Refactors AMP model mapping and error handling

Improves AMP request handling by consolidating model mapping logic into a helper function for better readability and maintainability.

Enhances error handling for premature client connection closures during reverse proxy operations by explicitly acknowledging and swallowing the ErrAbortHandler panic, preventing noisy stack traces.

Removes unused method `findProviderViaOAuthAlias` from the `DefaultModelMapper`.

internal/api/modules/amp/fallback_handlers.go

@@ -122,7 +122,11 @@ func (fh *FallbackHandler) SetModelMapper(mapper ModelMapper) {
 // 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) {
-		// Swallow ErrAbortHandler panics from ReverseProxy copyResponse to avoid noisy stack traces
+		// Swallow ErrAbortHandler panics from ReverseProxy to avoid noisy stack traces.
+		// ReverseProxy raises this panic when the client connection is closed prematurely
+		// (e.g., user cancels request, network disconnect) or when ServeHTTP is called
+		// with a ResponseWriter that doesn't implement http.CloseNotifier.
+		// This is an expected error condition, not a bug, so we handle it gracefully.
 		defer func() {
 			if rec := recover(); rec != nil {
 				if err, ok := rec.(error); ok && errors.Is(err, http.ErrAbortHandler) {
@@ -219,17 +223,10 @@ func (fh *FallbackHandler) WrapHandler(handler gin.HandlerFunc) gin.HandlerFunc
 		usedMapping := false
 		var providers []string
 
-		// Check if model mappings should be forced ahead of local API keys
+		// Helper to apply model mapping and update state
-		forceMappings := fh.forceModelMappings != nil && fh.forceModelMappings()
+		applyMapping := func(mappedModels []string, mappedProviders []string) {
-
-		if forceMappings {
-			// FORCE MODE: Check model mappings FIRST (takes precedence over local API keys)
-			// This allows users to route Amp requests to their preferred OAuth providers
-			if mappedModels, mappedProviders := resolveMappedModels(); len(mappedModels) > 0 {
-				// Mapping found and provider available - rewrite the model in request body
 			bodyBytes = rewriteModelInRequest(bodyBytes, mappedModels[0])
 			c.Request.Body = io.NopCloser(bytes.NewReader(bodyBytes))
-				// Store mapped model and fallbacks in context for handlers
 			c.Set(string(ctxkeys.MappedModel), mappedModels[0])
 			if len(mappedModels) > 1 {
 				c.Set(string(ctxkeys.FallbackModels), mappedModels[1:])
@@ -239,6 +236,16 @@ func (fh *FallbackHandler) WrapHandler(handler gin.HandlerFunc) gin.HandlerFunc
 			providers = mappedProviders
 		}
 
+		// Check if model mappings should be forced ahead of local API keys
+		forceMappings := fh.forceModelMappings != nil && fh.forceModelMappings()
+
+		if forceMappings {
+			// FORCE MODE: Check model mappings FIRST (takes precedence over local API keys)
+			// This allows users to route Amp requests to their preferred OAuth providers
+			if mappedModels, mappedProviders := resolveMappedModels(); len(mappedModels) > 0 {
+				applyMapping(mappedModels, mappedProviders)
+			}
+
 			// If no mapping applied, check for local providers
 			if !usedMapping {
 				providers = util.GetProviderName(normalizedModel)
@@ -250,17 +257,7 @@ func (fh *FallbackHandler) WrapHandler(handler gin.HandlerFunc) gin.HandlerFunc
 			if len(providers) == 0 {
 				// No providers configured - check if we have a model mapping
 				if mappedModels, mappedProviders := resolveMappedModels(); len(mappedModels) > 0 {
-					// Mapping found and provider available - rewrite the model in request body
+					applyMapping(mappedModels, mappedProviders)
-					bodyBytes = rewriteModelInRequest(bodyBytes, mappedModels[0])
-					c.Request.Body = io.NopCloser(bytes.NewReader(bodyBytes))
-					// Store mapped model and fallbacks in context for handlers
-					c.Set(string(ctxkeys.MappedModel), mappedModels[0])
-					if len(mappedModels) > 1 {
-						c.Set(string(ctxkeys.FallbackModels), mappedModels[1:])
-					}
-					resolvedModel = mappedModels[0]
-					usedMapping = true
-					providers = mappedProviders
 				}
 			}
 		}

internal/api/modules/amp/model_mapping.go

@@ -89,20 +89,6 @@ func (m *DefaultModelMapper) UpdateOAuthModelAlias(aliases map[string][]config.O
 	log.Debugf("amp model mapping: loaded oauth-model-alias for %d channel(s)", len(forward))
 }
 
-// findProviderViaOAuthAlias checks if targetModel is an oauth-model-alias name
-// and returns all aliases that have available providers.
-// Returns the first alias and its providers for backward compatibility,
-// and also populates allAliases with all available alias models.
-func (m *DefaultModelMapper) findProviderViaOAuthAlias(targetModel string) (aliasModel string, providers []string) {
-	aliases := m.findAllAliasesWithProviders(targetModel)
-	if len(aliases) == 0 {
-		return "", nil
-	}
-	// Return first one for backward compatibility
-	first := aliases[0]
-	return first, util.GetProviderName(first)
-}
-
 // findAllAliasesWithProviders returns all oauth-model-alias aliases for targetModel
 // that have available providers. Useful for fallback when one alias is quota-exceeded.
 func (m *DefaultModelMapper) findAllAliasesWithProviders(targetModel string) []string {
@@ -222,7 +208,7 @@ func (m *DefaultModelMapper) MapModelWithFallbacks(requestedModel string) []stri
 	if len(allAliases) == 1 {
 		log.Debugf("amp model mapping: resolved %s -> %s via oauth-model-alias", targetModel, allAliases[0])
 	} else {
-		log.Debugf("amp model mapping: resolved %s -> %v via oauth-model-alias (%d fallbacks)", targetModel, allAliases, len(allAliases))
+		log.Debugf("amp model mapping: resolved %s -> %v via oauth-model-alias (%d fallbacks)", targetModel, allAliases, len(allAliases)-1)
 	}
 
 	// Apply suffix to all aliases