fix: harden model catalog projections

tools/tht/internal/config/installation_model_catalog_test.go

@@ -78,6 +78,13 @@ func TestLoadRejectsInvalidModelCatalogDefaultsAndAuthentication(t *testing.T) {
 			catalog:   strings.Replace(validModelCatalogYAML(), "id: ollama/qwen3-embedding:0.6b", "id: external/qwen3-embedding:0.6b", 1),
 			wantError: "ollama canonical id",
 		},
+		{
+			name: "upstream model aliases must be unique within a provider",
+			catalog: strings.Replace(validModelCatalogYAML(),
+				"      models:\n        glm-5.3:\n",
+				"      models:\n        glm-alias:\n          upstreamModel: glm-5.3\n          session:\n            contextWindow: 200000\n            maxTokens: 131072\n        glm-5.3:\n", 1),
+			wantError: "same upstreamModel",
+		},
 		{
 			name:      "metadata default required",
 			catalog:   strings.Replace(validModelCatalogYAML(), "    metadataGeneration: local/qwen\n", "", 1),

tools/tht/internal/config/model_catalog.go

@@ -14,6 +14,7 @@ const maxCatalogModels = 64
 
 var catalogKeyPattern = regexp.MustCompile(`^[a-z][a-z0-9._-]{0,63}$`)
 var catalogModelIDPattern = regexp.MustCompile(`^[a-z][a-z0-9._-]{0,63}/[A-Za-z0-9][A-Za-z0-9._:-]{0,255}$`)
+var catalogUpstreamModelPattern = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._:-]{0,255}$`)
 var catalogAPIVersionPattern = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9._-]{0,127}$`)
 
 // ModelCatalog is the only operator-authored source for model identity and runtime eligibility.
@@ -163,11 +164,23 @@ func (c ModelCatalog) Validate(environment map[string]string) error {
 			return err
 		}
 		hasSession, providerHasMetadata := false, false
+		upstreamModels := make(map[string]string)
 		for modelID, model := range provider.Models {
 			if !catalogKeyPattern.MatchString(modelID) {
 				return fmt.Errorf("modelCatalog model %q/%q is invalid", providerID, modelID)
 			}
 			canonical := providerID + "/" + modelID
+			upstream := model.UpstreamModel
+			if upstream == "" {
+				upstream = modelID
+			}
+			if !catalogUpstreamModelPattern.MatchString(upstream) {
+				return fmt.Errorf("modelCatalog model %q upstreamModel is invalid", canonical)
+			}
+			if existing, duplicate := upstreamModels[upstream]; duplicate {
+				return fmt.Errorf("modelCatalog models %q and %q use the same upstreamModel", existing, canonical)
+			}
+			upstreamModels[upstream] = canonical
 			if model.Session == nil && model.MetadataGeneration == nil {
 				return fmt.Errorf("modelCatalog model %q has no runtime use", canonical)
 			}