fix: gpt->claude格式转换对齐effort映射和fast

backend/internal/service/openai_gateway_messages.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"github.com/Wei-Shaw/sub2api/internal/pkg/apicompat"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/claude"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/logger"
 	"github.com/Wei-Shaw/sub2api/internal/util/responseheaders"
 	"github.com/gin-gonic/gin"
@@ -46,6 +47,11 @@ func (s *OpenAIGatewayService) ForwardAsAnthropic(
 		return nil, fmt.Errorf("convert anthropic to responses: %w", err)
 	}
 
+	// 2b. Handle BetaFastMode → service_tier: "priority"
+	if containsBetaToken(c.GetHeader("anthropic-beta"), claude.BetaFastMode) {
+		responsesReq.ServiceTier = "priority"
+	}
+
 	// 3. Model mapping
 	mappedModel := account.GetMappedModel(originalModel)
 	// 分组级降级：账号未映射时使用分组默认映射模型
@@ -94,6 +100,12 @@ func (s *OpenAIGatewayService) ForwardAsAnthropic(
 		return nil, fmt.Errorf("build upstream request: %w", err)
 	}
 
+	// Override session_id with a deterministic UUID derived from the sticky
+	// session key (buildUpstreamRequest may have set it to the raw value).
+	if promptCacheKey != "" {
+		upstreamReq.Header.Set("session_id", generateSessionUUID(promptCacheKey))
+	}
+
 	// 7. Send request
 	proxyURL := ""
 	if account.Proxy != nil {
@@ -160,6 +172,18 @@ func (s *OpenAIGatewayService) ForwardAsAnthropic(
 		result, handleErr = s.handleAnthropicNonStreamingResponse(resp, c, originalModel, mappedModel, startTime)
 	}
 
+	// Propagate ServiceTier and ReasoningEffort to result for billing
+	if handleErr == nil && result != nil {
+		if responsesReq.ServiceTier != "" {
+			st := responsesReq.ServiceTier
+			result.ServiceTier = &st
+		}
+		if responsesReq.Reasoning != nil && responsesReq.Reasoning.Effort != "" {
+			re := responsesReq.Reasoning.Effort
+			result.ReasoningEffort = &re
+		}
+	}
+
 	// Extract and save Codex usage snapshot from response headers (for OAuth accounts)
 	if handleErr == nil && account.Type == AccountTypeOAuth {
 		if snapshot := ParseCodexRateLimitHeaders(resp.Header); snapshot != nil {