diff --git a/javascript/ql/lib/Expressions/ExprHasNoEffect.qll b/javascript/ql/lib/Expressions/ExprHasNoEffect.qll
index 5e194b3fc3a5..86f9d4133d88 100644
--- a/javascript/ql/lib/Expressions/ExprHasNoEffect.qll
+++ b/javascript/ql/lib/Expressions/ExprHasNoEffect.qll
@@ -1,7 +1,7 @@
 /**
  * Provides classes and predicates for the 'js/useless-expression' query.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/LanguageFeatures/UnusedIndexVariable.qll b/javascript/ql/lib/LanguageFeatures/UnusedIndexVariable.qll
index e8b235eca9b0..c9905d98fccc 100644
--- a/javascript/ql/lib/LanguageFeatures/UnusedIndexVariable.qll
+++ b/javascript/ql/lib/LanguageFeatures/UnusedIndexVariable.qll
@@ -1,7 +1,7 @@
 /**
  * Provides a predicate for identifying unused index variables in loops.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/AMD.qll b/javascript/ql/lib/semmle/javascript/AMD.qll
index e66a04ce4ecd..479be828f926 100644
--- a/javascript/ql/lib/semmle/javascript/AMD.qll
+++ b/javascript/ql/lib/semmle/javascript/AMD.qll
@@ -2,7 +2,7 @@
  * Provides classes for working with
  * [Asynchronous Module Definitions](https://github.com/amdjs/amdjs-api/wiki/AMD).
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/AST.qll b/javascript/ql/lib/semmle/javascript/AST.qll
index 0e6330605ba5..c37a4e938a23 100644
--- a/javascript/ql/lib/semmle/javascript/AST.qll
+++ b/javascript/ql/lib/semmle/javascript/AST.qll
@@ -1,7 +1,7 @@
 /**
  * Provides classes for working with the AST-based representation of JavaScript programs.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
@@ -477,7 +477,7 @@ module AST {
     DataFlow::AnalyzedNode analyze() { result = DataFlow::valueNode(this).analyze() }
 
     /** Gets the data flow node associated with this program element. */
-    overlay[caller]
+    overlay[caller?]
     pragma[inline]
     DataFlow::ValueNode flow() { result = DataFlow::valueNode(this) }
 
diff --git a/javascript/ql/lib/semmle/javascript/CFG.qll b/javascript/ql/lib/semmle/javascript/CFG.qll
index 2270ddfeaaf3..f7943647d77b 100644
--- a/javascript/ql/lib/semmle/javascript/CFG.qll
+++ b/javascript/ql/lib/semmle/javascript/CFG.qll
@@ -272,7 +272,7 @@
  * Note that the `import` statement as a whole is part of the CFG of the body, while its single
  * import specifier `x as y` forms part of the preamble.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Classes.qll b/javascript/ql/lib/semmle/javascript/Classes.qll
index 2485553370c6..7f6ea5ba4925 100644
--- a/javascript/ql/lib/semmle/javascript/Classes.qll
+++ b/javascript/ql/lib/semmle/javascript/Classes.qll
@@ -4,7 +4,7 @@
  * Class declarations and class expressions are modeled by (QL) classes `ClassDeclaration`
  * and `ClassExpression`, respectively, which are both subclasses of `ClassDefinition`.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Closure.qll b/javascript/ql/lib/semmle/javascript/Closure.qll
index fd13023b2e6e..930e94a77d77 100644
--- a/javascript/ql/lib/semmle/javascript/Closure.qll
+++ b/javascript/ql/lib/semmle/javascript/Closure.qll
@@ -1,7 +1,7 @@
 /**
  * Provides classes for working with the Closure-Library module system.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Comments.qll b/javascript/ql/lib/semmle/javascript/Comments.qll
index 46ce8b8a4ba9..6365127cad01 100644
--- a/javascript/ql/lib/semmle/javascript/Comments.qll
+++ b/javascript/ql/lib/semmle/javascript/Comments.qll
@@ -1,5 +1,5 @@
 /** Provides classes for working with JavaScript comments. */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Constants.qll b/javascript/ql/lib/semmle/javascript/Constants.qll
index b0b4a6c03eec..acf154346cb6 100644
--- a/javascript/ql/lib/semmle/javascript/Constants.qll
+++ b/javascript/ql/lib/semmle/javascript/Constants.qll
@@ -1,7 +1,7 @@
 /**
  * Provides classes for working with expressions that evaluate to constant values.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/DefUse.qll b/javascript/ql/lib/semmle/javascript/DefUse.qll
index 95cf57d543d2..60e0a728691d 100644
--- a/javascript/ql/lib/semmle/javascript/DefUse.qll
+++ b/javascript/ql/lib/semmle/javascript/DefUse.qll
@@ -1,5 +1,5 @@
 /** Provides classes and predicates for working with variable definitions and uses. */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/E4X.qll b/javascript/ql/lib/semmle/javascript/E4X.qll
index ce917c48cff3..4fef3ba2389c 100644
--- a/javascript/ql/lib/semmle/javascript/E4X.qll
+++ b/javascript/ql/lib/semmle/javascript/E4X.qll
@@ -1,7 +1,7 @@
 /**
  * Provides classes for working with E4X.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/ES2015Modules.qll b/javascript/ql/lib/semmle/javascript/ES2015Modules.qll
index 9f37e3082b89..3710942e9e47 100644
--- a/javascript/ql/lib/semmle/javascript/ES2015Modules.qll
+++ b/javascript/ql/lib/semmle/javascript/ES2015Modules.qll
@@ -1,5 +1,5 @@
 /** Provides classes for working with ECMAScript 2015 modules. */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Errors.qll b/javascript/ql/lib/semmle/javascript/Errors.qll
index 518b76b53461..9015e89efbf4 100644
--- a/javascript/ql/lib/semmle/javascript/Errors.qll
+++ b/javascript/ql/lib/semmle/javascript/Errors.qll
@@ -1,5 +1,5 @@
 /** Provides classes for working with syntax errors. */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Expr.qll b/javascript/ql/lib/semmle/javascript/Expr.qll
index b46faf7e2b79..008cc1283770 100644
--- a/javascript/ql/lib/semmle/javascript/Expr.qll
+++ b/javascript/ql/lib/semmle/javascript/Expr.qll
@@ -1,7 +1,7 @@
 /**
  * Provides classes for working with expressions.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
@@ -253,7 +253,7 @@ class Expr extends @expr, ExprOrStmt, ExprOrType, AST::ValueNode {
    * Gets the data-flow node where exceptions thrown by this expression will
    * propagate if this expression causes an exception to be thrown.
    */
-  overlay[caller]
+  overlay[caller?]
   pragma[inline]
   DataFlow::Node getExceptionTarget() {
     result = getCatchParameterFromStmt(getRawEnclosingStmt(this))
@@ -271,7 +271,7 @@ private DataFlow::Node getCatchParameterFromStmt(Stmt stmt) {
     DataFlow::parameterNode(stmt.getEnclosingTryCatchStmt().getACatchClause().getAParameter())
 }
 
