fix(api): report an alias's target in /v1/models/capabilities (#12183)

An alias config is a pure redirect with no backend of its own, so the
capabilities listing described it from its stub: no capabilities, no
modalities, and the default 4096 context_size. Clients that size their
context budget from this endpoint (nib, for one) then compacted every
turn against a model that really serves 100k.

Resolve the alias and report the target's capabilities, modalities and
context_size under the alias's id. A dangling or chained alias now
reports no enrichment instead of defaults no model runs with.

Co-authored-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

core/http/endpoints/openai/list_capabilities.go

@@ -35,7 +35,7 @@ func ListModelCapabilitiesEndpoint(bcl *config.ModelConfigLoader, ml *model.Mode
 		dataModels := []schema.ModelCapabilities{}
 		for _, m := range modelNames {
 			entry := schema.ModelCapabilities{ID: m, Object: "model"}
-			if cfg, ok := bcl.GetModelConfig(m); ok {
+			if cfg, ok := modelConfigFor(bcl, m); ok {
 				entry.Capabilities = cfg.Capabilities()
 				entry.ThreeDOperations = cfg.ThreeDOperations()
 				entry.InputModalities = cfg.InputModalities()
@@ -53,3 +53,22 @@ func ListModelCapabilitiesEndpoint(bcl *config.ModelConfigLoader, ml *model.Mode
 		})
 	}
 }
+
+// modelConfigFor returns the config that describes what a listed model can
+// do. An alias is a pure redirect whose own config carries no backend, so its
+// capabilities, modalities and context_size would all be empty defaults;
+// report the target's instead, since that is the model a request for the
+// alias reaches. A dangling or chained alias returns false: the endpoint then
+// reports the entry without enrichment rather than advertise defaults no
+// model runs with.
+func modelConfigFor(bcl *config.ModelConfigLoader, name string) (config.ModelConfig, bool) {
+	cfg, ok := bcl.GetModelConfig(name)
+	if !ok {
+		return config.ModelConfig{}, false
+	}
+	resolved, _, err := bcl.ResolveAlias(&cfg)
+	if err != nil {
+		return config.ModelConfig{}, false
+	}
+	return *resolved, true
+}

core/http/endpoints/openai/list_capabilities_test.go

@@ -142,4 +142,44 @@ parameters:
 		Expect(entry).NotTo(BeNil())
 		Expect(entry.ContextSize).To(Equal(backend.DefaultContextSize))
 	})
+	It("reports an alias with its target's capabilities and context_size", func() {
+		writeConfig("real-llm", `
+name: real-llm
+backend: llama-cpp
+context_size: 100000
+known_usecases:
+  - FLAG_CHAT
+  - FLAG_VISION
+template:
+  chat: "{{ .Input }}"
+parameters:
+  model: model.gguf
+`)
+		writeConfig("friendly", `
+name: friendly
+alias: real-llm
+`)
+		resp := call()
+		target := entryFor(resp, "real-llm")
+		Expect(target).NotTo(BeNil())
+
+		entry := entryFor(resp, "friendly")
+		Expect(entry).NotTo(BeNil())
+		Expect(entry.ID).To(Equal("friendly"))
+		Expect(entry.ContextSize).To(Equal(100000))
+		Expect(entry.Capabilities).To(Equal(target.Capabilities))
+		Expect(entry.InputModalities).To(Equal(target.InputModalities))
+		Expect(entry.OutputModalities).To(Equal(target.OutputModalities))
+	})
+
+	It("reports no context_size for an alias whose target does not exist", func() {
+		writeConfig("dangling", `
+name: dangling
+alias: missing-model
+`)
+		entry := entryFor(call(), "dangling")
+		Expect(entry).NotTo(BeNil())
+		Expect(entry.ContextSize).To(BeZero())
+		Expect(entry.Capabilities).To(BeEmpty())
+	})
 })