observability support

Signed-off-by: JaredforReal <w13431838023@gmail.com>

Author: JaredforReal

src/semantic-router/pkg/extproc/request_handler.go

@@ -339,6 +339,9 @@ func (r *OpenAIRouter) handleRequestHeaders(v *ext_proc.ProcessingRequest_Reques
 			return r.createErrorResponse(404, "Responses API not enabled"), nil
 		}
 
+		// Metrics: record that adapter is handling this request
+		metrics.ResponsesAdapterRequests.WithLabelValues("false").Inc()
+
 		// Prepare header mutation to rewrite :path to legacy chat completions
 		// Actual body mapping occurs in handleRequestBody
 		newPath := strings.Replace(path, "/v1/responses", "/v1/chat/completions", 1)

src/semantic-router/pkg/extproc/response_handler.go

@@ -213,6 +213,7 @@ func (r *OpenAIRouter) handleResponseBody(v *ext_proc.ProcessingRequest_Response
 							},
 						},
 					}
+					metrics.ResponsesAdapterSSEEvents.WithLabelValues("response.completed").Inc()
 					return response, nil
 				}
 
@@ -239,6 +240,13 @@ func (r *OpenAIRouter) handleResponseBody(v *ext_proc.ProcessingRequest_Response
 							sb.WriteString("data: ")
 							sb.Write(ev)
 							sb.WriteString("\n\n")
+							// Inspect the event type for metrics
+							var et map[string]interface{}
+							if err := json.Unmarshal(ev, &et); err == nil {
+								if t, _ := et["type"].(string); t != "" {
+									metrics.ResponsesAdapterSSEEvents.WithLabelValues(t).Inc()
+								}
+							}
 						}
 						v.ResponseBody.Body = []byte(sb.String())
 					}

src/semantic-router/pkg/metrics/metrics.go

@@ -380,6 +380,24 @@ var (
 		},
 		[]string{"fallback_reason", "fallback_strategy"},
 	)
+
+	// ResponsesAdapterRequests counts requests handled via the Responses adapter
+	ResponsesAdapterRequests = promauto.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "llm_responses_adapter_requests_total",
+			Help: "Total number of /v1/responses requests handled by the adapter",
+		},
+		[]string{"streaming"},
+	)
+
+	// ResponsesAdapterSSEEvents counts emitted Responses SSE events during translation
+	ResponsesAdapterSSEEvents = promauto.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "llm_responses_adapter_sse_events_total",
+			Help: "Total number of Responses SSE events emitted by the adapter",
+		},
+		[]string{"event_type"},
+	)
 )
 
 // RecordModelRequest increments the counter for requests to a specific model