-overlay[caller]
+overlay[caller?]
 pragma[inline]
 private Stmt getRawEnclosingStmt(Expr e) {
   // For performance reasons, we need the enclosing statement without overrides
diff --git a/javascript/ql/lib/semmle/javascript/Extend.qll b/javascript/ql/lib/semmle/javascript/Extend.qll
index e59c11d225ee..b871a74a03b7 100644
--- a/javascript/ql/lib/semmle/javascript/Extend.qll
+++ b/javascript/ql/lib/semmle/javascript/Extend.qll
@@ -1,7 +1,7 @@
 /**
  * Provides classes for reasoning about `extend`-like functions.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Externs.qll b/javascript/ql/lib/semmle/javascript/Externs.qll
index f894107528c4..22d6d03d7dd0 100644
--- a/javascript/ql/lib/semmle/javascript/Externs.qll
+++ b/javascript/ql/lib/semmle/javascript/Externs.qll
@@ -36,7 +36,7 @@
  * Array.prototype.length;
  * </pre>
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Files.qll b/javascript/ql/lib/semmle/javascript/Files.qll
index 8cc14ca0492b..556d25911f11 100644
--- a/javascript/ql/lib/semmle/javascript/Files.qll
+++ b/javascript/ql/lib/semmle/javascript/Files.qll
@@ -1,5 +1,5 @@
 /** Provides classes for working with files and folders. */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Functions.qll b/javascript/ql/lib/semmle/javascript/Functions.qll
index 9b1f98c3d0b6..186ef1bc0289 100644
--- a/javascript/ql/lib/semmle/javascript/Functions.qll
+++ b/javascript/ql/lib/semmle/javascript/Functions.qll
@@ -1,5 +1,5 @@
 /** Provides classes for working with functions. */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/GlobalAccessPaths.qll b/javascript/ql/lib/semmle/javascript/GlobalAccessPaths.qll
index 53e5a779a9b5..7b3004dbde43 100644
--- a/javascript/ql/lib/semmle/javascript/GlobalAccessPaths.qll
+++ b/javascript/ql/lib/semmle/javascript/GlobalAccessPaths.qll
@@ -1,7 +1,7 @@
 /**
  * Provides predicates for associating qualified names with data flow nodes.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
@@ -357,7 +357,7 @@ module AccessPath {
      * Gets a variable that is relevant for the computations in the `GetLaterAccess` module.
      * This predicate restricts as much as it can, but without depending on `getAVariableRef`.
      */
-    overlay[caller]
+    overlay[caller?]
     pragma[inline]
     private SsaVariable getARelevantVariableSimple() {
       // The variable might be used where `getLaterBaseAccess()` is called.
@@ -409,7 +409,7 @@ module AccessPath {
    * }
    * ```
    */
-  overlay[caller]
+  overlay[caller?]
   pragma[inline]
   DataFlow::Node getAReferenceTo(Root root, string path) {
     path = fromReference(result, root) and
@@ -433,7 +433,7 @@ module AccessPath {
    * })(NS = NS || {});
    * ```
    */
-  overlay[caller]
+  overlay[caller?]
   pragma[inline]
   DataFlow::Node getAReferenceTo(string path) {
     path = fromReference(result, DataFlow::globalAccessPathRootPseudoNode())
@@ -455,7 +455,7 @@ module AccessPath {
    * }
    * ```
    */
-  overlay[caller]
+  overlay[caller?]
   pragma[inline]
   DataFlow::Node getAnAssignmentTo(Root root, string path) {
     path = fromRhs(result, root) and
@@ -477,7 +477,7 @@ module AccessPath {
    *  })(foo = foo || {});
    * ```
    */
-  overlay[caller]
+  overlay[caller?]
   pragma[inline]
   DataFlow::Node getAnAssignmentTo(string path) {
     path = fromRhs(result, DataFlow::globalAccessPathRootPseudoNode())
@@ -488,7 +488,7 @@ module AccessPath {
    *
    * See `getAReferenceTo` and `getAnAssignmentTo` for more details.
    */
-  overlay[caller]
+  overlay[caller?]
   pragma[inline]
   DataFlow::Node getAReferenceOrAssignmentTo(string path) {
     result = getAReferenceTo(path)
@@ -501,7 +501,7 @@ module AccessPath {
    *
    * See `getAReferenceTo` and `getAnAssignmentTo` for more details.
    */
-  overlay[caller]
+  overlay[caller?]
   pragma[inline]
   DataFlow::Node getAReferenceOrAssignmentTo(Root root, string path) {
     result = getAReferenceTo(root, path)
@@ -530,7 +530,7 @@ module AccessPath {
   /**
    * Gets a `SourceNode` that refers to the same value or access path as the given node.
    */
-  overlay[caller]
+  overlay[caller?]
   pragma[inline]
   DataFlow::SourceNode getAnAliasedSourceNode(DataFlow::Node node) {
     exists(DataFlow::SourceNode root, string accessPath |
diff --git a/javascript/ql/lib/semmle/javascript/HTML.qll b/javascript/ql/lib/semmle/javascript/HTML.qll
index 8f70150963ef..fa3deaf661f2 100644
--- a/javascript/ql/lib/semmle/javascript/HTML.qll
+++ b/javascript/ql/lib/semmle/javascript/HTML.qll
@@ -1,5 +1,5 @@
 /** Provides classes for working with HTML documents. */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/JSDoc.qll b/javascript/ql/lib/semmle/javascript/JSDoc.qll
index f63e24d9c6c0..48d2a984ec43 100644
--- a/javascript/ql/lib/semmle/javascript/JSDoc.qll
+++ b/javascript/ql/lib/semmle/javascript/JSDoc.qll
@@ -1,5 +1,5 @@
 /** Provides classes for working with JSDoc comments. */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/JSON.qll b/javascript/ql/lib/semmle/javascript/JSON.qll
index ca322bacd467..ba5b42ba1ee7 100644
--- a/javascript/ql/lib/semmle/javascript/JSON.qll
+++ b/javascript/ql/lib/semmle/javascript/JSON.qll
@@ -1,7 +1,7 @@
 /**
  * Provides classes for working with JSON data.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/JSX.qll b/javascript/ql/lib/semmle/javascript/JSX.qll
index d182f1553543..ab9a4339bf75 100644
--- a/javascript/ql/lib/semmle/javascript/JSX.qll
+++ b/javascript/ql/lib/semmle/javascript/JSX.qll
@@ -1,7 +1,7 @@
 /**
  * Provides classes for working with JSX code.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Lines.qll b/javascript/ql/lib/semmle/javascript/Lines.qll
index 272be691498b..e0f675aa6e08 100644
--- a/javascript/ql/lib/semmle/javascript/Lines.qll
+++ b/javascript/ql/lib/semmle/javascript/Lines.qll
@@ -4,7 +4,7 @@
  * This information is only available for snapshots that have been extracted with
  * the `--extract-program-text` flag.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Locations.qll b/javascript/ql/lib/semmle/javascript/Locations.qll
index 1c48a3adbd3f..4aa93dd69377 100644
--- a/javascript/ql/lib/semmle/javascript/Locations.qll
+++ b/javascript/ql/lib/semmle/javascript/Locations.qll
@@ -1,5 +1,5 @@
 /** Provides classes for working with locations and program elements that have locations. */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
@@ -32,7 +32,7 @@ final class Location extends @location_default {
   int getNumLines() { result = this.getEndLine() - this.getStartLine() + 1 }
 
