Honor cancellation during compaction streams

cmd/olliesrv/internal/agent/history.go

@@ -270,15 +270,25 @@ func (s *History) compact(ctx context.Context, b backend.Backend) (int, string,
 	}
 
 	var summary strings.Builder
-	for ev := range ch {
-		if ev.Content != "" {
-			summary.WriteString(ev.Content)
-		}
-		if ev.Done {
-			break
+	for {
+		select {
+		case <-ctx.Done():
+			return 0, "", ctx.Err()
+		case ev, ok := <-ch:
+			if !ok {
+				return 0, "", fmt.Errorf("compact: stream closed before completion")
+			}
+			if ev.Content != "" {
+				summary.WriteString(ev.Content)
+			}
+			if ev.Done {
+				goto summaryDone
+			}
 		}
 	}
 
+summaryDone:
+
 	summaryText := strings.TrimSpace(summary.String())
 	if summaryText == "" {
 		return 0, "", fmt.Errorf("compact: empty summary")
@@ -571,16 +581,26 @@ func (s *History) stripCold(ctx context.Context, b backend.Backend) (backend.Usa
 	var resp strings.Builder
 	var usage backend.Usage
 	var reported bool
-	for ev := range ch {
-		if ev.Content != "" {
-			resp.WriteString(ev.Content)
-		}
-		if ev.Done {
-			usage = ev.Usage
-			reported = true
-			break
+	for {
+		select {
+		case <-ctx.Done():
+			return usage, true
+		case ev, ok := <-ch:
+			if !ok {
+				return usage, true
+			}
+			if ev.Content != "" {
+				resp.WriteString(ev.Content)
+			}
+			if ev.Done {
+				usage = ev.Usage
+				reported = true
+				goto responseDone
+			}
 		}
 	}
+
+responseDone:
 	if !reported {
 		usage.InputTokens = len(sb.String()) / 4
 		usage.OutputTokens = resp.Len() / 4