diff --git a/core/application/studio_service.go b/core/application/studio_service.go
index 6125791912..830dbd9f3c 100644
--- a/core/application/studio_service.go
+++ b/core/application/studio_service.go
@@ -14,6 +14,7 @@ import (
 	"github.com/mudler/xlog"
 	"gorm.io/gorm"
 
+	corebackend "github.com/mudler/LocalAI/core/backend"
 	"github.com/mudler/LocalAI/core/config"
 	"github.com/mudler/LocalAI/core/http/auth"
 	mcpendpoint "github.com/mudler/LocalAI/core/http/endpoints/mcp"
@@ -323,14 +324,17 @@ func (a *Application) studioModelConfig(model string) (config.ModelConfig, bool)
 	return bcl.GetModelConfig(name)
 }
 
-// studioContextTokens is the context window of a model, or zero when its config
-// does not say.
+// studioContextTokens is the context window a request to the model can use. A
+// config without context_size runs the backend with its default window, so that
+// is the limit (the same one /v1/models/capabilities reports), not a guess of
+// the harness. Zero only for a model with no local config (a remote one), whose
+// window is not known here.
 func (a *Application) studioContextTokens(model string) int {
 	cfg, ok := a.studioModelConfig(model)
-	if !ok || cfg.ContextSize == nil {
+	if !ok {
 		return 0
 	}
-	return *cfg.ContextSize
+	return corebackend.EffectiveRequestContextSize(cfg)
 }
 
 // studioModalities says which inputs a chat model takes natively, from its
diff --git a/core/application/studio_service_test.go b/core/application/studio_service_test.go
index 8818d02ef7..f56c9c0abd 100644
--- a/core/application/studio_service_test.go
+++ b/core/application/studio_service_test.go
@@ -89,7 +89,8 @@ var _ = Describe("studio service at startup", func() {
 		size := 4096
 		app.ModelConfigLoader().ReplaceModelConfigs([]config.ModelConfig{{Name: "small", LLMConfig: config.LLMConfig{ContextSize: &size}}, {Name: "unset"}})
 		Expect(app.studioContextTokens("small")).To(Equal(4096))
-		Expect(app.studioContextTokens("unset")).To(Equal(0))
+		// No context_size: the backend runs with its default window.
+		Expect(app.studioContextTokens("unset")).To(Equal(config.DefaultContextSize))
 		Expect(app.studioContextTokens("missing")).To(Equal(0))
 	})