   /** Holds if this location starts before location `that`. */
-  overlay[caller]
+  overlay[caller?]
   pragma[inline]
   predicate startsBefore(Location that) {
     exists(string f, int sl1, int sc1, int sl2, int sc2 |
@@ -46,7 +46,7 @@ final class Location extends @location_default {
   }
 
   /** Holds if this location ends after location `that`. */
-  overlay[caller]
+  overlay[caller?]
   pragma[inline]
   predicate endsAfter(Location that) {
     exists(string f, int el1, int ec1, int el2, int ec2 |
diff --git a/javascript/ql/lib/semmle/javascript/Modules.qll b/javascript/ql/lib/semmle/javascript/Modules.qll
index bc69695121e7..9bd9ce434517 100644
--- a/javascript/ql/lib/semmle/javascript/Modules.qll
+++ b/javascript/ql/lib/semmle/javascript/Modules.qll
@@ -3,7 +3,7 @@
  * ECMAScript 2015-style modules, and the older CommonJS and AMD-style
  * modules.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/NodeJS.qll b/javascript/ql/lib/semmle/javascript/NodeJS.qll
index dfc2dd15ad36..0fbd8d79a749 100644
--- a/javascript/ql/lib/semmle/javascript/NodeJS.qll
+++ b/javascript/ql/lib/semmle/javascript/NodeJS.qll
@@ -17,7 +17,7 @@ private import semmle.javascript.dataflow.internal.DataFlowNode
  *   process.stdout.write(fs.readFileSync(process.argv[i], 'utf8'));
  * ```
  */
-overlay[local]
+overlay[local?]
 class NodeModule extends Module {
   NodeModule() {
     is_module(this) and
@@ -234,7 +234,7 @@ predicate findNodeModulesFolder(Folder f, Folder nodeModules, int distance) {
 /**
  * A Node.js `require` variable.
  */
-overlay[local]
+overlay[local?]
 private class RequireVariable extends Variable {
   RequireVariable() {
     this = any(ModuleScope m).getVariable("require")
@@ -247,7 +247,7 @@ private class RequireVariable extends Variable {
   }
 }
 
-overlay[local]
+overlay[local?]
 private predicate isModuleModule(EarlyStageNode nd) {
   exists(ImportDeclaration imp | imp.getRawImportPath() = "module" |
     nd = TDestructuredModuleImportNode(imp)
@@ -261,7 +261,7 @@ private predicate isModuleModule(EarlyStageNode nd) {
   )
 }
 
-overlay[local]
+overlay[local?]
 private predicate isCreateRequire(EarlyStageNode nd) {
   exists(PropAccess prop |
     isModuleModule(TValueNode(prop.getBase())) and
@@ -291,7 +291,7 @@ private predicate isCreateRequire(EarlyStageNode nd) {
 /**
  * Holds if `nd` may refer to `require`, either directly or modulo local data flow.
  */
-overlay[local]
+overlay[local?]
 cached
 private predicate isRequire(EarlyStageNode nd) {
   exists(VarAccess access |
@@ -334,7 +334,7 @@ private predicate isRequire(EarlyStageNode nd) {
  * require('fs')
  * ```
  */
-overlay[local]
+overlay[local?]
 class Require extends CallExpr, Import {
   Require() { isRequire(TValueNode(this.getCallee())) }
 
diff --git a/javascript/ql/lib/semmle/javascript/Promises.qll b/javascript/ql/lib/semmle/javascript/Promises.qll
index f373ca87d39a..6868505b22a7 100644
--- a/javascript/ql/lib/semmle/javascript/Promises.qll
+++ b/javascript/ql/lib/semmle/javascript/Promises.qll
@@ -186,13 +186,13 @@ module Promises {
   /**
    * Gets the pseudo-field used to describe resolved values in a promise.
    */
-  overlay[local]
+  overlay[local?]
   string valueProp() { result = "$PromiseResolveField$" }
 
   /**
    * Gets the pseudo-field used to describe rejected values in a promise.
    */
-  overlay[local]
+  overlay[local?]
   string errorProp() { result = "$PromiseRejectField$" }
 
