Add AMP fallback proxy and shared Gemini normalization

- add fallback handler that forwards Amp provider requests to ampcode.com when the provider isn’t configured locally
- wrap AMP provider routes with the fallback so requests always have a handler
- share Gemini thinking model normalization helper between core handlers and AMP fallback

internal/api/modules/amp/fallback_handlers.go

@@ -0,0 +1,105 @@
+package amp
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http/httputil"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+	"github.com/router-for-me/CLIProxyAPI/v6/internal/util"
+	log "github.com/sirupsen/logrus"
+)
+
+// FallbackHandler wraps a standard handler with fallback logic to ampcode.com
+// when the model's provider is not available in CLIProxyAPI
+type FallbackHandler struct {
+	getProxy func() *httputil.ReverseProxy
+}
+
+// NewFallbackHandler creates a new fallback handler wrapper
+// The getProxy function allows lazy evaluation of the proxy (useful when proxy is created after routes)
+func NewFallbackHandler(getProxy func() *httputil.ReverseProxy) *FallbackHandler {
+	return &FallbackHandler{
+		getProxy: getProxy,
+	}
+}
+
+// WrapHandler wraps a gin.HandlerFunc with fallback logic
+// If the model's provider is not configured in CLIProxyAPI, it forwards to ampcode.com
+func (fh *FallbackHandler) WrapHandler(handler gin.HandlerFunc) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		// Read the request body to extract the model name
+		bodyBytes, err := io.ReadAll(c.Request.Body)
+		if err != nil {
+			log.Errorf("amp fallback: failed to read request body: %v", err)
+			handler(c)
+			return
+		}
+
+		// Restore the body for the handler to read
+		c.Request.Body = io.NopCloser(bytes.NewReader(bodyBytes))
+
+		// Try to extract model from request body or URL path (for Gemini)
+		modelName := extractModelFromRequest(bodyBytes, c)
+		if modelName == "" {
+			// Can't determine model, proceed with normal handler
+			handler(c)
+			return
+		}
+
+		// Normalize model (handles Gemini thinking suffixes)
+		normalizedModel, _ := util.NormalizeGeminiThinkingModel(modelName)
+
+		// Check if we have providers for this model
+		providers := util.GetProviderName(normalizedModel)
+
+		if len(providers) == 0 {
+			// No providers configured - check if we have a proxy for fallback
+			proxy := fh.getProxy()
+			if proxy != nil {
+				// Fallback to ampcode.com
+				log.Infof("amp fallback: model %s has no configured provider, forwarding to ampcode.com", modelName)
+
+				// Restore body again for the proxy
+				c.Request.Body = io.NopCloser(bytes.NewReader(bodyBytes))
+
+				// Forward to ampcode.com
+				proxy.ServeHTTP(c.Writer, c.Request)
+				return
+			}
+
+			// No proxy available, let the normal handler return the error
+			log.Debugf("amp fallback: model %s has no configured provider and no proxy available", modelName)
+		}
+
+		// Providers available or no proxy for fallback, restore body and use normal handler
+		c.Request.Body = io.NopCloser(bytes.NewReader(bodyBytes))
+		handler(c)
+	}
+}
+
+// extractModelFromRequest attempts to extract the model name from various request formats
+func extractModelFromRequest(body []byte, c *gin.Context) string {
+	// First try to parse from JSON body (OpenAI, Claude, etc.)
+	var payload map[string]interface{}
+	if err := json.Unmarshal(body, &payload); err == nil {
+		// Check common model field names
+		if model, ok := payload["model"].(string); ok {
+			return model
+		}
+	}
+
+	// For Gemini requests, model is in the URL path: /models/{model}:generateContent
+	// Extract from :action parameter (e.g., "gemini-pro:generateContent")
+	if action := c.Param("action"); action != "" {
+		// Split by colon to get model name (e.g., "gemini-pro:generateContent" -> "gemini-pro")
+		parts := strings.Split(action, ":")
+		if len(parts) > 0 && parts[0] != "" {
+			return parts[0]
+		}
+	}
+
+	return ""
+}

internal/api/modules/amp/routes.go

@@ -2,6 +2,7 @@ package amp
 
 import (
 	"net"
+	"net/http/httputil"
 	"strings"
 
 	"github.com/gin-gonic/gin"
@@ -112,6 +113,12 @@ func (m *AmpModule) registerProviderAliases(engine *gin.Engine, baseHandler *han
 	claudeCodeHandlers := claude.NewClaudeCodeAPIHandler(baseHandler)
 	openaiResponsesHandlers := openai.NewOpenAIResponsesAPIHandler(baseHandler)
 
+	// Create fallback handler wrapper that forwards to ampcode.com when provider not found
+	// Uses lazy evaluation to access proxy (which is created after routes are registered)
+	fallbackHandler := NewFallbackHandler(func() *httputil.ReverseProxy {
+		return m.proxy
+	})
+
 	// Provider-specific routes under /api/provider/:provider
 	ampProviders := engine.Group("/api/provider")
 	if auth != nil {
@@ -136,31 +143,33 @@ func (m *AmpModule) registerProviderAliases(engine *gin.Engine, baseHandler *han
 	}
 
