refactor: rely on content for single-line reasoning

Author: ammar-agent

src/browser/components/Messages/ReasoningMessage.tsx

@@ -18,10 +18,8 @@ export const ReasoningMessage: React.FC<ReasoningMessageProps> = ({ message, cla
   const isStreaming = message.isStreaming;
   const trimmedContent = content?.trim() ?? "";
   const hasContent = trimmedContent.length > 0;
-  const reasoningSegments = message.reasoningSegmentCount ?? 1;
   // OpenAI models often emit terse, single-line traces; surface them inline instead of hiding behind the label.
-  const isSingleLineTrace =
-    !isStreaming && hasContent && reasoningSegments === 1 && !/[\r\n]/.test(trimmedContent);
+  const isSingleLineTrace = !isStreaming && hasContent && !/[\r\n]/.test(trimmedContent);
   const isCollapsible = !isStreaming && hasContent && !isSingleLineTrace;
 
   // Auto-collapse when streaming ends

src/browser/utils/messages/StreamingMessageAggregator.ts

@@ -613,7 +613,6 @@ export class StreamingMessageAggregator {
       type: "reasoning",
       text: data.delta,
       timestamp: data.timestamp,
-      segmentCount: 1,
     });
 
     // Track delta for token counting and TPS calculation
@@ -799,20 +798,15 @@ export class StreamingMessageAggregator {
                 timestamp: lastMerged.timestamp ?? part.timestamp,
               };
             } else if (lastMerged?.type === "reasoning" && part.type === "reasoning") {
-              // Merge reasoning parts, preserving the first timestamp and accumulating segment count
+              // Merge reasoning parts, preserving the first timestamp
               mergedParts[mergedParts.length - 1] = {
                 type: "reasoning",
                 text: lastMerged.text + part.text,
                 timestamp: lastMerged.timestamp ?? part.timestamp,
-                segmentCount: (lastMerged.segmentCount ?? 1) + (part.segmentCount ?? 1),
               };
             } else {
               // Different type or tool part - add new part
-              if (part.type === "reasoning") {
-                mergedParts.push({ ...part, segmentCount: part.segmentCount ?? 1 });
-              } else {
-                mergedParts.push(part);
-              }
+              mergedParts.push(part);
             }
           }
 
@@ -849,7 +843,6 @@ export class StreamingMessageAggregator {
                 isPartial: message.metadata?.partial ?? false,
                 isLastPartOfMessage: isLastPart,
                 timestamp: part.timestamp ?? baseTimestamp,
-                reasoningSegmentCount: part.segmentCount ?? 1,
               });
             } else if (part.type === "text" && part.text) {
               // Skip empty text parts

src/common/types/message.ts

@@ -72,7 +72,6 @@ export interface MuxReasoningPart {
   type: "reasoning";
   text: string;
   timestamp?: number;
-  segmentCount?: number; // Number of merged reasoning deltas represented by this part
 }
 
 // File/Image part type for multimodal messages (matches AI SDK FileUIPart)
@@ -152,7 +151,6 @@ export type DisplayedMessage =
       isLastPartOfMessage?: boolean; // True if this is the last part of a multi-part message
       timestamp?: number;
       tokens?: number; // Reasoning tokens if available
-      reasoningSegmentCount?: number; // Number of merged reasoning deltas represented by this block
     }
   | {
       type: "stream-error";