🤖 feat: add mode to stream-start events for plan/exec breakdown

- Add mode field to StreamStartEventSchema
- Propagate mode from initialMetadata in streamManager (live + replay)
- Include mode in aiService context_exceeded and tool-policy-noop events
- Store mode in StreamingContext and return from getActiveStreamTimingStats
- Update mock scenario types to support mode
- The 'Split by mode' checkbox now appears when mode data is available

Change-Id: I7fc9df3551ff282708eb3d189818f27fbc05d674
Signed-off-by: Thomas Kosiewski <tk@coder.com>

Author: ThomasK33

src/browser/utils/messages/StreamingMessageAggregator.ts

@@ -644,6 +644,8 @@ export class StreamingMessageAggregator {
     liveTokenCount: number;
     /** Live tokens-per-second (trailing window) */
     liveTPS: number;
+    /** Mode (plan/exec) for this stream */
+    mode?: "plan" | "exec";
   } | null {
     // Get the first (and typically only) active stream
     const entries = Array.from(this.activeStreams.entries());
@@ -664,6 +666,7 @@ export class StreamingMessageAggregator {
       model: context.model,
       liveTokenCount: this.getStreamingTokenCount(messageId),
       liveTPS: this.getStreamingTPS(messageId),
+      mode: context.mode,
     };
   }
 
@@ -881,6 +884,7 @@ export class StreamingMessageAggregator {
       firstTokenTime: null,
       toolExecutionMs: 0,
       pendingToolStarts: new Map(),
+      mode: data.mode,
     };
 
     // Use messageId as key - ensures only ONE stream per message

src/common/orpc/schemas/stream.ts

@@ -43,6 +43,9 @@ export const StreamStartEventSchema = z.object({
   startTime: z.number().meta({
     description: "Backend timestamp when stream started (Date.now())",
   }),
+  mode: z.enum(["plan", "exec"]).optional().meta({
+    description: "Agent mode (plan/exec) for this stream",
+  }),
 });
 
 export const StreamDeltaEventSchema = z.object({

src/node/services/aiService.ts

@@ -1344,6 +1344,7 @@ export class AIService extends EventEmitter {
           model: modelString,
           historySequence,
           startTime: Date.now(),
+          ...(uiMode && { mode: uiMode }),
         };
         this.emit("stream-start", streamStartEvent);
 
@@ -1380,6 +1381,7 @@ export class AIService extends EventEmitter {
           model: modelString,
           historySequence,
           startTime: Date.now(),
+          ...(uiMode && { mode: uiMode }),
         };
         this.emit("stream-start", streamStartEvent);
 

src/node/services/mock/mockScenarioPlayer.ts

@@ -273,6 +273,7 @@ export class MockScenarioPlayer {
           model: event.model,
           historySequence,
           startTime: Date.now(),
+          ...(event.mode && { mode: event.mode }),
         };
         this.deps.aiService.emit("stream-start", payload);
         break;

src/node/services/mock/scenarioTypes.ts

@@ -20,6 +20,7 @@ export interface MockStreamStartEvent extends MockAssistantEventBase {
   kind: "stream-start";
   messageId: string;
   model: string;
+  mode?: "plan" | "exec";
 }
 
 export interface MockStreamDeltaEvent extends MockAssistantEventBase {

src/node/services/streamManager.ts

@@ -789,14 +789,16 @@ export class StreamManager extends EventEmitter {
       // Update state to streaming
       streamInfo.state = StreamState.STREAMING;
 
-      // Emit stream start event
+      // Emit stream start event (include mode from initialMetadata if available)
+      const streamStartMode = streamInfo.initialMetadata?.mode as "plan" | "exec" | undefined;
       this.emit("stream-start", {
         type: "stream-start",
         workspaceId: workspaceId as string,
         messageId: streamInfo.messageId,
         model: streamInfo.model,
         historySequence,
         startTime: streamInfo.startTime,
+        ...(streamStartMode && { mode: streamStartMode }),
       } as StreamStartEvent);
 
       // Initialize token tracker for this model
@@ -1690,14 +1692,16 @@ export class StreamManager extends EventEmitter {
     // Initialize token tracker for this model (required for tokenization)
     await this.tokenTracker.setModel(streamInfo.model);
 
-    // Emit stream-start event
+    // Emit stream-start event (include mode from initialMetadata if available)
+    const replayMode = streamInfo.initialMetadata?.mode as "plan" | "exec" | undefined;
     this.emit("stream-start", {
       type: "stream-start",
       workspaceId,
       messageId: streamInfo.messageId,
       model: streamInfo.model,
       historySequence: streamInfo.historySequence,
       startTime: streamInfo.startTime,
+      ...(replayMode && { mode: replayMode }),
     });
 
     // Replay accumulated parts as events using shared emission logic