diff --git a/backend/internal/service/gateway_service.go b/backend/internal/service/gateway_service.go
index 0256ac75e..274faeea7 100644
--- a/backend/internal/service/gateway_service.go
+++ b/backend/internal/service/gateway_service.go
@@ -2675,6 +2675,19 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 		return nil, fmt.Errorf("parse request: empty request")
 	}
 
+	// 防止非 Anthropic/Antigravity 平台的账号被错误地通过 Claude 端点转发。
+	// 例如 OpenAI 账号的 token 发到 Anthropic API 会导致 401 并触发 failover 禁用账号。
+	if account.Platform != PlatformAnthropic && account.Platform != PlatformAntigravity {
+		c.JSON(http.StatusBadRequest, gin.H{
+			"type": "error",
+			"error": gin.H{
+				"type":    "invalid_request_error",
+				"message": fmt.Sprintf("Account platform %q is not compatible with /v1/messages endpoint", account.Platform),
+			},
+		})
+		return nil, fmt.Errorf("platform mismatch: account %d platform=%s not compatible with claude endpoint", account.ID, account.Platform)
+	}
+
 	body := parsed.Body
 	reqModel := parsed.Model
 	reqStream := parsed.Stream
diff --git a/backend/internal/service/openai_codex_transform.go b/backend/internal/service/openai_codex_transform.go
index d28e13abc..25f75131a 100644
--- a/backend/internal/service/openai_codex_transform.go
+++ b/backend/internal/service/openai_codex_transform.go
@@ -135,8 +135,15 @@ func applyCodexOAuthTransform(reqBody map[string]any, isCodexCLI bool) codexTran
 	}
 
 	// 续链场景保留 item_reference 与 id，避免 call_id 上下文丢失。
+	// 但 store=false 时上游不会持久化 item，引用必然失败，
+	// 因此即使续链也必须移除 item_reference 并清理 id 字段。
+	storeFalse := false
+	if v, ok := reqBody["store"].(bool); ok && !v {
+		storeFalse = true
+	}
 	if input, ok := reqBody["input"].([]any); ok {
-		input = filterCodexInput(input, needsToolContinuation)
+		preserveRefs := needsToolContinuation && !storeFalse
+		input = filterCodexInput(input, preserveRefs)
 		reqBody["input"] = input
 		result.Modified = true
 	}
diff --git a/backend/internal/service/openai_codex_transform_test.go b/backend/internal/service/openai_codex_transform_test.go
index 0987c5090..53d0211be 100644
--- a/backend/internal/service/openai_codex_transform_test.go
+++ b/backend/internal/service/openai_codex_transform_test.go
@@ -11,7 +11,8 @@ import (
 )
 
 func TestApplyCodexOAuthTransform_ToolContinuationPreservesInput(t *testing.T) {
-	// 续链场景：保留 item_reference 与 id，但不再强制 store=true。
+	// 续链场景 + store=false：item_reference 被移除（上游不持久化，引用必然 404），
+	// function_call_output 保留但 id 被清理，call_id 保留用于工具调用关联。
 	setupCodexCache(t)
 
 	reqBody := map[string]any{
@@ -25,25 +26,23 @@ func TestApplyCodexOAuthTransform_ToolContinuationPreservesInput(t *testing.T) {
 
 	applyCodexOAuthTransform(reqBody, false)
 
-	// 未显式设置 store=true，默认为 false。
+	// store 强制为 false（OAuth 账号）。
 	store, ok := reqBody["store"].(bool)
 	require.True(t, ok)
 	require.False(t, store)
 
 	input, ok := reqBody["input"].([]any)
 	require.True(t, ok)
-	require.Len(t, input, 2)
+	// item_reference 被移除，只剩 function_call_output。
+	require.Len(t, input, 1)
 
-	// 校验 input[0] 为 map，避免断言失败导致测试中断。
 	first, ok := input[0].(map[string]any)
 	require.True(t, ok)
-	require.Equal(t, "item_reference", first["type"])
-	require.Equal(t, "ref1", first["id"])
-
-	// 校验 input[1] 为 map，确保后续字段断言安全。
-	second, ok := input[1].(map[string]any)
-	require.True(t, ok)
-	require.Equal(t, "o1", second["id"])
+	require.Equal(t, "function_call_output", first["type"])
+	require.Equal(t, "call_1", first["call_id"])
+	// id 被清理（store=false 下无意义）。
+	_, hasID := first["id"]
+	require.False(t, hasID)
 }
 
 func TestApplyCodexOAuthTransform_ExplicitStoreFalsePreserved(t *testing.T) {
diff --git a/backend/internal/service/openai_gateway_service.go b/backend/internal/service/openai_gateway_service.go
index 52800f077..aa3df23de 100644
--- a/backend/internal/service/openai_gateway_service.go
+++ b/backend/internal/service/openai_gateway_service.go
@@ -1163,6 +1163,16 @@ func (s *OpenAIGatewayService) handleErrorResponse(ctx context.Context, resp *ht
 	var statusCode int
 
 	switch resp.StatusCode {
+	case 400, 404, 409, 422:
+		// Client errors: pass through upstream status and message so the caller
+		// can act on the real problem (e.g. referencing a non-persisted response ID).
+		statusCode = resp.StatusCode
+		errType = "invalid_request_error"
+		if upstreamMsg != "" {
+			errMsg = upstreamMsg
+		} else {
+			errMsg = "Upstream request rejected"
+		}
 	case 401:
 		statusCode = http.StatusBadGateway
 		errType = "upstream_error"