   /** A property set containing the pseudo-properites of a promise object. */
diff --git a/javascript/ql/lib/semmle/javascript/Regexp.qll b/javascript/ql/lib/semmle/javascript/Regexp.qll
index db779e600d67..c42df3939c22 100644
--- a/javascript/ql/lib/semmle/javascript/Regexp.qll
+++ b/javascript/ql/lib/semmle/javascript/Regexp.qll
@@ -4,7 +4,7 @@
  * Regular expression literals are represented as an abstract syntax tree of regular expression
  * terms.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/SSA.qll b/javascript/ql/lib/semmle/javascript/SSA.qll
index 52486a7b7e3b..04d08c2343f6 100644
--- a/javascript/ql/lib/semmle/javascript/SSA.qll
+++ b/javascript/ql/lib/semmle/javascript/SSA.qll
@@ -73,7 +73,7 @@
  * expression in `k` induces a re-capture of `x` to reflect the fact that `x`
  * is incremented between the two `console.log` calls.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Stmt.qll b/javascript/ql/lib/semmle/javascript/Stmt.qll
index f97b07ac8e94..95ae6f5be597 100644
--- a/javascript/ql/lib/semmle/javascript/Stmt.qll
+++ b/javascript/ql/lib/semmle/javascript/Stmt.qll
@@ -1,5 +1,5 @@
 /** Provides classes for working with statements. */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Templates.qll b/javascript/ql/lib/semmle/javascript/Templates.qll
index 1b3db059226b..d6eaef945894 100644
--- a/javascript/ql/lib/semmle/javascript/Templates.qll
+++ b/javascript/ql/lib/semmle/javascript/Templates.qll
@@ -1,5 +1,5 @@
 /** Provides classes for working with ECMAScript 2015-style template expressions. */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Tokens.qll b/javascript/ql/lib/semmle/javascript/Tokens.qll
index 4e1c63440b5b..cb55a8296e6d 100644
--- a/javascript/ql/lib/semmle/javascript/Tokens.qll
+++ b/javascript/ql/lib/semmle/javascript/Tokens.qll
@@ -1,7 +1,7 @@
 /**
  * Provides classes for working with the token-based representation of JavaScript programs.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/TypeAnnotations.qll b/javascript/ql/lib/semmle/javascript/TypeAnnotations.qll
index 50201363bea1..dacc3913e658 100644
--- a/javascript/ql/lib/semmle/javascript/TypeAnnotations.qll
+++ b/javascript/ql/lib/semmle/javascript/TypeAnnotations.qll
@@ -1,7 +1,7 @@
 /**
  * Provides classes for reasoning about type annotations independently of dialect.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/TypeScript.qll b/javascript/ql/lib/semmle/javascript/TypeScript.qll
index b9d6ea0af983..7772ff3e21ab 100644
--- a/javascript/ql/lib/semmle/javascript/TypeScript.qll
+++ b/javascript/ql/lib/semmle/javascript/TypeScript.qll
@@ -1,4 +1,4 @@
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/Variables.qll b/javascript/ql/lib/semmle/javascript/Variables.qll
index 5fa7473c3043..aa97233af49b 100644
--- a/javascript/ql/lib/semmle/javascript/Variables.qll
+++ b/javascript/ql/lib/semmle/javascript/Variables.qll
@@ -1,5 +1,5 @@
 /** Provides classes for modeling program variables. */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/XML.qll b/javascript/ql/lib/semmle/javascript/XML.qll
index ca401bd3f4be..e4073362fc6f 100644
--- a/javascript/ql/lib/semmle/javascript/XML.qll
+++ b/javascript/ql/lib/semmle/javascript/XML.qll
@@ -1,7 +1,7 @@
 /**
  * Provides classes and predicates for working with XML files and their content.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import semmle.files.FileSystem
diff --git a/javascript/ql/lib/semmle/javascript/YAML.qll b/javascript/ql/lib/semmle/javascript/YAML.qll
index 01473226b44a..21b0825c8617 100644
--- a/javascript/ql/lib/semmle/javascript/YAML.qll
+++ b/javascript/ql/lib/semmle/javascript/YAML.qll
@@ -4,7 +4,7 @@
  * YAML documents are represented as abstract syntax trees whose nodes
  * are either YAML values or alias nodes referring to another YAML value.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/AbstractValues.qll b/javascript/ql/lib/semmle/javascript/dataflow/AbstractValues.qll
index c5d9993dbb75..8692f1b6ff31 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/AbstractValues.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/AbstractValues.qll
@@ -37,7 +37,7 @@
  * they represent; additionally, indefinite abstract values record
  * the source of imprecision that caused them to arise.
  */
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/AdditionalFlowSteps.qll b/javascript/ql/lib/semmle/javascript/dataflow/AdditionalFlowSteps.qll
index 83d523e07094..3b59fc529520 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/AdditionalFlowSteps.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/AdditionalFlowSteps.qll
@@ -33,7 +33,7 @@ private import semmle.javascript.internal.CachedStages
  * Note: For performance reasons, all subclasses of this class should be part
  * of the standard library. Use `isAdditionalFlowStep` for query-specific flow steps.
  */
-overlay[local]
+overlay[local?]
 class AdditionalFlowStep extends Unit {
   /**
    * Holds if `pred` &rarr; `succ` should be considered a value-preserving data flow edge.f
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/Configuration.qll b/javascript/ql/lib/semmle/javascript/dataflow/Configuration.qll
index 3b4a6be84d03..ffbb9e497b04 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/Configuration.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/Configuration.qll
@@ -625,19 +625,19 @@ abstract deprecated class LabeledBarrierGuardNode extends BarrierGuardNode {
  *
  * For use with load/store steps in `DataFlow::SharedFlowStep` and TypeTracking.
  */
-overlay[local]
+overlay[local?]
 module PseudoProperties {
   /** Holds if `s` is a pseudo-property. */
   bindingset[s]
-  overlay[caller]
+  overlay[caller?]
   predicate isPseudoProperty(string s) { s.matches("$%$") }
 
   bindingset[s]
-  overlay[caller]
+  overlay[caller?]
   private string pseudoProperty(string s) { result = "$" + s + "$" }
 
   bindingset[s, v]
-  overlay[caller]
+  overlay[caller?]
   private string pseudoProperty(string s, string v) { result = "$" + s + "|" + v + "$" }
 
   /**
@@ -684,7 +684,7 @@ module PseudoProperties {
    * Gets a pseudo-property for the location of a map value where the key is `key`.
    * The string value of the `key` is encoded in the result, and there is only a result if the string value of `key` is known.
    */
-  overlay[caller]
+  overlay[caller?]
   pragma[inline]
   string mapValueKnownKey(DataFlow::Node key) {
     result = mapValueKey(any(string s | key.mayHaveStringValue(s)))
@@ -694,20 +694,20 @@ module PseudoProperties {
    * Gets a pseudo-property for the location of a map value where the key is `key`.
    */
   bindingset[key]
-  overlay[caller]
+  overlay[caller?]
   string mapValueKey(string key) { result = pseudoProperty("mapValue", key) }
 
   /**
    * Holds if `prop` equals `mapValueKey(key)` for some value of `key`.
    */
   bindingset[prop]
-  overlay[caller]
+  overlay[caller?]
   predicate isMapValueKey(string prop) { prop.matches("$mapValue|%$") }
 
   /**
    * Gets a pseudo-property for the location of a map value where the key is `key`.
    */
-  overlay[caller]
+  overlay[caller?]
   pragma[inline]
   string mapValue(DataFlow::Node key) {
     result = mapValueKnownKey(key)
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/CustomAbstractValueDefinitions.qll b/javascript/ql/lib/semmle/javascript/dataflow/CustomAbstractValueDefinitions.qll
index 3c12284d77b5..e4cc05595ec3 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/CustomAbstractValueDefinitions.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/CustomAbstractValueDefinitions.qll
@@ -7,7 +7,7 @@
  * For performance reasons, all subclasses of `CustomAbstractValueDefinition`
  * should be part of the standard library.
  */
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/DataFlow.qll b/javascript/ql/lib/semmle/javascript/dataflow/DataFlow.qll
index d7fa6ba27623..a24d7976b3d6 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/DataFlow.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/DataFlow.qll
@@ -17,7 +17,7 @@
  * Flow through global variables, object properties or function calls is not
  * modeled (except for immediately invoked functions as explained above).
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/FlowSummary.qll b/javascript/ql/lib/semmle/javascript/dataflow/FlowSummary.qll
index 13aa5628111c..c4661b321ea6 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/FlowSummary.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/FlowSummary.qll
@@ -1,5 +1,5 @@
 /** Provides classes and predicates for defining flow summaries. */
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/InferredTypes.qll b/javascript/ql/lib/semmle/javascript/dataflow/InferredTypes.qll
index 48c21d41d75d..cfce0fd20cd5 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/InferredTypes.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/InferredTypes.qll
@@ -1,4 +1,4 @@
-overlay[local]
+overlay[local?]
 module;
 
