plandex-ai/plandex · error

%s is a built-in model pack name, so it can't be used for a

Error message

%s is a built-in model pack name, so it can't be used for a custom model pack

What it means

Custom model pack names must not shadow built-in model pack names (checked against shared.BuiltInModelPacksByName). A collision is rejected with HTTP 422 and a message naming the offending pack name, because built-in packs would be shadowed or ambiguously referenced in role config.

Source

Thrown at app/server/handlers/models.go:103

			msg := fmt.Sprintf("%s is a built-in base model id, so it can't be used for a custom model", model.ModelId)
			log.Println(msg)
			http.Error(w, msg, http.StatusUnprocessableEntity)
			return
		}
	}

	for _, modelPack := range modelsInput.CustomModelPacks {
		if modelPack.Name == "" {
			msg := "Model pack name is required"
			log.Println(msg)
			http.Error(w, msg, http.StatusBadRequest)
			return
		}

		if shared.BuiltInModelPacksByName[modelPack.Name] != nil {
			msg := fmt.Sprintf("%s is a built-in model pack name, so it can't be used for a custom model pack", modelPack.Name)
			log.Println(msg)
			http.Error(w, msg, http.StatusUnprocessableEntity)
			return
		}
	}

	var existingCustomModelIds = make(map[shared.ModelId]bool)
	var existingCustomProviderNames = make(map[string]bool)

	customModels, err := db.ListCustomModels(auth.OrgId)
	if err != nil {
		log.Printf("Error fetching custom models: %v\n", err)
		http.Error(w, "Failed to create custom model: "+err.Error(), http.StatusInternalServerError)
		return
	}

	customModelPacks, err := db.ListModelPacks(auth.OrgId)
	if err != nil {
		log.Printf("Error fetching custom model packs: %v\n", err)
		http.Error(w, "Failed to create custom model: "+err.Error(), http.StatusInternalServerError)

View on GitHub (pinned to e2d772072e)

Solutions

1. Rename the custom pack to a name not present in the built-in model packs table
2. If you want built-in behavior, reference the built-in pack name directly in config rather than redefining it
3. Create a modified copy under a new name if you need a variant of a built-in pack
4. After upgrading Plandex, verify custom pack names against the new built-in pack list

Example fix

// before
{"customModelPacks": [{"name": "default", "models": {...}}]}
// after
{"customModelPacks": [{"name": "my-default", "models": {...}}]}

for _, p := range input.CustomModelPacks {
    if shared.BuiltInModelPacksByName[p.Name] != nil {
        return fmt.Errorf("%s is a built-in model pack name; choose a different name", p.Name)
    }
}

func isBuiltInModelPackName(name string) bool { return shared.BuiltInModelPacksByName[name] != nil }

When it happens

Trigger: POSTing custom model packs where a pack's name equals a built-in pack name (e.g. "default", or any name defined in the shared built-in model packs table).

Common situations: Trying to override a built-in pack by reusing its name instead of inventing a new one; copying a built-in pack definition into custom packs and forgetting to rename it; a Plandex upgrade making a previously-legal custom pack name built-in.

Related errors

• %s is a built-in base model id, so it can't be used for a cu
• File %s is too large: %d (max %d)
• Has duplicates:
• Provider name is required
• Model id is required

AI-assisted analysis of plandex-ai/plandex@e2d772072e (2026-09-05). Data as JSON: /api/errors/6c8ad2eb8cc129ec. Report an issue: GitHub.