fix: gemini system prompt overwrite

relay/claude_handler.go

@@ -70,7 +70,7 @@ func ClaudeHelper(c *gin.Context, info *relaycommon.RelayInfo) (newAPIError *typ
 		info.UpstreamModelName = request.Model
 	}
 
-	if info.ChannelSetting.SystemPrompt != "" && info.ChannelSetting.SystemPromptOverride {
+	if info.ChannelSetting.SystemPrompt != "" {
 		if request.System == nil {
 			request.SetStringSystem(info.ChannelSetting.SystemPrompt)
 		} else if info.ChannelSetting.SystemPromptOverride {

relay/gemini_handler.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"net/http"
 	"one-api/common"
+	"one-api/constant"
 	"one-api/dto"
 	"one-api/logger"
 	"one-api/relay/channel/gemini"
@@ -94,6 +95,32 @@ func GeminiHelper(c *gin.Context, info *relaycommon.RelayInfo) (newAPIError *typ
 
 	adaptor.Init(info)
 
+	if info.ChannelSetting.SystemPrompt != "" {
+		if request.SystemInstructions == nil {
+			request.SystemInstructions = &dto.GeminiChatContent{
+				Parts: []dto.GeminiPart{
+					{Text: info.ChannelSetting.SystemPrompt},
+				},
+			}
+		} else if len(request.SystemInstructions.Parts) == 0 {
+			request.SystemInstructions.Parts = []dto.GeminiPart{{Text: info.ChannelSetting.SystemPrompt}}
+		} else if info.ChannelSetting.SystemPromptOverride {
+			common.SetContextKey(c, constant.ContextKeySystemPromptOverride, true)
+			merged := false
+			for i := range request.SystemInstructions.Parts {
+				if request.SystemInstructions.Parts[i].Text == "" {
+					continue
+				}
+				request.SystemInstructions.Parts[i].Text = info.ChannelSetting.SystemPrompt + "\n" + request.SystemInstructions.Parts[i].Text
+				merged = true
+				break
+			}
+			if !merged {
+				request.SystemInstructions.Parts = append([]dto.GeminiPart{{Text: info.ChannelSetting.SystemPrompt}}, request.SystemInstructions.Parts...)
+			}
+		}
+	}
+
 	// Clean up empty system instruction
 	if request.SystemInstructions != nil {
 		hasContent := false