diff --git a/crates/cortex-gateway/src/handlers.rs b/crates/cortex-gateway/src/handlers.rs
index af61a49..3c047d2 100644
--- a/crates/cortex-gateway/src/handlers.rs
+++ b/crates/cortex-gateway/src/handlers.rs
@@ -138,9 +138,10 @@ async fn anthropic_messages(
         }
     } else {
         // Non-streaming: proxy, buffer full response, translate back to Anthropic.
+        let target_url = format!("{}/v1/chat/completions", route.endpoint);
         let upstream_resp = fleet
             .http_client
-            .post(format!("{}/v1/chat/completions", route.endpoint))
+            .post(&target_url)
             .body(openai_body)
             .header("content-type", "application/json")
             .send()
@@ -150,7 +151,14 @@ async fn anthropic_messages(
             Ok(r) => r,
             Err(e) => {
                 metrics::counter!("cortex_request_errors_total", &labels).increment(1);
-                return error_response(502, &format!("upstream request failed: {e}"));
+                tracing::warn!(
+                    model = %model_id,
+                    node = %route.node_name,
+                    target = %target_url,
+                    error = %e,
+                    "anthropic proxy: upstream request failed (network)"
+                );
+                return error_response(502, "upstream request failed");
             }
         };
 
@@ -158,7 +166,16 @@ async fn anthropic_messages(
             metrics::counter!("cortex_request_errors_total", &labels).increment(1);
             let status = upstream_resp.status().as_u16();
             let body = upstream_resp.text().await.unwrap_or_default();
-            return error_response(status, &format!("upstream error: {body}"));
+            let body_snippet = body.chars().take(512).collect::<String>();
+            tracing::warn!(
+                model = %model_id,
+                node = %route.node_name,
+                target = %target_url,
+                status,
+                body = %body_snippet,
+                "anthropic proxy: upstream returned non-2xx"
+            );
+            return error_response(status, &format!("upstream returned {status}"));
         }
 
         let body_bytes = match upstream_resp.bytes().await {
diff --git a/crates/cortex-gateway/src/router.rs b/crates/cortex-gateway/src/router.rs
index cc0cef5..45acfc0 100644
--- a/crates/cortex-gateway/src/router.rs
+++ b/crates/cortex-gateway/src/router.rs
@@ -335,7 +335,13 @@ fn rewrite_loopback_host(inference_url: &str, neuron_endpoint: &str) -> Option<S
     let new_host = neuron.host_str()?;
     let mut out = inf.clone();
     out.set_host(Some(new_host)).ok()?;
-    Some(out.to_string())
+    // url::Url::to_string normalises an empty path to "/", which then
+    // breaks downstream callers that do format!("{endpoint}/v1/...")
+    // and produce a double slash. The proxy URL is treated as a base
+    // string that the caller appends paths to, so strip the trailing
+    // slash here.
+    let s = out.to_string();
+    Some(s.trim_end_matches('/').to_string())
 }
 
 #[cfg(test)]
@@ -350,14 +356,14 @@ mod tests {
         );
         assert_eq!(
             out.as_deref(),
-            Some("http://beast.hanzalova.internal:13131/")
+            Some("http://beast.hanzalova.internal:13131")
         );
     }
 
     #[test]
     fn rewrites_loopback_with_distinct_inference_port() {
         let out = rewrite_loopback_host("http://127.0.0.1:8080", "http://beast.lan:13131");
-        assert_eq!(out.as_deref(), Some("http://beast.lan:8080/"));
+        assert_eq!(out.as_deref(), Some("http://beast.lan:8080"));
     }
 
     #[test]