auth: decouple CLI from SDK's Experimental_IsUnifiedHost field

NEXT_CHANGELOG.md

@@ -5,8 +5,8 @@
 ### CLI
 
 * Moved file-based OAuth token cache management from the SDK to the CLI. No user-visible change; part of a three-PR sequence that makes the CLI the sole owner of its token cache.
-* Added experimental OS-native secure token storage behind the `--secure-storage` flag on `databricks auth login` and the `DATABRICKS_AUTH_STORAGE=secure` environment variable. Hidden from help during MS1. Legacy file-backed token storage remains the default.
-* Added experimental OS-native secure token storage opt-in via `DATABRICKS_AUTH_STORAGE=secure` or `[__settings__].auth_storage = secure` in `.databrickscfg`. Legacy file-backed token storage remains the default.
+* Added experimental OS-native secure token storage, opt-in via the `--secure-storage` flag on `databricks auth login` or the `DATABRICKS_AUTH_STORAGE=secure` environment variable. Legacy file-backed token storage remains the default.
+* Remove the `--experimental-is-unified-host` flag and stop reading `experimental_is_unified_host` from `.databrickscfg` profiles and the `DATABRICKS_EXPERIMENTAL_IS_UNIFIED_HOST` env var. Unified hosts are now detected exclusively from `/.well-known/databricks-config` discovery. The `experimental_is_unified_host` field is retained as a no-op in `databricks.yml` for schema compatibility.
 
 ### Bundles
 

bundle/config/workspace.go

@@ -46,6 +46,11 @@ type Workspace struct {
 	AzureLoginAppID  string `json:"azure_login_app_id,omitempty"`
 
 	// Unified host specific attributes.
+	//
+	// ExperimentalIsUnifiedHost is a deprecated no-op. Unified hosts are now
+	// detected automatically from /.well-known/databricks-config. The field is
+	// retained so existing databricks.yml files using it still validate against
+	// the bundle schema.
 	ExperimentalIsUnifiedHost bool   `json:"experimental_is_unified_host,omitempty"`
 	AccountID                 string `json:"account_id,omitempty"`
 	WorkspaceID               string `json:"workspace_id,omitempty"`
@@ -135,9 +140,8 @@ func (w *Workspace) Config(ctx context.Context) *config.Config {
 		AzureLoginAppID:  w.AzureLoginAppID,
 
 		// Unified host
-		Experimental_IsUnifiedHost: w.ExperimentalIsUnifiedHost,
-		AccountID:                  w.AccountID,
-		WorkspaceID:                w.WorkspaceID,
+		AccountID:   w.AccountID,
+		WorkspaceID: w.WorkspaceID,
 	}
 
 	for k := range config.ConfigAttributes {