diff --git a/model/ai_service.go b/model/ai_service.go
index f094efe..31f7964 100644
--- a/model/ai_service.go
+++ b/model/ai_service.go
@@ -6,6 +6,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"strings"
 	"time"
@@ -56,6 +57,13 @@ func (s *sseAIService) QueryCommandStream(
 	defer resp.Body.Close()
 
 	if resp.StatusCode != http.StatusOK {
+		body, readErr := io.ReadAll(resp.Body)
+		if readErr == nil {
+			var errResp errorResponse
+			if jsonErr := json.Unmarshal(body, &errResp); jsonErr == nil && errResp.ErrorMessage != "" {
+				return fmt.Errorf("%s", errResp.ErrorMessage)
+			}
+		}
 		return fmt.Errorf("server returned status %d", resp.StatusCode)
 	}
 
diff --git a/model/ai_service_test.go b/model/ai_service_test.go
new file mode 100644
index 0000000..7879557
--- /dev/null
+++ b/model/ai_service_test.go
@@ -0,0 +1,92 @@
+package model
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestQueryCommandStream_ErrorResponseBody(t *testing.T) {
+	tests := []struct {
+		name           string
+		statusCode     int
+		responseBody   interface{}
+		expectedErrMsg string
+	}{
+		{
+			name:       "quota exceeded returns error message from body",
+			statusCode: http.StatusTooManyRequests,
+			responseBody: errorResponse{
+				ErrorCode:    http.StatusTooManyRequests,
+				ErrorMessage: "monthly AI credit quota exceeded",
+			},
+			expectedErrMsg: "monthly AI credit quota exceeded",
+		},
+		{
+			name:       "unauthorized returns error message from body",
+			statusCode: http.StatusUnauthorized,
+			responseBody: errorResponse{
+				ErrorCode:    http.StatusUnauthorized,
+				ErrorMessage: "unauthorized",
+			},
+			expectedErrMsg: "unauthorized",
+		},
+		{
+			name:       "service unavailable returns error message from body",
+			statusCode: http.StatusServiceUnavailable,
+			responseBody: errorResponse{
+				ErrorCode:    http.StatusServiceUnavailable,
+				ErrorMessage: "AI service is not available",
+			},
+			expectedErrMsg: "AI service is not available",
+		},
+		{
+			name:           "non-JSON response falls back to status code",
+			statusCode:     http.StatusInternalServerError,
+			responseBody:   "not json",
+			expectedErrMsg: fmt.Sprintf("server returned status %d", http.StatusInternalServerError),
+		},
+		{
+			name:       "empty error message falls back to status code",
+			statusCode: http.StatusBadRequest,
+			responseBody: errorResponse{
+				ErrorCode:    http.StatusBadRequest,
+				ErrorMessage: "",
+			},
+			expectedErrMsg: fmt.Sprintf("server returned status %d", http.StatusBadRequest),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.Header().Set("Content-Type", "application/json")
+				w.WriteHeader(tt.statusCode)
+				if s, ok := tt.responseBody.(string); ok {
+					w.Write([]byte(s))
+				} else {
+					json.NewEncoder(w).Encode(tt.responseBody)
+				}
+			}))
+			defer server.Close()
+
+			svc := NewAIService()
+			err := svc.QueryCommandStream(
+				context.Background(),
+				CommandSuggestVariables{Shell: "bash", Os: "linux", Query: "test"},
+				Endpoint{APIEndpoint: server.URL, Token: "test-token"},
+				func(token string) {},
+			)
+
+			if err == nil {
+				t.Fatal("expected error, got nil")
+			}
+			if err.Error() != tt.expectedErrMsg {
+				t.Errorf("expected error %q, got %q", tt.expectedErrMsg, err.Error())
+			}
+		})
+	}
+}