 	// Root-level routes (for providers that omit /v1, like groq/cerebras)
-	provider.GET("/models", ampModelsHandler)
-	provider.POST("/chat/completions", openaiHandlers.ChatCompletions)
-	provider.POST("/completions", openaiHandlers.Completions)
-	provider.POST("/responses", openaiResponsesHandlers.Responses)
+	// Wrap handlers with fallback logic to forward to ampcode.com when provider not found
+	provider.GET("/models", ampModelsHandler) // Models endpoint doesn't need fallback (no body to check)
+	provider.POST("/chat/completions", fallbackHandler.WrapHandler(openaiHandlers.ChatCompletions))
+	provider.POST("/completions", fallbackHandler.WrapHandler(openaiHandlers.Completions))
+	provider.POST("/responses", fallbackHandler.WrapHandler(openaiResponsesHandlers.Responses))
 
 	// /v1 routes (OpenAI/Claude-compatible endpoints)
 	v1Amp := provider.Group("/v1")
 	{
-		v1Amp.GET("/models", ampModelsHandler)
+		v1Amp.GET("/models", ampModelsHandler) // Models endpoint doesn't need fallback
 
-		// OpenAI-compatible endpoints
-		v1Amp.POST("/chat/completions", openaiHandlers.ChatCompletions)
-		v1Amp.POST("/completions", openaiHandlers.Completions)
-		v1Amp.POST("/responses", openaiResponsesHandlers.Responses)
+		// OpenAI-compatible endpoints with fallback
+		v1Amp.POST("/chat/completions", fallbackHandler.WrapHandler(openaiHandlers.ChatCompletions))
+		v1Amp.POST("/completions", fallbackHandler.WrapHandler(openaiHandlers.Completions))
+		v1Amp.POST("/responses", fallbackHandler.WrapHandler(openaiResponsesHandlers.Responses))
 
-		// Claude/Anthropic-compatible endpoints
-		v1Amp.POST("/messages", claudeCodeHandlers.ClaudeMessages)
-		v1Amp.POST("/messages/count_tokens", claudeCodeHandlers.ClaudeCountTokens)
+		// Claude/Anthropic-compatible endpoints with fallback
+		v1Amp.POST("/messages", fallbackHandler.WrapHandler(claudeCodeHandlers.ClaudeMessages))
+		v1Amp.POST("/messages/count_tokens", fallbackHandler.WrapHandler(claudeCodeHandlers.ClaudeCountTokens))
 	}
 
 	// /v1beta routes (Gemini native API)
+	// Note: Gemini handler extracts model from URL path, so fallback logic needs special handling
 	v1betaAmp := provider.Group("/v1beta")
 	{
 		v1betaAmp.GET("/models", geminiHandlers.GeminiModels)
-		v1betaAmp.POST("/models/:action", geminiHandlers.GeminiHandler)
+		v1betaAmp.POST("/models/:action", fallbackHandler.WrapHandler(geminiHandlers.GeminiHandler))
 		v1betaAmp.GET("/models/:action", geminiHandlers.GeminiGetHandler)
 	}
 }

internal/util/gemini_thinking.go

@@ -62,6 +62,23 @@ func ParseGeminiThinkingSuffix(model string) (string, *int, *bool, bool) {
 	return base, &budgetValue, nil, true
 }
 
+func NormalizeGeminiThinkingModel(modelName string) (string, map[string]any) {
+	baseModel, budget, include, matched := ParseGeminiThinkingSuffix(modelName)
+	if !matched {
+		return baseModel, nil
+	}
+	metadata := map[string]any{
+		GeminiOriginalModelMetadataKey: modelName,
+	}
+	if budget != nil {
+		metadata[GeminiThinkingBudgetMetadataKey] = *budget
+	}
+	if include != nil {
+		metadata[GeminiIncludeThoughtsMetadataKey] = *include
+	}
+	return baseModel, metadata
+}
+
 func ApplyGeminiThinkingConfig(body []byte, budget *int, includeThoughts *bool) []byte {
 	if budget == nil && includeThoughts == nil {
 		return body

sdk/api/handlers/handlers.go

@@ -359,20 +359,7 @@ func cloneBytes(src []byte) []byte {
 }
 
 func normalizeModelMetadata(modelName string) (string, map[string]any) {
-	baseModel, budget, include, matched := util.ParseGeminiThinkingSuffix(modelName)
-	if !matched {
-		return baseModel, nil
-	}
-	metadata := map[string]any{
-		util.GeminiOriginalModelMetadataKey: modelName,
-	}
-	if budget != nil {
-		metadata[util.GeminiThinkingBudgetMetadataKey] = *budget
-	}
-	if include != nil {
-		metadata[util.GeminiIncludeThoughtsMetadataKey] = *include
-	}
-	return baseModel, metadata
+	return util.NormalizeGeminiThinkingModel(modelName)
 }
 
 func cloneMetadata(src map[string]any) map[string]any {