fix: add automatic text-start and text-end events

src/__tests__/tool-calling.test.ts

@@ -1467,8 +1467,8 @@ describe('Tool Calling', () => {
       expect(eventTypes).toContain('tool-call');
       expect(eventTypes).toContain('finish');
 
-      // Verify text content comes first and finish comes last
-      expect(eventTypes[0]).toBe('text-delta');
+      // Verify text-start comes first and finish comes last
+      expect(eventTypes[0]).toBe('text-start');
       expect(eventTypes[eventTypes.length - 1]).toBe('finish');
 
       // Verify tool call was completed correctly

src/helicone-language-model.ts

@@ -286,6 +286,10 @@ export class HeliconeLanguageModel implements LanguageModelV2 {
       // Map tool call index to ID for streaming chunks
       const indexToId: Map<number, string> = new Map();
 
+      // Track text parts for start/end events
+      const textStarted = new Set<string>();
+      const textEnded = new Set<string>();
+
       const textDecoder = new TextDecoder();
       const reader = response.body!.getReader();
 
@@ -314,6 +318,17 @@ export class HeliconeLanguageModel implements LanguageModelV2 {
                   }
                 }
 
+                // Complete any outstanding text parts before finishing
+                for (const id of textStarted) {
+                  if (!textEnded.has(id)) {
+                    controller.enqueue({
+                      type: 'text-end',
+                      id
+                    } as LanguageModelV2StreamPart);
+                    textEnded.add(id);
+                  }
+                }
+
                 controller.enqueue({
                   type: 'finish',
                   usage: usage as LanguageModelV2Usage,
@@ -371,17 +386,37 @@ export class HeliconeLanguageModel implements LanguageModelV2 {
                         toolCall.completed = true;
                       }
                     }
+
+                    // Complete any outstanding text parts
+                    for (const id of textStarted) {
+                      if (!textEnded.has(id)) {
+                        controller.enqueue({
+                          type: 'text-end',
+                          id
+                        } as LanguageModelV2StreamPart);
+                        textEnded.add(id);
+                      }
+                    }
                   }
 
                   const delta = choice.delta;
                   if (!delta) continue;
 
                   // Transform text content to text-delta events
                   if (delta.content) {
+                    const id = 'text-0';
+                    // Emit text-start before first text-delta
+                    if (!textStarted.has(id)) {
+                      controller.enqueue({
+                        type: 'text-start',
+                        id
+                      } as LanguageModelV2StreamPart);
+                      textStarted.add(id);
+                    }
                     controller.enqueue({
                       type: 'text-delta',
                       delta: delta.content,
-                      id: 'text-0'
+                      id
                     } as LanguageModelV2StreamPart);
                   }