refactor: name the proxy backends with constants

Review asked for constants instead of the "cloud-proxy" and
"localai-proxy" literals. Add CloudProxyBackend and LocalAIProxyBackend next
to the other backend-name constants in pkg/model (WhisperBackend,
TransformersBackend, ...), which core/config already imports, and use them
in every production check: the proxy options builder, IsRemoteProxy,
IsCloudProxyBackendPassthrough, the PII defaults, the localai-proxy backend
hook and loader warning, and the PII middleware metadata in the routes and
the in-process MCP client.

The proxy options builder now calls IsRemoteProxy() instead of repeating
the two-backend check, so the set of proxy backends is defined once.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

core/backend/options.go

@@ -542,7 +542,7 @@ func grpcModelOpts(c config.ModelConfig, modelPath string) *pb.ModelOptions {
 		Tokenizer: c.Tokenizer,
 	}
 
-	if c.Backend == "cloud-proxy" || c.Backend == "localai-proxy" {
+	if c.IsRemoteProxy() {
 		opts.Proxy = &pb.ProxyOptions{
 			UpstreamUrl:           c.Proxy.UpstreamURL,
 			Mode:                  c.Proxy.Mode,
@@ -558,7 +558,7 @@ func grpcModelOpts(c config.ModelConfig, modelPath string) *pb.ModelOptions {
 		// failover.UpstreamModel uses. Not for cloud-proxy: its translate mode
 		// falls back to parameters.model and passthrough keeps the client's
 		// model when upstream_model is empty.
-		if c.Backend == "localai-proxy" && opts.Proxy.UpstreamModel == "" {
+		if c.Backend == model.LocalAIProxyBackend && opts.Proxy.UpstreamModel == "" {
 			opts.Proxy.UpstreamModel = c.Name
 		}
 	}

core/config/hooks_localai_proxy.go

@@ -1,7 +1,9 @@
 package config
 
+import "github.com/mudler/LocalAI/pkg/model"
+
 func init() {
-	RegisterBackendHook("localai-proxy", localAIProxyDefaults)
+	RegisterBackendHook(model.LocalAIProxyBackend, localAIProxyDefaults)
 }
 
 // localAIProxyDefaults makes chat requests reach the upstream as structured

core/config/model_config.go

@@ -17,6 +17,7 @@ import (
 	"github.com/mudler/LocalAI/core/services/routing/piipattern"
 	"github.com/mudler/LocalAI/pkg/downloader"
 	"github.com/mudler/LocalAI/pkg/functions"
+	"github.com/mudler/LocalAI/pkg/model"
 	"github.com/mudler/LocalAI/pkg/modelartifacts"
 	"github.com/mudler/LocalAI/pkg/reasoning"
 	"github.com/mudler/cogito"
@@ -332,7 +333,7 @@ func (p ProxyConfig) ResolveAPIKey(envLookup func(string) string) (string, error
 // passthrough (SetDefaults normalises it, but Validate accepts empty
 // too — handlers should not rely on a particular call order).
 func (c *ModelConfig) IsCloudProxyBackendPassthrough() bool {
-	if c.Backend != "cloud-proxy" {
+	if c.Backend != model.CloudProxyBackend {
 		return false
 	}
 	return c.Proxy.Mode == "" || c.Proxy.Mode == ProxyModePassthrough
@@ -670,7 +671,7 @@ func (c *ModelConfig) PIIIsEnabled() bool {
 	if c.PII.Enabled != nil {
 		return *c.PII.Enabled
 	}
-	return c.Backend == "cloud-proxy"
+	return c.Backend == model.CloudProxyBackend
 }
 
 // PIIDetectors returns the names of the token-classification models that
@@ -701,7 +702,7 @@ var piiCoverableUsecases = []ModelConfigUsecase{FLAG_CHAT, FLAG_COMPLETION, FLAG
 // false naturally: HasUsecases short-circuits to false for any usecase a
 // declared score/token_classify model did not itself declare.
 func (c *ModelConfig) PIIFilterApplies() bool {
-	if c.Backend == "cloud-proxy" {
+	if c.Backend == model.CloudProxyBackend {
 		return true
 	}
 	return slices.ContainsFunc(piiCoverableUsecases, c.HasUsecases)

core/config/model_config_failover.go

@@ -3,6 +3,8 @@ package config
 import (
 	"fmt"
 	"time"
+
+	"github.com/mudler/LocalAI/pkg/model"
 )
 
