From ea084e775e0b81efd948ee9e413f530817b34542 Mon Sep 17 00:00:00 2001
From: Seefs <i@seefs.me>
Date: Sat, 20 Sep 2025 00:22:54 +0800
Subject: [PATCH 1/2] fix: claude system prompt overwrite

---
 relay/claude_handler.go | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/relay/claude_handler.go b/relay/claude_handler.go
index dbdc6ee1..3c9272b6 100644
--- a/relay/claude_handler.go
+++ b/relay/claude_handler.go
@@ -6,6 +6,7 @@ import (
 	"io"
 	"net/http"
 	"one-api/common"
+	"one-api/constant"
 	"one-api/dto"
 	relaycommon "one-api/relay/common"
 	"one-api/relay/helper"
@@ -69,6 +70,31 @@ func ClaudeHelper(c *gin.Context, info *relaycommon.RelayInfo) (newAPIError *typ
 		info.UpstreamModelName = request.Model
 	}
 
+	if info.ChannelSetting.SystemPrompt != "" && info.ChannelSetting.SystemPromptOverride {
+		if request.System == nil {
+			request.SetStringSystem(info.ChannelSetting.SystemPrompt)
+		} else if info.ChannelSetting.SystemPromptOverride {
+			common.SetContextKey(c, constant.ContextKeySystemPromptOverride, true)
+			if request.IsStringSystem() {
+				existing := strings.TrimSpace(request.GetStringSystem())
+				if existing == "" {
+					request.SetStringSystem(info.ChannelSetting.SystemPrompt)
+				} else {
+					request.SetStringSystem(info.ChannelSetting.SystemPrompt + "\n" + existing)
+				}
+			} else {
+				systemContents := request.ParseSystem()
+				newSystem := dto.ClaudeMediaMessage{Type: dto.ContentTypeText}
+				newSystem.SetText(info.ChannelSetting.SystemPrompt)
+				if len(systemContents) == 0 {
+					request.System = []dto.ClaudeMediaMessage{newSystem}
+				} else {
+					request.System = append([]dto.ClaudeMediaMessage{newSystem}, systemContents...)
+				}
+			}
+		}
+	}
+
 	var requestBody io.Reader
 	if model_setting.GetGlobalSettings().PassThroughRequestEnabled || info.ChannelSetting.PassThroughBodyEnabled {
 		body, err := common.GetRequestBody(c)

From 8e7301b79ad16c6ea97104a3b37edb0f46ff4bd2 Mon Sep 17 00:00:00 2001
From: Seefs <i@seefs.me>
Date: Sat, 20 Sep 2025 13:38:44 +0800
Subject: [PATCH 2/2] fix: gemini system prompt overwrite

---
 relay/claude_handler.go |  2 +-
 relay/gemini_handler.go | 27 +++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/relay/claude_handler.go b/relay/claude_handler.go
index 3c9272b6..59d12abe 100644
--- a/relay/claude_handler.go
+++ b/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 {
diff --git a/relay/gemini_handler.go b/relay/gemini_handler.go
index 0252d657..1410da60 100644
--- a/relay/gemini_handler.go
+++ b/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