 /**
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/Nodes.qll b/javascript/ql/lib/semmle/javascript/dataflow/Nodes.qll
index aa12cfe18648..d854dfc3f628 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/Nodes.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/Nodes.qll
@@ -3,7 +3,7 @@
  * as nodes corresponding to function definitions or nodes corresponding to
  * parameters.
  */
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/Refinements.qll b/javascript/ql/lib/semmle/javascript/dataflow/Refinements.qll
index b1302df6fbc7..2fa76caed79a 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/Refinements.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/Refinements.qll
@@ -27,7 +27,7 @@
  * so the refinement can evaluate to both `true` and `false` for the same
  * candidate value.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/Sources.qll b/javascript/ql/lib/semmle/javascript/dataflow/Sources.qll
index 85a8a163cba4..55614388e7bd 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/Sources.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/Sources.qll
@@ -5,7 +5,7 @@
  * Note that unlike `TypeTracking.qll`, this library only performs
  * local tracking within a function.
  */
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/internal/AbstractValuesImpl.qll b/javascript/ql/lib/semmle/javascript/dataflow/internal/AbstractValuesImpl.qll
index 97daed1f30a6..65f0d24e48df 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/internal/AbstractValuesImpl.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/internal/AbstractValuesImpl.qll
@@ -3,7 +3,7 @@
  *
  * Provides a representation for abstract values.
  */
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/internal/AccessPaths.qll b/javascript/ql/lib/semmle/javascript/dataflow/internal/AccessPaths.qll
index b7538c7ffbf0..bd9928105178 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/internal/AccessPaths.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/internal/AccessPaths.qll
@@ -14,7 +14,7 @@
  * to the same value have the same access paths, so access paths are neither sound nor
  * complete as an approximation of expression semantics.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/internal/AdditionalFlowInternal.qll b/javascript/ql/lib/semmle/javascript/dataflow/internal/AdditionalFlowInternal.qll
index dfa924699ba5..ed07ffa73955 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/internal/AdditionalFlowInternal.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/internal/AdditionalFlowInternal.qll
@@ -5,7 +5,7 @@ private import semmle.javascript.dataflow.internal.DataFlowPrivate
 /**
  * Gets a data-flow node synthesized using `AdditionalFlowInternal#needsSynthesizedNode`.
  */
-overlay[local]
+overlay[local?]
 DataFlow::Node getSynthesizedNode(AstNode node, string tag) {
   result = TGenericSynthesizedNode(node, tag, _)
 }
@@ -13,7 +13,7 @@ DataFlow::Node getSynthesizedNode(AstNode node, string tag) {
 /**
  * An extension to `AdditionalFlowStep` with additional internal-only predicates.
  */
-overlay[local]
+overlay[local?]
 class AdditionalFlowInternal extends DataFlow::AdditionalFlowStep {
   /**
    * Holds if a data-flow node should be synthesized for the pair `(node, tag)`.
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/internal/Contents.qll b/javascript/ql/lib/semmle/javascript/dataflow/internal/Contents.qll
index d29a450274e9..787a766c897e 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/internal/Contents.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/internal/Contents.qll
@@ -1,4 +1,4 @@
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript
@@ -337,14 +337,14 @@ module Public {
     /**
      * A content set containing only the given content.
      */
-    overlay[caller]
+    overlay[caller?]
     pragma[inline]
     ContentSet singleton(Content content) { result.asSingleton() = content }
 
     /**
      * A content set corresponding to the given property name.
      */
-    overlay[caller]
+    overlay[caller?]
     pragma[inline]
     ContentSet property(PropertyName name) { result.asSingleton().asPropertyName() = name }
 
@@ -405,7 +405,7 @@ module Public {
      * If `bound` is too large, it is truncated to the greatest lower bound we can represent.
      */
     bindingset[bound]
-    overlay[caller]
+    overlay[caller?]
     ContentSet arrayElementLowerBoundFromInt(int bound) {
       result = arrayElementLowerBound(bound.minimum(getMaxPreciseArrayIndex() + 1))
     }
@@ -416,7 +416,7 @@ module Public {
      * If `n` is too large, it is truncated to the greatest lower bound we can represent.
      */
     bindingset[n]
-    overlay[caller]
+    overlay[caller?]
     ContentSet arrayElementFromInt(int n) {
       result = arrayElementKnown(n)
       or
@@ -456,7 +456,7 @@ module Public {
      * If `key` is not one of the keys we track precisely, this is mapped to the unknown key instead.
      */
     bindingset[key]
-    overlay[caller]
+    overlay[caller?]
     ContentSet mapValueFromKey(string key) {
       result = mapValueWithKnownKey(key)
       or
@@ -519,7 +519,7 @@ module Public {
      * are mapped to their corresponding content sets (which are no longer seen as property names).
      */
     bindingset[propertyName]
-    overlay[caller]
+    overlay[caller?]
     ContentSet fromLegacyProperty(string propertyName) {
       result = fromLegacyPseudoProperty(propertyName)
       or
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/internal/DataFlowNode.qll b/javascript/ql/lib/semmle/javascript/dataflow/internal/DataFlowNode.qll
index 4a354e1f7593..315c8706bc00 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/internal/DataFlowNode.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/internal/DataFlowNode.qll
@@ -3,7 +3,7 @@
  *
  * Contains the raw data type underlying `DataFlow::Node`.
  */
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/internal/DataFlowPrivate.qll b/javascript/ql/lib/semmle/javascript/dataflow/internal/DataFlowPrivate.qll
index 24549e7f1e6b..f8836e51ad91 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/internal/DataFlowPrivate.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/internal/DataFlowPrivate.qll
@@ -1,4 +1,4 @@
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript
@@ -1108,7 +1108,7 @@ DataFlowCallable viableImplInCallContext(DataFlowCall call, DataFlowCall ctx) {
 }
 
 bindingset[node, fun]
-overlay[caller]
+overlay[caller?]
 pragma[inline_late]
 private predicate sameContainerAsEnclosingContainer(Node node, Function fun) {
   node.getContainer() = fun.getEnclosingContainer()
@@ -1517,7 +1517,7 @@ private Node getPostUpdateForStore(Node base) {
 }
 
