From a1e299a3552f055f08905fa27451e578b8650536 Mon Sep 17 00:00:00 2001
From: sakurawztlt <154661250+sakurawztlt@users.noreply.github.com>
Date: Mon, 13 Apr 2026 18:17:08 +0800
Subject: [PATCH] =?UTF-8?q?fix:=20Anthropic=20=E9=9D=9E=E6=B5=81=E5=BC=8F?=
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b2e379cf 引入的 BufferedResponseAccumulator 已修复了 chat_completions
非流式路径和 responses OAuth 非流式路径，但遗漏了 Anthropic /v1/messages
非流式路径 (handleAnthropicBufferedStreamingResponse)。

当客户端请求 stream=false 且模型开启思考时，上游 response.completed
终态事件的 output 字段可能为空，实际 message 内容通过
response.output_text.delta 增量事件下发。旧代码只读终态事件的 Response，
导致客户端收到的 content 字段为空 ([{"type":"text"}])。

本 commit 将 b2e379cf 的相同修复模式镜像到 Anthropic 路径：在 SSE 扫描
过程中用 BufferedResponseAccumulator 累积 delta 内容，终态 output 为空
时通过 SupplementResponseOutput 补充重建。

同时修复 handleAnthropicBufferedStreamingResponse 遗漏 response.done
事件类型的问题，与 chat completions 路径保持一致，避免上游发送
response.done 时 handler 认不出终态事件、最终返回 502 的潜在问题。

BufferedResponseAccumulator 已在 chatcompletions_responses_test.go 有
完整单元测试覆盖（TextOnly/ToolCalls/Reasoning/Mixed/SupplementEmpty/
NoSupplementWhenOutputExists/EmptyDeltas/IgnoresNonFunctionCallItems），
本次复用相同累加器无需新增测试。
---
 backend/internal/service/openai_gateway_messages.go | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/backend/internal/service/openai_gateway_messages.go b/backend/internal/service/openai_gateway_messages.go
index 7a4862d3..a72b9bbf 100644
--- a/backend/internal/service/openai_gateway_messages.go
+++ b/backend/internal/service/openai_gateway_messages.go
@@ -270,6 +270,7 @@ func (s *OpenAIGatewayService) handleAnthropicBufferedStreamingResponse(
 
 	var finalResponse *apicompat.ResponsesResponse
 	var usage OpenAIUsage
+	acc := apicompat.NewBufferedResponseAccumulator()
 
 	for scanner.Scan() {
 		line := scanner.Text()
@@ -288,8 +289,12 @@ func (s *OpenAIGatewayService) handleAnthropicBufferedStreamingResponse(
 			continue
 		}
 
+		// Accumulate delta content for fallback when terminal output is empty.
+		acc.ProcessEvent(&event)
+
 		// Terminal events carry the complete ResponsesResponse with output + usage.
-		if (event.Type == "response.completed" || event.Type == "response.incomplete" || event.Type == "response.failed") &&
+		if (event.Type == "response.completed" || event.Type == "response.done" ||
+			event.Type == "response.incomplete" || event.Type == "response.failed") &&
 			event.Response != nil {
 			finalResponse = event.Response
 			if event.Response.Usage != nil {
@@ -318,6 +323,10 @@ func (s *OpenAIGatewayService) handleAnthropicBufferedStreamingResponse(
 		return nil, fmt.Errorf("upstream stream ended without terminal event")
 	}
 
+	// When the terminal event has an empty output array, reconstruct from
+	// accumulated delta events so the client receives the full content.
+	acc.SupplementResponseOutput(finalResponse)
+
 	anthropicResp := apicompat.ResponsesToAnthropic(finalResponse, originalModel)
 
 	if s.responseHeaderFilter != nil {