fix(amp): pass mapped model to gemini bridge via context

Gemini handler extracts model from URL path, not JSON body, so
rewriting the request body alone wasn't sufficient for model mapping.

- Add MappedModelContextKey constant for context passing
- Update routes.go to use NewFallbackHandlerWithMapper
- Add check for valid mapping before routing to local handler
- Add tests for gemini bridge model mapping

internal/api/modules/amp/fallback_handlers.go

@@ -28,6 +28,9 @@ const (
 	RouteTypeNoProvider AmpRouteType = "NO_PROVIDER"
 )
 
+// MappedModelContextKey is the Gin context key for passing mapped model names.
+const MappedModelContextKey = "mapped_model"
+
 // logAmpRouting logs the routing decision for an Amp request with structured fields
 func logAmpRouting(routeType AmpRouteType, requestedModel, resolvedModel, provider, path string) {
 	fields := log.Fields{
@@ -141,6 +144,8 @@ func (fh *FallbackHandler) WrapHandler(handler gin.HandlerFunc) gin.HandlerFunc
 					// Mapping found - rewrite the model in request body
 					bodyBytes = rewriteModelInRequest(bodyBytes, mappedModel)
 					c.Request.Body = io.NopCloser(bytes.NewReader(bodyBytes))
+					// Store mapped model in context for handlers that check it (like gemini bridge)
+					c.Set(MappedModelContextKey, mappedModel)
 					resolvedModel = mappedModel
 					usedMapping = true
 

internal/api/modules/amp/gemini_bridge.go

@@ -26,6 +26,18 @@ func createGeminiBridgeHandler(geminiHandler *gemini.GeminiAPIHandler) gin.Handl
 			// Extract everything after "/models/"
 			actionPart := path[idx+8:] // Skip "/models/"
 
+			// Check if model was mapped by FallbackHandler
+			if mappedModel, exists := c.Get(MappedModelContextKey); exists {
+				if strModel, ok := mappedModel.(string); ok && strModel != "" {
+					// Replace the model part in the action
+					// actionPart is like "model-name:method"
+					if colonIdx := strings.Index(actionPart, ":"); colonIdx > 0 {
+						method := actionPart[colonIdx:] // ":method"
+						actionPart = strModel + method
+					}
+				}
+			}
+
 			// Set this as the :action parameter that the Gemini handler expects
 			c.Params = append(c.Params, gin.Param{
 				Key:   "action",

