fix: claude model can not access image

internal/backend/agent/model/anthropic.go

@@ -156,6 +156,18 @@ func anthropicEndpointURL(baseURL string) string {
 	return base + "/v1/messages"
 }
 
+// shouldRelocateAnthropicImages 判断是否需要把图片块搬运到末条 user 消息。
+//
+// 官方 Anthropic 端点（api.anthropic.com）可正确处理任意位置的图片，保持原样；
+// 其余第三方中转站默认启用搬运，规避「非末尾图片被丢弃」的转换问题。
+func shouldRelocateAnthropicImages(baseURL string) bool {
+	base := strings.ToLower(strings.TrimSpace(baseURL))
+	if base == "" {
+		return false
+	}
+	return !strings.Contains(base, "api.anthropic.com")
+}
+
 // ApplyAnthropicCompatibleAuthHeaders 同时兼容 Anthropic 原生 x-api-key 和 Bearer token 代理。
 func ApplyAnthropicCompatibleAuthHeaders(httpReq *http.Request, apiKey string) {
 	if httpReq == nil {
@@ -215,8 +227,9 @@ func (adapter *AnthropicAdapter) Stream(ctx context.Context, req StreamRequest,
 	body := cloneRequestBodyOverride(req.RequestBodyOverride)
 	if len(body) == 0 {
 		thinkingConfig := buildAnthropicThinkingConfig(req)
+		relocateImages := shouldRelocateAnthropicImages(baseURL)
 		stableMessageCount := anthropicStableProviderMessageCount(req.Messages, req.StableMessageCount, thinkingConfig != nil)
-		systemParts, messages, err := normalizeAnthropicProviderMessages(req.Messages, thinkingConfig != nil)
+		systemParts, messages, err := normalizeAnthropicProviderMessages(req.Messages, thinkingConfig != nil, relocateImages)
 		if err != nil {
 			return err
 		}
@@ -1066,7 +1079,7 @@ func anthropicStableProviderMessageCount(input []Message, stableReplayMessageCou
 	if len(stableReplayMessages) == 0 {
 		return 0
 	}
-	_, messages, err := normalizeAnthropicProviderMessages(stableReplayMessages, thinkingEnabled)
+	_, messages, err := normalizeAnthropicProviderMessages(stableReplayMessages, thinkingEnabled, false)
 	if err != nil {
 		return 0
 	}
@@ -1122,7 +1135,7 @@ func isAnthropicCacheableBlock(block map[string]any) bool {
 	}
 }
 
-func normalizeAnthropicProviderMessages(input []Message, thinkingEnabled bool) ([]string, []anthropicMessage, error) {
+func normalizeAnthropicProviderMessages(input []Message, thinkingEnabled bool, relocateImages bool) ([]string, []anthropicMessage, error) {
 	systemParts := make([]string, 0, len(input))
 	messages := make([]anthropicMessage, 0, len(input))
 	pendingToolResults := make([]map[string]any, 0, 2)
@@ -1208,9 +1221,70 @@ func normalizeAnthropicProviderMessages(input []Message, thinkingEnabled bool) (
 		}
 	}
 	flushToolResults()
+	if relocateImages {
+		messages = relocateAnthropicImagesToLastUserMessage(messages)
+	}
 	return systemParts, messages, nil
 }
 
+// relocateAnthropicImagesToLastUserMessage 把所有 user 消息里的 image 块搬运到最后一条 user 消息的末尾。
+//
+// 背景：部分第三方中转站（如 Bedrock 代理）在 Anthropic→上游 的消息转换中，
+// 会丢弃「后面还跟着大量文本/消息」的非末尾图片块。将图片统一移动到末条 user 消息
+// 可规避该问题，同时保留图片信息本身。
+//
+// 数据流演变：
+//
+//	[user_info] [query + IMG] [reminder] [reminder] [current_request]
+//	→ [user_info] [query] [reminder] [reminder] [current_request + IMG]
+//
+// 搬运后若某条 user 消息 content 变空，则丢弃该消息，避免 Anthropic 拒绝空内容消息。
+func relocateAnthropicImagesToLastUserMessage(messages []anthropicMessage) []anthropicMessage {
+	lastUserIndex := -1
+	for index := len(messages) - 1; index >= 0; index-- {
+		if strings.TrimSpace(messages[index].Role) == "user" {
+			lastUserIndex = index
+			break
+		}
+	}
+	if lastUserIndex < 0 {
+		return messages
+	}
+
+	relocated := make([]map[string]any, 0, 2)
+	for index := 0; index < len(messages); index++ {
+		if index == lastUserIndex || strings.TrimSpace(messages[index].Role) != "user" {
+			continue
+		}
+		kept := make([]map[string]any, 0, len(messages[index].Content))
+		for _, block := range messages[index].Content {
+			if isAnthropicImageBlock(block) {
+				relocated = append(relocated, block)
+				continue
+			}
+			kept = append(kept, block)
+		}
+		messages[index].Content = kept
+	}
+	if len(relocated) == 0 {
+		return messages
+	}
+	messages[lastUserIndex].Content = append(messages[lastUserIndex].Content, relocated...)
+
+	compacted := make([]anthropicMessage, 0, len(messages))
+	for index, message := range messages {
+		if index != lastUserIndex && strings.TrimSpace(message.Role) == "user" && len(message.Content) == 0 {
+			continue
+		}
+		compacted = append(compacted, message)
+	}
+	return compacted
+}
+
+func isAnthropicImageBlock(block map[string]any) bool {
+	return strings.TrimSpace(anthropicStringField(block, "type")) == "image"
+}
+
 func anthropicProviderContentBlocks(message Message, thinkingEnabled bool) ([]map[string]any, error) {
 	blocks, err := anthropicContentBlocks(message)
 	if err != nil {