diff --git a/atlas-core/src/main/scala/com/netflix/atlas/core/stacklang/Interpreter.scala b/atlas-core/src/main/scala/com/netflix/atlas/core/stacklang/Interpreter.scala
index cc0f2fc00..8098a3066 100644
--- a/atlas-core/src/main/scala/com/netflix/atlas/core/stacklang/Interpreter.scala
+++ b/atlas-core/src/main/scala/com/netflix/atlas/core/stacklang/Interpreter.scala
@@ -113,21 +113,25 @@ case class Interpreter(vocabulary: List[Word]) {
     if (s.program.isEmpty) s.context else execute(nextStep(s))
   }
 
-  final def execute(program: List[Any], context: Context, unfreeze: Boolean = true): Context = {
+  final def executeProgram(
+    program: List[Any],
+    context: Context,
+    unfreeze: Boolean = true
+  ): Context = {
     val result = execute(Step(program, context.incrementCallDepth)).decrementCallDepth
     if (unfreeze) result.unfreeze else result
   }
 
-  final def execute(program: List[Any]): Context = {
-    execute(program, Context(this, Nil, Map.empty))
+  final def executeProgram(program: List[Any]): Context = {
+    executeProgram(program, Context(this, Nil, Map.empty))
   }
 
-  final def execute(program: String): Context = {
-    execute(splitAndTrim(program))
-  }
-
-  final def execute(program: String, vars: Map[String, Any], features: Features): Context = {
-    execute(splitAndTrim(program), Context(this, Nil, vars, vars, features = features))
+  final def execute(
+    program: String,
+    vars: Map[String, Any] = Map.empty,
+    features: Features = Features.STABLE
+  ): Context = {
+    executeProgram(splitAndTrim(program), Context(this, Nil, vars, vars, features = features))
   }
 
   @scala.annotation.tailrec
@@ -145,7 +149,7 @@ case class Interpreter(vocabulary: List[Word]) {
   }
 
   final def debug(program: List[Any]): List[Step] = {
-    debug(program, Context(this, Nil, Map.empty))
+    debug(program, Context(this, Nil, Map.empty, features = Features.UNSTABLE))
   }
 
   final def debug(program: String): List[Step] = {
diff --git a/atlas-core/src/main/scala/com/netflix/atlas/core/stacklang/StandardVocabulary.scala b/atlas-core/src/main/scala/com/netflix/atlas/core/stacklang/StandardVocabulary.scala
index 05b07106b..12918340b 100644
--- a/atlas-core/src/main/scala/com/netflix/atlas/core/stacklang/StandardVocabulary.scala
+++ b/atlas-core/src/main/scala/com/netflix/atlas/core/stacklang/StandardVocabulary.scala
@@ -57,7 +57,7 @@ object StandardVocabulary extends Vocabulary {
     override def matches(stack: List[Any]): Boolean = true
 
     override def execute(context: Context): Context = {
-      context.interpreter.execute(body, context, unfreeze = false)
+      context.interpreter.executeProgram(body, context, unfreeze = false)
     }
 
     override def summary: String =
@@ -81,7 +81,7 @@ object StandardVocabulary extends Vocabulary {
     override def execute(context: Context): Context = {
       context.stack match {
         case (vs: List[?]) :: stack =>
-          context.interpreter.execute(vs, context.copy(stack = stack), unfreeze = false)
+          context.interpreter.executeProgram(vs, context.copy(stack = stack), unfreeze = false)
         case _ => invalidStack
       }
     }
@@ -198,7 +198,7 @@ object StandardVocabulary extends Vocabulary {
       context.stack match {
         case (f: List[?]) :: (vs: List[?]) :: stack =>
           vs.reverse.foldLeft(context.copy(stack = stack)) { (c, v) =>
-            c.interpreter.execute(f, c.copy(stack = v :: c.stack), unfreeze = false)
+            c.interpreter.executeProgram(f, c.copy(stack = v :: c.stack), unfreeze = false)
           }
         case _ => invalidStack
       }
@@ -362,7 +362,8 @@ object StandardVocabulary extends Vocabulary {
           val init = context.copy(stack = stack)
           val res = vs.foldLeft(List.empty[Any] -> init) {
             case ((rs, c), v) =>
-              val rc = c.interpreter.execute(f, c.copy(stack = v :: c.stack), unfreeze = false)
+              val rc =
+                c.interpreter.executeProgram(f, c.copy(stack = v :: c.stack), unfreeze = false)
               (rc.stack.head :: rs) -> rc.copy(stack = rc.stack.tail)
           }
           res._2.copy(stack = res._1.reverse :: res._2.stack)
diff --git a/atlas-core/src/test/scala/com/netflix/atlas/core/stacklang/InterpreterSuite.scala b/atlas-core/src/test/scala/com/netflix/atlas/core/stacklang/InterpreterSuite.scala
index 1ee739e48..38701662b 100644
--- a/atlas-core/src/test/scala/com/netflix/atlas/core/stacklang/InterpreterSuite.scala
+++ b/atlas-core/src/test/scala/com/netflix/atlas/core/stacklang/InterpreterSuite.scala
@@ -15,6 +15,7 @@
  */
 package com.netflix.atlas.core.stacklang
 