 /** Gets node to target with a store to the given `base` object.. */
-overlay[caller]
+overlay[caller?]
 pragma[inline]
 private Node getStoreTarget(DataFlow::Node base) {
   result = getPostUpdateForStore(base)
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/internal/FlowSteps.qll b/javascript/ql/lib/semmle/javascript/dataflow/internal/FlowSteps.qll
index 2d199887296b..7102e3c6a534 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/internal/FlowSteps.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/internal/FlowSteps.qll
@@ -524,7 +524,7 @@ private module CachedSteps {
   /**
    * Holds if there is a step from `pred` to `succ` through a call to an identity function.
    */
-  overlay[local]
+  overlay[local?]
   cached
   predicate identityFunctionStep(DataFlow::Node pred, DataFlow::CallNode succ) {
     exists(DataFlow::GlobalVarRefNode global |
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/internal/FlowSummaryPrivate.qll b/javascript/ql/lib/semmle/javascript/dataflow/internal/FlowSummaryPrivate.qll
index 509aa79eda8c..fe7bab98341a 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/internal/FlowSummaryPrivate.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/internal/FlowSummaryPrivate.qll
@@ -1,7 +1,7 @@
 /**
  * Provides JS specific classes and predicates for defining flow summaries.
  */
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/internal/VariableCapture.qll b/javascript/ql/lib/semmle/javascript/dataflow/internal/VariableCapture.qll
index 62892d7e5dbd..1799bc416ee5 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/internal/VariableCapture.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/internal/VariableCapture.qll
@@ -1,4 +1,4 @@
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript as js
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/internal/VariableOrThis.qll b/javascript/ql/lib/semmle/javascript/dataflow/internal/VariableOrThis.qll
index 8a3b79a420fe..96964110e11d 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/internal/VariableOrThis.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/internal/VariableOrThis.qll
@@ -1,4 +1,4 @@
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript
diff --git a/javascript/ql/lib/semmle/javascript/dataflow/internal/sharedlib/Ssa.qll b/javascript/ql/lib/semmle/javascript/dataflow/internal/sharedlib/Ssa.qll
index edea8ed6c387..7b479ac475b6 100644
--- a/javascript/ql/lib/semmle/javascript/dataflow/internal/sharedlib/Ssa.qll
+++ b/javascript/ql/lib/semmle/javascript/dataflow/internal/sharedlib/Ssa.qll
@@ -3,7 +3,7 @@
  *
  * JavaScript's old SSA library is still responsible for the ordinary SSA flow.
  */
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript as js
diff --git a/javascript/ql/lib/semmle/javascript/frameworks/AngularJS/AngularJSCore.qll b/javascript/ql/lib/semmle/javascript/frameworks/AngularJS/AngularJSCore.qll
index beb601dcfb9e..944256bd4569 100644
--- a/javascript/ql/lib/semmle/javascript/frameworks/AngularJS/AngularJSCore.qll
+++ b/javascript/ql/lib/semmle/javascript/frameworks/AngularJS/AngularJSCore.qll
@@ -15,7 +15,7 @@ private import AngularJS
 /**
  * Holds if `nd` is a reference to the `angular` variable.
  */
-overlay[local]
+overlay[local?]
 DataFlow::SourceNode angular() {
   // either as a global
   result = DataFlow::globalVarRef("angular")
diff --git a/javascript/ql/lib/semmle/javascript/frameworks/LazyCache.qll b/javascript/ql/lib/semmle/javascript/frameworks/LazyCache.qll
index e8b389e91ad5..e239c79b852f 100644
--- a/javascript/ql/lib/semmle/javascript/frameworks/LazyCache.qll
+++ b/javascript/ql/lib/semmle/javascript/frameworks/LazyCache.qll
@@ -1,7 +1,7 @@
 /**
  * Models imports through the NPM `lazy-cache` package.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/frameworks/LodashUnderscore.qll b/javascript/ql/lib/semmle/javascript/frameworks/LodashUnderscore.qll
index fe07e4f19678..74808368c718 100644
--- a/javascript/ql/lib/semmle/javascript/frameworks/LodashUnderscore.qll
+++ b/javascript/ql/lib/semmle/javascript/frameworks/LodashUnderscore.qll
@@ -9,7 +9,7 @@ module LodashUnderscore {
   /**
    * A data flow node that accesses a given member of `lodash` or `underscore`.
    */
-  overlay[local]
+  overlay[local?]
   abstract class Member extends DataFlow::SourceNode {
     /** Gets the name of the accessed member. */
     abstract string getName();
@@ -18,7 +18,7 @@ module LodashUnderscore {
   /**
    * An import of `lodash` or `underscore` accessing a given member of that package.
    */
-  overlay[local]
+  overlay[local?]
   private class DefaultMember extends Member {
     string name;
 
@@ -41,14 +41,14 @@ module LodashUnderscore {
    * In addition to normal imports, this supports per-method imports such as `require("lodash.map")` and `require("lodash/map")`.
    * In addition, the global variable `_` is assumed to refer to `lodash` or `underscore`.
    */
-  overlay[local]
+  overlay[local?]
   DataFlow::SourceNode member(string name) { result.(Member).getName() = name }
 
   /**
    * Holds if `name` is the name of a member exported from the `lodash` package
    * which has a corresponding `lodash.xxx` NPM package.
    */
-  overlay[local]
+  overlay[local?]
   private predicate isLodashMember(string name) {
     // Can be generated using Object.keys(require('lodash'))
     name =
@@ -185,7 +185,7 @@ module LodashUnderscore {
     }
   }
 
-  overlay[local]
+  overlay[local?]
   private class LodashEach extends DataFlow::SummarizedCallable {
     LodashEach() { this = "_.each-like" }
 
@@ -201,7 +201,7 @@ module LodashUnderscore {
     }
   }
 
-  overlay[local]
+  overlay[local?]
   private class LodashMap extends DataFlow::SummarizedCallable {
     LodashMap() { this = "_.map" }
 
@@ -220,7 +220,7 @@ module LodashUnderscore {
     }
   }
 
-  overlay[local]
+  overlay[local?]
   private class LodashFlatMap extends DataFlow::SummarizedCallable {
     LodashFlatMap() { this = "_.flatMap" }
 
@@ -242,7 +242,7 @@ module LodashUnderscore {
     }
   }
 
-  overlay[local]
+  overlay[local?]
   private class LodashFlatMapDeep extends DataFlow::SummarizedCallable {
     LodashFlatMapDeep() { this = "_.flatMapDeep" }
 
@@ -266,7 +266,7 @@ module LodashUnderscore {
     }
   }
 
-  overlay[local]
+  overlay[local?]
   private class LodashReduce extends DataFlow::SummarizedCallable {
     LodashReduce() { this = "_.reduce-like" }
 
@@ -285,7 +285,7 @@ module LodashUnderscore {
     }
   }
 
-  overlay[local]
+  overlay[local?]
   private class LoashSortBy extends DataFlow::SummarizedCallable {
     LoashSortBy() { this = "_.sortBy-like" }
 
@@ -303,7 +303,7 @@ module LodashUnderscore {
     }
   }
 
-  overlay[local]
+  overlay[local?]
   private class LodashMinMaxBy extends DataFlow::SummarizedCallable {
     LodashMinMaxBy() { this = "_.minBy / _.maxBy" }
 
