemetry string array, preserving fallback order. Evidence uses typed fields;
-/// unknown keys and values of the wrong type are omitted.
+/// ordered OpenTelemetry string array, preserving fallback order. Evidence is a JSON string.
 pub(crate) fn record_outcome(metadata: &OutcomeMetadata, models: &[ModelId]) {
     let span = Span::current();
     span.record("outcome_id", metadata.outcome_id());
@@ -129,25 +122,7 @@ pub(crate) fn record_outcome(metadata: &OutcomeMetadata, models: &[ModelId]) {
         )),
     );
     if let Some(evidence) = &metadata.evidence {
-        for (key, field) in [
-            ("source", "evidence.source"),
-            ("verdict", "evidence.verdict"),
-            ("trigger", "evidence.trigger"),
-            ("reason_code", "evidence.reason_code"),
-        ] {
-            if let Some(value) = evidence.get(key).and_then(serde_json::Value::as_str) {
-                span.record(field, value);
-            }
-        }
-        for (key, field) in [
-            ("score", "evidence.score"),
-            ("confidence", "evidence.confidence"),
-            ("threshold", "evidence.threshold"),
-        ] {
-            if let Some(value) = evidence.get(key).and_then(serde_json::Value::as_f64) {
-                span.record(field, value);
-            }
-        }
+        span.record("evidence", tracing::field::display(evidence));
     }
 }