+import com.netflix.atlas.core.util.Features
 import munit.FunSuite
 
 class InterpreterSuite extends FunSuite {
@@ -40,28 +41,28 @@ class InterpreterSuite extends FunSuite {
   }
 
   test("empty") {
-    assertEquals(interpreter.execute(Nil), context(Nil))
+    assertEquals(interpreter.executeProgram(Nil), context(Nil))
   }
 
   test("push items") {
-    assertEquals(interpreter.execute(List("foo", "bar")), context(List("bar", "foo")))
+    assertEquals(interpreter.executeProgram(List("foo", "bar")), context(List("bar", "foo")))
   }
 
   test("execute word") {
-    assertEquals(interpreter.execute(List(":push-foo")), context(List("foo")))
+    assertEquals(interpreter.executeProgram(List(":push-foo")), context(List("foo")))
   }
 
   test("overloaded word") {
-    assertEquals(interpreter.execute(List(":overloaded")), context(List("one")))
+    assertEquals(interpreter.executeProgram(List(":overloaded")), context(List("one")))
   }
 
   test("overloaded word and some don't match") {
-    assertEquals(interpreter.execute(List(":overloaded2")), context(List("two")))
+    assertEquals(interpreter.executeProgram(List(":overloaded2")), context(List("two")))
   }
 
   test("word with no matches") {
     val e = intercept[IllegalStateException] {
-      interpreter.execute(List(":no-match"))
+      interpreter.executeProgram(List(":no-match"))
     }
     val expected = "no matches for word ':no-match' with stack [], candidates: [exception]"
     assertEquals(e.getMessage, expected)
@@ -69,7 +70,7 @@ class InterpreterSuite extends FunSuite {
 
   test("using unstable word fails by default") {
     val e = intercept[IllegalStateException] {
-      interpreter.execute(List(":unstable"))
+      interpreter.executeProgram(List(":unstable"))
     }
     val expected = "to use :unstable enable unstable features"
     assertEquals(e.getMessage, expected)
@@ -77,53 +78,56 @@ class InterpreterSuite extends FunSuite {
 
   test("unknown word") {
     val e = intercept[IllegalStateException] {
-      interpreter.execute(List("foo", ":unknown"))
+      interpreter.executeProgram(List("foo", ":unknown"))
     }
     assertEquals(e.getMessage, "unknown word ':unknown'")
   }
 
   test("unmatched closing paren") {
     val e = intercept[IllegalStateException] {
-      interpreter.execute(List(")"))
+      interpreter.executeProgram(List(")"))
     }
     assertEquals(e.getMessage, "unmatched closing parenthesis")
   }
 
   test("unmatched closing paren 2") {
     val e = intercept[IllegalStateException] {
-      interpreter.execute(List("(", ")", ")"))
+      interpreter.executeProgram(List("(", ")", ")"))
     }
     assertEquals(e.getMessage, "unmatched closing parenthesis")
   }
 
   test("unmatched opening paren") {
     val e = intercept[IllegalStateException] {
-      interpreter.execute(List("("))
+      interpreter.executeProgram(List("("))
     }
     assertEquals(e.getMessage, "unmatched opening parenthesis")
   }
 
