feat(realtime): complete fake channel reply flow

backend/internal/handler/api/v1/conversation_handler.go

@@ -4,12 +4,14 @@ import (
 	"context"
 	"errors"
 	"io"
+	"net"
 	"net/http"
 	"strconv"
 	"strings"
 
 	"github.com/gin-gonic/gin"
 
+	"github.com/gochat/gochat/internal/llm"
 	"github.com/gochat/gochat/internal/model"
 	"github.com/gochat/gochat/internal/service"
 	"github.com/gochat/gochat/pkg/pagination"
@@ -1055,6 +1057,29 @@ func handleServiceError(c *gin.Context, err error) {
 		return
 	}
 	errMsg := err.Error()
+	if errors.Is(err, llm.ErrProviderNotConfigured) {
+		response.AbortWithStatusError(c, http.StatusServiceUnavailable, response.ErrCopilotNotConfigured, errMsg)
+		return
+	}
+	var providerErr *llm.APIError
+	if errors.As(err, &providerErr) {
+		switch providerErr.StatusCode {
+		case http.StatusUnauthorized, http.StatusForbidden:
+			response.AbortWithStatusError(c, http.StatusBadGateway, response.ErrCopilotProviderAuth, "Copilot provider authentication failed")
+		case http.StatusNotFound:
+			response.AbortWithStatusError(c, http.StatusBadGateway, response.ErrCopilotModelNotFound, "Copilot provider endpoint or model was not found")
+		case http.StatusTooManyRequests:
+			response.AbortWithStatusError(c, http.StatusTooManyRequests, response.ErrCopilotProviderRateLimited, "Copilot provider rate limit exceeded")
+		default:
+			response.AbortWithStatusError(c, http.StatusBadGateway, response.ErrCopilotProviderUnreachable, "Copilot provider request failed")
+		}
+		return
+	}
+	var networkErr net.Error
+	if errors.Is(err, context.DeadlineExceeded) || (errors.As(err, &networkErr) && networkErr.Timeout()) {
+		response.AbortWithStatusError(c, http.StatusGatewayTimeout, response.ErrCopilotProviderTimeout, "Copilot provider request timed out")
+		return
+	}
 	lower := strings.ToLower(errMsg)
 	if strings.Contains(lower, "not found") || strings.Contains(lower, "record not found") {
 		response.AbortWithStatusError(c, http.StatusNotFound, response.ErrNotFound, errMsg)