openai: don't skip chunk when having token usage (#706)

Author: liuzengh

model/openai/openai.go

@@ -1348,7 +1348,8 @@ func (m *Model) shouldSuppressChunk(chunk openai.ChatCompletionChunk) bool {
 // 2. Check content - if valid, don't skip (even if empty string)
 // 3. Check refusal - if valid, don't skip
 // 4. Check toolcalls - if valid but array is empty, skip (defensive against panic)
-// 5. Otherwise, skip
+// 5. Check usage - if valid, don't skip
+// 6. Otherwise, skip
 func (m *Model) shouldSkipEmptyChunk(chunk openai.ChatCompletionChunk) bool {
 	// No choices available, don't skip (let it be processed normally).
 	if len(chunk.Choices) == 0 {
@@ -1373,6 +1374,10 @@ func (m *Model) shouldSkipEmptyChunk(chunk openai.ChatCompletionChunk) bool {
 		return len(delta.ToolCalls) == 0
 	}
 
+	if chunk.Usage.CompletionTokens > 0 || chunk.Usage.PromptTokens > 0 || chunk.Usage.TotalTokens > 0 {
+		return false
+	}
+
 	// Otherwise there is no meaningful delta, skip the chunk.
 	return true
 }