internal/api/modules/amp/gemini_bridge_test.go

@@ -0,0 +1,120 @@
+package amp
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/router-for-me/CLIProxyAPI/v6/sdk/api/handlers"
+	"github.com/router-for-me/CLIProxyAPI/v6/sdk/api/handlers/gemini"
+)
+
+func TestCreateGeminiBridgeHandler_ActionParameterExtraction(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	tests := []struct {
+		name           string
+		path           string
+		mappedModel    string // empty string means no mapping
+		expectedAction string
+	}{
+		{
+			name:           "no_mapping_uses_url_model",
+			path:           "/publishers/google/models/gemini-pro:generateContent",
+			mappedModel:    "",
+			expectedAction: "gemini-pro:generateContent",
+		},
+		{
+			name:           "mapped_model_replaces_url_model",
+			path:           "/publishers/google/models/gemini-exp:generateContent",
+			mappedModel:    "gemini-2.0-flash",
+			expectedAction: "gemini-2.0-flash:generateContent",
+		},
+		{
+			name:           "mapping_preserves_method",
+			path:           "/publishers/google/models/gemini-2.5-preview:streamGenerateContent",
+			mappedModel:    "gemini-flash",
+			expectedAction: "gemini-flash:streamGenerateContent",
+		},
+		{
+			name:           "empty_mapped_model_ignored",
+			path:           "/publishers/google/models/gemini-pro:generateContent",
+			mappedModel:    "",
+			expectedAction: "gemini-pro:generateContent",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var capturedAction string
+
+			mockGeminiHandler := func(c *gin.Context) {
+				capturedAction = c.Param("action")
+				c.JSON(http.StatusOK, gin.H{"captured": capturedAction})
+			}
+
+			// Mirror the bridge logic from gemini_bridge.go
+			bridgeHandler := func(c *gin.Context) {
+				path := c.Param("path")
+				if idx := strings.Index(path, "/models/"); idx >= 0 {
+					actionPart := path[idx+8:]
+
+					if mappedModel, exists := c.Get(MappedModelContextKey); exists {
+						if strModel, ok := mappedModel.(string); ok && strModel != "" {
+							if colonIdx := strings.Index(actionPart, ":"); colonIdx > 0 {
+								method := actionPart[colonIdx:]
+								actionPart = strModel + method
+							}
+						}
+					}
+
+					c.Params = append(c.Params, gin.Param{Key: "action", Value: actionPart})
+					mockGeminiHandler(c)
+					return
+				}
+				c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid path"})
+			}
+
+			r := gin.New()
+			if tt.mappedModel != "" {
+				r.Use(func(c *gin.Context) {
+					c.Set(MappedModelContextKey, tt.mappedModel)
+					c.Next()
+				})
+			}
+			r.POST("/api/provider/google/v1beta1/*path", bridgeHandler)
+
+			req := httptest.NewRequest(http.MethodPost, "/api/provider/google/v1beta1"+tt.path, nil)
+			w := httptest.NewRecorder()
+			r.ServeHTTP(w, req)
+
+			if w.Code != http.StatusOK {
+				t.Fatalf("Expected status 200, got %d", w.Code)
+			}
+			if capturedAction != tt.expectedAction {
+				t.Errorf("Expected action '%s', got '%s'", tt.expectedAction, capturedAction)
+			}
+		})
+	}
+}
+
+func TestCreateGeminiBridgeHandler_InvalidPath(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	base := &handlers.BaseAPIHandler{}
+	geminiHandlers := gemini.NewGeminiAPIHandler(base)
+	bridgeHandler := createGeminiBridgeHandler(geminiHandlers)
+
+	r := gin.New()
+	r.POST("/api/provider/google/v1beta1/*path", bridgeHandler)
+
+	req := httptest.NewRequest(http.MethodPost, "/api/provider/google/v1beta1/invalid/path", nil)
+	w := httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+
+	if w.Code != http.StatusBadRequest {
+		t.Errorf("Expected status 400 for invalid path, got %d", w.Code)
+	}
+}

internal/api/modules/amp/routes.go

@@ -170,9 +170,9 @@ func (m *AmpModule) registerManagementRoutes(engine *gin.Engine, baseHandler *ha
 	// If no local OAuth is available, falls back to ampcode.com proxy.
 	geminiHandlers := gemini.NewGeminiAPIHandler(baseHandler)
 	geminiBridge := createGeminiBridgeHandler(geminiHandlers)
-	geminiV1Beta1Fallback := NewFallbackHandler(func() *httputil.ReverseProxy {
+	geminiV1Beta1Fallback := NewFallbackHandlerWithMapper(func() *httputil.ReverseProxy {
 		return m.getProxy()
-	})
+	}, m.modelMapper)
 	geminiV1Beta1Handler := geminiV1Beta1Fallback.WrapHandler(geminiBridge)
 
 	// Route POST model calls through Gemini bridge when a local provider exists, otherwise proxy.
@@ -187,8 +187,18 @@ func (m *AmpModule) registerManagementRoutes(engine *gin.Engine, baseHandler *ha
 				}
 				if modelPart != "" {
 					normalized, _ := util.NormalizeGeminiThinkingModel(modelPart)
-					// Only handle locally when we have a provider; otherwise fall back to proxy
+					// Only handle locally when we have a provider or a valid mapping; otherwise fall back to proxy
+					hasProvider := false
 					if providers := util.GetProviderName(normalized); len(providers) > 0 {
+						hasProvider = true
+					} else if m.modelMapper != nil {
+						// Check if mapped model has provider (MapModel returns target only if it has providers)
+						if mapped := m.modelMapper.MapModel(normalized); mapped != "" {
+							hasProvider = true
+						}
+					}
+
+					if hasProvider {
 						geminiV1Beta1Handler(c)
 						return
 					}