   test("list") {
     val list = List("(", "1", ")")
-    assertEquals(interpreter.execute(list), context(List(List("1"))))
+    assertEquals(interpreter.executeProgram(list), context(List(List("1"))))
   }
 
   test("nested list") {
     val list = List("(", "1", "(", ")", ")")
-    assertEquals(interpreter.execute(list), context(List(List("1", "(", ")"))))
+    assertEquals(interpreter.executeProgram(list), context(List(List("1", "(", ")"))))
   }
 
   test("multiple lists") {
     val list = List("(", "1", ")", "(", "2", ")")
-    assertEquals(interpreter.execute(list), context(List(List("2"), List("1"))))
+    assertEquals(interpreter.executeProgram(list), context(List(List("2"), List("1"))))
   }
 
   test("debug") {
+    def createContext(stack: List[Any]): Context = {
+      Context(interpreter, stack, Map.empty, features = Features.UNSTABLE)
+    }
     val list = List("(", "1", ")", "(", "2", ")")
     val expected = List(
-      Interpreter.Step(list, Context(interpreter, Nil, Map.empty)),
-      Interpreter.Step(list.drop(3), Context(interpreter, List(List("1")), Map.empty)),
-      Interpreter.Step(Nil, Context(interpreter, List(List("2"), List("1")), Map.empty))
+      Interpreter.Step(list, createContext(Nil)),
+      Interpreter.Step(list.drop(3), createContext(List(List("1")))),
+      Interpreter.Step(Nil, createContext(List(List("2"), List("1"))))
     )
     assertEquals(interpreter.debug(list), expected)
   }
diff --git a/atlas-webapi/src/main/scala/com/netflix/atlas/webapi/ExprApi.scala b/atlas-webapi/src/main/scala/com/netflix/atlas/webapi/ExprApi.scala
index 2d8733050..554089797 100644
--- a/atlas-webapi/src/main/scala/com/netflix/atlas/webapi/ExprApi.scala
+++ b/atlas-webapi/src/main/scala/com/netflix/atlas/webapi/ExprApi.scala
@@ -30,6 +30,7 @@ import com.netflix.atlas.core.model.TimeSeriesExpr
 import com.netflix.atlas.core.stacklang.Context
 import com.netflix.atlas.core.stacklang.Interpreter
 import com.netflix.atlas.core.stacklang.Word
+import com.netflix.atlas.core.util.Features
 import com.netflix.atlas.core.util.Strings
 import com.netflix.atlas.json.Json
 import com.netflix.atlas.pekko.CustomDirectives.*
@@ -154,7 +155,7 @@ class ExprApi extends WebApi {
   // macros it alwasy returns true. This ensures the operation will actually be successful before
   // returning to a user.
   private def execWorks(interpreter: Interpreter, w: Word, ctxt: Context): Boolean = {
-    Try(interpreter.execute(List(s":${w.name}"), ctxt)).isSuccess
+    Try(interpreter.executeProgram(List(s":${w.name}"), ctxt)).isSuccess
   }
 
   private def matches(interpreter: Interpreter, w: Word, ctxt: Context): Boolean = {
@@ -163,7 +164,7 @@ class ExprApi extends WebApi {
 
   private def processCompleteRequest(query: String, vocabName: String): HttpResponse = {
     val interpreter = newInterpreter(vocabName)
-    val result = interpreter.execute(query)
+    val result = interpreter.execute(query, features = Features.UNSTABLE)
 
     val candidates = interpreter.vocabulary.filter { w =>
       matches(interpreter, w, result)
@@ -185,7 +186,7 @@ class ExprApi extends WebApi {
     */
   private def processQueriesRequest(expr: String, vocabName: String): HttpResponse = {
     val interpreter = newInterpreter(vocabName)
-    val result = interpreter.execute(expr)
+    val result = interpreter.execute(expr, features = Features.UNSTABLE)
 
     val exprs = result.stack.collect {
       case ModelExtractors.PresentationType(t) => t
@@ -291,7 +292,7 @@ object ExprApi {
   }
 
   private def eval(interpreter: Interpreter, expr: String): List[StyleExpr] = {
-    interpreter.execute(expr).stack.collect {
+    interpreter.execute(expr, features = Features.UNSTABLE).stack.collect {
       case ModelExtractors.PresentationType(t) => t
     }
   }