@@ -317,7 +317,7 @@ module LodashUnderscore {
     }
   }
 
-  overlay[local]
+  overlay[local?]
   private class LodashPartition extends DataFlow::SummarizedCallable {
     LodashPartition() { this = "_.partition" }
 
@@ -331,7 +331,7 @@ module LodashUnderscore {
     }
   }
 
-  overlay[local]
+  overlay[local?]
   private class UnderscoreMapObject extends DataFlow::SummarizedCallable {
     UnderscoreMapObject() { this = "_.mapObject" }
 
@@ -352,7 +352,7 @@ module LodashUnderscore {
     }
   }
 
-  overlay[local]
+  overlay[local?]
   private class LodashTap extends DataFlow::SummarizedCallable {
     LodashTap() { this = "_.tap" }
 
diff --git a/javascript/ql/lib/semmle/javascript/frameworks/NodeJSLib.qll b/javascript/ql/lib/semmle/javascript/frameworks/NodeJSLib.qll
index 89d436bb64c7..b6506ddd648d 100644
--- a/javascript/ql/lib/semmle/javascript/frameworks/NodeJSLib.qll
+++ b/javascript/ql/lib/semmle/javascript/frameworks/NodeJSLib.qll
@@ -8,17 +8,17 @@ import semmle.javascript.security.SensitiveActions
 private import semmle.javascript.dataflow.internal.PreCallGraphStep
 
 module NodeJSLib {
-  overlay[local]
+  overlay[local?]
   private GlobalVariable processVariable() { variables(result, "process", any(GlobalScope sc)) }
 
-  overlay[local]
+  overlay[local?]
   pragma[nomagic]
   private GlobalVarAccess processExprInTopLevel(TopLevel tl) {
     result = processVariable().getAnAccess() and
     tl = result.getTopLevel()
   }
 
-  overlay[local]
+  overlay[local?]
   pragma[nomagic]
   private GlobalVarAccess processExprInNodeModule() {
     result = processExprInTopLevel(any(NodeModule m))
@@ -28,7 +28,7 @@ module NodeJSLib {
    * An access to the global `process` variable in a Node.js module, interpreted as
    * an import of the `process` module.
    */
-  overlay[local]
+  overlay[local?]
   private class ImplicitProcessImport extends DataFlow::ModuleImportNode::Range {
     ImplicitProcessImport() { this = DataFlow::exprNode(processExprInNodeModule()) }
 
diff --git a/javascript/ql/lib/semmle/javascript/frameworks/PropertyProjection.qll b/javascript/ql/lib/semmle/javascript/frameworks/PropertyProjection.qll
index c0188361e72a..957121da5af1 100644
--- a/javascript/ql/lib/semmle/javascript/frameworks/PropertyProjection.qll
+++ b/javascript/ql/lib/semmle/javascript/frameworks/PropertyProjection.qll
@@ -4,7 +4,7 @@
  * Subclass `PropertyProjection` to refine the behavior of the analysis on existing property projections.
  * Subclass `CustomPropertyProjection` to introduce new kinds of property projections.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/frameworks/Templating.qll b/javascript/ql/lib/semmle/javascript/frameworks/Templating.qll
index f1f91785329c..d63bafe7b6f3 100644
--- a/javascript/ql/lib/semmle/javascript/frameworks/Templating.qll
+++ b/javascript/ql/lib/semmle/javascript/frameworks/Templating.qll
@@ -1,7 +1,7 @@
 /**
  * Provides predicates for working with templating libraries.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
diff --git a/javascript/ql/lib/semmle/javascript/frameworks/UriLibraries.qll b/javascript/ql/lib/semmle/javascript/frameworks/UriLibraries.qll
index 9097497b4f07..03887819b252 100644
--- a/javascript/ql/lib/semmle/javascript/frameworks/UriLibraries.qll
+++ b/javascript/ql/lib/semmle/javascript/frameworks/UriLibraries.qll
@@ -422,7 +422,7 @@ private module ClosureLibraryUri {
   }
 }
 
-overlay[local]
+overlay[local?]
 private class QueryStringStringification extends DataFlow::SummarizedCallable {
   QueryStringStringification() { this = "query-string stringification" }
 
diff --git a/javascript/ql/lib/semmle/javascript/frameworks/data/ModelsAsData.qll b/javascript/ql/lib/semmle/javascript/frameworks/data/ModelsAsData.qll
index 9e7f94c139b7..5d65f901d22d 100644
--- a/javascript/ql/lib/semmle/javascript/frameworks/data/ModelsAsData.qll
+++ b/javascript/ql/lib/semmle/javascript/frameworks/data/ModelsAsData.qll
@@ -48,7 +48,7 @@ private class ThreatModelSourceFromDataExtension extends ThreatModelSource::Rang
   }
 }
 
-overlay[local]
+overlay[local?]
 private class SummarizedCallableFromModel extends DataFlow::SummarizedCallable {
   string type;
   string path;
diff --git a/javascript/ql/lib/semmle/javascript/frameworks/data/internal/ApiGraphModelsSpecific.qll b/javascript/ql/lib/semmle/javascript/frameworks/data/internal/ApiGraphModelsSpecific.qll
index 2074b18600dc..3fb76f76f70a 100644
--- a/javascript/ql/lib/semmle/javascript/frameworks/data/internal/ApiGraphModelsSpecific.qll
+++ b/javascript/ql/lib/semmle/javascript/frameworks/data/internal/ApiGraphModelsSpecific.qll
@@ -41,7 +41,7 @@ class Location = JS::Location;
  * The model generator must explicitly generate the step between `(package)` and `(package).foo`, for example.
  */
 bindingset[rawType]
-overlay[caller]
+overlay[caller?]
 predicate parseTypeString(string rawType, string package, string qualifiedName) {
   exists(string regexp |
     regexp = "('[^']+'|[^.]+)(.*)" and
@@ -56,7 +56,7 @@ predicate parseTypeString(string rawType, string package, string qualifiedName)
 /**
  * Holds if models describing `package` may be relevant for the analysis of this database.
  */
-overlay[local]
+overlay[local?]
 predicate isPackageUsed(string package) {
   package = "global"
   or
@@ -70,7 +70,7 @@ predicate isPackageUsed(string package) {
 }
 
 bindingset[type]
-overlay[local]
+overlay[local?]
 predicate isTypeUsed(string type) {
   exists(string package |
     parseTypeString(type, package, _) and
@@ -82,10 +82,10 @@ predicate isTypeUsed(string type) {
  * Holds if `type` can be obtained from an instance of `otherType` due to
  * language semantics modeled by `getExtraNodeFromType`.
  */
-overlay[local]
+overlay[local?]
 predicate hasImplicitTypeModel(string type, string otherType) { none() }
 
