fix: parallelize Workbench session summary reads (#1900)

internal/workbenchruntime/service.go

@@ -1166,19 +1166,39 @@ func (s *Server) querySummaryFacts(ctx context.Context, sessions []map[string]an
 	sessionIDs := uniqueStrings(mapSessions(sessions, sessionID))
 	traceIDs := uniqueStrings(mapSessions(sessions, lastTraceID))
 	facts := emptyFacts()
+	type summaryFactsResult struct {
+		kind             string
+		messageSummaries []any
+		facts            map[string][]any
+		err              error
+	}
+	resultCount := 0
+	results := make(chan summaryFactsResult, 2)
 	if len(sessionIDs) > 0 {
-		messageSummaries, err := s.queryMessageSummaries(ctx, sessionIDs)
-		if err != nil {
-			return nil, err
-		}
-		facts["messageSummaries"] = messageSummaries
+		resultCount++
+		go func() {
+			messageSummaries, err := s.queryMessageSummaries(ctx, sessionIDs)
+			results <- summaryFactsResult{kind: "messageSummaries", messageSummaries: messageSummaries, err: err}
+		}()
 	}
 	if len(traceIDs) > 0 {
-		byTrace, err := s.queryFacts(ctx, factQuery{TraceIDs: traceIDs, Families: []string{"turns", "checkpoints"}, Limit: len(traceIDs), TurnsOrder: "updated_desc", CheckpointsOrder: "updated_desc"})
-		if err != nil {
-			return nil, err
+		resultCount++
+		go func() {
+			byTrace, err := s.queryFacts(ctx, factQuery{TraceIDs: traceIDs, Families: []string{"turns", "checkpoints"}, Limit: len(traceIDs), TurnsOrder: "updated_desc", CheckpointsOrder: "updated_desc"})
+			results <- summaryFactsResult{kind: "traceFacts", facts: byTrace, err: err}
+		}()
+	}
+	for i := 0; i < resultCount; i++ {
+		result := <-results
+		if result.err != nil {
+			return nil, result.err
+		}
+		switch result.kind {
+		case "messageSummaries":
+			facts["messageSummaries"] = result.messageSummaries
+		case "traceFacts":
+			facts = mergeFacts(facts, result.facts)
 		}
-		facts = mergeFacts(facts, byTrace)
 	}
 	return facts, nil
 }