 // FailoverConfig turns a model config into a failover chain: requests for the
@@ -54,7 +56,7 @@ func (c ModelConfig) IsFailover() bool { return c.Failover != nil }
 // `warm` has no effect on it.
 func (c ModelConfig) IsRemoteProxy() bool {
 	switch c.Backend {
-	case "cloud-proxy", "localai-proxy":
+	case model.CloudProxyBackend, model.LocalAIProxyBackend:
 		return true
 	}
 	return false

core/config/model_config_loader.go

@@ -17,6 +17,7 @@ import (
 	"github.com/charmbracelet/glamour"
 	"github.com/mudler/LocalAI/core/schema"
 	"github.com/mudler/LocalAI/pkg/downloader"
+	"github.com/mudler/LocalAI/pkg/model"
 	"github.com/mudler/LocalAI/pkg/modelartifacts"
 	"github.com/mudler/LocalAI/pkg/safefile"
 	"github.com/mudler/LocalAI/pkg/utils"
@@ -963,7 +964,7 @@ func (bcl *ModelConfigLoader) loadModelConfigsFromPath(path string, strict bool,
 	// when a config carries settings that only make sense there, or lacks
 	// the usecases failover's own usecase-sharing check depends on.
 	for name, cfg := range bcl.configs {
-		if cfg.Backend != "localai-proxy" {
+		if cfg.Backend != model.LocalAIProxyBackend {
 			continue
 		}
 		if cfg.Proxy.Mode == ProxyModeTranslate || cfg.Proxy.Provider != "" {

core/http/routes/middleware.go

@@ -12,6 +12,7 @@ import (
 	"github.com/mudler/LocalAI/core/http/endpoints/localai"
 	"github.com/mudler/LocalAI/core/http/middleware"
 	"github.com/mudler/LocalAI/core/services/routing/router"
+	"github.com/mudler/LocalAI/pkg/model"
 )
 
 // RegisterMiddlewareRoutes wires the routing-module admin surface that
@@ -348,7 +349,7 @@ func buildPIIStatus(app *application.Application) map[string]any {
 			// Why is this on? backend default (cloud-proxy) vs an explicit YAML
 			// toggle. Helps admins understand the resolved state without
 			// reading source.
-			"default_for_backend": !explicit && cfg.Backend == "cloud-proxy",
+			"default_for_backend": !explicit && cfg.Backend == model.CloudProxyBackend,
 			// The detectors came from the global default, not this model's YAML.
 			"detectors_from_default": enabled && len(ownDetectors) == 0 && len(detectors) > 0,
 		}
@@ -403,7 +404,7 @@ func buildPIIStatus(app *application.Application) map[string]any {
 
 	return map[string]any{
 		"enabled_globally":             true,
-		"default_enabled_for_backends": []string{"cloud-proxy"},
+		"default_enabled_for_backends": []string{model.CloudProxyBackend},
 		"models":                       models,
 		"detector_models":              detectorModels,
 		"recent_event_count":           recentCount,

pkg/mcp/localaitools/inproc/client.go

@@ -1008,7 +1008,7 @@ func (c *Client) GetMiddlewareStatus(ctx context.Context) (*localaitools.Middlew
 		EnabledGlobally: c.PIIEvents != nil,
 		Models:          []localaitools.MiddlewarePIIModel{},
 	}
-	piiSection.DefaultEnabledForBackends = []string{"cloud-proxy"}
+	piiSection.DefaultEnabledForBackends = []string{model.CloudProxyBackend}
 	if c.ConfigLoader != nil {
 		for _, cfg := range c.ConfigLoader.GetAllModelsConfigs() {
 			cfg := cfg
@@ -1017,7 +1017,7 @@ func (c *Client) GetMiddlewareStatus(ctx context.Context) (*localaitools.Middlew
 				Backend:           cfg.Backend,
 				Enabled:           cfg.PIIIsEnabled(),
 				Explicit:          cfg.PII.Enabled != nil,
-				DefaultForBackend: cfg.Backend == "cloud-proxy",
+				DefaultForBackend: cfg.Backend == model.CloudProxyBackend,
 				Detectors:         cfg.PIIDetectors(),
 			})
 		}

pkg/model/initializers.go

@@ -51,6 +51,12 @@ const (
 	TransformersBackend = "transformers"
 	LocalStoreBackend   = "local-store"
 	ValkeyStoreBackend  = "valkey-store"
+
+	// Proxy backends serve a model by forwarding to another server instead
+	// of loading weights. Core special-cases both (credentials, failover
+	// kind, PII defaults), so every check goes through these names.
+	CloudProxyBackend   = "cloud-proxy"
+	LocalAIProxyBackend = "localai-proxy"
 )
 
 // starts the grpcModelProcess for the backend, and returns a grpc client