diff --git a/backend/internal/protocol/manifest.go b/backend/internal/protocol/manifest.go
index 2aa438b1f..acc45bf56 100644
--- a/backend/internal/protocol/manifest.go
+++ b/backend/internal/protocol/manifest.go
@@ -963,7 +963,13 @@ func manifestRequestValues(request GenerationRequest) map[string]any {
 			userContent = append(userContent, map[string]any{"type": "audio_url", "audio_url": map[string]any{"url": val}})
 		}
 	}
-	messages := make([]any, 0, len(request.Messages)+1)
+	messages := make([]any, 0, len(request.Messages)+2)
+	// instructions 是统一的系统指令字段，但多数 OpenAI 系协议只映射 request.messages。
+	// 系统指令必须进入消息数组，否则会被静默丢弃；带独立 system 字段的协议（Claude、
+	// Gemini、Responses）在各自模板里过滤 system 角色，不会重复发送。
+	if instructions := strings.TrimSpace(request.Instructions); instructions != "" && !hasSystemMessage(request.Messages) {
+		messages = append(messages, map[string]any{"role": "system", "content": instructions})
+	}
 	for _, message := range request.Messages {
 		if strings.TrimSpace(message.Role) == "" || message.Content == nil {
 			continue
@@ -1028,6 +1034,15 @@ func manifestRequestValues(request GenerationRequest) map[string]any {
 	}
 }
 
+func hasSystemMessage(messages []Message) bool {
+	for _, message := range messages {
+		if strings.EqualFold(strings.TrimSpace(message.Role), "system") {
+			return true
+		}
+	}
+	return false
+}
+
 func requestAsManifestValue(value any) (any, error) {
 	encoded, err := json.Marshal(value)
 	if err != nil {
diff --git a/backend/internal/protocol/official_catalog_test.go b/backend/internal/protocol/official_catalog_test.go
index 168545f79..1d81c9ed8 100644
--- a/backend/internal/protocol/official_catalog_test.go
+++ b/backend/internal/protocol/official_catalog_test.go
@@ -480,6 +480,55 @@ func TestOfficialOpenAIVideosDeclaresAuthenticatedResultDownload(t *testing.T) {
 	}
 }
 
+// 系统指令必须真正到达上游：只映射 messages 的协议要收到 system 消息，
+// 有独立 system 字段的协议要用该字段且不能在消息数组里重复发送。
+func TestOfficialTextProtocolsDeliverInstructions(t *testing.T) {
+	tests := []struct {
+		name, packageName, providerID, messagesField, instructionField string
+	}{
+		{name: "openai-chat", packageName: "openai-chat-completions.yingce-plugin", providerID: "chat-completion", messagesField: "messages"},
+		{name: "deepseek", packageName: "deepseek-chat.yingce-plugin", providerID: "deepseek-chat", messagesField: "messages"},
+		{name: "atlascloud", packageName: "atlascloud-chat.yingce-plugin", providerID: "atlascloud-chat", messagesField: "messages"},
+		{name: "openai-responses", packageName: "openai-responses.yingce-plugin", providerID: "openai-response", messagesField: "input", instructionField: "instructions"},
+		{name: "anthropic", packageName: "anthropic-messages.yingce-plugin", providerID: "claude-api", messagesField: "messages", instructionField: "system"},
+		{name: "gemini", packageName: "google-gemini-generate-content.yingce-plugin", providerID: "gemini-generate-content", messagesField: "contents", instructionField: "systemInstruction"},
+	}
+	const instructions = "只输出一个 JSON 对象"
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			adapter := officialPackageAdapter(t, test.packageName, test.providerID)
+			spec, err := adapter.BuildCreate(context.Background(), RequestContext{Request: GenerationRequest{
+				Capability: CapabilityText, Model: "model-test", Prompt: "一句话故事", Instructions: instructions,
+			}})
+			if err != nil {
+				t.Fatal(err)
+			}
+			body := manifestTestBody(t, spec)
+			encodedMessages, err := json.Marshal(body[test.messagesField])
+			if err != nil {
+				t.Fatal(err)
+			}
+			carriesInstructions := strings.Contains(string(encodedMessages), instructions)
+			if test.instructionField == "" {
+				if !carriesInstructions {
+					t.Fatalf("%s dropped the system instruction: %s", test.providerID, encodedMessages)
+				}
+				return
+			}
+			if carriesInstructions {
+				t.Fatalf("%s duplicated the system instruction into %s: %s", test.providerID, test.messagesField, encodedMessages)
+			}
+			encodedInstruction, err := json.Marshal(body[test.instructionField])
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !strings.Contains(string(encodedInstruction), instructions) {
+				t.Fatalf("%s did not map the system instruction to %s: %s", test.providerID, test.instructionField, encodedInstruction)
+			}
+		})
+	}
+}
+
 func officialPackageAdapter(t *testing.T, packageName, providerID string) Adapter {
 	t.Helper()
 	data, err := os.ReadFile(filepath.Join("..", "..", "..", "plugin-packages", packageName))
diff --git a/plugin-packages/generate-catalog.mjs b/plugin-packages/generate-catalog.mjs
index a8e1c976d..a5b9d0668 100644
--- a/plugin-packages/generate-catalog.mjs
+++ b/plugin-packages/generate-catalog.mjs
@@ -112,7 +112,9 @@ add({
   id: "openai-responses", providerId: "openai-response", name: "OpenAI Responses", vendor: "OpenAI", capability: "text",
   baseUrl: "https://api.openai.com", auth: bearer, params: textParams,
   create: jsonCreate("/responses", {
-    model: ref("request.model"), input: ref("request.messages"), instructions: omit(ref("request.instructions")),
+    model: ref("request.model"),
+    input: filter(ref("request.messages"), "message", ne(ref("message.role"), "system")),
+    instructions: omit(ref("request.instructions")),
     temperature: omit(ref("request.providerOptions.openai-response.temperature")),
     top_p: omit(ref("request.providerOptions.openai-response.top_p")),
     max_output_tokens: omit(coalesce(ref("request.extra.max_output_tokens"), ref("request.providerOptions.openai-response.max_output_tokens"))),
@@ -156,7 +158,7 @@ add({
   id: "google-gemini-generate-content", providerId: "gemini-generate-content", name: "Google Gemini generateContent", vendor: "Google", capability: "text",
   baseUrl: "https://generativelanguage.googleapis.com", auth: { type: "google-api-key", field: "apiKey" }, params: textParams,
   create: jsonCreate("/v1beta/models/{{model}}:generateContent", {
-    contents: map(ref("request.messages"), "message", {
+    contents: map(filter(ref("request.messages"), "message", ne(ref("message.role"), "system")), "message", {
       role: conditional(eq(ref("message.role"), "assistant"), "model", "user"),
       parts: [{ text: ref("message.content") }]
     }),
diff --git a/plugin-packages/google-gemini-generate-content.yingce-plugin b/plugin-packages/google-gemini-generate-content.yingce-plugin
index afccae8ff..00aedd4dc 100644
Binary files a/plugin-packages/google-gemini-generate-content.yingce-plugin and b/plugin-packages/google-gemini-generate-content.yingce-plugin differ
diff --git a/plugin-packages/openai-responses.yingce-plugin b/plugin-packages/openai-responses.yingce-plugin
index f0ee2178b..42b785636 100644
Binary files a/plugin-packages/openai-responses.yingce-plugin and b/plugin-packages/openai-responses.yingce-plugin differ