-overlay[local]
+overlay[local?]
 pragma[nomagic]
 private predicate parseRelevantTypeString(string rawType, string package, string qualifiedName) {
   isRelevantFullPath(rawType, _) and
diff --git a/javascript/ql/lib/semmle/javascript/internal/BasicBlockInternal.qll b/javascript/ql/lib/semmle/javascript/internal/BasicBlockInternal.qll
index d422c960a8fc..e0324bf5a6bf 100644
--- a/javascript/ql/lib/semmle/javascript/internal/BasicBlockInternal.qll
+++ b/javascript/ql/lib/semmle/javascript/internal/BasicBlockInternal.qll
@@ -2,7 +2,7 @@
  * Provides classes for working with basic blocks, and predicates for computing
  * liveness information for local variables.
  */
-overlay[local]
+overlay[local?]
 module;
 
 import javascript
@@ -320,7 +320,7 @@ module Public {
     /**
      * Holds if this basic block strictly dominates `bb`.
      */
-    overlay[caller]
+    overlay[caller?]
     pragma[inline]
     predicate strictlyDominates(ReachableBasicBlock bb) { this = immediateDominator+(bb) }
 
@@ -329,14 +329,14 @@ module Public {
      *
      * This predicate is reflexive: each reachable basic block dominates itself.
      */
-    overlay[caller]
+    overlay[caller?]
     pragma[inline]
     predicate dominates(ReachableBasicBlock bb) { this = immediateDominator*(bb) }
 
     /**
      * Holds if this basic block strictly post-dominates `bb`.
      */
-    overlay[caller]
+    overlay[caller?]
     pragma[inline]
     predicate strictlyPostDominates(ReachableBasicBlock bb) { this = immediatePostDominator+(bb) }
 
@@ -345,7 +345,7 @@ module Public {
      *
      * This predicate is reflexive: each reachable basic block post-dominates itself.
      */
-    overlay[caller]
+    overlay[caller?]
     pragma[inline]
     predicate postDominates(ReachableBasicBlock bb) { this = immediatePostDominator*(bb) }
   }
diff --git a/javascript/ql/lib/semmle/javascript/internal/CachedStages.qll b/javascript/ql/lib/semmle/javascript/internal/CachedStages.qll
index 17aa82ced6cf..eab6b76b031e 100644
--- a/javascript/ql/lib/semmle/javascript/internal/CachedStages.qll
+++ b/javascript/ql/lib/semmle/javascript/internal/CachedStages.qll
@@ -40,7 +40,7 @@ module Stages {
   /**
    * The `ast` stage.
    */
-  overlay[local]
+  overlay[local?]
   cached
   module Ast {
     /**
@@ -85,7 +85,7 @@ module Stages {
   /**
    * The `basicblocks` stage.
    */
-  overlay[local]
+  overlay[local?]
   cached
   module BasicBlocks {
     /**
@@ -112,7 +112,7 @@ module Stages {
   /**
    * The part of data flow computed before flow summary nodes.
    */
-  overlay[local]
+  overlay[local?]
   cached
   module EarlyDataFlowStage {
     /**
@@ -137,7 +137,7 @@ module Stages {
   /**
    * The `dataflow` stage.
    */
-  overlay[local]
+  overlay[local?]
   cached
   module DataFlowStage {
     /**
diff --git a/javascript/ql/lib/semmle/javascript/internal/Overlay.qll b/javascript/ql/lib/semmle/javascript/internal/Overlay.qll
index d1ca1f2b0da4..db3dc8ac6bf6 100644
--- a/javascript/ql/lib/semmle/javascript/internal/Overlay.qll
+++ b/javascript/ql/lib/semmle/javascript/internal/Overlay.qll
@@ -2,10 +2,10 @@ private import javascript
 private import OverlayXml
 
 /** Holds if the database is an overlay. */
-overlay[local]
+overlay[local?]
 private predicate isOverlay() { databaseMetadata("isOverlay", "true") }
 
-overlay[local]
+overlay[local?]
 private string getFileFromEntity(@locatable node) {
   exists(@location loc |
     hasLocation(node, loc)
@@ -19,11 +19,11 @@ private string getFileFromEntity(@locatable node) {
 }
 
 /** Holds if `file` was changed or deleted in the overlay. */
-overlay[local]
+overlay[local?]
 private predicate discardFile(string file) { isOverlay() and overlayChangedFiles(file) }
 
 /** Holds if `node` is in the `file` and is part of the overlay base database. */
-overlay[local]
+overlay[local?]
 private predicate discardableEntity(string file, @locatable node) {
   not isOverlay() and file = getFileFromEntity(node)
 }
@@ -34,7 +34,7 @@ private predicate discardEntity(@locatable node) {
   exists(string file | discardableEntity(file, node) and discardFile(file))
 }
 
-overlay[local]
+overlay[local?]
 private string getFileFromLocation(@location loc) {
   exists(@file file |
     locations_default(loc, file, _, _, _, _) and
@@ -43,7 +43,7 @@ private string getFileFromLocation(@location loc) {
 }
 
 /** Holds if `loc` is in the `file` and is part of the overlay base database. */
-overlay[local]
+overlay[local?]
 private predicate discardableLocation(string file, @location node) {
   not isOverlay() and file = getFileFromLocation(node)
 }
diff --git a/javascript/ql/lib/semmle/javascript/internal/StmtContainers.qll b/javascript/ql/lib/semmle/javascript/internal/StmtContainers.qll
index 741575c3242c..65984e2eb9b5 100644
--- a/javascript/ql/lib/semmle/javascript/internal/StmtContainers.qll
+++ b/javascript/ql/lib/semmle/javascript/internal/StmtContainers.qll
@@ -4,7 +4,7 @@
  * Provides predicates and classes for relating nodes to their
  * enclosing `StmtContainer`.
  */
-overlay[local]
+overlay[local?]
 module;
 
 private import javascript
@@ -48,7 +48,7 @@ class NodeInStmtContainer extends Locatable, @node_in_stmt_container {
   /**
    * Gets the function or toplevel to which this node belongs.
    */
-  overlay[caller]
+  overlay[caller?]
   pragma[inline]
   final StmtContainer getContainer() { result = getStmtContainer(this) }
 }
diff --git a/javascript/ql/lib/utils/test/InlineSummaries.qll b/javascript/ql/lib/utils/test/InlineSummaries.qll
index 0366736eaf66..1633e056b7f1 100644
--- a/javascript/ql/lib/utils/test/InlineSummaries.qll
+++ b/javascript/ql/lib/utils/test/InlineSummaries.qll
@@ -1,7 +1,7 @@
 import javascript
 import semmle.javascript.dataflow.FlowSummary
 
-overlay[local]
+overlay[local?]
 class MkSummary extends SummarizedCallable {
   private CallExpr mkSummary;